A facile synthesis of high-efficient N,S co-doped carbon dots for temperature sensing application

A high-efficient nitrogen and sulfur-doped carbon dots (CDs) were prepared from L-Cysteine (Cys) and trisodium citrate dihydrate using a hydrothermal method. The Cys-CDs were completely water-soluble and remarkably stable under various pH and ionic strength conditions. Cys-CDs show a absorption maximum at 350 nm and PL maximum at 450 nm with high fluorescence quantum yield of 68%. It is found that Cys-CDs exhibit linear temperature-dependent emission intensity responses at in the 283-343 K range, along with strongly temperature dependent monoexponential decay. The mechanism of temperature-dependent fluorescence is confirmed as temperature enhanced population of non-radiative channels by comparing radiative and nonradiative recombination rates at different temperature. All results indicate that Cys-CDs could be a promising material for fluorescent temperature-sensing application.