Rapid Fabrication of a Flexible and Transparent Ag Nanocubes@PDMS Film as a SERS Substrate with High Performance

Abstract

Flexible and transparent surface-enhanced Raman scattering (SERS) substrates have long been sought-after for nondestructive detection of analytes on nonplanar surfaces, but there is still a lack of one convenient and robust way to fabricate such SERS substrates rapidly. Herein, we demonstrate the fabrication of a high-performance SERS substrate consisting of plasmonic Ag nanocube (Ag NC) arrays anchored onto a flexible transparent poly(dimethylsiloxane) (PDMS) membrane. Through a simple organic/water interfacial self-assembly method, arrays of presynthesized Ag NCs are obtained and directly retrieved onto the PDMS membrane without the aid of rigid substrates (e.g., Si wafers or glass slides). The plasmonic Ag NC arrays can produce strong electromagnetic enhancement, achieving high SERS enhancement factor (∼3.43 × 10 6 ) and ideal detection capability for methylene blue (MB) and Rhodamine 6G (R6G) at respective trace amounts of 10 −10 and 10 −9 M. Moreover, without the need to transfer from substrate to substrate, the regular Ag NC arrays are kept intact, thereby yielding a good reproducibility (RSD ∼12%). We demonstrate further that our as-fabricated SERS substrate displays ideal selectivity toward different kinds of analyte molecules (R6G, crystal violet (CV), and MB) based on principal component analysis. The PDMS membrane owns excellent transparency and flexibility; thus, the substrate enables the conformal contact with nonplanar surfaces and allows the penetration of a laser to reach the analytes from the reverse side of the substrate. This thus facilitates in situ SERS detection of trace residual crystal violet on fish skin, with limit of detection (LOD) reaching 0.6 ppm. This fabrication method reported here is economical and easily implemented. The robust Ag NCs@PDMS could be readily prepared and stored to meet diverse SERS sensing applications, especially for in situ detection of analytes on irregular nonplanar surfaces.

Towards practical and sustainable SERS: a review of recent developments in the construction of multifunctional enhancing substrates

“…[122][123][124] For example, Chin, et al showed that Ag nanocubes can be induced to self-assembled at the water-cyclohexane interface with ethanol to form a densely packed monolayer film. 125 Subsequently, part of the cyclohexane phase was replaced with equivalent amounts of PDMS/cyclohexane solution and the entire solution was cured at 65 °C for 2 hours to allow evaporation of the cyclohexane. This led to the formation of a flexible PDMS film, which could be directly handled with a tweezer, with a densely packed monolayer of nanocubes anchored on the surface.…”

Spatially, Spectrally Single-Mode and Mechanically Flexible 3D-Printed Terahertz Transmission Waveguides

“…4(a), when the weighting percentage of PDMS decreased from 66.6% to the 50% (weight ratio of PDMS and Ag NPs decreased from 2:1 to 1:1), the transmission loss shows slight reduction from ~0.34 to ~0.23 dB/cm. The reason is ascribed to a larger covered region of the reflection layer by Ag NPs, which increase the reflectivity of inner surface of the terahertz waveguides [49]. However, the loss dramatically increased when the weighting percentage of PDMS decreased from 50% to 33.3% (weight ratio of PDMS and Ag NPs increased from 1:1 to 1:2).…”

Recent Advances in the Fabrication and Functionalization of Flexible Optical Biosensors: Toward Smart Life-Sciences Applications

“…In the same context, a relatively simple technique to fabricate plasmonic Ag Nanocubes (NCs) on PDMS was introduced as a SERS platform starting from an organic/water interface between cyclohexane and water. This technique exploits the socalled zero-transferring, i.e., the capability of preserving the spontaneous nanoparticles arrays formation at the interface between two immiscible liquids [112]. PDMS was directly inserted at the interface and no rigid materials were used for the fabrication of this device.…”