In situ dynamic measurements of the enhanced SERS signal using an optoelectrofluidic SERS platform

Abstract

A novel active surface-enhanced Raman scattering (SERS) platform for dynamic on-demand generation of SERS active sites based on optoelectrofluidics is presented in this paper. When a laser source is projected into a sample solution containing metal nanoparticles in an optoelectrofluidic device and an alternating current (ac) electric field is applied, the metal nanoparticles are spontaneously concentrated and assembled within the laser spot, form SERS-active sites, and enhance the Raman signal significantly, allowing dynamic and more sensitive SERS detection. In this simple platform, in which a glass slide-like optoelectrofluidic device is integrated into a conventional SERS detection system, both dynamic concentration of metal nanoparticles and in situ detection of SERS signal are simultaneously possible with only a single laser source. This optoelectrofluidic SERS spectroscopy allows on-demand generation of 'hot spots' at specific regions of interest, and highly sensitive, reliable, and stable SERS measurements of the target molecules in a tiny volume (∼500 nL) of liquid sample without any fluidic components and complicated systems.

Review of microfluidic approaches for surface-enhanced Raman scattering

“…The preconcentration of samples based on the movement of charged molecules along an electric field (electrophoresis) and the physical adsorption of the charged molecules to an oppositely charged electrode as the SERS substrate has effectively improved the sensitivity of detection for a wide range of concentrations without the use of complicated equipment [83]. To realize effective electrokinetic preconcentration, the SERS substrates must be well designed.…”

Optoelectrofluidic Manipulation of Nanoparticles and Biomolecules

“…Such an on-demand formation of nanostructures would be useful for constructing an active SERS platform for detecting chemicals with enhanced Raman scattering signals in a specific area of interest whenever we want. Recently, such an optoelectrofluidic-active SERS platform has been reported [66]. In that study, active generation of SERS substrate by optoelectrofluidic concentration of gold nanoparticles into a specific area of interest and in situ measurement of SERS signals from small molecules around the area has been demonstrated as shown in Figure 5(a).…”

“…Optoelectrofluidic tools for biological and chemical applications. (a) Active surface-enhanced Raman scattering (SERS) substrate for in situ detection of molecules in a specific area at a specific time of interest (Hwang et al[66]-reproduced by permission of The Royal Society of Chemistry). (b) Measurement of molecular diffusion coefficient by analyzing recovery rate after optoelectrofluidic molecular depletion from the illuminated area at a low AC frequency condition (adapted with permission from Hwang and Park[67], Copyright 2009 American Chemical Society).…”

Use of a micro- to nanochannel for the characterization of surface-enhanced Raman spectroscopy signals from unique functionalized nanoparticles

“…However, their device is a complex system that requires an alternating current voltage device to drive it. 24 Chrimes et al 25 used a dielectrophoresis approach to trap nanoparticles by changing the frequency and voltage to force nanoparticles to aggregate at certain locations. While this method does produce many enhancements at the desired locations, this approach requires the user to tune the frequency and voltage depending on the size and composition of the nanoparticle.…”