Patchy silica-coated silver nanowires as SERS substrates

Abstract

We report a class of core-shell nanomaterials that can be used as efficient surfaceenhancement Raman scattering (SERS) substrates. The core consists of silver nanowires, prepared through a chemical reduction process, that are used to capture 4-mercaptobenzoic acid (4-MBA), a model analyte. The shell was prepared through a modified Stöber method and consists of patchy or full silica coats. The formation of silica coats was monitored via transmission electron microscopy, UV-visible spectroscopy and phase-analysis light scattering for measuring effective surface charge. Surprisingly, the patchy silica coated silver nanowires are better SERS substrate than silver nanowires; nanomolar concentration of 4-MBA can be detected. In addition, "nano-matryoshka" configurations were used to quantitate/explore the effect of the electromagnetic field at the tips of the nanowire ("hot spots") in the Raman scattering experiment.

Nanoparticle Treated Stainless Steel Filters for Metal Vapor Sequestration

“…SSW were nominally 50 mm 9 10 mm diameter pads while SSC dimensions were 10 cm 9 2 cm. Au NPs were prepared by a citrate reduction approach [8][9][10][11]13,14,16 in the presence of the filter support. Specifically, 1.25 9 10 À4 M Au 3+ was heated to boiling and 1 wt.% sodium citrate solution was added.…”

“…[8][9][10][11]13,14,16,17 It was found that the size and density of the nanoparticles' formation depends on many factors such as the reaction temperature and duration of the process as well as the nature of the solid supports and their surface energy. The desired NP size and loading density were controlled and tailored by careful selection of experimental parameters as previously reported by us.…”

“…11,12 The nature and the structure of the material can also affect the adsorption and oxidation/reduction processes, controlling the formation of adsorbed intermediates and the products. 9, 13 Decreasing the particle size and manipulating the surface conditions and properties can boost the performance of the current sequestration technologies and reduce the material's cost. 9,13 Nanomaterials' surface chemistry can be easily tailored for targeted in situ sensing and remediation processes.…”

“…9, 13 Decreasing the particle size and manipulating the surface conditions and properties can boost the performance of the current sequestration technologies and reduce the material's cost. 9,13 Nanomaterials' surface chemistry can be easily tailored for targeted in situ sensing and remediation processes. [15][16][17] For example, calixarene-crown-6 derivatives with terminal carboxyl groups attached to nano-sized magneto-ferritin molecules can sequester radioactive cesium (I) ions from aqueous solution through ion chelation.…”

“…This spectral region has been exploited for sensing, sequestration and biological applications. [8][9][10]13,14,17 Gold is also resistant to oxidation and corrosion. The ease of surface engineering with a variety of functional groups opens new doors toward exploring their outstanding mechanical, electrical and structural properties.…”