Optical properties of colloids formed in copper–tin sulfate solution containing Rhodamine B

Abstract

This paper reports the composition and optical characterization of Sn(IV)–Sn(II) colloidal particles formed in sulfuric acid solution containing Sn(II) and Cu(II) in the presence of sulfur dioxide and Rhodamine B. Precipitated particles from Sn(IV)–Sn(II) colloids were characterized by FTIR, XRD and EPR. Optical properties were evaluated using a homemade transmission spectrometer in the energy range of 1.0–4.0 eV. The colloidal particles consist of copper-doped amorphous SnO2 as the predominant base material with Sn(OH)2(SO4)22− species attached on the surface. The EPR spectra of these materials are typical of Cu2+ ions in axial symmetry, suggesting that some Sn4+ ions in tin dioxide are replaced with Cu2+. Rhodamine B dramatically influences the spectra profile of these materials and also enhances the doping of Cu (Cu2+ and Cu0) in SnO2. An increase in the band gap energy is observed with increasing volume of RhB solution in the reactant media. This demonstrates the possibility of engineering optoelectronic devices with adjustable absorption profiles for a specific application.