Dual Photoluminescence Emission Chiral Carbon Quantum Dots for Ratiometric and Visual Fluorescent Ag+ Sensing

The current methods for the detection of silver ions (Ag+) encounter challenges, including complexity, high cost, potential sample damage, and interference from other ions. In this article, we proposed a facile strategy for the fabrication of dual-emission biomass chiral carbon quantum dots (CQDs) and demonstrated their applications for ratiometric and visual Ag+ sensing. Dual-emission biomass chiral CQDs were synthesized via a two-step hydrothermal method, employing sugar cane molasses as the carbon source, l-cysteine/d-cysteine (L/D-Cys) and Rhodamine B (RhB) as modifiers. The as-prepared CQDs with excellent dispersibility and uniform particle size manifest intriguing enhanced dual-emission behavior at 412 and 580 nm. With increasing Ag+ concentration, both the fluorescence bands at 412 and 580 nm decreased gradually. By monitoring the ratiometric fluorescence variation (F580 nm/F412 nm2), the as-prepared CQDs were developed as an effective platform for highly sensitive and selective ratiometric fluorescent Ag+ sensing, with a wide linear range of 22–220 μM and a low detection limit of 0.14 μM. DFT calculations, UV–vis spectrum, and fluorescence lifetime results confirmed the static quenching mechanism at 412 nm and inner filter effect (IFE) at 580 nm of the as-prepared Ch-CQDs-RhB caused by Ag+. Importantly, we devised a visual liquid scale sensor as well as a visual paper-based colorimetric fluorescent sensor, enabling rapid qualitative and quantitative determination of Ag+.