Fedorov Aleksandr S, Visotin Maxim A, Eremkin Egor V, Krasnov Pavel O, Ågren Hans, Polyutov Sergey P
International Research Center of Spectroscopy and Quantum Chemistry - IRC SQC, Siberian Federal University, 660041 Krasnoyarsk, Russia.
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, 660036 Krasnoyarsk, Russia.
Phys Chem Chem Phys. 2022 Aug 17;24(32):19531-19540. doi: 10.1039/d2cp01811j.
Charge-transfer plasmons (CTP) in complexes of metal nanoparticles bridged by conductive molecular linkers are theoretically analysed using a statistic approach. The applied model takes into account the kinetic energy of carriers inside the linkers including its dissipation and the Coulomb energy of the charged nanoparticles. The plasmons are statistically investigated for systems containing a large number of complexes of bridged nanoparticles of realistic sizes generated using a simplified molecular dynamics algorithm, where the geometries of the complexes are dependent on the rate of connection of the linkers with the nanoparticles. As illustrated, the distribution of CTP frequencies in the generated nanoparticle complexes is very inhomogeneous. It has a narrow peak, corresponding to CTP plasmons in dimers, and two broad peaks, corresponding mainly to low and high-frequency oscillations in chains of connected nanoparticles. It is found that in general the plasmon frequencies depend inversely on the value of the complex dipole moment of the plasmon oscillation, where the assumption follows that low-frequency plasmons will be more efficiently excited in an external electromagnetic field. To calculate the CTP energy absorption in this field two model modifications are proposed: a system-external electromagnetic field interaction model and a simplified broadening plasmon peak model where the plasmons are calculated at first without damping and where the delta-shaped oscillation peaks are broadened then due to the damping. It is demonstrated that both modifications lead to a wide and almost monotonic absorption in the IR region for all generated systems containing a large number of bridged nanoparticles due to the presence of a large number of CTPs in this region.
采用统计方法对由导电分子连接体桥接的金属纳米粒子复合物中的电荷转移等离子体激元（CTP）进行了理论分析。所应用的模型考虑了连接体内载流子的动能，包括其耗散以及带电纳米粒子的库仑能。对于包含大量使用简化分子动力学算法生成的实际尺寸的桥接纳米粒子复合物的系统，对等离子体激元进行了统计研究，其中复合物的几何形状取决于连接体与纳米粒子的连接速率。如图所示，所生成的纳米粒子复合物中CTP频率的分布非常不均匀。它有一个窄峰，对应于二聚体中的CTP等离子体激元，还有两个宽峰，主要对应于连接纳米粒子链中的低频和高频振荡。研究发现，一般来说，等离子体激元频率与等离子体振荡的复偶极矩值成反比，由此假设低频等离子体激元在外部电磁场中会更有效地被激发。为了计算该场中CTP的能量吸收，提出了两种模型修正：一种是系统 - 外部电磁场相互作用模型，另一种是简化的展宽等离子体激元峰模型，其中首先在无阻尼的情况下计算等离子体激元，然后由于阻尼使三角形振荡峰展宽。结果表明，由于该区域存在大量CTP，这两种修正对于所有包含大量桥接纳米粒子的生成系统在红外区域都导致了宽且几乎单调的吸收。
