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Hydrogen generation during wastewater treatment has remained a long-standing challenge for the environment preservation welfare. In the present work, we have fabricated a promising bifunctional thin film-based catalyst for hydrogen generation with concurrent wastewater treatment. The prepared catalyst film is a vertically oriented thin SnS (tin monosulfide) nanosheet array on a Ni-foam (SnS/NF) obtained via a solution process, demonstrating a promising electrocatalytic activity towards the generation of green H2 fuel at the cathodic side and the decomposition of urea waste at the anodic side. Notably, while assembling two identical electrodes as cathode and anode together with a reference electrode (i.e., SnS/NF∥SnS/NF vs. RHE assembly) in 1 M KOH aqueous electrolyte containing 0.33 M urea, the electrolyzer electrolyzed urea at a lower cell potential of 1.37 and 1.43 V (vs. RHE) to deliver a current density of 10 mA cm−2 and 50 mA cm−2, respectively, for the decomposition of urea at the anodic SnS/NF electrode and green hydrogen fuel generation at the cathodic SnS/NF electrode. This activity on electrocatalytic urea decomposition lies within the best performance to those of the previously reported sulfide-based and other catalytic materials. The promising catalytic activities of the SnS catalyst film are attributed to its combined effect of self-standing nanosheet array morphology and high crystallinity, which provides abundant active sites and a facile charge transfer path between the nanosheet arrays and the electrolyte. Thus, the present work offers a green avenue to the waste-urea treatment in water and sustainable hydrogen energy production.

NiS is a highly promising transition metal sulfide versatile for a sensor material owing to its superior conductivity and stability, and herein we report its first incorporation into an electrochemical sensor. Because exposure to electrolyte under electrochemical impact can easily deform NiS, thereby decreasing its electro-activity and measurement reproducibility, a strategy for optimally integrating NiS into sensors is critically necessary. For this purpose, NiS was initially firmly affixed to a mechanical pencil lead (MPL) by means of hydrothermal deposition (with the result designated as MPL-NiS). MPL, a commercially available carbon-based material with consistent quality, was adopted to make the sensor cost-effective and easily prepared. Then, to prevent direct exposure of NiS to samples during electrochemical measurement and to make the sensor surface more reactive for wide variety of analytes, reduced graphene oxide (rGO) was electrodeposited on the NiS surface to construct a final structure of MPL-NiS/rGO. In summary, NiS, a p-type semiconductor with positive charge, was effectively composited and sandwiched with negatively charged rGO and MPL by means of mutual electrostatic interaction. When the developed MPL-NiS/rGO sensor was used to separately measure bisphenol A (BPA) and mercury- Hg2+, the sensitivity and sensor-to-sensor reproducibility were comparable with or superior to those of previously reported sensors.

The present work reports on the morphological influence of catalyst on oxygen reduction reaction (ORR). As a catalyst, Prussian blue analog structured nickel hexacyanoferrate (Ni-HCF) with two distinct morphologically controlled frameworks, viz. granular crystalline bulk film and rose-petal like structured thin film having smooth surface, are synthesized via controlled anodization route, and their morphological influence on the ORR is investigated. In addition, the influence of addition of carbon black, which is commonly used as catalytic dispersing support, is also studied on the catalytic mechanism for the ORR. Based on the hydrodynamic voltammetry of the electrocatalytic films on rotating disk electrode, the number of electrons involved in the reduction of an O2 molecule, and the kinetic current density of the reaction are estimated. While the pristine Ni-HCF frameworks based catalyst, regardless of their morphology, demonstrates the direct reduction of O2 with participation of 4 electrons, the frameworks when mixed with carbon black as support diverts the reduction via two steps with participation of 2 electrons at each step. A larger kinetic current density is, however, obtained in the case of granular crystalline bulk film of the Ni-HCF frameworks.

The present work demonstrates the formation of self-aligned nanoporous architecture of gallium oxide by anodization of gallium metal film controlled at −15 °C in aqueous electrolyte consisting of phosphoric acid. SEM examination of the anodized film reveals that by adding ethylene glycol to the electrolyte and optimizing the ratio of phosphoric acid and water, chemical etching at the oxide/electrolyte interfaces can be controlled, leading to the formation of aligned nanotubular oxide structures with closed bottom. XPS analysis confirms the chemical composition of the oxide film as Ga2O3. Further, XRD and SAED examination reveals that the as-synthesized nanotubular structure is amorphous, and can be crystallized to β-Ga2O3 phase by annealing the film at 600 °C. The nanotubular structured film, when used as photoanode for photoelectrochemical splitting of water, achieved a higher photocurrent of about two folds than that of the nanoporous film, demonstrating the rewarding effect of the nanotubular structure...

