A facile synthetic strategy to simultaneously achieve ultra-wide PL redshift of carbon nanodots and their high selectivity and sensitivity for Mn2+ detection

This paper presents a straightforward synthesis strategy for N, S co-doped carbon nanodots (N, S-CDs), aiming to achieve CDs emitting ultra-wide redshifts while obtaining excellent metal ion detection performance. The N, S-CDs display excellent fluorescence (FL) emission independence regardless of the excitation wavelength or concentration. By introducing a single dopant thiourea, the FL emission of CDs was red-shifted from 445 to 575 nm (∼130 nm). The doped N and S elements are discovered to cause the introduction of defective energy levels and an elevation in oxidation on the surface of CDs, which could potentially be the crucial factor for the ultra-wide redshift of FL emission. Also, it is investigated that solvent engineering is essential for the redshift of the emission peak, which can also be an effective way to synthesize multicolor CDs. Furthermore, the N, S-CDs can be utilized for measuring the water content in methanol solvent based on their solvent effects. Additionally, N, S-CDs have the capability of detecting Mn2+ with high selectivity and sensitivity. The interaction of CDs with Mn2+ resulted in an obvious change in both the UV absorption spectrum and FL lifetime. To put it differently, the reaction mechanism between CDs and Mn2+ probably includes mixed processes of dynamic and static quenching. Zeta potential tests additionally indicate that the FL quenching is strongly correlated with the surface condition of CDs. The outcomes and discoveries offer a fresh and viable method for achieving the simultaneous production of long-wavelength glowing CDs and their analysis and detection of metal ions as fluorescent probes.