We conducted ${}^{195}\mathrm{Pt}$-NMR measurements on various-diameter Pt nanoparticles coated with polyvinylpyrrolidone in order to detect the quantum size effect and the discrete energy levels in the electron density of states, both of which were predicted by Kubo more than 50 years ago. We succeeded in separating the signals arising from the surface and interior regions and found that the nuclear spin-lattice relaxation rates in both regions show the metallic behavior at high temperatures. Surprisingly, the magnetic fluctuations in both regions exhibited anomalous behavior below the same temperature $T^{*}$, which points to a clear size dependence and is well scaled with ${\delta }_{\mathrm{Kubo}}$. These results suggest that a size-tunable metal-insulator transition occurs in the Pt nanoparticles as a result of the quantum size effect.

中文翻译：

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基于核磁共振的间隙行为与量子尺寸效应有关

我们进行了 ${}^{195}铂$为了检测量子尺寸效应和状态电子密度中的离散能级，对50年前的久保预测了涂覆聚乙烯吡咯烷酮的各种直径Pt纳米粒子的NMR测量。我们成功地分离了从表面和内部区域产生的信号，发现两个区域的核自旋晶格弛豫速率均显示出高温下的金属行为。令人惊讶的是，在相同温度下，两个区域的磁涨落均表现出异常行为${Ť}^{*}$，这表明存在明显的大小依赖性，并且可以很好地缩放 ${\delta }_{\mathrm{久保}}$。这些结果表明，由于量子尺寸效应，在Pt纳米颗粒中发生了尺寸可调的金属-绝缘体转变。