This work reports on back-electron injection barrier property and electrical charge storing behavior of PEDOT film with and without substituted propylene as terminal group. As a barrier layer, thin polymer film is deposited on TiO 2 particles of DSSC using photo-induced polymerization route. The same piece of DSSC device is used before and after deposition of polymer thin-film for studying the influence of interfacial treatment. The propylene substituted PEDOT treatment of the device demonstrates an enhanced power conversion efficiency from 4.31 to 5.96% whereas the unsubstituted PEDOT treated device shows only the power conversion enhancement from 4.54 to 5.31%. This finding suggests the higher barrier performance of the propylene substituted PEDOT for back-electron injections. Unlike the barrier performance, the propylene substituted PEDOT shows poorer electrical charge storing behavior with specific capacitance of 63.47 F g −1 whereas the unsubstituted PEDOT film achieved 96.84 F g −1 .

This work reports the influence of thermal treatment on electrocatalytic water oxidation/reduction behaviors of one dimensional CoTe nanotube film deposited on FTO substrate from aqueous solution at room temperature. The optimally annealed film at 200 °C demonstrates substantially better electrocatalytic properties, which can be ascribed to the enhanced electrochemical active surface area and electrical conductivity obtained by improving the intergranular connectivity. In addition, the annealed nanotube film demonstrates highly competitive performance to that of many outstanding electrocatalysts for overall splitting of alkaline water to generate hydrogen as green fuel with the oxygen evolution reaction overpotential of 0.37 V (without iR-compensation) for the benchmark current density of 10 mA cm−2.

Functionalization of BODIPY dyes with TPP substituents endowed them with mitochondria-targeting capabilities. The uniodinated BODIPY control displayed good biocompatibility, low cytotoxicity in the dark, and exceptional cellular imaging capabilities; however, it did not exhibit photodynamic therapeutic properties upon excitation at 530 nm. Dual functional photosensitizers were obtained in the case of mono- and di-iodinated BODIPY derivatives, which exhibited mitochondria-targeting capabilities and provided clear fluorescence confocal bioimages, while efficiently generating high levels of singlet oxygen species and displaying photodynamic therapeutic activity toward two cancer cell lines following LED irradiation. Overall, the results presented herein demonstrate the considerable potential for the use of TPP-functionalized BODIPY dyes as viable agents for fluorescence-imaging-guided photodynamic therapy (PDT) for cancer treatment.

We report the modulation of the dual photo/thermo-responsive multicolor fluorescence from poly( N -isopropyl acrylate) pNIPAM-based nanogels. The thermo-responsive pNIPAM-crosslinked matrix was covalently copolymerized with nitrobenzoxadiazole (NBD) monomers as a Forster resonance energy transfer (FRET) donor and electrostatically conjugated with photochromic spiropyran (SP) dyes as a FRET acceptor. The pristine nanogel emits green fluorescence derived from the NBD moieties; however, the irradiation of the nanogels with UV light led to the transformation of the ring-closed colorless SP moieties to the ring-opened coral-red merocyanine (MC) moieties, resulting in light-pink fluorescent nanogels. Notably, at higher temperatures, the fluorescence of the nanogels was red-shifted and enhanced by the more efficient FRET process. The nanogels were well-distributed in the cellular cytoplasm and showed excellent photochromic function in the subcellular environment for applications as photo-switchable bio-imaging agents and nanothermometers.

