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

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 Cu 2+ traces. The Cu 2+ 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 Cu 2+ traces in industrial wastewater or solutions. In addition, amino-functional CDs are successfully used to detect Cu 2+ in a mixed solution of different metallic salts, that demonstrate good selectivity and provide promising applications for biosensing, imaging, or disease diagnosis. • The NH2-CDs were simultaneously designed from chitosan through a simple carbonization process. • The NH2-CDs exhibited high QY (6.28%; 330 nm Ex), long photostability, low interference, and ease of preparation. • The fluorescent signals had a broad linear range of Cu2+ detection (short-ranging: from 0 to 100 μM). • The NH2-CDs demonstrated sensitive and selective detection of Cu2+ as a nanosensor with the low DL of 105.7 nM.