A full cell consists of the cobalt sulfide@reduced graphene oxide nanocomposite anode and a commercial LiCoO2 cathode, and is able to hold a high capacity of 574.7 mA h g−1 at 200 mA g−1 after 200 cycles. The reduced graphene oxide plays a key role in enhancing the electrical conductivity of the electrode materials; and it effectively prevents the cobalt sulfide nanoparticles from dropping off the electrode and buffers the volume variation during the discharge–charge process. The cobalt sulfide@reduced graphene oxide nanocomposites present great potential to be a promising anode material for lithium-ion batteries.Cobalt sulfide@reduced graphene oxide composites were prepared through a simple solvothermal method. The cobalt sulfide@reduced graphene oxide composites are composed of cobalt sulfide nanoparticles uniformly attached on both sides of reduced graphene oxide. Some favorable electrochemical performances in specific capacity, cycling performance, and rate capability are achieved using the porous nanocomposites as an anode for lithium-ion batteries. In a half-cell, it exhibits a high specific capacity of 1253.9 mA h g Cobalt sulfide@reduced graphene oxide nanocomposites obtained through a dipping and hydrothermal process, exhibit ascendant lithium-ion storage properties. The present commercial anode, graphite with a low theoretical capacity of 372 mA h g−1, greatly hinders the application fields of LIBs.4–6 Thus, the search for an anode with a high capacity, high rate capability and good cycling stability becomes urgent for the extensive applications of LIBs.Nowadays, lithium-ion batteries (LIBs), as convenient and effective devices for the storage and conversion of energy, have extended their practical application in alternative energy sources, and hybrid electric vehicles, as well as other electrical equipment.x) such as FeSx,7 NiSx,8,9 MnSx,10 MoS2,11,12 SnS2,13 CuS,14,15 ZnS16 have been fabricated and served as anode materials for LIBs due to their high theoretical capacities, low cost and abundant raw materials. Cobalt sulfide (CoSx) has been considered as an alternative anode material because of its high theoretical specific capacity of 590 mA h g−1 and superior electrochemical performance.17 Unfortunately, the pure CoS anode suffers from the low rate capability and a poor cycling stability, which were caused by the low electric conductivity, huge-structural change, and easy pulverization of the CoS anode material.17–20 Therefore, the tremendous efforts have been paid to improving the conductivity of anode materials and the diffusion of lithium ions/electrons.Recently, various transition metal sulfides  anchored on reduced graphene oxide (rGO) via combination of hydrothermal with sulfidation process. The as prepared CoS NFs–rGO electrodes delivered the discharge a capacity of 939 mA h g−1 after the 100th cycle at 100 mA g−1 with coulombic efficiency above 98%.30 Zhu et al. prepared CoSx/rGO nanocomposite via a facile hydrothermal method with CoSx NPs uniformly embedded in rGO. When utilized in LIBs, the composite demonstrated a high discharge capacity of 796 mA h g−1 after 50 cycles at 100 mA g−1.31 Lu et al. reported Cox1−S hollow spheres formed by in situ growth on reduced graphene oxide layers. When evaluated as an anode material for LIBs, it delivers a specific capacity of 969.8 mA h g−1 with a high coulombic efficiency of 96.49% after 90 cycles at 50 mA g−1.32 Compared with the pure CoS anodes, improvements in the specific capacity, cycling life and rate performance were achieved. Nevertheless, most graphene-based nanocomposites were obtained through a simple hydrothermal method, mixing the reactant with graphene oxide in a Teflon-lined autoclave. The resulting active materials obtained by this method cannot fully anchor on the surface of the rGO and often fall off easily, leading to a poor electrochemical property.25,27,32,33 Furthermore, the loading amount of CoS on rGO would also greatly affect the Li-storage performances of the nanocomposites. To seek for the desirable electrochemical behaviors for LIBs, it is important to develop a CoS@rGO nanocomposite with various CoS loadings, in which all CoS could anchor on the surface of rGO densely and tightly.To address the above problems, many attentions have been paid to the design of the CoS-based composites with nanostructures. The nanostructured CoS composites with an improved structural stability and electronic conductivity could be fabricated by incorporation of the CoS nanoparticles (NPs) with various carbonaceous materials such as amorphous carbon,via an electrostatic reaction to form CoS NPs uniformly distributing on the surfaces of the rGO. Employed as an anode, the CoS@rGO nanocomposites show outstanding electrochemical behaviors for LIBs.In this study, CoS@rGO nanocomposites with a 3D nanostructure were synthesized through a simple hydrothermal method. The composites consist of numerous CoS NPs and the rGO. The functional groups on the surfaces of rGO capture the Co ions All chemical reagents in this study were at the analytical level. The preparation of graphene oxide and 3D rGO is described in the ESI.†3CSNH2 and various amount of CoCl2·6H2O  were dissolved in 14 mL of DMF/water mixture solvent (1 : 1 v/v). The mixed precursor solution was stirred to form a transparent solution at room temperature using a magnetic stirrer. Then, a columnar rGO was soaked in the solution for 2 days. After that, the solution system was transferred into a Teflon-lined stainless steel autoclave and maintained at 200 °C for 24 h. When it cooled down to room temperature, the product was taken out and rinsed for several times with deionized water and absolute ethanol, respectively. At last, the product was vacuum-dried at 60 °C for 10 h. The amounts of CoCl2·6H2O for the preparation of CoS@rGO-1, CoS@rGO-2 and CoS@rGO-3 were 0.4, 0.5 and 0.6 g, respectively.Synthesis of CoS@rGO 0.8 g of CHThe as-prepared samples were characterized using X-ray diffraction , transmission electron microscopy , field emission scanning electron microscopy  with energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) (ESCALAB 250), Brunauer–Emmett–Teller (BET) nitrogen adsorption–desorption (Nova 2000E), and Raman spectroscopy . A thermogravimetric analysis (Setaram Labsys Evo SDT Q600) was conducted to determine the rGO content of the composites.6 mixed with ethylene carbonate (EC) and diethyl carbonate (DEC), with a volume ratio of 1 : 1. The mass loading of the electrode and the active mass are ca. 1.08 and 0.76 mg, respectively. The assembly process of the cells was carried out in a glove box ) filled with Ar gas, with oxygen and water concentrations below 0.1 ppm and 1 ppm, respectively. For a full-cell, a commercial LiCoO2 was used as the counter/reference electrode using a polypropylene separator (Celgard 2400). The commercial LiCoO2 mixed with a binder polyvinylidene fluoride (PVDF) and carbon black (mass ratio of 8 : 1 : 1) in N-methyl-2-pyrrolidone (NMP) solvent to form a slurry. The uniform slurry was then cast onto the surface of an aluminum foil and dried at 80 °C for 12 h. The mass loading of the electrode and the active mass are ca. 10.01 and 8.01 mg, respectively. The ratio of cathode and anode active materials is ca. 10.54. For a half-cell, a Neware battery tester  with a voltage ranging from 0.01–3.0 V was used to monitor the discharge/charge behavior. For the full-cell, the voltage range was 1.5–3.9 V. An electrochemical workstation  was used to record the cyclic voltammetry (CV) performance at a scanning rate of 0.1 mV s−1. The data of the electrochemical impedance spectrum (EIS) was obtained from 0.01 Hz to 100 kHz.For a half-cell, the electrochemical tests of the as-prepared CoS@rGO nanocomposites were conducted in a CR2032 coin-kind cell using a polypropylene separator (Celgard 2400), and the lithium plate acted as a counter/reference electrode. The active materials mixed with a sodium carboxymethyl cellulose binder, styrene butadiene rubber, and carbon black (mass ratio of 7 : 1.5 : 0.5 : 1) in water to form a slurry. The uniform slurry was then cast onto the surface of a copper foil and dried at 80 °C for 12 h. The electrolyte consisted of 1 M LiPF34,35 No other obvious diffraction peaks are found in The crystal structure of the CoS@rGO samples were determined by XRD as shown in The FE-SEM images of the samples  are presented in More detailed information on the morphology and structure of CoS@rGO-1 could be obtained using TEM and high-resolution TEM (HRTEM). The TEM images of the CoS@rGO-1 composite are presented in ca. 1347 and 1588 cm−1, which can be respectively ascribed to the D and G bands of rGO. Furthermore, 2D and D + G peaks not shown here should locate at approximately 2694 and 2935 cm−1, respectively.36 The formation of the D and G bands results from the disorder and defects in the graphene layers, and sp2-bonded carbon atoms in the hexagonal lattice, respectively. For carbon-related materials, the intensity ratio (ID/IG) of the D and G bands represents the defects and degree of graphitization.37ID/IG of the CoS@rGO-1, CoS@rGO-2, CoS@rGO-3, and GO are 1.12, 1.16, 1.22, and 0.917, respectively. This clearly indicates that most of the oxygen-containing functional groups on graphene oxide have been reduced in the CoS@rGO composites.36 Furthermore, the increase of the intensity ratio (ID/IG) may also be due to due to the widely separated rGO layers promoted by the intercalation of CoS NPs.38Raman spectroscopy was applied to investigate the structure of carbon materials in details. And Raman spectra of the CoS@rGO and GO samples are displayed in 2+.39 The peaks at 778.5 and 793.7 eV are the Co 2p3/2 and 2p1/2 of cobalt sulfides.40 The binding energy at 780.6 and 796.3 eV are consistent with Co 2p3/2 and 2p1/2 with the splitting value over 15 eV demonstrating the coexistence of Co3+ and Co2+.41,42 The higher state of Co3+ would provide extra capacity for LIBs.43 The S 2p spectrum as shown in 32,44–47 In addition,  PBM data was replaced with SVG by xgml2pxml:<glyph-data id="z.dbd" format="PBM" resolution="300" x-size="8" y-size="10" xml:space="preserve">00000000000000000000000000000000111111110000000011111111000000000000000000000000</glyph-data><svg xmlns="http://www.w3.org/2000/svg" version="1.0" width="13.200000pt" height="16.000000pt" viewBox="0 0 13.200000 16.000000" preserveAspectRatio="xMidYMid meet"><metadata>Created by potrace 1.16, written by Peter Selinger 2001-2019</metadata><g transform="translate scale" fill="currentColor" stroke="none"><path d="M0 440 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z M0 280 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z"/></g></svg>C bonds. Also, two weak peaks at 288.5 eV and 286.3 eV are detected, coming from the O–CO and C–O/C–S bonds, respectively.48 Obviously, the intensity of the C–C/CC bonds are much stronger than that of O–CO and C–O/C–S bonds. This result proves that the overwhelming majority of GO were reduced and transformed into the rGO via the hydrothermal process. The presence of C–S bond further confirms the formation of tight bonding between the C atoms and S atoms, which demonstrates that the CoS particles tightly attached on the surface of the rGO.25XPS analysis was used to determine the valence state and elemental composition in the CoS@rGO nanocomposites. From the survey spectrum shown in 49 The third weight loss from 410 to 650 °C is mainly due to