A review on development in synthesis process, characteristics, and biological applications of transition metal dichalcogenides quantum dots

Nowadays, transition-metal dichalcogenides (TMDs) based fluorescent quantum dots (QDs) have gained considerable interest from scientific community because of their potent applications in biological science such as photothermal therapy, bioimaging, and nanomedicine. The intrinsic properties of TMDs QDs, like high brightness, long-lasting optical properties, size-tunability, narrow-range luminescence, surface functionalisation, and emission energies of quantum states, with biocompatibility enhances the biomedical efficacy of TMDs QDs. These properties together make them suitable for biological applications. However, various limiting factors (aggregation, control over QDs, poorly understood surface chemistry, and cytotoxicity, etc.) are associated with the TMDs QDs which hinder their wide application. These challenges must be understood and more rationalised process need to be adopted for the synthesis and to enhance their biocompatibility before they are widely validated. This review provides an overview of TMDs QDs technology dealing with the currently used synthesis approaches (top-down and bottom-up approaches), characterization of physical properties, and applications in biosensors, photothermal therapy, drug delivery, and bioimaging. In addition, the influence of synthesis technique on their distinctive features, such as UV-absorbance, stable fluorescent properties with tunable bio-functionality, toxicity effects, and quantum yield (QY) has been discussed. The existing challenges need to be addressed, and future prospects have been presented in a systematic way.