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.