the decomposition by oxidation of CoS into Co3O4.50 As we know that the TGA data cannot be so clearly separated to rGO and CoS formation. The carbon contents within the CoS@rGO-1, CoS@rGO-2 and CoS@rGO-3 samples are approximately 4.5 ± 0.3 wt%, 3.6 ± 0.2 wt% and 3.1 ± 0.2 wt%, respectively.The content of rGO in the CoS@rGO nanocomposite was calculated based on the TGA results, which were performed at the temperature range of room temperature to 650 °C in air, as shown in Fig. S4 (see ESI for detail).2 g−1 for the CoS@rGO-1, CoS@rGO-2 and CoS@rGO-3 samples, respectively, in terms of a Brunauer–Emmett–Teller (BET) model. Obviously, the specific surface area of the samples slightly decreases as the load of the CoS NPs increases. The insets of the figures show the distributions of the pore sizes ranging from 1 to 22 nm. The pore sizes for the CoS@rGO-1, CoS@rGO-2 and CoS@rGO-3 respectively average 2.4, 2.1 and 1.9 nm. The as prepared CoS@rGO nanocomposites with high specific surface area and sandwich structure would present some exceptional performances in the application of LIBs.For the investigation of the porosity texture of the CoS@rGO nanocomposites, the nitrogen adsorption–desorption isotherms and pore size distributions (inset) were performed in Fig. S5.xLi+ + xe− → LixCoS.19,33,51 Another slight peak at ∼1.20 V corresponds to the reduction reaction: (2 − x)Li+ + LixCoS + (2 − x)e− → Co + Li2S.19,33,51 In the next two cycles, two peaks positively shift to ∼1.70 V and ∼1.29 V, respectively. The weak broad peak at ca. 0.41 V is assigned to the formation of the solid electrolyte interface (SEI) film which disappear in the following two cycles. The prominent peak at ∼0.11 V is attributed to the insertion of lithium into the rGO nanosheets and the lattice of carbon: yC + xLi+ + xe− → LixCy.52,53 In the anodic process, two apparent peaks at ∼2.08 and ∼2.40 V can be identified as the reverse reaction to form LixCoS and CoS, respectively. The CV curves are overlapped well in the second and third cycles indicating the good electrochemical reversibility of the electrode.The electrochemical properties of the electrodes were studied using cyclic voltammograms (CV) tests. 33 The obvious plateau at ∼0.12 V is ascribed to the lithium ion insertion of carbon.) In the charge process, two plateaus at ∼2.0 and ∼2.4 V are consistent with the anodic peaks in CV curves. In the first discharge and charge curves, the CoS@rGO-2 composite delivers specific capacities of 2262.0 and 1521.9 mA h g−1, respectively. And the coulombic efficiency is calculated as 67.3%, which mainly due to the SEI layer formed on the surface of the electrode. Besides, in the first lithiation process, some lithium ions were consumed because of the defects in the nanocomposite.54 In the second and third cycles, the specific discharge capacities of the CoS@rGO-2 composites declined to 1613.4 and 1589.2 mA h g−1, respectively. The coulombic efficiency of the second cycle increased to 97.8%, and it maintained ca. 97.9% in the third cycle, proving the good electrochemical cycling reversibility.The discharge and charge profiles the CoS@rGO-2 nanocomposites are shown in −1 at the current densities of 0.1, 0.2, 0.5, and 1.0 A g−1, respectively. The CoS@rGO-2 electrode delivered a high capacity of 668.5 mA h g−1 even at 2.0 A g−1. For the CoS@rGO-1, CoS@rGO-2 and CoS@rGO-3 electrodes, the specific capacities could respectively reach to 1305.8, 1462.6 and 1335.1 mA h g−1, when the current density returns to 0.1 A g−1. Furthermore, the CoS@rGO nanocomposite electrodes present a much better rate capacity than those of cobalt sulfide-based composites such as CoS NFs–rGO,30 CoSx/rGO nanocomposite31 and Cox1−S hollow spheres/rGO.32The rate performance of the CoS@rGO-1, CoS@rGO-2, CoS@rGO-3 were presented in −1. Observed from −1 with the coulombic efficiency of 99.2%, 98.9% and 99.9%, respectively. The theoretical capacity of CoS@rGO-2 can be calculated to be ∼596.6 mA h g−1 (CoS contribution (capacityCoS = 590 × 96.4%) + rGO contribution (capacityrGO = 774 × 3.6%)). The capacity of the CoS@rGO-2 electrode is much higher than the theoretical value, which may be attributed to an excellent synergistic effect between CoS NPs and rGO.48 In comparison with the CoS-based electrodes recent reported, the CoS@rGO nanocomposite electrodes exhibit superior electrochemical performance than those of CoS NPs,18 lantern-like CoS,55 CoS/CNTs hybrid,22 CoS nanosheets/rGO foams,25 cobalt sulfides/rGO composite,27,28 CoS NFs–rGO,30 CoSx/rGO nanocomposite,31 Cox1−S hollow spheres/rGO,32 CoS2/rGO composites,38 and other CoS/rGO composites,33,56,57 which have been listed in Table S1 (ESI).−1) among three nanocomposite electrodes after 100 cycles. And the suitable loading of active materials (CoS NPs) in the nanocomposites could account for the highest discharge capacity of the CoS@rGO-2 electrode. Since the theory capacity of CoS is higher than that of the rGO, the capacity of the CoS@rGO increases with the increase of the amount of the CoS within the composites. As a result, the specific capacity of the CoS@rGO-2 is higher than that of CoS@rGO-1. However, when there are too many CoS NPs anchored on the rGO, they could easily detached from rGO during the charge–discharge process, resulting a poor capacity.58 The detachment of the CoS NPs from the rGO can be observed from the SEM and TEM images (Fig. S7−1. Therefore, the specific capacity of the CoS@rGO-3 is lower than that of CoS@rGO-2.The cycling performance of the CoS@rGO composites was investigated when a high current density was set as 0.5 A gs Fig. S7 of the CRs. The resistance and constant phase element for the SEI film can be respectively expressed by Rf and CPE1. And for electrode/electrolyte interface, the charge-transfer resistance and constant phase element can be represented by Rct and CPE2, respectively. In addition, the Warburg impedance produced in the process of the lithium-diffusion can be referred as Wo.59 The Rct of the CoS@rGO-1, CoS@rGO-2 and CoS@rGO-3 electrodes before cycling test are 80.7, 56.6 and 61.3 Ω, respectively, which can be revealed by the fitting results. After 100 cycles, Rct of these electrodes respectively decreases to 53.0, 20.1 and 40.5 Ω. This may be due to the obvious pulverization of CoS NPs on the surface of rGO during the cycling process. The pulverization of CoS NPs can be observed from the TEM image (−1. Among these CoS@rGO nanocomposite electrodes before cycling test and after 100 cycles, the Rct of CoS@rGO-2 electrode is the smallest, for CoS NPs anchored on the rGO in the composites contribute to the small Rct value. Moreover, the Rct of the CoS@rGO-3 electrode is higher than that of the CoS@rGO-2 electrode, which may be due to the slight detachment of active material CoS from the surface of rGO. The slight detachment of the CoS NPs marked with an arrow can be observed from the SEM image (−1. The straight line in the low-frequency region is associated with Warburg behaviour where the lithium-ion diffusion occurs in the nanostructure. This clearly indicates that the unique porous structure is quite advantageous for improving the speed of charge transfer at the interface, and reducing the overall resistance of the battery, thus leading to excellent electrochemical performances.The Nyquist plots of the CoS@rGO nanocomposite electrodes before cycling test and after 100 cycles were presented in EM image  of the CEM image  of the C−1 for 10 or 100 cycles. Fig. S83S4, cubic Co9S8, orthorhombic CoSO4, and rhombohedral carbon in the final electrode material. This is consistent with the result of the EDS analysis after cycling. Moreover, Fig. S6−1. This clearly shows the presence of Co, S and C in the composites after 100 cycles. A small part of S has been oxidized to some higher valence states, and after the cycles, the composite consists of S2−, S22−, SO32−, and SO42−.The morphology and composition of the CoS@rGO nanocomposites were investigated by SEM, TEM, EDS, and XRD after the composite electrode was tested at 0.5 A g2 and the CoS@rGO-2 nanocomposites which respectively serve as a cathode and an anode. The capacity of the LiCoO2 was 1.2 times than that of the anode in design. When a current density and potential range was respectively set as 0.2 A g−1 and 1.5–3.9 V, the charge/discharge profiles were presented in −1, and the coulombic efficiency is ∼50.2%. The formation of SEI layer on the surfaces of the electrodes may account for the major loss in capacity. In the second and third cycles, the coulombic efficiency was up to 97.1% and 97.5%, respectively. This suggests that there is efficient electron transport as well as smooth insertion and extraction of Li+. Moreover, the cycling performance of the full battery was exhibited in −1 at 0.2 A g−1 when the battery cycled 200 times, which indicates outstanding cycling stability for the full battery.A full cell consists of commercial LiCoO−1 at 500 mA g−1 after 100 cycles. For a full-cell, the CoS@rGO-2 nanocomposite anode exhibited a capacity of 574.7 mA h g−1 at 200 mA g−1 after 200 cycles. In addition, in contrast to other CoS-based composite anodes reported, the as prepared nanocomposite anodes present the superior rate performance. And the CoS@rGO-2 nanocomposite delivers specific capacities of 892.1 and 668.5 mA h g−1, at respective 1000 mA g−1 and 2000 mA g−1. The unique nanostructure of the electrode materials accounts for the superior electrochemical behaviors. Furthermore, the rGO embedded in the nanocomposites can effectively buffer the volume variation, mitigate the aggregation of CoS particles, and prevent the CoS particles from dropping off the electrode during the cycling process. These notable electrochemical characteristics indicate promise of the nanocomposites as anode materials in LIBs.The CoS@rGO nanocomposites were synthesized through a facile solvothermal method. Some favorable electrochemical performances in specific capacity, cycling performance and rate capability are achieved when the nanocomposites were used as anode materials for LIBs. For a half-cell, the CoS@rGO-2 nanocomposite anode exhibited a capacity of 1253.9 mA h gThere are no conflicts to declare.RA-010-D0RA01351J-s001


