量子点Quantum dot

当晶体尺寸小于该材料的激子玻尔半径（CdSe 约 5.6 nm）时，电子和空穴的运动被限制，连续的能带变为分立的能级，类似“人造原子”。按布鲁斯方程，禁带宽度约增加 ħ²π²/(2R²)·(1/m_e + 1/m_h)。因此同一种材料只要控制粒径，就能发出从蓝到红的各种颜色光。量子点吸收谱宽、发射谱窄、量子产率高、光稳定性好。

When a crystal is smaller than the material's exciton Bohr radius (about 5.6 nm for CdSe), electron and hole motion is confined and continuous bands become discrete levels, like an 'artificial atom'. By the Brus equation the band gap increases by roughly ħ²π²/(2R²)·(1/m_e + 1/m_h). A single material can therefore emit any colour from blue to red simply by controlling particle size. Quantum dots absorb broadly, emit narrowly, have high quantum yields and resist photobleaching.

1981 年苏联的叶基莫夫在玻璃中发现 CuCl 纳米晶的颜色随尺寸变化；1983 年贝尔实验室的布鲁斯在胶体溶液中观察到 CdS 纳米颗粒的尺寸效应并给出理论解释。1993 年麻省理工学院的巴汶迪发展了热注射法，可合成尺寸均一、高质量的 CdSe 量子点。三人共获 2023 年诺贝尔化学奖。

In 1981 Alexei Ekimov in the Soviet Union found that the colour of CuCl nanocrystals in glass changed with size, and in 1983 Louis Brus at Bell Labs observed and explained size effects in colloidal CdS nanoparticles. In 1993 Moungi Bawendi at MIT developed the hot-injection method, making high-quality CdSe quantum dots of uniform size. The three shared the 2023 Nobel Prize in Chemistry.

量子点用于 QLED 电视和显示器的色彩增强膜，可显著扩大色域；也用于生物荧光标记和成像、太阳能电池、光电探测器、单光子源和光催化。由于镉的毒性，无镉量子点（InP、CuInS₂、钙钛矿量子点和碳量子点）正在发展。

Quantum dots are used in colour-enhancement films for QLED televisions and monitors, greatly widening the colour gamut, and in fluorescent biological labelling and imaging, solar cells, photodetectors, single-photon sources and photocatalysis. Because cadmium is toxic, cadmium-free dots (InP, CuInS₂, perovskite and carbon dots) are being developed.