Synthesis and size control via variation of temperature of ZnSe:Fe nanocrystals in a microemulsion assisted hydrothermal system

Abstract

A reverse micelle microemulsion assisted hydrothermal approach has been developed for synthesizing iron (Fe2+) doped ZnSe nanocrystals (NCs). The synthetic process contains a two-step procedure, a chemical reaction between Zn2+ and Se using a reducing agent NaBH4 in a Triton X-100 surfactant contained microemulsion, followed by a hydrothermal treatment. The ZnSe NCs have a well-defined crystallinity and the Fe2+ ions have been effectively incorporated into the ZnSe matrix as shown by the compositional mappings from scanning transmission electron microscope (STEM). As revealed by transmission electron microscope (TEM) and powder X-ray diffraction (XRD), the as-synthesized nanocrystals have a cubic zinc blende ZnSe structure with high purity and homogeneity. The sizes of the as-synthesized ZnSe:Fe NCs can be well controlled by changing temperature in the hydrothermal treatment procedure. If the temperature in the hydrothermal system is set lower, the synthesized NCs can be rendered smaller. The size of the ZnSe NCs can be controlled over a wide range from 3.6 nm to 10.4 nm with the temperature range from 90 °C to 140 °C, respectively. The correlation of NC size versus temperature is nearly linear, which can be used to predict and tune NC sizes. This manuscript reports for the first time that the size of Fe2+ doped ZnSe nanocrystals can be controlled by hydrothermal treatment after synthesis via a microemulsion process. Controlling size of the ZnSe:Fe nanocrystals is critical for developing new sensor materials and mid-infrared laser media in the infrared region based on tunable optical properties of the nanomaterials.