Synthesis and photoluminescent properties of doped ZnS nanocrystals capped by poly(vinylpyrrolidone)

Abstract

Zinc sulfide semiconductor nanocrystals doped with selected transition metal ions (Mn 2+, Cu 2+, and Ni 2+) have been synthesized via a solution-based method utilizing low dopant concentrations (0–1%) and employing poly(vinylpyrrolidone) (PVP) as a capping agent. UV/Vis absorbance spectra for all of the synthesized nanocrystals show an exitonic peak at around 310 nm, indicating that the introduction of the dopant does not influence the particle size. Calculated particle sizes for undoped and doped nanocrystals are in the 4.3 nm size range. Photoluminescence spectra recorded for undoped ZnS nanocrystals, using an excitation wavelength of 310 nm, exhibit an emission peak centered at around 460 nm. When a dopant ion is included in the synthesis, peaks in the corresponding photoluminescence spectra are red-shifted. For Mn-doped nanocrystals, an intense peak centered at approximately 590 nm is found and is seen to increase in photoluminescence intensity with an increase in dopant concentration. In contrast, for Cu-doped and Ni-doped nanocrystals, weaker peaks centered at around 520 and 500 nm, respectively, are observed and are noticed to decrease in photoluminescence intensity with an increase in dopant concentration. These results clearly show that careful control of synthetic conditions must be employed in the synthesis of doped semiconductor nanocrystals in order to obtain materials with optimized properties.