bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Protocol for Magnesium Electrochemistry
Authors: Masse Robert C , Cao Guozhong
Published: February 2020

Magnesium batteries are a compelling alternative to lithium-ion batteries on the basis of safety, resource abundance, and energy density. Yet until recently magnesium battery research received little attention, and progress remains slow. The two main hurdles have been the poor performance of positive electrode materials and the dearth of magnesium electrolytes with which to study them.

This is attributable to the much more complicated electrochemistry of magnesium relative to well-established lithium-ion battery studies. Well documented examples include the passivation of magnesium metal[1], corrosion of current collectors[2], and low voltage stability of magnesium electrolytes[3]. Nevertheless, a critical look at the literature reveals that many magnesium studies are conducted using experimental designs that are either dubious or unlikely to yield encouraging results[4].

To address these discrepancies, we show that appropriate electrochemical design choices are crucial to the success of magnesium experiments. This study analyzes how different electrolytes, current collectors, and electrode materials work with (or against) each other. This work is intended to provide a platform for the search for high energy magnesium battery electrode materials.

References

[1] Z. Lu, A. Schechter, M. Moshkovich, D. Aurbach, On the electrochemical behavior of magnesium electrodes in polar aprotic electrolyte solutions, J. Electroanal. Chem. 466 (1999) 203–217. doi:10.1016/S0022-0728(99)00146-1.

[2] D. Lv, T. Xu, P. Saha, M.K. Datta, M.L. Gordin, A. Manivannan, et al., A Scientific Study of Current Collectors for Mg Batteries in Mg(AlCl2EtBu)2/THF Electrolyte, J. Electrochem. Soc. 160 (2012) A351–A355. doi:10.1149/2.085302jes.

[3] J. Muldoon, C.B. Bucur, A.G. Oliver, J. Zajicek, G.D. Allred, W.C. Boggess, Corrosion of magnesium electrolytes: chlorides – the culprit, Energy Environ. Sci. 6 (2013) 482. doi:10.1039/c2ee23686a.

[4] R.C. Massé, E. Uchaker, G. Cao, Beyond Li-ion: electrode materials for sodium- and magnesium-ion batteries, Sci. China Mater. 58 (2015) 715–766. doi:10.1007/s40843-015-0084-8.
Current Redistribution and Uneven Heat Generation in a Lithium-Ion Battery Pack with Cells of Initial Performance Difference
Authors: DAN Dan , Li Zhe , Zhang Yangjun
Published: February 2020

Lithium-ion battery is one of the most promising candidate for the energy storage system in the automobile industry. In electric vehicles, cells are connected with each other closely due to space constraints, where thermal problem becomes significant during the system operation. Among all parameters, the initial cell inconsistency plays an important role in the changing rules of pack thermal performance. This paper seeks to gain a better understanding of current load and uneven heat redistribution for a lithium-ion battery pack consisted of cells with unequal initial parameter.

This study carries out a multi-physics coupling model for a battery pack consisted of cells with different initial resistance and capacity. A pseudo 2D electro-chemical model coupled with a lumped thermal model is used to describe each cell inside the pack. Based on this cell model, a coupled thermal-electrochemical model for a battery pack is built, which is able to predict the current load distribution and uneven heat generation during the charge and discharge procedure.

Using the coupled electrochemical-thermal model, cell initial parameters’ impact on pack performance was studied, including resistance and capacity inconsistency. Different cell numbers and connection pattern (parallel/series) were also selected to explore the changing mechanisms in load non-uniformity and heat performance.
Nafe(HPO4)2: A New Polyanionic Cathode Material for Lithium and Sodium-Ion Batteries
Authors: Sandineni Prashanth , Choudhury Amitava
Published: February 2020

There is a continuous quest for a low-cost, efficient and environmentally benign cathode materials for Li ion batteries. Several polyanionic compounds in the family of phosphates and sulfates have already been touted as excellent cathode materials, for example, olivine-type LiFePO4 and Triplite-LiFeFSO4. Herein, we are reporting a new phosphate compound, NaFe(HPO4)2, synthesized through a low-temperature hydrothermal route. The structure has been solved using single-crystal X-ray diffraction, showing a 3D structure built up of corner sharing FeO6 octahedra and PO4 tetarhedra yielding channels along C-axis. The Na ions occupy half of those channels leaving other half empty. Hence, further reductive insertion of alkali ions into the structure was hypothesized. The theoretical capacity of the compound based on one Li insertion is 98.97 mAhg-1, of which 60% of the capacity can be practically achieved in both Li- and Na-ion batteries with an average voltage of 3.0 and 2.80 V, respectively. Further ion-exchange of sodium with lithium was successfully carried out and the ion-exchanged compound, presumably LiFe(HPO4)2, showed better achievable capacity, up to 70% of theoretical capacity in a Li-ion battery with an average voltage of 3.0 V. The presentation will cover synthesis, structure, thermal and spectroscopic analysis of the samples and their detail electrochemical properties.

