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Photoswitchable organic field-effect transistors (OFETs) with embedded photochromic materials are considered as a promising platform for development of organic optical memory devices. Unfortunately, the operational mechanism of these devices and guidelines for selection of light-sensitive materials are still poorly explored. In the present work, a series of photochromic dihetarylethenes with a cyclopentenone bridge moiety were investigated as a dielectric/semiconductor interlayer in the structure of photoswitchable OFETs. It was shown that the electrical performance and stability of the devices can be tuned by variation of the substituents in the structure of the photochromic material. In particular, it was found that dihetarylethenes with donor substituents demonstrated the best light-induced switching effects (wider memory windows and higher switching coefficients) in the devices. The operation mechanism of the light-triggered memory devices was proposed based on the differential in situFourier transform infrared (FTIR) spectroscopy data and regression analysis of the threshold voltage–programming time experimental dependencies. The established relationships will facilitate further rational design of new photochromic materials, thus paving a way to fast and durable organic optical memories and memory transistors (memristors).

Electrochemical self-assembly (ESA) of CuSCN/4-cyano-4'-(N'-methyl)stilbazolium (CNS+) hybrid thin films has been performed and analyzed in comparison with CuSCN/4-(N,N-dimethylamino)-4'-(N'-methyl)stilbazolium (DAS+) hybrid system. Due to the presence of strongly electron-withdrawing -CN group, CNS+has a much higher dipole moment than DAS+to exhibit stronger affinity to CuSCN. CNS+therefore gave strong impact to the crystal growth of CuSCN with its smaller concentration than DAS+, such as changing crystal orientation, creating unique nanostructure and phase transition from ?- to ?-CuSCN. CNS+has been found to obey the same mechanism as DAS+for its loading into the film. The limit for diffusion limited loading was pushed up to its bulk concentration of 200 ?mol dm-3, much higher than that for DAS+(60 ?mol dm-3). Also, the efficiency of dye uptake in the surface reaction limited loading was enhanced about 3 times due to the improved stability of CuSCN/CNS surface complex.

Most interface materials for organic solar cells (OSCs) were originally optimized for fullerene-based systems and are now being adapted for non-fullerene acceptor (NFA) based solar cells. This reliance on established interface materials results in a limited choice of interface materials for NFA based OSCs. For vacuum processed organic devices, the concept of doped interface materials is exceptionally successful, but has not yet been translated to modern NFA based devices due to solution processing constraints requiring orthogonal solubility. Herein, we report a novel concept for the development of solution-processed HTL in inverted n-i-p architecture OSCs using doped organic nanoparticles (D-NPs), overcoming solvent compatibility limitations and enabling scalable production processes. We demonstrate that the functional key interface properties of D-NPs HTLs can be tailored independently over a wide regime. Specifically, conductivity and work function can be optimized separately by varying the dopant concentration and the material system. By using D-NPs as HTL in the n-i-p architecture, power conversion efficiencies (PCE) of over 12 % are achieved for PM6:Y6 based devices. The D-NPs HTL concept is successfully applied to a variety of organic semiconductors used in photovoltaics and opens a new class of tailorable interface materials for solution-processed HTL materials.

