To improve the quantum yield and decrease the toxicity of quantum dots for potential applications in biomedicine, several modifications can be made to their synthesis methods:1. Choice of materials: Opt for less toxic materials, such as indium phosphide InP , zinc selenide ZnSe , or silicon Si , instead of the commonly used cadmium-based quantum dots e.g., CdSe, CdTe , which are known for their toxicity.2. Surface modification: Modify the surface of quantum dots with biocompatible ligands or coatings, such as polyethylene glycol PEG , amphiphilic polymers, or biomolecules like peptides and proteins. This can help reduce toxicity and improve their stability in biological environments.3. Controlled synthesis: Employ controlled synthesis methods, such as the hot-injection technique or the microwave-assisted synthesis, to achieve better control over the size, shape, and composition of quantum dots. This can lead to higher quantum yields and reduced toxicity due to fewer defects and impurities.4. Core-shell structures: Create core-shell quantum dots, where a less toxic material forms the core and a higher bandgap material forms the shell e.g., CdSe/ZnS, InP/ZnS . The shell can help passivate the surface defects, improve quantum yield, and reduce the release of toxic ions from the core.5. Doping: Introduce dopants into the quantum dots to modify their electronic properties and improve their quantum yield. For example, manganese Mn doping in ZnSe quantum dots can enhance their photoluminescence efficiency.6. Size control: Synthesize quantum dots with a narrow size distribution, as smaller quantum dots generally exhibit higher quantum yields. This can be achieved by optimizing the reaction conditions, such as temperature, precursor concentration, and reaction time.7. Purification: Implement rigorous purification steps to remove any unreacted precursors, byproducts, or impurities that could contribute to toxicity or lower quantum yields. Techniques like size-exclusion chromatography, ultracentrifugation, or dialysis can be used for purification.8. Post-synthesis treatments: Perform post-synthesis treatments, such as annealing or surface passivation, to reduce surface defects and improve the quantum yield of quantum dots.By incorporating these modifications into the synthesis methods of quantum dots, it is possible to enhance their quantum yield and decrease their toxicity, making them more suitable for applications in biomedicine.