Jian Chao-Chao, Zhang Jianqi, Ma Xiangchao
School of Physics and Optoelectronic Engineering, Xidian University Xi'an 710071 China
RSC Adv. 2020 Apr 1;10(22):13277-13285. doi: 10.1039/d0ra01474e. eCollection 2020 Mar 30.
Efficient generation of high-energy hot carriers from the localized surface plasmon resonance (LSPR) of noble metal (Ag, Au and Cu) nanoparticles is fundamental to many applications based on LSPR, such as photovoltaics and photocatalysis. Theoretically, intra- and inter-band electron transitions in metal nanoparticles are two important channels for the non-radiative decay of LSPR, which determine the generation rate and energy of hot carriers. Therefore, on the basis of first-principles calculations and Drude theory, in this work we explore the potential role of alloying Ag with Cu in modulating the generation rate and energy of hot carriers by studying the intra- and inter-band electron transitions in Cu, Ag and Cu-Ag alloys. It is meaningful to find that the d-sp inter-band electron transition rates are notably increased in Cu-Ag alloys. In particular, the inter-band electron transition rates of CuAg become larger than that of single Cu and Ag across the whole energy range between 1.5 and 3.2 eV. In contrast, intra-band electron transition rates of Cu-Ag alloys become smaller than that of single Cu and Ag. Because the intra-band electron transitions mainly contribute to the resistive loss in metals, which finally results in a thermal effect rather than high-energy hot carriers, the reduction of intra-band electron transitions in Cu-Ag alloy is beneficial for the transforming the energy absorbed by LSPR into high-energy hot carriers through other non-radiative channels. These results indicate that alloying of Ag and Cu can effectively improve the generation rates of high-energy hot carriers through the inter-band electron transition, but decrease the resistive loss through intra-band transition of electrons, which should be used as a guide in optimizing the non-radiative decay processes of LSPR.
从贵金属（银、金和铜）纳米颗粒的局域表面等离子体共振（LSPR）高效产生高能热载流子是许多基于LSPR的应用（如光伏和光催化）的基础。从理论上讲，金属纳米颗粒中的带内和带间电子跃迁是LSPR非辐射衰减的两个重要通道，它们决定了热载流子的产生速率和能量。因此，基于第一性原理计算和德鲁德理论，在这项工作中，我们通过研究铜、银和铜 - 银合金中的带内和带间电子跃迁，探索将银与铜合金化在调节热载流子产生速率和能量方面的潜在作用。发现铜 - 银合金中的d - sp带间电子跃迁速率显著增加是有意义的。特别是，在1.5至3.2 eV的整个能量范围内，CuAg的带间电子跃迁速率大于单一的铜和银。相比之下，铜 - 银合金的带内电子跃迁速率小于单一的铜和银。由于带内电子跃迁主要导致金属中的电阻损耗，最终产生热效应而非高能热载流子，铜 - 银合金中带内电子跃迁的减少有利于通过其他非辐射通道将LSPR吸收的能量转化为高能热载流子。这些结果表明，银和铜的合金化可以通过带间电子跃迁有效提高高能热载流子的产生速率，但通过电子的带内跃迁降低电阻损耗，这应作为优化LSPR非辐射衰减过程的指导。