However, during the insertion/de-insertion process, Mn3O4 suffers from particle aggregation, poor conductivity, and low-rate capability, which, in turn, limits its practical application. To overcome these obstacles, we have successfully prepared Mn3O4 nanoparticles distributed on the nitrogen (N)-doped and nitrogen, sulphur -doped reduced graphene oxide (rGO) aerogels, respectively. The highly crystalline Mn3O4 nanoparticles, with an average size of 15–20 nm, are homogeneously dispersed on both sides of the N-rGO and N,S-rGO aerogels. The results indicate that the N-rGO and N,S-rGO aerogels could provide an efficient ion transport channel for electrolyte ion stability in the Mn3O4 electrode. The Mn3O4/N- and Mn3O4/N,S-doped rGO aerogels exhibit outstanding electrochemical performances, with a reversible specific capacity of 374 and 281 mAh g−1, respectively, after 100 cycles, with Coulombic efficiency of almost 99%. The interconnected structure of heteroatom-doped rGO with Mn3O4 nanoparticles is believed to facilitate fast ion diffusion and electron transfer by lowering the energy barrier, which favours the complete utilisation of the active material and improvement of the structure’s stability.Owing to their high theoretical capacity, transition-metal oxides have received a considerable amount of attention as potential anode materials in sodium-ion (Na-ion) batteries. Among them, Mn SHE) for Na-ion, most examined electrodes, especially the anode, are not ideal hosts for Na-ion insertion .,53.3O4, aerogels . Both Mn3O4 agglomerated in a size of 0.5–1.1 µm, which is an aggregate of individual Mn3O4 nanoparticles, anchored uniformly on the porous N-rGO . A typical crumpled structure of rGO and interconnected and cross-linked random rGO layers construct a 3D framework with open-pore structures ). The HRTEM images  plane of the tetragonal phase of the Mn3O4 nanoparticles. These results suggested that the Mn3O4 nanoparticles have a strong connection and network with the heteroatom-doped rGO aerogels, which is in accordance with the SEM images.Further characterisation of the morphology and structure of the Mnructures a,b. The M images e,f show −1, respectively, were observed in the heteroatom-doped rGO aerogels. The G band reflected the radial C-C stretching of ordered sp2 -linked carbon atoms, whereas the D band indicated the defects or irregularities on the graphene edges [ID/IG) for the N-rGO aerogel was 0.95, whereas it was 0.98 for the N,S-rGO aerogel. After the nitrogen and sulphur doping, defects were introduced to the rGO aerogel layers [ID/IG ratios of the Mn3O4/N-rGO and Mn3O4/N,S-rGO aerogels increased to 0.98 and 1.00, respectively. Two peaks at 658 and 369 cm−1 were observed in the Mn3O4/N-rGO and Mn3O4/N,S rGO aerogels, respectively [2+ ions and thus demonstrated that Mn3O4 is successfully attached to the rGO layer [−1 were associated with the second-order two-phonon mode 2D band. It is worth noting that the Raman spectrum associated with Mn3O4 in the Mn3O4/N-rGO and Mn3O4/N,S-rGO aerogels was shifted to a low wavenumber in comparison with the pristine Mn3O4, indicating the electronic coupling between Mn3O4 and heteroatom rGO aerogel.The disordered degree of the heteroatom-doped rGO aerogels was characterised via Raman spectroscopy and is presented in ne edges ,59. Furtl layers ,61, wherectively ,63. ThesGO layer ,65. Addi3O4/N-rGO and Mn3O4/N,S-rGO aerogels to further support the presence of heteroatom in the rGO aerogel, as well as the Mn3O4 nanoparticles in the nanocomposites. The peak positioned at 1730, 1363, and 1215 cm−1 corresponded to the stretching vibration C=O of carboxylic groups, O-H deformation, and C-O stretching vibration from epoxy groups, respectively, indicating that GO was successfully converted into rGO [−1 associated with the absorption band of C=S and S-H stretching vibration, respectively, was observed in the N,S-rGO and Mn3O4/N,S-rGO aerogels and, thus, confirmed the presence of S atom on the surface of N,S-rGO aerogel samples [−1 could be assigned to the characteristic band of nitrogen doping. For the Mn3O4 nanoparticles, the strong peaks at 528 and 621 cm−1 were attributed to the Mn-O stretching of the tetrahedral and octahedral sites in Mn3O4 [3O4 nanoparticles were successfully integrated into the heteroatom rGO layers.into rGO ,67. The  samples . In addi3O4/N,S-rGO and Mn3O4/N-rGO aerogels, respectively. From the survey scan XPS spectra, the presence of nitrogen  for the Mn3O4/N-rGO aerogel. Thus, it further confirmed the presence of N and S-atoms in the nanocomposites [3/2, S p1/2, and SOx, respectively, indicating the existence of Mn-S [3O4/N-rGO and Mn3O4/N,S-rGO aerogels is presented in 3/2 and Mn 2p1/2, respectively, indicating the existence of the Mn species, implying the possible presence of Mn3O4 in the nanocomposites [3/2 and Mn 2p1/2 were 12.2 and 11.4 eV for the Mn3O4/N,S-rGO and Mn3O4/N-rGO aerogels, respectively, and were in accordance with other earlier reports [3O4 nanoparticles have formed in the Mn3O4/N-rGO and Mn3O4/N,S-rGO aerogels.The XPS technique was used to obtain further insight into the chemical states of elements on the surface of the samples. nitrogen a and nitnitrogen b is notiFor O 1s c,d, the For O 1s e,f couldmposites . Figure mposites . As can  of Mn-S ,71. The mposites . The spl reports , which f3O4 to MnO as well as the formation of Na2O, which is attributed to the decomposition of the electrolyte according to Equation (1)To evaluate the sodium storage performances of the samples, the CV and galvanostatic charge/discharge testing have been conducted in a half-cell within the potential range of 0.01–3.00 V. As can be seen from The peaks at 0.45 to 0.01 V could be attributed to the reduction of MnO to metallic Mn (Equation (2)) and solid electrolyte interphase (SEI) layer formation on the electrode surface of the electroactive material.3O4/heteroatom rGO aerogel was reversible during the insertion/de-insertion process of Na+ ions [+ extraction into the graphitic carbon layers, which was the inverse process of Na+ intercalation. When compared with Li-ion batteries, the CV peaks in Na-ion batteries were broader and weaker. This may be due to the larger radius of Na+ than Li+ and the slower Na+ intercalation between graphitic carbon layers [3O4/N-rGO aerogel .During subsequent cycles, the CV curves nearly overlapped, indicating that the MnNa+ ions . The tinn layers ,76. Cont aerogel b, the Mn aerogel c exhibit3O4 and the Mn3O4/N-rGO and Mn3O4/N,S-rGO aerogels electrodes for selected cycles at a current density of 0.1 A g−1. The subsequent CV curves are different from the first sodiation, and the discharge plateau for the Mn3O4/N-rGO and Mn3O4/N,S-rGO aerogels is much longer than the pristine one, indicating that more Na-ions can be inserted into these nanocomposites [mposites . Further3O4, Mn3O4/N-rGO aerogel and Mn3O4/N,S-rGO aerogel were measured to be 522, 1950, and 884 mAh g−1, respectively. In the second cycle, the discharge capacities were 336, 470, and 425 mAh g−1 for Mn3O4, Mn3O4/N-rGO aerogel and Mn3O4/N,S-rGO aerogel, respectively. The irreversible capacity loss was mainly due to the irreversible formation of the SEI layer. Interestingly, the Mn3O4/N-rGO aerogel maintained its discharge capacity at 374 mAh g−1 after 100 cycles with an 80% retention rate. Contrarily, the Mn3O4/N,S-rGO aerogel and Mn3O4 exhibited much lower discharge capacities of 281 mAh g−1 (68% retention rate) and 185 mAh g−1 (55% retention rate) after 100 cycles. For the few initial cycles, the porous structure of rGO aerogel promoted the formation of excessive SEI layers, resulting in a lower initial Coulombic efficiency [3O4/N,S-rGO aerogel electrodes demonstrated much lower discharge capacity, presumably because of the large atomic radius of S, as well as the large crystallite size than that of Mn3O4/N-rGO aerogel electrodes.The cycling stability of all electrodes is presented in ficiency . Overall3O4/N-rGO and Mn3O4/N,S-rGO aerogel electrodes exhibited remarkable rate performance, as presented in 3O4/N-rGO aerogel electrode exhibited discharge capacities of 203, 166, 145, 135, 128, and 156 mAh g−1 at various current densities of 0.2, 0.4, 0.6, 0.8, 1.0, and returning to 0.2 A g−1. The minimal drop in capacities with increased current densities indicated a higher degree of reversible Na-ion insertion/de-insertion owing to their expanded interlayer spacing [3O4/heteroatom-doped rGO aerogels may be due, in part, to the 3D porous structure, which may minimise the electron and ion transport path.In addition to their high discharge capacity and good cycling stability, the Mn spacing . The imp3O4/N-rGO aerogel and Mn3O4/N,S-rGO aerogel were improved, which benefitted from the synergistic effect of the heteroatom doping and porous structure of the rGO, as well as the small particle sizes of Mn3O4. The rGO sheets as well as the porous structure in the conductive network of the Mn3O4/heteroatom rGO aerogels provided an efficient electron and ion transport path, thereby decreasing the internal resistance to enhance the reaction kinetics and resulting in a high specific capacity and rate capability [3O4 nanoparticles anchored on rGO can prevent the restacking of the rGO layers, preserve their high active surface area and maintain the channels for Na-ion diffusion, which is advantageous for increasing the Na storage within the nanocomposites [3O4/heteroatom-doped rGO aerogels. This strategy can be used as one of the approaches for mitigating the large volume change and poor electrical conductivity, which is associated with bare transition-metal oxide anodes.The specific capacity and cyclability of the Mnpability ,82,83. Ppability . Meanwhimposites . Doping mposites . The incmposites ,87,88, t3O4/heteroatom-doped rGO aerogels have been successfully synthesised via a hydrothermal route, followed by a freeze-drying process using NH3 and L-cysteine as nitrogen and nitrogen–sulphur sources, respectively. The aerogel structure built well-interconnected heteroatom-doped rGO layers, and the Mn3O4 nanoparticles distributed on the rGO layers prevented the graphene layers from restacking again. The 3D structure provides a large active surface area and eases electron diffusion and Na-ion transportation. Both the N- and N,S-doped rGO aerogels with Mn3O4 exhibited high specific capacity, excellent cycling stability, and rate capability than the pristine Mn3O4. The heteroatom-doped rGO aerogel acts as a robust structure to accommodate the volume expansion of Mn3O4 nanoparticles and enables reversible Na-ion insertion/de-insertion. Our work demonstrates that N- and N,S-doped rGO aerogels can efficiently improve the Na storage capacity of Mn3O4 and offer a useful strategy for synthesising high-yield anode materials. Considering the simple step of the preparation process and the excellent cycling stability of the samples, the Mn3O4/heteroatom-doped rGO aerogel can be considered a potential candidate and provide an opportunity to explore these materials for the next generation of Na-ion batteries.In summary, the Mn


