bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Synthesis and Optical Properties of Graphene Nanoparticles
Authors: Medina Lopez Daniel , Liu Thomas , Rondin Loic , Lauret Js , Campidelli Stephane 
Published: July 2021

In recent years, the scientific community has given much interest to graphene as a material because of its good mechanical, thermal and electrical properties. Nevertheless, the lack of a bandgap in graphene limits its optical and optoelectronic applications. To tackle this problem, size reduction, a popular technique for bandgap engineering, has been used. Thus, we shine our interest in graphene quantum dots (GQDs). GQDs synthesis has been mostly described via top-down methods (lithography, hydrothermal and electrochemical approaches).1 Though cheap and efficient, these methods do not allow for precise control of the size, shape and edges of the GQDs. This is where bottom-up approaches, especially the ones borrowing known reactions from organic chemistry, come in handy.2

Our group has previously reported single-photon emission from functionalized bottom-up synthesized GQDs.3 We wish to improve our understanding of GQDs optical properties. For this purpose, we have synthesized nanoparticles having the same number of hybridized sp2 carbons but arranged in different shapes (Figure 1). Besides modifying the optical properties, we also aim to improve the solubility of the GQDs by changing the functional groups at the edge of the nanoparticle. An improved solubility should simplify the study of individualized nanoparticles.
References :
[1] Yang, J.-S., Martinez, D. A. & Chiang, W.-H. Synthesis, Characterization and Applications of Graphene Quantum Dots in Recent Trends in Nanomaterials: Synthesis and Properties, Khan, Z. H., Springer Singapore, (2017).
[2] Müller, M., Kübel, C. & Müllen, K. Giant Polycyclic Aromatic Hydrocarbons. Chem. Eur. J.
4, 2099–2109 (1998).
[3] Zhao, S. et al. Single photon emission from graphene quantum dots at room temperature. Nat. Commun.
9, 1–5 (2018).

Figure 1
In-Situ Crossover Measurements for Vanadium-Based Non Aqueous Redox Flow Battery
Authors: Mushtaq Kashif , Mendes Adelio 
Published: July 2021

The efficient operation of the non-aqueous redox flow battery (NAqRFB) requires a selective membrane that prevents the crossover of the charged storage molecules (redox species) to minimize self-discharge or mixed potentials; actually, the crossover-induced capacity loss remains one of the most challenging problems for NAqRFB. At the same time, the membrane must enable high ionic conductivity (ions from supporting electrolyte) to lower ohmic losses. The identification of a highly conductive, yet selective membrane is of paramount importance for market penetration of RFBs. Although the membrane should be extremely selective, for allowing years of continuous operation, the truth is that all commercially used membranes allow to some extent redox species permeation, especially when a thinner membrane is pursued to ensure high ionic conductivity. In terms of capacity retention, the reactant that crosses directly through the membrane is oxidized or reduced without providing electrical work, leading to lower efficiency. Therefore, crossover in a NAqRFB and its impact on cell operation is a critical phenomenon that needs to be quantified and mitigated in the development of redox flow-cells.
The crossover through the membrane is problematic since it leads to loss of capacity and self-discharge. An in-situ electrochemical method based on linear sweep voltammetry was introduced to determine crossover through different membranes. The results were further confirmed through the permeance of redox ion using an ex-situ method, performance characterization, and by measuring the overpotentials. Ferrocene is reported as a model probing species for in-situ crossover measurement. The cation exchange membrane having a higher thickness (Nafion 117) and anion exchange membrane having reinforcement (FAPQ-375-PP) performed better. The model redox species (vanadium acetylacetonate) were used for the performance assessment of NARFB. The columbic efficiency was 91.47 % and voltaic efficiency of 72.9 %. The ohmic and mass transport overpotentials affecting the performance of NARFB were 0.46 V and 1.44 V. This in-situ technique will allow researchers to account for the contribution of migration-driven crossover influenced by the applied electrical field and not only the diffusion-based crossover as reported in the previous studies. Since there is no need for disassembling of the cell, so it can be used as a diagnostic tool to assess the realistic membrane situation under actual working conditions. The quantification of the permeance directly from the flow-cells and overpotentials complements the improvement in the designing and toward further optimization of the operational parameters. Due to its convenience and practicability, this technique has the potential to become the basic testing method to determine crossover and aid in membrane selection for many electrochemical cells/systems. This work is still in progress for in-depth study covering other aspects as well.

