Unique hierarchical SiO2@ZnIn2S4 marigold flower like nanoheterostructure for solar hydrogen production.

The novel marigold flower like SiO2@ZnIn2S4 nano-heterostructure was fabricated using an in situ hydrothermal method. The nanoheterostructure exhibits hexagonal structure with marigold flower like morphology. The porous marigold flower assembly was constructed using ultrathin nanosheets. Interestingly, the thickness of the nanopetal was observed to be 5-10 nm and tiny SiO2 nanoparticles (5-7 nm) are decorated on the surface of the nanopetals. As the concentration of SiO2 increases the deposition of SiO2 nanoparticles on ZnIn2S4 nanopetals increases in the form of clusters. The optical study revealed that the band gap lies in the visible range of the solar spectrum. Using X-ray photoelectron spectroscopy (XPS), the chemical structure and valence states of the as-synthesized SiO2@ZnIn2S4 nano-heterostructure were confirmed. The photocatalytic activities of the hierarchical SiO2@ZnIn2S4 nano-heterostructure for hydrogen evolution from H2S under natural sunlight have been investigated with regard to the band structure in the visible region. The 0.75% SiO2@ZnIn2S4 showed a higher photocatalytic activity (6730 µmol-1 h-1 g-1) for hydrogen production which is almost double that of pristine ZnIn2S4. Similarly, the hydrogen production from water splitting was observed to be 730 µmol-1 h-1 g-1. The enhanced photocatalytic activity is attributed to the inhibition of charge carrier separation owing to the hierarchical morphology, heterojunction and crystallinity of the SiO2@ZnIn2S4.

Ionic Liquid-Responsive Phase Transfer of Gold Nanoparticles: Anionic Metathesis.

In this work, a fresh approach has been proposed for the efficient transfer of gold nanoparticles (AuNPs) from an aqueous to organic phase by the metathesis reaction or anion exchange reaction. Here, we synthesized ionic liquid 1-butyl 3-hexadecyl imidazolium bromide [C4C16Im]Br-stabilized AuNPs which exhibit excellent stability in solution. Transfer of Au@[C4C16Im]Br from an aqueous to organic phase was investigated by the metathesis reaction with different hydrophobic ionic liquid-forming salts such as LiNTf2, LiClO4, and KPF6. The anionic exchange process in ionic liquids at the AuNP surface to make hydrophilic to hydrophobic AuNPs is demonstrated. It was found that hydrophobic ionic liquids provide the most effective transfer of AuNPs from the aqueous to organic phase. Interestingly, we have noticed no change in color, size, and shape of AuNPs for more than a month, indicating more efficient transfer of AuNPs in organic solvents, which remained stable for over a month. The ionic liquids with anions NTf2-, ClO4-, and PF6- make the AuNP surface hydrophobic, indicating their good dispersibility in nonpolar solvents. Finally, these AuNPs exhibit excellent sensitivity toward the refractive index of organic solvents, which is correlated with the surface plasmon resonance (SPR) λSPR bands.

Solar-light-active mesoporous Cr-TiO2 for photodegradation of spent wash: an in-depth study using QTOF LC-MS.

A dark-coloured effluent called "spent wash" is generated as an unwanted product in sugarcane-based alcohol distilleries. Most distilleries discharge this effluent into soil or water without any treatment, causing water and soil pollution. Herein, we report chromium-doped TiO2 (Cr-TiO2) as a photocatalyst for the degradation of spent wash colour under natural sunlight. Cr-doped TiO2 nanoparticles were prepared using an aqueous titanium peroxide-based sol-gel method with titanium isopropoxide as the Ti precursor and chromium nitrate as the Cr precursor. To observe the effect of dopant on sol-gel behaviour and physicochemical properties, the Cr concentration was varied in the range 0.5-5 wt%. The crystallization temperature and time were optimized to obtain the required phase of Cr-TiO2. The physicochemical characteristics of the Cr-doped TiO2 catalyst were determined using X-ray diffraction, FE-SEM, FETEM, TG, XPS, the Brunauer-Emmett-Teller (BET) method, FT-IR, Raman, PL, ICP-MS, and UV visible spectroscopy. A shift in the absorption edge of TiO2 by doping with chromium suggested an increase in visible light absorption due to a decrease in the effective band gap. The application potential of the Cr-TiO2 catalyst was studied in the degradation of sugar-based alcohol distillery waste under natural sunlight, and the results were compared with those of undoped TiO2 and Degussa P25 TiO2. Degradation of the spent wash solution was monitored using UV-visible, gel permeation chromatography (GPC), and QTOF LC-MS. GPC and LC-MS showed significant changes in the molecular weight of spent wash colour-forming compounds due to the degradation reaction. QTOF LC-MS analysis suggested that acids, alcohols, glucosides, ketones, lipids, peptides, and metabolites were oxidized to low-molecular-weight counterparts. From the results, 5% Cr-TiO2 showed the highest degradation rate among all Cr-TiO2 samples, undoped TiO2, and Degussa P25 TiO2 under identical reaction conditions, with nearly 68-70% degradation achieved in 5 h.

