Microwave fabrication of Cu2ZnSnS4 nanoparticle and its visible light photocatalytic properties

Cu₂ZnSnS₄ nanoparticle with an average diameter of approximately 31 nm has been successfully synthesized by a time effective microwave fabrication method. The crystal structure, surface morphology, and microstructure of the Cu₂ZnSnS₄ nanoparticle were characterized. Moreover, the visible light photocatalytic ability of the Cu₂ZnSnS₄ nanoparticle toward degradation of methylene blue (MB) was also studied. About 30% of MB was degraded after 240 min irradiation when employing Cu₂ZnSnS₄ nanoparticle as a photocatalyst. However, almost all MB was decomposed after 90 min irradiation when introducing a small amount of H₂O₂ as a co-photocatalyst. The enhancement of the photocatalytic performance was attributed to the synergetic effect between the Cu₂ZnSnS₄ nanoparticle and H₂O₂. The detailed photocatalytic degradation mechanism of MB by the Cu₂ZnSnS₄ was further proposed.     

Synthesis and physical characteristics of ZnAl2O4 nanocrystalline and ZnAl2O4/Eu core-shell structure via hydrothermal route

Nanocrystalline zinc aluminate (ZnAl₂O₄) particles with a spinel structure were prepared by hydrolyzing a mixture of aluminum chloride hexahydrate and zinc chloride in deionized water. It was found that pH value and reaction temperature play critical roles in the formation of nano-sized ZnAl₂O₄. Depending on pH values in the precursor solution, ZnAl layered double hydroxide (ZnAl-LDH), ZnO, boehmite or gibbsite could be formed. At pH 7 and T>120 °C, the nanocrystalline ZnAl₂O₄ particles with average particle size of ∼5 nm are easily synthesized through ZnAl layered double hydroxide (ZnAl-LDH). After surface treatment with R-OH by using the cationic surfactant CTAB, the ZnAl₂O₄/Eu core-shell structure can be developed. The ZnAl₂O₄/Eu core-shell structure can show both emissions from ⁵D₀ to ⁷F₂ sensitivity energy level and ⁵D₂ to ⁷F₀ depth energy level.     

Low-temperature synthesis of Bi2Fe4O9 nanoparticles via a hydrothermal method

Bi₂Fe₄O₉ (BFO) nanoparticles were successfully synthesized by a hydrothermal method at a temperature as low as 100 °C. The as-prepared powders, characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM) and physical property measurement system (PPMS), exhibited a pure BFO phase about 100 nm size with uniform sheet-like shape and exhibited an AF order at room temperature. It was found that high alkali concentration and alkali ion Na⁺ played a key role in the formation of BFO nanoparticles at a low temperature of 100 °C.     

Solution transformation of SnS into Cu2ZnSnS4xSe4(1-x) for solar water splitting

Cu₂ZnSnS_4xSe_4(1-x) (CZTSSe) has recently attracted much attention for solar water splitting due to its high absorption efficient and tunable bandgap. However, high quality CZTSSe thin films with good quality and adherence with the substrate are mainly based on physical deposition method, such as magnetron sputtering, which is expensive and energy consuming processes. Here, we have developed a novel and low-cost solution fabrication method and CZTSSe electrodes were synthesized at low temperature by hydrothermal treatment of chemical bath deposited SnS films. The quality and phase purity of CZTSSe thin films were greatly improved after annealing process and the effect of SnS thickness to the physical and photoelectrochemical (PEC) properties of CZTSSe thin films were detailedly studied. The fabrication of FTO/CZTSSe/CdS/TiO₂/Pt photocathode improved the PEC properties of CZTSSe thin films greatly and the highest water splitting photocurrents of 7.2 mA/cm⁻² had been achieved under simulated solar illumination. Furthermore, the electrode showed good stability and had a good incident photon-to-current efficiency (IPCE) response in the visible light range.     

