Non-cytotoxic lanthanum and nitrogen co-doped lignin-based carbon dots for selective detection of ions in biological imaging

Owing to their versatility, fluorescent carbon quantum dots (CQDs) have attracted significant attention for applications in sensors, bioimaging, microfluidics, photodynamic therapy, drug delivery, light-emitting diode, etc. Herein, nitrogen and lanthanum co-doped multifunctional lignin-based carbon quantum dots ((N, La)-CQDs) were prepared from enzymatic hydrolysis lignin using a simple one-step hydrothermal method. The diameter of the CQDs obtained was about 2.2 nm with a good water solubility at the excitation wavelength of around 365 nm and emission wavelength of around 465 nm. This is the first discovery of (N, La)-CQDs to detect Sn2+. (N, La)CQDs were successfully used to detect Fe3+, Sn2+, and ClO- ions in the range of 0-100 & mu;M with the detection limits of 0.99 & mu;M, 1.1 & mu;M and 1.1 & mu;M sequentially, and the linear fit R2 of 0.9997, 0.9943 and 0.9941 respectively. Non-cytotoxic (N, La)-CQDs can be used for labeling cells and detecting Sn2+ in zebrafish. These attractive features make these non-toxic, environmentally friendly CQDs material highly promising for applications in a wide range of areas, such as biomedicine, biosensing, disease diagnosis, and environmental monitoring.