Sodium carboxymethyl cellulose (CMC) is firstly applied as the binder for ZnS based anodes and shows a more advantageous binding effect than PVDF. To simplify the synthesis procedure, l-cysteine is added as the sulfur source for ZnS and simultaneously as the reducing agent for rGO. The average diameter of ZnS nanoparticles is measured to be 13.4 nm, and they uniformly disperse on the rGO sheets without any obvious aggregation. As anode materials, the CMC bound ZnS–rGO nanocomposites can maintain a high discharge capacity of 705 mA h g−1 at a current density of 500 mA g−1 for 150 cycles. The significantly improved electrochemical performance mainly derives from the combined effects of the small and uniformly dispersed ZnS nanoparticles, the high conductivity and structural flexibility of rGO and the strong binding ability of CMC.ZnS nanoparticles are  in situ grown on reduced graphene oxides (rGO) via a simplified one-step hydrothermal method.ZnS nanoparticles are  Among the vastly investigated anode materials, ZnS is a promising candidate as it possesses a high theoretical capacity of 962 mA h g−1.3 The naturally abundant zinc and sulfur are cheap and environmental friendly, which makes ZnS anodes even more advantageous. But the practical application of ZnS based anode materials is still hindered by their low rate capability and severe capacity decay which are caused by their low conductivity and huge volume expansion during cycling. Thus it is imperative to find effective methods to solve these problems.The ever growing demand for green and high-efficiency energy storage devices has greatly promoted the development of the lithium-ion batteries (LIBs) industry. However, the power and energy density of current commercial LIBs still cannot satisfy the high requirements of next generation batteries which are expected to be applied in electric vehicles.4–6 And among the various carbon based materials, reduced graphene oxide (rGO) is an ideal performance-enhancing additive because of its high electrical conductivity, large surface area and excellent structural flexibility.7–9 Actually, the advantages of the above two strategies can be combined through the fabrication of composite materials which contain rGO nanosheets and uniformly dispersed ZnS nanoparticles. But synthesizing such ZnS–rGO nanocomposites with desired particle size and morphology is not an easy task because zero-dimensional nanoparticles often suffer from severe aggregation problems. Aggregated particles will block the penetration of electrolyte, decrease the ion transport efficiency and lower the utilization of active materials.10–12 Moreover, rGO is usually obtained by the reduction of graphene oxide (GO), which means the need for extra reducing agent (like toxic hydrazine) or additional thermal annealing process.13,14 And how to guarantee the firm adhesion of ZnS nanoparticles on the rGO sheets is another problem that should be considered. Physically adsorbed particles can be easily peeled off from rGO, which will result in the loss of cell capacity. Considering these issues, it is obvious that green and simplified method is still urgently needed to fabricate stable ZnS–rGO nanocomposites while ensuring the uniform dispersion and firm adhesion of ZnS particles.For ZnS anode materials, reducing the particle size to the nanometer scale and compositing ZnS with carbon materials are two adoptable strategies to improve their long-term cycling stability and rate performance. Nanosized materials, especially nanoparticles and nanodots, are quite advantageous as their shortened ion and electron transport path will greatly facilitate the lithium storage process at high current rate.15,16 So PVDF also seems not to be a good choice for ZnS since alloying and conversion reactions are both existed in its charge–discharge process. Compared with PVDF, sodium carboxymethyl cellulose (CMC) is probably more suitable for ZnS as it can offer a homogeneous 3D networking around the active materials, endowing the electrode with stronger ability to accommodate mechanical stress.17 The successful application of CMC in Si and metal oxides anodes further demonstrates its advantage.18–20 However, to the best of our knowledge, whether CMC binder has a positive effect on ZnS anodes has not yet been reported. Figuring this out would be meaningful as it may provide an easy and scalable way to improve the cycling performance of ZnS.In addition to optimizing ZnS anodes from the structural and materials preparation aspects, choosing suitable binder for ZnS is also of great importance. Traditional PVDF binder has been proved to be inappropriate for anode materials based on alloying or conversion mechanism because it is difficult for PVDF to withstand the huge volume expansion that is involved.in situ grow ZnS nanoparticles on rGO and firstly use CMC as the binder for ZnS based anodes. In the synthesis procedure, l-cysteine is added as both the sulfur source for ZnS and simultaneously as the reducing agent for rGO. No extra annealing treatment or reagent is needed to complete the reduction process. The introduced rGO has proved itself to be a desirable matrix as it can improve the dispersity of ZnS and enhance the conductivity and structural stability of the as-prepared composite materials. The binding effect of CMC has been compared with traditional PVDF binder. With the synergistic effects of the flexible rGO nanosheets, firmly attached ZnS nanoparticles and the advantageous CMC binder, the ZnS–rGO nanocomposites exhibit a much enhanced electrochemical performance.Based on the above considerations, herein we develop a simplified one-step hydrothermal route to 3COO)2·2H2O, l-cysteine were used as received without further purification. GO was prepared by the oxidation of natural flake graphite powder by a modified Hummers method.21 Typically, 3 mmol Zn(CH3COO)2·2H2O was dissolved into 50 ml deionized water under magnetic stirring for 10 minutes. Then 10 ml of 2.0 mg ml−1 GO aqueous suspension was added and treated by ultrasonication for 30 minutes. Subsequently, 4.5 mmol l-cysteine was dissolved into the above solution. After being vigorously stirred for 20 minutes, the resulting mixture was transferred into a Teflon-lined stainless steel autoclave and heated to 180 °C for 12 h. The product was collected by centrifugation and washed thoroughly by deionized water and absolute ethanol. After being dried in air at 60 °C for 12 h, the ZnS–rGO nanocomposites (denoted as ZSG) were obtained. As control samples, pure ZnS (denoted as ZS) and rGO were also prepared using the same method without the addition of GO suspension or Zn(CH3COO)2·2H2O.Analytical-grade Zn with Cu Kα radiation (λ = 1.5406 Å). ESCALAB 250 spectrometer with Al Kα X-ray source was used to collect the X-ray photoelectron spectroscopy (XPS) data. The morphology of the as-prepared samples is observed by field emission scanning electron microscopy . Thermogravimetric analysis  was carried out under air flow (100 ml min−1) at a heating rate of 10 °C min−1. Raman spectra measurements were recorded on a Renishaw InVia Raman microscope with an excitation wavelength of 633 nm. TEM and HRTEM images were obtained by a FEI-TECNAI G2 F20/America microscope.The crystallographic structure and phase purity of as-prepared samples were characterized by X-ray diffraction , ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 1 : 1 : 1, and 1 M LiPF6 was dissolved in the mixture, which was used as the electrolyte. A LAND CT2001A battery instrument was applied to perform galvanostatic charge–discharge tests at various current densities in 0.01–3.0 V. The cyclic voltammetry (CV) tests were conducted in 0.01–3.0 V at a scan rate of 0.1 mV s−1 on a CHI650D electrochemical workstation. Electrochemical impedance spectra (EIS) measurements were also recorded on the CHI650D electrochemical workstation with an AC signal amplitude of 5 mV from 0.01 Hz to 100 kHz.The working electrode is prepared by mixing active materials, acetylene black and polyvinylidene fluoride (PVDF) or sodium carboxymethyl cellulose (CMC) to form a homogenous slurry. The weight ratio of the active materials, conducting agent and binder is 7 : 2 : 1. The slurry was uniformly pasted on a copper foil and then dried at 70 °C for 12 h in a vacuum oven. The electrode materials prepared with PVDF is denoted as ZS–PVDF, ZSG–PVDF and rGO–PVDF. Similarly, electrode using CMC as the binder is denoted as ZS–CMC, ZSG–CMC and rGO–CMC. CR2025-type half-coin cells were assembled in an argon filled glove box with Hl-cysteine, Raman spectroscopy measurements were carried out on ZSG and pristine GO powder. The Raman spectra displays disorder-induced D band (∼1350 cm−1) and tangential G band (∼1590 cm−1) in ID/IG value of ZnS–rGO is 1.14, and the value for GO is 1.03. The increased ID/IG value indicates the successful reduction of GO as it can decrease the average size of the sp2 domains.22,23 And among all the reagents, only l-cysteine possesses the ability to reduce GO.24 Thus it is obvious that l-cysteine, with its strong reducibility and excessive amount, has successfully reduced GO to rGO.The crystal structure and phase purity of the as-prepared products were characterized by XRD . All the1/2 and Zn 2p3/2 peaks are found at 1044.5 eV and 1021.4 eV in the high-resolution spectra of Zn 2p in 25 For the S 2p spectra in 1/2 and S 2p3/2 spin orbit peaks of ZnS. For ZSG, the successful reduction of GO can also be proved by the change of C 1 s XPS spectra. Four peaks are detected in the C 1 s spectra of unreduced GO in  PBM data was replaced with SVG by xgml2pxml:<glyph-data id="z.dbd" format="PBM" resolution="300" x-size="8" y-size="10" xml:space="preserve">00000000000000000000000000000000111111110000000011111111000000000000000000000000</glyph-data><svg xmlns="http://www.w3.org/2000/svg" version="1.0" width="13.200000pt" height="16.000000pt" viewBox="0 0 13.200000 16.000000" preserveAspectRatio="xMidYMid meet"><metadata>Created by potrace 1.16, written by Peter Selinger 2001-2019</metadata><g transform="translate scale" fill="currentColor" stroke="none"><path d="M0 440 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z M0 280 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z"/></g></svg>C bond. The binding energy of the CC bond is slightly deviated from the usually reported value (∼284.6 eV).26 This might be caused by the modification of the electronic structure of GO by some electronic acceptor molecules. As reported by Mullen, the electronic donor and acceptor molecules within the functional groups on graphene can modify its electronic structure, which can lead to the upshift/downshift of the carbon peaks in the XPS spectra.27 Moreover, the defective carbon structures on GO also possess the ability to reduce the binding energy of CC bond and cause the downshift of the XPS peak.28 Considering the complex electronic and defective structures of GO, further investigation is still needed to figure out the detailed mechanism. The other three peaks at 285.8, 286.3 and 287.5 eV are typical C–O, CO and O–CO bonds in GO.29 In contrast, the peak intensity of these oxygen-containing bonds decreases dramatically in the C 1 s spectra of ZSG  and differential scanning calorimetry (DSC) were conducted in air to evaluate the rGO content in the composites (X-ray photoelectron spectroscopy (XPS) analysis was carried out to further verify the reduction of GO and investigate the oxidation state of the component elements in ZSG. As shown in a of ZSG , indicatmposites  and S1†.2 adsorption–desorption measurement. Type IV isotherm with a distinct hysteresis loop in relative pressure of 0.45 < P/P0 < 1.00 is observed in 2 g−1, respectively, proving that the introduction of rGO has increased the surface area of the composites. Large surface area is beneficial as it can increase the contact area between the electrode and electrolyte and provide more active sites for electrochemical reactions.31 It is apparent that the ZSG sample, with the in situ formed ZnS nanoparticles and the wrinkled rGO nanosheets, possesses a more advantageous nanostructure than the ZS sample.32The TEM images in −1 in 0.01–3 V. During the first cathodic scan, the broad and weak reduction peak below 0.8 V is related with the reduction of ZnS to metallic zinc and the formation of Li2S.33 Besides, the Li–Zn alloying process and formation of SEI film also take place in this voltage range.34 During the first anodic scan, three small peaks are observed in 0.01–0.7 V, which can be assigned to the multi-step dealloying process of Li–Zn alloys. The oxidation peak at ∼1.4 V corresponds to the back conversion of metallic zinc to ZnS. The corresponding reversible reactions are summarized as follows:To investigate the electrochemical performance and compare the binding effect of CMC and PVDF, ZS and ZSG electrode materials are prepared with both the two sorts of binders, and they are denoted as ZS–PVDF, ZSG–PVDF, ZS–CMC and ZSG–CMC, respectively. As shown in + into the nanocomposites. Such phenomenon is also