Efficient microwave hydrothermal synthesis of nanocrystalline orthorhombic LiMnO2 cathodes for lithium batteries

Rod-like orthorhombic LiMnO₂ nanocrystals were successfully synthesized using temperature-controlled microwave hydrothermal route (TCMH) in a short time (30 min) at a temperature as low as 160 °C. o-LiMnO₂ obtained by two different methods was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemistry test. SEM revealed that the product obtained in case of TCMH was rod-like with a diameter of 40 nm, while the nanoparticles with 200 nm diameter were obtained by traditional hydrothermal route (TH). The dramatic formation of o-LiMnO₂ in the microwave hydrothermal field influenced the morphology and crystal structure of the final products. The formation and preferred growth orientation mechanism of o-LiMnO₂ in the microwave irradiation process was discussed. Electrochemistry performance exhibited that the as-synthesized o-LiMnO₂ nanorods reached the maximum discharge capacity of 194.2 mAh g⁻¹ at 0.1 C rate after several cycles between 2.2 and 4.4 V vs. Li⁺/Li at room temperature, which was higher than the electrochemical performance of o-LiMnO₂ obtained by TH. The experimental results showed that the TCMH method provided an effective way for preparing o-LiMnO₂ cathode material in lithium-ion batteries.     

p-Type and n-type Cu2O semiconductor thin films: Controllable preparation by simple solvothermal method and photoelectrochemical properties

p-Type and n-type Cu₂O thin films were controllably prepared using a simple solvothermal method by adjusting pH value of the copper (II) acetate aqueous solution. Photoelectrochemical experiments show that the Cu₂O thin films synthesized in acid and alkaline (or neutral) media present n-type and p-type semiconductor character, respectively. Moreover, the films prepared at pH 5 have the best photoelectrochemical properties. The mechanism for the formation of these p-type and n-type Cu₂O films is discussed. The Cu₂O p–n homojunction fabricated in this study shows typical p–n junction character. This facile preparation method may be a promising way to prepare p–n homojunctions for semiconductor devices.     

The Synergistic Effect of Adsorption-Photocatalysis for Removal of Organic Pollutants on Mesoporous Cu2V2O7/Cu3V2O8/g-C3N4 Heterojunction

Cu₂V₂O₇/Cu₃V₂O₈/g-C₃N₄ heterojunctions (CVCs) were prepared successfully by the reheating synthesis method. The thermal etching process increased the specific surface area. The formation of heterojunctions enhanced the visible light absorption and improved the separation efficiency of photoinduced charge carriers. Therefore, CVCs exhibited superior adsorption capacity and photocatalytic performance in comparison with pristine g-C₃N₄ (CN). CVC-2 (containing 2 wt% of Cu₂V₂O₇/Cu₃V₂O₈) possessed the best synergistic removal efficiency for removal of dyes and antibiotics, in which 96.2% of methylene blue (MB), 97.3% of rhodamine B (RhB), 83.0% of ciprofloxacin (CIP), 86.0% of tetracycline (TC) and 80.5% of oxytetracycline (OTC) were eliminated by the adsorption and photocatalysis synergistic effect under visible light irradiation. The pseudo first order rate constants of MB and RhB photocatalytic degradation on CVC-2 were 3 times and 10 times that of pristine CN. For photocatalytic degradation of CIP, TC and OTC, it was 3.6, 1.8 and 6.1 times that of CN. DRS, XPS VB and ESR results suggested that CVCs had the characteristics of a Z-scheme photocatalytic system. This study provides a reliable reference for the treatment of real wastewater by the adsorption and photocatalysis synergistic process.     

