Solar Photocatalytic and Self-Cleaning Performances of HoVO4 Doped ZnO.

In this article we report preparation of 5 wt% HoVO4 doped ZnO via template-free hydrothermal process and investigated its photocatalytic activity against azo dyes Rhodamine-B (Rh-B), Trypan Blue (TB) and Acid Black 1 (AB 1) in solar light irradiation. The as prepared HoVO4 doped ZnO was characterised by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Field emission Transmission electron microscopy (FE-TEM), Brunauer-Emmett-Teller (BET) surface area measurements, X-ray photoelectron spectroscopy (XPS), Diffused reflectance (DRS) and Photoluminescence (PL) spectroscopy. The SEM images clearly indicate the formation of nanoparticles in the range of 20-50 nm. BET surface area of the HoVO4-ZnO is 2 times that of ZnO. Higher activity of HoVO4-ZnO in natural sunlight may be due to higher visible light absorption of HoVO4- ZnO when compared to undoped ZnO. The results suggested that HoVO4 doping on ZnO has great influence on the photocatalytic activity. The prepared photocatalyst HoVO4-ZnO possesses high stability and reusability without appreciable loss of catalytic activity up to four runs. Significant hydrophobicity of HoVO4-ZnO reveals its self cleaning property.

Photophysical and Photoprototropic Characteristics of 2-Aminobenzothiazole in ß-Cyclodextrin Medium.

The formation of stable inclusion complexes between neutral and monocationic species of 2-aminobenzothiazole (2ABT) with ß-CDx is observed with significant enhancement in absorbance and fluorescence intensity. The stoichiometry of the 2ABT and 2ABTH⊕ with ß-CDx is found to be 1:1 at pH 6.8 and 1.1. Their binding constant values for neutral and monocationic species are found to be 1239.3 and 1259.2 M-1, respectively. Lifetime analysis, FT-IR spectral and SEM image analysis strongly supports the formation of the inclusion complex between 2ABT and ß-CDx. Photoprototropic study shows that there is no remarkable difference in the pK a and pK a* in aqueous and ß-CDx media, which is rules out the formation of the inclusion complex with -NH2 group of 2ABT inside the cavity of ß-CDx i.e., the -NH2 group of 2ABT is in aqueous environment. Based on stoichiometry, binding constant and acidity constant values, the structure of the 1:1 complex is proposed.

TiO2-PANI/Cork composite: A new floating photocatalyst for the treatment of organic pollutants under sunlight irradiation.

A novel photocatalyst based on TiO2-PANI composite supported on small pieces of cork has been reported. It was prepared by simple impregnation method of the polyaniline (PANI)-modified TiO2 on cork. The TiO2-PANI/Cork catalyst shows the unique feature of floating on the water surface. The as-synthesized catalyst was characterized by X-ray diffraction (XRD), scanning electron micrograph (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectra (UV-vis DRS) and the Brunauer-Emmett-Teller (BET) surface area analysis. Characterization suggested the formation of anatase highly dispersed on the cork surface. The prepared floating photocatalyst showed high efficiency for the degradation of methyl orange dye and other organic pollutants under solar irradiation and constrained conditions, i.e., no-stirring and no-oxygenation. The TiO2-PANI/Cork floating photocatalyst can be reused for at least four consecutive times without significant decrease of the degradation efficiency.

Construction of single tungsten/copper atom oxide supported on the surface of TiO2 for the higher activity of electrocatalytic water splitting and photodegradation of organic pollutant.