reported in other metal oxides with small particle size.35–37 The irreversible formation of SEI film has led to the change in the curve shape of the second cathodic scan. The peaks corresponding to the reduction of ZnS has right shifted to voltage above 0.8 V. The CV curves coincide well from the second cycle onwards, indicating the good reversibility of ZSG. As for the CV peaks of rGO, the insertion of Li+ should appear around 0.5 V and the extraction of Li+ from rGO happens in a wide voltage range from 0.05 to 3 V.13 However, the overlap of the reaction voltage with ZnS and the low content of rGO in the nanocomposites has made the peaks corresponding to rGO invisible in −1 in 0.01–3 V. The slope ranging from 0.01–0.7 V in the first discharge curve and the plateau around 1.4 V in the first charge curve are consistent with the above CV results. During the first cycle, the ZnS–rGO nanocomposites deliver an initial discharge and charge capacity of 1184 mA h g−1 and 625 mA h g−1, exhibiting a relatively low coulombic efficiency of 55.1%. The large capacity loss is mainly due to the formation of the solid electrolyte interphase (SEI) layer.38 In the 2nd, 10th and 30th cycle, the coulombic efficiency has increased to 80.9%, 96.2% and 98.7%, demonstrating the high reversibility of the electrode materials.Interestingly, in the first scanning cycle, one tiny cathodic peak at ∼1.6 V and two anodic peaks at ∼1.8 V and ∼2.3 V are observed and they gradually disappear in subsequent cycles. This can be ascribed to the insertion and extraction of a small amount of Li−1 is displayed in −1 and 1334 mA h g−1. Then the capacity of ZS–PVDF gradually decreases and drops to 337 mA h g−1 in the 35th cycle while the ZSG–PVDF sample can maintain a stable capacity of 496 mA h g−1. This suggests that the incorporation of rGO with ZnS has effectively helped to buffer the volume expansion, making the electrode more stable during charge–discharge cycles. When CMC is used as the binder, the cycling performance of ZSG is further improved. It can deliver an initial discharge capacity of 1184 mA h g−1 and maintain at 645 mA h g−1 after 35 cycles, retaining 54.5% of its initial capacity, which is much higher than that of ZSG–PVDF (37.2%). The improved capacity retention may mainly derive from the stronger binding ability of CMC than PVDF.18 During cycling, the carboxylic groups in CMC can form hydrogen binding with ZnS nanoparticles, alleviating pulverization and therefore increase the utilization rate of the active materials. Though the content of rGO in the nanocomposites is low and its contribution to the capacity of the electrode is limited, investigating the performance of pure rGO anodes is necessary and would be conducive to the understanding of the electrochemical properties of ZSG. The cycling performance of rGO–PVDF and rGO–CMC is shown in Fig. S2a.−1 and maintained at 574 mA h g−1 after 35 cycles at 100 mA g−1, while the rGO–PVDF can also retain a stable capacity of 443 mA h g−1.The cycling performance of ZS–PVDF, ZSG–PVDF, ZS–CMC and ZSG–CMC at 100 mA g−1 to 2 A g−1. ZS–PVDF can only retain 52 mA h g−1 and ZSG–PVDF can hold a capacity of 174 mA h g−1 at 2 A g−1. The improved rate performance of ZSG–PVDF mainly derives from the good conductivity of rGO and the uniformly dispersed nanosized ZnS particles. On the one hand, the problem of low conductivity of ZnS will be ameliorated after the introduction of rGO. On the other hand, the small particle size and uniform dispersion of ZnS will shorten the diffusion length of ions and electrons, offer larger surface area for reactions and facilitate the penetration of electrolyte. Interestingly, ZS–CMC shows a much inferior capacity than ZSG–PVDF at low current density, but the capacity gap narrows with the increase of current and even becomes comparable at 2 A g−1. The low-density PVDF binder possess a porous structure. Such structure can guarantee a good immersion of active materials in the electrolyte. That is why the PVDF bound ZSG shows comparable electrochemical performance at low current density. However, according to Winter et al., the porous nature of PVDF will result in a low electronic conductivity, thus weakening the electrode performance under high current rate.39 In comparison, the relatively compact CMC binder is not faced with this problem. Its performance under high rates is only limited by the Li diffusion coefficient within the electrode materials. Moreover, there are also reports showing that CMC could modify the Li diffusion coefficient and accelerate the ion transport, thus leading to a more advantageous rate capability.40 ZSG–CMC still displays the highest rate performance with capacities of 379 mA h g−1 at 1 A g−1 and 325 mA h g−1 at 2 A g−1. Moreover, its capacity can recover to 640 mA h g−1 after the current is changed back to 100 mA g−1. For pure rGO  which reflects the diffusion of lithium ions in electrode appears as the slope long line in the low frequency region. It can be clearly seen that the diameter of the curve of ZSG–CMC is smaller than the other three samples, indicating that the nanocomposites possess a lower charge transfer resistance and higher conductivity. This is further verified by the fitting results. The inset of Rct value for ZS–PVDF, ZSG–PVDF, ZS–CMC and ZSG–CMC are 388.7 Ω, 59.9 Ω, 61.7 Ω and 47.1 Ω, respectively. Lower charge transfer resistance means a higher transport efficiency of Li+ ions through the interface of the electrode and electrolyte, which is conducive to the enhancement of rate capability of the electrode materials.47To gain more information about the nanocomposites, electrochemical impedance spectroscopy (EIS) measurements were performed after the cells were tested at 500 mA gThe excellent electrochemical performance of ZSG–CMC can be ascribed to the following reasons. Firstly, the high structural flexibility and conductivity of rGO can help to alleviate the huge volume expansion and increase ion transport efficiency of the composite materials. Secondly, the small particle size and uniform dispersion of ZnS can offer larger surface area for reactions and facilitate the penetration of electrolyte, guaranteeing a high utilization of active materials. Thirdly, the conversion reaction mechanism and small size of ZnS can trigger a capacity increase phenomenon through the formation of gel-like films and pseudo-capacitive behavior. Finally, the CMC binder can provide a strong binding effect to alleviate pulverization and to some extent modify the Li diffusion coefficient to further improve the rate capability. These advantages have combined to enhance the overall cycling stability and rate capability of the ZSG–CMC electrode.via a simplified one-step hydrothermal route and CMC is firstly used as the binder for the ZnS based anode. With an average diameter of 13.4 nm, ZnS nanoparticles are uniformly anchored on rGO nanosheets. l-cysteine plays an indispensible role during the whole fabrication process as it not only serves as the sulfur source for ZnS but also acts as the reducing agent for rGO. The incorporation of rGO and ZnS has successfully alleviated the severe aggregation of ZnS nanoparticles. Besides, rGO has also endowed the composites with higher electronic conductivity and structural flexibility. The CMC binder can provide a strong binding effect to further stabilize the electrode, thus guaranteeing a higher capacity retention. Owing to these beneficial features, the CMC binded ZnS–rGO nanocomposites can retain a high discharge capacity of 705 mA h g−1 at 500 mA g−1 for 150 cycles. The excellent electrochemical performance fully demonstrates that the ZnS–rGO nanocomposites are quite promising as high-performance anode materials for next generation Li-ion batteries. And the idea of adding l-cysteine as the sulfur source and reducing agent to simplify the synthesis procedure can be extended to fabricate other metal sulfides–rGO composites.In summary, ZnS–rGO nanocomposites are synthesized There are no conflicts to declare.RA-008-C8RA00470F-s001


Nfkb, Trem2 , GFAP (astrocyte marker), Il1b, and S100a8 in DSS-treated mice. While the expression of Nfkb, Trem2, and GFAP showed a peak on day 10, the S100a8 expression was high on days 10 and 17 and subsided on day 42. Interestingly, expression of Bdnf remained elevated in the times assessed . Together, these results demonstrated that DSS-induced colitis could induce prolonged neuroinflammation and impaired contextual fear memory.Accumulating evidence has shown that intestinal inflammations in inflammatory bowel disease (IBD) also drive pathological responses in organs outside the intestine, including the brain. Previous studies using the dextran sodium sulfate (DSS)-induced colitis model have shown that colonic inflammation contributes to the development of anxiety- and depression-related behaviors; however, little is known about whether memory function is affected. Here, we subjected male and female C57BL/6J mice to DSS-induced colitis for 6 days, followed by Pavlovian conditioned fear (CF) tests 15 days after the start of inflammation, when local colonic inflammation has receded. The contextual and cued CF tests were used to assess associative fear memory. We found that DSS-induced colitis led to significant impairment in contextual fear memory in both male and female mice; on the other hand, auditory cued fear memories were comparable between control and DSS-treated mice. There were marked signs of astrogliosis in the hippocampal regions 17 days (D17) after colitis induction. Furthermore, molecular characterization of hippocampi showed marked but transient increases in the expression of inflammatory genes The online version contains supplementary material available at 10.1186/s13041-022-00961-4. The prevalence of inflammatory bowel disease (IBD), a chronic inflammatory condition of the gastrointestinal tract, continues to rise . IBDs, iTo model IBD in rodents, dextran sulfate sodium (DSS)-induced colitis has been widely used, which elicits intestinal pathologies similar to human ulcerative colitis . PreviouIn the present study, we subjected male and female C57BL/6J mice to DSS-induced colitis for 6 days, followed by Pavlovian conditioned fear (CF) tests 15 days after the start of colitis induction  . Some male mice showed cued fear response below the 5% threshold and were excluded from data analysis, while all female mice responded. Overall, freezing behaviors for auditory cues were comparable between control and DSS-treated mice  and recovered gradually after cessation of DSS Fig. b. FemaleNfkb, Trem2 , Gfap, and Il1b were significantly increased on day 10 and decreased thereafter to basal levels by day 42, except for Il1b  peaked on day 17 and subsided to basal level on day 42 (Fig. Bdnf remained elevated compared to control (Fig. It has been shown that contextual information is encoded by neurons in the hippocampus and conveyed directly to the amygdala, which generates conditioned fear responses , 11. Nex colitis . InteresIn conclusion, our study showed that contextual memory function was negatively impacted by an episode of colitis, with prolonged neuroinflammation in the hippocampal regions. Further work is required to determine mechanistically the interactions between innate neuroinflammatory response and neurons encoding specific inputs to hippocampal-amygdala neurocircuit to affect contextual fear memory . Of noteAdditional file 1. Experimental Methods.


