Exploring the surfactant structure efficacy in controlling growth and stability of HgS nanoparticles in aqueous medium
Sanjay Kumar, S.K. Mehta, Vaishali Thakur, Aseem Vashisht, Kulvinder Singh
Abstract
Surfactants exhibit many inherent properties, one of the properties is their favorable capacity to absorb at the interface or surface in which surfactant molecules are transferred from bulk phase of solution to the interface. With the evolution in the synthesis routes of nanoparticles (NPs) via colloidal chemistry approaches, now the adsorption capacity of surfactants is being exploited concerning the stabilization of the NPs. In present research work, colloidal mercuric sulfide nanoparticles (HgS NPs) have been synthesized with effective sizes below 15 nm in aqueous solutions of various surfactants through facile chemical precipitation technique. Different head groups and hydrophobic chain length moieties have been tested for various cationic and anionic surfactants. These surfactants have been demonstrated to produce dispersed spherical configured HgS NPs, in which the composition of surfactant has controlled growth assessment. Although, the NPs in the pulverized form exhibit β-HgS form except of the surfactant opted. Surfactant adsorption at the surface of NP has been shown due to change in inter-particle potential and prevents the self-aggregation of NPs. Additionally, it has been demonstrated that the surfactants (stabilizers) have some favorable chemical moiety which promotes the binding at NP surface, generates an adequate size of particles and eventually inhibits their unlimited growth. The kinetics of nucleation and growth of surfactant stabilized HgS NPs follows the first-order rate law in all the surfactants. However, the first order rate constant has shown prominent surfactant dependence.