Abstract
This paper reports a highly sensitive and selective surface-enhanced Raman spectroscopy (SERS) sensing platform. We used a simple fabrication method to generate plasmonic hotspots through a direct maskless plasma etching of a polymer surface and the surface tension-driven assembly of high aspect ratio Ag/polymer nanopillars. These collapsed plasmonic nanopillars produced an enhanced near-field interaction via coupled localized surface plasmon resonance. The high density of the small nanogaps yielded a high plasmonic detection performance, with an average SERS enhancement factor of 1.5 × 107. More importantly, we demonstrated that the encapsulation of plasmonic nanostructures within nanofiltration membranes allowed the selective filtration of small molecules based on the degree of membrane swelling in organic solvents and molecular size. Nanofiltration membrane-encapsulated SERS substrates do not require pretreatments. Therefore, they provide a simple and fast detection of toxic molecules using portable Raman spectroscopy.
Highlights
Plasmonic nanogaps enable the detection of single molecule using surface-enhanced Raman spectroscopy (SERS) [1,2,3,4]
The surface-tension-driven leaning effects applied to the Ag/polyethylene terephthalate (PET) nanopillars led to the assembly of high-density plasmonic nanogaps
The Ag NPs/PET nanopillars collapsed and leaned together through water-driven capillary leaning effects, and the leaning nanostructures were encapsulated by a PDMS membrane
Summary
Plasmonic nanogaps enable the detection of single molecule using surface-enhanced Raman spectroscopy (SERS) [1,2,3,4]. Among the many fabrication methods tested, the surface tension-induced leaning of metallic nanopillars offers a simple and desirable strategy for generating small nanogaps [14,15,16,17,18,19]. The main function of both natural and synthetic membranes is to allow for the selective permeation of target substances through the membrane pores This functionality naturally suggests that semipermeable layers might be integrated into plasmonic nanostructures to provide high molecular selectivity. The development of metal nanostructures with antibody-, enzyme-, or chemical-ligand-functionalized surfaces would require molecular selectivity This type of surface treatment would involve capturing one specific target molecule through antibody–antigen or ligand–receptor binding interactions. The plasmonic substrates were deposited with ultrahigh-density (53/μm2) top Ag NPs. The surface-tension-driven leaning effects applied to the Ag/PET nanopillars led to the assembly of high-density plasmonic nanogaps. Dissolving the MB molecules in deionized (DI) water resulted in the exclusion of even the small MB molecules because the PDMS membrane did not swell in DI water
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