Synthesis and Spectroscopic Characterization of Manganese Doped Zinc Sulfide Quantum Dot Nanocrystals

Author

Pedro A. Gonzalez Beerman, Western Michigan University

Date of Award

6-2005

Degree Name

Doctor of Philosophy

Department

Chemistry

Abstract

Zinc sulphide quantum dots were synthesized in aqueous media using sodium polyphosphate as the stabilizer. The nanoparticles were 2.5 ± 0.5 nm and 5.0 ± 0.5 nm diameter depending on the synthetic procedure employed and the amount of Mn doped varied from 0.003 to 0.32% (w/w). The nanoparticles were characterized by UV-Vis absorption, luminescence, EPR, near edge x-ray absorption fine structure (NEXAFS), and x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD), and transmission electron microscopy (TEM). These quantum dots show a strong emission at 590 nm due to the ⁴T₁ -⁶A₁ transition characteristic of Mn occupying Zn positions in the lattice in a slightly distorted T_d site. The intensity of the emission at 590 nm increases asymptotically with the concentration of Mn(II) while the lifetime of this emission decreases. The EPR data reveal that Mn²⁺ exists in at least three different types of environments: a slightly distorted T_d site, a highly distorted site near the surface of the nanoparticle and surface sites where Mn²⁺ is adsorbed. The sites responsible for the luminescence of ZnS:Mn are the Td sites inside the nanoparticle. The 590 nm emission is enhanced when the nanoparticles photo-react with cysteine. This change in intensity could be employed for the design of nanosensors.

Access Setting

Dissertation-Open Access

Recommended Citation

Gonzalez Beerman, Pedro A., "Synthesis and Spectroscopic Characterization of Manganese Doped Zinc Sulfide Quantum Dot Nanocrystals" (2005). Dissertations. 1016.
https://scholarworks.wmich.edu/dissertations/1016