Single step electrosynthesis of Cu2ZnSnS4 (CZTS) thin films for solar cell application

The Cu₂ZnSnS₄ (CZTS) thin films have been electrodeposited onto the Mo coated and ITO glass substrates, in potentiostatic mode at room temperature. The deposition mechanism of the CZTS thin film has been studied using electrochemical techniques like cyclic voltammetery. For the synthesis of these CZTS films, tri-sodium citrate and tartaric acid were used as complexing agents in precursor solution. The structural, morphological, compositional, and optical properties of the CZTS thin films have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), EDAX and optical absorption techniques respectively. These properties are found to be strongly dependent on the post-annealing treatment. The polycrystalline CZTS thin films with kieserite crystal structure have been obtained after annealing as-deposited thin films at 550 in Ar atmosphere for 1 h. The electrosynthesized CZTS film exhibits a quite smooth, uniform and dense topography. EDAX study reveals that the deposited thin films are nearly stoichiometric. The direct band gap energy for the CZTS thin films is found to be about 1.50 eV. The photoelectrochemical (PEC) characterization showed that the annealed CZTS thin films are photoactive.     

CuInS2 quantum dot-sensitized TiO2 nanorod array photoelectrodes: synthesis and performance optimization

CuInS₂ quantum dots (QDs) were deposited onto TiO₂ nanorod arrays for different cycles by using successive ionic layer adsorption and reaction (SILAR) method. The effect of SILAR cycles on the light absorption and photoelectrochemical properties of the sensitized photoelectrodes was studied. With optimization of CuInS₂ SILAR cycles and introduction of In₂S₃ buffer layer, quantum dot-sensitized solar cells assembled with 3-μm thick TiO₂ nanorod film exhibited a short-circuit current density (I_sc) of 4.51 mA cm⁻², an open-circuit voltage (V_oc) of 0.56 V, a fill factor (FF) of 0.41, and a power conversion efficiency (η) of 1.06%, respectively. This study indicates that SILAR process is a very promising strategy for preparing directly anchored semiconductor QDs on TiO₂ nanorod surface in a straightforward but controllable way without any complicated fabrication procedures and introduction of a linker molecule.     

Lithium-ion battery anode properties of TiO2 nanotubes prepared by the hydrothermal synthesis of mixed (anatase and rutile) particles

From mixed (anatase and rutile) bulk particles, anatase TiO₂ nanotubes are synthesized in this study by an alkaline hydrothermal reaction and a consequent annealing at 300-400 °C. The physical and electrochemical properties of the TiO₂ nanotube are investigated for use as an anode active material for lithium-ion batteries. Upon the first discharge-charge sweep and simultaneous impedance measurements at local potentials, this study shows that interfacial resistance decreases significantly when passing lithium ions through a solid electrolyte interface layer at the lithium insertion/deinsertion plateaus of 1.75/2.0 V, corresponding to the redox potentials of anatase TiO₂ nanotubes. For an anatase TiO₂ nanotube containing minor TiO₂(B) phase obtained after annealing at 300 °C, the high-rate capability can be strongly enhanced by an isotropic dispersion of TiO₂ nanotubes to yield a discharge capacity higher than 150 mAh g⁻¹, even upon 100 cycles of 10 C-rate discharge-charge operations. This is suitable for use as a high-power anode material for lithium-ion batteries.     

Synthesis of mesoporous nanocrystalline MgAl2O4 spinel via surfactant assisted precipitation route

In this research, mesoporous nanocrystalline MgAl₂O₄ spinel powders were synthesized with a facile synthesis method by co-precipitation route using CTAB as surfactant. The prepared samples were characterized by X-ray diffraction, N₂ adsorption, thermal gravimetric and differential thermal analyses, Fourier transform infrared spectroscopy and transmission electron microscope. The effects of surfactant to metal molar ratio on the structural properties of the samples were investigated. The obtained results showed that the sample prepared without addition of surfactant presented a lower specific surface area and bigger crystallite size compared with those obtained for the samples prepared by CTAB/metal molar ratio of 0.3. The results showed that the sample prepared by CTAB/metal molar ratio of 0.3 has the highest specific surface area and the smallest crystallite size. Moreover, the CTAB/metal molar ratio higher than 0.3 led to a decrease in the specific surface area, due to destruction of the pore walls.     

