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Thin-film organic photovoltaic (OPV) devices represent an attractive alternative to conventional silicon solar cells due to their lightweight, flexibility, and low cost. However, the relatively low optical absorption of the OPV active layers still represents an open issue in view of efficient devices that cannot be addressed by adopting conventional light coupling strategies derived from thick PV absorbers. The light coupling to thin-film solar cells can be boosted by nanostructuring the device interfaces at the subwavelength scale. Here, we demonstrate broadband and omnidirectional photon harvesting in thin-film OPV devices enabled by highly ordered one-dimensional (1D) arrays of nanogrooves. Laser interference lithography, in combination with reactive ion etching (RIE), provides the controlled tailoring of the height and periodicity of the silica grooves, enabling effective tuning of the anti-reflection properties in the active organic layer (PTB7:PCBM). With this strategy, we demonstrate a strong enhancement of the optical absorption, as high as 19% with respect to a flat device, over a broadband visible and near-infrared spectrum. The OPV device supported on these optimized nanogrooved substrates yields a 14% increase in short-circuit current over the corresponding flat device, highlighting the potential of this large-scale light-harvesting strategy in the broader context of thin-film technologies.

Currently, energy-efficient electrocatalytic oxygen evolution from water involves the use of noble metal oxides. Here, we show that highly p-conducting zinc cobaltite spinel Zn1.2Co1.8O3.5 offers an enhanced electrocatalytic activity for oxygen evolution. We refer to previous studies on sputtered Zn–Co spinels with optimized conductivity for implementation as (p-type) transparent conducting oxides. Based on that, we manufacture off-stoichiometric conducting p-spinel catalytic anodes on tetragonal Ti, Au–Ti and hexagonal Al-doped ZnO carriers and report the evolution of O2 at Tafel slopes between 40.5 and 48 mV dec−1 and at overpotentials between 0.35 and 0.43 V (at 10 mA cm−2). The anodic stability, i.e., 50 h of continuous O2 electrolysis in 1 M KOH, suggests that increasing the conductivity is advantageous for electrolysis, particularly for reducing the ohmic losses and ensuring activity across the entire surface. We conclude by pointing out the merits of improving p-doping in Zn–Co spinels by optimized growth on a tetragonal Ti-carrier and their application as dimension-stable 3d-metal anodes., Zinc cobaltite spinels show enhanced electrocatalytic activity for oxygen evolution. The spinels evolve O2 at Tafel slopes between 40.5 and 48 mV dec−1 and at overpotentials between 0.35 and 0.43 V at 10 mA cm−2. Their stability underlines their utility as 3d-metal anodes.

To facilitate the prompt management of public health risks from water resources, the fluorescence-based detection of the enzymatic activity of β- d -glucuronidase (GLUC) has been suggested as a rapid method to monitor fecal pollution. New technological adaptations enable now its automated, near-real-time measurement in a robust and analytically precise manner. Large data sets of high temporal or spatial resolution have been reported from a variety of freshwater resources, demonstrating the great potential of this automated method. However, the fecal indication capacity of GLUC activity and the potential link to health risk is still unclear, presenting considerable limitations. This review provides a critical evaluation of automated, online GLUC-based methods (and alternatives) and defines open questions to be solved before the method can fully support water management.

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 situ Fourier 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 β- to α-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 μmol dm-3, much higher than that for DAS+ (60 μmol 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.

Electrocatalytic CO2-to-CO conversion represents one pathway to upgrade CO2 to a feedstock for both fuels and chemicals (CO, deployed in ensuing Fischer–Tropsch or bioupgrading). It necessitates se...

Conducting polymers represent an emerging class of conductors combining notable optoelectronic and thermoelectric properties; however, the electrical performance remains a limiting factor. This review provides an overview of the relevant parameters driving the rarely observed metal-insulator transition. Recent magnetotransport measurements provide clearer insight to study the proximity to the metallic state, i.e. the exact quantification of scattering and mobility. From that, one conclusion is the desired isotropic metallic phases depend on coherence and intermolecular radii.

Charge-transfer complex crystals have been extensively studied because of their metallic conductivity, photoconductivity, ambipolar charge transport, and high career mobility. Numerous studies of their applications for organic electric devices such as organic field effect transistors and solar cells have reported. However, bulky single crystals of charge-transfer complexes are difficult to handle, specifically to be made into a form of a thin film. Recently, nano/micro crystallization of charge-transfer crystal is attracted to realize thin film applications. In this paper, charge transfer complex nanorods composed of dibenzotetrathiafulvalene-tetracyanoquinodimethane (DBTTF-TCNQ) were prepared by the reprecipitation method. The as-formed nanorods possess a kinetically metastable crystal structure different from the thermodynamically stable bulk crystal prepared by slow evaporation of the solvent. From photoconductive measurement, nanorod stacks show a significant photosensitivity (354.57 μA/W) on par with bulk crystal (417.14 μA/W). These results suggest dibenzotetrathiafulvalene-tetracyanoquinodimethane (DBTTF-TCNQ) nanorods have a favorable crystal structure for carrier transport due to the difference of molecular stacking assembly.

Understanding the fate of fecal pollution in the landscape is required for microbial risk analysis. The aim of this study was to assess the patterns and dynamics of beta-D-glucuronidase (GLUC), which has been suggested as a surrogate for fecal pollution monitoring, in a stream draining an agricultural headwater catchment. Automated enzymatic on-site measurements of stream water and sediments were made over two years (2014-2016) to quantify the sources and pathways of GLUC in a stream. The event water fraction of streamflow was estimated by stable isotopes. Samples from field sediments on a hillslope, streambed sediment and stream water were analyzed for GLUC and with a standard E. coli assay. The results showed ten times higher GLUC and E. coli concentrations during the summer than during the winter for all compartments (field and streambed sediments and stream water). The E. coli concentrations in the streambed sediment were approximately 100 times those of the field sediments. Of the total GLUC load in the study period, 39% were transported during hydrological events (increased streamflow due to rainfall or snowmelt); of these, 44% were transported when the stream contained no recent rainwater. The results suggested that a large proportion of the GLUC and E. coli in the stream water stemmed from resuspended streambed sediments. Moreover, the results strongly indicated the existence of remnant populations of GLUC-active organisms in the catchment. usc Refereed/Peer-reviewed

Rivers and other freshwater systems play a crucial role in ecosystems, industry, transportation and agriculture. Despite the > 40 years of inland water observations made possible by optical remo ...

