Microchannel plate (MCP) functionalized with Ag nanorods as a high-porosity stable SERS-active membrane

Surface-enhanced Raman scattering (SERS) encountered in interstitial gaps between closely positioned metal nanostructures, hot spots, offers tremendous potential for molecular analysis at the trace or single-molecule level. SERS-active sites, hot spots, can be achieved at a higher density when metal nanostructures are configured on a three-dimensional (3D) platform than on a planar two-dimensional (2D) substrate. Yet, 3D platforms demonstrated thus far such as anodized alumina and microstructured fibers offer capillaries/pores either too narrow for the sample to be infused or may not be compatible with microfluidic integration due to their non-planar feature. Here, we introduce a 3D SERS-active platform based on a planar component that is readily available and presents densely packed highly aligned precision microchannels, the so-called microchannel plate (MCP). The microchannels, owing to their alignment biased at a small but precise angle (7°) with respect to the plate surface normal and their reasonably large diameter (~6 μm) can be functionalized with Ag nanorods through shadowing-based deposition that requires no other template or lithography. The plate functionalized with Ag nanorods delivers an enhancement factor with values in the range of 106–108 as verified with probing molecules 4-mercatobenzoic acid (4-MBA) and rhodamine-6G.