Phonon Characterization, Structural and Optical Properties of Type-II CdSe/CdTe core/shell and Type-II/type-I CdSe/CdTe/ZnS core/shell/shell Quantum Dots

Abstract

The CdSe, type-II CdSe/CdTe core/shell and type-II/type-I CdSe/CdTe/ZnS core/shell/shell quantum dots (QDs) were successfully synthesized in a noncoordinating solvent. The phonon characterizations, optical properties and structures of the synthesized QDs were characterized by Raman scattering (RS) spectra, photoluminescence (PL) spectroscopy, PL-decay lifetime, absorption spectroscopy (Abs), and X-ray diffraction (XRD). The growth of QDs was monitored by using RS, which demonstrated the formation of correct of the core/shell and core/shell/shell structures. Observation results from XRD reveal that all QDs crystallize in the cubic phase with zinc-blende structure. The typical characteristics of spatially indirect recombination for type-II QDs were observed through Abs and PL spectroscopy. The ZnS shell significantly enhanced the PL quantum yeild (QY), the optical durability, the chemical stability and separating CdSe/CdTe QDs from the surroundings. The effect of excitation power on the PL properties of the CdSe core, CdSe/CdTe and CdSe/CdTe/ZnS QDs has been investigated.

One-Pot Synthesis of CdTe/ZnS Quantum Dots and their Physico-Chemical Characterization

“…[15] To prevent the effects of toxicity by a possible diffusion of metals due to the oxidation of the imperfections on the nanocrystal surface, a shell of nontoxic material is deposited on nanocrystal surface. In this case, the synthesis of materials for core/shell (CS) structures depends on the band gap energy and the location of the energy levels of the semiconductor electronic components [16][17][18][19]. In the present research, ZnS was deposited on the CdTe nanocrystal surface since this compound is not dangerous for living organisms and is a chemically stable semiconductor material.…”