Nitrogen and sulfur co-doped carbon dots: facile synthesis and multifunctional applications for pH sensing, temperature sensing and RNA-selective imaging

Abstract Heteroatoms doped carbon dots (CDs) have attracted extensive attention for their superior optical properties, facile preparation and multifunctional applications in environmental detection, cell imaging and gene delivery. Herein, Nitrogen and sulfur co-doped carbon dots (N,S-CDs) were synthesized directly from methyl cellulose (MC), L-cysteine (L-cys) and ethylenediamine (EDA), showing excitation-dependent emission properties and relative high quantum yield (QY) of 12.3%. The obtained N,S-CDs are responsive to pH and temperature, suggesting pH- and temperature-dependent fluorescent features. Moreover, N,S-CDs are utilized to image and exhibit selective location inside the nucleus region both in living and fixed cells. Relative mechanisms have been explored by ribonuclease digestion testing and co-staining analysis with commercial nucleic acid dye. N,S-CDs show the specifical distribution in RNA-rich regions and positive response to RNA in cells. In brief, the developed N,S-CDs possess multi-faced application potency in pH sensing, temperature monitoring and RNA-selective imaging in cells.