Investigations on the interconnection between chemical reactions and experimental results of Zn-based quantum dots

Zn-based materials (ZnO/ZnS) have multiple uses, such as photo-anode, passivation layer, and sensitizer in quantum dot sensitized solar cells (QDSSCs), sensors, UV light-emitting-diodes, and photocatalytic applications. Several synthesis conditions/parameters are accountable for obtaining desired Zn-based products via wet-chemical synthesis. These parameters collectively influence chemistry within the reaction matrix, following the nucleation-growth process, and are finally reflected in the properties of the synthesized product. Importantly, for pure ZnS and ZnO nanoparticle/quantum dot formation, the role of zinc precursors and capping agents is critical. Furthermore, the solubility of precursor salt and metal-ion/complex ratio is the fundamental criteria for the availability of zinc cations in the solution, which will eventually combine with the sulfur anions. In addition, the capping agent's selection and effect are indispensable as they help stabilize the nanomaterials sterically/electrostatically along with the surface passivation of nanoparticle/quantum dots by mediating the growth. In this perspective, we have studied the role of zinc precursors and capping agents in the chemical reaction mechanism, which formulate ZnS and ZnO, and their effect on the optical, structural, and morphological properties of prepared nanoparticles or quantum dots. The final findings show the limitation of using zinc acetate precursor (formation of mixed-phase). Pure ZnS (using zinc sulfate) and pure ZnO (using zinc chloride) will help us for our potential future work to improve the efficiency of QDSSC by choosing optimized chemicals and synthesis conditions, where ZnO can be used in photoanode; ZnS can act as a passivation layer, photoanode, and sensitizers, solving band offset problem at the interface of electron transport material and as exciton absorber. Eventually, the final compositions, synthesis conditions, and materials establish a base and will help researchers with applications such as solar cells, sensors, LEDs, and bioimaging, based on material properties. ZnS-10H polytype, ZnO quantum dots, and mixed ZnS/ZnO obtained using zinc sulfate, zinc chloride, and zinc acetate as precursors, respectively. Nanoparticles, nanosheets, and nanoflowers were formed by changing zinc precursors and capping agents.