One of the challenges in obtaining hydrogen economically by electrochemical water splitting is to identify and substitute cost-effective earth-abundant materials for the traditionally used precious-metal-based water-splitting electrocatalysts. Herein, we report the electrochemical formation of a thin film of nickel-based Prussian blue analogue hexacyanoferrate (Ni-HCF) through the anodization of a nickel substrate in ferricyanide electrolyte. As compared to the traditionally used Nafion-binder-based bulk film, the anodically obtained binder-free Ni-HCF film demonstrates superior performance in the electrochemical hydrogen evolution reaction (HER), which is highly competitive with that shown by a Pt-plate electrode. The HER onset and the benchmark cathodic current density of 10 mA cm–2 were achieved at small overpotentials of 15 mV and 0.2 V (not iR-corrected), respectively, in 1 M KOH electrolyte, together with the long-term electrochemical durability of the film. Further, a metal-HCF-electrode-based full...

We investigated the intramolecular charge transfer characteristics in the S1 state of boron-dipyrromethene (BODIPY) derivatives with triphenylamine (TPA) substituents, depending on the substituted position and the number of substituents. Based on the spectroscopic and theoretical results, the β-substitution of TPA on BODIPY hybridizes locally excited and intramolecular charge transfer characteristics in the S1 state because of strong coupling between the highest occupied molecular orbitals of BODIPY and TPA moieties, and consequently, the BODIPY derivatives with β-substituted TPAs exhibit strong red-color fluorescence around 640 nm in nonpolar and moderately polar solvents. The TPA substituent with propeller-like nonplanar geometry could prevent H-type aggregation between neighboring BODIPY derivative units and induce aggregation-induced emission enhancement (AIEE) characteristics of the BODIPY derivatives with TPA substituents, which are helpful to maintain their emission efficiencies under highly concentrated and condensed conditions. Since the red-color emission and AIEE property of the BODIPY derivatives with β-substituted TPAs are promising characteristics for a bioimaging application, we applied these derivatives to L-929 fibroblast cells for cellular imaging. The BODIPY derivative with a single β-substituted TPA (compound 2) was effectively loaded into porous silica nanoparticles (SNPs). Consequently, we achieved good cellular uptake of 2-SNPs and good cellular imaging, which further confirmed the bioimaging ability of 2-SNPs.

Lithium-sulfur (Li–S) batteries are considered promising candidates for next-generation energy storage devices due to their ultrahigh theoretical gravimetric energy density, cost-effectiveness, and environmental friendliness. However, the application of Li–S batteries remains challenging; mainly due to a lack of understanding of the complex chemical reactions and associated equilibria that occur in a working Li–S system. A new approach preparing graphene-based active cathode materials of Li-S battery with spatially confined lithium sulfides is reported. The starting graphene-embedded 2D-MoS2 was synthesized by a solvothermal method in organic solvents followed by the calcination of trapped organic solvent molecules at 800 °C to give graphene single sheets inside the 2D-MoS2 layers with 7 A distance (MoS2-Gr-32.51). Then, it was electrochemically reduced/lithiated at potential 0.01 V vs Li+/Li generating metallic molybdenum and lithium sulfides. As a result, the structure of MoS2 multi-layers collapsed. The graphene multi-layer (ML-Graphene) was left behind and shut the lithium sulfides between the layers. The sizes of Li2Sn (n = 4–6) are bigger than the inter-layer distance of ML-Graphene, and the escape of sulfur/sulfides from the cathode into the electrolyte is physically blocked alleviating shuttle effects. The specific capacity of ML-Graphene/lithium sulfides cathode was high of 1209 mAh/gMoS2-Gr at 0.1 C (1 C = 670 mA/g). The ML-Graphene exhibited the remarkable lithium intercalation capability, and the theoretical calculation has been carried out to give 2231.4 mAh/g. Such high capacity was hybridized with the theoretical capacity of sulfur (1675 mAh/g), and the ML-Graphene composite with dichalcogenides (2D-MoS2) became a promising platform for the cathode of Li-S batteries.

This work reports on in-situ doping of Fe(III) redox centers to Ni Co based Prussian blue analogue framework films and their eletrocatalytic performance towards water splitting into molecular hydrogen and oxygen. Uniform and self-supported films of frameworks are deposited onto nickel substrate via anodization in 80 vol % glycerol based aqueous electrolyte containing 0.1 M K3[Co(CN)6] with/without addition of a small amount of [Fe(CN)6]3− as doping precursor. XRD, HR-TEM, STEM and XPS characterization of the film confirmed the doping. Notably, the doped film demonstrated an enhanced electrocatalytic activity towards hydrogen and oxygen evolution reaction in alkaline electrolyte with small overpotentials of 169 and 263 mV, respectively to derive the benchmark current density of 10 mAcm−2. In addition, bulk electrolysis at 10 mAcm−2 demonstrated an improved and well-maintained long-term electrochemical durability of the doped film-based cathode and anode for overall splitting of water.

