Fig. 3. (a) The absorption spectra of the bulk ReS₂ and utReS₂ nanosheets. (b) The absorption spectra of RSV and utReS₂@RSV–FA. (c) The fluorescence spectra of utReS₂, RSV and utReS₂@RSV–FA. (d) RSV loading ratio onto bulk ReS₂ and utReS₂ as the function of added RSV concentrations. (e) The average size change of utReS₂@RSV–FA in water, FBS, cell media, PBS and saline over 7 days. (f) The absorbance ratio change of utReS₂@RSV–FA between 304 nm and 280 nm (A_{304 nm}/A_{280 nm}) over 7 days.