The effect of solvents on ZnS nanostructures synthesized by biomolecule-assisted solvothermal method

Nanostructured ZnS (hexagonal and cubic) were synthesized by a 200 °C and 24 h solvothermal reaction of Zn(CH₃COO)₂·2H₂O and l-cysteine (C₃H₇NO₂S) in water, propylene glycol (PG) and glycerol (GR) solvents. The products, characterized by XRD, were specified as pure ZnS (hexagonal) in water, and ZnS (cubic) in PG and GR. SEM and TEM analyses showed the particle sizes and agglomerated behaviors, mainly related to the reaction media, which were in accordance with BET adsorption of nitrogen, with blue shift energy gaps relative to the bulk.     

Photocatalytic activity of La-doped ZnO nanostructure materials synthesized by sonochemical method

ZnO nanostructure materials doped with different La contents were synthesized by sonochemical method. The products were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM),transmission electron microscopy(TEM), Raman spectroscopy, and Fourier transform infrared spectroscopy(FTIR). In this research, XRD patterns of pure ZnO and La-doped ZnO are specified as hexagonal wurtzite ZnO structure with no detection of La2O3 phase. SEM and TEM characterization revealed the flower shape of pure ZnO built-up from petals of hexagonal prisms with hexagonal pyramid tips. Upon doping with La, the flower-shaped ZnO is broken into individual 1D prism-like nanorods. Photocatalytic activities of the as-synthesized products were determined by measuring the degradation of methylene blue(MB) under ultraviolet–visible(UV) light irradiation.Among them, the 2.0 mol% La-doped ZnO shows better photocatalytic properties than any other products.     

Characterization of SrWO4-PVA and SrWO4 spiders’ webs synthesized by electrospinning

Mixtures of strontium acetate, ammonium metatungstate hydrate, and different contents of poly (vinyl alcohol) (PVA, 125,000 MW) were electrospun by a +15 kV direct voltage to synthesize SrWO₄-PVA spiders’ webs. The spider's web, synthesized from the solution containing 1.3 g PVA, was further calcined in air at 300-600 °C for 3 h. The SrWO₄-PVA spider's web was analyzed by thermogravimetric analyzer (TGA) to specify the evaporation and decomposition of PVA and volatile components. In addition, the SrWO₄-PVA and SrWO₄ spiders’ webs were characterized by X-ray diffractometer (XRD), selected area electron diffraction (SAED), scanning and transmission electron microscopes (SEM, TEM), and ultraviolet (UV)-visible and photoluminescence (PL) spectrometers, including the vibration modes by Fourier transform infrared (FTIR) and Raman spectrometers. A possible formation mechanism of SrWO₄-PVA and SrWO₄ spiders’ webs was also proposed according to the experimental results.     

Solvothermal synthesis of CdS nanowires templated by polyethylene glycol

CdS nanowires were solvothermally synthesized from Cd(NO₃)₂ and S powder using ethylenediamine as a solvent and polyethylene glycol (PEG) as a template. Hexagonal CdS with P6₃mc space group was detected using XRD and SAED, results which are in good accordance with those obtained by the simulation. SEM, TEM and HRTEM revealed the gradual development of nanowires in the [0 0 1] direction with a number of atoms aligning in a crystal lattice. Raman spectra of different products showed the fundamental and overtone modes at the same wavenumbers of 300 and 601 cm⁻¹, respectively. Their relative intensities at different molecular weight PEG were influenced by the anisotropic geometry of the products. Their photoluminescence peaks were detected at the same wavelengths of 518 nm. A formation mechanism for CdS nanowires was also proposed to relate to the experimental results.     

Formation of LiNi0.5Co0.5VO4 nano-crystals by solvothermal reaction

LiNi_0.5Co_0.5VO₄ nano-crystals were solvothermally prepared using a mixture of LiOH·H₂O, Ni(NO₃)₂·6H₂O, Co(NO₃)₂·6H₂O and NH₄VO₃ in isopropanol at 150–200 °C followed by 300–600 °C calcination to form powders. TGA curves of the solvothermal products show weight losses due to evaporation and decomposition processes. The purified products seem to form at 500 °C and above. The products analyzed by XRD, selected area electron diffraction (SAED), energy dispersive X-ray (EDX) and atomic absorption spectrophotometer (AAS) correspond to LiNi_0.5Co_0.5VO₄. V–O stretching vibrations of VO₄ tetrahedrons analyzed using FTIR and Raman spectrometer are in the range of 620–900 cm⁻¹. A solvothermal reaction at 150 °C for 10 h followed by calcination at 600 °C for 6 h yields crystals with lattice parameter of 0.8252 ± 0.0008 nm. Transmission electron microscope (TEM) images clearly show that the solvothermal temperatures play a more important role in the size formation than the reaction times.     