Crocodilians are an order of ancient reptiles that thrive in pathogen-rich environments. The ability to inhabit these harsh environments is indicative of a resilient innate immune system. Defensins, a family of cysteine-rich cationic host defence peptides, are a major component of the innate immune systems of all plant and animal species, however crocodilian defensins are poorly characterised. We now show that the saltwater crocodile defensin CpoBD13 harbors potent antifungal activity that is mediated by a pH-dependent membrane-targeting action. CpoBD13 binds the phospholipid phosphatidic acid (PA) to form a large helical oligomeric complex, with specific histidine residues mediating PA binding. The utilisation of histidine residues for PA engagement allows CpoBD13 to exhibit differential activity at a range of environmental pH values, where CpoBD13 is optimally active in an acidic environment. Defensins are a class of host defence peptides that contribute to the immune system of eukaryotes. Here, the authors report the structure of saltwater crocodile defensin CpoBD13 and the mechanism of pH-dependent antifungal activity. During this time, these animals have evolved to thrive in microbe-laden environments. Yet despite regularly receiving wounds and even losing limbs in territorial disputes and interspecies conflicts, the development of infection is rare2. This unique ability to ward off pathogens before they can invade systemically is indicative of a formidable innate immune system1. A major constituent of an organism’s innate immune system are defensins; a family of cysteine-rich cationic host defence peptides (CHDPs) that harbor a broad range of activities, including direct microbicidal properties and inflammatory response signalling4. Defensins are grouped into two major superfamilies based on their intramolecular disulphide bonds; cis-defensins  and trans-defensins (expressed by vertebrates and invertebrates)4. Within vertebrates, the trans-defensins are further subdivided into three sub-families termed the α-, β- and θ-defensins, with their distinguishing feature being the cysteine-pairing order of their disulphide bonds. While α- and θ-defensins are unique to mammals and old-world primates respectively, β-defensins are the most abundant and expressed by all vertebrates4.Crocodilians are an order of ancient reptiles that have existed in their modern-day forms for approximately 83 million years5, fungi6, viruses7 as well as tumourigenic cells8. This broad range of activities is primarily attributed to the destabilisation of the target cell plasma membrane, leading to death by lysis9. This mechanism of action was first characterised in plant defensins that were found to directly target and bind negatively charged phospholipids. Target phospholipids are typically members of the phosphatidylinositol phosphate (PIP) family and interact electrostatically with cationic residues of the defensin 11. Engagement of a target lipid by plant defensins triggers the formation of oligomeric defensin–lipid complexes which place torsional stress on the membrane until the point of lysis. Recently, this ability to target PIPs has been shown to be conserved in β-defensins, specifically human β-defensin 2 (HBD-2), which was able to kill the human pathogenic fungus Candida albicans through the binding of phosphatidylinositol 4,5-bisphosphate P2)6. While plant and human defensins have been studied in detail11, the defensins of other phyla, including reptiles, are poorly characterised.β-defensins effectively inhibit and/or kill a wide range of pathogens including bacteriaCrocodylus porosus β-defensin 13 (CpoBD13). Our findings reveal that despite limited primary sequence identity, the three-dimensional structure of CpoBD13 bears a striking resemblance to HBD-2, suggesting strong evolutionary conservation of the β-defensin structure between humans and reptiles. Furthermore, we have also determined the structure of CpoBD13 bound to phosphatidic acid (PA), which identifies a continuous helical oligomer and reveals in atomic detail how trans-defensins are able to form large oligomeric membrane attack complexes. Importantly, we show that CpoBD13 permeabilises fungal cell membranes in a pH-dependent manner as a result of histidine-mediated binding of PA, revealing a mechanism to regulate defensin antimicrobial potency.We now report the functional and structural characterisation of C. porosus open reading frames acquired from the NCBI nucleotide database for potential defensin genes. CpoBD13, the homologue of avian β-defensin-13 and Alligator sinensis β-defensin-13, was selected for further characterisation based on its unusual amino acid sequence that featured a high proportion of histidine residues  to pH +8 (at pH 5.5), we surmised that changes in the net charge of CpoBD13 may impact its functionality. To assess if changes in the environmental pH modify the membrane-permeabilising activity of CpoBD13, we repeated the PI uptake assays in buffered media , the net charge of CpoBD13 is significantly altered by the pH of its surrounding environment Fig. . As the dia Fig. . At pH 5C. albicans with fluorescently labelled CpoBD13 and observed the process by confocal microscopy -tagged CpoBD13 in lipid overlay assays on PIP Strips Fig.  bound oncis-defensins and adopt large intricate protein:phospholipid oligomeric complexes. In contrast, whilst trans-defensins (such as those found in humans) have been shown to bind phospholipids, the atomic detail of putative large oligomeric defensin:phospholipid complexes remain to be determined11. Consequently, we subjected CpoBD13 to chemical crosslinking analysis in the presence and absence of PA 5, clear dimers are observed at 0 and 23 µM PA concentrations. At 115 µM PA, multiple higher order bands are clearly observable, indicative of multimeric complexes up to the size of pentamers. To visualise the morphology of these higher order complexes, samples of CpoBD13, PA only and CpoBD13:PA were examined by transmission electron microscopy (TEM)  Fig. . CpoBD13To understand the structural basis of CpoBD13 activity, we determined its atomic structure using X-ray crystallography. A single copy of CpoBD13 was found in the asymmetric unit, with clear and continuous density observed for the entire protein chain. CpoBD13 adopts a fold comprising the family-defining structural elements observed in mammalian β-defensins comprising a single α-helix and a three-stranded β-sheet, which are connected via three disulphide bonds. A Dali analysis of CpoBD13 revealed that human β-defensin-2 (HBD-2) is the closest structural homologue in the Protein Data Bank (PDB), with a rmsd of 0.8 Å (Z-score 6.2) over 40 Cα atoms, and a peptide sequence identity of 26% .An overlay of the two defensin structures Fig.  revealedIn contrast, the type I site Fig.  featuresTo further understand the role of PA interactions for CpoBD13 activity, we performed structure-guided mutagenesis on key residues involved in the proposed type I (R9 and H21) and type II (R17 and H35) PA-binding sites and performed fungal growth inhibition assays using our panel of CpoBD13 mutants Fig. . We also50 of ~6 µM) and CpoBD13 (H21A) (IC50 could not be determined) both showed significant reductions in fungal growth inhibition activity. This pattern in activity was reflected in PI uptake assays with CpoBD13 (H21A) being the least effective at permeabilising C. albicans cell membranes followed by CpoBD13 (R17A)  compared to the wild type and only minor changes in activities of CpoBD13 (R9A) and CpoBD13 (H33A) Fig. , whereas7A) Fig. . In cont7A) Fig. . Results. CpoBD13 (H21A) was the least effective at binding PA at pH 5.5, whereas the remaining histidine mutants showed no significant differences to the wild type.We then examined PA binding of our panel of mutants in liposome pulldown assays Fig. . Both arFig. . CpoBD13To establish if the differences in PA binding are reflected in the lytic activity of the mutants, we again treated PA-enriched liposomes and monitored calcein-release Fig. . The resAs single amino acid substitutions of the PA-binding residues elicited mild changes in the antifungal activity of CpoBD13 (excluding H21A), we generated a range of compound mutations to further investigate the importance of PA interactions on the defensin’s ability to kill fungal cells. In total, five compound mutant defensins were recombinantly expressed to investigate two aspects of the defensin’s activities Fig. , the pH C. albicans  had greater membranolytic activity and was able to permeabilise ~75% of the fungal cells at 50 µM. Furthermore, when the pH was adjusted to pH 7.5, neither mutant showed a significant difference in activity when compared to pH 5.5, indicating that the antifungal activities of the compound histidine mutants were not regulated by the surrounding pH.As single amino acid substitutions had little effect on the pH sensitivity of CpoBD13, we assessed the ability of the double histidine substitution mutants CpoBD13 (H21A/H35A) and CpoBD13 (H21R/H35R) to permeabilise fungal cell membranes at pH 5.5 and 7.5 Fig. . At pH 510. While reptilian defensin genes have been identified from the genomes of species such as the Komodo dragon12, Chinese turtle13 and recently members of the crocodilian family15, the same depth of structural and mechanistic insight has not been obtained in comparison to their human and plant counterparts.The structure–function relationships of human and plant defensins have been well documented. These CHDPs target and destabilise the plasma membranes of a broad range of microbial organisms and, in certain cases, tumourigenic cells by interacting with negatively charged phospholipidsIn this study, we characterised the antifungal activity of the saltwater crocodile β-defensin CpoBD13 and discovered that the ability to bind anionic phospholipids, specifically phosphatidic acid, has been evolutionarily conserved by reptilians. By solving the first three-dimensional crystal structure of a reptilian defensin in complex with PA, we identified that the binding of PA is mediated by key histidine residues that regulate the membranolytic activity of the peptide in a manner dependent on the environmental pH. To our knowledge, this phenomenon has not been observed for any characterised defensin.C. albicans, which is mediated via accumulation at the cell membrane prior to cell lysis  in a pH-dependent manner21. For CpoBD13, this in-built pH-sensitivity could be a mechanism that allows the peptide to be stored or transported in a low-activity state within the crocodile when maintained in a neutral pH to help prevent harm to the host. However, once CpoBD13 reached an acidic pH at the site of an infection (e.g. Candida blastophores favour acidic pH in humans22), the peptide could be activated and clear target pathogens.The antifungal activity of CpoBD13 is regulated by the environmental pH and has optimal activity at acidic pH. Its ability to permeabilise fungal membranes improves as the net charge of the peptide increases. While this is the first defensin determined to be pH-sensitive based on direct histidine-mediated lipid binding, the ability for pH to modulate membranolytic activity has been previously observed23. Our crystal structure of CpoBD13 bound to PA  tag (YPYDVPDYA) was codon-optimised for expression in the methylotrophic yeast Pichia pastoris, synthesised by Bioneer Pacific , subcloned into the pPIC9 vector for recombinant protein expression in P. pastoris, and subsequently purified by cation exchange chromatography, as previously described25. CpoBD13 point mutations  were generated using the QuikChange II Site-Directed Mutagenesis Kit  as per the manufacturer’s instructions. CpoBD13 compound mutants were synthesised by GenScript Biotech  directly into the pPIC9 vector.The open reading frame encoding CpoBD13 was identified from the NCBI nucleotide database as accession XM_019537183.1. The DNA sequence encoding the mature defensin domain of CpoBD13 (nucleotides 142–255), as determined using the web-based software SignalPC. albicans ATCC 10231 cells  were pelleted , washed once in 0.5× potato dextrose broth  and finally resuspended in the same media. Cells were seeded onto a 96-well plate  and treated with an equal volume of varying concentrations of defensin in 0.5× potato dextrose broth. After incubating the samples , the plates were shaken to distribute the cells and growth was determined by performing a 9-well scan (600 nm) using a Spectramax M5e microplate reader . For assays testing defensin salt tolerance, C. albicans cells were instead resuspended in 1x potato dextrose broth and treated with an equal volume of CpoBD13 + NaCl solution at their intended concentrations. Propidium iodide (PI) uptake assays were performed by preparing the cells as per the standard growth inhibition assay however they were instead seeded onto a U-bottom 96-well plate . After incubating the cells with an equal volume of defensin in 0.5× potato dextrose broth at a range of concentrations , PI (diluted in ice-cold PBS) was added to the samples  before analysis by flow cytometry using a BD FACSCanto II with FACSDiva 8.0.1 (BD Biosciences). For PI uptake experiments performed at a specific pH, the same method was followed with the exception that cells were resuspended in 1× potato dextrose broth while defensin titrations were diluted in 40 mM MES buffer at the intended pH. An example PI uptake gating strategy is presented in Supplementary Fig. For fungal growth assays, overnight cultures of 2.Human epithelial cervical cancer , prostate cancer  and histiocytic lymphoma  cells were obtained from the American Type Culture Collection  and cultured in RPMI-1640 medium  supplemented with 5–10% (v/v) foetal bovine serum (FBS), 100 U/mL penicillin and 100 U/mL streptomycin . Adult human dermal fibroblasts  cells were obtained from Lonza  and cultured in Dulbecco’s Modified Eagle Medium (DMEM) (Thermo Fisher Scientific) supplemented with 10% (v/v) FBS, 100 U/mL penicillin and 100 U/mL streptomycin. Human umbilical vein epithelial  cells were obtained from Lonza and cultured in EBM-2 medium supplemented with EGM-2 SingleQuots (Lonza). All cell lines were maintained at 37 °C in a humidified incubator with 5% CO8. For propidium iodide uptake assays in serum-free medium, U937 cells  were washed once in serum-free RPMI-1640, pelleted again (as previous centrifugation) and resuspended in serum-free media. 