At present, solvothermal fabrication method has widely been applied in the synthesis of spinel ferrite nanoparticles (SFNs), which is mainly because of its great advantages such as precise control over size, shape distribution, and high crystallinity that do not require postannealing treatment. Among various SFNs, Fe3O4 nanoparticles have attracted tremendous attention because of their favorable physical and structural properties which are advantageous, especially in biomedical applications, among which the vast application of these materials as targeted drug delivery systems, hyperthermia, and imaging agents in cancer therapy can be mentioned. The main focus of this study is to present an introduction to solvothermal method and key synthesis parameters of SFNs through this synthesis route. Moreover, most recent progress on the potential applications of Fe3O4 nanoparticles as the most important compound among the spinel ferrites family members is discussed.

CuInS2 nanostructures were synthesized via a simple surfactant-free solvothermal route. In this synthesis, thiosemicarbazide and thioglycolic acid were used as sulfur sources. The effects of different parameters such as type of precursor and time on the morphology and particle size of the samples have been investigated. The nanostructures were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive Xray analysis (EDX), Fourier transform infrared (FT-IR) and photoluminescence (PL) spectroscopy. The fill factor (FF), open circuit voltage (VOc), and short circuit current (Isc) were obtained by I–V characterization.

The aim of this work was to characterize copper ferrite nanoparticles synthesized via solvothermal method and to investigate the effects of ultrasonic waves on the synthesis efficiency. Crystal structure, functional groups, microstructure, particle size, magnetic properties, specific surface area, porosity distribution and photocatalytic activity of the synthesized nanoparticles were also investigated. Structural analyses revealed that nanostructured copper ferrites with spinel crystal structure have been successfully synthesized via both solvothermal and ultrasonic-assisted solvothermal methods. The powders contained submicron spheres which were consisted of nanoparticles with regular arrangement. The applied ultrasonic wave had significant effect on the shape and size of the spheres, particularly on their specific surface area, but it had no considerable effect on the magnetic properties. All the synthesized powders were superparamagnetic and their band gap energy was about 1. 5 eV. High absorption rate is another unique characteristic of the powders so that it can complete the photocatalytic process in less than 10 min. The saturation magnetization of about 47 emu/g, together with negligible coercivity, make the synthesized nanostructured absorbent ideal for magnetic separation processes.

Titanium dioxide was prepared under high temperature and pressure by solvothermal method. XRD crystallography of TiO2 showed decreases in crystalline size with increasing temperature, which means an increase in the surface area that increases the activity of the compound. Whereas in B-TiO2, the crystal size decreased to  and then increased again at, and it was a doping of 5% by weight of boric acid. We used temperatures of 70, 100, 130, 160 and 190 °C, respectively, and the energy gap values in the pure state were 3.23, 3.21, 3.11, 3.04 and 3.01 eV, respectively, while the energy gap values for B-TiO2 were 2.94, 2.5, 2.7, 2.4 and 3.04 eV, respectively. XRD measurements were taken at three temperatures of 70, 130 and 190, respectively. The crystal thickness according to XRD measurements for pure substance was 29.1, 7.61, and 1.046 nanometers, respectively, while crystal thickness for B-TiO2 was 15.575, 6.887, and 9.79 nanometers, respectively. FE-SEM measurements were taken at three temperatures of 70, 130, and 190, respectively. The diameters of the crystals according to FE-SEM measurements for TiO2 were 19.245, 24.00286, and 25.21 nanometers, respectively, while the crystal diameters for B-TiO2 were 13.68, 60.68714 and 57.00714 nanometers, respectively. The shapes of nanoparticles ranged between nanorods, nanotubes, and nanoflowers. We expect these structures to have promising future features in various applications.

Titanium oxide nanoparticles were synthesized via a solvothermal treatment of titanium isopropoxide in the presence of L-lysine (lysine). The prepared nanostructures characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), diffraction scanning calorimetry (DSC), scanning electronic microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Results exhibited that peptization in the absence of the additive led to the non-uniform (from nano to micro size) anatase particles, while well-dispersed anatase nanoparticles were obtained in the small range from titania-lysine precursor. Well-organizing the growth of anatase particles during the calcinations can be attributed to initial amorphous phase of the as-synthesized lysine sample.