Intense studies are being carried out on single atom catalysts that exhibit remarkable activity and selectivity. To enhance their catalytic abilities, one must have a thorough understanding of the properties of the single metal atom active site and its dynamics in the working state. Herein, we report single metal atom oxide (SMAO) (metal: W/Cu) anchored on TiO2-rGO nanomaterials (SMAO-ED-TiO2-rGO) by simple sonication process. It is efficient for the electrocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and photocatalytic degradation of pharmaceutical pollutant. The uniform dispersion of the tungsten/copper metal atom oxide over a TiO2-rGO materials is detected by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The SMAO-ED-TiO2-rGO nanocatalyst has shown impressive HER/OER activity with an overpotential of 121/295 mV at (-)10 mA cm-2 current density and the low Tafel slope of 96/60.3 mV dec-1 in 1 M KOH solution. Further, SMAO-ED-TiO2-rGO nanocatalyst was used for the photocatalytic degradation of ciprofloxacin (CF). After 60 min of UV light irradiation, the SMAO-ED-TiO2-rGO nanocatalyst efficiently photodegraded 98.5% of CF while retaining its activity for five cycles. Superoxide radicals (O2•-) are found to be the main reactive species required in the photodegradation of CF, according to scavenger study of the SMAO-ED-TiO2-rGO nanocatalyst for CF degradation.

Sonication strategy for anchoring single metal atom oxides (W, Cu, Co) on CeO2-rGO for boosting electrocatalytic oxygen evolution reaction.

In the field of electrocatalysis, single-atomic-layer tungsten, copper, and cobalt oxide on CeO2, ethylene diamine (ED) and reduced graphene oxide (rGO) supported materials shows tremendous potential. Despite the enormous interest in single metal atom oxide (SMAO) catalysts, it is still very difficult to directly convert readily available bulk metal oxide into single atom oxide. It is crucial and tough to create high performance materials for the oxygen evolution reaction (OER) in an alkaline environment. Herein, a single tungsten, copper and cobalt atom oxide (SMAO) anchored on the CeO2 atomic layer and overall components deposited on the rGO (rGO-ED-CeO2-WCuCo) is prepared through a one-pot sonication technique. The presence of SMAO is identified by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging. The electrocatalytic performance of final rGO-ED-CeO2-WCuCo-30 nanocomposite for the OER in 1 M KOH electrolyte is evidenced by providing low overpotential of 283 mV at 10 mA cm-2. The Tafel slope for OER using rGO-ED-CeO2-WCuCo-30 electrocatalysts is 57.03 mV dec-1. The electrocatalytic activity of rGO-ED-CeO2-WCuCo-30 nanocomposites for OER was noticeably increased when compared to bare CeO2 nanorods (401 mV), rGO-ED-CeO2-WCo-30 (345 mV), rGO-ED-CeO2-WCu-30 (340 mV) and rGO-ED-CeO2-WCuCo-20 (321 mV) samples.

Solar active fire clay based hetero-Fenton catalyst over a wide pH range for degradation of Acid Violet 7.

Fe(III) immobilized fire clay (Fe-FC) was prepared using ferric nitrate by solid state dispersion method and this hetero-Fenton catalyst was applied for the degradation of Acid Violet 7 (AV 7) under natural sunlight. The 26% ferric nitrate loaded fire clay was found to be most efficient. The experimental conditions such as solution pH, H2O2 concentration for efficient degradation of AV 7 have been determined. Unlike Fenton catalyst, Fe-FC is photoactive over a wide pH range of 3-7. This catalyst was found to be stable and reusable. The GC-MS analysis of experimental solutions during irradiation revealed the formation of 2,8-diaminonaphthalene-1,3,6-triol, 8-aminonaphthalene-1,2,3,6-tetrol, 2-aminonaphthalene-1,3,6,8-tetrol and 2-aminobenzene-1,3-diol/5-aminonbenzene-1,3-diol/ 2-aminobenzene-1,4-diol as intermediates. The 26% ferric nitrate loaded fire clay was characterized by XRD, ICP-AES, BET surface area, FT-IR, SEM-EDS and UV-DRS studies.

Eco-friendly hybrid Paper-AgBr-TiO2 for efficient photocatalytic aerobic mineralization of ethanol.

