Dendritic Forest-Like Ag Nanostructures Prepared Using Fluoride-Assisted Galvanic Replacement Reaction for SERS Applications.

Ming-Hua Shiao,Yung-Sheng Lin,Ching-Yi Peng,Hung Ji Huang,Tsunghsueh Wu,Yang-Wei Lin,Ting-Yu Lai

doi:10.3390/nano11061359

Abstract

Dendritic forest-like Ag nanostructures were deposited on a silicon wafer through fluoride-assisted galvanic replacement reaction (FAGRR) in aqueous AgNO3 and buffered oxide etchant. The prepared nanostructures were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma–optical emission spectroscopy, a surface profiler (alpha step), and X-ray diffraction. Additionally, the dendritic forest-like Ag nanostructures were characterized using surface-enhanced Raman scattering (SERS) when a 4-mercaptobenzoic acid (4-MBA) monolayer was adsorbed on the Ag surface. The Ag nanostructures exhibited intense SERS signal from 4-MBA because of their rough surface, and this intense signal led to an intense local electromagnetic field upon electromagnetic excitation. The enhancement factor for 4-MBA molecules adsorbed on the Ag nanostructures was calculated to be 9.18 × 108. Furthermore, common Raman reporters such as rhodamine 6G, 4-aminothiolphenol, 5,5′-dithiobis-2-nitrobenzoic acid, and carboxyfluorescein (FAM) were characterized on these dendritic forest-like Ag nanostructures, leading to the development of an ultrasensitive SERS-based DNA sensor with a limit of detection of 33.5 nM of 15-mer oligonucleotide.

Highlights

Surface-enhanced Raman scattering (SERS) is well known for its high sensitivity toward analytes that adsorb on roughened Au and Ag surfaces [1]
The anisotropic growth of Ag microstructures is attractive because these microstructures possess a rough surface that induces localized surface plasmon resonance when they interact with light and strongly enhance the electromagnetic field in surface-enhanced Raman scattering (SERS) [7,8,9]
The surface morphology and nanostructure of the substrate crucially influence the degree of Raman signal enhancement in SERS, and the dendritic forest-like Ag nanostructures synthesized in this study had distinctive morphology and a rough surface, making them as adequate SERS-active substrates

Summary

Introduction

Surface-enhanced Raman scattering (SERS) is well known for its high sensitivity toward analytes that adsorb on roughened Au and Ag surfaces [1]. Studies have discovered that electromagnetic fields and chemical amelioration enhance the Raman signals of molecules adsorbed on metallic nanostructures with a factor of 102 to 106. Colloidal Ag nanomaterials of various morphology have been widely investigated as highly efficient SERS substrates [4,5,6]. The anisotropic growth of Ag microstructures is attractive because these microstructures possess a rough surface that induces localized surface plasmon resonance when they interact with light and strongly enhance the electromagnetic field in SERS [7,8,9]. The anisotropic growth of Ag microstructures is attractive because these microstructures possess a rough surface that induces localized surface plasmon resonance when they interact with light and strongly enhance the electromagnetic field in SERS [7,8,9]. 4.0/).

Methods

Results

Conclusion