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A facile, fluorine-free and non-toxic one-pot solvothermal technique was adopted to synthesis TiO2 nanoflowers with anatase phase having 98% highly exposed {0 0 1} facets (TiO2 {0 0 1} NFs). The morphology, grain size and crystallinity of pure TiO2 {0 0 1} NFs and reduced graphene oxide (RGO) sheets modified TiO2 {0 0 1} NFs (RGO-TiO2 {0 0 1} NFs) were inspected by diffuse reflectance spectroscopy (DRS), X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM images showed the development of anatase TiO2 {0 0 1} NFs with high crystallinity and uniform shape. The influence of RGO on the performance of the TiO2 {0 0 1} NFs as a photoanode material in dye-sensitized solar cell (DSSC) was examined. High energy conversion efficiency (ɳ) was observed for the DSSC based on a photoanode made of RGO-TiO2 {0 0 1} NFs when compared to DSSCs based on photoanodes fabricated using pure TiO2 {0 0 1} NFs and commercial Degussa P25 TiO2, which exhibited η of 6.78, 4.59 and 2.71%, respectively. The improved performance of the DSSC based on a photoanode composed of RGO-TiO2 {0 0 1} NFs was due to its good crystallinity, high dye intake and enhanced light-harvesting properties. Moreover, the presence of RGO greatly hindered the recombination of photogenerated electrons and increased their lifespan. This work discloses a novel efficient photoanode design for improving performance of the DSSCs.

Chitosan microbeads with C-doped TiO2, N-doped TiO2 and C,N-codoped TiO2 were prepared to obtain photocatalysts with higher photocatalytic efficiency, active under visible light and easy to removed from aqueous medium. TiO2 powders were synthesized by the sol–gel method and modified using glucose and ammonium nitrate as source of C and N, respectively. Scanning electron microscope (SEM), X-ray diffraction (XRD), DRUV–Vis spectra and Raman techniques, were used to characterize the modified TiO2 powders. The structural and physicochemical properties of the microbeads were analyzed by nitrogen physisorption, functional groups were identified by Fourier transform Infrared (FT-IR) spectroscopy and microbeads were observed by optical microscopy. The microbeads photocatalytic efficiency under visible light was evaluated monitoring the E. coli growth-inhibition, determined by colony count analysis (CFU—colony forming units). Results showed effectiveness in all tested composites to inhibit E. coli growth in 24 h under visible light. Furthermore chitosan microbeads with C,N-codoped TiO2 showed the best performance in the degradation test being the most effective composite to achieving 99.99% of E. coli growth inhibition in less than 4 h.

BiFeO3 was synthesized by conventional solid-state reaction method, and its structural, vibrational, electrical, ferroelastic, and multiferroic properties were studied. X-ray diffraction analysis and Rietveld refinement confirmed its rhombohedral crystal structural with the space group of R3c. SEM images show the rectangular shaped micrograins. The stress–strain curves obtained from uniaxial compressive tests with different maximum stresses exhibit hysteresis loops with different remnant strains due to ferroelastic domain switching during compression loading and partial domain switching back upon unloading. From Raman spectra, we have observed 3A1 and 6E modes in the range of 100–600 cm−1. Dielectric constant and dielectric loss were measured as a function of frequency in the range 100 Hz to 1 MHz. The leakage current density was found to be $$8.07\times {10}^{-7}$$ A/cm2 at higher electric field. In further, we performed the ferroelectric, magnetic, and magnetoelectric effect for the confirmation of its multiferroic behavior.

CoFe2O4/ZnO magnetic nanocatalysts were synthesized using a low-frequency ultrasound-assisted technique to enhance the optical, morphological, magnetic and catalytic properties of ZnO. The as-synthesized nanocatalysts were characterized by XRD, Raman, TEM, DR-UV-Vis and VSM analyses in order to confirm the expected modifications of the resulting nanocatalysts. The Raman spectral analysis revealed substitutional Zn2+ in the CoFe2O4/ZnO nanocatalyst. The as-synthesized material was tested for its catalytic activity in the degradation of Acid Blue (AB113), a known textile pollutant. The CoFe2O4 and CoFe2O4/ZnO nanocatalysts revealed the efficient catalytic degradation of AB113 in ambient conditions. The nanocatalyst dosage and the initial concentration of AB113 were varied by fixing one parameter as constant in order to determine the maximum catalytic efficiency with the minimum catalyst loading for AB113 degradation. The CoFe2O4/ZnO nanocatalyst demonstrated 10-fold enhanced mineralization of AB113 compared to the individual bare nanocatalysts, which could be achieved within 3 hours of catalytic degradation of AB113. The magnetic CoFe2O4/ZnO nanocatalyst was found to be stable for six consecutive recycles of AB113 degradation, which indicates that the catalytic efficiency of the nanocatalyst was retained after various numbers of cycles.

Recently, the development of an alternative magnetic refrigerant for the conventional fossil fuels attracts the researchers. We discussed the structural defect-induced magnetocaloric effect (MCE) i...

Synthesis of CeO2, ZnO, and CeO2 nanocubes decorated on the surface of ZnO ovals via a simple hydrothermal method was investigated. The crystalline nature and purity of CeO2, ZnO and CeO2 decorated ZnO were confirmed through X-ray diffraction (XRD) by the co-existence of cubic and hexagonal wurtzite phase of CeO2 and ZnO, respectively. The transmission electron microscopy (TEM) images revealed that CeO2 nanocubes were well decorated on the surface of ZnO in oval morphology. The optical properties of the prepared materials were investigated using diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectra and also, the oxidation species presented in the materials were identified through X-photoelectron spectroscopy (XPS) spectra survey. The photocatalytic activity of CeO2 decorated ZnO nanostructures against methylene blue (MB) as a model pollutant under visible light irradiation was enhanced when compared to those of the pure CeO2 and ZnO nanostructures. The reusability of catalyst studies revealed that the efficiency of the visibility light degradation of MB was increased upon the CeO2 deposited on the ZnO surfaces.