Figure 1
Why Two-Dimensional Semiconductors Generally Have Low Electron Mobility
Authors: Cheng Long , Zhang Chenmu , Liu Yuanyue 
Published: July 2021

Atomically thin (two-dimensional, 2D) semiconductors have shown great potential as the fundamental building blocks for next-generation electronics. However, all the 2D semiconductors that have been experimentally made so far have room-temperature electron mobility lower than that of bulk silicon, which is not understood. Here, by using first-principles calculations and reformulating the transport equations to isolate and quantify contributions of different mobility-determining factors, we show that the universally low mobility of 2D semiconductors originates from the high “density of scatterings,” which is intrinsic to the 2D material with a parabolic electron band. The density of scatterings characterizes the density of phonons that can interact with the electrons and can be fully determined from the electron and phonon band structures without knowledge of electron-phonon coupling strength. Our work reveals the underlying physics limiting the electron mobility of 2D semiconductors and offers a descriptor to quickly assess the mobility [1,2,3].
[1] L. Cheng, C. Zhang, Y. Liu, Phys. Rev. Lett., 2020, DOI: 10.1103/PhysRevLett.125.177701
[2] L. Cheng, C. Zhang, Y. Liu, J. Am. Chem. Soc., 2019, DOI: 10.1021/jacs.9b05923
[3] L. Cheng, Y. Liu, J. Am. Chem. Soc., 2018, 140, 17895-17900
(Invited) Integration of 2D Materials in Van Der Waals Photonic Heterostructures
Authors: Ignatova Tetyana , Pourianejad Sajedeh , Rotkin Slava V. 
Published: July 2021

Recently, significant attention has been focused at photonic properties of vertical heterostructures of two-dimensional (2D) materials which is driven by large range of their applications in sensing and information technology. In this work, the Van der Waals heterostructures were produced by integration of CVD grown 2D MoS2 with transferred monolayer graphene. Each of 2D layers possesses its own surface electromagnetic (optical) modes. While in the photonic heterostructure these modes are strongly coupled. Scattering-type scanning near-field optical microscopy allows to visualize 2D surface polaritons, as well as their hybridization with the resonances of the bulk substrate polaritons. Using excitation frequencies well below substrate resonances, a signature of charge transfer in van der Waals heterostructures with nanometer resolution was obtained.
Acknowledgement: Authors acknowledge the JSNN, a member of the Southeastern Nanotechnology Infrastructure Corridor (SENIC) and National Nanotechnology Coordinated Infrastructure (NNCI), supported by the NSF (ECCS-1542174), The PSU Two-Dimensional Crystal Consortium – Materials Innovation Platform 2DCC-MIP, supported by NSF cooperative agreement (DMR-1539916). S.V.R. acknowledges PSU MRSEC supported by NSF (DMR-2011839). Authors are grateful to Dr. S. Aravamudhan (JSNN) and Dr. J. Redwing (2DCC-MIP).
(Invited) Additively Manufactured Graphene Aerogel Supercapacitors
Authors: Beck Victor A , Chandrasekaran Swetha , Salazar de Troya Miguel , Lin Dun , Reale Batista Mariana Desiree , Yao Bin , Moran Bryan , Zhu Cheng , Duoss Eric B , Stadermann Michael , Tortorelli Daniel , Li Yat , Worsley Marcus Andre 
Published: July 2021

Electrochemical energy storage (EES) and conversion devices (e.g. batteries, supercapacitors, and reactors) are emerging as primary methods for global efforts to shift energy dependence from limited fossil fuels towards sustainable and renewable resources. These electric-based devices, while showing great potential for meeting some key metrics set by conventional technologies, still face significant limitations. For example, an EES device tends to exhibit large energy density (e.g. lithium-ion battery) or power density (e.g. supercapacitor), but not both. This inability of a single device to simultaneously achieve both metrics represents a major obstacle to widespread adoption of EES devices. Improvements in materials, such as the integration of 2D materials (e.g. graphene, dichalcogenides, MXene, etc.) into electrochemical devices has yielded some exciting results towards tackling this issue, but significant improvements are still needed. Our approach to simultaneously achieving high energy and power density is to focus on one of the fundamental processes that occur in these systems: mass (or charge) transport. The efficient transport of ions within EES devices is critical to realizing both large power and energy densities. The pore structure of the electrode is a key factor in determining this transport phenomena, but in many cases, engineering the pore structure in a highly deterministic fashion is not pursued or even possible for many electrode materials. In this work, we explore a number of additive manufacturing methods (e.g. direct ink write, projection microstereolithography, etc.) to engineer the pore structure of device electrodes. We also determine effective electrode geometries using both simple theory and topology optimization techniques. The topology optimization couples the solution of the forward electrochemical problem over the full electrode domain with gradient-based optimization. The output of our code is a three-dimensional CAD representation which optimizes over specific performance metrics and which can be used to print functional electrodes. This work provides a systematic path toward automatic design and fabrication of engineered electrodes with precise control over the fluid and species distribution.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Invited) Lead-Free Halide Perovskites for Hydrogen Evolution
Authors: Listorti Andrea 
Published: July 2021

