Novel Bottom‐Up SERS Substrates for Quantitative and Parallelized Analytics

Abstract

Surface-enhanced Raman spectroscopy (SERS) is an emerging technology in the field of analytics. Due to the high sensitivity in connection with specific Raman molecular fingerprint information SERS can be used in a variety of analytical, bioanalytical, and biosensing applications. However, for the SERS effect substrates with metal nanostructures are needed. The broad application of this technology is greatly hampered by the lack of reliable and reproducible substrates. Usually the activity of a given substrate has to be determined by time-consuming experiments such as calibration or ultramicroscopic studies. To use SERS as a standard analytical tool, cheap and reproducible substrates are required, preferably with a characterization technique that does not interfere with the subsequent measurements. Herein we introduce an innovative approach to produce low-cost and large-scale reproducible substrates for SERS applications, which allows easy and economical production of micropatterned SERS active surfaces on a large scale. This approach is based on an enzyme-induced growth of silver nanostructures. The special structural feature of the enzymatically deposited silver nanoparticles prevents the breakdown of SERS activity even at high particle densities (particle density >60%) that lead to a conductive layer. In contrast to other approaches, this substrate exhibits a relationship between electrical conductivity and the resulting SERS activity of a given spot. This enables the prediction of the SERS activity of the nanostructure ensemble and therewith the controllable and reproducible production of SERS substrates of enzymatic silver nanoparticles on a large scale, utilizing a simple measurement of the electrical conductivity. Furthermore, through a correlation between the conductivity and the SERS activity of the substrates it is possible to quantify SERS measurements with these substrates.

Raman spectroscopy - An essential tool for biophotonics

“…An appropriate bottom-up approach is the on demand preparation of silver nanostructures on welldefined chip surfaces by immobilizing horse radish peroxidase between microstructured electrodes via a biotin labeled DNA linker molecule [24]. An enzymatic silver reduction results in an arrangement of statistically distributed spiky silver nanoclusters, whose SERS activity can be characterized by recording the electrical conductivity [25]. These enzymatically generated SERS substrates have been successfully applied for the detection of PCR products amplified from DNA of epizootic pathogens [26].…”

Towards SERS based applications in food analytics: Lipophilic sensor layers for the detection of Sudan III in food matrices

“…The SERS active silver nanostructures were fabricated following a previously published protocol for producing enzymatically generated silver nanoparticles (EGNP) [65,67]. The method is based on the deposition of silver ions from a silver containing solution caused by the enzymatic activity of horseradish peroxidase (HRP) which is immobilized onto the substrate material.…”

“…Within this contribution, we present the application of enzymatically generated silver nanoparticles (EGNP) [65][66][67], prepared by a bottom-up and self-organizing procedure, in combination with a lipophilic sensor layer (LSL) for the detection of Sudan dyes in presence of water-soluble competitors in the sample solution. The aforementioned surface modification consists of aliphatic hydrocarbons with a thiol moiety.…”

Detection of PCR products amplified from DNA of epizootic pathogens using magnetic nanoparticles and SERS

“…[24] The produced nanoparticles show an exceptional structure enabling easy and fast characterization of the SERS activity, a high enhancement factor and a broad plasmonic absorption profile. [26] SERS substrates of enzymatically generated silver nanoparticles were already used wileyonlinelibrary.com/journal/jrs for the detection of low molecular weight substances. Here, these substrates should facilitate the detection of labeled DNA targets.…”