Highly efficient fluorescent probes from chitosan-based amino-functional carbon dots for the selective detection of Cu2+ traces

Abstract

Carbon dots (CDs) have been rising intensely as a new fluorescent nanomaterial in recent years with their outstanding features for various potential applications. In this respect, the blue-green fluorescence CDs are successfully synthesized via the one-step simple and green carbonization method using chitosan as a carbon precursor. The as-prepared CDs hold the beneficially functional groups of amines on the surface with a high quantum yield of 6.28% under an excitation of 330 nm, and they are employed for fluorescently sensing copper(II) ions. Additionally, the CDs have excellent stability both in ambient conditions and even under the continuous irradiation of UV light (365 nm) for 1.5 h. Experimental results show that the as-synthesized nanometric particles have a nearly monodisperse and quasi-spherical structure with an average diameter of 4.9 nm and thickness of 5.1 nm, moreover, they exhibit very high fluorescence sensitivity and effective selectivity when the existence of Cu2+ traces. The Cu2+ detection depends almost on their dispersion rate and pH value in initial solutions with the detection limit as low as 105.7 nM within a linear wide dynamic range from 0 to 100 μM, which could offer a useful platform for identifying the Cu2+ traces in industrial wastewater or solutions. In addition, amino-functional CDs are successfully used to detect Cu2+ in a mixed solution of different metallic salts, that demonstrate good selectivity and provide promising applications for biosensing, imaging, or disease diagnosis.