bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Observation of Virtual Electrode Formation By Spectromicroscopy
Authors: Siegel David A , El Gabaly Farid , Bartelt Norman , McCarty Kevin F. 
Published: February 2020

Novel electrochemical solutions to problems in energy storage and transportation can drive renewable energy to become an economically viable alternative to fossil fuels. In many electrochemical systems, the behavior of a device can be fundamentally limited by the surface area of a triple phase boundary, the boundary region where a gas-phase species, electrode, and electrolyte coincide. When the electrode is an ionic insulator the triple phase boundary is typically a one-dimensional boundary with nanometer-scale thickness: ions cannot transport through the electrode, while electrons cannot be transported through the electrolyte.
Here we present direct experimental measurements of a novel electrolyte-to-electrode transition with photoemission electron microscopy, and observe that the surface of an ionically conductive, electronically insulative solid oxide electrolyte undergoes a transition into a mixed electron-ion conductor in the vicinity of a metal electrode. Our direct experimental measurements allow us to characterize this system and address the mechanisms of ionic reactions and transport through comparisons with theoretical modeling to provide us with a physical picture of the processes involved.
Our results provide insight into one of the mechanisms of ion transport in an electrochemical cell that may be generalizable to other systems.
Photocurrent Measurements at Quantum Dot Electrodes for Bioanalytical Applications
Authors: Riedel Marc , Tanne Johannes , Göbel Gero , Parak Wolfgang , Lisdat Fred 
Published: February 2020

Quantum dots (QDs) allow the generation of electron-hole pairs upon illumination. When these particles are fixed to an electrode a photocurrent can be generated. This allows their use as a light-switchable layer on the surface. The QDs can not only exchange electrons with the electrode, but can also show reactions with donor or acceptor compounds in solution. This provides access to the construction of signal chains starting from an analyte molecule to be detected.
The direction and magnitude of the photocurrent depend on several factors such as electrode polarization, solution pH and composition. These defined dependencies have been evaluated with respect to the combination of QD-electrodes with enzyme reactions for sensorial purpose [1,2].
Thus, it has been found that the cofactor of many dehydrogenase-based reactions NADH can be oxidized at the illuminated QDs without applying high potentials. This provides the basis for a coupling strategy with the enzyme glucose dehydrogenase for the analysis of glucose concentrations in solution by photocurrent measurements.
CdSe/ZnS-QD-modified electrodes can also be used to follow enzymatic reactions in solution based on their capability to reduce molecular oxygen while being excited [3]. In order to develop a photoelectrochemical biosensor, glucose oxidase (GOD) is immobilized on the QD-electrode. One immobilization strategy applies the layer-by-layer-technique of GOD and a polyelectrolyte (polyallylamine hydrochloride). Photocurrent measurements of such a sensor show a clear concentration dependent behavior for millimolar glucose concentrations. Sensitivity can be influenced by the enzyme concentration and the number of layers deposited. The principle of combining QD electrodes with a layered protein architecture and light-triggered read-out can also be transferred to other enzymes such sarcosine oxidase and sarcosine detection. The sensing properties of quantum dot electrodes can be significantly influenced by additional nanoparticles giving access to the detection of other substances, but also by immobilizing multiple layers of the QDs.
In another direction of research it can be demonstrated that direct electron transfer from excited quantum dots can be achieved with the redox protein cytochrome c provided the QD surface is properly modified. This allows the detection of the protein in different concentrations and redox states, but also of interaction partners which show a defined reaction with the protein. Examples are the cyt c reduction by superoxide radicals resulting in an anodic photocurrent and the cyt c oxidation by nitrate reductase in the presence of nitrate resulting in a cathodic photocurrent .
[1] Ch. Stoll, S. Kudera, W.J. Parak, F. Lisdat, SMALL 2 (6) (2006) 741-743).
[2] K. Schubert, W. Khalid, Z. Yue, W. Parak, F. Lisdat, Langmuir 26 (2) (2010) 1395-1400
[3] J. Tanne, D. Schäfer, W. Khalid, W. J. Parak, F. Lisdat, Analytical Chemistry 83 (20) (2011) 7778–7785
From Molecular to Nanostructured Carbon Systems By Spectroelectrochemistry
Authors: Iurlo Matteo , Valenti Giovanni , Rapino Stefania , Paolucci Francesco , Marcaccio Massimo 
Published: February 2020

