Facile synthesis of NaYF4:Yb, Er-Ag2S nanocomposite, upconversion emission, microbubble formation by optical tweezer and in-vitro photodynamic therapy studies

Abstract

Photon upconversion and metal sulphide-based nanocomposites find potential applications for NIR mediated photodynamic and photothermal therapy. Present work investigates the effect of three different novel synthesis strategies on forming ultrasmall NaYF4:Yb, Er - Ag2S nanocomposites by thermal decomposition and hydrothermal methods by utilising different silver and sulphur precursors. The Ag2S was employed as an acceptor for the upconverted photon, which has an influence on fluorescence resonance energy transfer (FRET). An efficient FRET between the NaYF4:Yb,Er and Ag2S was confirmed by a decrease in the upconversion emission intensity and decay lifetime, and this phenomenon can support photodynamic and photothermal effect. In addition to upconversion emission and FRET studies, we explored the microbubble formation phenomenon for the first time in the NaYF4:Yb,Er-Ag2S at 975 nm diode laser interaction to demonstrate photothermal effect. Also, the reactive oxygen species (ROS) generation by photodynamic effect on 975 nm diode laser interaction was investigated with the 1,3-diphenylisobenzofuran (DPBF) as the ROS sensor. The cytotoxicity studies showed a high biocompatibility of the NaYF4:Yb, Er-Ag2S. The photodynamic therapeutic (PDT) study performed even at a low power density of 100 mW cm-2 with the 975 nm diode laser showed an excellent PDT property. The present investigation confirms the suitability of NaYF4:Yb, Er-Ag2S for NIR light mediated photodynamic and photothermal therapy applications.