bluuebunny/crossref_metadata_2025_split huggingface dataset:
Graphitic Carbon Nitride: An Excellent Base for Composite Electrodes in Electrochemical Energy Conversion and Storage
Authors: Ola Oluwafunmilola , Zhu Yanqiu 
Published: May 2020

Growing environmental concerns linked with global energy demands have increased the need for sustainable, reliable and portable energy supply that can be delivered from energy conversion to energy storage. Although some emerging electrocatalysts can potentially compete with commercial electrocatalysts in terms of cost per unit kWh when using low-cost precursors to create them, research efforts are still mainly focusing on performance rather than cost. It is expected that flexible energy storage devices with multifunctionalities would spearhead the power management of future energy devices, which requires engineering solutions of volume and weight reduction. Nanocomposites that offer simultaneous energy conversion and storage capabilities with mechanical load bearing are promising candidates to provide these desired functionalities in electrochemical devices. Utilizing hierarchical porous polymers with combined properties of light weight, flexibility and absorption capacity offers numerous possibilities for the development and utilization of nanocomposites in applications ranging from electronics, aerospace, military to transportation where rapid or stored burst of energy is required for peak power, backup power and load levelling to achieve improved efficiency and reliability.
In this work, iron oxide nanoparticles encapsulated in graphitic carbon nitride shells (Fex-NC) were grown on interconnected, macroscopic carbon scaffold after dip coating followed by carbonization to attain multifunctional nanocomposites. The resulting composites based on the graphitic carbon nitride base possess combined properties of superb structural flexibility, high strength to weight ratio and mechanical stability. The Fex-NC nanocomposites were tested for energy conversion and storage, to take advantage of their porous graphitic carbon nitride features which would be beneficial for optimal ion transport to iron oxide nanoparticles. We have found that the resulting graphitic carbon nitride shells prevented direct contact between iron oxide nanoparticles and acidic electrolyte (H2SO4), so that improved efficiency, stability and corrosion resistance were achieved. They also exhibit excellent electrochemical performances with overpotentials of 191 mV to reach current density of 10 mA/cm2 for hydrogen evolution reaction. In addition to demonstrating excellent specific capacitance, these nanocomposites also possess good stability after 8 hours of testing. The results demonstrate that the physicochemical properties of multifunctional 3D foams developed from simultaneous carbonization and dip coating of polymeric templates can be used as an excellent base to host a variety of nanoparticles to create composite electrocatalysts and be further exploited for future energy and environmental technologies.
Up- and Down-Converting Photons in Molecular Carbon Materials
Authors: Guldi Dirk M. 
Published: May 2020

The Shockley-Queisser limit places an upper bound on solar conversion efficiency for a single p-n junction solar cell at slightly more than 30%. To surpass this limit, multi-exciton generation is being explored in inorganic semiconductors, while singlet fission (SF) is being investigated in arrays of conjugated organic molecules. In an optimal SF process, the lowest singlet excited state of one molecule (S1) that is positioned next to a second molecule in its ground state (S0) is down-converted into two triplet excited states (T1) each residing on one of the two adjacent molecules. The two triplet states initially form a correlated pair state 1(T1T1), which then evolves into two separated triplet states (T1 + T1). As such, the energetic requirement for SF is E(S1) ≥ 2 ´ E(T1).
We have set our focus in recent years on intramolecular SF in molecular carbon materials and their studies in solution rather than on intermolecular SF investigations in crystalline films.
Implicit in intramolecular SF is a resonant, direct excitation of the SF material. In dimers of molecular carbon materials linked by a myriad of molecular spacers, SF takes place with quantum yields of up to 200%. In addition, all key intermediates in the SF process, including the formation and decay of a quintet state that precedes formation of the pentacene triplet excitons, have been identified. This approach is, however, limited to the part of the solar spectrum, where, for example, the dimers of carbon materials feature a significant absorption cross-section. To employ the remaining part of the solar spectrum necessitates non-resonant, indirect excitation of the SF materials via either up- or down-conversion. For example, the up-conversion approach is realized with singlet excited states , which are accessed by two-photon absorptions (TPA). TPA is then followed in the second step of the sequence by an intramolecular SF – similar to what is seen upon resonant, direct excitation. Quite different is the down-conversion approach, which is based on an intramolecular Förster resonance energy transfer (FRET) and thereby the (photo)activation of the SF material. FRET requires the use of a complementary absorbing chromophore and enables funneling its excited state energy unidirectionally to the SF performing pentacene dimer. Again, SF completes the reaction sequence.
(Invited) Near Infrared Imaging of Chemical Signaling between Cells Using Fluorescent Nanosensors
Authors: Kruss Sebastian 
Published: May 2020