Preparation of bao-pbo-nd2o3-tio2 powders by hydrothermal synthesis

Homogeneous and nano-sized BPNT [(Ba_1-xPb_x)Nd₂Ti₅O₁₄] powders were prepared under various hydrothermal conditions. Crystallinity and homogeneity of the synthetic powders were investigated. The microwave dielectric properties of the filters prepared with hydrothermal powders were compared with those of the filters prepared with conventional powders. The microwave dielectric properties of the filter prepared with the hydrothermal powders were also better than those of the filter manufactured with the conventional powders. The dielectric constant, quality constant and temperature coefficient of resonance frequency of hydrothermally prepared filter under optimum condition and measured at 3.5 GHz around were about 93, 6067 and 0 ppm/°C, respectively.     

Microstructure and optical properties of nanocrystalline Cu2O thin films prepared by electrodeposition

Cuprous oxide (Cu₂O) thin films were prepared by using electrodeposition technique at different applied potentials (−0.1, −0.3, −0.5, −0.7, and −0.9 V) and were annealed in vacuum at a temperature of 100°C for 1 h. Microstructure and optical properties of these films have been investigated by X-ray diffractometer (XRD), field-emission scanning electron microscope (SEM), UV-visible (vis) spectrophotometer, and fluorescence spectrophotometer. The morphology of these films varies obviously at different applied potentials. Analyses from these characterizations have confirmed that these films are composed of regular, well-faceted, polyhedral crystallites. UV–vis absorption spectra measurements have shown apparent shift in optical band gap from 1.69 to 2.03 eV as the applied potential becomes more cathodic. The emission of FL spectra at 603 nm may be assigned as the near band-edge emission.     

Morphology-controlled synthesis and characterization of bismuth sulfide crystallites via a hydrothermal method

Bismuth sulfide (Bi₂S₃) crystallites with various morphologies have been successfully synthesized via a hydrothermal process assisted by KOH mineralizer. X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated that the mineralizer played a key role in the crystallization and morphology-controlled synthesis of Bi₂S₃ crystallites. The room temperature photoluminescence spectra (PL) showed that uniform rod-shape morphology resulted in better luminescence.     

A hydrothermal reaction to synthesize CuFeS2 nanorods

A hydrothermal reaction route has been developed to prepare chalcopyrite phase CuFeS₂ nanorods at 200–250°C. X-ray powder diffraction and transmission electron microscopy results reveal that the CuFeS₂ synthesized displays nanorods with diameters of 20–40 nm and lengths of up to several micrometers. Elemental analysis gives the atomic ratio of Cu:Fe:S of 1:1.04:2.11. The ⁵⁷Fe Mössbauer spectrum exhibits a six-peak hyperfine magnetic spectrum and a like-splitted line non-magnetic peak. The factors influencing the formation of the CuFeS₂ nanorods were discussed.     

One step synthesis of lamellar R-3m LiCoO2 thin films by an electrochemical–hydrothermal method

In this study, we report the synthesis of lamellar R-3m LiCoO₂ thin films electrodes for lithium rechargeable batteries by a single step method based on an electrochemical–hydrothermal synthesis in a concentrated LiOH solution with a cobalt salt. This process combines the effect of temperature (between 150 °C and 200 °C), pressure and galvanostatic current. The obtained films were not annealed after the electrochemical–hydrothermal synthesis.For the first time, the theoretical study of the potential–pH diagram of cobalt was carried out at high temperature and high concentration. These calculations show that a pH value higher than 12 is necessary to avoid the direct precipitation of cobalt hydroxide Co(OH)₂ inside the solution. An improvement of the soluble species stability with an increase of the temperature and a decrease of the cobalt concentration is predicted. The influence of the deposition conditions (temperature and concentration) at a constant current density was experimentally studied. X-ray diffraction (XRD) shows the formation of well-crystallized LiCoO₂ thin films. Raman spectroscopy confirmed the achievement of the electrochemically active R-3m LiCoO₂ phase without any trace of the Fd3m phase at temperatures as low as 150 °C. Electrochemical measurements demonstrate good performances of the material synthesized between 150 °C and 200 °C with better capacity retention at higher temperature.     