The combination of electrochemistry and spectroscopy techniques has been widely used in different contexts both to complement physical chemical information or gain new data otherwise not so easily obtainable.
Thus, spectroelectrochemistry techniques, since the development in the 60’s of the last century has allowed to investigate the electron transfer processes in molecular systems with an increasing structure complexity as well as the electronic interactions among the various moieties in supramolecular species.1 The appearance of low-dimensional carbon nanostructures, such as nanotubes and graphenes, which represent a very promising class of new materials in the field of nanotechnology, has seen an even more frequent recourse to spectroelectrochemical investigations.2 This family of combined electrochemical and spectroscopy techniques has also been successfully used to develop sensor devices, as well as to study technological applications, as for example in the field of conducting polymers.
In this communication the interesting redox, luminescence and electrochemiluminesce properties of different species spanning from molecular species, mainly coordination complexes, to nanostructured carbon systems (single walled carbon nanotube – SWNT, graphene, planar and curved polycyclic hydrocarbons3) will be discussed together with the fundamental data obtained from the spectroelectrochemical investigations.

References:

1 Stagni, S. et al. Inorg. Chem.
2006, 45, 695.

2 (a) Iurlo, M. et al. Chem. Comm
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3 Valenti, G. et al. J. Phys.
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Solid-State Lead-Selective Electrodes- a New Insight into Measurements of Ions at Low Analyte Concentrations
Authors: Lisak Grzegorz , Ciepiela Filip , Sokalski Tomasz , Harju Leo , Bobacka Johan , Lewenstam Andrzej 
Published: February 2020

In environmental analysis of ions, ion-selective electrodes (ISEs) are frequently investigated as candidates to improve already existing techniques. Potentiometric sensors have several advantages over other analytical techniques, e.g. portability, low energy consumption, and small size. This creates an opportunity to perform analysis at overall lower cost [1, 2]. Despite obvious advantages, ISEs due to the need of re-calibration and fouling are not yet implemented in environmental analysis of ions on an industrial scale [3, 4]. Vast majority or scientific reports dealing with measurements of ions in diluted samples are devoted to solid-contact and conventional (with inner filling solution) ISEs, however, the concept of lowering the detection limit was firstly introduced and studied with solid-state ISEs [5-8].
In this study solid-state membrane electrodes were re-vitalized in measurements of ions at low analyte concentration in environmental samples. We used lead(II)-selective electrodes with PbS/Ag2S membranes to develop two methods lowering of the detection limit based on the concentration time-dependent adsorption of the primary ion on the surface of the membrane [9] and tuned galvanostatic polarization (chronopotentiometry) [10]. Furthermore, solid-state electrodes were used to determine lead concentration in environmental sample. Tuned galvanostatic polarization method was found suitable in measurement of lead(II) in environmental samples collected nearby industrially exposed terrain [11]. The chronopotentiometric determination was compared to the analysis done with inductively coupled plasma mass spectrometry (ICP-MS) and differential pulse anodic stripping voltammetry (DPASV). The tuned galvanostatic polarization method for the determination of lead in environmental sample was employed in our study for the very first time. By this application we open a new important direction for electrochemical measurement of ions at low analyte concentrations.
References:

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G. Lisak, F. Ciepiela, J. Bobacka, T. Sokalski, L. Harju, A. Lewenstam, Electroanalysis 25 (2013) 123.
Effects of Stress and State-of-Charge on Lithium Transport Behavior in Silicon Electrodes
Authors: Pan Jie , Cheng Yang-Tse , Beck Matthew J 
Published: February 2020