In this study, a facile and effective route to prepare hybrid photocatalysts (paper-TiO2, paper-TiO2-AgBr and paper-AgBr-TiO2) has been reported. The preparation procedure consisted of the direct adsorption of the previously synthesized titania nanoparticles (TiO2 sol) to generate the TiO2 nanosphere and the immersion process in an aqueous suspension of AgBr to form the AgBr nanoclusters on paper fibers. The synthesis technology is economic, efficient, environmentally friendly and easy to implement even at industrial scale. A cellulose-based structure with well dispersed TiO2 particles of around 1 µm and a pseudo-liquid coating of Ag+ and AgBr species was obtained. All the prepared photocatalysts demonstrated effective photocatalytic performance in gaseous phase ethanol degradation with simulated sunlight illumination, through the direct mineralization to CO2 and the parallel reaction via acetaldehyde degradation. A relevant improvement in the photocatalytic activity was noticed when TiO2 was associated with AgBr nanocrystals, with a higher effect observed when AgBr was loaded onto the paper surface prior to TiO2. Ag-Ti interaction reduces the pair recombination rate and increases the available charge carriers generating reactive OH- radicals from both Ag-species and TiO2, and O2- radicals from Ag+-AgBr species, which would be involved in the ethanol degradation process.

Correction: Nano N-TiO2 mediated selective photocatalytic synthesis of quinaldines from nitrobenzenes.

[This corrects the article DOI: 10.1039/C2RA01178F.].

Solar light-driven CeVO4/ZnO nanoheterojunction for the mineralization of Reactive Orange 4.

In this study, we synthesized CeVO4/ZnO nanoheterojunction photocatalyst through hydrothermal-precipitation method. The prepared photocatalyst was characterized by Fourier transform infrared analysis (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) with elemental color mapping (ECM), high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED) pattern, UV-vis diffuse reflection spectroscopy (UV-vis-DRS), BET, and photoluminescence (PL) spectroscopy. The BET surface area of CeVO4/ZnO is 10.50 m2/g. The photocatalytic activity of CeVO4/ZnO nanoheterojunction under solar light was investigated for the degradation of Reactive Orange 4 (RO 4). CeVO4/ZnO has been found to be more effective for mineralization of RO 4 than the prepared ZnO at neutral pH. The addition of TBA (•OH scavenger) contributes a significant decrease in the photodegradation efficiently of the catalyst. Chemical oxygen demand (COD) measurements confirmed the complete mineralization of RO 4. In addition, it found that the photocatalyst was stable and reusable. Graphical abstract.

Efficient Photoreduction of Hexavalent Chromium Using the Reduced Graphene Oxide-Sm2MoO6-TiO2 Catalyst under Visible Light Illumination.

In past years, the presence of toxic heavy metal ions in water and soil has caused major health problems. The ternary type semiconductor material, reduced graphene oxide (rGO)-Sm2MoO6-TiO2, has been investigated as a photocatalyst for the reduction of soluble chromium(VI) into (III) for the first time. The as-synthesized rGO-Sm2MoO6-TiO2 catalyst was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, X-ray photoelectron spectroscopy, FT-Raman, Fourier transform infrared, and optical spectroscopy. The maximum Cr(VI) reduction of 96% was achieved within 70 min under visible light illumination. The powder XRD analysis confirmed the formation of anatase TiO2. Field-emission SEM images depicted well-dispersed rGO sheets, and TiO2 and Sm2MoO6 particles are randomly distributed onto rGO. The reduction of Cr(VI) by rGO-Sm2MoO6-TiO2 was considerably greater than the reduction by Sm2MoO6, TiO2, Sm2MoO6-rGO, TiO2-rGO, and Sm2MoO6-TiO2. Sm2MoO6 acts as an effective cocatalyst to TiO2 to enhance the separation of photo-generated electron-holes. Even after six consecutive cycles, the photoreduction of Cr(VI) was more than 85%, which reveals that the excellent reusability performance of the catalyst for practical applications. The photogenerated electron plays an important role in the reduction of Cr(VI) into nontoxic Cr(III), and the synergistic effect of rGO greatly improved the separation of h+ and e- pairs.

Sol-Gel Synthesis of Ce4-x Sr1+x Fe5-x Zn x O14+δ [0 ≤ x ≤ 0.45] Superparamagnetic Oxide Systems and Its Magnetic, Dielectric, and Drug Delivery Properties.