Bioinspired Carbon Quantum Dots: An Antibiofilm Agents.

Carbon dots, very tiny carbon material with various surface passivations, have emerged as a new class of nanomaterials for various applications. Herein, we describe a simple, economical, and green approach for the synthesis of colloidal luminescent carbon dots (C-dots) by solvothermal method from fruit juice of Citrus limetta, an abundantly available plant in Asian countries. The existence of C-dots was confirmed by X-ray Diffraction and High Resolution Transmission Electron Microscopy studies. The C-dots size was observed to be 2-4 nm. We further evaluated the efficacy of C-dots to inhibit the attachment of Candida albicans MTCC 227, and biofilm formation on the polystyrene surfaces. The C-dots have effectively inhibited the attachment and formation of biofilm in Candida albicans at very low concentrations, which is hitherto unattempted. The ability of C-dots to inhibit biofilm formation may contribute to diverse applications of C-dots in biomedical field.

Growth study of hierarchical Ag3PO4/LaCO3OH heterostructures and their efficient photocatalytic activity for RhB degradation.

We have demonstrated the synthesis of Ag3PO4/LaCO3OH (APO/LCO) heterostructured photocatalysts by an in situ wet chemical method. From pre-screening evaluations of photocatalysts with APO/(x wt% LCO) composites with mass ratios of x = 5, 10, 15, 20, 25 and 30 wt%, we found that the APO/LCO (20 wt%) exhibited a superior photocatalytic activity for organic pollutant remediation. Therefore, an optimised photocatalyst APO/LCO (20 wt%) is selected for the present study and we investigate the effect of a mixed solvent system (H2O:THF) on the morphology, which has a direct effect on the photocatalytic performance. Interestingly, a profound effect on the morphological features of APO/LCO20 heterostructures was observed with variation in the ratio of the solvent system. From the FESEM study it is observed that the LCO spherical nanoparticles are transformed into nanorods with the variation of THF into the solvent system. Moreover, these LCO nanorods make intimate contact with the APO microstructures which is helpful for the improvement of the photocatalytic activity. The photocatalytic activities of the APO/LCO composites with different solvent ratios were evaluated by the degradation of rhodamine B (RhB) under visible light irradiation. Excellent photocatalytic activity was observed for the APO/LCO-2 (H2O : THF = 60 : 40) sample. This might be due to uniform covering of the APO microstructures by fine LCO rod-like structures offering intimate contact between the APO and LCO and providing proper channels for the degradation reactions. Furthermore, with an increasing THF volume ratio in the reaction system there was an increase of the dimensions of the LCO rod-like structures and also a loose compactness of their uniform intimate contact between the APO/LCO heterostructures. All in all, the enhanced photocatalytic activity of the APO/LCO heterostructures is attributed to the collective co-catalytic effect of LCO, by providing accelerated charge separation through the heterojunction interface, and THF, by helping to tune the unique morphological features which eventually facilitate the photocatalysis process.

Fern-like rGO/BiVO4 Hybrid Nanostructures for High-Energy Symmetric Supercapacitor.

Herein, we demonstrate the synthesis of rGO/BiVO4 hybrid nanostructures by facile hydrothermal method. Morphological studies reveal that rGO sheets are embedded in the special dendritic fern-like structures of BiVO4. The rGO/BiVO4 hybrid architecture shows the way to a rational design of supercapacitor, since these structures enable easy access of electrolyte ions by reducing internal resistance. Considering the unique morphological features of rGO/BiVO4 hybrid nanostructures, their supercapacitive properties were investigated. The rGO/BiVO4 electrode exhibits a specific capacitance of 151 F/g at the current density of 0.15 mA/cm2. Furthermore, we have constructed rGO/BiVO4 symmetric cell which exhibits outstanding volumetric energy density of 1.6 mW h/cm3 (33.7 W h/kg) and ensures rapid energy delivery with power density of 391 mW/cm3 (8.0 kW/kg). The superior properties of symmetric supercapacitor can be attributed to the special dendritic fern-like BiVO4 morphology and intriguing physicochemical properties of rGO.

