Quantum Dots

Incorporating nanocrystals into future electronic or optoelectronic devices will require a means of controlling charge-injection processes and an understanding of how the injected charges affect the properties of nanocrystals. We show that the optical properties of colloidal semiconductor nanocrystal quantum dots can be tuned by an electrochemical potential. The injection of electrons into the quantum-conÞned states of the nanocrystal leads to an electrochromic re-sponse, including a strong, size-tunable, midinfrared absorption corresponding to an intraband transition, a bleach of the visible interband exciton transitions, and a quench of the narrow band-edge photoluminescence. Nanometer-scale materials promise to be important in the development of next-gen-eration electronic and optoelectronic devic-es. Colloidal semiconductor nanocrystals are particularly attractive (1–3) because their color is directly determined by thei