Metal halide perovskites (MHPs) semiconductors possess unique optical properties, such as high optical absorption in the visible region, tunable band-gap and long carrier lifetime, which have been extensively exploited in photovoltaics and optoelectronic applications.[1] More recently there has been a growing interests towards novel applications of MHPs, in particular in the field of solar-driven photocatalysis.[2] However, some of the most interesting photocatalytic reactions such as H2O splitting, CO2 and N2 reduction, dye degradation, require the use of water or alternative polar solvents, this represent a conundrum foreseeing MHPs utilization. In this talk we report clear evidence of water stability for two lead-free metal halide perovskites, namely dimethylammonium (DMA) DMASnBr3 and phenylethylammonium (PEA) PEA2SnBr4 obtained by means of diffraction, optical and x-ray photoelectron spectroscopy. The water stability for the 2D material is somehow expected due to the water-repulsive nature of the symmetry breaking organic cation, some computational work is addressing such improved water stability, showing also that the same mechanism is thought to protect tin from +2 to +4 oxidation. The stability in water of the 3D analogous represent instead an important innovation of the field. Such unprecedented water-stability has been applied to promote photocatalysis in aqueous medium, in particular by devising a novel composite material by coupling DMASnBr3 to g-C3N4, taking advantage from the combination of their optimal photophysical properties. The prepared composites provide an impressive hydrogen evolution rate >1700 μmol g-1 h-1 generated by the synergistic activity of the two composite constituents. DFT calculations provide insight into this enhancement deriving it from the favorable alignment of interfacial energy levels of DMASnBr3 and g-C3N4. The demonstration of an efficient photocatalytic activity for lead-free metal halide perovskites in water paves the way to a new class of light-driven catalysts working in aqueous environments.

References

[1] S. D. Stanks, H. L. Snaith, Nature Nanotec. 2015, 10, 931-402.
[2] H. Huang, B. Pradhan, J. Hofkens, M. B. Roeffaers, J. A. Steele, ACS Energy Letters 2020,
5, 1107-1123.
[3] L. Romani, A. Bala, V.Kumar, A. Speltini, A. Milella, F. Fracassi, A. Listorti, A. Profumo, L.Malavasi. Journal of Materials Chemistry C, 2020, 8, 9189-9194
[4] L. Malavasi, L. Romani, A. Speltini, F. Ambrosio, E. Mosconi, A. Profumo, S. Margadonna, A. Milella, F. Fracassi, A. Listorti, F. De Angelis and M. Marelli. (2020), Angew. Chem. Int. Ed.. Accepted Author Manuscript. https://doi.org/10.1002/anie.202007584

Figure 1
Combinatorial Development of LSF Based Cathode Material for IT-SOFC
Authors: Kılıç Fahrettin , Öztürk Tayfur 
Published: July 2021

The primary challenges for the commercialization of the technology are considered to be costs and durability. To accommodate this, research is pushing towards lower cell operation temperature (intermediate temperature SOFC, IT-SOFC) in the range of 500–700 0C [1,2]. The lower temperatures involve advantages such as wider and cheaper choice of materials (e.g. metals), increased material durability, and increased system stability.
The progress in this field is, inevitably associated with a continuous search for novel cathode and anode materials having superior electrocatalytic activity in the intermediate-temperature range. These developments have also a key importance for other solid-state electrochemical devices, such as electrolyzer of carbon dioxide and water vapor [3].
The fact that oxygen reduction rate is faster at the interface ,necessitates cathodes to be considered as composite. In this context, the traditional method is to mix cathode with electrolyte. This approach allows oxygen to be reduced at the interface and transported at the same time. Mixing cathode with electrolyte allows us to adjust the thermal expansion coefficient of the cathode. Another benefit of this approach is better bonding between the cathode and the electrolyte.

