Fe:ZnSe semiconductor nanocrystals: Synthesis, surface capping, and optical properties

Water-soluble Fe-doped ZnSe (Fe:ZnSe) nanocrystals (NCs) were synthesized by aqueous synthesis approach using thioglycolic acid (TGA) as capping agent. The undoped ZnSe and Fe:ZnSe NCs were well retained in the zinc blende structure, and the Fe dopants were well doped into the ZnSe NCs, as confirmed by X-ray photoelectron spectroscopy (XPS). The lattice constant of Fe:ZnSe NCs decreases slightly by the introduction of Fe, and Fe:ZnSe NCs exhibit a uniform size distribution with average grain size of ∼5 nm. The thioglycolic acid (TGA) was successfully capped on the surface of Fe:ZnSe NCs, confirmed by Fourier-transform-infrared (FT-IR) spectroscopy. The absorption edges of pure ZnSe and Fe:ZnSe NCs are blue-shifted compared to that of corresponding bulk ZnSe, indicating the quantum confinement effect, and the absorption edge of Fe:ZnSe NCs shows a slightly red shift with respect to the pure ZnSe NCs. The as-prepared Fe:ZnSe NCs exhibits an emission peak at ∼425 nm, and the photoluminescence (PL) intensity of the NCs has the maximum value when the Fe-doping concentration reaches 1.0 at%. It is of interest to note that the concentration quenching effect appears when the Fe-doping concentration is larger than 10.0 at%, and the underlying physical mechanisms were discussed.

Research highlights▶ Highly luminescent and water-soluble Fe:ZnSe semiconductor nanocrystals. ▶ Surface capping and optical properties of Fe:ZnSe semiconductor nanocrystals. ▶ Concentration quenching appears when Fe-doping concentration is larger than 10.0 at%.