Cost-Effective Plasmonic Platforms: Glass Capillaries Decorated with Ag@SiO₂ Nanoparticles on Inner Walls as SERS Substrates

Abstract

A cost-effective method for the fabrication of a glass capillary based plasmonic platform for the selective detection and identification of analytes of importance in health, environment, and safety is demonstrated. This was achieved by coating Ag@SiO nanoparticles (Ag ∼ 60 nm) having silica shell of varying thickness (∼2 and ∼25 nm) on the inside walls of glass capillaries, over 2 cm in length, with uniform coverage. It was found that the particle density on the surface plays a decisive role on the enhancement of Raman signals. Multiple hot spots, which are essentially junctions of amplified electric field, were generated when ∼30 Ag@SiO particles/μm were bound onto the walls of glass capillaries. The pores of the silica shell allow the localization of analyte molecules to the vicinity of hot spots resulting in signal enhancements of the order of 10 (using pyrene as analyte; excitation wavelength, 632.8 nm). The applicability of Ag@SiO coated capillaries for the detection of a wide range of molecules has been explored, by taking representative examples of polyaromatic hydrocarbons (pyrene), amino acids (tryptophan), proteins (bovine serum albumin), and explosives (trinitrotoluene). By increasing the thickness of the silica shell of Ag@SiO nanoparticles, an effective filtration cum detection method has been developed for the selective identification of small molecules such as amino acids, without the interference of large proteins.

Rapid, Label‐free Optical Spectroscopy Platform for Diagnosis of Heparin‐Induced Thrombocytopenia

“…While previous studies have suggested different routes for assembling nanoparticles inside a capillary, we propose here a simpler fabrication approach that features the single‐step, rapid growth of a bare silver nanoparticle film on the capillary wall. Specifically, we employed a solution‐processed, in situ reduction route to generate the plasmonic coating.…”

“…It has been previously suggested that coating plasmonic nanoparticles on the inside walls of glass capillaries could lead to high electromagnetic enhancement enabling small molecule detection while conserving precious specimen . The potential of such a construct for designing and controlling SERS for sensing, however, has not been exploited for analyzing complex mixture samples, where a variety of biomolecular species are likely to contribute to the acquired spectral profile.…”

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“…SERS is employed to detect different materials from biological to environmental analyts [5]. The Raman weak cross section limits its application, so the analyte molecules should be located in close proximity of plasmonic nanostructure [6] & [7]. If nanoparticles have had a constant size distribution throughout the SERS sample and have been sufficiently close to each other, a strong interaction between the nanoparticles and analyte molecules would be gained [8].…”

Ag Nanotwin-Assisted Grain Growth-Induced by Stress in SiO2/Ag/SiO2 Nanocap Arrays

“…Surface plasma is the collective movement of electrons in metals, which occurs when the electrons are driven by an electromagnetic wave [ 20 ]. When the fluctuation of the surface plasma-formed field is no longer continuous in space, for example, in isolated metal nanostructures, the surface plasmon becomes a localized surface plasmon (LSP).…”