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

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Abstract
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.