qdots

Quantum dots, often abbreviated as QDs or qdots, are nanoscale semiconductor particles that confine electrons and holes in all three spatial dimensions. This quantum confinement produces discrete energy levels, yielding size-tunable optical and electronic properties. Most QDs are a few nanometers in diameter, and their emission color depends on particle size rather than the material alone.

Most qdots are synthesized as colloidal nanocrystals using solution-based chemical methods, enabling scalable production. Common materials include cadmium-based systems such as CdSe/CdS and CdSe/ZnS, as well as cadmium-free alternatives like indium phosphide (InP) and zinc-based shells. Core/shell architectures improve photoluminescence by passivating surface traps and enhancing stability.

Optically, qdots exhibit strong absorption and bright, narrow-band emission with a full width at half maximum often a few tens of meV. The emission color spans the visible to near-infrared, controlled by particle size and composition. They offer high photoluminescence quantum yields and can be tuned post-synthesis through shell growth or surface chemistry.

Applications are diverse: quantum-dot light-emitting diodes (QLEDs) for displays, solar cells and photodetectors, and biological imaging where bright, stable fluorescence enables multiplexed tagging. Integration into devices often relies on ligand exchange, surface passivation, and robust encapsulation to protect against oxygen and moisture.

Challenges include toxicity concerns for cadmium-containing QDs, environmental impact, and long-term stability. Blinking, or intermittent emission, has been observed; strategies such as thick shells and optimized core/shell structures mitigate it. Ongoing research seeks non-toxic materials, scalable manufacturing, and efficient, stable integration into commercial lighting, display, and sensing technologies.