Aqueously synthesized color-tunable quaternary Cu-In-Zn-S quantum dots for Cu(II) detection via mild and rapid cation exchange

Non-cadimum photoluminescent I - III - VI semiconductor nanocrystals have attracted increasing attention due to their low toxicity, extraordinary optical and electronic properties. Herein, water-soluble quaternary Cu-In-Zn-S quantum dots (CIZS QDs) with tunable emission from 535 nm to 645 nm were successfully synthesized via ecofriendly one-pot aqueous method. The full width at half-maximum (FWHM) of the emissions are about 68 nm-88 nm, which are rather narrow among Cu-based semiconductors and preferred to facilitate improving color purity. The photoluminescence of water-soluble QDs was enhanced by ZnS coating with the absolute quantum yield (QY) up to 30.8%. Further, a novel fluorescent sensor for Cu2+ detection was developed based on the alteration of intrinsic optical properties of the CIZS/ZnS QDs after cation exchange at room temperature within 10 min, presenting a linear range of 0.020-20 mu M and a detection limit down to 6.7 nM. Mechanism studies revealed that the QDs served as the template for cation exchange, through UV-vis absorption and fluorescence spectra in combination with the chemical composition and time-resolved photoluminescence decay analysis. Ions interference experiments demonstrated the good selectivity of the QDs towards Cu2+ and the sensor showed comparable accuracy to ICP-AES method as well as good performance in real sample detection, manifesting the reliability of the current strategy for sensing Cu2+ mildly and rapidly.