In this paper, we demonstrate a simple and efficient method for synthesis of β-indium sulphide (In 2 S 3 ) nanoparticles embedded in an ionomer matrix (nafion membrane). The influence of reaction temperature on structural, compositional and optical properties of these films were analysed using X-Ray Diffraction, EDAX, UV-Vis absorption spectroscopy and photoluminescence studies. Average particle diameter was estimated using modified effective mass approximation method. Absorption spectra of In 2 S 3 nanoparticles show blue shift compared to bulk In 2 S 3 , indicating strong quantum size confinement effects. PL emission in the wavelength range 530-600 nm was recorded using a 488 nm line from an Ar + laser as the excitation source. © 2014 AIP Publishing LLC.