Synthesis and Electrophoretic Concentration of Cadmium Sulfide Nanoparticles in Reverse Microemulsions of Tergitol NP-4 in n-Decane

Abstract

The kinetics of thiourea synthesis of CdS nanoparticles (NPs) in reverse microemulsions of Tergitol Np-4/n-decane was studied in the temperature range of 313-333 K by spectrophotometry, photon-correlation spectroscopy, and transmission electron microscopy. The formation of NPs is described by the kinetic model, including two consecutive steps: homogeneous nucleation in a solution as the first step and the autocatalytic growth of NPs due to heterogeneous reaction on a continuously increasing surface as the second step. Effective rate constants of the steps (k = 1.52 × 10-1.75 × 10 s and k = 4.9 × 10-5.1 × 10 M s) and effective activation energies (E = 156 and E = 149 kJ/mol) were estimated in the pseudo-first-order reaction with respect to cadmium (c = 0.9 mM, c = 9 mM). The obtained constants were used to calculate the dependence of nanoparticle diameter on the synthesis time (d ∼ t). The calculated values correlate well with experimental data of photon-correlation spectroscopy and transmission electron microscopy.