A review on quantum dots and their applications

Quantum dots (QDs) are nanosized semiconductor crystals with unique chemical and physical properties, enabling them to emit bright, photobleaching-resistant light. They are classified into three categories: core type QDs, core-shell QDs, and alloyed QDs. Core-type QDs are composed of a single substance, while core-shell QDs have a semiconductor core surrounded by a shell of another semiconductor material. Alloyed QDs are manufactured using high-temperature or wet-chemical processes, while silicon-based QDs display unusual optical and electrical features due to quantum confinement forces. QDs have exceptional optoelectronic capabilities, producing photoluminescence quantum yields of up to 90%. They are useful for various applications, including optoelectronics and photocatalysis. There are three main types of QDs: colloidal, magnetic, and fluorescent. Colloidal synthesis is a widely used technique for creating QDs, offering applications in visible and near-infrared wavelengths. Magnetic QDs display unique magnetic characteristics and can be synthesized using various methods. Fluorescent QDs have high fluorescence quantum yields and are resistant to photobleaching, making them useful in imaging, sensing, and therapies. QDs are being developed to enhance biological imaging capabilities by increasing cellular uptake, reducing toxicity, and enhancing stability. They can be used for intracellular imaging, deep tissue imaging, single-molecule tracking, super-resolution imaging, targeting ligands, selective imaging of mitochondria, pH-responsive fluorescence, responding to specific cellular signals, and self-illuminating systems. However, they have limitations such as toxicity, structural instability, and deterioration due to UV light or aquatic environments.