Lakes are conduits of greenhouse gases to the atmosphere; however, most efflux estimates for individual lakes are based on extrapolations from a limited number of locations. Within‐lake variability in carbon dioxide (CO2) and methane (CH4) arises from differences in water sources, mixing, atmospheric exchange, and biogeochemical transformations, all of which vary across multiple temporal and spatial scales. We asked, how variable are CO2and CH4across the surface of a single lake, how do spatial patterns change seasonally, and how well does the typical sampling location represent the entire lake surface? During the 2016 ice‐free period, we mapped surface water concentrations of CO2and CH4approximately weekly in Lake Mendota (USA) and modeled diffusive gas exchange. During stratification, CO2was generally lower than atmospheric saturation (mean 19.81 μM) and relatively homogenous (mean coefficient of variation 0.12), whereas CH4was routinely extremely supersaturated (mean 0.29 μM) with greater spatial heterogeneity (mean coefficient of variation 0.65). During fall mixis, concentrations of both gases increased and became more spatially variable, but their spatial arrangements differed. In this system, samples collected from the lake center reasonably well represented the spatially weighted mean CO2concentration but overestimated annual CO2efflux by 21%. For CH4, the lake center underestimated annual diffusive efflux by only 8.6% but poorly represented lakewide concentrations and fluxes on any given day. Upscaling from a single site to the whole lake requires consideration of spatial variation to assess lakewide carbon dynamics due to heterogeneity in within‐lake processing, transport to the lake surface, and exchange with the atmosphere. Numerous physical, chemical, and biological properties vary across the surface of individual lakes. However, researchers frequently use the lake center to represent the entire lake and ignore spatial heterogeneity. Using a boat‐mounted sampling system, we mapped carbon dioxide and methane across the surface of Lake Mendota 26 times spanning the entire ice‐free season. We described the progression of each gas's spatial pattern and evaluated the consequences of using only the lake center to calculate emissions to the atmosphere. The lake surface alternated between periods of relative uniformity to periods or remarkable spatial heterogeneity, and the spatial patterns of the two gases did not always align. At the annual scale, samples at the lake center overestimated lakewide carbon dioxide efflux and underestimated methane efflux. These results have consequences for our understanding of lake carbon cycling and the contribution of lakes to atmospheric greenhouse gas budgets. Concentrations of carbon dioxide and methane in Lake Mendota varied through time and across the lake surfaceEfflux estimates at the lake center overestimated lakewide carbon dioxide emissions and underestimated methane emissions to the atmosphereUpscaling concentrations, fluxes, and gas transfer velocities from point samples to whole lakes requires consideration of spatial variability

In order to realize sustainable renewable energy supply, large-scale energy storage system is needed to overcome the problem of intermittency of power generation. Vanadium redox flow battery (VRFB) presents the most viable solution but faces the problem of high material cost. In this study, we have established a cost-effective process to prepare vanadium electrolyte for VRFB from an untouched industrial waste, ammonia slag, by pH control under atmospheric condition (< 95degC). The extracted solution changed color during electrolytic reduction as yellow, blue, dark green and purple, matched with the colors of V5+, V4+, V3+, and V2+, respectively, indicating accurate change of the valences without forming precipitates. Electrolyte prepared from the recycled vanadium showed almost the same charging/discharging performances as the one prepared from commercial V2O5 reagent battery tests during the first several cycles, but degraded rapidly after 16 cycles, caused by impurities that deactivate the negative electrode for the reduction of V3+ to V2+. The miniature VRFB prototype built by employing 3D printing technique showed a much higher performance than the H-cell, indicating the flow cell configuration could help to push up the diffusion limit of vanadium redox by flowing the electrolyte solution through the electrodes, as well as reducing IR loss and water splitting to increase the efficiency.

Microwave-assisted hydrothermal reaction has successfully achieved synthesis of Co-doped ZnO nanocrystals at a low reaction temperature of 160oC and in a short reaction time of 30 min. Partial replacement of 4-coordinated Zn(II) ions of ZnO with Co(II) ions up to about 10at% has been suggested from evaluation of the products by UV-Vis absorption spectra, morphological observations and X-ray diffraction. The higher addition of Co resulted in its phase-separated precipitation as Co(OH)2. While mesoporous electrode processed from ZnO nanocrystals was totally inactive for water oxidation, that of Co-doped ZnO exhibited a good catalytic activity to achieve about 1 mA cm-2 current of oxygen evolution reaction (OER) with an overvoltage of 0.545 V in a neutral aqueous KCl solution, which in fact was far superior to a Co3O4 electrode known to suffer from its limited conductivity. The doped Co ions are only expected to act as reaction centers for charge transfer on the very surface in contact with the electrolyte, while ZnO acts as a highly conductive and chemically stable host matrix to support the catalyst. Doping of transition metals into ZnO by the present method thus provides a new strategy to obtain sustainable OER catalysts from earth-abundant elements for conversion and storage of renewable electricity.

