Role of silica coating in influencing emission properties of CdSe NPs and photodegradation of methylene blue solution

Core shell nanoparticles (NPs) of CdSe@SiO₂ have been prepared by Sol–Gel method using bare CdSe NPs as template. The XRD, SEM and TEM results show that CdSe NPs are of hexagonal phase, with crystallite size ranging from 3 to 5 nm for CdSe and around 7 nm for CdSe@SiO₂ NPs. Fourier transform infrared spectroscopy study confirms the presence of silanol groups bonded to core shell NPs. Optical studies carried out by using UV–Vis and photoluminescence spectroscopy show symmetric intense peak with blue shift of 320 nm in PL spectrum for bare CdSe as compared to its bulk counterparts. The effect of surface modification by silica coating on CdSe (mass:volume ratio of CdSe:TEOS) NPs and the photodegradation of methylene blue (MB) solution has been studied. Degradation of MB is caused by photo-generated free radicals, which gets improved with mass ratio of CdSe:SiO₂ i.e. from 0.107 to 0.0535 thereby increasing the stability of photocatalyst and its performance from 22 to 35 %, its reaction kinetics being of pseudo first order. Recyclic study showed degradation rate of 88.57 % after 4th cycle thus showing efficacy in the treatment of problems related to degradation of MB solution.