Recent interest and responsibility to retain the water resources rose among people. Scientists have been engaged to develop the mechanism that involves the freely available sunlight - a sustainable resource - to remove the pollutants from water to make it again suitable for life. Ample research was reported in the removal of dye pollutants present in water. For this they have utilized p type and n type semiconductors or combination of both (p-n type) under the excitation of a wide range of electromagnetic band energy. Most of the interest lies in emerging out of the mechanism with hybrid semiconductors to remove the previously reported flaws. Toward this regard, this manuscript aims to develop unique material using the underlying p-n-p model for harnessing visible light in catalysis. Initially, p-n structure was developed with copper oxide (p-type) and zinc oxide (n-type), then polyaniline (p-type) conjugated at different concentrations (0.5 M, 0.7 M & 1.0 M), to yield p-n-p models, using precipitation followed by sonication techniques. Detailed physicochemical investigations were conducted on the resultant p-n-p material to elucidate its characteristics. Furthermore, the mechanism was advocated for the best photocatalytic activity under visible light excitation for the degradation of 4-chlorophenol and compared with the performance of a standard p-n (CuO/ZnO) combination.

In this study, (1 − x) BFO-xCFO (CFO, x = 0.00, 0.05, 0.10 and 0.30) ceramics were synthesized by a solid-state reaction method; their compositions were driven by structural, microstructural, vibrational, electrical, magnetic properties; their enhanced magneto capacitance (MC) effect have also been carried out. Reitveld refinement studies of X-ray diffraction data shows composition-driven structural phase transformation from rhombohedral (R3c) to tetragonal (P4mm). Two phonon scattering Raman modes were observed for the higher wavenumber which supports the crystal structural transition in the BFO-CFO. Ferroelectric polarization shows that the polarization increased with increasing CFO concentration, which describes the changes of the polar symmetry of the crystal structure from rhombohedral (R3c) to tetragonal (P4mm). In Further, the maximum efficiency of energy density (η = 68.65%), reversible energy density of 0.138 J/cm3 and the strong magneto capacitance was observed in 0.9BFO-0.1CFO, which belongs to the morphotropic phase boundary (MPB) region near to the BiFeO3-rich region. The magnetic response analysis has shown, the saturation magnetization (Ms) values of 83 emu/gm and 139 emu/gm for pure CFO and 0.7BFO-0.3CFO composite, respectively, and their magnetic behaviours were also confirmed with Arrott–Belov–Kouvel (ABK) plot.

By this report, we described the facile synthesis technique for the synthesis of hexagonal prism and rod like ZnO nanostructures via simple refluxing route by varying the hexamethylenetetramine and refluxing time. The microstructural parameters such as unit cell volume, bond length, dislocation density and microstrain were extracted from the X-ray diffraction data analysis. The variation in size, shape and morphological details of the prepared nanostructures were discussed using the scanning electron microscope and transmission electron microscope images. The effect of precursors concentration ratio and variation in refluxing time, which played a significant role on the formation of ZnO nanostructures, on the tunability of the aspect ratio was discussed. Also, in relation with these parameters the variation of the band gap and the intensity of (photo luminescence) emission of the nano ZnO was discussed. The obtained results revealed that the microstructural parameters, band gap and luminescence are highly depending on the aspect ratio and the morphology of the ZnO nanostructures. The variation of phonon modes with crystallinity and the phonon life time of the prepared nanostructures were discussed with the Raman spectral data analysis. The photocatalytic activity of the prepared nanostructures with different morphology (prism, rod and bipods) was monitored.

By this report, we discussed about the synthesis and optical properties of pure ceria (nanospheres) and ceria:graphene nanocomposites (nanorice like morphology) which were prepared by using commercial microwave oven as a cost effective and environmental friendly approach. The influence of graphene on the crystallinity, morphology, band gap energy and luminescence of the synthesized samples were deliberately discussed. The obtained average crystallite size, by using Scherrer formula, of the CeO 2 nanostructures exhibited a decreasing trend with increasing the graphene loading. The higher graphene loaded ceria nanocomposites clearly depicted the morphology of nanorice like in shape with the diameter and length as ∼ 6 and ∼ 50 nm, respectively. The presence of graphene and ceria related vibrational modes in FTIR and Raman spectra along with the structural studies supported the successful formation of the nanocomposites. The observed increase in the band gap (blue shift) of nanoceria was discussed. The luminescence related to various F -centers and its quenching in the ceria nanocomposites was discussed.

Photocatalysis offers a promising route to address the challenges of future energy production and anthropogenic environmental pollution. Here we demonstrated the synthesis of a high activity Ag/TiO2 photocatalyst through a two-step, sol-gel and mechanothermal decomposition method employing a silver acetate precursor. Bulk and surface characterization revealed the formation of dispersed metallic silver nanoparticles (∼9 nm diameter) decorating anatase crystallites (∼14 nm) which stabilized a significant concentration of Ti3+ surface species. Synergy between silver and titania enhanced the photophysical properties, narrowing the band gap and suppressing charge-carrier recombination. Ag/TiO2 exhibited good visible light activity and excellent stability over 3 cycles for the aqueous phase photocatalytic degradation of methyl orange dye (38 μmol/h/gcat), and excellent hydrogen production from water splitting (910 μmol/h/gcat).

Structural and mechanical Characterizations of La1.8M0.2NiO4+δ (M: Sr and Ba) prepared by low frequency ultra-sound assisted synthesis technique and sintered at different temperatures were studied. HRTEM and XRD analyses showed the uniform shape of calcined nanocrystalline powders with the particle size of less than 100 nm with mixed phases, which were refined by Rietveld method using orthorhombic (Fmmm) and tetragonal (F4/mmm) structures. Sintering La1.8Sr0.2NiO4+δ and La1.8Ba0.2NiO4+δ compacted discs at temperatures higher than 1300 °C and 1250 °C, respectively, resulted in appearance of extra peaks close to a monoclinic phase. Doping La2NiO4+δ with Sr2+ and Ba2+ did not affect its sinterability and average grain size significantly, however, Ba2+ improved the elastic modulus and microhardness, while Sr2+ improved the fracture toughness.

