Elastomeric Substrates with Femtosecond(fs)-Laser Fabricated Hierarchical Micropillar-Nanostructures for Strain-Active Sub-fM Ultrasensitive Raman Detection.

Abstract

The challenge to ultrasensitive surface-enhanced Raman spectroscopy (SERS) has to trade off the detection sensitivity and storage stability for the sophisticated SERS substrates. The tunable surface wettability is hence critical to switch the capture mode for detection and protection state for antifouling storage. However, surface-wettability-tunable substrates generally require reversible electric-, light-, temperature- or pH-sensitive properties to regulate the substrate nanostructures and chemical properties, for which complicated operation procedures are inevitable. Here, an elastomeric fluorophlogopite SERS substrate composed of a hierarchical micropillar-nanostructure array is reported by femtosecond(fs)-laser nanofabrication. The wettability of the substrate is reversibly tuned by mechanical strain from the free superhydrophobic surface (156°) in Cassie state to the compressive hydrophilic one (76°) in Wenzel state. The wettability-controllable surface facilitates to capture of target molecules for limit of detection down to 0.1fM@5 µL with the enhancement factor of 2.46 × 10¹² for Rhodamine 6G, of which the standard deviation is 7.8%, indicating good homogeneity. The developed elastomeric SERS substrate not only demonstrates the anti-pollution for long-term storage but also provides a simple way to switch the surface wettability for ultrasensitive Raman detection, holding promise for ultrasensitive clinical and biological SERS in future.