Controlled Synthesis, Growth Mechanism, and Properties of Monodisperse CdS Colloidal Spheres

Abstract

Highly monodisperse submicrometer CdS colloidal spheres (CSCS) with a controllable and tunable size (between 80 and 500 nm) have been synthesized through a facile solvothermal technique. Owing to the controllability of the reaction process, the growth mechanism of the colloidal spheres has been elucidated in detail. The whole growth process can be summarized as homogenous and slow nucleation of nanocrystals, formation of "cores" through 3D-oriented attachment of nanocrystals, and further surface-induced growth to monodisperse colloidal spheres through in situ formation and random attachment of additional nanocrystals. It has been demonstrated that the obtained CSCS colloidal particles are able to be assembled into films which show characteristic stop band gaps of photonic crystals. By using the CSCS as a template, Ag2S, Bi2S3, Cu2S, HgS, and Sb2S3 colloidal spheres, which are difficult to obtain directly, have also been prepared successfully through ion exchange.

Synthesis of Nanoparticles via Solvothermal and Hydrothermal Methods

“…A stainless steel autoclave lined with polytetrafluoroethylene (PTFE) is used as the reactor, and the filling factor is 70 %. The CdS NPs grow from 150 to 450 nm if the reaction time is increased from 5 to 75 min at 140 C [148]. The NP size also increases with increasing Cd 2+ concentrations.…”

“…C , 8 h, and 0.2 M, respectively [148]. In contrast, the NP size reduces with increasing PVP concentration, from 310 to 210 nm, when PVP increases from 0.05 to 0.5 M. These PVP molecules might function as nucleation sites during crystal growth.…”

“…In contrast, the NP size reduces with increasing PVP concentration, from 310 to 210 nm, when PVP increases from 0.05 to 0.5 M. These PVP molecules might function as nucleation sites during crystal growth. Higher PVP concentrations mean more available nucleation sites, which mitigate particle growth and result in smaller particles [148]. This method can also be applied to other sulfides, such as HgS, Ag 2 S, and Bi 2 S 3 [148].…”

“…Higher PVP concentrations mean more available nucleation sites, which mitigate particle growth and result in smaller particles [148]. This method can also be applied to other sulfides, such as HgS, Ag 2 S, and Bi 2 S 3 [148]. Thioglycolic acid and dithiol glycol can also be used as S sources for the synthesis of CdS NPs via hydrothermal or solvothermal methods [149,150].…”

“…Cd(NO 3 ) 2 and thiourea are used as precursors, and polyvinylpyrrolidone (PVP) is employed as a capping agent [148]. A stainless steel autoclave lined with polytetrafluoroethylene (PTFE) is used as the reactor, and the filling factor is 70 %.…”