Silver-Based SERS Pico-Molar Adenine Sensor.

Yonhua Tzeng,Bo-Yi Lin

doi:10.3390/bios10090122

Abstract

Adenine is an important molecule for biomedical and agricultural research and applications. The detection of low concentration adenine molecules is thus desirable. Surface-enhanced Raman scattering (SERS) is a promising label-free detection and fingerprinting technique for molecules of significance. A novel SERS sensor made of clusters of silver nanostructures deposited on copper bumps in valleys of an etched silicon substrate was previously reported to exhibit a low and reproducible detection limit for a 10−11 M neutral adenine aqueous solution. Reflection of laser illumination from the silicon surface surrounding a valley provides additional directions of laser excitation to adenine molecules adsorbing on a silver surface for the generation of enhanced SERS signal strength leading to a low detection limit. This paper further reports a concentration dependent shift of the ring-breathing mode SERS adenine peak towards 760 cm−1 with decreasing concentration and its pH-dependent SERS signal strength. For applications, where the pH value can vary, reproducible detection of 10−12 M adenine in a pH 9 aqueous solution is feasible, making the novel SERS structure a desirable pico-molar adenine sensor.

Highlights

Adenine is one of aromatic bases of DNA and RNA
We reported a novel means of graphene islands masked selective chemical plating technique for the depositing silver nanocrystals on copper [8,9]
The orientation in which an adenine molecule adsorbs on silver varies depending on the interactive mechanism between adenine and silver

Summary

Introduction

Adenine is one of aromatic bases of DNA and RNA. Active interactions of adenine with silverand gold-based sensors result in favorable surface enhanced Raman scattering (SERS) signal strength.SERS can detect adenine in a low-concentration aqueous solution, which regular Raman scattering technique cannot. Active interactions of adenine with silverand gold-based sensors result in favorable surface enhanced Raman scattering (SERS) signal strength. Adenine molecules must adsorb on a SERS sensor with very high plasmonic coupling induced local electromagnetic fields. An exciting laser beam causes electrons in a metal nanostructure to drift in resonance to the incident electromagnetic fields. High-concentration negative and positive charges accumulate on two closely spaced counter metal surfaces. These charges induce much stronger electromagnetic fields than that of the incident laser beam. Molecules which adsorb on counter surfaces in a nanoscale gap are subjected to much stronger excitation than the laser beam alone and generate strong SERS signal strength for detection by a spectrometer [1,2]

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Conclusion