Sol-gel based simonkolleite nanopetals with SnO2 nanoparticles in graphite-like amorphous carbon as an efficient and reusable photocatalyst

We report a new sol-gel nanocomposite (STC) having simonkolleite nanopetals (SC) and quasi-spherical tin oxide (SO) nanoparticles embedded in graphite-like amorphous carbon (C) as an efficient and reusable photocatalyst for the degradation of rhodamine 6G dye under UV (254 nm) illumination. The STC was synthesized using vacuum curing (450 degrees C) of precursor gel derived from a sol (Zn : Sn, 2 : 1) in 2-methoxyethanol with acetylacetone. The presence of tetragonal SO well decorated on rhombohedral SC forming nanoheterostructures in the carbon matrix was identified by X-ray diffraction, micro-Raman and X-ray photoelectron spectroscopy and electron microscopes (field emission scanning electron and transmission electron) studies. Carbon content and thermal weight loss behaviour in STC were studied by carbon determinator and thermogravimetry. The nanocomposite showed high photocatalytic activity (10(-5) M dye solution degraded completely in 32 min). Reusability test of the photocatalyst exhibited about 95% of dye degradation after five successive recycles. In addition to accelerating photo-induced charge carrier separation and electron transport in the nanoheterostructures as revealed from electrochemical impedance spectroscopy response of the UV-exposed nanocomposite, an active role of the carbon at an optimum content (similar to 18%) was found for generating high BET specific surface area (similar to 143 m(2) g(-1)). This simple synthesis strategy could open a new avenue to the development of sol-gel nanocomposites as efficient and reusable photocatalysts from various simonkolleite-based metal oxide semiconductors embedded in graphite-like amorphous carbon

Effect of Ga doping on Microstructural, Optical and Photocatalytic Properties of Nanostructured Zinc Oxide Thin Films

Ga doped nanostructured zinc oxide thin films (thickness, 160-170 nm) on pure silica glass substrate were prepared from zinc acetate based precursor solutions by varying Ga doping level (0 to 6%). The presence of nanocrystalline hexagonal ZnO was confirmed by X-ray diffraction study whereas the field emission scanning and transmission electron microscopic analyses evidenced the existence of quasi-spherical ZnO with a decreased trend in crystallite/particle size vis-à-vis an enhancement of direct band gap energy of the films on increasing the doping level. Root means square (RMS) film surface roughness was determined by atomic force microscope and found maximum RMS roughness value in 1% doped film. Photoluminescence (PL) emission spectral study revealed the formation of various intrinsic/extrinsic defects along with the presence of characteristics band edge emission of ZnO at ~ 385 nm (UVPL). However, a lowest relative intensity of the UVPL emission was found in 1% doped film (G1ZO), indicating an appreciable decrease in the recombination rate of photogenerated charge carriers in the semiconductor. The photocatalytic activity of the films towards degradation of rhodamine 6G dye was performed under UV (254 nm) and obtained the maximum value of dye degradation rate constant (considering first order reaction kinetics) in 1% doped film (G1ZO). On increasing doping level, the trend in change of defect concentration (oxygen vacancies) as analyzed by Raman spectral study was found identical with the dye photodegradation activity of the films. The G1ZO film would expect to decompose micro-organisms even under exposure of visible light

Indium Oxide Based Nanomaterials: Fabrication Strategies, Properties, Applications, Challenges and Future Prospect

Nanostructured metal oxide semiconductors (MOS) in the form of thin film or bulk attract significant interest of materials researchers in both basic and applied sciences. Among these important MOSs, indium oxide (IO) is a valuable one due to its novel properties and wide range of applications in diversified fields. IO based nanostructured thin films possess excellent visible transparency, metal-like electrical conductivity and infrared reflectance properties. This chapter mainly highlights the synthesis strategies of IO based bulk nanomaterials with variable morphologies starting from spherical nanoparticles to nano-rods, nano-wires, nano-needles, nanopencils, nanopushpins etc. In addition, thin film deposition and periodic 1-dimensional (1D)/2-dimensional (2D) surface texturing techniques of IO based nanostructured thin films vis-à-vis their functional properties and applications have been discussed. The chapter covers a state-of-the-art survey on the fabrication strategies and recent advancement in the properties of IO based nanomaterials with their different areas of applications. Finally, the challenges and future prospect of IO based nanomaterials have been discussed briefly

