Colloidal suspension of binary sulfides of copper and indium were generated by the reaction of CuCl and In2(SO4)3 with thiourea independently in ethyleneglycol. The colloids were identified to be Cu9S5 and a mixture of InS and In2S3 from the TEM-SAED measurements. They were reacted to yield phase pure CuInS2 in zincblende arrangement as endorsed by the powder X-ray diffraction pattern, TEM-SAED, lattice fringe measurements and Raman spectroscopy measurements. Optical band gap of zincblende CuInS2 was measured using UV–visible spectroscopy. In the photoluminescence spectrum, a strong emission centred at around 750nm was observed on exciting the sample with λ=500nm. Following this success, quaternary composition containing Cu, In, Fe and S in zincblende arrangement has been synthesized and characterized. Band gap of iron substituted samples was estimated to be 1.07eV. It showed paramagnetic behaviour at room temperature suggesting its use as opto-magnetic material. While cubic CIS degraded methylene blue dye solution under visible light radiation, iron substituted sample did not promote this reaction.