Enhanced photocatalytic performance of ZnO under visible light by co-doping of Ta and C using hydrothermal method.

This study attempted to improve the photocatalytic activity of zinc oxide (ZnO) semiconductors in the visible light region by introducing the co-doping of carbon (C) and tantalum (Ta) to ZnO (ZTC) using a simple hydrothermal method with the respective precursors. The obtained uniform ZTC nanoparticles with an average crystal size of 29.30 nm (according to Scherrer's equation) revealed a redshift with a decrease in bandgap (Eg) from 3.04 eV to 2.88 eV, allowing the obtained photocatalyst to absorb the energy of the visible light for photocatalysis. Furthermore, the Zn 2p and Ta 4f core level spectra confirmed the presence of Zn2+ and Ta5+ in the ZTC sample. In addition, the infrared spectra identified hydrogen-related defects (HRDs), while the O 1s spectra indicated the existence of oxygen vacancies (VO). Electrochemical tests revealed improvement in the electron conductivity and charge separation of the obtained materials. To follow, the photocatalytic performance assessment was conducted by varying the C/Zn2+ ratios (5, 10, and 15 mol%) in ZTC samples, the initial RhB concentration (7, 15, and 30 ppm), and the pH of the RhB solution (3.0-10.0). The photodegradation on ZTC samples showed the most effectiveness for a 7 ppm RhB solution with a C/Zn2+ ratio of 10 mol% in the slightly alkaline medium (pH 9.0). Additionally, ZTC also exhibited commendable durability after being reused several times. The nature of RhB photodegradation was proposed and discussed via a mechanism at the end of this work.

One-step hydrothermal preparation of Ta-doped ZnO nanorods for improving decolorization efficiency under visible light.

In this work, Ta-doped ZnO (Ta-ZnO) nanomaterials were synthesized by the hydrothermal method at different temperatures (110, 150, and 170 °C) for the photodegradation of methylene blue (MB) under visible light. Ta doping significantly affects the crystal defects, optical properties, and MB photocatalytic efficiency of ZnO materials. The optical absorption edge of Ta-ZnO 150 was redshifted compared to undoped ZnO, correlating to bandgap narrowing (E gTa-ZnO = 2.92 eV; E gZnO = 3.07 eV), implying that Ta doped ZnO is capable of absorbing visible light. Besides, Ta-doping was the reason for enhanced blue light emission in the photoluminescence spectrum, which is related to the oxygen defect V 0 O. It is also observed in the XPS spectra, where the percentage of oxygen in the oxygen-deficient regions (O531.5 eV) of Ta-ZnO150 is higher than that of ZnO150. It is an important factor in enhancing ZnO's photocatalytic efficiency. The MB degradation efficiency of Ta-doped ZnO reached the highest for Ta-ZnO 150 and was 2.5 times higher than ZnO under a halogen lamp (HL). Notably, the influence of hydrothermal temperature on the structural, morphological, and photoelectrochemical properties was discussed in detail. As a result, the optimal hydrothermal temperature for synthesizing the nanorod is 150 °C. Furthermore, photocatalytic experiments were also performed under simulated sunlight and natural sunlight. The nature of the photo-oxidative degradation of MB was also investigated.

Preparation and Characterization of Antimony-Doped Tin Oxide Nanocrystallite Coatings on 316L Stainless Steel.

The study on the coatings containing antimony-dope tin oxide mostly has been done on titanium and its alloys for preparation of electrode materials. In this study, we try to prepare the similar coatings on 316L stainless steel, which is more common than titanium, and investigate some characteristics of the formed coatings. The preparation of the coating is by the impregnation of the substrate in solution containing SnCl4 and SbCl3 with the ratio of 93/7, and the concentration of SbCl3, 10 g/L in isopropanol, pH of 1-1.2, and the annealed temperature of 450°C give suitable coating for electrode materials. Some coating features, such as the crystal structure (XRD), morphology (SEM), hardness, electrical resistant, and electrochemical behaviors of the coating on the substrate have been also investigated. The results of the study show that the coatings can be used as electrode materials for the effective treatment of organic colorants in water such as methylene blue in water treatment.

A comparative study of 0D and 1D Ce-ZnO nanocatalysts in photocatalytic decomposition of organic pollutants.

Nanosized zinc oxide is an intriguing material that can be applied in various fields. In this study, Ce doped ZnO nano-catalysts (Ce-ZnO) were synthesized by two different methods (i.e., hydrothermal (Ce-ZnO-HT) and polymer gel combustion (Ce-ZnO-CB) methods) to compare their photodegradation efficiency. The prepared material characteristics were investigated using XRD, SEM, TEM, FTIR, UV-Vis, PL, XPS, EDS, and BET. The bandgap of both nanoparticles (NPs) was 2.95 eV, despite the fact that the morphology of Ce-ZnO-HT NPs was 1D-rod-shaped and that of Ce-ZnO-CB NPs was 0D-spherical. However, the surface area and oxygen vacancy rate of Ce-ZnO-HT NPs were higher than those of Ce-ZnO-CB NPs. These differences are directly related to the photocatalytic activity of Ce-ZnO NPs. Accordingly, the results showed that photocatalytic efficiency was classified in the order Ce-ZnO-HT > Ce-ZnO-CB > pure ZnO, and the photocatalytic reaction rate constant of Ce-ZnO-HT used to decompose MB was 3.0 times higher than that of Ce-ZnO-CB. Interestingly, the photodegradation mechanism study revealed that hydroxyl radicals and holes were shown to be more important contributors to methyl blue degradation than photo-induced electrons and superoxide radical ions.

