The use of conductive metal oxide (CMO) films as supporting layers for attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) is treated theoretically and experimentally. The greater mid-infrared transparency of thin layers of indium zinc oxide (IZO), as compared to metals, is verified through IR reflectivity measurements and the Drude model. IZO layers sputtered on silicon micromachined internal reflection elements (Si μIREs) are found to have a thin surface layer with slightly different plasma frequency and electronic scattering time compared to the bulk material. The complex permittivity and refractive index of the IZO can be extracted using the Drude model. This allows application of the Bruggeman effective medium theory to calculate the ATR-SEIRAS response of a layer of gold prolate spheroids supported on an IZO film. Calculated ATR-SEIRAS spectra for a 1 nm thick organic film, modeled as a Lorentz oscillator, predict an order of magnitude improvement in absorbance strength using the IZO film as a base layer compared to a conventional, gold covered internal reflection element. These predictions are qualitatively verified by the electrodeposition of gold nanoparticles on an IZO modified Si internal reflection element and the study of the potential controlled adsorption of a pyridine derivative. The IZO/Au layers are found to be very mechanically stable and can withstand large potential perturbations. This is demonstrated through the in situ study of the repeated reductive desorption of a self-assembled monolayer of 4-mercaptobenzoic acid.

Point-of-care (POC) diagnostic testing platforms are a growing sector of the healthcare industry as they offer the advantages of rapid provision of results, ease of use, reduced cost, and the ability to link patients to care. While many POC tests are based on chromatographic flow assay technology, this technology suffers from a lack of sensitivity along with limited capacity for multiplexing and quantitative analysis. Several recent reports have begun to investigate the feasibility of coupling chromatographic flow platforms to more advanced read-out technologies which in turn enable on-site acquisition, storage, and transmission of important healthcare metrics. One such technology being explored is surface-enhanced Raman spectroscopy or SERS. In this work, SERS is coupled for the first time to a rapid vertical flow (RVF) immunotechnology for detection of anti-HCV antibodies in an effort to extend the capabilities of this commercially available diagnostic platform. High-quality and reproducible SERS spectra were obtained using reporter-modified gold nanoparticles (AuNPs). Serial dilution studies indicate that the coupling of SERS with RVF technology shows enormous potential for next-generation POC diagnostics.

Dagger shaped gold particles have been electrodeposited on surfaces of conductive indium tin oxide (ITO) films. The optical extinction of these AuND@ITO substrates extends from the near-IR to long wavelength mid-infrared frequencies. AuND@ITO substrates are assessed as potential enhancing interfaces for dual modality, spectroelectrochemical, surface sensitive vibrational spectroscopy; specifically surface enhanced Raman spectroscopy (SERS) using 1064 nm excitation and attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) using a broadband emission source. The potential dependent spectra of pyridine establishes the SERS suitability of the AuND@ITO interfaces and confirms the N-bonded adsorption model. The ability of the substrates to provide surface enhancement for both SERS and ATR-SEIRAS allows an analogous study of 4methoxypyridine (MOP) and, with the assistance of DFT calculations and surface selection rules, demonstrates that MOP adsorbs with a vertical orientation over a broad range of applied potentials. In a proof of principle experiment, the SEIRAS and SERS spectra of the same self-assembled monolayer of 4-mercaptobenzoic acid (MBA) is reported using a AuND@ITO film supported on a ZnSe hemisphere.

The field of plasmonics has experienced rapid growth over the past decade with a host of emerging applications including single molecule sensing and plasmon-assisted catalysis. The vast majority of these applications use either silver or gold as the plasmonic metal, which are both high cost and face earth-abundance limitations in the next 100 years. Recent efforts have focused on taking advantage of the plasmonic properties of copper, a more abundant and low cost coinage metal as a sustainable route for plasmonic applications. In particular, there has been great interest in developing copper substrates capable of reliable and efficient enhancement of Raman signals for use in surface-enhanced Raman spectroscopy (SERS) sensing. Herein we describe a sequential electrodeposition technique whereby highly functional and robust Cu/Ag bimetallic SERS-active screen printed electrodes can be produced rapidly and at low cost, which display excellent plasmonic performance and are capable of supporting surface-plasmon assisted catalysis (SPAC). This modified screen printed electrode allows for the in situ spectroelectrochemical investigation of surface redox processes using a sustainable alternative to traditional monometallic electrodes. Over the past several decades there has been growing interest in the field of plasmonics, in particular due to the many applications which are possible now, and may be possible in the future with such a technology. In particular, SERS-based sensing, which relies heavily on the localized surface plasmon resonance (LSPR) to contribute to the large enhancement in signal, has shown promise for a multitude of applications ranging from medical diagnostics to art conservation to environmental monitoring.1-5 While Ag and Au form the bulk of metals used for SERS-based sensing, there is growing interest in the use of Cu as a plasmonic substrate due to its relatively low cost and high earth abundance. [6][7][8] In particular, large scale applications of plasmonics such as in plasmon-enhanced photovoltaics are going to require exploration of more readily scalable metals such as Cu. Cu-based SERS substrates were first explored in the early 1980's, but recent progress in this area has been slow. Limitations with the use of Cu for SERS-based sensing extend from two main issues -the ease of oxidation of Cu, which leads to a dampening of the plasmon resonance, as well as a lack of reported stable nanostructures.10 In addition, as with Au, Cu cannot be used for plasmonic applications below ∼600 nm due to interfering interband transitions.10 That being said, in recent years several groups have been working to realize the possibility of Cu-based SERS. For example, Chen et al. reported a highly efficient nanoporous Cu SERS substrate produced by dealloying of a Cu 30 Mn 70 alloy.11 In this case, selective etching of the Mn resulted in Cu nanopores with tunable sizes. In 2014, Bassetto et al. evaluated a copper-based sphere segment void (SSV) SERS structure produced using a combination of nanosphere lithography a...

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