Extremely Sensitive SERS Sensors Based on a Femtosecond Laser-Fabricated Superhydrophobic/-philic Microporous Platform

Abstract

The detection of molecules from highly diluted solutions with a limited amount is vital for precancer diagnosis, food safety, and forensic analysis. The sensitivity and convenience of detection techniques are the primary concerns. In this study, a hybrid superhydrophobic/-philic (SH/SHL) microporous platform is designed and fabricated by a femtosecond laser to improve surface-enhanced Raman scattering (SERS) performances. Relying on the micropores fabricated at the center of SHL patterns, sediments distributed at the central regions are avoided, leading to the further enrichment of the target molecules. The engineered micropores with high identification further improve the speed of Raman tests, and the fabricated SERS substrate shows an advantage in outdoor handheld detection and automated inspection applications. The optimized SERS sensor is sufficient for attomolar-level detection (10 −17 M) of rhodamine 6G using analyte volumes of just 5 μL, corresponding to an enhancement factor of 5.19 × 10 13 . Meanwhile, a relative standard deviation of 7.48% at 10 −10 M shows the excellent uniformity of this proposed SERS platform. This work further pushes forward the practical applications of SERS technology in ultratrace molecular detections.

Plasma‐Etched Nanograss Surface without Lithographic Patterning to Immobilize Water Droplet for Highly Sensitive Raman Sensing

“…The gradually decreasing contact angle suggests that the water droplets were firmly anchored to the surface, which differs from a typical superhydrophobic surface that maintains a high contact angle throughout the water evaporation process. [ 23 ]…”

“…The gradually decreasing contact angle suggests that the water droplets were firmly anchored to the surface, which differs from a typical superhydrophobic surface that maintains a high contact angle throughout the water evaporation process. [23] The ability to anchor a droplet to a superhydrophobic surface enables precise positioning without complex lithographic patterning processes. As shown in Figure 3a, a two-step positioning method was used to create a plasmonic active region for analytes, wherein a 2.5 μL droplet containing 100 nm Ag nanoparticles (0.02 mg mL −1 ) was first placed on the surface.…”

“…However, typical state‐of‐the‐art superhydrophobic surfaces are slippery with low sliding angles for droplets. Therefore, they need to be positioned using lithographic patterning processes [ 18,19,21 ] (i.e., optical lithography, [ 22 ] e‐beam lithography, [ 6 ] laser writing, [ 23 − 25 ] laser printing, [ 26 ] and particle assembly) [ 27 ] to locate the droplets, which renders the fabrication process complex, expensive, and time‐consuming. Although most superhydrophobic surfaces are slippery, sticky (adhesive) superhydrophobic surfaces have also been reported.…”

Sensitive and reproducible gold nanostar@metal–organic framework-based SERS membranes for the online monitoring of the freshness of shrimps

“…17 Furthermore, well-designed hydrophobic substrates can concentrate plasma-sensitive regions, boosting the SERS substrate detection sensitivity and repeatability. 21,22 In particular, the slippery liquid-infused porous surface (SLIPS), a stable, defect-free, inert “slippery” interface, has been exploited in the design of SERS sensing substrates. 23,24…”

“…17 Furthermore, well-designed hydrophobic substrates can concentrate plasma-sensitive regions, boosting the SERS substrate detection sensitivity and repeatability. 21,22 In particular, the slippery liquid-infused porous surface (SLIPS), a stable, defect-free, inert "slippery" interface, has been exploited in the design of SERS sensing substrates. 23,24 Herein, combining SLIPS, plasmonic nanoparticles, and metal-organic framework (NP@MOF) composites, a facile strategy for efficient, real-time, dual-indicator monitoring of seafood spoilage is proposed.…”