Temperature dependent luminescence of azobenzene capped CdS quantum dots

Cadmium sulfide (CdS) quantum dots (QDs) are prepared at room temperature by "form-fill-seal" method, while the azobenzene is used as surfactant to control the particle size and to prevent agglomeration. The typical size of CdS nanoparticles is estimated as 2 nm by X-ray diffraction. The absorption spectra of CdS QDs are measured at room temperature and a new absorption peak associated with the surface excited state is found. The luminescence property of the CdS QDs is studied at room temperature and low temperature. Two photoluminescence peaks exist in the temperature range of 8-300 K. One peak at 460 nm is attributed to CdS QDs, while the other one at 667 nm comes from the transition of surface excited state and its intensity decreases with temperature increasing.