4×104 cells were seeded and incubated with a range of CpoBD13 concentrations (diluted in serum-free medium) for 30 min at 37°C. PI (diluted in ice-cold PBS) was added to a final concentration of 1 µg/mL before analysis by flow cytometry using a BD FACSCanto II with FACSDiva 8.0.1 (BD Biosciences).Cell viability assays were performed using MTT/MTS as previously describedLyophilised CpoBD13 (2 mg) was resuspended in 900 µL of conjugation buffer  followed by the addition of 0.71 mg 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and 2 mg N-hydroxysuccinimide . After incubating at RT for 15 min, the pH of the reaction was adjusted to between 7–8 by the addition of 20× PBS. BODIPY FL EDA (Thermo Fisher Scientific) was resuspended in dimethylsulfoxide to a concentration of 20 mg/mL before it was subsequently added to the reaction mixture . After incubating the reaction for 150 min, salts and unbound BODIPY were removed by using a PD-10 desalting column  as per the manufacturer’s instructions.2. C. albicans ATCC 10231 cells suspended in 0.5× potato dextrose broth were immobilised onto the surface of glass chamber wells pre-coated with 0.01% poly-L-lysine  and were treated with CpoBD13-BODIPY (20 µM) immediately prior to imaging. For microscopy experiments containing PI, the dye was added to the cell media to give a final concentration of 1 µg/mL.Live cell imaging was performed on a Zeiss LSM 800 confocal microscope using a 63× oil immersion objective at 30 °C in 5% COPIP Strips  were initially incubated in PBS/3% BSA for 60 min. The blocked strips were then incubated with CpoBD13-HA (1 µg/mL) diluted in PBS with 1% BSA for 60 min followed by three 10 min washes with PBS/0.1% Tween-20 at RT. Bound CpoBD13-HA was probed for using rabbit anti-HA tag antibody  diluted to 1:4000 in PBS/1% BSA for 120 min at RT. The PIP Strips were washed before being incubated with HRP-conjugated donkey anti-rabbit Ig  diluted to 1:5000 in PBS/1% BSA for 60 min at RT. Following a final round of washing, antibody reactivity was detected by chemiluminescence using the ECL Prime Western Blotting System (Cytiva) as per the manufacturer’s instructions.5, Thermo Fisher Scientific) in the aforementioned buffer solution. After a 30 min incubation, samples were subjected to SDS-PAGE analysis and colloidal Coomassie staining. Crosslinking experiments with CpoBD13 mutants were performed using the same method however only a single PA concentration (0.46 mM) was assessed.CpoBD13  was incubated with an equivalent volume of 0, 0.092 or 0.46 mM 08:00 phosphatidic acid (PA)  in 20 mM HEPES pH 7.1 for 30 min before the addition of equal parts 20 mM PEGylated bis(sulfosuccinimidyl) suberate (BS(PEG)6. For liposome pulldowns performed at pH 5.5, the same protocol was used with minor variations. The desiccated lipid films were resuspended in 20 mM MES pH 7.4 and were washed in the same buffer during the centrifugation process. After the final wash step, the liposome pellets were resuspended in 20 mM MES pH 5.5 and incubated with CpoBD13 or mutants thereof .Liposomes were prepared using natural chicken egg L-α-phophatidylcholine and L-α-phosphatidic acid dissolved in chloroform (Avanti Polar Lipids), and liposome pulldowns (at pH 7.4) and calcein-encapsulated liposome lysis assays were performed as previously describedSamples were prepared by mixing 1 mg/mL CpoBD13 with 4 mM PA or PC at a 9:1 ratio . For samples of CpoBD13, PA or PC only, protein/lipid was diluted in water to give the same concentration as the CpoBD13 + lipid sample. Samples (10 µL) were allowed to settle onto 400-mesh copper grids before excess liquid was removed with blotting paper. Each sample was negative stained twice with 2% uranyl acetate, allowed to air-dry and imaged using a JEOL JEM-2010 transmission electron microscope . For experiments in reducing conditions, CpoBD13 and PA were mixed in the presence of 100 mM dithiothreitol (DTT) prior to negative staining.2HPO4/KH2PO4, 0.1 M sodium HEPES pH 7.5 using a protein:lipid molar ratio of 1:1.2 at a concentration of 14 mg/mL. Diffraction data were collected on the MX2 beamline at the Australian Synchrotron. All diffraction data were integrated using Dials26 or Xia227 version 3.2.1. and scaled using AIMLESS version 0.7.429. The structure of CpoBD13 was solved by molecular replacement with PHASER30 using the structure of HBD-2 (PDB ID 6CS9)6 as a search model. The structure of CpoBD13:PA was solved by molecular replacement with PHASER30 using the previously determined structure of CpoBD13. Final models were manually built using Coot31 and refined using PHENIX version 1.18.2_387432. All data collection and refinement statistics are summarised in Supplementary Table Crystals of CpoBD13 were grown at 20°C in 0.1 M trisodium citrate pH 5.5, 20% PEG 3000 using protein at a concentration of 20 mg/mL. Crystals of CpoBD13:PA were grown at 20°C in 0.8 M NaAll data are presented as the mean ± SEM of three independent experiments. Where stated, statistical analyses of these experiments (including two-way ANOVA and unpaired t-tests) were performed using Prism 9.1 .Further information on research design is available in the Supplementary InformationDescription of Additional Supplementary FilesSupplementary Movie 1Reporting Summary


The appropriate design of studies is essential for their quality, successful execution, and interpretation. Randomized controlled trials (RCTs) are considered the “gold standard” for intervention studies. However, the most recent large-scale , long-term RCTs involving vitamin D3 did not provide any statistically significant primary results. This may be because they are designed similarly to RCTs of a therapeutic drug but not of a nutritional compound and that only a limited set of parameters per individual were determined. We propose an alternative concept using the segregation of study participants into different groups of responsiveness to vitamin D3 supplementation and in parallel measuring a larger set of genome-wide parameters over multiple time points. This is in accordance with recently developed mechanistic modeling approaches that do not require a large number of study participants, as in the case of statistical modeling of the results of a RCT. Our experience is based on the vitamin D intervention trials VitDmet, VitDbol, and VitDHiD, which allowed us to distinguish the study participants into high, mid, and low vitamin D responders. In particular, investigating the vulnerable group of low vitamin D responders will provide future studies with more conclusive results both on the clinical and molecular benefits of vitamin D3 supplementation. In conclusion, our approach suggests a paradigm shift towards detailed investigations of transcriptome and epigenome-wide parameters of a limited set of individuals, who, due to a longitudinal design, can act as their own controls.Vitamin D intervention studies are designed to evaluate the impact of the micronutrient vitamin D However, over many thousands of years hunter–gatherer populations adapted genetically to reduced UV-B exposure, such as a less active DHCR7 (7-dehydrocholesterol reductase) enzyme [3 [SLC24A5 (solute carrier family 24 member 5) and SLC45A2 of the solute carrier family [3-rich food like fatty fish to their diet [3 became a real vitamin. For example, in England in the 19th century, rickets was a very common disorder in children [Vitamin Dsed skin ,3, the nsed skin . Above a) enzyme . Reducednzyme [3 ,7. In par family  involvedr family . In addieir diet . Althougeir diet ,13, justchildren ,15. Thischildren .3 (25(OH)D3) [3 [3 is considered insufficient [Mycobacterium tuberculosis [The vitamin D status of an individual is defined as the serum concentration of the most stable and abundant vitamin D metabolite, 25-hydroxyvitamin D5(OH)D3) . There iH)D3) [3 . As a reH)D3) [3 . This sufficient , becausefficient , and a lfficient ,23. Whilfficient , multiplfficient  and inflfficient  as well fficient ,29 or thrculosis ,31, stilrculosis , as wellrculosis . Howeverrculosis . To eval3, 1,25-dihydroxyvitamin D3 2D3), which acts as a high-affinity ligand to the transcription factor VDR (vitamin D receptor) [VDR-expressing tissues and cell types [3 intervention studies can be considered as nutrigenomic experiments, in which the action of vitamin D3 and its endogenously produced metabolites are investigated under human in vivo conditions. This had already been demonstrated by studying vitamin D-triggered changes in chromatin accessibility [The physiological effects of vitamin D are mediated by the biologically most active form of vitamin Deceptor) . In thisll types . Thus, all types , (ii) asll types , (iii) mll types , and  are balanced. This clearly distinguishes RCTs from observational studies. However, the design of RCTs requires a larger number of participants. Finally, when the RCTs are finished, they are unblinded and mostly analyzed in comparison of the groups to which the individuals had been assigned, i.e., treatment versus placebo.RCTs aim to measure the effectiveness of interventions or treatments, such as whether vitamin D3 supplementation have been published  with more than 5000 adults over 3.3 years concerning the prevention of cardiovascular events and mortality [3 (1600 or 3200 IU) per day over 5 years for investigation of the primary outcomes of cardiovascular disease and invasive cancer [3 (4000 IU) over 2.5 years, for a possible conversion of prediabetes to type 2 diabetes (T2D) [3 dose of 50 µg (2000 IU) alone or in combination with ω-3 (1 g/d) and a strength-training exercise program over 3 years improves the health conditions of elderly, such as the likelihood of falls [Within the past 6 years, the results of a few large-scale RCTs involving vitamin Dublished . The lard cancer . The ViDortality . In the e cancer . The stues (T2D) . Finallyof falls .3 in serum, i.e., hardly any study participants were vitamin D deficient. This is not representative of the world population, of which some 7% are severely vitamin D deficient and 33% have an insufficient vitamin D status [3 supplementation clearly increased the vitamin D status of the participants to sufficiency. However, primary analysis of the data showed a trend in the expected direction, but did not provide any statistically significant indication that vitamin D3 supplementation, either daily or monthly, was beneficial for the expected clinical outcome of the respective trials, i.e., the studies had null results [The average vitamin D status of a total of 38,054 individuals in these five studies was, at baseline, more than 50 nM 25(OH)DD status . Moreove results .3 supplementation did not improve their clinical status (only 12.7% of participants in VITAL and 9.1% in FIND were vitamin D deficient). In the classical RCT, the entrance criterion into a study should be low vitamin D3 status to observe a stronger effect of supplementation, but for ethical reasons, long-term RCTs with vitamin-D3-deficient individuals as a placebo group (control) cannot be performed. Additionally, for some of the individuals, daily supplementation with only 40 µg (FIND) or 50 µg (VITAL and DO-HEALTH) vitamin D3 may have been insufficient. Furthermore, the RCTs were designed for outcomes such as cancer, cardiovascular disease, and T2D that do not reflect the primary physiological role of vitamin D, which is the control of calcium homeostasis and the modulation of immunity [3 supplementation reduced the risk of autoimmune diseases by 22%, i.e., for a directly immune-related outcome a significant effect could be observed [3 supplementation on cancer mortality [3.There are several explanations for this unexpected result. The main point may be that the study participants were recruited an excessively high basal vitamin D status, i.e., many of them were already vitamin D sufficient and further vitamin Dimmunity . For exaortality , while Vwww.internationalgenome.org, accessed on 5 July 2023) have described the variability of the human genome [“Big biology” projects such as 1000 Genomes , CYP2R1 , CYP24A1 (rs17216707), and GC  contribute to basal serum levels of 25(OH)D3, but each of them only with a small OR [DHCR7 gene, increases the 7-dehydrocholesterol concentrations in the skin, and leads to a more efficient synthesis of vitamin D3 [3. Similarly, the frequency of other SNVs related to genes mediating vitamin D signaling, such as VDR (rs2228570 (known as FokI polymorphism), rs1544410 (Bsm1), rs731236 (Taq1)), and the VDR target genes CD14 (rs2569190) and CARD9  is increased in European populations [3 serum levels [The 20/80% contribution of genetics versus environment/epigenetics also applies to vitamin D status. GWAS indicated that SNVs in the regions of the genes small OR ,55. Moretamin D3 . Today’s3 over 5 months of a Finnish winter , i.e., it follows the treatment protocol of the FIND trial. The study aimed at preventing the onset of type 2 diabetes; blood samples were collected at the beginning and end of the intervention. In contrast, in VitDbol 35 young healthy subjects were exposed only once to a vitamin D3 bolus  and samples were taken at days 0, 1, 2, and 30. Importantly, the analysis of both VitDmet and VitDbol differed from other vitamin D intervention studies by relating the changes of vitamin D-triggered parameters, such as vitamin D target gene expression in PBMCs , which had been isolated at the end and beginning of the study, to the ratio of the vitamin D status at the respective time points  ,59,60,61e points A. Accord3 supplementation. For example, the study BEST-D had a similar