Composite of graphitic carbon nitride and TiO2 as photo-electro-catalyst in microbial fuel cell.

The widespread application of surfactants and their subsequent discharge in the receiving water bodies is a very common issue in developing countries. In the present investigation, a composite of graphitic carbon nitride (GCN) and TiO2 was used as a photo-electro-catalyst in a microbial fuel cell (MFC)-based hybrid system for bio-electricity production and simultaneous pollutant removal (organic matter and sodium dodecyl sulphate, SDS). The GCN: TiO2 composite with a ratio of 70:30 (by wt. %) revealed a better electrochemical response; thus, it was used as a photo-electro-catalyst in MFC. Additionally, the photochemical characterization indicated a decrease in the band gap and charge recombination of GCN-TiO2 composite compared to standalone TiO2, which indicated a conducive effect of GCN addition. Further, on the actual use as a photo-electro-catalyst, the GCN-TiO2 catalysed MFC attained 58.2 ± 9.6% and 86.5 ± 7.1% of COD and SDS removal; while simultaneously harvesting a maximum power density of 1.07 W m-3, which was higher than standalone TiO2-catalysed MFC. The follow-up treatment in the charcoal bio-filter and photo-cathodic chamber of the hybrid system further improved the overall COD and SDS removal efficiency to 92.1 ± 2.7 and 95.6 ± 1.5%, respectively. The electro-catalytic performance of the GCN-TiO2 can be attributed to the presence of nitrogen-active species in the composite. The results of this investigation demonstrated a potential MFC-based hybrid system for the simultaneous secondary and tertiary treatment of municipal wastewater. Consequently, the outcome of this investigation indicates an innovative research direction in the field of photo-electro-catalyst, which can fit into the role of a photo-catalyst as well as an electro-catalyst.

Double Effects of Interfacial Ag Nanoparticles in a ZnO Multipod@Ag@Bi2S3 Z-Scheme Photocatalytic Redox System: Concurrent Tuning and Improving Charge-Transfer Efficiency.

Distinct functional materials in their combined form in a well-designed hybrid architecture offer great possibilities for creating a highly active photocatalytic system. Herein, a uniform multipod-shaped ZnO is synthesized through a natural template assisted route and progressively integrated with Ag nanoparticles (NPs) and Bi2S3 to form a three-component (3C) ternary photocatalytic system by a facile, two -step wet chemical approach. Encapsulation of polycrystalline Bi2S3 and assimilation of Ag NPs in between the interface of ZnO and Bi2S3 in the ternary hybrid are confirmed from electron microscopy and X-ray photoelectron spectroscopy, which resulted in improved UV-vis absorption, charge separation efficiency, and photocurrent response evaluated from optical absorption spectroscopy, photoluminescence, and photoelectrochemical cell measurements. This ternary hybrid shows high photoredox activity toward the hydrogen evaluation reaction (HER) (218.7 µmol h-1 g-1) and methyl orange (MO) oxidation (k = 3.21 × 10-2 min-1) compared to their binary and single counterparts. Moreover, on the basis of the estimation of the predominant active species (O2•-, •OH) in the photoredox catalysis and band edge positions from the Mott-Schottky plot, it was determined that both binary ZnO multipod@Bi2S3 and ternary ZnO multipod Ag@Bi2S3 hybrids undergo a Z-scheme electron transfer mechanism under irradiation of light. Here, the Ag ingredient in the ternary hybrids acts as an interfacial charge-transfer mediator to accelerate the Z-scheme electron transfer between Bi2S3 and ZnO along with plasmonic photosensitization to trigger the generation of plasmon-induced hot electrons. Such a cooperative concurrent dual role of Ag NPs in the Z-scheme ternary hybrid system considerably boosts the photoredox performance compared to direct Z-scheme binary hybrids. This work will enlighten and uncover the essential roles of metal NPs along with their cooperative synergy in Z-scheme photocatalytic systems as a prototypical example for substantial solar energy conversion.

Strategic Synthesis of SiO2-Modified Porous Co3O4 Nano-Octahedra Through the Nanocoordination Polymer Route for Enhanced and Selective Sensing of H2 Gas over NO x.