In this work, we have successfully synthesized superparamagnetic nanocomposites, Ce4-x Sr1+x Fe5-x Zn x O14+δ (0 ≤ x ≤ 0.45) (CSFZ) (TA1-TA4: x = 0, 0.15, 0.30, and 0.45) via the Nitrate-citrate sol-gel method. X-ray diffraction studies show the formation of single-phase nanocomposites (NCs) and the average crystallite size is found to be 18 nm. Energy-dispersive X-ray spectroscopy analysis supports the formation of the desired product with the expected composition. The scanning electron microscopy image shows that the prepared samples are in spherical shape and highly porous in nature. Most of the particle sizes present in the image are in the range of 5-20 nm. The optical studies show an intense peak at 583 nm corresponding to the instantaneous existence of both Fe2+ and Fe3+ intervalence electronic charge transition bands. X-ray photoelectron spectra analysis confirms the presence of elements with their preferred oxidation state. The superparamagnetic nature of the prepared sample was confirmed by vibrating sample magnetometer analysis. Synthesized materials show a low saturate magnetic moment ranging from 0.3400 to 0.1075 emu/g. The coercivity and retentivity value of the synthesized NC is zero. The NCs show high encapsulation efficiency toward ciprofloxacin hydrochloride because of their unique structure and release the loaded drug molecules in a sustained manner up to 10 h at pH 7.4. Such NCs have high potential for use as multifunctional material in various fields such as optical properties, conductivity studies, dielectric, sensor, and drug delivery properties.

Changes in the fatty-acid profile of cyanide-utilizing Yersinia species.

A cyanide-utilizing Yersinia species was isolated from the cyanide-bearing gold-plating industrial wastewater. Analysis of the fatty acid composition of the organism revealed that it contains large amounts of saturated fatty acids. The unsaturated hydroxy- and cyclopropyl-ring-bearing fatty acids are present in low concentrations. A comparison of the fatty acid composition with other Yersinia species shows that the genus Yersinia appears homogeneous, and that fatty-acid data of Yersiniae do not reflect the distance between Yersiniae species.

Preparation and characterization of host-guest system between inosine and ß-cyclodextrin through inclusion mode.

Inosine is a nucleoside that is formed when hypoxanthine is attached to a ribose ring (also known as a ribofuranose) via a ß-N9-glycosidic bond. Inosine is commonly found in tRNAs. Inosine (INS) has been used widely as an antiviral drug. The inclusion complex of INS with ß-CDx in solution phase is studied by ground and excited state with UV-visible and fluorescence spectroscopy, respectively. A binding constant and stoichiometric ratio between INS and ß-CDx are calculated by BH equation. The lifetime and relative amplitude of INS is increases with increasing the concentrations of ß-CDx, confirms the formation of inclusion complex in liquid state. The solid complexes are prepared by kneading method (KM) and co-precipitation method (CP). The solid complex is characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and differential scanning colorimetry (DSC). CP method gives the solid product with good yield than that of physical mixture and KM method. The structure of complex is proposed based on the study of Patch - Dock server.

The simple, template free synthesis of a Bi2S3-ZnO heterostructure and its superior photocatalytic activity under UV-A light.

The development of a heterostructured semiconductor photocatalyst makes a significant advancement in catalytic technologies. Highly crystalline Bi2S3-ZnO nanosheets with a hierarchical structure have been successfully synthesized by a facile sonochemical process and characterized by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL) and Brunauer-Emmett-Teller (BET) surface area measurements. X-ray powder diffraction (XRD) analysis reveals that the as synthesized product has an orthorhombic phase of Bi2S3 and a hexagonal wurtzite phase of ZnO. XPS analysis shows the presence of the elements Zn, O, Bi and S and their oxidation states. Bi2S3-ZnO has increased absorption in the UV region as well as in the visible region. This heterostructured nano catalyst has a higher photocatalytic activity for the degradation of Acid Black 1 (AB 1) under UV-A light than pure ZnO, Bi2S3 and commercial Degussa P25. The heterojunction in the Bi2S3-ZnO photocatalyst has led to low recombination rates of photoinduced electron-hole pairs and an enhanced photocatalytic activity. Bi2S3-ZnO is advantageous in AB 1 degradation because of its reusability and higher efficiency at neutral pH 7.

The simple hydrothermal synthesis of Ag-ZnO-SnO2 nanochain and its multiple applications.