Magnetically separable Ag3PO4/NiFe2O4 composites with enhanced photocatalytic activity.

Magnetically separable Ag3PO4/NiFe2O4 (APO/NFO) composites were prepared by an in situ precipitation method. The photocatalytic activity of photocatalysts consisting of different APO/NFO mass ratios was evaluated by degradation of methylene blue (MB) under visible light irradiation. The excellent photocatalytic activity was observed using APO/NFO5 (5% NFO) composites with good cycling stability which is higher than that of pure Ag3PO4 and NiFe2O4. All the APO/NFO composites showed good magnetic behavior, which makes them magnetically separable after reaction and reusable for several experiments. Photoconductivities of pure and composite samples were examined to study the photoresponse characteristics. The current intensity greatly enhanced by loading NFO to APO. Furthermore, the photocatalytic performance of the samples is correlated with the conductivity of the samples. The enhancement in the photocatalytic activity of APO/NFO composites for MB degradation is attributed to the excellent conductivity of APO/NFO composites through the co-catalytic effect of NFO by providing accelerated charge separation through the n-n interface.

In-situ preparation of N-TiO2/graphene nanocomposite and its enhanced photocatalytic hydrogen production by H2S splitting under solar light.

Highly monodispersed nitrogen doped TiO2 nanoparticles were successfully deposited on graphene (N-TiO2/Gr) by a facile in-situ wet chemical method for the first time. N-TiO2/Gr has been further used for photocatalytic hydrogen production using a naturally occurring abundant source of energy i.e. solar light. The N-TiO2/Gr nanocomposite composition was optimized by varying the concentrations of dopant nitrogen and graphene (using various concentrations of graphene) for utmost hydrogen production. The structural, optical and morphological aspects of nanocomposites were studied using XRD, UV-DRS, Raman, XPS, FESEM, and TEM. The structural study of the nanocomposite shows existence of anatase N-TiO2. Further, the details of the components present in the composition were confirmed with Raman and XPS. The morphological study shows that very tiny, 7-10 nm sized, N-TiO2 nanoparticles are deposited on the graphene sheet. The optical study reveals a drastic change in absorption edge and consequent total absorption due to nitrogen doping and presence of graphene. Considering the extended absorption edge to the visible region, these nanocomposites were further used as a photocatalyst to transform hazardous H2S waste into eco-friendly hydrogen using solar light. The N-TiO2/Gr nanocomposite with 2% graphene exhibits enhanced photocatalytic stable hydrogen production i.e. ∼5941 µmol h(-1) under solar light irradiation using just 0.2 gm nanocomposite, which is much higher as compared to P25, undoped TiO2 and TiO2/Gr nanocomposite. The enhancement in the photocatalytic activity is attributed to 'N' doping as well as high specific surface area and charge carrier ability of graphene. The recycling of the photocatalyst shows a good stability of the nanocomposites. This work may provide new insights to design other semiconductor deposited graphene novel nanocomposites as a visible light active photocatalyst.

Template-free synthesis of nanostructured Cd(x)Zn(1-x)S with tunable band structure for H2 production and organic dye degradation using solar light.

We have demonstrated a template-free large-scale synthesis of nanostructured Cd(x)Zn(1-x)S by a simple and a low-temperature solid-state method. Cadmium oxide, zinc oxide, and thiourea in various concentration ratios are homogenized at moderate temperature to obtain nanostructured Cd(x)Zn(1-x)S. We have also demonstrated that phase purity of the sample can be controlled with a simple adjustment of the amount of Zn content and nanocrystalline Cd(x)Zn(1-x)S(x = 0.5 and 0.9) of the hexagonal phase with 6-8 nm sized and 4-5 nm sized Cd(0.1)Zn(0.9)S of cubic phase can be easily obtained using this simple approach. UV-vis and PL spectrum indicate that the optical properties of as synthesized nanostructures can also be modulated by tuning their compositions. Considering the band gap of the nanostructured Cd(x)Zn(1-x)S well within the visible region, the photocatalytic activity for H2 generation using H2S and methylene blue dye degradation is performed under visible-light irradiation. The maximum H2 evolution of 8320 µmol h(-1)g(-1) is obtained using nanostructured Cd(0.1)Zn(0.9)S, which is four times higher than that of bulk CdS (2020 µmol h(-1) g(-1)) and the reported nanostructured CdS (5890 µmol h(-1)g(-1)). As synthesized Cd(0.9)Zn(0.1)S shows 2-fold enhancement in degradation of methylene blue as compared to the bulk CdS. It is noteworthy that the synthesis method adapted provides an easy, inexpensive, and pollution-free way to synthesize very tiny nanoparticles of Cd(x)Zn(1-x)S with a tunnable band structure on a large scale, which is quite difficult to obtain by other methods. More significantly, environmental benign enhanced H2 production from hazardous H2S using Cd(x)Zn(1-x)S is demonstrated for the first time.

