Yu Kui, Zaman Badruz, Singh Shanti, Dashan Wang, Ripmeester John A
Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario K1A OR6, Canada.
J Nanosci Nanotechnol. 2005 Apr;5(4):659-68. doi: 10.1166/jnn.2005.122.
This manuscript reports the ready synthesis of high-quality colloidal CdSe nanocrystals from tri-n-octylphosphine (TOP) and reports the optical properties of the resulting CdSe dispersed in nonpolar and polar environments. With cadmium oxide (CdO) as the Cd precursor and TOPSe as the Se source, the CdSe nanocrystals were synthesized in a reaction medium consisting of TOP. The synthetic approach is as simple as: the swift injection of a TOPSe/TOP solution into a CdO/TOP solution at one particular (high) temperature, with subsequent growth at a lower temperature. The temporal evolution of the optical properties, including absorption and luminescence, were monitored in detail. The photoluminescence (PL) properties of the TOP-capped CdSe investigated comprise the intensity, emission peak wavelength, full width at half maximum of the PL spectra, and stability; these PL properties are sensitive to the history of growth as well as the environment of dispersion. An appropriate parameter, termed "Sensitivity Index (SI)," is proposed to define the percent difference in the PL intensity that arises when the dots are dispersed in non-polar hexane (Hex) as compared to polar tetrahydrofuran (THF). The decrease in the PL efficiency on going from Hex to THF is attributed to changes in surface states rather than in the internal core as more ligands are removed in THF. Dilution experiments further confirm the suggestion of the ligand removal mechanism and provide a conceptual estimate of surface quality via the SI parameter. Due to a slow growth in size (the size of the nanocrystals is almost constant during early 20 min) and good PL stability (tested as PL changes after storage for days both in dispersed or solid states, as well as after UV-irradiation), we suggest that our synthetic approach is likely to be practical for large-scale CdSe nanocrystals with good PL stability.
本手稿报道了由三正辛基膦（TOP）简便合成高质量胶体硒化镉（CdSe）纳米晶体的方法，并报道了所得CdSe在非极性和极性环境中的光学性质。以氧化镉（CdO）作为镉前驱体，以TOPSe作为硒源，在由TOP组成的反应介质中合成了CdSe纳米晶体。合成方法很简单：在一个特定的（高）温度下，将TOPSe/TOP溶液快速注入CdO/TOP溶液中，随后在较低温度下生长。详细监测了包括吸收和发光在内的光学性质随时间的演变。所研究的TOP包覆的CdSe的光致发光（PL）性质包括PL光谱的强度、发射峰波长、半高宽和稳定性；这些PL性质对生长历史以及分散环境敏感。提出了一个合适的参数，称为“灵敏度指数（SI）”，以定义当量子点分散在非极性己烷（Hex）中与极性四氢呋喃（THF）中时PL强度的百分比差异。从Hex到THF时PL效率的降低归因于表面态的变化，而不是内部核的变化，因为在THF中更多的配体被去除。稀释实验进一步证实了配体去除机制的建议，并通过SI参数提供了表面质量的概念估计。由于尺寸增长缓慢（纳米晶体的尺寸在最初20分钟内几乎保持不变）以及良好的PL稳定性（在分散或固态下储存数天以及紫外线照射后通过PL变化进行测试），我们认为我们的合成方法对于具有良好PL稳定性的大规模CdSe纳米晶体可能具有实用性。