Figure 1
The Response and Limits of Fast Discharge and Charge Rates of Electrodeposited V2O5 Inverse Opal Networks in Lithium Batteries
Authors: O'Hanlon Sally , O'Dwyer Colm
Published: February 2020

Structurally stable electrodeposited vanadium pentoxide inverse opal networks on FTO-coated glass are electrochemically tested as a function of C-Rate (discharging and charging) in this study. Recent applications of IOs in electrochemical energy storage have proven that their open-worked structure promotes more stable Li-ion intercalation during cycling(1-3), exhibit improved rate capability due to increased surface area and decreased path lengths for Li+ insertion,(4-7). Rate limitations associated with standard Li-ion batteries can be improved in principle due to shorter diffusion lengths in the 3D architecture(8, 9), particularly important for charging in full cells. V2O5 has been widely investigated(10) as a cathode material for Li-ion batteries due to its high theoretical specific capacity and is useful for reversible Li-ion insertion and removal due to its mixed valance and layered structure.(11) The difference in open-topped versus overfilled (closed top) 3D inverse opal macroporous V2O5 networks, due to electrodeposition growth time, is examined by galvanostatic cycling, and both 3D structure are examined at C-rates in the range 0.5 – 30 C. Electrochemical analysis demonstrates how lithium phase changes increasing C-rate in both open and overfilled network cases, with capacity values investigated after 25 charge/discharge cycles. Raman scattering and X-ray diffraction is used to investigate the change in structure and phase in each case at each C-rate, along with SEM images to visual investigate the effect of C-rate on the V2O5 inverse opal networks.

References

1. E. Armstrong and C. O'Dwyer, J. Mater. Chem. C, 3, 6109 (2015).

2. Y. Zhao, X. Li, J. Liu, C. Wang, Y. Zhao and G. Yue, ACS Appl. Mater. Interfaces (2016).

3. E. Armstrong, D. McNulty, H. Geaney and C. O’Dwyer, ACS Appl. Mater. Interfaces (2015).

4. M. Osiak, H. Geaney, E. Armstrong and C. O'Dwyer, J. Mater. Chem. A, 2, 9433 (2014).

5. F. Zhang, Y. Tang, H. Liu, H. Ji, C. Jiang, J. Zhang, X. Zhang and C.-S. Lee, ACS Appl. Mater. Interfaces (2016).

6. Y. Liang, L. Chen, L. Cai, H. Liu, R. Fu, M. Zhang and D. Wu, Chem. Commun (2016).

7. F. Li, M. Zeng, J. Li, X. Tong and H. Xu, RSC Adv. (2016).

8. D. R. Rolison, J. W. Long, J. C. Lytle, A. E. Fischer, C. P. Rhodes, T. M. McEvoy, M. E. Bourg and A. M. Lubers, Chem. Soc. Rev, 38, 226 (2009).

9. C. O'Dwyer, Adv. Mater.
28, 5681 (2016).

10. D. McNulty, D. N. Buckley and C. O'Dwyer, J. Power Sources, 267, 831 (2014).

11. E. Armstrong, M. O'Sullivan, J. O'Connell, J. D. Holmes and C. O'Dwyer, J. Electrochem. Soc, 162, D605 (2015).
Studies on Complex Electrolytes for Divalent Batteries
Authors: Merrill Laura C. , Upadhyay Sunil , Schaefer Jennifer L.
Published: February 2020

Lithium-ion batteries have dominated the rechargeable battery market since the 1990s when they were first commercialized. Many advanced technologies (portable devices, electric vehicles) are limited by the performance of commercialized lithium-ion batteries. Furthermore, future resource availability is undetermined. Magnesium serves as a viable anode for post lithium-ion batteries due to its high volumetric charge capacity and widespread abundance. Magnesium batteries are under investigation for future applications in electric vehicles due to their potential to have high energy density and reduced cost. The electrolyte is identified as a limiting factor in magnesium batteries, as many analogous electrolytes to lithium-ion batteries can passivate the magnesium metal surface preventing rechargeability. Thus, many new electrolytes are under investigation in the field. Here we report the effect of the anion electronic structure and solvent on the performance of magnesium bis(disilazide) based electrolytes. This includes the electrolytes’ stability window, ability to electrochemically deposit magnesium, and conductivity.
Hydrothermal Assembly of Submicron Si Recovered from Si Waste with Graphene and Carbon for Scalable Lithium Battery Anodes
Authors: Lee Byeongyong , Liu Tianyuan , Jang Hankwon , Jang Hee Dong , Lee Seung Woo
Published: February 2020

Despite its high theoretical capacity of 4200 mAh/g, the application of Si has been limited for lithium-ion battery (LIB) anode. This is because Si suffers from large volume change during charge and discharge processes, resulting in poor cycling stability. To address this issue, researchers have proposed Si nanoparticles, especially less than 150nm, and their composite with various carbonaceous materials for LIB anodes. Although these electrodes have demonstrated improved cycling stability, it is still far-off from fulfillment for practical LIB anodes. To date, the Si nanoparticles have been synthesized costly processes, such as CVD and magnesiothermic reduction. In addition, their composites were prepared through complex fabrication process requiring toxic chemicals such as silane (SiH4) and hydrofluoric acid (HF). Therefore, it is highly desirable to develop cost-effective Si source and scalable fabrication process for the composite. Today, a large amount of Si is being consumed in photovoltaic and semiconductor industries. Surprisingly, more than 40% of the Si is being dumped as kerf-loss generated during the slicing of high purity Si ingots into Si wafers. The Si waste consists of Si, SiC, and the other impurities. We simply recovered Si and SiC through mild centrifugation using the differences of their specific gravities. The recovered Si particles were slightly ground to homogenize size distributions, resulting in submicron Si. The recovered submicron Si particles were coated with graphene and carbon through a hydrothermal one-pot process, yielding submicron Si@C/Graphene. The submicron Si@C/Gr electrode delivered a reversible capacity of 1192 mAh/g at 100th cycle, showing 84% of initial capacity. This composite electrode assembled from cost-effective Si source can provide cost-effective and high-performance anode materials for the next-generation LIBs.
First-Principles Calculation of Li-GIC Compounds: Van-Der Waals Interaction DFT Calculation
Authors: Yamamoto Masahiro
Published: February 2020

