Indium phosphide quantum dots: advanced synthesis, surface engineering, and biomedical applications in imaging, sensing, and therapy

Indium phosphide quantum dots (InP QDs) are emerging as non-toxic, tunable, and biocompatible semiconductor nanomaterials with transformative potential in biomedical applications. This review highlights cutting-edge synthesis methods, including nonclassical nucleation and scalable production, alongside innovative surface engineering techniques such as ligand exchange, polymer coatings, and inorganic passivation to overcome challenges like surface defects and indium release. We explore their superior near-infrared (NIR) emission and low cytotoxicity, enabling high-sensitivity NIR bioimaging, resonance energy transfer-based biosensing, photodynamic therapy, drug delivery, and neural prosthetics. Compared to other nanoparticles, InP QDs offer enhanced NIR performance and regulatory compliance, making them economically viable for diagnostics and therapeutics. By addressing safety concerns through advanced shell designs and safer precursors, InP QDs pave the way for clinical translation. This review, with a focused emphasis on the biomedical translation of InP QDs, provides a structured roadmap for researchers and clinicians to harness their potential in next-generation healthcare solutions.