In order to realize sustainable renewable energy supply, large-scale energy storage system is needed to overcome the problem of intermittency of power generation. Vanadium redox flow battery (VRFB) presents the most viable solution but faces the problem of high material cost. In this study, we have established a cost-effective process to prepare vanadium electrolyte for VRFB from an untouched industrial waste, ammonia slag, by pH control under atmospheric condition (< 95degC). The extracted solution changed color during electrolytic reduction as yellow, blue, dark green and purple, matched with the color of V5+, V4+, V3+, and V2+, respectively, indicating accurate change of the valences without forming precipitates. Electrolyte prepared from the recycled vanadium showed almost the same charging/discharging performances as the one prepared from commercial V2O5 reagent in in battery tests. The miniature VRFB prototype built by employing 3D printing technique showed a much higher performance than the H-cell, indicating the flow cell configuration could help to push up the diffusion limit of vanadium redox by flowing the electrolyte solution through the electrodes, as well as reducing IR loss and water splitting to increase the efficiency.

Electrochemical self-assembly of CuSCN/4-(N,N-dimethylamino)-4'-(N'-methyl)stilbazolium (DAS) hybrid thin films has been carried out on systematic variation of bulk concentrations of [Cu(SCN)]+, DAS tosylate (DAST) and changing their flux density by angular speed of rotation of the rotating disk electrode. Switching of DAS loading mechanism dependent on the DAST concentration in the bath has been verified and quantified. The switching occurs at the concentration ratio [Cu(SCN)]+/DAST = ca. 40, above which the loading becomes diffusion limited for DAS to be occluded in the CuSCN grains, whereas the second order reaction rate of complex formation between CuSCN surface sites and DAS begins to limit the DAS loading when the relative concentration of DAST exceeds this border, resulting in a phase-separated precipitation of CuSCN and (DAS)(SCN) aggregate in unique nanostructures.

Nanostructured hybrid thin films of crystalline CuSCN and fluorescent cationic dyes; Rhodamine B (RB), Nile Blue A (NB) and 4-(N,N-dimethylamino)-4'-(N'-methyl)stilbazolium (DAS) were obtained by electrochemical self-assembly from a single pot containing all the chemical ingredients. Concerted functionalities achieved by the intimate interaction between CuSCN and dye was studied for photoluminescence (PL) behavior between 77 and 298 K. PL from RB and NB was totally quenched when they were hybridized with CuSCN, due to hole transfer from the dye excited state to the valence band of CuSCN, potentially indicating their use as light absorber in solar cells and photodiodes. On the contrary, that of DAS was not quenched despite of its favorable HOMO position for the hole transfer. Crystalline DAS salt with tosylate (DAST) exhibited a strong exciton-phonon coupling to weaken, broaden and red-shift PL at room temperature, so that it inversely is strongly enhanced, sharpened and blue-shifted at 77 K. The PL of the same chromophore in the hybrid thin film, however, shows a slight red-shift and only moderate enhancement at reduced temperature, due to exciton stabilization and energy transfer from CuSCN to DAS luminophore, making it a unique nearly temperature-independent luminescent material.