The graphite intercalation compounds(GIC) of lithium is commercially used in lithium ion battery (LIB), then a lot of the experimental and theoretical works on GIC have been reported from the invention of LIB. In our previous study[1] we have shown that first-principles calculation based on the local density approximation(LDA) of Ceperley-Alder(CA) type give us some physic-chemical properties, because the LDA-CA calculation accidentally give us the stable interlayer distance between the graphite layers. The interaction between the layers is believed to be van der Waals (vdW) interaction and this interaction comes from the dynamic properties. In 2004 Dion et al. proposed the approximated method that include the vdW interaction in the density functional framework and some people have shown that the their method works! In this study we have used the vdW-DF2 functional[2] in the VASP code[3] for vdW DFT calculation and compare the results without vdW contribution. The energetics and structure of graphite and LiC6 are in good agreement with the results by Wang et al.[4] The have shown that energetics and structures for Li, K, Na GIC are in good agreement with the experimental results. In our study the energy barriers of the diffusion for lithium ion in LIC6 GIC have been calculated. The energy barrier in the parallel direction of the grapheme plane is 0.3 eV per Li ion without vdW interaction, which is in good agreement with out previous calculation[1]. In the vdW-DF2 calculation the energy barrier is increased up to 0.8 eV, the origin of which may be the attractive character of the vdW interaction between the Li and C. If we expand the C-C interplane distance up to 1 nm which corresponds to the distance between the GIC that contains the solvated intercalants, we have found that the calculated energy barrier in plane direction can be neglected.

The dependence of the interlayer distance and the charged state on the diffusion barrier is now evaluating and will be presented.

References [1] M. Yamamoto and H. Imamura, Tanso, 2004 No.212 81-90. [2] K. Lee et al. Phys. Rev. B, 2010, 82 08101 [3] G. Kresse et al. Phys. Rev. B, 1993, 47, 558-561, J. Comput. Mater. Sci. 1996, 6, 15-50. [4] Z. Wang et al. Rsc. Adv. 2014, 4, 4069-4079.
Electropolymerization and Electrochemical Performance of Nickel Schiff Base Complexes on Reduced Graphene Oxide(RGO) Support for Supercapacitors
Authors: Deng Fuhai , Li Xinping , Wang YuDong , Li Jianling
Published: February 2020

Supercapacitors have a high power capability and relatively large energy density compared to the conventional capacitors. Conducting polymers have been shown as promising electrode materials because of their high conductivity and fast redox activity. N,N_-ethylenebis(salicylideneaminato) nickel(II), (Ni(salen)), which is the archetype of Schiff base metal complexes, was easily synthesized onto the surface of reduced graphene oxide(RGO) by the route of linear potential sweep. Growth parameters such as the apparent surface coverage and the doping level were investigated to confirm the effects of supports on the Ni(salen) polymerization.SEM, TEM, Raman, and XPS analyses show that the poly(Ni(salen)/RGO composite prepared from this approach,at the same time it exhibited an excellent electrocapacitive performance with a high specific capacitance over 260 F g-1

Fig.1 (a) Polymerization Q varies with polymerization time at different voltages ; (b) GCD curves of MWCNTs and the composites at a current density of 1.0 mA cm2 under the voltage range of 0 V to 1.2 V.

Reference

1 Kim, M., Lee, C., & Jang, J. (2014). Fabrication of Highly Flexible, Scalable, and High‐Performance Supercapacitors Using Polyaniline/Reduced Graphene Oxide Film with Enhanced Electrical Conductivity and Crystallinity.Advanced Functional Materials, 24(17), 2489-2499.

2. Salanne, M., Rotenberg, B., Naoi, K., Kaneko, K., Taberna, P. L., Grey, C. P., ... & Simon, P. (2016). Efficient storage mechanisms for building better supercapacitors. Nature Energy, 1, 16070.

Acknowledgement

This work is financially supported by the National Natural Science Foundation of China (No. 51372021).

Figure 1
DFT Simulation of Edge Halogenated Graphene Nanosheets As an ORR Catalyst in Fuel Cells
Authors: Rodriguez Roberto , Humphrey Nicholas , Arias Gabriel , Goddard William A , Yu Ted H.
Published: February 2020

Edge halogenated graphene-nanosheets1have recently been discovered to be a low cost Oxygen Reduction Reaction (ORR) catalysts for alkaline fuel cells. Better understanding of ORR on these catalysts is needed to understand:

i) why these doped catalysts form water in the preferred 4e-ORR mechanism over the peroxide formation found in undoped graphene.

ii) how to improve these catalysts, so that ORR can occur in the preferred acidic environment.

We used the PBE flavor density functional theory (DFT) with the SeqQUEST code2to calculate the binding energies, onset potential, and reaction barriers for ORR using either bromine, chlorine or iodine as the hetero-atom dopants on edge halogenated graphene-nanosheets. We examined both the zig-zag and armchair edges and find that the ORR intermediates bind to the zig-zag edges more strongly than the armchair. We find that the ORR intermediate species HOO does not bind to the basal plane. Thus, the ORR occurs on the graphene edges and not on the basal plane surface. We also find that the halide doped graphene zig-zag and armchair edges lead to a skewed geometry due to nonbonded interactions of the halogen with each other on the adjacent edge sites.

Although the ORR intermediate species bind more strongly on the zigzag edges, our results predict that ORR occurs in the armchair edges based on the predicted onset potential calculation that agree well with experiments (Cl: 0.95 V, Br: 0.70 V, I: 0.72 V). We used nudged elastic band (NEB) calculations in conjunction with the CANDLE water solvation method3 to predict the potential dependent barriers4of the ORR.

