Comparison of hot carrier generation between self-assembled gold and silver nanoparticle arrays tailored to the same hybrid plasmon resonance

Abstract

We evaluated the properties of hot carrier generation on Au and Ag nanoparticle (NP) 2D arrays by monitoring chemical transformation. The arrays were fabricated by assembling the Au and AgNPs, respectively, with a diameter of ∼30 nm. The plasmon resonance peaks of both the arrays were tuned to around 671 nm, where the intraband transition was the dominant pathway for the surface plasmon excitation since the incident photon energy is below the interband transition threshold for both Au and Ag. Time-resolved surface-enhanced Raman scattering (SERS) spectroscopy was utilized to monitor the changes in the molecular structure sensitively. We selected para-aminothiophenol as the molecule, which was well known to transform to 4,4′-dimercaptoazobenzene (DMAB) by hot carriers generated from the plasmonic excited surface. It was observed that the peak intensity of DMAB increased as the total exposure increased due to the increase in the number of DMAB molecules for both metals, similar to our previous reports. The analysis of the SERS spectra showed that larger laser intensity progressed the transformation more rapidly. The analysis also clarified that the chemical transformation occurs more efficiently on the AgNP array compared to the AuNP array. The superiority in the efficiency for Ag may be derived from contribution of more hot carriers generated in the material with the smaller plasmon damping constant.

Investigating Plasmonic Catalysis Kinetics on Hot-Spot Engineered Nanoantennae

“…Hence, a systematic study with tangible parameters at a single-particle level is required . Namely, surface enhanced Raman spectroscopy (SERS) is one of the most powerful tools for systematic investigation on hot-electron meditated catalysis because SERS information allows direct phenomenological observation on hot-carrier dynamics by tracing the photocatalytic reactions real-time. − Yet, low signal-to-noise ratio in single-particle SERS measurements remains a bottleneck. It is well-known that SERS intensities are proportional to the square of the local-field intensity and number of the observed molecules.…”

Insights into Plasmon-Induced Dimerization of Rhodanine–A Surface-Enhanced Raman Scattering Study

“…59,66 The increased efficiency of AgNP in the chemical transformation of the adsorbate occurred due to the generation of more hot carriers on the metal surface under resonance excitation, in addition to its lower damping constant. 104 These observations clearly suggest that the dimerization reaction of Rd on AgNP/AuNP is assisted by LSPR. Thus, we have explored the reaction pathway and the most probable excitation mechanism involved in the plasmon-induced dimerization of Rd.…”

“…Previous SERS studies on Rd did not discuss the details about the role of plasmon and excitation mechanisms involved in the dimerization of Rd. If the plasmon-induced dimerization of Rd occurred through the transfer of hot electrons (details mentioned below), the SERS spectra are expected to change with excitation wavelengths as it is known that the hot carrier generation is affected by the excitation wavelength, the size of nanoparticles, and the nature of the metal. ,− The nature of the metal is an important factor because the hot carrier is generated via plasmon damping, whose rate is determined by the damping constant of the metal . A smaller plasmon damping constant will have more rate, and silver is supposed to have a smaller damping constant than gold .…”

“…66,103−105 The nature of the metal is an important factor because the hot carrier is generated via plasmon damping, whose rate is determined by the damping constant of the metal. 104 A smaller plasmon damping constant will have more rate, and silver is supposed to have a smaller damping constant than gold. 104 It is also expected that the electron transfer efficiency would increase with the incident photon energy, as higher energy would generate more electrons with enough energy and also optimum efficiency may be achieved when incident energy is in resonance with the LSPR of the MNP.…”

“…104 A smaller plasmon damping constant will have more rate, and silver is supposed to have a smaller damping constant than gold. 104 It is also expected that the electron transfer efficiency would increase with the incident photon energy, as higher energy would generate more electrons with enough energy and also optimum efficiency may be achieved when incident energy is in resonance with the LSPR of the MNP. 106 With the aim to understand the role of the plasmon and excitation mechanism involved in the Rd dimerization, further investigations of the SERS spectra of Rd adsorbed on AgNP and AuNP were carried out using 632.8 nm excitation.…”