three-arm design as VitDmet, also focused on the elderly, and measured the expression of cytokines [3 supplementation [The method of data analysis of these smaller-scale studies is essential for obtaining significant effects of vitamin Dytokines . Howeverentation  2D3). In addition, this study included two different approaches, which were a traditional cohort analysis built on single repeats of 25 individuals and a personalized analysis based on testing a limited number of selected participants in triplicate [50-value of 1,25(OH)2D3 stimulation [The vitamin D intervention study VitDHiD (NCT03537027) followed the VitDbol approach in design, but studied 25 participants on the level of their transcriptome  Table 2Table 2. iplicate . This lemulation . In humaVKORC1 (vitamin K epoxide reductase complex subunit 1) and CYP2C9 [The molecular basis of the vitamin D response index needs to be explored further. In analogy to the anti-coagulant drug warfarin, as the interindividual difference in the response to it is determined by SNVs in the genes d CYP2C9 , the vit3 supplementation, can be used [In general, the transcriptome-wide analysis has an advantage in that, in contrast to the set of 24 vitamin D target genes, which had been selected in the context of the VitDmet study ,59,60,61 be used . This si3 production. High vitamin D responders better tolerate these conditions and should suffer less frequently from autoimmune diseases [3 supplementation doses than suggested by population-based recommendations and guidelines that may serve primarily mid vitamin D responders. However, daily vitamin D3 supplementation should not be higher than 4000 IU (100 µg) in order to prevent overdose in high vitamin D responders. The most appropriate supplementation may be 1 µg (40 IU)/kg body mass to account for obese individuals.A low vitamin D status most likely occurs in the winter season, in particular in the about 15% of the world’s population living above a latitude of 38° N ,72, i.e.diseases , infectidiseases , and/or diseases  because It is possible that due to the evolutionary adaptation of the European populations to changing environmental conditions, such as the northern migration after the end of the ice age, there are more high vitamin D responders in Northern Europe than in Southern Europe. Since populations in Nordic countries have a higher rate of ancestry from Caucasian pastoralists  and Siberian hunter–gatherers than those from the South ,77, inte3 supplementation than mid or high responders, which already may be saturated with a lower vitamin D status. Accordingly, RCTs performed exclusively with accurately adjusted dosage on low vitamin D3 responders would provide more conclusive results. However, ethical considerations do not allow the use of low vitamin D responders as a control group with no or insufficient vitamin D3 supplementation. This prevents the design of classical RCTs with low vitamin D responders as well as studies with vitamin-D-deficient persons. In this respect, a longitudinal design of vitamin D intervention studies, such as in VitDmet, VitDbol, or VitDHiD, where each participant is serving as his/her own control, are more appropriate. Since in these studies each participant is investigated individually, they are also referred to as N = 1 studies  , Wikipat3, for which no clean zero controls exist, long-term RCTs with vitamin-D3-deficient individuals cannot be performed for ethical reasons and alternative study designs, such as N = 1 approaches, may be more appropriate. Finnish studies such as VitDbol and VitDHiD were designed to use a vitamin D3 bolus (3 intervention study in Saudi Arabia [3 bolus should not be used over longer periods in order to prevent hypercalcemia and tissue calcification [3 supplementation is recommended [The most recent large-scale, long-term RCTs involving vitamin D did not provide any significant primary results. This is largely because they were designed similarly to RCTs of therapeutical compounds, i.e., drugs that do not naturally occur in the human body. Thus, for endogenous molecules, such as vitamin DD3 bolus , i.e., ti Arabia ,86. Howefication . Thus, dommended .3 supplementation may serve as a trait that identifies members of the general population who have a significantly higher susceptibility to multiple types of diseases, such as autoimmune diseases, cardiovascular disorders, T2D, and cancer. In contrast, high responsiveness may reflect a high immune resilience, i.e., an appropriate response of the immune system to various health challenges [3 supplementation.A low responsiveness to vitamin Dallenges . In this


Trisomy 18 syndrome (T18) is the second most common autosomal trisomy and has a high risk of fetal loss and stillbirth. Aggressive surgical treatments for the respiratory, cardiac, or digestive systems of patients with T18 were previously futile, while the results of recent studies are controversial. Over the past decade, there have been approximately 300,000 to 400,000 births annually in the Republic of Korea; however, there have been no nationwide studies on T18. This nationwide retrospective cohort study aimed to determine the prevalence of T18 in Korea and its prognosis according to the presence of congenital heart disease and relevant interventions.This study utilized NHIS-registered data between 2008 and 2017. A child was defined as having T18 if the ICD-10 revision code Q91.0–3 was reported. Subgroup analysis was performed for children with congenital heart diseases, and survival rates were compared based on the history of cardiac surgical or catheter interventions. The primary outcomes in this study were the survival rate during the first hospitalization period and the 1-year survival rate.Of the children born between 2008 and 2017, 193 were diagnosed with T18. Of these, 86 died, with a median survival of 127 days. The 1-year survival rate for children with T18 was 63.2%. The survival rate in the first admission of children with T18 who did and did not have congenital heart disease was 58.3% and 94.1%, respectively. Children with heart disease who underwent surgical or catheter intervention had a longer survival time than those who did not.We suggest these data could be used in ante- and postnatal counseling. Ethical concerns about the prolonged survival of children with T18 remain; however, the potential benefits of interventions for congenital heart disease in this population need further study.The online version contains supplementary material available at 10.1186/s12887-023-04056-4. Trisomy 18 syndrome (T18) is the second most common autosomal trisomy and has a high risk of fetal loss and stillbirth. The prevalence in live births is estimated as 1/6,000–1/8,000. However, the actual prevalence may be higher  because of the high risk of fetal death and pregnancy termination after prenatal diagnosis . Recent In contrast, some reports have indicated that the survival rate of children with T18 may increase while receiving active treatment. Data of vital statistics from Japan demonstrated that more surgical interventions provided during 1995–2016 increased the median survival time of children with T18 from 28 to 54 days . A multiIn 2019, the Constitutional Court in the Republic of Korea (Korea) determined the anti-abortion law unconstitutional officially. Until then, abortion due to fetal disease was illegal . The govNHIS data containing demographics, healthcare utilization, and diagnoses based on the International Classification of Diseases, 10th revision (ICD-10), were used in this study. Several studies utilizing the Korean NHIS cohorts have been conducted, and more recently, studies on the long-term outcomes of neonates using the NHIS database have been published –12. ThisA child was defined as having T18 if the ICD-10 codes  were reported during an inpatient admission or visit to outpatient clinics. Follow-up observations of these infants were conducted until December 31, 2018. The type of insurance  and the NHIS premium depending on income levels were employed as proxies for measures of income level. The lowest income category was designated as those receiving medical aid. In addition, the NHIS group was split into four groups: category 1, < 25% premium; category 2, 25–50% premium; category 3, 50–75% premium; and category 4, > 25% premium. We reviewed and ranked all ICD-10 codes associated with congenital malformation, deformation, and chromosomal abnormalities (Q codes). A child was defined as having a history of congenital heart disease (CHD) if diagnosed with Q20–26. Heart anomalies that usually regress spontaneously, such as atrial septal defect (ASD) (Q21.1) and patent ductus arteriosus (PDA) (Q25.0), were excluded from CHD codes. Among CHDs, the annual number of children who underwent surgical or catheter intervention (intervention) for CHDs was counted using health insurance claim codes (eTable 1 in Supplement 1). Additionally, the number of children with T18 who had tracheotomy or gastrostomy was counted. The mortality rate was analyzed in two categories. We examined mortality during the first hospitalization period and before 1 year after birth.The study employed Pearson’s chi-square analysis to compare the mortality rates between groups according to the history of cardiac intervention. Kaplan-Meier survival analysis and log-rank tests were utilized to describe long-term survival and compare groups, respectively. In this study, we used a two-sided test with a significance level of p < 0.05 to determine statistical significance. All analyses were performed using SAS .The NHIS database included 193 children diagnosed with T18 who were born between 2008 and 2017. Annually, 12–25 children are diagnosed with T18  ’, which includes ASD and ventricular septal defect; ‘congenital malformations of great arteries (Q25)’, which subsume PDA; ‘congenital deformities of feet (Q66)’; and ‘other congenital malformations of the brain (Q04)’ (eTable 2 in Supplement 1). Except for PDA and ASD, the ventricular septal defect was the most common CHD, followed by coarctation of the aorta and double outflow of the right ventricle (eTable 3 in Supplement 1). Consequently, 108 (56.0%) children with T18 were diagnosed with CHDs, and 47 (43.5%) received cardiac intervention. In 2008 and 2009, few children with T18 underwent heart intervention; however, 23.1–77.8% of children with T18 and CHD underwent intervention from 2010. Only one or two infants underwent a tracheotomy yearly; however, approximately more infants underwent surgery in 2014 and 2017 .P = 0.028) (Table P < 0.001)  Table , with si01) Fig. .This nationwide population-based study was the largest on intervention and outcomes of children with T18 in Korea. The median survival time of mortality cases was 127 days and the 1-year survival rate was 63.2%, with no evident change in the survival rate for 10 years. Among 108 children with CHD, 47 (43.5%) underwent cardiac intervention, and their survival days were longer than those who did not undergo the intervention.In this study, 193 children were diagnosed with T18 over 10 years , a lower number than in previous studies conducted in other countries. Approximately 1.5 per 10,000 live births in the US were affected by T18, and multinational research reported that the mean prevalence of T18 among live births was 1.07  per 10,000 births , 6. The The median survival time (25–75 percentiles) of mortality cases was 127  days in our study, which was longer than those in previous studies with similar study periods. A recent study from Japan has reported that the median survival time of children with T18 who were born between 2006 and 2016 was 54 (1–196) days . In anotOur study included 108 children with T18 and CHD. In previous studies, there has been debate about the association between CHD and the survival of T18 . HoweverSevere developmental delay, long-term dependence on medical equipment, and survival have been considered in deciding on a treatment policy for T18 patients. However, several studies on the quality of life of children with T18 have further indicated that considering the family’s perspective and knowledge of natural history when formulating policies for T18 treatment is crucial. Parents of patients with T18 or trisomy 13 syndrome patients reported that their child was happy and enriched their family despite their children’s severe conditions . In anotThis study had some limitations. First, in this study, the observation period varied from 1 year to 11 years due to the children’s different birth years, and ended in December 2018. Although we attempted to mitigate this issue by using a survival curve, there were still limitations to this approach. We acknowledge the limitations of our analysis due to the absence of information on the number of patients at risk at each time point and censoring marks. We had access to this information at the time of analysis, but unfortunately overlooked it and are now unable to retrieve the data. Thus, our presented survival curve may not provide a comprehensive view of the survival outcomes, and readers should interpret our results with caution. Second, we did not have patient information on T18 mosaicism. Patients with T18 mosaicism revealed an extremely variable phenotype; they occupy a small portion of the disease group and may not affect the study’s result . In addiIn this study, fewer children with T18 were reported in the NHIS database in Korea than in other countries; however, many of them received active treatments and had longer survival rates. Recently, advance care planning has been implemented, and the laws regarding abortion have been amended in Korea. Due to these social and legal changes, more ante- and postnatal consultation on T18 treatment are expected, and patient-centered care will be more warranted. Therefore, we expect these data to help determine the disease prognosis and find the best interests for children with T18.Below is the link to the electronic supplementary material.Supplementary Material 1