In recent years, silicon (Si) has been proposed as a promising negative electrode material because of its high specific capacity, low discharge voltage, and abundance. However, the large volume change and high stress during lithiation and de-lithiation of Si1-3, which can lead to cracking and severe degradation, are impeding the commercialization of Si-based electrodes. Furthermore, Li-ion transport behavior, which affects stress generation4 and rate performance of the electrode, must be understood in order to design Si electrodes with improved performance.
In this study, we investigated the transport mechanism of Li in both crystalline and amorphous lithiated Si in the framework of Density Functional Theory as implemented in the Vienna ab initio Simulation Package (VASP)5, 6. The effects of stress/strain and state-of-charge (SOC) on ionic transport were examined. In the study of crystalline phases, we used the Climbing Nudged Elastic Band (CNEB) method to estimate the diffusion barrier for several possible diffusion paths. We prepared amorphous Li-Si systems (Figure 1) by simulated annealing within ab initio Molecular Dynamics (AIMD). We used the Stokes-Einstein relationship7 to obtain diffusion coefficients from AIMD trajectories (Figure 2).
We found that, in crystalline Li-Si alloys, the interstitial diffusion barrier of Li-ion increases monotonically as the system is compressed. However, in amorphous systems, the effect of stress is not monotonic. One possible mechanism of the non-monotonic behavior is the change of local structure, such as the coordination number, in the amorphous Li-Si alloys as a function of stress. From the view of activation volume, this behavior could be explained by the factor that the activation volume due to Li-ion migration is negative in amorphous Li-Si structures. In addition, we investigated the effects of SOC on Li-ion transport using AIMD calculations and Darken’s equation for chemical diffusion. This study provides new insights into the effects of stress and composition on lithium transport in Si.

References:

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7. J. R. Chelikowsky, J. J. Derby, V. V. Godlevsky, M. Jain and J. Y. Raty, Journal Of Physics-Condensed Matter 13 (41), R817-R854 (2001).
Invited Presentation: Optical Properties of Carbon Nanotube/Chromophores Assemblies
Authors: Vialla Fabien , Delport Géraud , Langlois Benjamin , Filoramo Arianna , Deleporte Emmanuelle , Campidelli Stéphane , Voisin Christophe , Lauret Jean-Sébastien 
Published: February 2020

The delocalized π-electronic system of carbon nanotubes allows them to link non-covalently to a lot of different organic molecules. In contrast to covalent functionalization, this weak interaction preserves most of the nanotubes intrinsic properties (photoluminescence or mobility for instance) but still leads to a strong enough coupling so as to give stable compounds and to induce new and efficient functionalities [1, 2]. We focus on nanotubes / chromophores compounds where the latter acts as an optical nano antenna that absorbs light and transfers its energy to the nanotube, allowing a uniform excitation of all the chiral species in the sample [3, 4, 5, 6, 7].
In this presentation, we will focus on the latest developments of our research in this topic.
References:
[1] C. Roquelet, et al, ChemPhysChem 2010, 11, 1667
[2] G. Clave et al, Chem. Mat. 2013, 25, 2700
[3] G. Magadur et al. ChemPhysChem 2008, 9, 1250
[4] C. Roquelet, et al, Appl. Phys. Lett. 2010, 97,141918
[5] D. Garrot et al, J. Phys. Chem C 2011, 115, 23283
[6] C. Roquelet et al, ACS Nano 2012, 6, 8796)
[7] F. Vialla et al, Phys. Rev. Lett. 2013, 111, 137402
Carbon Nanotube Computer: Transforming Scientific Discoveries into Working Systems
Authors: Shulaker Max , Hills Gage , Patil Nishant , Wei Hai , Chen Hong-Yu , Wong H.-S. Philip , Mitra Subhasish 
Published: February 2020