The dissociation of O2 in the second step of the ORR indicates that halogen doped graphene favor the 4e- pathway. In addition, the barrier to form –OH is much lower on the halide graphene edges than undoped graphene. Based on the calculated barriers, we conclude that iodine-doped graphene has the lowest thresholds water formation (0.56 eV at 0.72 V), which we find to be the rate determine step (RDS). This is in agreement with ORR activity of experimental results indicating iodine doped graphene performs better than bromine-doped, chlorine-doped, and undoped1.

References:

1. I. Y. Jeon, H. J. Choi, M. Choi, J. M. Seo, S. M. Jung, M. J. Kim, S. Zhang, L. Zhang, X. Zhenhai, L. Dai, N. Park and J. B. Baek, Scientific Reports 3(1810), 1-7 (2013).

2. P. Schultz, (SEQQUEST, Sandia National Laboratory).

3. R. Sundararaman and W. A. Goddard, J Chem Phys 142(6), 064107 (2015).

4. H. Xiao, T. Cheng, W. A. Goddard and R. Sundararaman, J Am Chem Soc 138 (2), 483-486 (2016).

Figure 1
Controlled Addition of Carbon Nanotube Defects and Their Role in Limiting Solar Cell Performance
Authors: Wang Jialiang , Shea Matthew J , Arnold Michael S.
Published: February 2020

Semiconducting single-walled carbon nanotubes (s-SWCNTs) have attracted significant attention as a photoactive component in thin film photovoltaics due to their strong absorptivity and high charge mobility. However, the external quantum efficiency (EQE) of s-SWCNT/C60 heterojunction solar cells is limited by poor exciton diffusion to the heterointerface. Exciton diffusion is believed to be strongly dependent on the length between defects, which quench excitons. Here, we systematically study the influence of defects on s-SWCNT/C60 planar heterojunction photovoltaic devices. We use covalent sidewall functionalization via diazonium chemistry to introduce sp3
defects to the s-SWCNTs at varying concentrations. We generate a defect-adding model to describe the position of defects on the surface of the nanotube, and use it to successfully reproduce the time-resolved exciton decay rate measured with transient absorption spectroscopy. We fabricate s-SWCNT/C60 heterojunction photovoltaic cells and characterize the EQE as a function of defect concentration. We develop a diffusion limited contact quenching Monte Carlo model to reproduce the EQE trends we observe. The model allows us to predict the behavior of theoretical s-SWCNT devices with varying length distribution and defect concentration, toward the limit of long length and zero defects. This work guides the field of nanotube photovoltaics and illuminates the promise and limitations of s-SWCNT solar cell devices.
Trap-Limited Recombination and Energy Offset at the Carbon Nanotube – C60 Interface
Authors: Shea Matthew J , Wang Jialiang , Arnold Michael S.
Published: February 2020

We study photophysics and free carrier recombination in (7,5) semiconducting single walled carbon nanotube (s-SWCNT)/C60 fullerene heterojunction diodes over the temperature range 4.5-300 K. We characterize the temperature dependence of the magnitude and spectral peak position of the external quantum efficiency. Appling the Marcus theory description of energy transfer at the interface, we estimate that the reorganization energy and change in Gibbs free energy are relatively equal in magnitude, and predict the high exciton dissociation rate at the s-SWCNT/C60 heterojunction to be relatively resistant to changes in temperature. We show that the current-voltage characteristics in forward bias at all temperatures are best fit to a two-diode model in which traps dictate recombination at the heterointerface. From the diode ideality factor, we calculate the trap depth for holes in (7,5) s-SWCNT films to be 150 meV. We measure the temperature dependence of the open-circuit voltage, short-circuit current density, and fill factor of the devices. Open-circuit voltage strongly depends on temperature, rising to a maximum of 0.82 V at 20 K. Meanwhile, fill factor decreases precipitously below 150 K to a fluence-independent value of 28%. We are able to verify our two-diode model by successfully recreating the temperature and fluence dependence of the open-circuit voltage, and suggest that decreasing fill factor is consistent with a temperature-dependent polaron pair recombination rate at the heterointerface. Finally, we calculate the interfacial energy gap of the s-SWCNT/C60 heterojunction using two methods and find agreement, estimating 0.90 eV by examining the current-voltage characteristics in the dark and 0.86 eV by extrapolating the open-circuit voltage to its 0 K value. These insights provide a greater understanding of the processes that take place at the heterointerface of s-SWCNT/C60 solar cells, guiding further research to improve the efficiency of these devices.
Structural Identification of 11 of the 19 Isomers of the Opv Acceptor Bispcbm Via
13c NMR and UV-Vis Absorption Spectroscopy, and Cyclic Voltammetry, Coupled with DFT Simulations
Authors: Liu Tong , Misquitta Alston J. , Abrahams Isaac , Dennis John
Published: February 2020

The as-produced isomer mixture of the organic photovoltaic acceptor material bisPCBM has recently been purified into 19 components by peak-recycling HPLC and their frontier orbitals have been characterised by UV-Vis absorption spectroscopy and cyclic voltammetry. OPV devices based on the purified isomers may now be made, but before meaningful conclusions can be made about why some isomers are better that others in these devices, we mush first know which particular isomer is used in which OPV device. Here we present the structural identification of more than half (11) of the 19 isomers by 13C NMR and UV-Vis spectroscopy.

Via UV-Vis spectroscopy the 19 isomers of bisPCBM were classified into 7 different groups, with each group containing 2 or 3 members. Each of the 7 groups corresponds to 1 of the 7 bond types identified by Hirsch (trans-1, trans-2, trans-3, trans-4, e, cis-3, cis-2). By examining the molecular structure of each of the 19 isomers, we conclude that 11 isomers have C1 symmetry, 3 isomers have Cs symmetry, 3 have C2 symmetry, 1 has C2h symmetry and 1 has C2v symmetry; and we have confirmed this prediction experimentally by 13C NMR spectroscopy. The two high-symmetry isomers, C2h and C2v, which correspond to the two polar isomers (where the two addends bridge the 1,9 and 52,60 bond of C60with the two addends having opposing relative orientations) correspond to the first and third HPLC fractions by retention time, respectively.