Experimental

The aim is to find the best cathode composition as a mixture of (La0.5Sr0.5)MnO3-δ (LSM), (La0.8Sr0.2)FeO3-δ (LSF) and (Zr10.92Sc0.08)O2- δ (8ScSZ) for IT-SOFC. In this study LSM, LSF and ScSZ targets were sputtered on both sides of Zr10.92Sc0.08 O2- δ electrolyte to form symmetric cells. We obtained 21 cells at the same time each with a different cathode composition. Geometry of targets and substrate is given in figure 1.
Figure 1.Target and substrate geometries
The produced cells were structurally characterized with XRD and SEM. Electrochemical performance of cells were determined using electrochemical impedance spectroscopy. The target working temperature is 600 0C and area specific resistance is maximum 0.15 ohm.cm2.

References

[1] R. Knibbe, J. Hjelm, M. Menon, N. Pryds, M. Søgaard, H.J. Wang, K. Neufeld, J. Am. Ceram. Soc. 93 (9) (2010) 2877–2883.
[2] M.C. Tucker, J. Power Sources 195 (15) (2010) 4570–4582.
[3] Tsipis, E. V., & Kharton, V. V. (2007). Journal of Solid State Electrochemistry,12(9), 1039-1060.

Acknowledgement

The support was provided by the Scientific and Technological Research Council of Turkey (TUBITAK) with a project number 217M628, which the authors gratefully acknowledge.

Figure 1
(Invited) Structural Analysis of Organic Semiconducting Materials Using Solid-State NMR
Authors: Suzuki Katsuaki , Kaji Hironori 
Published: July 2021

Our research group is currently conducting basic research on organic light-emitting diodes (OLEDs). Recently, we have successfully developed a series of blue and green TADF emitters for OLEDs realizing high external quantum efficiencies through high-throughput screening based on quantum chemical calculations. However, even using highly efficient emitting materials, the device performance depends on the device structure and aggregated state of organic molecules in the device. To understand the origin of the device performance, both theoretical and experimental approaches are important. In this regards, we have also carried out multiscale simulations and solid-state NMR (ssNMR) analysis of organic amorphous thin films. The ssNMR is the powerful technique for the detailed experimental analysis of amorphous aggregated materials, which has been difficult by typical diffraction methods because organic molecules in OLEDs are in the amorphous state. In this presentation, we demonstrate the structural analysis of organic semiconducting materials using ssNMR. Also, we we show the analysis of molecular orientation of an organic semiconducting material in an amorphous thin film state using DNP-ssNMR, which is one of the most powerful sensitivity enhancement technique of NMR.
Reference
(1) “Analysis of Molecular Orientation in Organic Semiconducting Thin Films Using Static Dynamic Nuclear Polarization Enhanced Solid-State NMR Spectroscopy”, Suzuki, K.; Kubo, S.; Aussenac, F.; Engelke, F.; Fukushima, T.; Kaji, H. Angew. Chem. Int. Ed. 2017, 56, 14842.
(2) “Solution-processable thermally activated delayed fluorescence emitters for application in organic light emitting diodes”, Suzuki, K.; Adachi, C.; Kaji, H. J. Soc. Inf. Disp.
2017, 25, 480.
(3) “Combined Inter- and Intramolecular Charge-Transfer Processes for Highly Efficient Fluorescent Organic Light-Emitting Diodes with Reduced Triplet Exciton Quenching”, Moon, C.-K.; Suzuki, K.; Shizu, K.; Adachi, C.; Kaji, H.; Kim, J.-J. Adv. Mater.
2017, 131, 6614.
(4) “Triarylboron-based Fluorescent Organic Light-emitting Diodes with External Quantum Efficiencies Exceeding 20%”, Suzuki, K.; Kubo, S.; Shizu, K.; Fukushima, T.; Wakamiya, A.; Murata, Y.; Adachi, C.; Kaji, H.; Angew. Chem. Int. Ed. 2015, 54, 15231.
(5) “Purely organic electroluminescent material realizing 100% conversion from electricity to light”, Kaji, H.; Suzuki, H.; Fukushima, T.; Shizu, K.; Suzuki, K.; Kubo, S.; Komino, T.; Oiwa, H.; Suzuki, F.; Wakamiya, A.; Murata, Y.; Adachi, C. Nat. Commun. 2015, 6, 8476.
(Invited) Synthesis and Optical Properties of Core-Shell Swnt Hybrids
Authors: Orcin-Chaix Lucile , Hanana Manel , Rondin Loic , Bretenaker Fabien , Chassagneux Yannick , Voisin Christophe , Lauret Js , Campidelli Stephane 
Published: July 2021