Hybrid thin films of crystalline CuSCN and 4-(N,N-dimethylamino)-4′-(N′-methyl)stilbazolium (DAS) in three distinctively different nanostructures were obtained by electrochemical self-assembly from a single pot containing all the chemical ingredients. Their optical properties for UV–vis-NIR absorption, photoluminescence (PL), and PL excitation spectra were examined between 77 and 298 K, in comparison with solution and solid powder of DAS tosylate (DAST). Unlike all other dyes we tested before, PL of DAS was not quenched but rather enhanced when hybridized with CuSCN. 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 dye in the hybrid thin film, however, shows a slight red shift and only a moderate enhancement at reduced temperatures due to strong exciton stabilization in dielectric environment of CuSCN and concerted PL by energy transfer from CuSCN to DAS luminophore, making it a unique nearly temperature-independent luminescent material.

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 of the precursors DAST/[Cu(SCN)]+ = ca. 1/31, molar ratio of the product DAS/CuSCN = ca. 1/48, below which the loading becomes diffusion limited for DAS to be occluded in the CuSCN grains, whereas surface reaction for formation of complex between CuSCN 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.

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 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.

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.

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.

Summary Electrochemical reduction of carbon dioxide (CO 2 RR) 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 CO 2 to formate. We explored, using density functional theory, how the incorporation of sulfur into tin may favor formate generation. We used atomic layer deposition of SnS x followed 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 CO 2 RR at geometric current densities of 55 mA cm −2 at −0.75 V versus reversible hydrogen electrode with a Faradaic efficiency of 93%. Furthermore, Sn(S) catalysts show excellent stability without deactivation (

Carbon 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 CO2 concentrations (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 CO2 concentrations, 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 CO2 conditions and overall weak supersaturation of CO2 in the main channel (average 133.8% saturation) and tributaries. We observed only weak correlations between CO2 saturation, chlorophyll a fluorescence, and turbidity, thus not strongly supporting our hypothesis of primary prod...

Nanostructured inorganic–organic hybrid thin films of copper(I) thiocyanate (CuSCN) and 4-(N,N-dimethylamino)-4′-(N′-methyl)stilbazolium tosylate (DAST) were electrochemically self-assembled by adding DAST into methanolic bath containing Cu2+ and SCN− ions. Loading of the stilbazolium organic chromophore (DAS+) increased linearly on increasing DAST concentration, accompanied with changes of the film morphology, crystallographic orientation of CuSCN and transition from β- to α-CuSCN. At low DAST concentrations, transport limited passive occlusion of DAS+ has been suggested with its diffusion coefficient of 1.25 × 10−6 cm2 s−1 in methanol at 298 K, while the loading receives kinetic limitation by the surface chemical reaction to yield definitive hybrid structures, resulting in unique “hair comb” shape β-CuSCN-DAST and “nano-platelets” shape α-CuSCN-DAST hybrid structures. Both the inorganic and organic components are interconnected and bi-continuous, as the loaded DAS+ could be totally extracted by dimethylacetamide to leave porous skeleton of crystalline CuSCN, making them highly interesting for device applications.

Permafrost in high alpine catchments is expected to disappear in future warmer climates, but the hydrological impact of such changes is poorly understood. This paper investigates the flow paths and the hydrological response in a 5 km2 high alpine catchment in the Otztal Alps, Austria, and their changes resulting from a loss of permafrost. Spatial permafrost distribution, depth to the permafrost table and depth to the bedrock were mapped by geophysical methods. Catchment runoff and meteorological variables were monitored from June 2008 to December 2011. These data were used along with field experience to infer conceptual schemes of the dominant flow paths in four types of hillslopes that differ in terms of their unconsolidated sediment characteristics and the presence of permafrost. The four types are: talus fans, rock glaciers, Little Ice Age (LIA) till and Pre-LIA till. Permafrost tends to occur in the first three types, but is absent from Pre-LIA till. Based on these flow path concepts, runoff was simulated for present conditions and for future conditions when permafrost has completely disappeared. The simulations indicate that complete disappearance of permafrost will reduce flood peaks by up to 17% and increase runoff during recession by up to 19%. It is argued that change modeling needs to account for flow path types and their changes based on geophysical surveys and field investigations. This article is protected by copyright. All rights reserved.

We have developed a simple and robust process to prepare efficient perovskite solar cells. Pinhole free thin films of CH3NH3PbI3−xClx can be coated on high conductivity poly(3,4-ethylenedioxythiophene) poly(styrene-sulfonate) (PEDOT:PSS), (Clevios PH1000) when the PEDOT:PSS is deposited together with dimethyl sulfoxide (DMSO) and Zonyl as additives. This process enables the fabrication of perovskite solar cells using [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as electron transport layer with >12% power conversion efficiency, low hysteresis and excellent operational stability. We have performed a detailed opto-electronic characterization of these solar cells and identified the main loss mechanism limiting the device performance.

The current study reports the application of chalcopyrite semiconductor CuInS2 (CIS) nanofibers for the reduction of CO2 to CO with a remarkable Faradaic efficiency of 77 ± 4%. Initially the synthesis of CuInS2 nanofibers 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 CuInS2 nanofibers 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 CuInS2 in nanofibrous structure as compared to the solution processed CuInS2. This underlines the important effect of the electrode ...

