In Situ Fabricated Cu–Ag Nanoparticle-Embedded Polymer Thin Film as an Efficient Broad Spectrum SERS Substrate

Abstract

Thin films of polymer−metal nanocomposites can serve as efficient surface-enhanced Raman scattering (SERS) substrates; it would be highly advantageous if it can be fabricated by a cost-effective and facile protocol, and high enhancement factors (EF) can be realized for a range of excitation wavelengths, enabling sensitive detection of different analytes. Poly(vinyl alcohol) (PVA) thin films with embedded Cu−Ag nanoparticles are fabricated through a simple in situ procedure via stepwise formation of CuO−PVA and Cu−PVA; the fabrication is monitored through the different stages, by spectroscopy, microscopy, electron diffraction, and elemental analysis. Choice of the Cu−Ag combination is dictated by its broad plasmonic extinction, favorable cost factor, and chemical stability of the nanocomposite; the hydrogel character of PVA facilitates analyte absorption and contact with the nanoparticles, leading to efficient SERS. Cu−Ag−PVA thin film with an optimal composition is shown to display plasmonic extinction over an appreciable part of the visible range and to provide EF of the order of 10 7 −10 8 for the analytes, rhodamine 6G and methylene blue, at three different excitation wavelengths; the EF values are significantly higher than those reported earlier, with most of the Cu−Ag based SERS substrates. The novel polymer−bimetal nanocomposite thin film is an efficient SERS substrate providing subpicomolar limits of detection.

‘Dip Catalysts’ Based on Polymer‐Metal Nanocomposite Thin Films: Combining Soft‐Chemical Fabrication with Efficient Application and Monitoring

“…B atoms are generated at the expense of A; ions of A formed as the byproduct can be removed by simple washing. The nanocomposite films of bimetallic combinations we have reported include Ag−Pd‐PVA, Ag−Au‐PVA and Cu−Ag‐PVA . In a different approach, Ag/AgCl‐PVA thin films could be fabricated by first forming an AgCl‐PVA film, followed by a partial in situ photochemical reduction of AgCl…”

“…The bimetallic composition can be easily tuned by varying the concentration of the solution spread on the film. Cu−Ag‐PVA films were fabricated by first preparing Cu‐PVA films and treating it with AgNO 3 solution; Cu‐PVA was prepared by a 2‐step in situ process involving fabrication of CuO‐PVA by thermal decomposition of Cu(NO 3 ) 2 ‐PVA followed by reduction using hydrazine. The general methodology developed in these reports open up the possibilities of fabricating not only a variety of bimetallic nanoparticles inside polymer thin films, but also multi‐metallic nanoparticles; this is an area that merits systematic explorations in future.…”

“…Surface enhanced Raman scattering (SERS) substrates: SERS is a very sensitive and selective tool for the detection of compounds in extremely low concentrations. Ag‐PVA, Ag‐PVVV, Ag−Au‐PVA and Cu−Ag‐PVA film substrates provide very high enhancement factors for SERS and allow broad band application with a variety of organic analytes; detection limits down to a few picomols have been demonstrated ,, …”

SERS Research Applied to Polymer Based Nanocomposites

“…Synthetic Poly(amide) Ag Biomolecular detection [87] Poly(vinyl alcohol) Ag Biomolecular detection [95,101] Substrate characterization [97] Au Biomolecular detection [126] Medical diagnosis and target detection [126] Au@Ag Biomolecular detection [128] Cu@Ag Biomolecular detection [103] Poly(styrene) Ag Biomolecular detection [98] Substrate characterization [104] Medical diagnosis and target detection [98,117] Poly(vinylpyrrolidone) Ag Biomolecular detection [99,102,105] Poly(aniline) Ag Biomolecular detection [100] Poly(t-butylacrylate) Ag Biomolecular detection [113,114] Au Biomolecular detection [107] Poly(methyl methacrylate) Ag Biomolecular detection [115] Poly(acrylamide) Ag Biomolecular detection [118] Poly(acryloyl) Hydrazine Ag Biomolecular detection [162] Poly(ethylene glycol) Au Medical diagnosis and target detection [11,163] Heavy metal detection [122] Au@Ag SERS mapping and imaging [93] Poly(pyrrole) Ag Substrate characterization [96] poly(ethylene glycol) diacrylate…”

“…As discussed in the previous chapter, metal loaded polymer composites can be prepared by using different matrices such as synthetic [107,113,114,123,132] or natural polymers [61-63, 84, 87, 90, 151]. Polymer based composites containing metal NPs are of great interest due to their multifunctionality and potential for large-scale fabrication at low cost [23,107,[152][153][154] In the context of SERS, these composites appear as a promising alternative for the development of efficient and scalable substrates for the detection of molecular species, such as dyes [68,73,95,102,103,105,121], biomolecules [64,74,75,101,113,123,155], and environmental pollutants [48,60,85]. For example, the application of polymer-based composites as stable and active smart devices or SERS chips has increased in the last years [126,[156][157][158][159].…”