Unfortunately, the other isomers cannot be identified from the NMR spectra alone. However, as the UV-Vis spectra and 7 groups identified above reduce the uncertainty to no more than 3 isomers, when coupled with the symmetry identified from NMR spectra, some of the isomers may be confidently identified. For example, the 13th HPLC fraction belongs to the cis-2 group which contains one C
s and two C
1 isomers. The NMR spectra shows that this 13th fraction is the C
s isomer, which involves the 32,33 bond of C60. By this method, the other C
s and C
2isomers were also unambiguously confirmed.

The remaining unidentified isomers all have C
1 symmetry and cannot be further identified by this method. For these isomers, the HOMOs and HOMO-LUMO gaps were calculated by DFT and TD-DFT methods. By comparing the experimental and calculated results, some, but not all, the C
1 isomers were tentatively identified with reasonable confidence. For the remaining 8 C1 isomers the DFT calculations were not able to adequately distinguish, so the identification of these isomers will have to wait for single crystal analysis. A full description of the identification of the isomers will be presented in the meeting.
Purification and Frontier Orbital Characterisation of 19 Purified Isomers of the Opv Acceptor Bis[60]PCBM
Authors: Dennis John , Shi Wenda , Hou Xueyan , Liu Tong
Published: February 2020

The as-produced isomer mixture of the organic photovoltaic device acceptor material bis-[60]PCBM has been purified into its constituents by peak-recycling HPLC, and those individual isomers were characterised by UV-Vis absorption spectroscopy and cyclic voltammetry.

A total of 19 isomers (from a potential total of 21isomers) were purified from the mixture to a standard exceeding 99.5% with respect to other isomers. Three different columns, silica, 5PYE and 5PBB, were used and tried on each isomer to achieve the highest purification efficiency. The UV-Vis spectra and cyclic voltammograms demonstrate that each of the isomers exhibit different electronic properties. Their HOMO, LUMO and HOMO-LUMO gaps range from, -5.673 to -5.402 eV, from -3.901 to -3.729 eV, and from 1.664 to 1.883 eV, respectively.

Based on comparisons with known UV-vis absorption spectra of analogous materials we conclude that there is correlation between HPLC retention time and the relative positions of the addends; in that generally the closer the addends are to each other the longer the retention time of the isomer, and vice versa. These comparisons have enables us to tentatively, assign each of the isomers to one of the 8 bond types identified by Hirsch and co-workers1,2 (Trans1, Trans2, Trans3, Trans4, equatorial, Cis3, Cis2 and Cis1), such that the identity of the isomers is reduced to being one of only 2 or 3 isomers.

The LUMO levels of the majority of the isomers are above that of the isomer mixture, and hence, OPV devices based on each of those isomers are predicted to have a V
OC higher than that of present devices based on the mixture (with the most promising isomer being 94 meV above that of the mixture and 188 meV above that of [60]PCBM).

Furthermore, with the removal of energetic and morphological disorder associated with the normal mixture of bis-[60]PCBM isomers, it is also predicted that OPV devices based on all of the isomers will have better charge carrier transport properties, and thereby potentially higher currents, than those based on the mixture.

Preliminary analysis of an unoptimized P3HT/bisPCBM device based on the isomer with the highest LUMO indicates an open circuit voltage that is 210 meV above that obtained from the PCBM-based analogous, which is very significant given that the target voltage for OPVs is about 1 V. In addition, time-of-flight conductivity measurements indicate that electron carrier mobility for this isomer is similar to that of PCBM. Optimisation of a is underway and in addition to the abovementioned purification and frontier orbital the findings, the results of the performance of optimised devices will be presented at the meeting.
(Invited) Organic Polymers for Thermoelectric Energy Conversion
Authors: Chabinyc Michael
Published: February 2020

Semiconducting polymers have been proposed as potential materials for thermoelectric devices. While there have been significant advances in designing polymers for applications such as solar cells and thin film transistors, significantly less is understood about how to control their thermoelectric properties. The performance of thermoelectric materials is determined by their electrical conductivity, thermopower and thermal conductivity. Each of these properties is related to the carrier concentration in semiconducting materials and their electronic density of states. The electronic density of states is strongly modified by processing methods used to introduce dopants making it difficult to predict their electrical properties. We will discuss our efforts to understand how the electrical conductivity and thermopower of semiconducting polymers are interrelated using model polymer systems including poly(3-hexylthiophene) and a thienothiophene-basedpolymers, PBTTT. We find that changes in processing conditions can increase the electrical conductivity by >50x at the same apparent carrier concentration, while causing smaller changes in the thermopower. The increase in performance can be understood by the nanoscale connectivity between ordered domains and quantitated using synchrotron-based X-ray scattering methods. We will also present temperature-dependent transport measurements that further help to understand changes in performance. Prospects for the ultimate performance of polymer thermoelectrics will be discussed.
(Invited) Low Temperature Thermoelectric Power Factor from Completely Organic Thin Films Enabled By Carbon Nanostructures
Authors: Grunlan Jaime , Cho Chungyeon , Yu Choongho
Published: February 2020