In this work, the photocatalytic degradation of the antibiotic cefuroxime (CFX) was evaluated by heterogeneous photo-Fenton using Fe2O3-TiO2 as a catalyst under simulated solar radiation and varying the concentration of H2O2 added. The materials Fe2O3-TiO2 modified with different amounts of α-Fe2O3 were prepared by the sol-gel method. The materials were characterized by X-ray diffraction, atomic absorption spectroscopy, scanning electron microscopy, transmission electron microscopy, UV–Vis diffuse reflectance spectroscopy, N2 adsorption-desorption, and X-ray photoelectronic spectrometry. The Fe2O3 incorporation into TiO2 increased surface area, decreased Eg value, and improved the degradation efficiency of CFX. The photocatalytic tests were conducted under simulated sunlight. The best results were obtained at pH 3, (1.0% wt.) Fe2O3-TiO2, and 5.3 mmol L-1 H2O2, achieving complete degradation of CFX and 73% mineralization at 150 kJ m-2 of accumulated radiation. A synergistic effect between heterogeneous photocatalysis and photo-Fenton process was observed using Fe2O3-TiO2 as the catalyst. Inorganic ions such as nitrate and sulfate, short-chain carboxylic acids (organic ions) were detected during degradation. Also, the stability of Fe2O3-TiO2 was demonstrated during five consecutive cycles in the CFX degradation with minimum iron leaching, which makes it a suitable catalyst for organic contaminants elimination by heterogeneous photo-Fenton.

Humic acid coated magnetic iron oxide nanoparticles (HA-MNPs) were synthesized, characterized, and studied for the removal of toxic inorganic arsenic species from aqueous media. The adsorption of As(III) and As(V) followed pseudo-second-order kinetics, and the observed data were accurately modeled employing the Freundlich adsorption isotherm. Application of the Weber and Morris intraparticle diffusion model to the observed kinetic data suggests that the adsorption occurs in three distinct stages, fast, intermediate, and slow steps. We propose the initial stage is governed by surface association, followed by intraparticle diffusion of arsenic through the HA matrix and, finally, chemical reaction or bonding between the arsenic species and HA functionality. The HA-MNP nanoadsorbent absorbs >95% of the inorganic arsenic species with an absorption capacity of 12.2–12.6 mg/g from aqueous media and is effective under a variety of conditions. Post arsenic adsorption characterization of the nanoparticles suggests ...

In this work, we present the synthesis of Ag doped TiO2 materials. The products are characterized by powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption, and hydrogen adsorption. The Ag/TiO2 materials exhibit 3.65 times higher in hydrogen adsorption capability compared with the non-doped TiO2 materials thank to the existence of Ti3+ species, which are Kubas-type hydrogen adsorption centers, and the Ag nanoparticles which provide spillover effects. We believe that this is the first time that both Kubas-type adsorption and spillover are exploited in the design of novel hydrogen storage materials.

The cost-effective low-frequency ultrasound (42 kHz) producing bath type sonicator was utilized to demonstrate the synthesis of sequential (SP) and co-precipitated (CP) Ce 0.9 Pr 0.1 O 1.95 , Ce 0.9 Nd 0.1 O 1.95 and their bare catalysts. The analytical characterizations of the catalysts showed that the 42 kHz ultrasound fetches the interesting physicochemical properties with unusual sonocatalytic efficiency in the resulting catalysts. In addition, the ultrasound introduced the nanoporous structure in the CeO 2 , Ce 0.9 Pr 0.1 O 1.95 (SP, CP) and Ce 0.9 Nd 0.1 O 1.95 (SP, CP) catalysts, however, the nanoporous structure was not observed for the bare praseodymium and neodymium oxides. The sonocatalytic efficiency of the catalysts was evaluated by studying the degradation kinetics of Acid Blue 113 (AB113) dye. The sonocatalytic degradation of AB113 followed the first-order kinetic rate law and the r 2 (linear regression coefficient) was >0.92. The extended ultrasound irradiation of AB113 was studied for 7 h in the presence of various nanocatalysts in order to evaluate the total organic carbon (TOC) removal from the sonocatalytic microenvironment. The rapid development of cost-effective technology based on 42 kHz ultrasound assisted degradation of various environmental pollutants significantly contributes to reducing the cost required for the commercialization of advanced oxidation processes.

Effective removal of excess phosphate from water is critical to counteract eutrophication and restore water quality. In this study, low cost, environmentally friendly humic acid coated magnetite nanoparticles (HA-MNP) were synthesized and applied for the remediation of phosphate from aqueous media. The HA-MNPs, characterized by FTIR, TEM and HAADF-STEM showed the extensive coating of humic acid on the magnetite surface. The magnetic nanoparticles with diameters of 7–12 nm could be easily separated from the reaction mixture by using a simple hand held magnet. Adsorption studies demonstrate the fast and effective separation of phosphate with maximum adsorption capacity of 28.9 mg/g at pH 6.6. The adsorption behavior follows the Freundlich isotherm suggesting the formation of non-uniform multilayers of phosphate on the heterogeneous surface of HA-MNP. The adsorption kinetic fits the pseudo-second order model well with rate constants of 0.206 ± 0.003, 0.073 ± 0.002 and 0.061 ± 0.003 g mg −1 min −1 for phosphate (P) concentrations of 2, 5 and 10 mg/L respectively. The removal of phosphate was found higher at acidic and neutral pH compared to basic conditions. The nanoparticles exhibit good selectivity and adsorption efficiency for phosphate in presence of co-existing ions such as Cl − , SO 4 2− and NO 3 − with some inhibition effect by CO 3 2− . The effect of temperature on the adsorption reveals that the process is endothermic and spontaneous. HA-MNPs are promising, simple, environmentally friendly materials for the removal of phosphate from aqueous media.

Controlling size and shape of hybrid nanostructures is technologically important because of the strong effect of nanostructure dimension and morphology on optoelectronic, biosensors and catalytic properties. Here, we have demonstrated a simple strategy for simultaneous control of morphology, defect engineering and photocatalytic activities of reduced graphene oxide:zinc oxide (rGO:ZnO) hybrid nanostructures which were prepared by using low frequency (42 kHz) ultrasound. By varying the solvents, the morphology of ZnO gradually evolved from spherical shape to a star like nature and the ZnO nanoparticles decorated on reduced graphene oxide were clearly observed in the TEM analysis. Absorption, photoluminescence, Raman and FTIR spectra clearly indicated the formation of rGO:ZnO hybrid nanostructures. Thermal analysis revealed that the hybrid nanostructures exhibited a good thermal stability. The synergistic integration of the unique morphology and size imparts the rGO:ZnO hybrid nanostructures with remarkably enhanced photocatalytic efficiency when compared with bare ZnO. The enhanced photocatalytic behaviour of the rGO:ZnO composite has been discussed in details herein. Simple and facile synthesis route demonstrated the potential for the utilization of rGO:ZnO hybrid nanostructures with unique properties for environmental engineering applications.

