Electroless deposition via galvanic displacement as a simple way for the preparation of silver, gold, and copper SERS-active substrates

Fabrication of gold nanoparticles tethered in heat-cooled calf thymus-deoxyribonucleic acid Langmuir-Blodgett film as effective surface-enhanced Raman scattering sensing platform

SERS active substrate fabricated through self-assembly of Gold nanoparticles on the disjointed networks of Heat-cooled Calf Thymus DNA (HC-Ct DNA) Langmuir-Blodgett (LB) film has been reported. Adsorption kinetics of HC-Ct DNA molecules at the air-water interface has been studied explicitly. The UV-Vis electronic absorption spectra in conjunction with the FESEM images collectively suggest the presence of H- type aggregated domains most likely owing to plane-to-plane self-association of the HC-Ct DNA molecules aligned vertically on the surface of the LB film. Elemental composition and the morphological features of the as-prepared substrate (APS) are explored from XPS analysis and the FESEM, AFM images respectively. The SERS efficacy of the APS has been tested with trace concentrations of 4-Mercaptopyridine molecule. Finally, this SERS active substrate has also been used for the detection of malathion at ultrasensitive concentrations.

Fabrication of Efficient Gold−Nickel-Supported Titania Nanotube Electrocatalysts for Sodium Borohydride−Hydrogen Peroxide Fuel Cells

Here we report the optimization of the fabrication conditions for AuNi bimetallic catalysts supported on self-ordered titania nanotube arrays (AuNi-TiO2ntb). A series of efficient AuNi-TiO2ntb catalysts with small amounts of Au in the range of 1.74 to 15.7 μgAu·cm−2 have been fabricated by anodization, electroless Ni plating, and galvanic displacement techniques. The electrocatalytic activity of the catalysts has been evaluated for BH4− ion oxidation in an alkaline medium using cyclic voltammetry and chronoamperometry. The performance of a NaBH4-H2O2 fuel cell with Ni-TiO2ntb and AuNi-TiO2ntb anode catalysts has been investigated at different temperatures. It was found that the electrocatalytic activity of AuNi-TiO2ntbs catalysts was improved remarkably when the Ni layer of 100 and 400 nm was used for the deposition of Au crystallites. The Ni-TiO2ntb catalyst generates the maximum power density values of ca. 85–121 mW·cm−2 at a temperature of 25–55 °C, whereas the AuNi-TiO2ntb catalysts that have the Au loading of 3.07 and 15.7 μgAu·cm−2 achieve the power density values of ca. 104–147 and 119–170 mW·cm−2, respectively, at a temperature of 25–55 °C.

3D Printed SERS-Active Thin-Film Substrates Used to Quantify Levels of the Genotoxic Isothiazolinone

Several reports present methods to fabricate thin-film substrates capable of surface-enhanced Raman scattering (SERS). Substrates synthesized by displacing silver onto copper using facile synthesis methods such as galvanic displacement can generate high levels of SERS enhancement rivaling commercially available substrates manufactured by lithographic methods. Here, we describe the optimization of a novel set of SERS-active thin-film substrates synthesized via the electroless displacement of Ag onto the surface of three-dimensional (3D) printed disks composed of the copper/polymer (PLA) composite filament. The effect of AgNO₃ concentration on the deposition, morphology, and overall SERS activity of the substrates has been carefully studied. Two commonly used Raman reporters, 4-mercaptobenzoic acid (MBA) and malachite green isothiocyanate (MGITC), were used to measure the SERS output of the substrates. Good SERS signal reproducibility (RSD ∼16.8%) was measured across the surface of replicate substrates and high-sensitivity detection of MBA was achieved (10^-12 M). To test the real-world application of our substrates, we opted to detect 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), which is a genotoxic, biocide common in many household products, known to leach into water supplies. Our newly developed SERS-active substrates could detect CMIT down to 10 ppm when spiked in simulated lake water samples, which is well within current agency standards.