Approximation of Rough Soft Set and Its Application to Lattice

The approximation of soft set is presented in modified soft rough (MSR) approximation space in this paper, i.e., approximation of an information system with respect to another information one. Besides, the concept of rough soft set is introduced in a modified soft rough approximation space. Various properties are studied like subset, union, intersection on rough soft set with some propositions presented on rough soft set. Moreover, the measure of roughness of soft set is defined in MSR-approximation space and the order relation is introduced on soft set. Furthermore, lattice theory is studied in the MSR-approximation space under a modified rough soft environment. Finally, some realistic examples are considered to usefulness and illustrate of the paper

Effect of precursor sol pH on microstructural, optical and photocatalytic properties of vacuum annealed zinc tin oxide thin films on glass

Dip coated vacuum annealed zinc tin oxide thin films on soda lime silica glass have been deposited from the precursor sols containing zinc acetate dihydrate and tin (IV) chloride pentahydrate (Zn:Sn = 67:33, atomic ratio in percentage) in 2-methoxy ethanol by varying sol pH (0.85-5.5). Crystallinity, morphology, optical and photocatalytic properties of the films strongly depend on sol pH. Measurement of grazing incidence X-ray diffraction confirms the presence of hexagonal nano ZnO in the films derived from the sols of pH < 5.5. Film crystallinity deteriorates on increasing sol pH and the film deposited from the sol of pH 5.5 shows XRD amorphous but the selected area diffraction pattern and HRTEM image evidence the presence of nano Zn2SnO4 (size, 5-6 nm). Direct band gap energy of films increases on increasing sol pH. To visualize the film surface microstructure, FESEM study has been done and a rod-like surface feature is revealed in the film deposited from the sol of pH 2.85. A dependence of precursor sol pH on the photocatalytic activity of films towards degradation of Rhodamine 6G dye under UV (254 nm) irradiation is found and the highest decomposition rate constant, `k' value is obtained from the film prepared from the sol of pH 5.5. The presence of zinc deficient nano Zn2SnO4 in the film may consider for generating the highest `k' value. We also measure gelling time, viscosity of sols as well as UV and FTIR studies on the films and propose chemical reactions

Influence of Surface Defects and Size on Photochemical Properties of SnO2 Nanoparticles

We report the successful synthesis of surface defective small size (SS) SnO2 nanoparticles (NPs) by adopting a low temperature surfactant free solution method. The structural properties of the NPs were analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The presence of surface defects, especially oxygen vacancies, in the sample were characterized using micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence emission. The Brunauer&ndash;Emmet&ndash;Teller (BET) nitrogen adsorption&ndash;desorption isotherms demonstrated the superior textural properties (high surface area and uniform pore size) of SS SnO2 compared to large size (LS) SnO2. A comparable study was drawn between SS SnO2 and LS SnO2 NPs and a significant decrease in the concentration of surface defects was observed for the LS sample. The results showed that surface defects significantly depend upon the size of the NPs. The surface defects formed within the band gap energy level of SnO2 significantly participated in the recombination process of photogenerated charge carriers, improving photochemical properties. Moreover, the SS SnO2 showed superior photoelectrochemical (PEC) and photocatalytic activities compared to the LS SnO2. The presence of a comparatively large number of surface defects due to its high surface area may enhance the photochemical activity by reducing the recombination rate of the photogenerated charges

Fabrication, structural evaluation, optical and photoelectrochemical properties of soft lithography based 1D/2D surface patterned indium titanium oxide sol-gel thin film