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 nanopar...

We have established electrochemical self-assembly (ESA) of inorganic / organic hybrid thin films in which the inorganic is CuSCN, known as a wide bandgap p-type semiconductor, whereas the organic is 4-N,N-dimethylamino-4’-N’-methylstilbazolium chromophore (abbreviated as DAS+) as its salt with tosylate (DAST) known to exhibit second-order nonlinear optical property for terahertz emitters. The CuSCN/DAS hybrid thin films by ESA show concerted photoluminescence based on energy transfer from inorganic CuSCN to organic DAS, making us anticipate its potential use in optoelectronic devices [1]. Understanding the mechanism of ESA to obtain tuning knob to maximize its functionality is therefore important. In our previous study, switching of dye loading mechanism has been suggested, depending on DAS concentration (C DAS) in the bath [2]. With low C DAS, the loading is limited by diffusion so that DAS is entrapped within CuSCN crystal grains, while surface reaction of hybridization begins to limit the dye loading with high C DAS, resulting in formation of unique nanostructures as well as phase separation of inorganic and organic domains. The border for the switching of dye loading mechanism was found as the ratio between bulk concentrations of dye and the [Cu(SCN)]+ complex, C DAS/C comp = ca. 1/31 in case of DAS+ [3]. In this study, electrochemical analysis has been performed employing rotating disk electrode (RDE) under variation of bulk concentration of dye (DAST and CNST = 4-cyano-4’-(N’-methyl)stilbazolium tosylate for comparison) to verify the proposed mechanism. CNS+ has a strongly electron withdrawing -CN group and therefore bears a much larger dipole moment of 23.5016 Debye than that of DAS+ (10.1442 Debye) as determined by DFT calculation. Thus, a much stronger interaction of CNS+ with CuSCN (essentially with SCN- ion) is expected than DAS+. The overall behavior of CNS+ has been found exactly the same as DAS+ such as changing the crystal orientation of β-CuSCN to lay down its c-axis and phase transition from β- to α-CuSCN. However, such transitions were found for smaller concentrations of CNS+ than DAS+ because of its stronger affinity with CuSCN. The switching dye loading mechanism and associated change of the hybrid structure has also been observed for CNS. Fig. 1 shows plots of amount of dye loaded into the hybrid thin films against the dye concentrations in the electrolytic bath for DAS+ and CNS+. The steep slopes in low dye concentration range represent diffusion limited loading, whereas the moderate slopes are those limited by surface reaction. The bending points, C DAS = 60 μmol dm-3 and C CNS = 200 μmol dm-3, indicate the switching borders for C comp = 2.5 mM. Because of the increased stability of adsorption of CNS+ on CuSCN surface, diffusion limited loading, thus all dyes reaching the electrode surface buried inside the film, continues to operate up to this high dye concentration. The increased stability of CuSCN/CNS surface complex also resulted in about 3 times more efficient dye uptake in the surface reaction limited regime. These results nicely confirm the validity of the proposed mechanism both for DAS+ and CNS+, and that the switching border can be varied by the stability of CuSCN/dye complex. Full analysis should be able to determine C CNS/C comp ratio as the switching border. [1] K. Uda et al. ACS Omega, 4, 4056-4062 (2019). [2] Y. Tsuda et al., Monatshefte für Chemie, 148, 845-854 (2017). [3] Y. Tsuda et al., J. Electrochem. Soc. 166(9) B3096-B3102 (2019). Figure 1

Electrocatalytic hydrogen evolution reaction (HER) is promising to achieve conversion of renewable electricity into storable chemical energy. For practical installation of such technology, it is important to develop active and stable electrocatalysts without relying on rare metal elements. Recently, some metal-free conductive organic polymers such as poly-dopamine (PDA) and poly-guanine (PG) have been found to exhibit stably high catalytic activity towards HER1-3. Also, we have achieved polymerization of neutral red (NR) dye, which is chemically analogous to aniline and bears amino groups at a high density. Oxidative chemical vapor deposition (oCVD) or electrodepolymerization deposition (EPD) were the techniques to achieve formation of PNR. PNR exhibited a good catalytic activity for CO2 reduction reaction (CO2RR), although the one prepared by oCVD was about twice as active as that by EPD. Structural disordering of the oCVD sample was supposed to contribute to the catalysis. It is likely that there is an optimum for the balance between conductivity and the density of hydrogen bonding sites. In this study, we have studied electrochemical co-polymerization of NR and aniline to find the optimum design of the catalyst. Electro-polymerization of poly-aniline (PANI), PNR or co-polymer PANI-PNR was carried out at an F-doped tin oxide (FTO) coated conductive glass (Asahi-DU) or a carbon felt (CF, Jing Long Te Tan) substrate by potential cycling between -0.2 and +1.0V vs. Ag/AgCl in aqueous solutions containing ANI, NR or their mixtures at appropriate ratios at a total monomer concentration of 50 mM and 0.1 M H2SO4 for 50 (FTO) or 20 cycles (CF) under N2. Linear sweep voltammetry (LSV) was performed on polymer coated CF electrodes in a 0.5 M H2SO4 under N2 for evaluation of HER catalysis. PANI appeared dark green, PNR red, whereas PANI-PNR was black. These color differences already speak for successful loading of NR into PANI to achieve PANI-PNR copolymer. Cyclic voltammograms (CVs) during EPD of PANI and PNR show the characteristic redox peaks3 (Fig. 1 a, b). While redox peaks of PANI continue to grow, the reversible redox peaks of NR almost stay the same, since formation of cation radical of NR under the present acidic condition is inefficient.3 When ANI and NR are blended, however, CV that differ from those for homopolymers of PANI and PNR is obtained (Fig. 1c). Although this CV is not the exact superimpose of the two for PANI and PNR, it suggests the presence of NR in the film and its contribution to the redox behavior. HER current in LSV almost remains the same when CF is coated with PANI, indicating its disability of electrocatalysis (Fig. 1d). Although PANI should be the most conductive among the polymers we tested here, PANI does not possess hydrogen bonding amino groups. PNR only showed moderate catalysis partly due to the small film thickness we could achieve under the current preparation condition. The PANI-PNR copolymer indeed exhibited very high catalytic activity to reduce the overvoltage as small as 250 mV. It is likely that NR provides hydrogen bonding catalytic centers while PANI assures a high conductivity. Thus, a superior catalysis has been achieved by the co-polymer strategy than using the homopolymers. The optimal compositional balance between PANI and PNR should be found by further experimental elaboration. References: Coskun et al., Mater., 2020, 1902177. Coskun et al., Mater. interfaces, 2019, 1901364. Xin Huang et al., 237th ECS meeting abstract, 2019, 135704. Figure 1

