Biomolecule and surfactant-assisted hydrothermal synthesis of PbS crystals

PbS crystals were hydrothermally synthesized using Pb(NO₃)₂, l-cysteine, and N-cetyl pyridinium chloride in solutions with different pH values at 140 °C. Flower-like, granular and truncated cubic PbS crystals composing of Pb and S were detected using an X-ray diffractometer (XRD), a scanning electron microscope (SEM), a transmission electron microscope (TEM), a selected area electron diffraction (SAED) technique and an energy dispersive X-ray (EDX) analyzer. In addition, a Raman spectrometer revealed the presence of the first and second overtone modes at 436 and 602 cm⁻¹, respectively. Emission spectra of the products were detected at 412 nm using a photoluminescence (PL) spectrometer.     

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.     

Preparation of LiNiVO4 nano-powder using tartaric acid as a complexing agent

LiNiVO₄ was prepared from Li₂CO₃, Ni(CH₃COO)₂·4H₂O and NH₄VO₃ using tartaric acid as a complexing agent with 1:1–1:4 mole ratios of metals:tartaric acid and subsequent calcination at 350–700 °C for 6–12 h. Inverse spinel LiNiVO₄ was detected using XRD. FTIR and Raman analyses revealed the presence of stretching band of VO₄ tetrahedrons. Only Ni, V and O were detected by EDX. The 1:4 mole ratio for the product with 450 °C calcination for 6 h analyzed by SEM, TEM and electron diffraction (ED) composes of LiNiVO₄ nano-powder with 10–30 nm in diameter.     

Nanosized GdVO_4 powders synthesized by sol-gel method using different carboxylic acids

Nanosized GdVO_4 powders were synthesized via a sol-gel method using different carboxylic acids as chelating agent, followed by calcination at 600 ℃ for 3 h.The effect of different carboxylic acids such as citric acid,malic acid, and tartaric acid on the characteristics of the nanosized GdVO_4 powders was investigated. The GdVO_4 powder was also synthesized without carboxylic acid for comparison. The thermal decomposition process of the carboxylate precursors was investigated by thermogravimetric differential thermal analysis(TG-DTA). X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR),field emission scanning electron microscope(FESEM),transmission electron microscope(TEM), and surface area measurement data were used to confirm the formation of nanocrystalline GdV04 powders. It is found that the synthesis using the carboxylic acid with higher heat of combustion results in the powder with larger crystallite size. The difference in the steric effect of the acids used,which was evaluated by a computational method, also affects the degree of agglomeration of the synthesized powders.     

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.     

Methanol–Water System for Solvothermal Synthesis of YVO4:Eu with High Photoluminescent Intensity

A methanol–water mixed solvent was used as a reaction medium for the preparation of Eu³⁺-doped YVO₄ phosphor materials. These were synthesized by a solvothermal method at 150°–300°C using a 10 vol% solution of water in methanol as the reaction medium followed by calcination at 1000°–1200°C. The phase composition and optical properties of the products were characterized by X-ray diffraction, scanning electron microscope, and photoluminescence spectroscopy. The powders obtained were composed of spherical particles ∼0.5 μm in size, with an internal structure that was different for samples prepared under subcritical and supercritical conditions of methanol. After the calcination, the powders obtained at 240°–300°C retained the initial raspberry-like morphology, whereas the morphology of samples prepared at 150°–210°C changed significantly due to noticeable sintering. The fluorescence intensity exhibited by the prepared samples was higher than the fluorescence intensity shown by one of the best commercial YVO₄:Eu phosphors having a large particle size.     

Sonochemical preparation of PbWO4 crystals with different morphologies

PbWO₄ was prepared from Na₂WO₄·2H₂O and Pb(OAc)₂·3H₂O in a solution containing a cationic surfactant (N-cetyl pyridinium chloride) using the sonochemical process (ultrasonic irradiation). The product morphologies, characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), were controlled by the surfactant, pH values and ultrasonic irradiation times. X-ray diffraction (XRD) and selected area electron diffraction (SAED) studies revealed diffraction patterns in good agreement with the simulation model, along with Fourier transform infrared (FTIR) and Raman analyses showed a W–O stretching band consistent with tetragonal PbWO₄. Photoluminescent properties of the pine tree shaped products were also investigated.