In an effort to create a paintable/printable thermoelectric material, comprised exclusively of organic components, polyaniline (PANi), graphene, and double-walled carbon nanotubes (DWNT) were alternately deposited from aqueous solutions using the layer-by-layer assembly technique. Graphene and DWNT are stabilized with an intrinsically conductive polymer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). A 1 µm thick film, composed of 80 PANi/graphene-PEDOT:PSS/PANi/DWNT-PEDOT:PSS quadlayers (QL) exhibits electrical conductivity (σ) of 1.88 X 105 S/m and a Seebeck coefficient (S) of 120 µV/K, producing a thermoelectric power factor (S
2∙σ) of 2710 µW/(m∙K2). This is the highest value ever reported for a completely organic material measured at room temperature. Furthermore, this performance matches or exceeds that of commercial bismuth telluride. These outstanding properties are attributed to the highly ordered structure in the multilayer assembly. The thermoelectric power output increased with the number of cycles deposited, yielding 8.5 nW at 80 QL for ΔT = 5.6 K. A simple thermoelectric generator was prepared with selectively-patterned, fabric-based system. The electric voltage generated by each TE device increased in a linear relationship with both ΔT and the number of TE legs, producing ~ 5 mV with just five legs and a ΔT of 9.5 K. This unique TE coating system is water-based and uses only organic components. For the first time, there is a real opportunity to harness waste heat from unconventional sources, such as body heat to power devices in an environmentally-benign way.

Figure 1
An Impedance Study on Porous Carbon/Lithium Titanate Composites for Li-Ion Battery
Authors: Deng Zhaofeng , Ho Ching-Kit , Li Chi-Ying Vanessa , Chan Kwong-Yu
Published: February 2020

The electrode structure affects the charge-transfer process, electronic conduction, mass transport within pores, and therefore electrochemical performance of batteries 1. In this study, a hierarchical carbon network with hollow core and mesoporous shell (HCMS) 2,3 and activated carbon (AC) are employed as supports for Li4Ti5O12 (LTO) anode material. LTO/HCMS composite shows higher capacity than LTO/AC composite under high-rate and low-temperature conditions. In order to study the performance-structure relationship, electrochemical impedance spectroscopy (EIS) technique with transmission line model (TLM), together with material characterization, are utilized to study the electronic conduction process, mass transport within the pores and the charge-transfer process of LTO/C composites and carbon supports.

Fig. 1 TEM images of (a) HCMS and (b) AC carbon supports; (c) Nyquist plots (symbol), and plots (line) fitted with equivalent circuit model for symmetric HCMS/HCMS (○, solid line) and AC/AC (□, broken line) coin-cells in 1M LiPF6 in EC/EMC/DMC (1:1:1).

References

[1] N. Ogihara, S. Kawauchi, C. Okuda, Y. Itou, Y. Takeuchi, and Y. Ukyo, J. Electrochem. Soc., 159, A1034 (2012)

[2] F. Li, M. Morris, and K.Y. Chan, J. Mater. Chem., 21, 8880 (2011)

[3] C. Yang, C.Y.V. Li, F. Li, and K.Y. Chan, J. Electrochem. Soc., 160, H271 (2013)

Acknowledgements

This project is financially supported by Innovation and Technology Commission, Hong Kong (Project No.: ITS/076/11), HKU Seed Fund for Basic Research (Project No.: 201605159011), and University Development Fund for Clean Energy and Environment.

Figure 1
Preparation of Porous Graphene Via Covalent Functionalization for Efficient Electrocatalysis in Oxygen Reduction
Authors: Ahmed Mohammad Shamsuddin , Kim young-Bae
Published: February 2020

Considerable effort has been focused to search for sustainable and renewable sources of green and clean energy because of the increasing demands and environmental impact of traditional energy resources, such as fossil fuels. Fuel cells (FCs) obtain significant attention as next generation energy sources because of their superior energy conversion efficiency and potential to provide clean energy. Metal-free electrocatalysts for oxygen reduction reaction (ORR) in FCs are an interesting research topic due to low cost much stable and tolerance to crossover effect than that of expensive noble metals. In this study, However, porous graphene (G) catalysts have been prepared with sp3-hybridized 1,4-diaminobutane (sp3-DABu) and sp2-hybridized 1,4-diaminobenzene (sp2-DABe) through a enhanced amidation functionalization and have employed as a metal-free electrocatalyst for oxygen reduction reaction (ORR) in alkaline media. Both compounds have used as a junction between functionalized G layers to improve electrical conductivity and impart electrocatalytic activity to the ORR resulting from the interlayer charge transfer. The successful amidation and the subsequent reduction in the process of catalyst preparation have confirmed by X-ray photoelectron spectroscopy. A hierarchical porous structure is also confirmed by surface morphological analysis. Specific surface area and thermal stability have increased after successful amidation by sp3-DABu. The G catalyst functionalized by sp3-DABu is proved as an efficient metal-free electrocatalyst with better electrocatalytic activity, stability, and tolerance to the crossover effect than the commercially available Pt/C for ORR because of the π-electron interaction-free interlayer charge transfer.

Figure 1
(Invited) New Glycofullerenes for Ebola Virus Infection
Authors: Ramos-Soriano Javier , Pérez Alfonso , Rodríguez-Pérez Laura , Illescas Beatriz , Rojo Javier , Delgado Rafael , Martín Nazario
Published: February 2020

Multivalency is an important issue in the study of carbohydrate−protein interactions as well as for getting a better understanding of the virus infection processes. Thus, different chemical and bio-inspired scaffolds have been used in the literature in the search for new glycoconjugates bearing larger units of carbohydrates located in the appropriate spatial arrangement.

