Wafer‐Scale Polymer‐Based Transparent Nanocorals with Excellent Nanoplasmonic Photothermal Stability for High‐Power and Superfast SERS Imaging

Abstract

AbstractPolymer‐based surface‐enhanced Raman spectroscopy (SERS) substrates offer distinctive advantages such as low‐cost and high optical transparency which allows direct detection of trace chemicals on target surfaces and easy microfluidic integration. However, incident‐laser‐induced localized surface plasmon resonances can generate heat that deform the polymer and significantly reduce the intensities of recorded SERS signals. Herein, a novel wafer‐scale polymer‐based transparent nanocoral (WTNC) SERS substrate with 3D electromagnetic “hotspots” is presented. Its fabrication is simple and lithography‐free. The novel SERS substrate demonstrates excellent nanoplasmonic heat resistance, high SERS sensitivity, and unmatched SERS signal uniformity with a relative standard deviation of ≈6% across 80 mm. Excellent photothermal stability is achieved by highly crosslinking SU‐8, a negative epoxy photoresist, raising its initial degradation temperature to ≈230 °C, much higher than the glass transition temperature of state‐of‐the‐art thermalplasts used in SERS substrates, including polyethylene terephthalate and poly(methyl methacrylate). The WTNC substrate can withstand very high laser irradiance of up to 300 kW cm−2, enabling superfast SERS imaging of analytes in extremely small quantities. A high resolution SERS image containing 10 201 spectra of ≈44 amol trans‐1,2‐bis(4‐pyridyl)ethylene is obtainable in <5 min. The WTNC substrate pushes the state‐of‐the‐art in polymer‐based SERS substrates and has great potential for rapid routine analyses.