The development and study of new smart materials is an emergent research area with high potential applications. In this study, we have fabricated poly(ethyleneimine)/poly(acrylic acid) multilayer films on glass substrates by automated spray-layer-by-layer (spray-LbL) technique. By analyzing the changes in thickness, roughness and elasticity, with fine-tuning of the operational parameters of the spray-LbL system, evident trends of its effect on the multilayer construction were observed. In the case of its mechanical properties, the stability of Young’s modulus (up to 8.25 GPa) from film thickness at this scale was detected, making it variable for other factors such as pH and molecular weight. This work also identified the healability phenomenon that is present in the exponentially grown PEI/PAA samples, based on the reduction in viscosity of the polymer complexes and the interdiffusion of polyelectrolytes at the damaged zones in the presence of water. These properties allow for the assembly of a highly electrically conductive multilayered film by dispersion of a top layer of silver nanowires whose sheet resistance is increased around 5% after multiple damaging events. These experimental results provide new data for the evaluation and design of polyelectrolyte multilayers assembled with a spin-assisted automated spray deposition system to serve as substrates for mechanoelectrical devices which can benefit from its self-healing and modulated mechanical capabilities.

The photocatalytic activities of reduced titanium dioxide (TiO2) materials have been investigated by measuring their ability to produce hydroxyl radicals under UV and visible light irradiation. Degussa P25 TiO2 was doped with nitrogen (N), fluorine (F), and/or phosphorus (P) and then subjected to surface modification employing a thermo-physicochemical process in the presence of reducing agent sodium borohydride (NaBH4). The reduced TiO2 materials were characterized by a number of X-ray, spectroscopic and imaging methods. Surface doping of TiO2 was employed to modulate the band gap energies into the visible wavelength region for better overlap with the solar spectrum. Hydroxyl radical generation, central to TiO2 photocatalytic water purification applications, was quantitated using coumarin as a trap under UV and visible light irradiation of the reduced TiO2 materials. At 350 nm irradiation, the yield of hydroxyl radicals generated by the reduced forms of TiO2 was nearly 90% of hydroxyl radicals generated by the Degussa P25 TiO2. Hydroxyl radical generation by these reduced forms of TiO2 was also observed under visible light irradiation (419 and 450 nm). These results demonstrated that simple surface modification of doped TiO2 can lead to visible light activity, which is important for more economical solar-driven applications of TiO2 photocatalysis.

The catalyst FeTiO3/ZnO was prepared by ultrasound-assisted chemical precipitation method. The material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDAX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL). FeTiO3/ZnO (1, 5, and 10%wt. FeTiO3) was evaluated on photocatalytic degradation of ciprofloxacin (CPX) in an aqueous solution (10 mg L−1) under UV-Vis irradiation. The heterojunction between FeTiO3 and ZnO, the presence of Fe2O3 impurities, and the formation of oxygen vacancies allowed the coupled material FeTiO3/ZnO (1%wt.) showed a better photocatalytic performance (100% degradation CPX and 27% of mineralization) than bare ZnO. Although ZnO also attained complete degradation of CPX, the antibiotic was not mineralized under the same operating conditions. A scavenger study determined that h+ and OH were the principal reactive species involved in the CPX photocatalytic degradation. The heterostructured material showed high stability and reusability during three cycles of use.

In this research study, WO3/NaNbO3-coupled photocatalysts were synthesized at three WO3 mass ratios (15, 85, and 95 wt%) and characterized. These composites were characterized via X-ray powder diffraction, N2 physisorption, UV–Vis diffuse reflectance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and photoluminescence techniques. For comparison, bare WO3 and NaNbO3 were also synthesized and characterized. 2,4-Dichlorophenoxyacetic acid (2,4-D) was degraded under visible light to evaluate its photocatalytic performance. The WO3 (95 wt%)/NaNbO3 composite showed higher photocatalytic activity than pure WO3 and NaNbO3 and even than the 15 and 85 wt% coupled materials; thus, the combination with the highest ratio of WO3 with respect to NaNbO3 showed increased photocatalytic activity compared with the bare materials.

La 0.6 Sr 0.4 M 0.1 Fe 0.9 O 3-δ (M: Co, Ni and Cu) perovskite nanostructures were synthesized using low frequency ultrasound assisted synthesis technique and effect of substitution of Fe by Co, Ni and Cu on crystal structure and mechanical properties in La 0.6 Sr 0.4 FeO 3-δ perovskite was studied. The HRTEM and Rietveld refinement analyses revealed the uniform equi-axial shape of the obtained nanostructures with the existence of La 0.6 Sr 0.4 M 0.1 Fe 0.9 O 3−δ with mixed rhombohedral and orthorhombic structures. Substitution by Cu decreases the melting point of La 0.6 Sr 0.4 FeO 3-δ . The results of mechanical characterizations show that La 0.6 Sr 0.4 Co 0.1 Fe 0.9 O 3−δ and La 0.6 Sr 0.4 Ni 0.1 Fe 0.9 O 3−δ have ferroelastic behavior and comparable elastic moduli, however, substitution by Ni shows higher hardness and lower fracture toughness than Co in B-site doping.

