论文标题
NMR证据证明硫醇封闭铂纳米颗粒中的能隙开口的证据
NMR evidence for energy gap opening in thiol-capped platinum nanoparticles
论文作者
论文摘要
当金属的粒径减小时，预计由于量子尺寸效应，能量差距将打开。然而，尚未直接观察到铂金属纳米颗粒中的能量隙（NMR）。为了研究Pt纳米颗粒的电子状态的粒径依赖性，我们在硫醇封闭的Pt纳米颗粒上进行了195pt NMR实验，三个不同的平均直径小于3 nm。对于直径为2.8 nm的纳米颗粒，我们观察到通常的金属行为，其状态密度较小。相比之下，直径小于2.5 nm的纳米颗粒中1/T1T的温度依赖性是一种激活能力形式，是150 K以上的激活 - 能量形式，它是半导体的行为，其能量差距为2000 K的能量差距2000K。1/t1t在1/t1t中的显着降低在1/t1t中的显着下降量在较小的pt nanopart属性中的数量较小的数量均超过两个级数。费米能量与能量差距的打开是一致的。这些结果表明，直径低于2.5 nm的金属 - 绝缘体跃迁存在于我们的硫醇限制的PT纳米颗粒样品中。还讨论了硫醇封盖对实验结果建议的电子结构的影响。
When the particle size of a metal is reduced, it is expected that an energy gap will open due to the quantum size effect. However, the energy gap in platinum (Pt) metal nanoparticles has not been observed directly by nuclear magnetic resonance (NMR). To investigate the particle size dependence of the electronic state of Pt nanoparticles, we performed 195Pt NMR experiments on thiol-capped Pt nanoparticles with three different average diameters of less than 3 nm. For the nanoparticles with a diameter of 2.8 nm, we observed usual metallic behavior with a smaller density of states than that of the bulk Pt. In contrast, the temperature dependence of 1/T1T in nanoparticles less than 2.5 nm in diameter is an activation-energy form above 150 K, which is semiconducting behavior with an energy gap of the order of 2000 K. The significant decrease in 1/T1T by more than two orders of magnitude in the smaller Pt nanoparticles compared to the bulk Pt is attributable to the disappearance of the density of states at the Fermi energy, which is consistent with the opening of an energy gap. These results indicate a metal-insulator transition below 2.5 nm in diameter is present in our thiol-capped Pt nanoparticle samples. The effect of the thiol capping on the electronic structure suggested by the experimental results is also discussed.
