Thermally and photoinduced structural and chemical changes of a silver nanocube array on Au(111).

Takeru Iwahori,Yoichi Uehara,Satoshi Katano,Ayana Mizuno,Atsushi Ono

doi:10.1039/d1ra00830g

Abstract

We have investigated the thermally and photoinduced structural and chemical changes of a polyvinylpyrrolidone (PVP)-covered silver nanocube (AgNC) array on Au(111). The Langmuir–Blodgett (LB) method was utilized to fabricate the highly ordered array of the AgNC monolayer on Au(111). In the Raman spectra obtained at room temperature, sharp vibrational peaks were observed owing to the surface-enhanced Raman scattering (SERS) effect of AgNCs. When AgNCs were annealed, their corners became rounded, followed by their height decrease and lateral expansion. Simultaneously, PVP decomposed into nanocarbons, which were eliminated from the gap between AgNCs. Further annealing AgNCs/Au(111) resulted in obvious decreases in Raman signal intensity and AgNC height due to the sintering of AgNCs. We also confirmed the photochemical transformation of PVP to nanocarbons without the deformation of AgNCs when an intense laser was irradiated on the AgNC surface.

Highlights

Metal nanoparticles (NPs) forming an array on a substrate have been attracting much attention in relation to technological applications such as sensing, optoelectonics and catalyses.[1,2,3] So far, various metals and shapes of NPs have been used to fabricate NP arrays
The AgNC alignment remained unchanged a er annealing, which implies that AgNCs do not diffuse or aggregate at 111 C
In the Raman spectrum obtained at room temperature, sharp peaks assigned to vibrational modes of PVP were observed as a result of the surface-enhanced Raman scattering (SERS) effect of the AgNCs

Summary

Introduction

Metal nanoparticles (NPs) forming an array on a substrate have been attracting much attention in relation to technological applications such as sensing, optoelectonics and catalyses.[1,2,3] So far, various metals and shapes of NPs have been used to fabricate NP arrays. A silver nanocube (AgNC) has drawn much attention since it has a higher electric eld enhancement[25,26,27,28,29,30,31] than and a superior catalytic activity to AgNP of spherical shape.[32,33] Unique nanoscale properties, such as single-molecule detection by the SERS effect,[25] superior catalytic activity on (100) facets[32,33] and plasmonic chemical reactions,[34,35,36] and brightening of an organic light-emitting device,[37] have been realized by utilizing. We used Raman spectroscopy to elucidate the chemical state of PVP before and a er heating and laser irradiation

Experimental method

Results and discussion

Conclusions