A controlled synthesis of CuO nanostructures with various morphologies were successfully achieved by presence/absence of low frequency (42 kHz) ultrasound with two different methods. The size, shape and morphology of the CuO nanostructures were tailored by altering the ultrasound, mode of addition and solvent medium. The crystalline structure and molecular vibrational modes of the prepared nanostructures were analysed through X-ray diffraction and FTIR measurement, respectively which confirmed that the nanostructures were phase pure high-quality CuO with monoclinic crystal structure. The morphological evaluation and elemental composition analysis were done using TEM and EDS attached with SEM, respectively. Furthermore, we demonstrated that the prepared CuO nanostructures could be served as an effective photocatalyst towards the degradation of methyl orange (MO) under visible light irradiation. Among the various nanostructures, the spherical shape CuO nanostructures were found to have the better catalytic activities towards MO dye degradation. The catalytic degradation performance of MO in the presence of CuO nanostructures showed the following order: spherical

The presence of sulfates potentialize damage on cementbased materials, leading to structural failures. Therefore, structures must be designed to compensate for this effect. The mechanical properties of cement–chitin mixtures are investigated with different percentages of chitin (0.5, 1.3, and 2.1 wt.%) and aging of composite in a joint nanoscopic- and macroscopic-scale by experimental study. The objective is to increase the durability of concrete elements at coastal aquifers where concrete structures are in constant exposure to sulfate ions, chloride ions among others. Tapping mode AFM was used to characterize the surface structure and roughness of the cement pastes. To verify the chitin addition and the formation of sulfate-based aggregates Raman and IR spectra were recorded and are presented in this work. Then, force spectroscopy was used to obtain the nanomechanical properties at three different exposure times (1 day, 6 months, and 1 year) into water or a SO4 2 environment. Macroscopic parameters (e.g., compression strength of cylindrical probes) were assessed for comparison following standard guidelines. The results show a decrease of its mechanical properties as a function of the polymer concentration but more importantly, they correlate the elasticity and adhesion at the nanoscale with the behavior of the bulk material.

Despite the recent synthesis and identification of a diverse set of new nanophotocatalysts that has exploded recently, titanium dioxide (TiO2) remains among the most promising photocatalysts because it is inexpensive, non-corrosive, environmentally friendly, and stable under a wide range of conditions. TiO2 has shown excellent promise for solar cell applications and for remediation of chemical pollutants and toxins. Over the past few decades, there has been a tremendous development of nanophotocatalysts for a variety of industrial applications (i.e. for water purification and reuse, disinfection of water matrices, air purification, deodorization, sterilization of soils). This paper details traditional and new industrial routes for the preparation of nanophotocatalysts and the characterization techniques used to understand the physical chemical properties of them, like surface area, ζ potential, crystal size, and phase crystallographic, morphology, and optical transparency. Finally we present some applications of the industrial nanophotocatalysts.

Norflurazon (4-chloro-5-(methylamino)-2-[3-(trifluoromethyl)phenyl]pyridazin-3(2H)-one; C12H9ClF3N3O) is an excellent weed controlling agent being practiced in the agricultural lands. The excessive addition or the undissolved Norflurazon (maximum solubility 28 mg/L at 25 °C) enters into the aquatic environment and causes the adverse effects associated with its high concentration. To avoid the perilous effects, visible light assisted photocatalysis set-up coupled with the 42 kHz ultrasound producing bath type sonicator is used to completely mineralize the Norflurazon. TiO2, ZnO and gold loaded zinc oxide nanocatalysts were utilized to study the mineralization of Norflurazon. Au-ZnO shows the greater efficiency for the sonophotocatalytic removal of Norflurazon among the various nanocatalysts employed to study the mineralization. The order of Norflurazon mineralization was sonophotocatalysis > sonocatalysis > photocatalysis. The additive effect was achieved for the sonophotocatalytic degradation. The high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometric (LCMS) analyses were employed to identify the various intermediates produced during the mineralization. The identification of four pseudo molecular ions and various intermediates using the LCMS analysis evidently suggests the sonophotocatalytic degradation was preceded in various decay pathways. A suitable mechanism has been proposed for the sonophotocatalytic mineralization of Norflurazon.

CoFe2O4 nanoparticles with band gap of 1.5 eV have excellent magnetic properties but poor catalytic degradation of Acid Blue (AB113) under ambient conditions due to the rapid recombination of electronic charges. To prevent the rapid recombination of electronic charges and to preserve magnetic properties exhibited by CoFe2O4 nanoparticles, in this study a non-magnetic counterpart (TiO2) was engineered by low-frequency ultrasound (40 kHz) assisted processes. Properties of the materials were characterized using XRD, Raman, STEM-HAADF, VSM, and DR-UV-Vis analyses which confirms the lattice substitution of Ti4+ by Co2+ and Fe3+ in the anatase crystal structure. TEM analysis reveals the enhanced d-spacing values for anatase (1 0 1) crystal plane when the value are compared for TiO2 (0.35 nm) and CoFe2O4/TiO2 (0.38 nm) which confirms the lattice substitution of Co2+ and Fe3+ and/or CoFe2O4 nanocatalysts. The optical band gap was increased from 1.5 eV (CoFe2O4) to 2.63 eV (CoFe2O4/TiO2). The magnetic nanocomposites demonstrated enhanced sonocatalytic rate {(CoFe2O4/TiO2 = 6.026 × 10-4 s-1) and (TiO2 = 2.135 × 10-4 s-1)} and magnetic properties. Heterogeneous sonocatalytic activation of peroxomonosulphate (PMS) validated ∼ 1.6-fold enhanced rate of mineralization of AB113 in the presence of CoFe2O4/TiO2 nanocatalysts. Besides, CoFe2O4/TiO2 nanocatalysts were found to be more stable during the re-utilization up to six consecutive cycles in the sonocatalytic processes. A suitable mechanism was proposed for sonocatalytic degradation of AB 113 in the presence of CoFe2O4/TiO2 magnetic nanocomposites.

A noble-metal free and surface defect-induced mesoporous mixed valent NiO decorated TiO2 heterostructure with tuned bandgap has been successfully prepared. Its outstanding visible-light driven hydrogen evolution and its excellent H2 storage ability have been examined and confirmed. The formation of oxygen vacancies by surface defect creates the Ni3+ and Ti3+ on the interface of the heterostructure induce the efficient H2 evolution, bench-marked by 1200% enhancement in catalytic performance. The underlying chemistries include the near-unity occupancy of eg orbital (t2g6 eg1) of Ni3+ which speeds up the electron transfer and significantly promote the excellent electron-hole separation efficiency, establishes the outstanding overall charge-transfer efficiency and long-term photocatalytic activity in the visible light spectrum. Multiple Ti3+ adsorption centers in the structure attract multiple intact H2 molecules per each center via a sigma - pi bonding motif - namely the Kubas interaction - which leads to 480% higher H2 adsorption capability against the performance of the pristine mesoporous TiO2. Not only the significant results, the study also provide an air-stable synthetic method on the basis of low-cost and abundant materials, which are strongly favoured for scaling up production.