１． Intention Concentration of carbon dioxide (CO2) in the atmosphere has steadily increased since industrial revolution. Despite the recent significant cost reduction of renewable electricity by solar and wind, their intermittency hinders the total shift to renewable energy. It is urgently needed to develop technologies for fast conversion of electrical energy into storable chemical energy by electrolysis, e.g., by water splitting and CO2 reduction. Stable and high-performance electrocatalysts are essential but must be developed without depending on precious metals for the real use and sustainability of the technology. Recently, we have demonstrated high and stable electrocatalytic properties of conductive organic polymers, such as polydopamine (PDA) and polyguanine (PGA) for hydrogen evolution reaction (HER) and CO2 reduction reaction (CO2RR)1,2). Hydrogen bonding N and O atoms introduced to these polymers are expected to stabilize the reaction intermediates for their high catalytic activities. In this study, a phenazine dye, neutral red (NR) was employed as the monomer to obtain a metal-free catalyst. NR bears many amino functions to make it electropolymerizable just like poly-aniline (electropolymerization deposition, to be called EPD). Also, oxidative chemical vapor deposition (oCVD) was employed to obtain PNR. Synthesis, characterization and comparison of the catalytic activities of PNR by EPD and oCVD are discussed. ２． Experiment EPD of PNR onto carbon felt (CF) was carried out by cycling potential between -1 and +1 V vs. Ag/AgCl for 100 cycles in an aqueous solution containing 0.2 mmol/L NR and 0.5 mol/L KNO3 (pH 5) at 50 mV/s. oCVD of PNR was performed in a three-zone quartz tube furnace under N2 flow, while setting the temperature for NR, sulfuric acid and CF at 375, 220 and 100ºC, respectively, for 240 min. PNR-modified as well as bare CF electrodes were measured under N2 and CO2 in a 1 M KNO3 (pH 7) for their catalytic activities for HER and CO2RR. ３． Result While bare carbon felt (CF) electrode does not show any catalytic activity towards CO2RR, showing about -3 mA cm-2 current at –1 V vs. Ag/AgCl, supposedly dominated by that for HER, the PNR coated CFs show enhanced current (Fig. 1a). That by EPD gives about -5 and -6 mA under N2 and CO2, respectively, indicating its moderate catalytic activity for HER and CO2RR. PNR prepared by oCVD, on the other hand, gives -6 and -12 mA, to demonstrate its superior activity, especially for CO2RR. Chronoamperogram measured during long term electrolysis for 17 h at the oCVD PNR electrode indicates reasonable stability of the catalysis (Fig 1b). These results already nicely confirm catalytic activity of PNR for its conductivity and hydrogen-bonding ability. H. Coskun et al., Sci. Adv. 3, e1700686 (2017). H. Coskun et al., Adv. Mater. Interf. 10, 1901364 (2019). Figure 1

1. Introduction Hydrogen is a promising energy carrier, but is currently produced by steam reforming of fossil fuels to discharge CO2. Water splitting by electricity from renewable resources is an ideal solution. However, expensive and rare metals such as Pt and Ru are needed as electrocatalysts for their high activity and durability. We have recently found that metal-free organic conductive polymer made by polymerization of guanine (PG) exhibits a high catalytic activity for hydrogen evolution reaction (HER) close to that of Pt.1,2,3 Hydrogen bonding sites in PG are supposed to stabilize the reaction intermediates. It is also interesting that a nucleic acid as one of the key components of DNA has such properties for HER catalysis. In this work, we have explored other nucleic acids, namely, adenine, cytosine and thymine for their capabilities of polymerization by oxidative chemical vapor deposition (oCVD) and HER activities. 2. Experimental oCVD was carried out in a 3-zone heating quartz tubular furnace, in which 0.5 g of monomer (set to 300~360°C depending on melting points), oxidant (mixture of 0.5 mL sulfuric acid and 0.5 g sodium sulfate, 360°C) and carbon felt (CF) substrate (1.5 cm × 2.5 cm, Jing Long Te Tan, 360°C) were put under N2 stream (3 L/min). The deposition was maintained for 30 minutes after the set temperatures were reached and then allowed to cool down. FT-IR spectra were measured to check formation of conductive polymers. Linear sweep voltammetry (LSV) was performed at 10 mV/s on the polymer coated CF electrodes in a 0.1 M sulfuric acid under N2 to evaluate overvoltage for hydrogen evolution reaction (HER) at 10 mA/cm2. 3. Results and Discussion A black layer was formed by oCVD of adenine. Its FT-IR spectrum exhibited broad peaks around 3000 cm-1, indicative of hydrogen bonds, as well as several strong peaks below 1000 cm-1, which shows presence of free charge carriers to evoke infrared-activated vibration (IRAV). Since similar features were observed in the FT-IR of PG,2 formation of conductive poly-adenine (PA) is reasonably expected. While oCVD of cytosine also yielded similar black film, suggesting formation of PC, that of thymine did not afford any product on the substrate, despite several trials to change temperatures and other deposition conditions. The difference can be reasoned as adenine and cytosine bear cross-linkable amino groups, whereas thymine does not have one. Preliminary electrochemical study revealed an overvoltage of CA. 700mV, far larger than that of PG (290 mV).2 While PG has a hydrogen donating -NH group and a hydrogen accepting ketone group in α-position, PA does have an -NH group but not a ketone. Such difference in the structure of hydrogen bonding site is a possible reason for the large difference of the catalytic activity. Further studies about the HER electrocatalysis are under investigation. References: Coskun et al., Sci. Adv. 2017, 3, e1700686. Coskun et al., Adv. Mater. interfaces, 2019, 1901364. Coskun et al., Adv. Mater. 2020, 1902177.