Electrochemical reduction of carbon dioxide (CO2RR) to formate provides an avenue to the synthesis of value-added carbon-based fuels and feedstocks powered using renewable electricity. Here, we hypothesized that the presence of sulfur atoms in the catalyst surface could promote undercoordinated sites, and thereby improve the electrochemical reduction of CO2to formate. We explored, using density functional theory, how the incorporation of sulfur into tin may favor formate generation. We used atomic layer deposition of SnSxfollowed by a reduction process to synthesize sulfur-modulated tin (Sn(S)) catalysts. X-ray absorption near-edge structure (XANES) studies reveal higher oxidation states in Sn(S) compared with that of tin in Sn nanoparticles. Sn(S)/Au accelerates CO2RR at geometric current densities of 55 mA cm−2at −0.75 V versus reversible hydrogen electrode with a Faradaic efficiency of 93%. Furthermore, Sn(S) catalysts show excellent stability without deactivation (<2% productivity change) following more than 40 hours of operation.

AbstractCarbon dioxide (CO2) emissions from rivers and other inland waters are thought to be a major component of regional and global carbon cycling. In large managed rivers such as the Columbia River, contemporary ecosystem changes such as damming, nutrient enrichment, and increased water residence times may lead to reduced CO2concentrations (and emissions) due to increased primary production, as has been shown in another large North American river (Upper Mississippi). In this work, spatial patterns of water quality, including dissolved CO2concentrations, were assessed in the Lower Columbia River (LCR) and major tributaries using underway measurements from a small research vessel during July 2016. We observed near-equilibrium CO2conditions and overall weak supersaturation of CO2in the main channel (average 133.8% saturation) and tributaries. We observed only weak correlations between CO2saturation, chlorophyll afluorescence, and turbidity, thus not strongly supporting our hypothesis of primary productivity controls. In general, the LCR was clear (low turbidity, mean = 1.48 FNU) and had low chlorophyll fluorescence (mean = 0.177 RFU) during the sampling period. As a whole, the LCR was homogeneous with respect to biogeochemical conditions and showed low spatial variability at >100 km scales. Overall, we find that the LCR is likely a weak summertime source of CO2to the atmosphere, in line with findings from other altered rivers such as the Upper Mississippi.

The current study reports the application of chalcopyrite semiconductor CuInS2(CIS) nanofibers for the reduction of CO2to CO with a remarkable Faradaic efficiency of 77 ± 4%. Initially the synthesis of CuInS2nanofibers was carried out by adaptable electrospinning technique. To reduce the imperfection in the crystalline fiber, polyacrylonitrile (PAN) was selected as template polymer. Afterward, the desired chemical structure of nanofibers was achieved through sulfurization process. Making continuous CuInS2nanofibers on the cathode surface by the electrospinning method brings the advantages of being economical, environmentally safe, and versatile. The obtained nanofibers of well investigated size and diameter according to the SEM (scanning electron microscope) were used in electrochemical studies. An improvement of Faradaic efficiency was achieved with the catalytic active CuInS2in nanofibrous structure as compared to the solution processed CuInS2. This underlines the important effect of the electrode fabrication on the catalytic performance. Being less contaminated as compared to solution processing, and having a well-defined composition and increased catalytically active area, the CuInS2nanofiber electrodes prepared by the electrospinning technique show a 4 times higher Faradaic efficiency. Furthermore, in this study, attention was paid to the stability of the CuInS2nanofiber electrodes. The electrochemical reduction of CO2to CO by using CIS nanofibers coated onto FTO electrodes was carried out for 10 h in total. The observed current density of 0.22 mA cm–2and the stability of CIS nanofiber electrodes are found to be competitive with other heterogeneous electrocatalysts. Hence, we believe that the fabrication and application of nanofibrous materials through the electrospinning technique might be of interest for electrocatalytic studies in CO2reduction.

Organic microboxes composed of charge-transfer molecule (HB194) were prepared by the reprecipitation method. HB194 dissolved in an organic solvent was rapidly injected into water to produce nanoparticles. Nanoparticles prepared from organic solvents containing the carbonyl group were recrystallized in a dispersion to form microboxes. TiO2nanoparticles were loaded inside the microboxes to produce TiO2@HB194 hybrid microboxes.Organic microbox composed of charge-transfer molecule (HB194) was prepared by reprecipitation method. HB194 dissolved in organic solvent was rapidly injected to a water to produce nanoparticles. Nanoparticles prepared from organic solvents containing carbonyl group were recrystallized in a dispersion to form a microbox. TiO2nanoparticles were loaded inside the microbox to produce TiO2@HB194 hybrid microbox.