WOS: 000461536400006, 30721835, The detection of water soluble vitamins using electrochemical method is widely established in pharmaceutical quality control laboratories, and especially the recent advances in hybrid heterostrucure nanomaterials has devoted to enhance the significant analytical parameters like sensitivity, selectivity and fast response time. Herein, we report the synthesis of a hybrid heterostructure comprising SnO2 nanopartides supported mesoporous TiO2, and the obtained nanocomposite were fabricated over glassy carbon electrode (GCE) for the electrochemical oxidation of vitamin B-6 in pharmaceutical tablets. The designed SnO2-TiO2/GC modified electrode exhibits well-defined oxidation peak with lowering over-potential and larger signal response compared to the pristine counterparts, and it is mainly due to the formation of abundant active surface layer offered by SnO2 cocatalyst, and thus significantly enhances the electrochemical surface area. Differential pulse voltammetry (DPV) measurements revealed a sharp increase in the anodic peak current upon addition of increasing concentration of vitamin B-6. The analytical performance of the modified electrode displayed a wide linear range (0.1-31.4 mu M), high selectivity, and excellent sensitivity (759.73 mu A mM(-1) cm(-2)) with low detection limit (35 nM). Thus, the resultant mesoporous hybrid nanocatalyst provides an efficient electrochemical platform for determination of various potential analytes. (C) 2019 Elsevier Inc. All rights reserved., CONICYT, Government of Chile [CONICYT/FONDAP/15110019]; FONDECYT Government of Chile [11170414], The authors (S.R., F.G.) acknowledge the support of CONICYT, Government of Chile through the project CONICYT/FONDAP/15110019. The author (S.R) acknowledge FONDECYT Government of Chile (Project No.: 11170414), for the support to carry out this project.

Nickel-containing silica catalysts (Ni-SiO2) were synthetized via two methods: i) a modified direct synthesis and ii) incipient impregnation (as a control). The catalytic activity and deactivation of the products were evaluated in the dry reforming of methane (DRM). The modified direct synthesis method was found to favour the formation of Ni-phyllosilicates; these compounds led to a high Ni dispersion in the catalysts (even with 15 wt% of Ni). At short times of reaction, these catalysts showed low carbon deposition in comparison with that of the catalysts that were synthetized via the incipient impregnation method, which produced large carbon deposits. At long times on stream, the catalysts that contained Ni-phyllosilicates showed a severe sintering of the Ni particles during the DRM reaction at 700 °C. If the reactor is not operated in the kinetic regime, the activity loss is not adequately observed, even if significant sintering of Ni has already occurred in the catalyst. With the reactor operating in the kinetic regime, the deactivation curves can be fit using the deactivation model with residual activity (DMRA), and the Ni-SiO2 catalysts followed a second-order deactivation that was caused by the Ni sintering. Finally, at short times of reaction and with the reactor operating in the kinetic regime at 700 °C, an apparent activation energy of 80.3 kJ/mole was determined for the DRM reaction.

Structural characteristics of combustion synthesized, calcined and densified pure and doped nanoceria with tri-valent cations of Er, Y, Gd, Sm and Nd were analyzed by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The results showed that the as-synthesized and calcined nanopowders were mesoporous and calculated lattice parameters were close to theoretical ion-packing model. The effect of dopants on elastic modulus, microhardness and fracture toughness of sintered pure and doped ceria were investigated. It was observed that tri-valent cation dopants increased the hardness of the ceria, whereas the fracture toughness and elastic modulus were decreased.

Size and shape tuneable ZnO nanostructures were prepared by a low frequency ultrasound (42 kHz) route using various organic solvents as the reaction media. The crystalline nature, lattice parameters and microstructural parameters such as microstrain, stress and energy density of the prepared ZnO nanostructures were revealed through X-ray diffraction (XRD) analysis. The organic solvents influenced the size and morphology of the ZnO nanostructures, and interesting morphological changes involving a spherical to triangular shaped transition were observed. The visible emission properties and lattice vibrational characteristics of the nanostructures were drastically modified by the changes in size and shape. Raman spectral measurements revealed the presence of multiphonon processes in the ZnO nanostructures. The intensity of the visible emission band was found to vary with the size and morphology of the structures. The strongest visible emission band corresponded to the structure with the largest surface/volume ratio and could be attributed to surface oxygen vacancies. The control over the size and morphology of ZnO nanostructures has been presented as a means of determining the intensity of the visible emission band.

In this report, photocatalytic degradation of Acid Blue 113 (AB 113) has been investigated in aqueous heterogeneous media containing pure and Sm3+ doped ZnO nanostructures. A simple low frequency (42 kHz) ultrasound was employed to synthesize the nanostructures. X-ray diffraction, UV–Vis-NIR and Photoluminescence analyses revealed that Sm3+ ion was successfully doped into ZnO lattice. The organic solvents and dopant highly influenced the particle morphology which was identified through transmission electron microscopy. The photocatalytic efficiency was highly depended on the native defects and dopant. Sm3+ doped ZnO nanostructures demonstrated better photocatalytic degradation of the AB 113 due to the involvement of more oxygen vacancy defects, oxygen interstitials and Sm3+ ions in the charge recombination process and enhanced the better catalytic reaction under a UV-A lamp.

Cerium oxide (CeO2), Ce0.9Gd0.1O1.95 and Ce0.9Sm0.1O1.95 nanostructures were synthesized using 42 kHz ultrasound assisted sequential and co-precipitation techniques. The nanoporous nature of the powders was revealed from the BET analysis which showed that the observed pore size distributions and the H2 hysteresis loops of the respective nanostructures confirmed the existence of nanopores in various sizes and shapes. The nanoporous nature of the synthesized powders were further confirmed by the high resolution transmission electron microscopy (HRTEM) and high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) analyses. The perceived shift in the characteristic F2g Raman active band centered at 464 cm−1 indicated the defects were increased during the sequential co-precipitation synthesis of Ce0.9Gd0.1O1.95 and Ce0.9Sm0.1O1.95 nanostructures. Moreover, the intensity of the F2g peaks can be ordered as CeO2 < Ce0.9Sm0.1O1.95 (CP)1 < Ce0.9Gd0.1O1.95 (SP)2 < Ce0.9Sm0.1O1.95 (SP)2 < Ce0.9Gd0.1O1.95 (CP)1 which indicates the increase in the concentration of the defects like oxygen vacancies enhances the efficiency of the solid oxide fuel cells (SOFCs) as electrolyte materials. The diffuse reflectance UV-vis solid state spectroscopic analysis demonstrated the narrowing optical band gap of CeO2 during the sequential and co-precipitation of the Ce0.9Gd0.1O1.95 and Ce0.9Sm0.1O1.95 nanostructures.