In this article, we report the fabrication of a stable Ag-ZnO-SnO2 nanochain by template free hydrothermal method and its photocatalytic activity for the first time. This composite material represents a potential new class of photocatalysts with enhanced light absorption, hydrophobic and electronic properties of ZnO. This catalyst has been characterized by X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), field emission scanning electron microscopy (FESEM), elemental mapping, energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). XRD and elemental mapping reveal the presence of SnO2 and Ag in the catalyst. Ag-ZnO-SnO2 has increased absorption in the visible region when compared to ZnO. This three component nano junction system exhibits enhanced photocatalytic activity for the degradation of azo dyes, Acid Black 1 (AB 1) and Acid Violet 7 (AV 7) under UV light (365 nm), far exceeding those of the single and two component systems. Ag-ZnO-SnO2 is found to be reusable without appreciable loss of catalytic activity up to four runs. Based on the band gap energies of ZnO and SnO2, a mechanism is proposed for the photodegradation of dyes. Hydrophobicity and photoconductivity of Ag-ZnO-SnO2 have been evaluated. Nanochain exhibiting higher positive photoconductivity can be useful for soliton wave communication as well as solar cell applications. Our results provide some new insights on the fabrication of Ag-ZnO-SnO2 and its performance as an active photocatalyst, self cleaning and conducting material.

Effect of inclusion complexation on the photophysical behavior of diphenylamine in ß-cyclodextrin medium: a study by electronic spectra.

Spectral characteristics of diphenylamine (DPA) have been investigated in ß-cyclodextrin (ß-CDx) solution. The formation of the complex was revealed by UV, steady state and time-resolved fluorescence spectroscopy. The stoichiometry of DPA:ß-CDx complex, determined using Benesi-Hildebrand equation and Job's continuous variation method is 1:1. The binding constants calculated from various methods are reported. This inclusion complex formation from DPA and ß-CDx was also confirmed by the FT-IR spectral study and SEM image analysis of solid complex prepared by co-precipitation method.

Nanostructured AgBr loaded TiO2: An efficient sunlight active photocatalyst for degradation of Reactive Red 120.

The AgBr loaded TiO2 catalyst was prepared by a feasible approach with AgBr and tetraisopropyl orthotitanate and characterized by BET surface area measurement, diffuse reflectance spectra (DRS), scanning electron microscope (SEM), energy dispersive spectra (EDS), X-ray diffraction (XRD), transmission electron microscope (TEM) and atomic force microscope (AFM) analysis. The results of characterization reveal that AgBr loaded TiO2 has a nanostructure. Formation of the nanostructure in AgBr loaded TiO2 results in substantial shifting of the absorption edge of TiO2 to red and enhancement of visible light absorption. Electrochemical impedance spectroscopy measurements reveal that AgBr loaded TiO2 has a higher photoconductivity than prepared TiO2 due to higher separation efficiency of electron-hole pairs. Cyclic voltammetric studies reveal enhanced conductivity in AgBr loaded TiO2, which causes an increase in its photocatalytic activity. AgBr loaded TiO2 exhibited a higher photocatalytic activity than TiO2-P25 and prepared TiO2 in the photodegradation of Reactive Red 120 (RR 120).

Fluorimetric and prototropic studies on the inclusion complexation of 3,3'-diaminodiphenylsulphone with beta-cyclodextrin and its unusual behavior.

The photophysical and photoprototropic properties of 3,3'-diaminodiphenylsulphone (3DADPS) in aqueous beta-cyclodextrin (beta-CDx) solution have been investigated using absorption and fluorescence spectral techniques. beta-CDx forms 1:1 inclusion complex with 3DADPS as revealed by steady state and time-resolved fluorescence spectroscopy. This inclusion complex formation was also confirmed by the FT-IR and SEM image analysis of solid complex prepared by co-precipitation method. The existence of twisted intramolecular charge transfer state and the unusual red shift observed during inclusion complexation were analyzed and discussed. The ground and excited state acidity constants in beta-CDx are reported. Based on the photophysical and photoprototropic characteristics of 3DADPS in beta-CDx, the structure of the 1:1 inclusion complex is proposed.