(C8H22N4Zn)2Ge7O14(OH)F3: a one-dimensional zinc germanate containing hollow columns with an 18-membered window.

A new zinc germanate incorporating a tetradentate amine ligand has been synthesized by the solvothermal method and structurally characterized by single-crystal X-ray diffraction, solid-state (19)F NMR spectroscopy, thermal analysis, and IR spectroscopy. Its structure contains close-packed hollow columns with an 18-membered window, each of which contains six one-dimensional chains formed of Ge(7)X(19) (X = O, OH, F) clusters connected to zinc complexes.

Mixed-valence uranium germanate and silicate: Cs(x)(U(V)O)(U(IV/V)O)2(Ge2O7)2 (x = 3.18) and Cs4(U(V)O)(U(IV/V)O)2(Si2O7)2.

A new mixed-valence uranium germanate and the silicate analogue have been synthesized under hydrothermal conditions at 600 °C and 165 MPa. Their crystal structures contain infinite -U(V)-O-U(IV/V)-O-U(IV/V)-O-U(V)- chains that are connected by Ge(2)O(7) or Si(2)O(7) groups to form a 3D framework with six-ring channels where the Cs(+) cations are located. Two of the Cs sites in the germanate are partially occupied. Bond-valence-sum calculation and an U 4f X-ray photoelectron spectroscopy study confirm the valence states of the uranium.

Cs3UGe7O18: a pentavalent uranium germanate containing four- and six-coordinate germanium.

A pentavalent uranium germanate, Cs(3)UGe(7)O(18), was synthesized under high-temperature, high-pressure hydrothermal conditions at 585 °C and 160 MPa and structurally characterized by single-crystal X-ray diffraction and infrared spectroscopy. The valence state of uranium was confirmed by X-ray photoelectron spectroscopy and electron paramagnetic resonance. The room-temperature EPR spectrum can be simulated with two components using an axial model that are consistent with two distinct sites of uranium(V). In the structure of the title compound, each ([6])GeO(6) octahedron is bonded to six three-membered single-ring ([4])Ge(3)O(9)(6-) units to form germanate triple layers in the ab plane. Each layer contains nine-ring windows; however, these windows are blocked by adjacent layers. The triple layers are further connected by UO(6) octahedra to form a three-dimensional framework with intersecting six-ring channels along the <1 ̅10> directions. The Cs(+) cation sites are fully occupied, ordered, and located in the cavities of the framework. Pentavalent uranium germanates or silicates are very rare, and only two uranium silicates and one germanate analogue have been published. However, all of them are iso-structural with those of the Nb or Ta analogues. In contrast, the title compound adopts a new structural type and contains both four- and six-coordinate germanium. Crystal data of Cs(3)UGe(7)O(18): trigonal, P3̅c1 (No. 165), a = 12.5582(4) Å, c = 19.7870(6) Å, V = 2702.50(15) Å(3), Z = 6, D(calc) = 5.283 g·cm(-3), µ(Mo Kα) = 26.528 mm(-1), R(1) = 0.0204, wR(2) = 0.0519 for 1958 reflections with I > 2σ(I). GooF = 1.040, ρ(max,min) = 1.018, and -1.823 e·Å(-3).

Organically templated metal germanate: ionothermal synthesis of (C8H24N4)[NbOGe6O13(OH)2F].

A very rare organically templated niobium germanate was synthesized and structurally characterized by single-crystal X-ray diffraction. The crystal shows an intense second harmonic generation signal. It is the first example of the synthesis of organically templated metal germanate using an ionic liquid as a solvent.

Cs4UGe8O20: a tetravalent uranium germanate containing four- and five-coordinate germanium.

A very rare tetravalent uranium germanate has been synthesized under hydrothermal conditions at 585 °C and 160 MPa. Its structure contains layers of single-ring Ge(3)O(9)(6-) germanate anions that are connected by UO(6) octahedra and dimers of edge-sharing GeO(5) trigonal bipyramids to form a three-dimensional framework with intersecting 6- and 7-ring channels. UV-visible, photoluminescence, and U 4f X-ray photoelectron spectroscopy were used to confirm the valence state of uranium.

Cs8U(IV)(U(VI)O2)3(Ge3O9)3·3H2O: a mixed-valence uranium germanate with 9-ring channels.

A mixed-valence uranium(IV,VI) germanate has been synthesized under high-temperature, high-pressure hydrothermal conditions. The structure contains discrete U(IV)O(6) octahedra and U(VI)O(6) tetragonal bipyramids, which are connected by three-membered single-ring Ge(3)O(9)(6-) anions to form a three-dimensional framework with 9-ring channels. The U 4f X-ray photoelectron spectroscopy spectrum was measured to identify the valence states of the uranium.