Nanocrystalline zinc indium vanadate: a novel photocatalyst for hydrogen generation.

Hydrogen is a future fuel and hence production of cheap hydrogen is an important area of research. Recently, the photocatalysts were used to generate hydrogen from water and hydrogen sulfide splitting under solar light. Hence, we designed Zinc Indium Vanadate, a novel visible light active photocatalyst and used for the generation of hydrogen by using solar light. We have demonstrated the synthesis of ZnIn2V2O9 (ZIV) catalyst by sonochemical route using NH4VO3, In (NO3)3 and Zn(CH3COO)2 as a precursors and PVP as a capping agent. The obtained product was further characterized by XRD, UV-DRS and FESEM. The XRD pattern reveals the existence of monoclinic crystal structure and broader peaks indicating the nanocrystalline nature of the material. The particle size was observed in the range of 50-70 nm. The optical study showed the absorption edge cut off at 520 nm with estimated band gap about 2.3 eV. Considering the band gap in visible range, ZnIn2V2O9 was used as a photocatalyst for photodecomposition of H2S under visible light irradiation to produce hydrogen. We observed excellent photocatalytic activity for the hydrogen generation by using this photocatalyst.

Hierarchical nanostructured ZnO with nanorods engendered to nanopencils and pin-cushion cactus with its field emission study.

In the present investigation, we report the synthesis of highly crystalline ZnO nanorods engendered to pin-cushion cactus and 1D nanopencil like nanoforms on zinc (Zn) foil via a simple sonochemical assisted hydrothermal route. The work reported herewith is attractive for two reasons: (i) the facile one step solution approach assisted by prior ultrasonication converts nanorods/nanobelts into nanopencils, and (ii) the sharp and quasi-aligned ZnO nanopencils are potential field electron emitters. In addition, the controlled growth of pinhole like ZnO nanopencils and aligned hexagonal ZnO nanodisc was obtained. The changes in the growth rate, diameter, density, and surface area of highly oriented ZnO nanorods are examined. Considering the significances of such novel morphologies, technically detailed formation mechanism has been proposed. The field emission study of pin-cushion cactus like ZnO nanopencils was performed. Field emission measurements demonstrate remarkably low turn-on field which is explained on the basis of a sequential enhancement mechanism involving the consecutive stem and tip contribution. The Folwer-Nordheim (F-N) plot showed nonlinear behavior indicating the semiconducting nature of the emitter. Significantly, emission current is stable at the preset value of 3 µA over the period of 3 h. The simplicity of the synthesis route coupled with the promising emission properties is envisaged to be an important candidate for potential nanoelectronic devices. These unique imperative ZnO nanostructures may have potential for sensors, solar cell, photocatalysis, varisters, etc.

Exhaustive analysis of frontal copolymerization of functionalized monovinyl and divinyl monomers.

A series of copolymers of 2-hydroxyethyl methacrylate (HEMA)/glycidyl methacrylate (GMA) and ethylene dimethacrylate (EGDM) were synthesized by frontal polymerization (FP). This study was conducted to investigate the effect of crosslink density, type and concentration of initiator, the use of a complex initiator system, porogen, and diluent on the most relevant parameters of FP, such as sustainability of the front, temperature profile, front velocity, and yield. The products were also characterized for intruded pore volume, pore-size distribution, epoxy-functionality number, and surface morphology. Higher crosslink densities (CLDs) and initiator concentration produced higher front velocities, whereas no trend in front temperature was noted. A complex initiation system was effective in stabilizing and increasing the polymerization yield. Relative to suspension polymerization (SP), FP products synthesized without a solvent were microporous, whereas micro-to-macroporous products were obtained in the presence of a solvent (for HEMA-EGDM polymers). We also present, explain, and discuss the exotic patterns observed under a microscope. We observed two basic types of spatial patterns, namely, planar and nonplanar patterns. The type of planar pattern observed under scanning electron microscopy (SEM) has a spatial impulse that appears as a loop followed by regular periodic motion in the radial and axial directions. This behavior gives rise to a repeating pattern that is a few microns thick. Also, nonplanar patterns, namely, layered concentric rings and winding staircase patterns, were observed under SEM.