SnO2 nanoparticles were prepared by a continuous hydrothermal process carried out in a helical tube reactor (HTR). The products prepared at different hydrothermal temperatures (from 160 degrees C to 300 degrees C) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), selected area electron diffraction (SAED) and UV-Visible spectroscopy (UV-Vis). The obtained SnO2 nanoparticles had a tetragonal structure and mean size of about 4-7 nm. It was found that the mean size of SnO2 nanoparticles increased with the increase of the hydrothermal temperature. The analysis of UV-Visible spectroscopy showed that with an increasing hydrothermal temperature from 160 degrees C to 300 degrees C the optical absorption edge shifted from about 320 nm to 350 nm, responding to the optical band gap value variation from 3.78 eV to 3.50 eV and indicating the red-shifted property of the prepared SnO2 nanoparticles. In addition, when employed as a photocatalyst, the as-obtained SnO2 nanoparticles demonstrated good degradation ability for methylene blue solution. (C) 2014 Elsevier B.V. All rights reserved.