Plasmonic Slippery Surface for Surface-Enhanced Raman Spectroscopy and Protein Adsorption Inhibition

Abstract

Slippery liquid-infused porous surfaces (SLIPSs) are a class of surface that offers low contact angle hysteresis and low tilt angle for water droplet shedding. This property also endows the surface with pinning-free evaporation, which in turn has been exploited for analyte concentration enrichment for Surface Enhanced Raman Spectroscopic applications and antibiofouling. Herein, we demonstrate a facile approach for creating SLIPS with low contact angle hysteresis and low tilt angle for water shedding by coating the equal-volume mixture of polydimethylsiloxane (PDMS) and silicone oil. By exploiting the in situ plasmonic particle reduction capability of the PDMS, the surface is converted to plasmonic SLIPS, which illustrates its potential as a sensitive analytical platform via surface-enhanced Raman spectroscopy. The Raman spectroscopic studies using crystal violet as a reference sample show a limit of detection of 76 pM. Further, we have demonstrated that the fabricated plasmonic substrate is found to be more efficient in inhibiting proteins (bovine serum albumin) on the surface compared to pristine PDMS surfaces. Our fabricated plasmonic surface can find applications in ultrasensitive molecular detection for applications related to analytical chemistry, diagnostics, environmental monitoring, and national security and more importantly can control the nonspecific adsorption of proteins.

Figure 1

WCA of (a) PDMS, (b) slippery PDMS, and (c) water droplet pinned to the PDMS surface at 90° tilt. Scale bar: 1 mm. (d) Water droplet sliding on slippery PDMS at 5° tilt. Scale bar: 1 mm.

Figure 2

(a) 5 μL water droplet sliding at 10° tilt on plasmonic slippery PDMS. Scale bar: 1 mm. (b) WCA on plasmonic slippery PDMS at 101°. Scale bar: 1 mm. (c) XRD plot of slippery PDMS and plasmonic slippery PDMS. (d) Absorbance spectra of plasmonic slippery PDMS. (e) ATR–FTIR spectra of slippery PDMS and plasmonic slippery PDMS. (f) Raman spectra of slippery PDMS and plasmonic slippery PDMS.

Figure 3

(a) Optical image of plasmonic slippery PDMS at scale 100 μm. (b) Optical image of plasmonic slippery PDMS at scale 10 μm. (c) SEM image of slippery PDMS. Scale: 2 μm. (d) SEM image of plasmonic slippery PDMS. Scale: 2 μm.

Figure 4

Pinning-free evaporation of crystal violet solution on (a) plasmonic slippery PDMS, (b) slippery PDMS, and (c) coffee-ring stain of the crystal violet solution on PDMS. Scale bar: 500 μm. (d) Backscattered Raman spectra of crystal violet of varied concentration. (e) Concentration vs Intensity plot for the peak at 1376 cm^–1 Raman shift.

Figure 5

(a) Fluorescence microscopy images of FITC-BSA adhesion on PDMS, slippery PDMS, and plasmonic slippery PDMS for 1 day, 2 days, and 3 days. Scale bar: 100 μm. (b) Relative fluorescence intensity on the substrate. Error bars represent the mean ± SD. An * indicates statistical significance compared to the control groups at the level of p < 0.05 using ANOVA followed by a posthoc test. N = 3.