Malic acid complex method for preparation of LiNiVO4 nano-crystallites

LiNiVO₄ nano-crystallites were prepared by the polymerized complex method using Li₂CO₃, Ni(CH₃COO)₂·4H₂O and NH₄VO₃ as starting reagents and malic acid as a complexing agent. With the subsequent calcination at 450 °C, the powder analyzed by XRD, FTIR, Raman, electron diffraction, SEM and TEM techniques was found to be inverse spinel LiNiVO₄ with ∼20 nm in diameter. TGA shows continuous weight loss at 40–450 °C due to the evaporation and decomposition processes. Above 450 °C, weight percent tended to be constant. In addition, formation mechanism of the purified LiNiVO₄ was proposed to relate with the experimental results.     

Effects of ethylenediamine to water ratios on cadmium sulfide nanorods and nanoparticles produced by a solvothermal method

Cadmium sulfide nanorods and nanoparticles were successfully produced by a solvothermal reaction at 200 °C for 24 h using ethylenediamine and water as pure and mixed solvents. The products were analyzed by X-ray diffraction, Raman spectroscopy and transmission electron microscopy. In pure ethylenediamine, they show the hexagonal structure CdS nanorods with 0.2-2 μm long and 30 nm diameter, and the 1LO and 2LO modes at 299.36 and 600.72 cm^− 1, respectively. Growth of CdS nanorods is along the [001] direction, interpreted by HRTEM images and SAED patterns. In the 50:50 vol.% of ethylenediamine:water mixed solvents, the length of CdS nanorods decreased to 100-200 nm. The CdS nanoparticles were produced when pure water was used.     

Characterization of Bi2S3 with different morphologies synthesized using microwave radiation

Bi₂S₃ with different morphologies (nanoparticles, nanorods and nanotubes) was synthesized using bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) and two kinds of sulfur sources (CH₃CSNH₂ and NH₂CSNH₂) in different solvents (water, ethylene glycol and propylene glycol) via a microwave radiation method at 180 W for 20 min. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that all of the products are orthorhombic Bi₂S₃ phase of nanoparticles, nanorods and nanotubes, influenced by the sulfur sources and solvents. Formation mechanisms of the products with different morphologies are also proposed.     

Characterization of AgBiS2 nanostructured flowers produced by solvothermal reaction

AgBiS₂ nanostructured flowers were produced from CH₃COOAg, Bi(NO₃)₃.5H₂O and thiosemicarbazide (NH₂CSNHNH₂) using different solvents [ethylene glycol (EG), water (H₂O), polyethylene glycol with molecular weight of 200 (PEG200), and propylene glycol (PG)] in Teflon-lined stainless steel autoclaves. The phase and purity were detected using X-ray diffraction (XRD), controlled by the solvents. The product was purified AgBiS₂ produced by the 200 °C and 24 h reaction in EG, corresponding to selected area electron diffraction (SAED) and simulation patterns. Scanning and transmission electron microscopies (SEM and TEM) revealed the formation of nanostructured flowers — enlarged by the increase in the lengths of time and temperature. Their photoluminescence (PL) emissions were detected at the same wavelength of 382 nm (3.24 eV), although they were produced under different conditions.     

Characterization of Li1−x Ni1+x O2 prepared using succinic acid as a complexing agent

Li_1−x Ni_1+x O₂ was prepared by a polymerized complex method using succinic acid as a complexing agent. Ethanolic solutions of lithium acetate dihydrate, nickel acetate tetrahydrate, and succinic acid were mixed to form carboxylate precursors, which were subsequently calcined at 650–800°C for 14–48 h. TGA curves of metal acetates, succinic acid, and the precursors were characterized to determine weight loss and formation temperature of the oxide. By using XRD, SEM, and EDX, pure crystals of Li_1−x Ni_1+x O₂ were detected at 750 and 800°C. The maximum and minimum intensity ratios of XRD spectra show that the optimum calcination condition is 750°C for 40 h. At 650–800°C, the particle size distribution is in the range of 0.35–39 μm. The text was submitted by the authors in English.