At the molecular level, there are a wide variety of examples where multivalency drastically enhances the interactions between biomolecules in comparison with the monovalent binding. The search for high-affinity ligands for the study and understanding of the mechanisms involved in multivalent interactions has yielded a wide variety of artificial glycoconjugates which include, among others, glycopolymers, glycodendrimers, and glyconanoparticles. Recently, we have shown that hexakis-adducts of [60]fullerene endowed with 12, 24 or 36 mannoses, act as strong inhibitors for DC-SIGN in an Ebola infection assay model.1 Furthermore, a drastic increase in the inhibition process to the subnanomolar scale has been observed when the size and mannoses´ number are increased in the tridecafullerenes endowed with 120 mannose units decorating the periphery of the molecule.2

In this work, we report the synthesis and study of novel carbon nanostructures and carbohydrates for the multivalent presentation in an artificial Ebola virus infection model. These new carbon nanoforms have been chemically modified by the covalent attachment of glycofullerenes using the CuAAC “click chemistry” approach as well as in the absence of Cu in order to prevent the unfavorable metal effect.3 The efficiency to block DC-SIGN mediated viral infection by an artificial Ebola virus has been tested in a cellular experimental assay finding that, these systems are potent inhibitors of viral infection.

References

1. a) J. Luczkowiak, A. Muñoz, M. Sánchez-Navarro, R. Ribeiro-Viana, A. Ginieis, B. M. Illescas, N. Martín, R. Delgado, J. Rojo, Biomacromolecules 
2013, 14, 431-437; b) J.-F. Nierengarten, J. Iehl, V. Oerthel, M. Holler, B. M. Illescas, A. Muñoz, N. Martín, J. Rojo, M. Sánchez-Navarro, S. Cecioni, S. Vidal, K. Buffet, M. Durka, S. P. Vincent, Chem.
Commun. 
2010, 46, 3860-3862; c) M. Sánchez-Navarro, A. Muñoz, B. M. Illescas, J. Rojo, N. Martín, Chem. Eur. J. 
2011, 17, 766-769.

2. A. Muñoz, D. Sigwalt, B. M. Illescas, J. Luczkowiak, L. Rodríguez, I. Nierengarten, M. Holler, J.-S. Remy, K. Buffet, S. P. Vincent, J. Rojo, R. Delgado, J.-F. Nierengarten, N. Martín, Nat. Chem., 2016, 8, 50-57 - DOI: 10.1038/NCHEM.2387.

3. J. Ramos-Soriano, J. Juan Reina, A. Pérez-Sánchez, B. M. Illescas, J. Rojo, N. Martin, Chem. Commun., 2016, 52, 10544-10546 - DOI: 10.1039/C6CC05484F

Figure 1
(Invited) Single Carbon Nanotube Tracking Reveals Nanoscale Organization of the Extracellular Space in Live Brain Tissue
Authors: Cognet Laurent
Published: February 2020

Sub-wavelength localizations of single molecules allows super-resolution imaging and a subtle probing of spatio temporal nano-environments in cells [1].

By using biocompatible luminescent single wall carbon nanotubes (SWCNTs) in the near-IR emission [2,3], here we show an approach to directly observe local structures and rheology of the extracellular space in a brain tissue using super-resolution imaging. Upon injection in live rat cerebroventricles [4], individual SWCNTs are followed for tens of minutes in acute slices as they diffuse inside the extracellular space. Because of the interplay between the nanotube geometry and the extracellular space local environment [5], we can extract information about the extracellular space dimension and local viscosity. We find a striking diversity of extracellular space dimensions down to 40 nm, and as well as of local viscosity values. Moreover, by chemically altering the brain extracellular matrix of the live animals before nanotube injection, we reveal that ECS rheology properties are affected, but that extracellular space alterations are local and inhomogeneous at nanoscale dimensions [6].

 

References

[1] Godin et al , Biophys. J, (2014).

[2] Gao, et al, Biomater. Sci.(2016).

[3] Danné et al submitted

[4] Varela et al Nat. Comm. (2016).

[5] Fakhri et al , Science(2010).

[6] Godin et al Nat. Nanotechnol. (2016).
(Invited) Synthetic Infrared Nanosensors for Brain Imaging of Modulatory Neurotransmitters
Authors: Landry Markita , Beyene Abraham , Del Bonis-O'Donnell Jackson Travis
Published: February 2020

For over 60 years, drugs that alter, mimic, or block modulatory neurotransmitters have formed the core arsenal for the treatment of neurological disorders such as depression, addiction, schizophrenia, anxiety, and Parkinson’s disease. Nonetheless, methods to measure neurotransmitters remain sparse, particularly to detect the three modulatory neurotransmitters that govern brain function: dopamine, serotonin, and norepinephrine. We describe the design, characterization, and implementation of near-infrared optical sensors to image neurotransmitter dopamine. Dopamine is a key molecular governor of brain function, whereby dopamine imbalances lead to neurodegenerative and behavioral disorders. We show direct visualization of endogenous dopamine release over multiple rounds of acute brain slice stimulation, for over 80 minutes. We characterize this sensor in the context of its utility for high spatial and temporal neurotransmitter imaging in the brain, describe it function from a molecular dynamics (MD) perspective, validate its use in vitro, and extrapolate its use in vivo to correlate external stimuli (experiences, behavior) to chemical output (neurotransmission).
Graphene Quantum Dots: Emerging Carbon Nanomaterials
Authors: Hadad Caroline , Gonzalez Dominguez Jose Miguel , Istif Akcan , Da Ros Tatiana
Published: February 2020

Among the various carbon nanostructures, the graphene quantum dots represent an emerging 0D platform with very interesting properties for biological application. More specifically they are properly water-soluble, they can be decorated exploiting different chemical approaches and they possess intrinsic characteristics of fluorescence.

