Tuning of the fluorescence wavelength of CdTe quantum dots with 2 nm resolution by size-selective photoetching.
Photoetching of CdTe nanocrystals was applied to thiol-capped CdTe quantum dots (QDs) to control their fluorescence wavelength. CdTe QDs with a high quantum yield (49%) were synthesized in aqueous solution, and they were successfully photoetched in strong alkaline (pH = 13.5) conditions. When monochromatic light was used, size-selective photoetching could be conducted; the photoetching proceeded until the band gap energy of the CdTe QDs increased to the energy corresponding to the wavelength of the irradiating light. As a result, a good linear relationship was obtained between the wavelength of the irradiating light and that of the fluorescence peak. The resulting CdTe QDs exhibited a fluorescence peak with an FWHM value as small as 23.5 nm, indicating preparation of highly monodispersed nanocrystals. The high quantum yield (ca. 45%) was maintained after the photoetching. Very fine tuning of the fluorescence wavelength with 2 nm resolution was achieved by changing the wavelength of the irradiating light by 2 nm. Theoretical calculation of the quantum size effects (effective mass approximation) predicts that a difference in the band gap fluorescence wavelength of 2 nm corresponds to a change in particle diameter of ca. 0.02 nm.
Uematsu
T
T
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.
Kitajima
H
H
Kohma
T
T
Torimoto
T
T
Tachibana
Y
Y
Kuwabata
S
S
D019187:Cadmium Compounds / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D010777:Photochemistry / Q000379:methods*; D045663:Quantum Dots; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013499:Surface Properties; D013691:Tellurium / Q000737:chemistry*
D019187:Cadmium Compounds; D046911:Macromolecular Substances; D013691:Tellurium; C028337:cadmium telluride