The nano-size gold loaded visible light driven Au–TiO 2 nanophotocatalysts were synthesized using a commercial sonicator bath producing 42 kHz ultrasound. The X-ray diffraction (XRD), transmission electron microscopy (TEM) and high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) analyses revealed the gold nanoparticles incorporated in the TiO 2 resides at the surface of the nanocatalysts. An increased BET surface area was observed for the Au–TiO 2 when compared with the bare TiO 2 which gave the first notation that the gold nanoparticles modified the physicochemical characteristics of the TiO 2 . The RAMAN spectrum shows the shift by ∼5 cm −1 at 639 cm −1 which indicated that the loaded gold nanoparticles were loaded on the surface of TiO 2 nanoparticles and thus confirms that the gold nanoparticles readily accepts the electronic charges created during the photoexcitation of Au–TiO 2 nanocatalysts. The Simazine (triazine based pesticide) was taken as the model pollutant to evaluate its sonocatalytic, photocatalytic and sonophotocatalytic degradation in the presence of TiO 2 and Au–TiO 2 nanocatalysts. The first order kinetics was observed for the Simazine degradation. The observed rate constants indicate that the order of degradation of Simazine was, sonophotocatalysis > sonocatalysis > photocatalysis. The additive effect was observed for the Au–TiO 2 assisted sonophotocatalytic degradation of Simazine. A 1.65 and 1.38 fold enhanced mineralization was achieved for the sonophotocatalytic degradation of Simazine when compared with the photocatalytic and sonocatalytic processes. The intermediates produced during the mineralization of Simazine were analyzed using ESI-MS analysis and based on that a suitable mechanism has been proposed.

Based on our previous work on the green preparation of Ag–TiO2 photocatalyst with bactericidal activity under visible light, we extended our studies to the synthesis of TiO2–Fe3+ materials with enhanced photocatalytic activity for the degradation of recalcitrant organic pollutants in water. TiO2–Fe3+ nanopowders were synthesized using a robust, environmentally friendly procedure. Established amounts of Fe(NO3)3·9H2O and titanium tetraisopropoxide (TTIP) were mixed using glacial acetic acid as solvent. Hydrolysis of TTIP–Fe3+ was accomplished using a 30 % (W/V) Arabic gum aqueous solution. TiO2–Fe3+ nanopowders were obtained by thermal treatment at 400 °C. In order to elucidate the structure of these photocatalysts, microscopic and spectroscopic characterization techniques were applied. The high resolution transmission electron microscopy (HRTEM) analysis indicated the presence of uniformly distributed particles with average particle size of about 9 nm. According to the HRTEM lattice fringes, ring pattern, and selected area electron diffraction pattern, the crystalline part of the samples consists of anatase (PDF 01-086-1157 with the lattice constant of 3.7852, 9.5139 A and 90°) as dominant phase. X-ray photoelectron spectroscopy (XPS) was applied to determine the oxidation state of iron. The XPS provides evidence for Fe3+ surface species in the TiO2–Fe3+ composite. Complete degradation of aqueous solutions (20 ppm) of methylene blue and/or methyl orange was accomplished after 4 h of treatment using 150 mg of TiO2–Fe3+/150 mL of dye solution. The in vitro toxicity of the materials was tested. The materials showed no toxicity against human red blood cells.

In this study, TiO 2 modified with WO 3 (2 wt.%) was prepared by the sol–gel method, and its photocatalytic activity (PCA) under solar irradiation was evaluated using malathion as the model contaminant. The catalyst was synthesized using tetra butyl orthotitanate (TBT) and ammonium p -tungstate (A p T) as precursors. For comparison, bare TiO 2 was also prepared by the sol–gel process. The resulting photocatalysts were characterized by XRD, BET, DRUV–vis, FE-SEM, TEM and STEM. The synthesized TiO 2 materials exhibited a crystalline anatase phase with an average particle size of 20 nm. Results of malathion degradation using solar light, indicated that 2%WO 3 /TiO 2 showed better catalytic performance than sol–gel TiO 2 , achieving a complete degradation after 2 h, while TOC abatement was 63% after 5 h. These results suggest that 2%WO 3 /TiO 2 catalyst is a promising material for solar photocatalytic treatment of water contaminated by pesticides.

This report presents the preparation and spectroscopic properties of rGO:ZnO composite nanostructures. The reduced graphene oxide (rGO) and rGO:ZnO composite structures were prepared through modified Hummer’s and solution precipitation techniques, respectively. The decoration of star like ZnO nanostructures on rGO surface was identified through transmission electron microscopy (TEM) analysis. Raman spectral measurements revealed the co-existence of vibrational modes of ZnO and rGO which confirmed the formation of composites nanostructures. The absorption spectra of ZnO hybrid and rGO nanostructures exhibited bands at 370 and 261 nm which were attributed to the free excitonic absorption of ZnO and rGO absorption band, respectively.

Formation of NiCr nanorings out of 2-3 nm NiCr nanoparticles prepared by DC magnetron sputtering with inert gas condensation is reported. An RF quadrupole mass filter has been used to get the particle size distribution and control the particle size in the plasma stream of grown material. The depositions are made on silicon substrates at room temperature under a helium and argon atmosphere of varying composition. By optimizing the He-Ar composition, magnetron power and the condensation zone, the particle size distribution is narrowed. Magnetic characterization determines that every single nanoparticle possesses a single magnetic domain that influenced their arrangement on the substrate. These arrangements were particularly in ring like structures. Particles join together while being deposited to form rings with a ~100 nm diameter. Particle density and agglomeration phenomena depend on the substrate’s time of exposure to the NiCr nanoparticle source coming from the target.