Field-effect transistors have been widely used to study electronic transport and doping in colloidal quantum dot solids to great effect. However, the full power of these devices to elucidate the electronic structure of materials has yet to be harnessed. Here, we deploy nanodielectric field-effect transistors to map the energy landscape within the band gap of a colloidal quantum dot solid. We exploit the self-limiting nature of the potentiostatic anodization growth mode to produce the thinnest usable gate dielectric, subject to our voltage breakdown requirements defined by the Fermi sweep range of interest. Lead sulfide colloidal quantum dots are applied as the active region and are treated with varying solvents and ligands. In an analysis complementary to the mobility trends commonly extracted from field-effect transistor studies, we focus instead on the subthreshold regime and map out the density of trap states in these nanocrystal films. The findings point to the importance of comprehensively mapping the electronic band- and gap-structure within real quantum solids, and they suggest a new focus in investigating quantum dot solids with an aim toward improving optoelectronic device performance.

We present a frameworkvalidated using both modeling and experimentto predict doping in CQD films. In the ionic semiconductors widely deployed in CQD films, the framework reduces to a simple accounting of the contributions of the oxidation state of each constituent, including both inorganic species and organic ligands. We use density functional theory simulations to confirm that the type of doping can be reliably predicted based on the overall stoichiometry of the CQDs, largely independent of microscopic geometrical bonding configurations. Studies employing field-effect transistors constructed from CQDs that have undergone various chemical treatments, coupled with Rutherford backscattering and X-ray photoelectron spectroscopy to provide compositional analysis, allow us to test and confirm the proposed model in an experimental framework. We investigate both p- and n-type electronic doping spanning a wide range of carrier concentrations from 1016cm–3to over 1018cm–3, and demonstrate reversible switching between p- and n-type doping by changing the CQD stoichiometry. We show that the summation of the contributions from all cations and anions within the film can be used to predict accurately the majority carrier type. The findings enable predictable control over majority carrier concentration viatuning of the overall stoichiometry.

In order to realize sustainable renewable energy supply, large-scale energy storage system is needed to overcome the problem of intermittency of power generation. Vanadium redox flow battery (VRFB) presents the most viable solution but faces the problem of high material cost. In this study, we have established a cost-effective process to prepare vanadium electrolyte for VRFB from an untouched industrial waste, ammonia slag, by pH control under atmospheric condition (< 95°C). The extracted solution changed color during electrolytic reduction as yellow, blue, dark green and purple, matched with the colors of V5+, V4+, V3+, and V2+, respectively, indicating accurate change of the valences without forming precipitates. Electrolyte prepared from the recycled vanadium showed almost the same charging/discharging performances as the one prepared from commercial V2O5reagent battery tests during the first several cycles, but degraded rapidly after 16 cycles, caused by impurities that deactivate the negative electrode for the reduction of V3+to V2+. The miniature VRFB prototype built by employing 3D printing technique showed a much higher performance than the H-cell, indicating the flow cell configuration could help to push up the diffusion limit of vanadium redox by flowing the electrolyte solution through the electrodes, as well as reducing IR loss and water splitting to increase the efficiency.