Cells use small molecules to exchange information. A very prominent example is neurotransmitter signaling between neuronal cells or paracrine signaling between blood cells. However, it is up to date difficult to visualize signaling processes between cells with high spatial, temporal and chemical resolution. We are interested in developing fluorescent sensors/probes that overcome these limitations and answer novel biological questions.
For that purpose we use near infrared (nIR) fluorescent single-walled carbon nanotubes (SWCNTs). SWCNTs fluoresce in the nIR tissue transparency window (900 nm -1700 nm) and do not bleach. They are chemically modified to render them selective for neurotransmitters such as dopamine and serotonin. In this context, we developed different chemical strategies that include screening for artificial binding motifs, aptamers and nanobodies. Using these strategies we created sensors for the neurotransmitters dopamine and serotonin that increase their fluorescence in the presence of the target molecule and detect down to single molecules. Fast parallel imaging of many of those sensors provides a nIR image (>900 nm) of the neurotransmitter concentration around cells. This technique was used to image hot spots of dopamine release from primary dopaminergic neurons. It enabled us to observe localized release sites and correlate it with the exocytosis machinery of the cells. Neurotransmitters are not only relevant in the neuronal system but as well in the periphery e.g. in blood cells. In this context, we imaged for the first time how human blood platelets release serotonin after activation and resolved the heterogeneity in release patterns. These results illustrate that tailored SWCNTs are powerful tools for quantitative chemical imaging of biological processes.
(Invited) Near-Infrared Optical Probes for Imaging Neuromodulators with High Spatiotemporal Resolution
Authors: Beyene Abraham G , Delevich Kristen , Wilbrecht Linda , Landry Markita P 
Published: May 2020

Dopamine neurotransmission plays critical roles in brain function in both health and disease and aberrations in dopamine neurotransmission are implicated in several psychiatric and neurological disorders, including schizophrenia, depression, anxiety, and Parkinson’s disease. Until recently, measuring the dynamics of dopamine and other neurotransmitters of this class could not be achieved at spatiotemporal resolutions necessary to understand how dopamine regulates the plasticity and function of neurons and neural circuits, and how dysfunctions in this regulation lead to disease. Probes that satisfy critical attributes in spatial and temporal resolution, and chemical selectivity are needed to facilitate investigations of brain neurochemistry.
To address this need, we developed an ultrasensitive near-infrared “turn-on” nanosensor (nIRCat) for the catecholamines dopamine and norepinephrine and implemented nIRCat to study endogenous dopamine dynamics in brain tissue. nIRCats are synthesized from photostable and near infrared emissive functionalized single wall carbon nanotubes (SWCNT) and exhibit maximal relative change in fluorescence intensity (ΔF/F0) of up to 35-fold, with a dynamic range that spans physiological concentrations of their target brain analytes. We demonstrate that nIRCat can detect electrically and optogenetically evoked release of dopamine in brain tissue, revealing putative hotspots of activity that exhibited a log-normal distribution in size, ranging from 2 – 10 µm for mice brain tissue in the dorsomedial striatum. Furthermore, the synthetic nature of the molecular recognition platform afforded compatibility with dopamine-receptor targeting antipsychotics and psychoactive drugs and permitted studies of how such receptor-targeting drugs modulate evoked dopamine release. This assay revealed presynaptic correlates of drug activity at the level of putative dopamine release sites, which had heretofore been inaccessible to probe with existing tools. Our results suggest that nIRCat technology may uniquely support similar explorations of processes that regulate dopamine neuromodulation at the level of individual synapses, and exploration of the effects of receptor agonists and antagonists that are commonly used as psychiatric drugs as well as drugs that lead to substance use disorder. We conclude that SWCNTs can serve as versatile synthetic optical scaffolds for monitoring interneuronal chemical signaling in the brain extracellular space at spatial and temporal scales pertinent with the encoded neurochemical information.
(Invited) Development of Single Walled Carbon Nanohorn Systems for Biological Applications
Authors: Quinn Susan Jane 
Published: May 2020

