Nat Mater. 2011 Oct 23;10(12):936-41. doi: 10.1038/nmat3145.
The syntheses of strongly anisotropic nanocrystals with one dimension much smaller than the two others, such as nanoplatelets, are still greatly underdeveloped. Here, we demonstrate the formation of atomically flat quasi-two-dimensional colloidal CdSe, CdS and CdTe nanoplatelets with well-defined thicknesses ranging from 4 to 11 monolayers. These nanoplatelets have the electronic properties of two-dimensional quantum wells formed by molecular beam epitaxy, and their thickness-dependent absorption and emission spectra are described very well within an eight-band Pidgeon-Brown model. They present an extremely narrow emission spectrum with full-width at half-maximum less than 40 meV at room temperature. The radiative fluorescent lifetime measured in CdSe nanoplatelets decreases with temperature, reaching 1 ns at 6 K, two orders of magnitude less than for spherical CdSe nanoparticles. This makes the nanoplatelets the fastest colloidal fluorescent emitters and strongly suggests that they show a giant oscillator strength transition.
具有一个维度远小于另外两个维度的强各向异性纳米晶体的合成，如纳米薄片，仍在很大程度上未得到开发。在这里，我们展示了原子级平坦的准二维胶体 CdSe、CdS 和 CdTe 纳米薄片的形成，其厚度从 4 到 11 单层不等。这些纳米薄片具有由分子束外延形成的二维量子阱的电子特性，其厚度相关的吸收和发射光谱在八带 Pidgeon-Brown 模型中得到了很好的描述。它们呈现出非常窄的发射光谱，在室温下半峰全宽小于 40 毫电子伏特。在 CdSe 纳米薄片中测量的辐射荧光寿命随温度降低而降低，在 6 K 时达到 1 纳秒，比球形 CdSe 纳米粒子低两个数量级。这使得纳米薄片成为最快的胶体荧光发射器，并强烈表明它们表现出巨大的振荡器强度转变。