The most active and efficient catalysts for the electrochemical hydrogen evolution reaction (HER) rely on platinum, a fact that increases the cost of producing hydrogen and thereby limits the widespread adoption of this fuel. Here, a metal-free organic electrocatalyst that mimics the platinum surface by implementing a high work function and incorporating hydrogen-affine hydrogen bonds is introduced. These motifs, inspired from enzymology, are deployed here as selective reaction centres. It is shown that the keto-amine hydrogen-bond motif enhances the rate-determining step in proton reduction to molecular hydrogen. The keto-amine-functionalized polymers reported herein evolve hydrogen at an overpotential of 190 mV. They share certain key properties with platinum: a similar work function and excellent electrochemical stability and chemical robustness. These properties allow the demonstration of one week of continuous HER operation without notable degradation nor delamination from the carrier electrode. Scaled continuous-flow electrolysis is reported and 1 L net molecular hydrogen is produced within less than 9 h using 2.3 mg of polymer electrocatalyst.

We have found electrochemical self-assembly (ESA) of inorganic / organic hybrid thin films in which the inorganic is CuSCN, known as a wide bandgap p-type semiconductor, whereas the organic is 4-N,N-dimethylamino-4’-N’-methylstilbazolium chromophore (abbreviated as DAS) as its salt with tosylate (DAST) known to exhibit second-order nonlinear optical property for terahertz emitters. DAS is also known to yield a layered inorganic-organic hybrid crystal in a (DAS)(Cu5I6) composition [1]. Strong dipole-dipole interaction of the DAS chromophores aligned between the CuI layers results in a spontaneous photocarrier generation and ambipolar transport in a single absorber solar cell. Thus, CuSCN/DAS hybrid thin films can be attractive alternatives for such opto-electrical applications, when ordered arrangement of DAS chromophore is achieved during ESA. In our previous study, switching of dye loading mechanism has been suggested, depending on DAS concentration (C DAS) in the bath [2]. In low C DAS, the loading is limited by diffusion so that DAS is entrapped within CuSCN crystal grains, while surface reaction of hybridization begins to limit the dye loading in high C DAS, resulting in formation of unique nanostructures as well as phase separation of inorganic and organic domains. In this study, electrochemical analysis by employing rotating disk electrode (RDE) has been performed to verify the mechanism of ESA and also to explore the limit of DAS loading. Electrodeposition of CuSCN undergoes as limited by transport of 1 : 1 complex between Cu2+ and SCN- ions, namely [Cu(SCN)]+ species, near 100% Faradic efficiency with marginal influence by the presence of DAS. Thus, the rate of CuSCN precipitation, P CuSCN, is always proportional to the concentration of the complex (C comp), and also to ω 1/2 (ω = angular speed of rotation of RDE) therefore P CuSCN can be expressed Eq. (1) from Levich equation. P CuSCN = J/F = 0.62×C comp×D comp 2/3×ν -1/6×ω 1/2 ··· (1) On the other hand, the rate of DAS precipitation, P DAS, should also be proportional to ω 1/2 under the regime of diffusion limited loading with a given C DAS, and is independent of CuSCN formation rate. P DAS = 0.62×C DAS×D DAS 2/3×ν -1/6×ω 1/2 ··· (2) Plots of P DAS against C comp for variation of C DAS were examined, and indeed such a trend as predicted from the above-mentioned model was found (Fig. 1). In the high C comp range, P DAS is independent of C comp and appears proportional to C DAS, because of the diffusion limited loading mechanism. When C comp goes below certain concentration, P DAS changes proportionally to C comp, while its slope also increase as dependent on C DAS. The relationship between the switching C comp and C DAS yields C DAS / C comp = 1/31 as the border for the switching of the mechanism [3], whereas the dependence of the slope on C DAS in the low C comp range should reveal the stoichiometry of surface complex between CuSCN and DAS. When the rate surface complex formation, P DAS become proportional to the P CuSCN, assuming n of DAS complexes with single CuSCN site yields the equilibrium as the right and the surface is expected to be always equilibrated such equation, P CuSCN + nC DAS ⇄ P DAS ··· (3) Stability constant K should be expressed like Eq. (4), K = P DAS/P CuSCN × C DAS n ··· (4) Eq. (4) can be re-written by inserting Eq. (1), P DAS/C comp= 0.62×D comp 2/3×ν -1/6×ω 1/2 ×K×CDAS n ··· (5) Plotted slope of Fig. 1 in the low C comp range (P DAS/C comp) against C DAS and did fitting with n as variable and then resulted n = 0.6. It means approximately one DAS coordinating two CuSCNs and stability constant K can be calculated as 6.78×102 mol−0.5 cm2.5. [1] Elena Cariati et al., Adv. Mater., 13, 1665-1668 (2001). [2] Yuki Tsuda et al., Monatshefte für Chemie, 148, 845-854 (2017). [3] Yuki Tsuda et al., J. Electrochem. Soc. 166(9) B3096-B3102 (2019). Figure 1