This work presents an epitaxial deposition of a thin film of single crystal MoTe2 nanorods via electrodeposition at room temperature from aqueous based electrolyte purged with argon. The method allows control over film morphology through deposition potential. In a typical deposition performed at −0.8 V vs Ag/AgCl for 10 min, film comprised of 1D MoTe2 nanorods is obtained, while the deposition at −0.9 V vs Ag/AgCl renders nanoplate like structure. When characterized with FE-SEM, XRD, TEM, SAED and Raman spectroscopy, the film shows uniform deposition of single crystal MoTe2 nanorods particularly with metallic 1 T’ phase. In a preliminary test on feasibility of the nanorod film as anode material for Li-ion storage, a promising result is perceived showing discharge capacity of about 770 mAhg−1 with good electrochemical reversibility.

We investigate aggregation-induced emission (AIE) characters of bulk tetraphenylethene (TPE) derivatives with nonpolar and polar exterior chains. The bulk TPE derivatives with nonpolar dodecyl and polar di(ethylene oxide) chains are in liquid crystal (LC) and crystalline phases, respectively, at room temperature. The mobile LC character of the TPE derivatives in bulk is crucial for high AIE efficiency because the mobile LC character is effective in minimizing the number of undesirable nonemissive local sites in aggregates and inducing a homogeneous zigzag-stacked columnar structure with j-type coupled transition dipoles of the TPE derivatives. The mobile LC characteristics of AIE luminogens can be advantageous for highly efficient solid-state emission.

We investigated the mechanism and sensing efficiency of an anthracene-based fluorescent water-content chemosensor (AMG) containing a guanidine moiety in water-miscible organic solvents. Based on spectroscopic and theoretical results, we established that there are two functions of water for AMG in organic solvents, one of which is as a reagent for protonation and the other is in the solvation and stabilization of ionic products, such as protonated AMG (AMGH+) and hydroxide ion. Moreover, the effective solvation and stabilization of ionic products in organic solvents are critical for the mitigation of the deprotonation between them and the relatively high ratio of the fluorescence turn-on AMGH+ species. In 1,4-dioxane with low polarity, AMGH+ and hydroxide ion cannot be effectively solvated, and there is a strong positive correlation between the fluorescence intensity and volumetric fraction of water due to the improved solvation condition caused by the co-existent water. Conversely, the amount of water in polar solvents is less significant, as evidenced by the relatively small increase in the fluorescence intensity upon increasing the water content. This is because ionic products can be stabilized by polar organic solvent molecules without cooperation with water. Conclusively, the solvation and stabilization of ionic products produced by a chemical reaction at a chemical sensing site in a fluorescent chemosensor are important for determining the relative ratio between the fluorescence turn-on and –off species and the overall sensing efficiency of the fluorescent chemosensors.

The present work demonstrates the formation of self-aligned nanoporous architecture of gallium oxide by anodization of gallium metal film controlled at -15 °C in aqueous electrolyte consisting of phosphoric acid. SEM examination of the anodized film reveals that by adding ethylene glycol to the electrolyte and optimizing the ratio of phosphoric acid and water, chemical etching at the oxide/electrolyte interfaces can be controlled, leading to the formation of aligned nanotubular oxide structures with closed bottom. XPS analysis confirms the chemical composition of the oxide film as Ga

A theoretical study on antioxidant properties of fourteen xanthones extracted from the pericarp of G. Mangostana has been performed. Three main reaction mechanisms are investigated: hydrogen atom transfer (HAT), single electron transfer–proton transfer (SETPT) and sequential proton loss electron transfer (SPLET). The O H bond dissociation enthalpy (BDE), ionization energy (IE), proton affinity (PA) and electron transfer energy (ETE) parameters were computed in gas phase and water. The results show that HAT would be the most favorable mechanism for explaining antioxidant activity of xanthones in gas phase, whereas the SPLET mechanism is thermodynamically favored in water.

