3D Flexible SERS Substrates Integrated with a Portable Raman Analyzer and Wireless Communication for Point-of-Care Application

Abstract

With the development of flexible surface-enhanced Raman spectroscopy (SERS) substrates that can realize rapid in situ detection, the SERS technique accompanied by miniaturized Raman spectrometers holds great promise for point-of-care testing (POCT). For an in situ detection strategy, constructing high-performance flexible and transparent SERS substrates through a facile and cost-effective fabrication method is critically important. Herein, we present a simple method for fabricating a large-area flexible and transparent SERS substrate consisting of a silver-nanoparticle-grafted wrinkled polydimethylsiloxane (Ag NPs@W-PDMS) film, using a surface-wrinkling technique and magnetron sputtering technology. By characterizing rhodamine 6G as a probe molecule with a portable Raman spectrometer, the flexible SERS substrate shows a low detection limit (10–7 M), a high enhancement factor (6.11 × 106), and excellent spot–spot and batch–batch reproducibilities (9.0% and 4.2%, respectively). Moreover, the Ag NPs@W-PDMS substrate maintains high SERS activity under bending and twisting mechanical deformations of over 100 cycles, as well as storage in air for 30 days. To evaluate its practical feasibility, in situ detection of malachite green on apple and tomato peels is performed with a detection limit of 10–6 M. In addition, for point-of-care analysis, we develop a wireless transmission system to transmit the collected SERS spectral data to a computer in real time for signal processing and analysis. Therefore, the proposed Ag NPs@W-PDMS SERS substrate fabricated through a simple and mass-producible method, combined with the utilization of a portable Raman spectrometer and wireless communication, offers a promising opportunity to extend the SERS technique from the laboratory to POCT applications.

Triangular Silver Nanoplates/Graphene Oxide Nanohybrids on Flexible Substrates for Detection of Bacteria via Surface-Enhanced Raman Spectroscopy

“…Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique proposed by Fleischmann et al in 1974 . It allows for the highly sensitive detection of single molecules with no interference from water molecules. − This technique has had a profound impact on optics and interface science.…”

Plasmonic 3-D wrinkled polymeric shrink film-based SERS substrates for pesticide detection on real-world surfaces

“…23 Recently, Zhang et al designed a large-area flexible and transparent SERS substrate which was able to detect up to 10 −7 M concentration of rhodamine 6G molecules. 24 Li et al developed a PDMS based flexible and transparent SERS substrate with sensitivity limited to 10 −9 M and 10 −10 M for rhodamine 6G (R6G) and methylene blue (MB) respectively. 25 Additionally, researchers have also used lithography-based pattern generation on stretchable and flexible substrates, which is a laborious, less sensitive and expensive approach with limitations related to ineffective sampling.…”

One-Step, On-Site Chemical Printing of a 3D Plasmon-Coupled Silver Nanocoral Substrate toward SERS-Based POCT

“…Surface-enhanced Raman scattering (SERS) with the advantages of high sensitivity, nondestructive analysis, and a unique fingerprint effect has been widely used in clinical diagnosis, environmental pollutant testing, food safety, and other fields. − Specifically, the portability of the Raman instrument and the capacity of rapid detection (about 10 s for each sample) ensure the high application prospect in SERS-based POCT. − The activity and uniformity of SERS enhancement substrates are the important factors in determining the sensitivity and reproducibility of SERS analysis methods. Composite plasmonic nanomaterials have often been used to provide a drastically enhanced local electric field at the surface for the signal enhancement.…”