Flexible SERS-based substrates: challenges and opportunities toward an Army relevant universal sensing platform

Abstract

Generally the fabrication, assembly and evaluation of plasmonic nanostructures for surface enhanced Raman scattering (SERS) substrates has focused on static rigid substrates such as glass and silicon. However, these static substrates severely limit the application of plasmonic nanostructures as (i) they provide no means to alter the state of assembly of the nanostructures once they are formed or anchored on the surface i.e., not reconfigurable; and (ii) preclude applications which demand non-planar, flexible or conformal surfaces. The above considerations has led to the development of a novel class of SERS substrates based on flexible substrates such paper, polymer membranes and electrospun fibers. These flexible SERS media based on unconventional substrates such as paper offer distinct advantages compared to the conventional SERS substrates in that (i) flexible nature of the substrate enables conformal contact with the surfaces under investigation leading to efficient sample collection; (ii) porous nature of the SERS substrate (interstices between the fibers) provides efficient access to the analytes; (iii) high surface area of the 3D paper substrate results in large dynamic range of the chemical sensors; (iv) intricate network of fibers decorated with metal nanoparticles can provide potentially high density of electromagnetic hotspots; (v) intense light scattering caused by the fibrous structure of the substrate (e.g., paper) enables efficient light-metal interaction; and (vi) facile fabrication leads to efficient, robust, reliable, reusable and cost-effective SERS substrates. In this presentation, we will focus on the Army need for a more flexible (substrate surface and application) SERS substrate for universal sensing. This presentation will leverage from material presented at a flexible SERS (May 2014) workshop hosted by Dr. Srikanth Singamaneni at Washington University.

Fabrication of Large-Area Flexible SERS Substrates by Nanoimprint Lithography

“…26−31 The flexible SERS substrates are recognized as a sensing platform in military applications as well. 32 There are some reports on the fabrication of flexible SERS substrates made from paper, plastic, and other polymer scaffolds. 33−35 In particular, Zhang et al 34 reported a SERS substrate fabrication method using a continuous roll-to-roll (R2R) UV NIL similar to this work.…”

“…These SERS-active tapes facilitate the detection of chemical analytes on irregular and nonplanar surfaces. Compared to the traditional SERS substrates such as silicon or glass that are rigid and hard, the flexible substrates such as plastics, nanofibers, and papers are highly sought after for on-field Raman measurements and real-time monitoring of chemical and biological analytes. − The flexible SERS substrates are recognized as a sensing platform in military applications as well . There are some reports on the fabrication of flexible SERS substrates made from paper, plastic, and other polymer scaffolds. − In particular, Zhang et al reported a SERS substrate fabrication method using a continuous roll-to-roll (R2R) UV NIL similar to this work.…”

Recent Development and Applications of Stretchable SERS Substrates

“…However, traditional SERS substrates are rigid and brittle so are not feasible for some specific applications where variable plasmonic nanostructures and conformable sampling are required [30,31]. Conventional rigid substrates are usually used to detect molecular samples in liquids by dip-coating or dry samples on object surfaces by contact sampling [32].…”

Rapid and direct detection of illicit dyes on tainted fruit peel using a PVA hydrogel surface enhanced Raman scattering substrate

“…Direct analysis of surface contaminants has caught the attention of the SERS community, especially in the elds such as homeland security [26][27][28][29] and food quality assurance. [30][31][32][33][34][35] The SERS substrates involved include SERS active nanomaterials, [35][36][37][38] or coinage nanomaterials supported on various exible supporting substances, such as paper, 33,[39][40][41][42][43] polymer, 30 PDMS, 29 sandpaper, 34 and even cotton swabs. 28 Since there is no need for sample pretreatment, the main advantage of the direct surface analysis is that it can greatly streamline the onsite screening process and hence shorten the analysis time.…”