In this work, a strategic synthesis of Co3O4 nano-octahedra was developed through the facile nanoscale coordination polymer (NCP) route, which was further modified by SiO2 to be used as a sensor for enhanced sensing of hydrogen. The Co(II)-NCP-derived Co3O4 octahedra and SiO2-modified Co3O4 octahedra were characterized using Fourier transform infrared, powder X-ray diffraction, Brunauer-Emmett-Teller, thermogravimetric analysis, field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature-programmed reduction (H2TPR) techniques. The SiO2-modified Co3O4 sensor exhibited a stronger and selective electrical response to H2 gas over NO x at 225 °C than Co(II)-NCP-derived Co3O4 octahedra and the conventional Co3O4 powder. The composite sensor shows faster recovery and significant repeatability than the other two. The enhancement in the sensing performance of the SiO2-modified Co3O4 octahedron was explained by the effectiveness of surface modification, controlled morphology, and combination of synergistic effect of Co3O4 and SiO2. Surface engineering of the as-prepared Co3O4 nano-octahedra with an exposed (111) surface plane and later SiO2 modification facilitates effective gas adsorption, resulting in enhancement in sensing and selectivity over NO x . The details of the synergistic effect and the plausible reasons for the improvement in gas-sensing parameters are discussed here. This study would offer new directions for development on the controlled synthesis of porous materials, in general, and in gas sorption or sensing, in particular.

Effective oil removal from water by magnetically driven superhydrophobic and oleophilic magnetic titania nanotubes.

Development of efficient techniques to combat the harmful effects of oil spill is an emerging field, where fabrication of new sorbents for selective removal of oil has become a hot topic for environmental scientists. The present study reports the preparation of superhydrophobic/oleophilic magnetic titania nanotubes via a facile hydrothermal method, followed by the treatment with octadecylamine, as potential magnetically driven sorbent for selective removal of oil from water surface. The magnetic nature (superparamagnetism at 300 K) of the nanotubes enabled magnetic removal of the oil-sorbed material from water surface. Wettability test of the material depicted a static water contact angle of 166 ± 1°, indicating its superhydrophobic character. Oil uptake experiments and contact angle measurements revealed its superoleophilicity with maximum oil sorption capacity >1.5 g/g for a variety of oils. In addition to the ease of magnetic removal, the nanotubes possess sufficient buoyancy, high selectivity, and quick rate of oil uptake and is more than five times reusable.

Ru(ii)-Metal complex immobilized mesoporous SBA-15 hybrid for visible light induced photooxidation of chlorophenolic compounds in aqueous medium.

The work focuses on room-temperature photocatalytic degradation of phenolic compounds by Ru(ii)-complex immobilized mesoporous silica SBA-15 under visible light in an aqueous medium. The immobilization of [Ru(bpy)3]Cl2 complex on an SBA-15 surface is carried out, and the as-synthesized hybrid is characterized by X-ray Diffraction (XRD), Fourier Transformation IR Spectroscopy (FTIR), Diffuse Reflectance Spectroscopy (DRS), Brunauer-Emmett-Teller analysis (BET), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX) and X-ray Photoelectron Spectroscopy (XPS). Kinetic studies of photodegradation reactions are followed by High Performance Liquid Chromatography (HPLC). Control studies are performed to elucidate the nature of the photodegradation process. The maximum degradation of DCP reached 95% for 10 ppm concentration of the contaminants with an optimum amount of catalyst being 1 g L-1 in 150 min of light irradiation. The long-lived intermediates are identified by HPLC, and the final products are identified by GC-MS. From a series of experiments, the mechanistic steps of the photodegradation process are identified.

Pre-dispersed organo-montmorillonite (organo-MMT) nanofiller: Morphology, cytocompatibility and impact on flexibility, toughness and biostability of biomedical ethyl vinyl acetate (EVA) copolymer.

