Cation exchange doping by transition and non-transition metals: embracing luminescence for band gap tunability in a ZnS lattice

When designing sensors for optoelectronic devices, fluorescent materials are always the choice of material chemists. Among the existing fluorescent molecules, the most widely used sensing materials are colloidal nanocrystals, which are classified as quantum dots (QDs). Photoluminescence and tuning of the band gap are the two domains that are explored while engineering optically active crystals. The selection of dopants in a host lattice is the initial step towards achieving the material of choice and designing tailor-made stable materials. Among various QD materials, doped ZnS quantum dots have emerged as a fascinating class, showcasing distinctive characteristics resulting from both transition and non-transition metal doping. This work reviews recent developments in the synthesis, structural characterization, and applications of transition and non-transition metal-doped ZnS quantum dots. Transition metal doping, involving elements such as Mn, Co, and Cu, imparts remarkable photoluminescence properties to QDs, rendering them suitable for optoelectronic devices, such as light-emitting diodes and displays. Non-transition metal doping, involving elements such as Al, Mg, and Ga, facilitates bandgap engineering, paving the way for enhanced light absorption and utilization in photovoltaics and photocatalysis. Transition and non-transition metal-doped ZnS quantum dots exhibit diverse applications across multiple domains. In the field of biomedicine, their biocompatibility, tunable fluorescence, and ability to generate reactive oxygen species under light irradiation present opportunities for cellular imaging and photodynamic therapy. Moreover, their integration into composite materials holds the potential for enhanced electronic and optoelectronic device performance. Challenges in this field include achieving precise control over dopant concentrations, uniformity, and stability, while also addressing scalability issues for large-scale production. Future directions include exploring novel doping strategies, co-doping schemes, and surface functionalization techniques to further enhance the properties of doped ZnS quantum dots. In conclusion, transition and non-transition metal-doped zinc sulphide quantum dots showcase a realm of exciting possibilities for technological innovation. Their unique properties, enabled by judicious dopant incorporation, make them valuable materials for applications spanning optoelectronics, energy conversion, and biomedical sciences. As research in this field advances, these doped quantum dots are poised to significantly contribute to the progression of next-generation technologies.