Physical and electrochemical characterization of CdS hollow microspheres prepared by a novel template free solution phase method

Novel CdS hollow microspheres have been successfully synthesized via a facile template-free solution-phase reaction from cadmium nitrate and thioacetamide precursors. The morphology of CdS hollow microspheres depends strongly on the ratio between the precursors, cadmium nitrate to thioacetamide ratio. The physical properties of the hollow microspheres have systematically been studied by different characterization methods. The stoichiometry of the hollow microspheres studied by the energy dispersive X-ray diffraction spectroscopy confirmed that the synthesized CdS hollow microspheres are nearly stoichiometric bulk like CdS. The morphology of the hollow microspheres studied by high resolution scanning electron microscopy and transmission electron microscopy observations showed that the CdS hollow microspheres of the size of 2.5 μm have hollow structure and are constructed by several nanoparticles of the size between 30 and 40 nm. The UV-visible diffuse reflectance spectroscopy studies showed that the band gap of the CdS hollow microspheres increased while increasing the cadmium nitrate to thioacetamide ratio. Further electrochemical characterization of CdS hollow microspheres was performed with glassy carbon electrode (GCE) after its chemical modification by CdS dispersed in dimethylformamide. The electrochemical studies showed that with decreasing the band gap energy the electron transfer resistance of CdS/GCE was also found decreased. Moreover, electrochemical impedance spectroscopic measurements showed enhanced DNA adsorption onto CdS/GCE in comparison to GCE. These experiments demonstrate that the CdS hollow microspheres act as an efficient electrode modifier that effectively decreased the charge transfer resistance and capacitance of the modified sensors, which can be used for electroanalytical purposes.