Carbon dots-modified silver nanoparticles as a new colorimetric sensor for selective determination of cupric ions

Abstract

In this work, carbon dots-modified silver nanoparticles (CDs-Ag NPs) were successfully prepared by reducing AgNO3 in the presence of carbon dots (CDs). The prepared CDs-Ag NPs were characterized by using UV–vis spectroscopy, IR spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). Aqueous dispersions of the CDs-Ag NPs showed strong surface plasmon resonance (SPR) absorption band at 430nm. A simple, sensitive, and selective colorimetric Cu2+ sensor was developed on the basis of the strong interaction of functional groups of the CDs incorporated in CDs-Ag NPs with Cu+2 cations which in turn resulted in the aggregation of the nanoparticles and manifested itself in the change of color of CDs-Ag NPs dispersion from orange to red-brown. The main factors affecting the Cu2+ detection, including pH, concentration of CDs, ionic strength, and the interaction time, were optimized for finding out the best conditions for determination of Cu2+. Under the optimum conditions, the analytical response (A525/A430) was linear over the Cu2+ concentration in the range of 0.3–8μM (r2=0.999) and a detection limit of 0.037μM was obtained. The method was successfully used for detection of Cu2+ in tap and river water samples.