What is a quantum dot?

A quantum dot is accurately described as a small cluster of atoms that typically range between 2 and 10 nanometers in size. These nanoscale semiconductor particles exhibit unique electronic and optical properties due to quantum confinement effects, which arise because of their small dimensions. This size allows the quantum dots to have distinct energy levels and absorption/emission characteristics that depend on their size and shape, enabling a wide range of applications in areas such as photovoltaics, LED technologies, and biological imaging.

The other options highlight concepts that do not accurately describe quantum dots. The mention of self-repairing materials relates to a different field of material science that focuses on smart materials, while imaging surfaces at the atomic level pertains to techniques like scanning tunneling microscopy, not quantum dots specifically. Lastly, invoking infectious organisms deviates entirely from the context of nanotechnology and quantum materials.