CoFe2O4@SiO2/PrNH2 nanoparticles as highly efficient and magnetically recoverable catalyst for the synthesis of 1,3-thiazolidin-4-ones

An efficient three-component synthesis of 1,3-thiazolidin-4-ones is described by one-pot condensation of aldehydes, aromatic amine and thioglycolic acid with nano-CoFe₂O₄@SiO₂/PrNH₂ as a robust heterogeneous catalyst. The significant advantages of this protocol are the use of magnetically recoverable catalyst, high to excellent product yields, operational simplicity and the use of CoFe₂O₄@SiO₂/PrNH₂ nanoparticles as an environment-friendly catalyst.     

Preparation of hollow porous Cu2O microspheres and photocatalytic activity under visible light irradiation

Cu₂O p-type semiconductor hollow porous microspheres have been prepared by using a simple soft-template method at room temperature. The morphology of as-synthesized samples is hollow spherical structures with the diameter ranging from 200 to 500 nm, and the surfaces of the spheres are rough, porous and with lots of channels and folds. The photocatalytic activity of degradation of methyl orange (MO) under visible light irradiation was investigated by UV-visible spectroscopy. The results show that the hollow porous Cu₂O particles were uniform in diameters and have an excellent ability in visible light-induced degradation of MO. Meanwhile, the growth mechanism of the prepared Cu₂O was also analyzed. We find that sodium dodecyl sulfate acted the role of soft templates in the synthesis process. The hollow porous structure was not only sensitive to the soft template but also to the amount of reagents.     

Continuous hydrothermal synthesis of HT-LiCoO2 in supercritical water

A detailed investigation was made into the production of high temperature lithium cobalt oxide (HT-LiCoO₂) particles by continuous hydrothermal synthesis via the reaction of cobalt nitrate, lithium hydroxide, and hydrogen peroxide. The experiments were carried out in both subcritical and supercritical water, at temperatures ranging from 300 to 411 °C, with residence times less than 1 min in all instances. Although Co₃O₄ particles were synthesized in subcritical water at similar reaction conditions designed for comparison, well-ordered particles of HT-LiCoO₂ were obtained in supercritical water. In supercritical conditions, the variations in temperature and residence time did not have significant impacts on the average particle size, particle size distribution, or morphology of obtained HT-LiCoO₂. However, it was important to supply excessive lithium hydroxide and hydrogen peroxide in order to synthesize single-phased HT-LiCoO₂ particles without undesired by-products. The hydrothermal synthetic route for LiCoO₂, CoO, and Co₃O₄ in both subcritical and supercritical conditions was postulated.     

Hydrothermal assisted synthesis and hot-corrosion resistance of nano lanthanum zirconate particles

The nano La₂Zr₂O₇ (LZ) particles with pyrochlore microstructure were successfully synthesized from a mixture of La(NO₃)₃, Zr(NO₃)₄ and C₁₉H₄₂BrN (CTAB) using hydrothermal assisted (HTA) synthesis which consists of two steps: hydrothermal treatment and calcination. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR) and X-ray diffraction (XRD) spectroscopy were employed to study morphologies and phase compositions. The results suggest that HTA process led to very rapid synthesis of nano LZ compared to the conventional solid reaction process. The particles produced by HTA synthesis have cubic shape and the distribution of its grain size is from 10 nm to 30 nm. The present work demonstrates that the nano La₂Zr₂O₇ produced via HTA synthesis which have better hot-corrosion resistance is an ideal material for thermal barrier coatings.