Near-Infrared Surface-Enhanced Raman Scattering on Silver-Coated Porous Silicon Photonic Crystals.

Marko Škrabić,Mile Ivanda,Marijan Gotić,Marin Kosović,Ozren Gamulin,Lara Mikac

doi:10.3390/nano9030421

Abstract

Surface-enhanced Raman scattering (SERS) with near-infrared (NIR) excitation offers a safe way for the detection and study of fragile biomolecules. In this work, we present the possibility of using silver-coated porous silicon photonic crystals as SERS substrates for near-infrared (1064 nm) excitation. Due to the deep penetration of NIR light inside silicon, the fabrication of photonic crystals was necessary to quench the band gap photoluminescence of silicon crystal, which acts as mechanical support for the porous layer. Optimal parameters of the immersion plating process that gave maximum enhancement were found and the activity of SERS substrates was tested using rhodamine 6G and crystal violet dye molecules, yielding significant SERS enhancement for off-resonant conditions. To our knowledge, this is the first time that the 1064 nm NIR laser excitation is used for obtaining the SERS effect on porous silicon as a substrate.

Highlights

Surface-enhanced Raman scattering (SERS) is an exceptionally powerful vibrational spectroscopy technique, which finds wide applications in the identification and structural studies of biological materials and chemical substances [1,2,3]
Since we only considered the performance within the stopband, deviations from the ideal Porous silicon (pSi) RF structure were of no concern
Silver-coated porous silicon photonic crystals as SERS substrates were developed for near-infrared excitation (1064 nm), which is important for the Raman detection and study of fragile biomolecules

Summary

Introduction

Surface-enhanced Raman scattering (SERS) is an exceptionally powerful vibrational spectroscopy technique, which finds wide applications in the identification and structural studies of biological materials and chemical substances [1,2,3]. It has attracted a great deal of scientific interest due to a huge enhancement of the Raman signal from a small number of molecules near or bound to plasmonic surfaces, reaching single-molecule detection [4]. Among the various promising SERS-active substrates [6], it has been shown that non-expensive, easy-to-fabricate, stable in air, uniform, reproducible, and highly sensitive SERS-active substrates can be produced using noble-metal nanoparticles deposited or grown on the porous silicon surface [7,8,9,10,11,12,13].

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