Sato Keiichi, Kojima Satoshi, Hattori Shinya, Chiba Taeko, Ueda-Sarson Keiko, Torimoto Tsukasa, Tachibana Yasuhiro, Kuwabata Susumu
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamada-oka, Suita, Osaka 565-0871, Japan. Life Science Research Center, Hitachi Software Engineering Co. Ltd, 1-1-43 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
Nanotechnology. 2007 Nov 21;18(46):465702. doi: 10.1088/0957-4484/18/46/465702. Epub 2007 Oct 12.
Photoluminescence enhancement, photoetching and photostability of CdS nanocrystals were investigated under light irradiation. Strongly photoluminescent nanocrystals were obtained when the nanocrystal was weakly photoexcited in an aqueous solution at pH = 11 in the presence of oxygen. With the support of XPS measurements, the following photoactivation mechanism is proposed: Cd(2+) ions are released from the CdS surface owing to slow photocorrosion in the presence of oxygen, and Cd-OH bond formation occurs on the CdS surface under the alkaline conditions, removing the surface trap states. The wavelength of the irradiating light and the pH of the solution were determined as key parameters for nanocrystal surface modification. For the stability measurements the nanocrystals were extracted with an ammonium salt in a non-polar solvent. The photoluminescence quantum yield for the nanocrystals in the non-polar phase reached approximately 30%. The extracted nanocrystals were remarkably stable even under UV light irradiation, and the photoluminescence intensity was maintained for several months.
研究了CdS纳米晶体在光照下的光致发光增强、光蚀刻和光稳定性。当纳米晶体在pH = 11的水溶液中、有氧存在的情况下受到弱光激发时，可获得强发光纳米晶体。在XPS测量的支持下，提出了以下光活化机制：由于在有氧存在的情况下发生缓慢的光腐蚀，Cd(2+)离子从CdS表面释放出来，并且在碱性条件下CdS表面形成Cd-OH键，从而消除了表面陷阱态。确定了照射光的波长和溶液的pH值为纳米晶体表面改性的关键参数。为了进行稳定性测量，纳米晶体用铵盐在非极性溶剂中萃取。非极性相中纳米晶体的光致发光量子产率达到约30%。即使在紫外光照射下，萃取的纳米晶体也非常稳定，并且光致发光强度可维持数月。