The miniaturization of electronic devices has been the principal driving force behind the semiconductor industry, and has brought about major improvements in computational power and energy efficiency. Although advances with silicon-based electronics continue to be made, alternative technologies are being explored. Digital circuits based on transistors fabricated from carbon nanotubes (CNTs) have the potential to outperform silicon by improving the energy– delay product, a metric of energy efficiency, by more than an order of magnitude. Hence, CNTs are an exciting complement to existing semiconductor technologies. However, carbon nanotubes (CNTs) are subject to substantial inherent imperfections that pose major obstacles to the design of robust and very large-scale CNFET digital systems:
• It is nearly impossible to guarantee perfect alignment and positioning of all CNTs. This limitation introduces stray conducting paths, resulting in incorrect circuit functionality.
• CNTs can be metallic or semiconducting depending on chirality. Metallic CNTs cause shorts resulting in excessive leakage and incorrect circuit functionality.
A combination of design and processing technique overcomes these challenges by creating robust CNFET digital circuits that are immune to these inherent imperfections. This imperfection-immune design paradigm enables the first experimental demonstration of the carbon nanotube computer, and, more generally, arbitrary digital systems that can be built using CNFETs. The CNT computer is capable of performing multitasking: as a demonstration, we perform counting and integer-sorting simultaneously. In addition, we emulate 20 different instructions from the commercial MIPS instruction set to demonstrate the generality of our CNT computer. This is the most complex carbon-based electronic system yet demonstrated. It is a considerable advance because CNTs are prominent among a variety of emerging technologies that are being considered for the next generation of highly energy-efficient electronic systems.
Relative Populations of Non-Isomeric Metallofullerenes: La@C76(Td) Vs. La2@C76(Cs,17490)
Authors: Slanina Zdenek , Lee Shyi-Long , Nagase Shigeru , Akasaka Takeshi 
Published: February 2020

Very recently, a new member of the lanthanum-containing metallofullerene family has been isolated and its structure determined from X-ray crystallographic analysis, namely [1] La2@C76(Cs,17490), even with two pairs of connected pentagons, hence violating the isolated-pentagon rule (IPR). In order to explain the interesting observation, a computational treatment is suggested for evaluations of the relative populations of non-isomeric metallofullerenes. As a comparative reference structure, the most stable La@C76 isomer is selected - the IPR-C76(Td)-cage based endohedral La@C76(Td). It is found that in the relevant temperature region the La2@C76(Cs,17490) species should be considerably more populated compared to La@C76(Td). The new computational stability treatment is applicable to a wider spectrum of non-isomeric metallofullerenes.
[1] M. Suzuki, N. Mizorogi, T. Yang, F. Uhlik, Z. Slanina, X. Zhao, M. Yamada, Y. Maeda, T. Hasegawa, S. Nagase, X. Lu, T. Akasaka, Chem. Eur. J. 19, doi:10.1002/chem.201302821 (2013).
Synthesis, Characterization, and Unusual Behavior of a Perfluoroarylated Fullerene
Authors: San Long K. , Whitaker James B. , Popov Alexey A. , Strauss Steven H. , Boltalina Olga V. 
Published: February 2020

Fullerenes and fullerene derivatives have attracted much attention due to their interesting optical and electronic properties. For example, further chemical elaborations of fullerenes possessing cyclo‐adducts (ie., phenyl‐C61‐butyric acid methyl ester, PCBM,1 and mono‐indene-C60, ICMA2) have shown promising use in photovoltaic energy conversion. Mono‐hydrofullerenes, C60RH, were shown as effective synthons for novel molecules3 with interesting physicochemical properties for various applications. The C‒H bond activation utilizing the acidic fullerenyl C60‒H proton can be realized by the use of strong bases. For instance, the dimerization of two RC60· radicals using NaOH in the presence of C60RH was used to form RC60‒C60R.4

In this work, we use the labile hydrogen atom on C60RH as a synthetic handle for further chemical elaborations, resulting in a novel perfluoroarylfullerene. One such product, a "fullerene-with-a-mohawk," was realized by the use of a base or by an one‐electron reductant. Products were characterized by 19F and 1H NMR spectroscopy, mass spectrometry, cyclic voltammetry, X‐ray crystallography, and DFT calculations.