Polymer-clay based nanocomposites are among the attractive materials to be applied for various applications, including biomedical. The incorporation of the nano sized clay (nanoclay) into polymer matrices can result in their remarkable improvement in mechanical, thermal and barrier properties as long as the nanofillers are well exfoliated and dispersed throughout the matrix. In this work, exfoliation strategy through pre-dispersing process of the organically modified montmorillonite (organo-MMT) nanofiller was done to obtain ethyl vinyl acetate (EVA) nanocomposite with improved flexibility, toughness, thermal stability and biostability. Our results indicated that the degree of organo-MMT exfoliation affects its cytotoxicity level and the properties of the resulting EVA nanocomposite. The pre-dispersed organo-MMT by ultrasonication in water possesses higher degree of exfoliation as compared to its origin condition and significantly performed reduced cytotoxicity level. Beneficially, this nanofiller also enhanced the EVA flexibility, thermal stability and biostability upon the in vitro exposure. We postulated that these were due to plasticizing effect and enhanced EVA-nanofiller interactions contributing to more stable chemical bonds in the main copolymer chains. Improvement in copolymer flexibility is beneficial for close contact with human soft tissue, while enhancement in toughness and biostability is crucial to extend its life expectancy as insulation material for implantable device.

Effective photocatalytic dechlorination of 2,4-dichlorophenol by a novel graphene encapsulated ZnO/Co3O4 core-shell hybrid under visible light.

In the present work, a graphene encapsulated ZnO/Co3O4 (GE/ZnO/Co3O4) core-shell hybrid is fabricated through a facile self-assembly approach, where the mutual electrostatic interaction force drives the ZnO/Co3O4 heteronanostructures to be fully wrapped with flexible ultrathin graphene shells. The as-prepared GE/ZnO/Co3O4 core-shell hybrid is characterized and exhibits excellent visible light photocatalytic ability toward dechlorination of 2,4-dichlorophenol (2,4-DCP) in the aqueous phase. It is worth noting that 2,4-DCP is almost completely mineralized into CO2 and H2O by the GE/ZnO/Co3O4 after 5 h of a photocatalytic reaction. This type of higher dechlorination and mineralization efficiency of 2,4-DCP is not generally observed, and is found to be higher than some previous studies. The dechlorination of 2,4-DCP has been achieved under different parametric conditions. The unique architecture of the GE/ZnO/Co3O4 core-shell hybrid also provides high stability and recyclability towards degradation of 2,4-DCP. The higher photocatalytic activity of the hybrid can be ascribed to the synergistic effect of ZnO, Co3O4 and graphene, and also by an increase in the contact surface between the metal oxide core and the graphene shell, which acts as a continuous path for rapid electron transport to offer a greater number of reactive species.

Development of phosphonate modified Fe 1-x MnxFe2O4 mixed ferrite nanoparticles: novel peroxidase mimetics in enzyme linked immunosorbent assay.

A highly facile and feasible strategy on the fabrication of advanced intrinsic peroxidase mimetics based on Mn(2+) doped mixed ferrite (Mn(II)(x)Fe(II)(1-x)Fe(III)(2)O(4)) nanoparticles was demonstrated for the quantitative and sensitive detection of mouse IgG (as a model analyte). Mn(2+) doped Fe(1-x)Mn(x)Fe(2)O(4) nanoparticles were synthesized using varying ratios of Mn(2+):Fe(2+) ions and characterized by the well known complementary techniques. The increase of Mn(2+) proportion had remarkably enhanced the peroxidase activity and magnetism. The catalytic activity of mixed ferrites was found to follow Michaelis-Menten kinetics and was noticeably higher than native Fe(3)O(4). The calculated K(m) and K(cat) exhibited strong affinity with substrates which were remarkably higher than similar sized native magnetite nanoparticles and horseradish peroxidase (HRP). These findings stimulated us to develop carboxyl modified Fe(1-x)Mn(x)Fe(2)O(4) nanoparticles using phosphonomethyl immunodiacetic acid (PMIDA) to engineer PMIDA-Fe(1-x)Mn(x)Fe(2)O(4) fabricated enzyme linked immunosorbent assay (ELISA). Results of both PMIDA-Fe(1-x)Mn(x)Fe(2)O(4) linked ELISA revealed that the enhancements in absorbance during the catalysis of enzyme substrate were linearly proportional to the concentration of mouse IgG within the range between 0.1 µg/ml and 2.5 µg/ml. Further, this detection was ten times lower than previous reports and the detection limit of mouse IgG was 0.1 µg/ml. The advantages of our fabricated artificial peroxidase mimetics are combined of low cost, easy to prepare, better stability and tunable catalytic activity. Moreover, this method provides a new horizon for the development of promising analytical tools in the application of biocatalysis, bioassays, and bioseparation.