A study on the correlation between the dewetting temperature of Ag film and SERS intensity

Jiamin Quan,Yong Zhu,Jie Zhang,Ning Wang,Xueqiang Qi,Junying Li

doi:10.1038/s41598-017-15372-y

Jiamin Quan, Yong Zhu + Show 4 more

Open Access

https://doi.org/10.1038/s41598-017-15372-y

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Abstract

The thermally dewetted metal nano-islands have been actively investigated as cost-effective SERS-active substrates with a large area, good reproducibility and repeatability via simple fabrication process. However, the correlation between the dewetting temperature of metal film and SERS intensity hasn’t been systematically studied. In this work, taking Ag nano-islands (AgNIs) as an example, we reported a strategy to investigate the correlation between the dewetting temperature of metal film and SERS intensity. We described the morphology evolution of AgNIs on the SiO2 planar substrate in different temperatures and got the quantitative information in surface-limited diffusion process (SLDP) as a function of annealing temperature via classical mean-field nucleation theory. Those functions were further used in the simulation of electromagnetic field to obtain the correlation between the dewetting temperature of Ag film and theoretical analysis. In addition, Raman mapping was done on samples annealed at different temperatures, with R6G as an analyte, to accomplish the analysis of the correlation between the dewetting temperature of Ag film and SERS intensity, which is consistent with the theoretical analysis. For SLDP, we used the morphological characterization of five samples prepared by different annealing temperatures to successfully illustrate the change in SERS intensity with the temperature fluctuation, obtaining a small deviation between the experimental results and theoretic prediction.

Highlights

Surface-enhanced Raman spectroscopy (SERS) as a powerful analytical technique for ultrasensitive chemical or biochemical analysis has gained much attention since its discovery 40 years ago, because it can produce several orders of magnitude enhancement in Raman signals[1,2]
We have demonstrated a strategy for investigating the correlation between the dewetting temperature of Ag film and SERS intensity
We used a small amount of samples prepared by different dewetting temperatures to get the quantitative information about the morphology evolution of Ag nano-islands (AgNIs) as a function of the annealing temperature in surface-limited diffusion process (SLDP)

Summary

Introduction

Surface-enhanced Raman spectroscopy (SERS) as a powerful analytical technique for ultrasensitive chemical or biochemical analysis has gained much attention since its discovery 40 years ago, because it can produce several orders of magnitude enhancement in Raman signals[1,2]. By controlling the shape (surface morphology), size, and the spacing between nanoparticles, we can tune the LSPR to obtain an optimized SERS signal from the metal nanostructures at the target wavelength. Among those factors, the surface morphology and the inter–particle spacing are important. The mean diameter, mean surface-to-surface spacing and contact angle of the thermally dewetted AgNIs were quantified as a function of the annealing temperature T via the classical mean-filed nucleation theory, based on the image analysis of scanning electron microscopy (SEM) of AgNIs in SLDP These functions were brought into the COMSOL Multiphysics to obtain the correlation between LSPR effect and the dewetting temperature. Using the R6G as the probe molecule to conduct SERS measurements, we found there was a good consistency between the simulation and experimental results

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