The combination of biocompatibility and unique surface properties has led to the extensive study of the biological applications of carbon nanomaterials. We are interested in the application of single walled carbon nanohorns (CNH) for the development of tools for cellular imaging, diagnostics and therapeutics. CNHs are made up of sp2 conical shaped postulates, with diameters of 2–5 nm and lengths of 40–50 nm, assembled into robust bud-like spherical aggregates of between 80 and 100 nm. The key advantage of these materials is their low toxicity, high surface area, and ease of functionalisation.1,2 In this presentation results from our recent work on the use of CNHs for enhanced biosensing of glutamate,3 to study of the cellular interactions of fluorescently labelled CNH systems and their use of CNHs to delivery photodynamic therapy agents to cells will be presented.
The poor cellular uptake of many porphyrins is a barrier to their application in phototherapeutic applications,4 biocompatible CNH carriers offer a means to overcome this. A spectroscopic study of the binding interactions of the PtTMPyP4 cationic porphyrin with oxidised carbon nanohorns through non-covalent, electrostatic interactions revealed a high a loading of 200 wgt%. Brightfield microscopy demonstrated the efficacy of sparsely loaded Porphyrin-CNH constructs to be internalised within HeLa cells, which were found to undergo rapid cell death upon visible light excitation.5

The ability to image processes in cells and track the interaction and efficacy of nanomaterial cellular uptake is of great interest. The use of an ON/OFF fluorophore whose emission is triggered upon cellular uptake will be described as a means to monitor time dependent uptake by live-imaging and also to report on the influence of functionalisation on the extent of cellular aggregation.6 Finally, some more recent results on tracking the destination of carbon nanohorns in cells will be reported.
1. Iijima, M. Yudasaka, R. Yamada, S. Bandow, K. Suenaga, F. Kokai, K. Takahashi, Chem. Phys. Lett. 1999, 309, 165−170.S.
2. Zhuab, G. Xu, Nanoscale, 2010, 2, 2538–2549.
3. R. Ford, S. J. Devereux, S. J. Quinn, R. D. O'Neill, Analyst, 2019, 144, 5299-5307
4. A. Rajora, J.W.H. Lou and G. Zheng, Chem. Soc. Rev., 2017, 46, 6433 – 6469.
5. J. Devereux, M. Massaro, A. Barker, D. T. Hinds, B. Hifni, J. C. Simpson and S. J. Quinn, J. Mater. Chem. B, 2019, 7, 3670–3678.
6. S. J. Devereux, S. Cheung, H. C. Daly, D. F. O'Shea and S J. Quinn, Chem. Eur. J., 2018, 24, 14162–14170.
Large Area, High-Density SWCNT Forests with Remarkably Invariant Structural Properties over a Wide Range of Synthesis Conditions
Authors: Park Sei Jin , Meshot Eric R. , Buchsbaum Steven F. , Jue Melinda L. , Wu Kuang Jen , Fornasiero Francesco 
Published: May 2020

Driven by the exceptional thermal, electrical, optical, mechanical and fluidic properties of single-walled carbon nanotubes (SWCNT), commercial use of vertically aligned “forests” are on the horizon for applications1 ranging from optical absorbers and thermal interfaces to selective membranes and advanced fabrics.2,3 Large-area SWCNT forests with high densities and small diameters are especially important for many applications, yet they are conspicuously absent from the literature due to synthesis challenges.
Here, we demonstrate synthesis of high-density (> 1012 CNTs/cm2), small-diameter (~ 2 nm) SWCNT forests with structural characteristics that remain uniform over large areas (up to 6-in. diameter)4 and, surprisingly, largely unchanged over a wide range of synthesis conditions. We find also that our growth regime enables a record-high carbon conversion efficiency and a stable mass kinetics, both of which are invariant with catalyst type (Fe vs Fe/Mo mixes). To identify the limiting steps in the SWCNT growth kinetics and the factors contributing to the process robustness, we determine the dependence of the reaction rate and carbon conversion efficiency on broad ranges of synthesis parameters. Effects of catalyst area (from 1 × 1 cm2 to 6-in wafers), growth pressure (10-750 mbar), gas composition (30-fold acetylene partial pressure variation), and flowrates are presented.
Our demonstration of such exceptionally robust and reproducible synthesis of high-density forests over large areas provides valuable insights for future scale-up efforts of SWCNT forest production that are necessary for widespread adoption of advanced CNT technologies.
1. R. Rao et al., ACS Nano., 12 (2018) 11756.
2. N. Bui, E. R. Meshot, S. Kim, J. Peña, P. W. Gibson, K. J. Wu, F. Fornasiero, Adv. Mater., 28 (2016) 5871.
3. Y. Li, C. Chen, E. R. Meshot, S. F. Buchsbaum, M. Herbert, R. Zhu, O. Kulikov, B McDonald, N. Bui, M. L. Jue, S. Park, C. Valdez, S. Hok, C. J. Doona, K. J. Wu, T. M. Swager, F. Fornasiero, submitted (2019)
4. E. R. Meshot, S. Park, S. F. Buchsbaum, M. L. Jue, T. R. Kuykendall, E. Schaible, L. B. Bayu Aji, S. Kucheyev, K. J. Wu, F. Fornasiero, submitted (2019).
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-797268
Raman Imaging Study of Alpha-Sexithiophene Encapsulation in Single-Walled Carbon Nanotubes
Authors: Allard Charlotte , Gaufres Etienne , Desjardins Patrick , Martel Richard 
Published: May 2020