The most active and efficient catalysts for the electrochemical hydrogen evolution reaction rely on noble metals, a fact that increases the cost of producing hydrogen and thereby limits the widespread adoption of this fuel. Here we present metal-free polydopamine and polyguanine as selective organic hydrogen electrocatalysts1–3. The conducting functional polymers incorporate selective hydrogen-affine hydrogen bonds that possess a similar hydrogen binding energies and work function as e.g. platinum. We report the synthesis of hydrogen-selective electrocatalytic polyguanine and polydopamine and demonstrate the enhancement of the rate-determining step in the proton reduction. We further present mechanistic spectral IR-operando studies on the catalytic hydrogen bonded motifs as well as the continuous electrolysis to molecular hydrogen using polyguanine and polydopamine electrodes for several 100 hours without notable degradation. (1) Coskun, H.; Aljabour, A.; Schöfberger, W.; Hinterreiter, A.; Stifter, D.; Sariciftci, N. S.; Stadler, P. Cofunction of Protons as Dopant and Reactant Activate the Electrocatalytic Hydrogen Evolution in Emeraldine‐Polyguanine. Adv. Mater. Interfaces 2019, 1901364 DOI: 10.1002/admi.201901364. (2) Coskun, H.; Aljabour, A.; Uiberlacker, L.; Strobel, M.; Hild, S.; Cobet, C.; Farka, D.; Stadler, P.; Sariciftci, N. S. Chemical Vapor Deposition - Based Synthesis of Conductive Polydopamine Thin-Films. Thin Solid Films 2018, 645 (August 2017), 320–325 DOI: 10.1016/j.tsf.2017.10.063. (3) Coskun, H.; Aljabour, A.; Luna, P. De; Sun, H.; Nishiumi, N.; Yoshida, T.; Koller, G.; Ramsey, M. G.; Greunz, T.; Stifter, D.; Hassel, A. W.; Sariciftci, N. S.; Sargent, E. H.; Stadler, P. Hydrogen-Bonded Polymers Mimic Noble Metal Electrocatalysts. Adv. Mater., submitted.

Whether they are inorganic or organic, the key words for creation of new functional materials should be (1) solution, (2) low temperature, and (3) rare-element-free for sustainable development. As a leading example, we explore electrochemical self-assembly (ESA) of inorganic / organic hybrid thin films. In addition to the interests to study evolution of unique hybrid structures, concerted new functionalities are anticipated due to intimate interaction between the inorganic and organic constituents. Herein, we report ESA of CuSCN / 4-(N,N-dimethylamino)-4’-(N’-methyl)stilbazolium (DAS) hybrid thin films and its concerted photoluminescence (PL) behavior [1]. Hybrid thin films of crystalline CuSCN/DAS in three distinctively different nanostructures were obtained by ESA from a single pot containing all the chemical ingredients. Adsorption of DAS during the electrochemical precipitation of CuSCN result in significant change of film morphology, crystal structure and its orientation, as DAS “occluded” into crystal grains of β-CuSCN, DAS phase separated nano-“haircomb” shape β-CuSCN, and DAS phase-separated in nano-“scale” shape α-CuSCN, by simply increasing DAST concentration in the bath [2]. Their optical properties for UV-vis-NIR absorption, photoluminescence (PL), and PL excitation (PLE) spectra were examined between 77 and 298 K, in comparison with solution and solid powder of DAS tosylate (DAST). While all the fluorescent dyes we previously found to hybridize with CuSCN underwent quenching due to hole injection from dye excited state to the valence band of CuSCN, DAS presented the first and only example to exhibit PL when combined with CuSCN [3]. 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. However, the PL of the same dye in the hybrid thin film shows a slight red shift and not much intensified. Dielectric environment as well as ordered alignment of DAS greatly stabilize exciton against thermalization loss by suppressing twisted intramolecular charge transfer (TICT) and exciton-phonon coupling. The smallest temperature dependence, thus to be interpreted as the strongest exciton stabilization, was found for the “haircomb” β-CuSCN/DAS hybrid. The PLE spectra of the “scale” α-CuSCN/DAS hybrid show a prominent sharp peak at 380 nm and another double-peak between 400 and 450 nm by cooling temperature. The former corresponds to the band-edge absorption of CuSCN, while the latter being similar to the LMCT absorption of [Cu(SCN)]+ complex. It has been confirmed that those peaks in PLE spectra indicate the contribution of CuSCN thin film without DAS for the generation of PL. These contributions of the light absorption by CuSCN to the PL from DAS clearly indicate energy transfer from CuSCN to DAS as a concerted PL mechanism. Concerted PL by energy transfer from CuSCN to DAS has also been found to occur efficiently, especially for the “scale” α-CuSCN/DAS with the largest contact area due to interpenetrating hybrid nanostructure in the smallest domain size. Those hybrid thin film having the concerted PL mechanism (Fig. 1) can possibly make these materials useful as LEDs. [1] K. Uda et al., ACS Omega, 2019, 4 (2), 4056-4062. [2] Y. Tsuda et al., Chem., 2017, 148, 845-854. [3] K. Uda et al., ECS Trans., 2019, 88, 323-333. Figure 1

