Dl‐Aspartic Acid‐Mediated Hydrothermal Synthesis of β‐ZnS Microspheres and Their Optical Properties

Abstract

AbstractZnS hollow microspheres were synthesized by a dl‐aspartic acid mediated hydrothermal route. dl‐aspartic acid plays an important role as crystal growth soft template, which regulates the release of Zn2+ ions for the formation of ZnS hollow spheres. The formation of these hollow spheres was mainly attributed to an Ostwald ripening process. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), electron diffraction (ED), UV/Vis spectroscopy (UV), and photoluminescence (PL). The shells of the microspheres were composed of ZnS quantum dots (QDs) with the average size of 2.31 nm. The average microspheres diameter is 0.5–3.5 μm. The shell thickness of the hollow sphere is ≈︁300 nm. The optical bandgap energy increased significantly compared to the bulk ZnS material due to the strong quantum confinement effect. Two strong emissions at ≈︁425 nm and ≈︁472 nm in the photoluminescence (PL) spectrum of ZnS hollow microspheres indicate strong quantum confinement because of the presence of QDs.