Silver tetrahedral nanoparticles (NP) were synthesized using the inert gas condensation technique. We performed morphological and optical characterization of the nanoparticles (NPs) using atomic force microscopy (AFM), mass spectroscopy (MS), and UV-visible spectroscopy. The Ag NPs were produced by modified magnetron sputtering, followed by thermalization and condensation in a high pressure zone. Along the synthesis process, the size of the NPs was controlled through the handling of the gas flow (Ar and He), the magnetron power, and the length of the aggregation zone. We optimized the synthesis parameters to obtain a peak on the size distribution of Ag NPs around of 5 nm (as measured with AFM and MS). The AFM measurements show that the particles have tetrahedral shape, with a fair correspondence with a 2925-atoms ideal tetrahedron. We performed a set of Molecular Dynamics (MD) calculations using the Embedded Atom potential model to simulate the dynamics of particles with different shapes, obtaining that, at sizes close to that of the particles produced experimentally, the tetrahedra may be as energetically stable as cuboctahedra of roughly the same size, and that their melting point is below but close to that of the bulk. We also found that both the size and shape of the nanoparticles determine the shift of the UV-visible absorption spectrum. Finally, we observed the formation of atomic islands above the faces of the Ag tetrahedral NPs, in agreement with the results obtained from the MD simulations.

An attempt has been made to render the visible light driven photocatalytic activity to the TiO2 nanocatalysts by loading 1 wt% of rare earth (RE) nanoclusters (Gd(3+), Nd(3+) and Y(3+)) using a low frequency (42 kHz) producing commercial sonicator. The STEM-HAADF analysis confirms that the RE nanoclusters were residing at the surface of the TiO2. Transmission electron microscopic (TEM) and X-ray diffraction (XRD) analyses confirm that the loading of RE nanoclusters cannot make any significant changes in the crystal structure of TiO2. However, the optical properties of the resulted nanocatalysts were significantly modified and the nanocatalysts were employed to study the sonocatalytic, photocatalytic and sonophotocatalytic decolorization as well as mineralization of Acid Blue 113 (AB113). Among the experimented nanocatalysts maximum degradation of AB113 was achieved in the presence Y(3+)-TiO2 nanocatalysts. The decolorization of AB113 in the presence and absence of Y(3+) loaded TiO2 ensues the following order sonolysis

In this study, the solar photocatalytic activity (SPA) of WO3/TiO2 photocatalysts synthesized by the sol–gel method with two different percentages of WO3 (2 and 5%wt) was evaluated using malathion as a model contaminant. For comparative purpose bare TiO2 was also prepared by sol–gel process. The powders were characterized by X-ray diffraction (XRD), Raman spectroscopy, diffuse reflectance UV–vis spectroscopy (DRUV–vis), specific surface area by the BET method (SSABET), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy with a high annular angle dark field detector (STEM-HAADF). The XRD, Raman, HRTEM and STEM-HAADF analyses indicated that WO3 was present as a monoclinic crystalline phase with nanometric cluster sizes (1.1 ± 0.1 nm for 2% WO3/TiO2 and 1.35 ± 0.3 nm for 5% WO3/TiO2) and uniformly dispersed on the surface of TiO2. The particle size of the materials was 19.4 ± 3.3 nm and 25.6 ± 3 nm for 2% and 5% WO3/TiO2, respectively. The SPA was evaluated on the degradation of commercial malathion pesticide using natural solar light. The 2% WO3/TiO2 photocatalyst exhibited the best photocatalytic activity achieving 76% of total organic carbon (TOC) abatement after 300 min compared to the 5% WO3/TiO2 and bare TiO2 photocatalysts, which achieved 28 and 47% mineralization, respectively. Finally, experiments were performed to assess 2% WO3/TiO2 catalyst activity on repeated uses; after several successive cycles its photocatalytic activity was retained showing long-term stability.

Nanometer size-selected Cu clusters in the size range of 1–5 nm have been produced by a plasma-gas-condensation-type cluster deposition apparatus, which combines a grow-discharge sputtering with an inert gas condensation technique. With this method, by controlling the experimental conditions, it was possible to produce nanoparticles with a strict control in size. The structure and size of Cu nanoparticles were determined by mass spectroscopy and confirmed by atomic force microscopy (AFM) and scanning electron transmission microscopy (STEM) measurements. In order to preserve the structural and morphological properties, the energy of cluster impact was controlled; the energy of acceleration of the nanoparticles was in near values at 0.1 ev/atom for being in soft landing regime. From SEM measurements developed in STEM-HAADF mode, we found that nanoparticles are near sized to those values fixed experimentally also confirmed by AFM observations. The results are relevant, since it demonstrates that proper optimization of operation conditions can lead to desired cluster sizes as well as desired cluster size distributions. It was also demonstrated the efficiency of the method to obtain size-selected Cu clusters films, as a random stacking of nanometer-size crystallites assembly. The deposition of size-selected metal clusters represents a novel method of preparing Cu nanostructures, with high potential in optical and catalytic applications.

Silver nanoparticles were synthesized using the inert gas aggregation technique. We found the optimal experimental conditions to synthesize nanoparticles at different sizes: 1.3 ± 0.2, 1.7 ± 0.3, 2.5 ± 0.4, 3.7 ± 0.4, 4.5 ± 0.9, and 5.5 ± 0.3 nm. We were able to investigate the dependence of the size of the nanoparticles on the synthesis parameters. Our data suggest that the aggregation of clusters (dimers, trimer, etc.) into the active zone of the nanocluster source is the predominant physical mechanism for the formation of the nanoparticles. Our experiments were carried out in conditions that kept the density of nanoparticles low, and the formation of larges nanoparticles by coalescence processes was avoided. In order to preserve the structural and morphological properties, the impact energy of the clusters landing into the substrate was controlled, such that the acceleration energy of the nanoparticles was around 0.1 eV/atom, assuring a soft landing deposition. High-resolution transmission electron microscopy images showed that the nanoparticles were icosahedral in shape, preferentially oriented with a five-fold axis perpendicular to the substrate surface. Our results show that the synthesis by inert gas aggregation technique is a very promising alternative to produce metal nanoparticles when the control of both size and shape are critical for the development of practical applications.