Concentration of carbon dioxide (CO2) in the atmosphere has steadily increased since industrial revolution. Despite the recent significant cost reduction of renewable electricity by solar and wind, their intermittency hinders the total shift to renewable energy. It is urgently needed to develop technologies for fast conversion of electrical energy into storable chemical energy by electrolysis, e.g., by water splitting and CO2 reduction. Stable and high-performance electrocatalysts are essential but must be developed without depending on precious metals for the real use and sustainability of the technology. Recently, we have demonstrated high and stable electrocatalytic properties of conductive organic polymers, such as polydopamine (PDA) and polyguanine (PGA) for hydrogen evolution reaction (HER) and CO2 reduction reaction (CO2RR)1,2). Hydrogen bonding N and O atoms introduced to these polymers are expected to stabilize the reaction intermediates for their high catalytic activities. In this study, a phenazine dye, neutral red (NR) was employed as the monomer to obtain a metal-free catalyst. NR bears many amino functions to make it electropolymerizable just like poly-aniline (electropolymerization deposition, to be called EPD). Also, oxidative chemical vapor deposition (oCVD) was employed to obtain PNR. Synthesis, characterization and comparison of the catalytic activities of PNR by EPD and oCVD are discussed. EPD of PNR onto carbon felt (CF) was carried out by cycling potential between -1 and +1 V vs. Ag/AgCl for 100 cycles in an aqueous solution containing 0.2 mmol/L NR and 0.5 mol/L KNO3 (pH 5) at 50 mV/s. oCVD of PNR was performed in a three-zone quartz tube furnace under N2 flow, while setting the temperature for NR, sulfuric acid and CF at 375, 220 and 100ºC, respectively, for 240 min. PNR-modified as well as bare CF electrodes were measured under N2 and CO2 in a 1 M KNO3 (pH 7) for their catalytic activities for HER and CO2RR. While bare carbon felt (CF) electrode does not show any catalytic activity towards CO2RR, showing about -3 mA cm-2 current at –1 V vs. Ag/AgCl, supposedly dominated by that for HER, the PNR coated CFs show enhanced current (Fig. 1a). That by EPD gives about -5 and -6 mA under N2 and CO2, respectively, indicating its moderate catalytic activity for HER and CO2RR. PNR prepared by oCVD, on the other hand, gives -6 and -12 mA, to demonstrate its superior activity, especially for CO2RR. Chronoamperogram measured during long term electrolysis for 17 h at the oCVD PNR electrode indicates reasonable stability of the catalysis (Fig 1b). These results already nicely confirm catalytic activity of PNR for its conductivity and hydrogen-bonding ability. References: 1. H. Coskun et al., Sci. Adv., 2017, 3, e1700686. 2. H. Coskun et al., Adv. Mater. Interf., 2019, 10, 1901364. Figure 1

Among various metal oxides previously tested, Co3O4 is known to be one of the best catalysts for oxygen evolution reaction (OER). In this study, doping of Co ions into nanocrystals of zinc oxide (ZnO) has been achieved by microwave (MW) assisted hydrothermal reaction to form catalytic surface sites for OER combined with highly conductive and stable ZnO for flexible catalyst design and potential enhancement of the catalytic activity. MW-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 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.

Electrocatalytic hydrogen evolution reaction (HER) and carbon dioxide reduction reaction (CO2RR) are the key reactions for conversion of renewable electricity into storable chemical energies. It is crucially important to develop active and stable electrocatalysts without relying on rare metal elements for sustainable energy systems. Recently, some metal-free conductive organic polymers such as polydopamine (PDA) and poly guanine (PGA) synthesized by oxidative chemical vapor deposition (oCVD) have been found to exhibit high catalytic activity and durability for HER and CO2RR1,2. In addition to their conductivity of the π-conjugated system of the main chain, these polymers contain heteroatoms such as N and O at high densities, which are believed to act as hydrogen bonding sites for stabilization of reaction intermediates. However, their exact structures and relationship to the catalytic activities are not fully grasped. In this study, we employ electro-polymerization as the mean to obtain catalytic polymers. Taking polyaniline (PANI) as the host, hydrogen bonding monomers such as dopamine (DA), guanine (GA) and neutral red (NR) are to be introduced to obtain co-polymers with controlled structure and density of the hydrogen bonding sites. Comparison of their electrocatalytic activity to those of the respective homo-polymers should reveal the effective catalytic sites and its product selectivity, which should result in optimal design of the catalyst. Electro-polymerization of PANI and PNR was carried out at an ITO glass substrate in an aqueous solution containing 50 mM ANI or NR and 0.1 M H2SO4 during 50 times potential cycling between -0.5 and +0.6 V vs. Ag/AgCl under the N2. Copolymers were obtained by mixing the monomers at appropriate ratios. The films were characterized by FT-IR spectra. PANI, PNR and their copolymer appeared dark green, dark red and black, respectively. While CVs during electropolymerization of PANI continue to increase the redox peaks of PANI as typically expected, those for PNR show decrease of anodic current suggesting inactiveness of PNR for its redox (Figs. 1 a, b). When they are mixed together, a new redox peak in between those from PANI and another irreversible anodic peak close to +0.9 V appear, which indicate loading of NR in redox active form into PANI (Fig. 1c). The FTIR spectrum of the copolymer showed significant difference from the homo-polymers of PANI and PNR with intense absorption peaks between 800 and 1600 cm-1 (Fig. 1d). These peaks arise from infrared-activated vibrations (IRAV) due to the presence of polaron in the main chain, thus are indicative of its conductive nature. These results suggest improvement of conductivity by heterogeneity in copolymers. Its relevance to the catalytic property and optimal density of hydrogen bonding sites are to be further investigated. References: 1. Coskun et al., Adv. 2017, 3, e1700686. 2. Coskun et al., adv mater interfaces, 2019, 1901364. Figure 1