This work reports on designing of first successful MOF-sensitizer based solid-state photovoltaic device, perticularly with a meaningful output power conversion efficiency. In this study, an intrinsically conductive cobalt-based MOFs (Co-DAPV) formed by the coordination between Co (II) ions and a redox active di(3-diaminopropyl)-viologen (i.e., DAPV) ligand is investigated as sensitizer. Hall-effect measurement shows p-type conductivity of the Co-DAPV film with hole mobility of 0.017 cm2 V–1 s–1, suggesting its potential application as hole transporting sensitizer. Further, the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of Co-DAPV are well-matched to be suitably employed for sensitizing TiO2. Thus, by layer-by-layer deposition of hole conducting MOF-sensitizer onto mesoporous TiO2 film, a power conversion efficiency of as high as 2.1% is achieved, which exceeds the highest efficiency values of MOF-sensitized liquid-junction solar cells ...

This work reports a facile solution based chemical transformation of thin film of CdCO3 cuboids into Cd-based Prussian blue analogue structured thin film with controlled redox-state by manipulating the anion exchange reaction between the solid film and the aqueous solution of K3[Fe(CN)6] at 60 °C. The progress of the transformation reaction is monitored via electron microscopy, X-ray difractometry and X-ray photoelectron spectroscopy. Based on the scenario of the reaction progress revealed by these analysis, the CdCO3 cuboids are first found to be transformed into the smaller cuboids of cadmium ferricyanide, which, on further reaction, are transformed into the cadmium ferrocyanide cuboids. Thus, by controlling the redox-state of the Fe-metal center on the frameworks, the electrocatalytic activity of the frameworks on oxygen reduction reaction (ORR) is studied. The electrocatalytically inert CdCO3 cuboids after transformation to the frameworks with Fe3+-centers demonstrate an enhanced catalytic activity on ORR, while the Fe2+-centers of the frameworks are found to relegate the catalytic activity, thereby manifesting the redox-sate modulated ORR activity of the frameworks. To the best of the authors' knowledge, this is the first report of this kind on redox-state specific ORR activity.

In the present study, a solution-processed organic semiconductor based on indolocarbazole derivative (heptazole) is introduced as a p-type donor material for a bulk-heterojunction photovoltaic device. The heptazole has an optical band gap of 2.97 eV, and its highest occupied molecular orbital-lowest unoccupied molecular orbital energy levels are compactable with the PC60BM to construct a donor-acceptor heterojuction for energy harvesting and transfer. When the bulk-heterojunction photovoltaic devices consisting of ITO/PEDOT:PSS/heptazole:PC60BM/Al with different blending ratio of heptazole:PC60BM were constructed, the cell with 1:1 blending ratio exhibited the best power conversion efficiency. Further, when an indoline organic dye (D149) was introduced as an interfacial modifier to the above donor/acceptor bulk heterojunction, the device demonstrated an enhanced overall power conversion efficiency from 1.26% to 2.51% hence demonstrating enhancement by the factor of 100%. The device was further characterized using electronic absorption spectroscopy, photoluminescence spectroscopy, electrochemical impedance spectroscopy, and the photovoltage decay kinetics. These studies reveal that the enhanced power conversion efficiency of the device is due to the enhanced charge transfer with the complementary light absorption feature of the interfacial D149 dye molecules.

The present study reports a facile synthetic route for thin film formation of a self-standing 1-D structured array of cobalt hexacyanoferrate crystals using an aqueous solution based ion exchange transformation approach. For this, the cobalt hydroxycarbonate 1-D structured array film was used as a sacrificial precursor template for the ion exchange reaction in aqueous K3[Fe(CN)6] solution. By controlling the reaction, 1-D structured array film, or particulate structured film of the cobalt hexacyanoferrate crystals could be obtained, which thus offered possibilities on morphology-dependent property engineering. The films before and after the ion exchange reaction were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry, energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). Further, electrochemical study of the films was performed using voltammetry, and electrochemical impedance spectroscopy. The study reveals the morphology-dependent electrocatalytic property of the cobalt hexacyanoferrate crystal film on water-oxidation. The 1-D structured array film of the cobalt hexacyanoferrate crystals has demonstrated superior electrocatalytic performance on water-oxidation from alkaline and neutral electrolytes, which is competitive to the catalytic performance demonstrated by many outstanding water-oxidation catalysts.