For the first time, we report on successful fabrication of 1-dimensional (ID) nanoprism and 2-dimensional (2D) nanocone shaped surface patterned amorphous indium titanium oxide (INTO) sol-gel based mesoporous thin films on glass by soft lithography. Structural evaluation of the surface patterns over amorphous thin film surfaces was performed by atomic force and transmission electron microscopes as well as X-ray diffraction study. Chemical bonding/oxidation state of constituent elements in INTO film matrix was analyzed by FTIR and X-ray photoelectron spectroscopies. Maximum optical absorption and minimum specular surface reflection in visible region were noticed in 20 patterned film. The thin film with physical thickness over 100 nm was mesoporous in nature (similar to 14% porosity) as measured by spectroscopic ellipsometer. A significant improvement in photoelectrochemical (PEC) activity was found in 2D patterned film under visible light that could be associated with the enhancement in light absorption/trapping by the periodic nanocones. Moreover, the existence of mesopores could provide excess active sites for electrolyte diffusion and mass transportation. Thus, the mesoporous 2D patterned thin film could have substantial opportunity in solar energy conversion. The facile technique could create an avenue for fabrication of complexed surface patterned thin films with improved PEC property. (C) 2017 Elsevier B.V. All rights reserved

Low temperature synthesis of graphene hybridized surface defective hierarchical core-shell structured ZnO hollow microspheres with long-term stable and enhanced photoelectrochemical activity

The present work reports on successful in situ synthesis of chemically converted graphene (CCG) hybridized, surface defective core-shell structured ZnO hollow microspheres (ZG-CSHM) from a surfactant/template free precursor by adopting a low temperature solution method. This special architecture has been synthesized as an intermediate product between solid and hollow microspheres via Ostwald ripening process by optimizing the reaction time, as observed by field emission scanning and transmission electron microscopic studies. The samples have also been characterized by X-ray photoelectron, FTIR and Raman spectral as well as X-ray diffraction analyses. From textural property measurement by BET N-2 adsorption-desorption isotherms, it is seen that the ZG-CSHM possesses an enhanced specific surface area with narrow distribution of mesopores. Relatively higher photoelectrochemical activity with long term stability of ZG-CSHM is found compare to pristine core-shell structured ZnO hollow microspheres. The synergic effect of graphene hybridization and the presence of surface defects of ZnO nanoparticles in the mesoporous sample can play the key roles in advancing its photoelectrochemical activity. The surface defects can prolong the recombination rate of photogenerated charge carriers and the high surface area with narrow sized mesopore distribution can provide large number of active sites, make electrolyte diffusion and mass transportation easier. The ZG-CSHM sample also shows an improved photocurrent density compare to solid and hollow microspheres. Moreover, the existence of chemically interacted CCG with ZnO inhibits the photocorrosion, resulted long-term stable photoelectrochemical activity of ZG-CSHM. This facile process can create an avenue for synthesis of core-shell structured microspheres from different metal oxide semiconductors for improving their photoelectrochemical activity

Influence of Al doping on microstructural, optical and photocatalytic properties of sol-gel based nanostructured zinc oxide films on glass

Al doped nanostructured zinc oxide thin films (thickness, 165 +/- 5 nm) on silica glass were prepared from zinc acetate based solutions of varying dopant content (0 to 10 at% with respect to Zn). X-ray diffraction confirmed the presence of nanocrystalline hexagonal ZnO. On increasing the doping level, we observed a change in ZnO morphology (spherical, hexagon and plate-shaped) under field emission scanning and transmission electron microscopes and a gradual decrease of ZnO crystallite size (14.0 to similar to 10 nm) vis-a-vis an enhancement of direct band gap energy of the films. Root mean square film surface roughness and chemical state of elements were studied by atomic force microscopy and X-ray photoelectron spectroscopy respectively. In addition to common intrinsic defects in ZnO, a defect (designated as D-ZA(center dot), appearing as a paramagnetic singly negatively charged oxygen vacancy) was identified up to 4% doping from the appearance of photoluminescence emission at 398 nm and measurement of paramagnetic property of the films. Film photocatalytic activity towards Rhodamine 6G dye decomposition was performed under UV (254 nm) irradiation and the film with 4% doping (A4ZO) showed the highest value of first order decomposition rate constant. On increasing Al content, the trend of change of defect concentration (oxygen vacancies) analyzed by Raman spectra was found to be identical with the dye photodecomposition activity (PA) of the films. A major role of D-ZA(center dot) towards the PA was explored under visible light. We proposed the reaction mechanism of PA based on the experimental results. The A4ZO would be expected to decompose micro-organisms under visible light