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Preparation of Graphene Fibers
Authors: He Yijia 
Published: February 2020

Graphene owns intriguing properties in electronic, thermal, and mechanic with unique two-dimension (2D) monolayer structure. The new member of carbon family has not only attracted great attentions in scientific research, but also showed great potential for many applications. Graphene sheets can self-assemble into macroscopic structures, which is conducive to further explore the value of graphene material in application, and also the future major trends.
This dissertation introduces the preparation of graphene fiber by graphene oxide solution as spinning dope. The graphene oxide is selected to solve the poor wettability of graphene hindering its direct wet spinning. The oxygen-containing groups on graphene oxide surface make it hydrophilic. The graphene fibers were prepared in the following steps: Firstly assemble the graphene oxide into graphene oxide fibers by wet spinning; then turning the graphene oxide fibers into graphene fibers by thermal reduction. To observe the graphene oxide immersing in the coagulation bath at different times by SEM and the assembly mechanism of macroscopic graphene oxide fibers could be studied. In this work, the conductivity of the graphene fibers have been measured using the four-point method. Single mast mechanics test system was used for the tensile strength of graphene fibers. So the key process factors in graphene fibers preparation were explored and optimized, including the concentration of wet spinning dope, the composition of the coagulation bath, the change in diameter of the needles, injection rate and collection rate, etc.
In summary, graphene oxide fibers were assembled by wet-spinning of the graphene oxide dope. And by the thermal reduction graphene fibers were prepared successfully. After studying the assembly mechanism of graphene fibers, the better raw materials and the more proper preparation conditions were chosen to make the fibers which have the superior performances.
Photovoltaic Properties of Organic Heterojunctions with Ordered Nanostructures Prepared By Anodic Porous Alumina
Authors: Masuda Hideki , Kondo Toshiaki , Yanagishita Takashi , Nishio Kazuyuki 
Published: February 2020

Organic thin film solar cells have attracted much attention as a next generation energy conversion devices due to their unique properties [1-3]. Control of the nanostructures of organic heterojunctions is essential to improve the conversion efficiency of the organic solar cells. In the present report, we describe the fabrication of the organic solar cells with controlled nanostructures and their photovoltaic properties. Fabrication of organic heterojunctions with controlled geometrical nanostructures was carried out by using the substrates with ordered textured patterns of nanometer scale, which were prepared by nanoimprinting using anodic porous alumina molds. Anodic porous alumina, which is formed by anodization of Al in acidic electrolyte, is a typical self-ordered material and is promising candidate for the starting material for making nanostructures [4]. Use of anodic porous alumina as a mold for nanoimprinting allows the high throughput formation of the substrates with ordered nanostructures of polymers [5,6]. The heterojunctions of organic thin layers were formed on the substrates with ITO layer using a vacuum deposition apparatus. The ordered nanostructure of the substrates could be maintained even at the organic layer of heterojunctions. Optical properties of the obtained samples and the photovoltaic properties were examined. In the samples with controlled geometrical structures prepared by the present processes, improvement of conversion efficiencies was confirmed compared to the samples without controlled geometrical structures. This improvement was thought to be caused by the increase of absorption of light at the heterojunctions due to the antireflection effect caused by the periodic nanostructures. The controlled nanostructure of the heterojunction also contributed to the improvement of the conversion efficiency due to the effective charge separation at the junction. The present process, which allows high throughput formation of the organic heterojunctions with controlled geometrical structures, will be used for the formation of organic solar cells with high conversion efficiencies.
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