Implementation of surface functionalization of MnS nanoparticles for achieving novel optical properties and improving therapeutic potential.

In the past few years, metal sulfide nanoparticles (NPs) have achieved enormous interest due to their photo and electrochemical properties, which can compete with the existing metal oxide NPs. However, there are fewer reports on the synthesis and the mechanism of surface functionalization of these NPs to achieve intrinsic optical properties. Here, we demonstrate a novel method for the synthesis and the surface modification of manganese sulfide (MnS) NPs to achieve intrinsic photoluminescence and special electrochemical properties. The MnS NPs were characterized using electron microscopy and optical spectroscopic methods. Fourier-transform infrared spectroscopy (FTIR) demonstrated the attachment of citrate on the surface of MnS NPs. The surface modification of insoluble as-prepared MnS NPs by citrate makes them soluble in water. The UV-vis absorption spectra show distinct d-d and ligand to metal charge transfer (LMCT) bands of the citrate-MnS NP nanohybrid. The citrate-MnS NPs exhibited strong photoluminescence. They generated a huge amount of ROS at neutral/acidic pH without any photo-activation which was shown to degrade bilirubin. In addition, the higher ROS generation at pH 5 and pH 7 was exploited to evaluate their anti-bacterial efficacy against Staphylococcus hominis (S. hominis). These observations could pave the path for the designing and development of new-age surface-functionalized metal sulfide NPs for the benefit of human health.