Khlebtsov Nikolai G, Zarkov Sergey V, Khanadeev Vitaly A, Avetisyan Yuri A
Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences, 13 Prospekt Entuziastov, Saratov 410049, Russia.
Nanoscale. 2020 Oct 14;12(38):19963-19981. doi: 10.1039/d0nr02531c. Epub 2020 Sep 30.
Rational design of AuNST morphology requires adequate computational models. The bulk dielectric function is not applicable to sharp nanostar spikes. We suggest a two-component dielectric function in which the nanostar core is treated as a bulk material, whereas the size-corrected dielectric function of the spikes is treated by a modified Coronado-Schatz model. In addition to the strong broadening of plasmonic peaks, the simulated absorption and scattering spectra show unusual properties, which are not observed with bulk dielectric functions. The effect of NIR water absorption on nanostar spectra is small, and the absorption peak demonstrates the expected small decrease in the absorbing media. Surprisingly, however, water absorption increases the scattering peak by 30%. For the common surfactant-free Vo-Dinh AuNSTs, we report, for the first time, very intense SWIR plasmonic peaks around 1900 nm, in addition to the common strong peak in the UV-vis-NIR band (here, at 1100 nm). For bilayers of AuNSTs in air, we recorded two similarly intense peaks near 800 and 1500 nm. To simulate the experimental extinction spectra of colloids and bilayers on glass in air, we develop a statistical model that includes the major fraction of typical Vo-Dinh AuNSTs and two minor fractions of sea urchins and particles with protrusions. In contrast to the general belief, we show that the common UV-vis-NIR plasmonic peak of surfactant-free AuNSTs is related to short spikes on a spherical core, whereas long spikes produce an intense SWIR plasmonic mode. Such a structural assignment of vis-NIR and SWIR peaks does not seem to have been reported previously for surfactant-free nanostars. With our model, we demonstrate good agreement between simulated and measured spectra of colloids and bilayers on glass in air.
金纳米星形态的合理设计需要适当的计算模型。体介电函数不适用于尖锐的纳米星尖刺。我们提出了一种双组分介电函数，其中纳米星核心被视为体材料，而尖刺的尺寸校正介电函数则通过改进的科罗纳多 - 沙茨模型来处理。除了等离子体峰的强烈展宽外，模拟的吸收和散射光谱还显示出不寻常的特性，而这些特性在体介电函数中并未观察到。近红外水吸收对纳米星光谱的影响很小，吸收峰在吸收介质中呈现出预期的小幅下降。然而，令人惊讶的是，水吸收使散射峰增加了30%。对于常见的无表面活性剂的沃 - 丁氏金纳米星，我们首次报道了除紫外 - 可见 - 近红外波段（此处为1100 nm）的常见强峰外，在1900 nm左右还有非常强烈的短波红外等离子体峰。对于空气中的金纳米星双层膜，我们记录到了在800和1500 nm附近两个强度相似的峰。为了模拟空气中玻璃上胶体和双层膜的实验消光光谱，我们开发了一个统计模型，该模型包括典型的沃 - 丁氏金纳米星的主要部分以及海胆状和有突起颗粒的两个次要部分。与普遍看法相反，我们表明无表面活性剂的金纳米星的常见紫外 - 可见 - 近红外等离子体峰与球形核心上的短尖刺有关，而长尖刺则产生强烈的短波红外等离子体模式。对于无表面活性剂的纳米星，这种可见 - 近红外和短波红外峰的结构归属似乎以前未曾报道过。通过我们的模型，我们证明了模拟的和测量的空气中玻璃上胶体和双层膜光谱之间的良好一致性。