Because of their emission in the near infrared region, Single-Walled Carbon Nanotubes remain among the most attractive nanomaterials for (opto)electronics, optics and photonics.1
-
3 However, the extreme sensitivity of nanotubes to their environment hinders their applications. Thus, the fabrication of tailor-made functional hybrid materials that preserve the optical properties of SWNTs and facilitate their manipulation is extremely important. One route to take advantage of the protection offered by polymers is to synthesize core/shell nanostructures in which the nanotube is the active core and the polymer, tightly bound to the nanotubes, acts as a protective shell.
Here, we describe the synthesis of core-shell nanotube materials made of SWNTs and polystyrene. We developed a two-step strategy that permits to form a stable and homogeneous layer of polymer around the nanotubes by adding first polystyrene via the micelle swelling method and then by locking the structure via radical polymerisation in micelles of styrene and divinylbenzene. After polymerisation and redispersion, the nanotube hybrids can be easily manipulated in solution; they still exhibited photoluminescence properties both in solution and in the solid state demonstrating that the SWNTs embedded in their polystyrene shell are isolated one from each other.4
,5

References

Avouris, P.; Freitag, M.; Perebeinos, V. Nat. Photonics
2008,
2, 341-350.

Godin, A. G.; Varela, J. A.; Gao, Z.; Danné, N.; Dupuis, J. P.; Lounis, B.; Groc, L.; Cognet, L. Nat. Nanotechnol.
2017,
12, 238-243.

He, X.; Htoon, H.; Doorn, S. K.; Pernice, W. H. P.; Pyatkov, F.; Krupke, R.; Jeantet, A.; Chassagneux, Y.; Voisin, C. Nat. Mater.
2018,
17, 663-670.

Orcin-Chaix, L.; Trippé-Allard, G.; Voisin, C.; Okuno, H.; Derycke, V.; Lauret, J.-S.; Campidelli, S. J. Mater. Chem. C
2018,
6, 4786-4792.

Orcin-Chaix, L.; Campidelli, S.; Rondin, L.; Fossard, F.; Bretenaker, F.; Chassagneux, Y.; Voisin, C.; Lauret, J.-S. ACS Appl. Nano Mater.
2020,
3, 7291-7296

Figure 1
Power-Generating Electrochemical Anion Exchange CO2 Separator for Practical AEMFC Application
Authors: Zheng Yiwei , Mustain William 
Published: July 2021

Anion exchange membrane fuel cells (AEMFCs) have been widely touted as a low- cost alternative to existing proton exchange membrane fuel cells. However, one of the limitations of this technology has been the severe performance penalty related to the introduction of CO2 to the cell (typically from air in the cathode feed). A low cost, low energy solution is needed that is able to remove CO2 from the incoming air before it is fed to the AEMFC system.1,2 Many approaches to removing CO2 from the cathode inlet would consume valuable energy and complicate the systems-level balance-of-plant. However, recently3, an electrochemical approach was proposed that i) is able to generate power; and ii) takes advantage of the carbonation phenomena that harms AEMFCs. Such a device can be called an anion exchange CO2 separator (AECS).
An AECS operates on the same principles as an AEMFC. H2 is fed to the anode and O2/air is fed to the cathode. As OH- is formed from the oxygen reduction reaction at the cathode, it is converted to carbonates by reaction with carbon dioxide. The carbonates are transported to the anode by migration where they are eventually released as CO2. Ideally, an AECS operates on waste H2 and a high concentration CO2 stream leaves the anode and an air stream devoid of CO2 leaves the cathode. By design, the AECS is smaller than the primary AEMFC. Because carbonates are present, the AECS operates at a lower power density than the AEMFC, but the method has the promise to use waste to generate energy while removing CO2.
In this work, the effectiveness of an AECS in lowering the CO2 concentration of an incoming stream of 400ppm air is investigated. Several parameters are changed, including the AECS active area and anode flowrate. The primary focus of these experiments was to develop operating conditions that lead to very low ppm CO2 concentrations leaving the AECS cathode. In addition to showing significant CO2 removal, we also show an AECS that operates with a stable output for over 150 h. Finally, AEMFC operation on AECS-purified industrial air is successfully demonstrated.

References

Zheng, T. J. Omasta, X. Peng, L. Wang, J. R. Varcoe, S. Pivovar, and W. E. Mustain, Energy Environ. Sci., 12, 2806–2819 (2019).

R. Gerhardt, L. M. Pant, H.-S. Shiau, and A. Z. Weber, ECS Trans., 86, 15–24 (2018).

Yan, B. Setzler, Y. Zhao, M. S. R. Carbonell, and S. Gottesfeld, U.S. Patent No. 10,811,711. 20 Oct. 2020.