SERS-enhanced piezoplasmonic graphene composite for biological and structural strain mapping

Abstract

Thin-film optical strain sensors have the ability to map small deformations with spatial and temporal resolution and do not require electrical interrogation. This paper describes the use of graphene decorated with metallic nanoislands for sensing of tensile deformations of less than 0.04% with a resolution of less than 0.002%. The nanoisland-graphene composite films contain gaps between the nanoislands, which when functionalized with benzenethiolate behave as hot spots for surface-enhanced Raman scattering (SERS). Mechanical strain increases the sizes of the gaps; this increase attenuates the electric field, and thus attenuates the SERS signal. This compounded, SERS-enhanced “piezoplasmonic” effect can be quantified using a plasmonic gauge factor, and is among the most sensitive mechanical sensors of any type. Since the graphene-nanoisland films are both conductive and optically active, they permit simultaneous electrical stimulation of myoblast cells and optical detection of the strains produced by the cellular contractions.

Gold Nano-Island Platforms for Localized Surface Plasmon Resonance Sensing: A Short Review

“…The surface energy of the substrate supports that graphene influenced the morphology of the nano-island films, and thus, a wide range of morphologies could be produced, from isolated islands to percolated networks. These graphene nano-island composite films exhibit tunable morphologies and small gaps between adjacent nano-islands, and could be transferred to flexible substrates [ 18 ].…”

Graphene–Metal Composite Sensors with Near-Zero Temperature Coefficient of Resistance

“… 17 This phenomenon is in contrast to metals, which typically have a positive TCR owing to an increase in both inelastic electron scattering and lattice spacing with temperature. 18 Given our previous experience with metal nanoislands on graphene as a platform for multimodal sensing, 2 , 19 we hypothesized that a zero-TCR sensor could be fabricated if the right amount of metal was deposited onto the graphene such that the effects of each material cancel each other out. To design this material, we characterized the effect of deposition thickness and island morphology on the TCR of the graphene–metal composites.…”

Metallic nanoislands on graphene: a metamaterial for chemical, mechanical, optical, and biological applications

“…6,74,75,25,76,77,78 The role of graphene in the majority of these applications is as a substrate, allowing easy transfer onto arbitrary substrates for specific applications such as optical strain sensing using SERS (Figure 6c, d). 7 Additionally, it has been shown that graphene can also mitigate the effects of fluorescence in SERS signal-to-noise ratios. In recent work, the role of graphene has been expanded by exploiting its electrical conductivity to actuate musculoskeletal cells (Figure 6e, f).…”

“…Metal nanoislands on graphene have been used extensively as surface-enhanced Raman scattering (SERS) substrates with numerous applications such as structural strain mapping and time-dependent biological strain detection (c–g). (c–g) Reprinted and adapted with permission from reference 7 and the Royal Society of Chemistry. A silver nanoisland on graphene substrate on bent glass is depicted (c) with the SERS mapped area marked by the narrow yellow box and the apex of the bent glass marked by the white dashed line.…”

“…For example, the deposition of metal particles onto graphene can change its band gap, 1,2 optical properties, 3,4 and give rise to catalytic behavior 5 and properties such as enhanced piezoresistance 6 and strain-evolved optical—i.e., “piezoplasmonic”—effects. 7 These properties are most closely associated with semiconducting materials, but can emerge in metal-graphene composites if the metal overlayer has the right thickness or morphology (e.g., interconnectivity or pattern). 8,9 Graphene serves a dual role in these composite films.…”