Electrochemical conversion of CO2 to alcohols is one of the most challenging methods of conversion and storage of electrical energy in the form of high-energy fuels. The challenge lies in the catalyst design to enable its real-life implementation. Herein, we demonstrate the synthesis and characterization of a cobalt(III) triphenylphosphine corrole complex, which contains three polyethylene glycol residues attached at the meso-phenyl groups. Electron-donation and therefore reduction of the cobalt from cobalt(III) to cobalt(I) is accompanied by removal of the axial ligand, thus resulting in a square-planar cobalt(I) complex. The cobalt(I) as an electron-rich supernucleophilic d8-configurated metal centre, where two electrons occupy and fill up the antibonding dz2 orbital. This orbital possesses high affinity towards electrophiles, allowing for such electronically configurated metals reactions with carbon dioxide. Herein, we report the potential dependent heterogeneous electroreduction of CO2 to ethanol or methanol of an immobilized cobalt A3-corrole catalyst system. In moderately acidic aqueous medium (pH = 6.0), the cobalt corrole modified carbon paper electrode exhibits a Faradaic Efficiency (FE%) of 48 % towards ethanol production., Electrochemical conversion of carbon dioxide to ethanol is one of the most challenging energy conversion reactions. Here the authors show selective electroreduction of carbon dioxide to ethanol by using a functionalized cobalt A3-corrole catalyst immobilized on a carbon paper electrode.

This study used automated enzymatic activity measurements conducted from a mobile research vessel to detect the spatial variability of beta‑d‑glucuronidase (GLUC) activity in large freshwater bodies. The ship-borne observations provided the first high-resolution spatial data of GLUC activity in large water bodies as rapid indication of fecal pollution and were used to identify associations with hydrological conditions and land use. The utility of this novel approach for water quality screening was evaluated by surveys of the Columbia River, the Mississippi River and the Yahara Lakes, covering up to a 500 km river course and 50 km

Over the past 15 years, pioneering interdisciplinary research has been performed on the microbiology of hydrogeologically well-defined alpine karst springs located in the Northern Calcareous Alps (NCA) of Austria. This article gives an overview on these activities and links them to other relevant research. Results from the NCA springs and comparable sites revealed that spring water harbors abundant natural microbial communities even in aquifers with high water residence times and the absence of immediate surface influence. Apparently, hydrogeology has a strong impact on the concentration and size of the observed microbes, and total cell counts (TCC) were suggested as a useful means for spring type classification. Measurement of microbial activities at the NCA springs revealed extremely low microbial growth rates in the base flow component of the studied spring waters and indicated the importance of biofilm-associated microbial activities in sediments and on rock surfaces. Based on genetic analysis, the autochthonous microbial endokarst community (AMEC) versus transient microbial endokarst community (TMEC) concept was proposed for the NCA springs, and further details within this overview article are given to prompt its future evaluation. In this regard, it is well known that during high-discharge situations, surface-associated microbes and nutrients such as from soil habitats or human settlements-potentially containing fecal-associated pathogens as the most critical water-quality hazard-may be rapidly flushed into vulnerable karst aquifers. In this context, a framework for the comprehensive analysis of microbial pollution has been proposed for the NCA springs to support the sustainable management of drinking water safety in accordance with recent World Health Organization guidelines. Near-real-time online water quality monitoring, microbial source tracking (MST) and MST-guided quantitative microbial-risk assessment (QMRA) are examples of the proposed analytical tools. In this context, this overview article also provides a short introduction to recently emerging methodologies in microbiological diagnostics to support reading for the practitioner. Finally, the article highlights future research and development needs. This article is categorized under: 1Engineering Water > Water, Health, and Sanitation2Science of Water > Water Extremes3Water and Life > Nature of Freshwater Ecosystems.

Inorganic-organic hybrid materials have shown excellent optoelectronic device performances from single-layer solution-processed thin films. Their electronic bands are coupled to the ionic interactions within the organic and inorganic moieties. Exactly these features also allow a sequential deposition route so as to implement thin films having inherently non-linear optical properties perpendicular to the substrate plane. Here, we demonstrate a sequential layer-by-layer path to prepare films of an inorganic-organic hybrid material [DAMS][Cu5I6] through a self-recognition process in the solid state between the first Cul layer and the successive [DAMS]I layer. A persistent non-linear optical behavior, typical of oriented films, is consequently accessible on different substrates without electrical bias poling through the excellent self-recognition of dipoles aligned along the z-axis. In addition, semiconductive and preliminary photovoltaic properties of the film are observed. This work highlights all aspects of the solution-based films with potential to serve as versatile and robust optoelectronic active materials.

Weak localization describes a metallic system, where due to the presence of disorder the electrical transport is governed by inelastic electron relaxation. Therefore the theory defines a threshold of spatial and of energetic disorder, at which a metal-insulator transition takes place. To achieve a metallic state in an inherently disordered system such as a conductive polymer, one has to overcome the threshold of localization. In this work we show that the effective suppression of disorder is possible in solution-processible poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate). We grow polymer films under optimized conditions allowing self-organization in solution. Interestingly, we find the requisite threshold, at which the system becomes finally metallic. We characterize the transition using a complementary morphology and magneto-electrical transport study and find coherent electron interactions, which emerge as soon as local order exceeds the macromolecular dimensions. These insights can be used for discrete improvement in the electrical performance, in particular for tailoring conductive polymers to alternative metal-like conductors.

Sol-gel processed copper indium sulfide (CIS) films have been processed on glass and transparent indium doped tin oxide (ITO)-coated glass electrodes by a straightforward layer by layer spin coating route yielding excellent film qualities with subsequent thermal annealing. Resulting films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-vis spectroscopy. We apply these films in an electrochemical cell as a working electrode and take a view on the reduction of carbon dioxide (CO2) to its energy richer carbon monoxide (CO) in acetonitrile solution containing 0.1 M (C4H9)4NPF6 supporting electrolyte saturated with CO2. CIS films exhibit pronounced electrochemical and photoelectrochemical activities. Concomitantly, we quantify the generation of CO, which starts to evolve at a threshold potential of −0.60 V vs normal hydrogen electrode (NHE). The calculated faradaic efficiency of the electrochemical reduction of CO2 into CO exceeds 20 (±1) % in an optimized thin-film structure.