Single-Walled Carbon Nanotubes (SWNTs) are nanosystems with a large aspect ratio that have potential in a wide range of optical applications. Notably, the hollowness of SWNTs interior allows endohedral filling, in which the SWNTs act as a template for the creation of new hybrid nanostructures. It was shown recently that dyes encapsulated inside carbon nanotubes (CNTs) are protected from degradation and present a strong Raman signature with narrow emission peaks, free of background fluorescence [1]. Further, confinement inside SWNTs was found to largely impact molecular organisation, tuning the physical and chemical properties of the encapsulated molecules. In this study, we explore the encapsulation mechanism of dye molecules in SWNTs. α-sexithiophene molecules were chosen due to their well-conjugated, rod-like structure and giant Raman signal upon encapsulation, at an excitation of 532 nm.
A model system composed of long (>10 um) and aligned SWNTs was used, in which CVD-grown SWNTs are patterned by electron-beam lithography (EBL) and opened by oxygen plasma reactive ion etching (O2 RIE). The encapsulation is carried-out using a liquid-phase protocol, which allows the study of different encapsulation processes, such as dye entryways, aggregation formation and dynamics, as well as the relationship between encapsulation parameters (concentration, temperature, solvent) and yield. Due to their length, these SWNTs are well resolved by Raman imaging (RIMA, Raman Imaging system, Photon etc.) and provide a direct visual of the encapsulation process in this 1D system.
[1] Gaufrès, E., et al. Giant Raman scattering from J-aggregated dyes inside carbon nanotubes for multispectral imaging. Nature Photonics 8(1), 72 (2014).
(Invited) Growth and Characterization of Various Van Der Waals Hetero-Nanotubes Based on Single-Walled Carbon Nanotubes
Authors: Maruyama Shigeo 
Published: May 2020

We have synthesized a new coaxial nanotube structure, in which mono- or few-layer hexagonal boron nitride nanotube (BNNT) seamlessly wrap around a single-walled carbon nanotube (SWCNT); SWCNT@BNNT [1]. We named these as one-dimensional van der Waals hetero-nanotubes, because we found no correlation between chiral angle of inner SWCNT and outer BNNT for ‘double-walled’ SWCNT@BNNT. We have further developed the 1D coating CVD of transition metal dichalcogenide nanotubes (TMD-NT), such as MoS2 nanotubes and WSe2 nanotubes. We can grow MoS2 nanotubes around relatively large diameter SWCNT or SWCNT@BNNT. These nanotubes can be labelled as SWCNT@TMD-NT or SWCNT@BNNT@TMD-NT as shown in Fig. 1. Because BNNT is thermally more stable than SWCNT, we can remove SWCNT from SWCNT@BNNT by the gentle oxidation process. Hence, we can produce BNNT with inner diameter determined by the original SWCNT. Then, the MoS2 CVD can result BNNT@TMD-NT or TMD-NT@BNNT as shown in Fig. 1. Recently, CVD growth of carbon nanotubes over SWCNT@BNNT is realized, resulting SWCNT@BNNT@SWCNT. These hetero-nanotubes are characterized by HR-TEM, STEM-EELS, optical absorption, FT-IR, Raman scattering, Photoluminescence spectroscopy.
Part of this work was supported by JSPS KAKENHI Grant Numbers JP15H05760, JP18H05329.
Reference:
[1] R. Xiang, T. Inoue, Y. Zheng, A. Kumamoto, Y. Qian, Y. Sato, M. Liu, D. Gokhale, J. Guo, K. Hisama, S. Yotsumoto, T. Ogamoto, H. Arai, Y. Kobayashi, H. Zhang, B. Hou, A. Anisimov, Y. Miyata, S. Okada, S. Chiashi, Y. Li, E. I. Kauppinen, Y. Ikuhara, K. Suenaga, S. Maruyama, arXiv:1807.06154 (2019).

