Time‐Dependent Growth Rates of TGA‐Capped ZnS Nanocrystals as a Synthetic Formula for Ligand‐Capped Quantum Dots

Abstract

ZnS quantum dots (ZnS QDs) are prepared in the absence and presence of thioglycolic acid (TGA) molecules by using a chemical precipitation method. The as‐prepared ZnS QDs are characterized by photoluminescence (PL), UV–vis absorption, Fourier transform infrared (FTIR), and X‐ray powder diffraction (XRD). Based on the calculation from XRD patterns, the temporal evolution of ZnS‐TGA QD size is fashioned and is in agreement with the Ostwald ripening process. The temporal evolution of ZnS–TGA QD size is divided into two regimes and two approximate expressions of growth time (t) − average size (d) as t = Ad3 + B and t = Cd2 + D (A, B, C, D are constants) for lower and higher values of t are suggested, respectively. The growth rates are large in the lower regime and are near zero in the higher regime. The time value at the frontier of these regimes is revealed as the necessary time to synthesize ZnS–TGA QDs. Under the experimental conditions, this value is 60 min (corresponding size of 1.80 nm). This study paves the way for determining the fabrication time of ligand‐capped quantum dots.