Herein, we report a new top-down strategy to prepare these structures, that has been recently explored and allows an almost quantitative conversion of the carbon source, and some preliminary biological results.
Experimental and Computational Approaches to Explore the the Mechanisms of Carbon Nanotube Biosensing
Authors: Jena Prakrit Vaibhav , Mittal Jeetain , Heller Daniel A , Safaee Mohammad , Roxbury Daniel
Published: February 2020

The intrinsic photoluminescence properties of semi-conducting single-walled carbon nanotubes (SWCNTs), including indefinite photostability, high spectral diversity, environmental sensitivity, and near infrared emission, have recently been exploited for various applications ranging from optical strain sensors to biomedical imaging labels and probes. We have recently shown that one particular separated species of polymer-wrapped SWCNT is able to detect abnormal accumulations of cholesterol and other lipids in the endolysosomal pathways of live cells, indicative of various diseases including atherosclerosis, neurodegenerative disorders, and cancer. Here, we employ all-atom REMD simulations to probe the structure and stability of the demonstrated live-cell lipid sensor. We observe rapid cholesterol aggregation and association with the exposed SWCNT surface, followed by a slower polymer rearrangement. These results shed light onto the mechanism of lipid-modulated blue-shifting observed in live-cell and live-animal experiments.
Single-Walled Carbon Nanotubes for the Quantification of Active Chemotherapy Drugs
Authors: Harvey Jackson Dean , Baker Hanan , Galassi Thomas Vito , Williams Ryan M. , Heller Daniel A
Published: February 2020

Platinum-based chemotherapy drugs have had an enormous impact on cancer treatment, but cancers often become resistant to these treatments through mechanisms which are still poorly understood. To clarify these issues, there is a need for sensors that can detect active cisplatin drug exposure. As optical sensors, single-walled carbon nanotubes (SWCNTs) have properties that make them ideally suited for detection of biologically important analytes. Carbon nanotubes exhibit bandgap fluorescence which does not photobleach or blink, and their fluorescent properties can be modulated by changes in their immediate environment. Tissue transparent emission, biocompatibility, and versatile modes of optical response make SWCNTs uniquely valuable optical biosensors. Recent work by our group has yielded insight into the mechanism of optical changes induced by analyte interaction with single-stranded DNA-wrapped SWCNTs. Using these findings, we designed SWCNT-based sensors for controllable red or blue-shifting responses to platinum-based chemotherapy drugs. We employed these sensors for the purpose of quantifying exposure of tissue to active drug in vivo.
Graphene Oxide: A Modifiable Platform for Drug Delivery Imaging and Sensing
Authors: Naumov Anton V , Sizemore Elizabeth , Hasan Md. Tanvir , Culp Marais
Published: February 2020

Due to its remarkable electronic properties, graphene has become a basis of many novel microelectronic devices. Its functional derivative, graphene oxide (GO), retains multiple properties of graphene, however, unlike graphene is water soluble and exhibits fluorescence over the functionalization-induced optical band gap. A large graphene platform with oxygen containing groups that can be easily functionalized with active agents or analyte binding sites makes GO attractive for biosensing and drug delivery applications. In addition, an intrinsic GO fluorescence in red/near-infrared region with reduced biological autofluorescence background provides a possibility of fluorescence imaging without the need in additional fluorophores. We explore these properties to develop a multifunctional delivery/imaging/sensing GO platform for cancer therapeutics. GO utilized in our work shows little to no apparent cytotoxicity in concentrations of up to 15 ug/mL. We optimize the size of the commercially available GO flakes via ultrasonic processing for the most efficient cellular internalization and use spectrally-resolved fluorescence imaging for in vitro detection in the spectral range specific to GO emission. Furthermore, ozone processing adding extra oxygen-containing functional groups to GO surface is used to spectrally adjust GO emission and enhance its intensity. Solution-based timed ozone treatment allows to blue shift and increase the intensity of the emission. Concomitantly, such processing provides the basis for versatile covalent functionalization of anticancer agents to the new addends on GO platform via synthetic route akin to peptide synthesis. Optimized GO moieties show efficient intracellular accumulation with a potential preference toward the cancer (MCF-7, HeLa) versus healthy (HEK-293) cells. A pH dependence of GO emission discovered in our previous work provides a sensing mechanism for the acidic environment of cancer cells. In this regard, spectrally-resolved fluorescence microscopy imaging suggests a more blue-shifted GO emission in healthy versus cancer cells. As a result we propose GO as efficient multifunctional candidate for in-vitro delivery of active agents, fluorescence imaging and sensing of cancerous environments.
(Invited) Single-Molecule Electronic Sensors to Monitor Conformational Dynamics in Nucleic Acids
Authors: Bouilly Delphine
Published: February 2020

Single-molecule biophysics offers unique insight into the dynamics and mechanistics of biomolecules, unlimited by the inevitable averaging associated with ensemble measurements. Apart from established single-molecule characterization techniques based on optical and force spectroscopies, electronic sensors are emerging as a novel approach for single-molecule biophysics. These ultraminiature, point-functionalized circuits offer a powerful method to isolate and probe biomolecules, with the ability to detect tiny changes in charge or conformation over a uniquely wide range of time scales. In particular, we have demonstrated signal acquisition in fast time scales down to the microsecond range, combined with extended, multi-hour measurement times on the same molecule. In this presentation, I will present recent studies exploring the conformational dynamics of nucleic acids. I will demonstrate how nanoelectronic biosensors can detect, through quantized fluctuations in electrical conductance, successive hybridization and melting events in double-stranded DNA, as well as fluctuations between different folded states in single-stranded telomeric DNA and riboswitch RNA sequences. Electronic sensors open the way towards developing integrated genomic analyses, as well as investigating the mechanistic and dynamics landscape of a variety of biomolecules.