Uematsu T, Kitajima H, Kohma T, Torimoto T, Tachibana Y, Kuwabata S
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.
Nanotechnology. 2009 May 27;20(21):215302. doi: 10.1088/0957-4484/20/21/215302. Epub 2009 May 5.
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.
将碲化镉（CdTe）纳米晶体的光刻技术应用于硫醇封端的碲化镉量子点（QDs），以控制其荧光波长。在水溶液中合成了具有高量子产率（49%）的碲化镉量子点，并在强碱性（pH = 13.5）条件下成功地对其进行了光刻。当使用单色光时，可以进行尺寸选择性光刻；光刻过程一直持续到碲化镉量子点的带隙能量增加到与照射光波长对应的能量。结果，照射光波长与荧光峰波长之间获得了良好的线性关系。所得的碲化镉量子点表现出半高宽（FWHM）值低至23.5 nm的荧光峰，表明制备出了高度单分散的纳米晶体。光刻后量子产率仍保持在较高水平（约45%）。通过将照射光波长改变2 nm，实现了分辨率为2 nm的荧光波长的精细调谐。量子尺寸效应的理论计算（有效质量近似）预测，带隙荧光波长2 nm的差异对应于粒径约0.02 nm的变化。
