Facile synthesis of high-quality nano-sized CdS hollow spheres and their application in electrogenerated chemiluminescence sensing

CdS hollow spheres of about 25 nm average diameter and about 5 nm shell thickness can be easily synthesized in an aqueous solution of polyglycol. It was found that the polyglycol had a significant influence on the formation of the CdS hollow spheres, because when the experiments were carried out in the absence of polyglycol, only solid particles were formed. High-resolution transmission electron microscopy (HRTEM) shows the shell of the CdS hollow spheres is formed by a layer of primary CdS particles. The Brunauer-Emmett-Teller (BET) surface area of the CdS hollow spheres calculated from the N₂ adsorption isotherm is 98.2 m² g^-1, which is much larger than the value of about 49.8 m² g^-1 calculated for the surface area of solid spheres. Compared with previous reports, the prepared hollow spheres have a small diameter, a large surface area and a thin shell. The photoluminescence (PL) spectrum of the CdS hollow spheres at 220 nm excitation shows two sharp emission peaks centered ∼493 nm and ∼530 nm which may be ascribed to the near band edge emission arising from the recombination of excitons and/or shallow trapped electron-hole pairs. Electrogenerated chemiluminescence (ECL) from the CdS hollow spheres and its first application to sensing H₂O₂ were studied. The H₂O₂ sensor based on ECL from the CdS hollow spheres had much better responses than those from CdS solid nanoparticles and had good stability.