Microwave-assisted hydrothermal reaction has successfully achieved synthesis of Co-doped ZnO nanocrystals at a low reaction temperature of 160ºC and in a short reaction time of 30 min. Partial replacement of 4-coordinated Zn(II) ions of ZnO with Co(II) ions up to about 10at% has been suggested from evaluation of the products by UV-Vis absorption spectra, morphological observations and X-ray diffraction. The higher addition of Co resulted in its phase-separated precipitation as Co(OH)2. While mesoporous electrode processed from ZnO nanocrystals was totally inactive for water oxidation, that of Co-doped ZnO exhibited a good catalytic activity to achieve about 1 mA cm-2current of oxygen evolution reaction (OER) with an overvoltage of 0.545 V in a neutral aqueous KCl solution, which in fact was far superior to a Co3O4electrode known to suffer from its limited conductivity. The doped Co ions are only expected to act as reaction centers for charge transfer on the very surface in contact with the electrolyte, while ZnO acts as a highly conductive and chemically stable host matrix to support the catalyst. Doping of transition metals into ZnO by the present method thus provides a new strategy to obtain sustainable OER catalysts from earth-abundant elements for conversion and storage of renewable electricity.

In order to realize sustainable renewable energy supply, large-scale energy storage system is needed to overcome the problem of intermittency of power generation. Vanadium redox flow battery (VRFB) presents the most viable solution but faces the problem of high material cost. In this study, we have established a cost-effective process to prepare vanadium electrolyte for VRFB from an untouched industrial waste, ammonia slag, by pH control under atmospheric condition (< 95°C). The extracted solution changed color during electrolytic reduction as yellow, blue, dark green and purple, matched with the color of V5+, V4+, V3+, and V2+, respectively, indicating accurate change of the valences without forming precipitates. Electrolyte prepared from the recycled vanadium showed almost the same charging/discharging performances as the one prepared from commercial V2O5reagent in in battery tests. The miniature VRFB prototype built by employing 3D printing technique showed a much higher performance than the H-cell, indicating the flow cell configuration could help to push up the diffusion limit of vanadium redox by flowing the electrolyte solution through the electrodes, as well as reducing IR loss and water splitting to increase the efficiency.

Electrochemical self-assembly of CuSCN/4-(N,N-dimethylamino)-4’-(N’-methyl)stilbazolium (DAS) hybrid thin films has been carried out on systematic variation of bulk concentrations of [Cu(SCN)]+, DAS tosylate (DAST) and changing their flux density by angular speed of rotation of the rotating disk electrode. Switching of DAS loading mechanism dependent on the DAST concentration in the bath has been verified and quantified. The switching occurs at the concentration ratio [Cu(SCN)]+/DAST = ca. 40, above which the loading becomes diffusion limited for DAS to be occluded in the CuSCN grains, whereas the second order reaction rate of complex formation between CuSCN surface sites and DAS begins to limit the DAS loading when the relative concentration of DAST exceeds this border, resulting in a phase-separated precipitation of CuSCN and (DAS)(SCN) aggregate in unique nanostructures.

Nanostructured hybrid thin films of crystalline CuSCN and fluorescent cationic dyes; Rhodamine B (RB), Nile Blue A (NB) and 4-(N,N-dimethylamino)-4’-(N’-methyl)stilbazolium (DAS) were obtained by electrochemical self-assembly from a single pot containing all the chemical ingredients. Concerted functionalities achieved by the intimate interaction between CuSCN and dye was studied for photoluminescence (PL) behavior between 77 and 298 K. PL from RB and NB was totally quenched when they were hybridized with CuSCN, due to hole transfer from the dye excited state to the valence band of CuSCN, potentially indicating their use as light absorber in solar cells and photodiodes. On the contrary, that of DAS was not quenched despite of its favorable HOMO position for the hole transfer. Crystalline DAS salt with tosylate (DAST) exhibited a strong exciton-phonon coupling to weaken, broaden and red-shift PL at room temperature, so that it inversely is strongly enhanced, sharpened and blue-shifted at 77 K. The PL of the same chromophore in the hybrid thin film, however, shows a slight red-shift and only moderate enhancement at reduced temperature, due to exciton stabilization and energy transfer from CuSCN to DAS luminophore, making it a unique nearly temperature-independent luminescent material.