Figure 1
(Invited) Combining Absorption, Wavelength-Dependent Raman and Fluorescence-Excitation Spectroscopy with High-Resolution Transmission Electron Microscopy for Determining the Chiral Purity of Sorted SWCNT Samples
Authors: Cambré Sofie , Forel Salomé , Castan Alice , Defillet Joeri , Levshov Dmitry , Fossard Frederic , Wenseleers Wim , Loiseau Annick 
Published: May 2020

Single-wall carbon nanotubes (SWCNTs) possess unique electronic and optical properties that depend strongly on their exact chiral structure. Recent progress in the structure sorting of specific SWCNT chiralities, with increasing chiral purity[1], demands an effective characterization methodology to be developed to accurately determine the chiral composition of any SWCNT sample. Very often, optical spectroscopy is used to assess the chiral composition of a sample, but absorption cross-sections, PL quantum efficiencies and Raman cross-sections are all depending on the exact chiral structure,[2] and can be strongly influenced by other factors such as the specific internal and external environment of the SWCNTs.[3] In this work, we systematically compare the chirality distribution obtained from 3 different optical spectroscopic techniques, i.e. absorption, wavelength-dependent Raman and fluorescence-excitation spectroscopy with the chirality distribution obtained from high-resolution transmission electron microscopy for both chirality-sorted and unsorted SWCNT samples. This combined approach demonstrates the importance of using a multi-technique characterization strategy for a reliable determination of SWCNT chirality distribution.
[1] J.A. Fagan, Nanoscale Adv. 1, 3307 (2019) and references therein
[2] V.N. Popov, Nano Lett. 4, 1795 (2004)
[3] S. Cambré et al, Angew. Chem. – Int Ed. 50, 2764 (2011); ACS nano 6, 2649 (2012)
(Invited) Different Fluorescent Modifications of Carbon Nanotubes with Aromatic Reactants
Authors: Bachilo Sergei M. , Zheng Yu , Weisman R. Bruce 
Published: May 2020

Covalent functionalization of single-wall carbon nanotubes (SWCNTs) can produce a stable material with electronic and optical properties enhanced purposely as compare to original species. In the present report we describe a new category of reactions between photoexcited aromatic compounds and SWCNTs, creating different fluorescent trapping states in SWCNTs. The reactions take place in aqueous suspensions of SWCNTs with small addition of soluble or even very-slightly soluble organic aromatic compounds excited by UV light. The reaction rate depends on the aromatic compound structure and proportional to its concentration, and in some cases, as with aniline or iodoaniline, these strong spectral sidebands appear within one minute. Total SWCNT photoluminescence intensity can be increased by a factor as large as 5. Shifted emission bands and the trapping nature of them may be interesting for a variety of optical and electronic applications.
Most notably, in most cases of these photochemical reactions, the emission spectra of altered SWCNTs become different, never observed previously, upon removal of molecular oxygen from the solution, thus indicating different chemical products of the reactions. For instance, for (6,5) SWCNTs, treatment in oxygen presence gives a new emission band red-shifted by 160 meV from the pristine position, which is similar to many previously studied reactions starting with oxygen doping. However, same UV treatments after dissolved molecular oxygen removal will lead to two new emission bands red-shifted by 140 and 270 meV, growing with different rate under UV illumination. Variance spectroscopy shows the presence of individual “multicolor” nanotubes with three distinct emission bands, original plus two shifted. The reaction demonstrates new possibilities for creation different trapping states on individual nanotubes, and opens new options for tuning electronic and optical properties of nanotubes for possible applications.