Effect of ZnS coating on the optoelectronic properties of aqueous glutathione capped AgInS quantum dots

Abstract

Ternary I–III–VI quantum dots (QDs) have proved to be promising alternatives to the traditional binary CdQDs due to their inherently lower toxicities, greener synthetic methods, and tunable optoelectronic properties. Their application in the development of biosensors, electroluminescent devices, and a range of other electrochemical applications has resulted in the I–III–VI QDs receiving widespread attention in various fields. In this paper, water-soluble glutathione capped AgInS core QDs and AIS/ZnS core/shell QDs were synthesized using an eco-friendly hydrothermal method. Electrochemical properties of the AgInS core QDs and AgInS/ZnS core/shell QDs were evaluated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). DPV of AgInS core QDs exhibited distinguished oxidation peaks centred at − 0.05 and − 0.88 V vs Ag/AgCl of Ag and In ions, respectively, while the AgInS/ZnS QDs showed three symmetrically oxidation peaks at potentials − 0.87, − 0.66 and − 0.42 V of Zn, In and Ag ions, respectively. The total number of electrons, electron transport diffusion coefficient, De (in cm2 s1 ), and surface concentration of soluble species were evaluated and calculated using the Randles-Sevcik equation. The number of electrons was found to be 1.08 and 0.75 for AgInS QDs and AgInS/ZnS QDs, respectively using the Ag peak and the De value of AgInS QDs was greater than AgInS/ZnS QDs. This indicates that the electron diffusion was the slowest in the AgInS/ZnS QDs. The as-synthesized AgInS core QDs and AgInS/ZnS core-shell QDs exhibited chemical and electrochemical composition-dependent properties. This suggests the material is suitable for the development of biosensors.