*Article* **Steel Wire Mesh as a Thermally Resistant SERS Substrate**

### **Tomasz Szymborski 1,2, Evelin Witkowska 1, Krzysztof Nici ´nski 1, Zuzanna Majka 1, Tomasz Krehlik 1, Tomiła Deskur 1, Katarzyna Winkler 1 and Agnieszka Kami ´nska 1,\***


Received: 4 July 2018; Accepted: 23 August 2018; Published: 26 August 2018

**Abstract:** In this paper, we present novel type of Surface-enhanced Raman spectroscopy (SERS) platform, based on stainless steel wire mesh (SSWM) covered with thin silver layer. The stainless steel wire mesh, typically used in chemical engineering industry, is a cheap and versatile substrate for SERS platforms. SSWM consists of multiple steel wires with diameter of tens of micrometers, which gives periodical structure and high stiffness. Moreover, stainless steel provides grea<sup>t</sup> resistance towards organic and inorganic solvents and provides excellent heat dissipation. It is worth mentioning that continuous irradiation of the laser beam over the SERS substrate can be a source of significant increase in the local temperature of metallic nanostructures, which can lead to thermal degradation or fragmentation of the adsorbed analyte. Decomposition or fragmentation of the analysed sample usually causea a significant decrease in the intensity of recorded SERS bands, which either leads to false SERS responses or enables the analysis of spectral data. To our knowledge, we have developed for the first time the thermally resistant SERS platform. This type of SERS substrate, termed Ag/SSWM, exhibit high sensitivity (Enhancement Factor (EF) = 106) and reproducibility (Relative Standard Deviation (RSD) of 6.4%) towards detection of *p*-mercaptobenzoic acid (*p-*MBA). Besides, Ag/SSWM allows the specific detection and differentiation between Gram-positive and Gram-negative bacterial species: *Escherichia coli* and *Bacillus subtilis* in label-free and reproducible manner. The unique properties of designed substrate overcome the limitations associated with photoand thermal degradation of sensitive bacterial samples. Thus, a distinctive SERS analysis of all kinds of chemical and biological samples at high sensitivity and selectivity can be performed on the developed SERS-active substrate.

**Keywords:** Surface-enhanced Raman spectroscopy (SERS); wire mesh; steel mesh; SERS platform; *Escherichia coli*; *Bacillus subtilis*
