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A label-free sensing platform is described for the detection of single-stranded DNA by using surface-enhanced Raman scattering (SERS). The Raman spectra of molecules serving as Raman labels residing on the hot spot are enhanced and the sensing of the target species is confirmed by the appearance of an intense SERS signal of the Raman label, which is bound to the surface of the Ag film.

Surface-enhanced Raman scattering (SERS) of 4-nitrothioanisole (4-NTA) is investigated in Ag sol. The molecule is found to adsorb on Ag as 4-NTA via the sulfur atom.

Surface-enhanced Raman scattering spectra (SERS) of BPS were obtained in si lver sol to examine the excitation-wavelength dependence of their surface-induces photoreaction on silver. The C-S bond cleavage of BPS on Ag to produce benzenethiolate was confirmed to be very effective under green light at 514.5nm.

The structure and thermal behavior of silver perfluorocarboxalates by using various analytical tools is studied. The results show that the Perfluorocarbons are a promising organic moiety endowing the organic/inorganic hybrid materials with high thermal stability.

The use of heteropoly acid (HPA)-incorporated TiO2 colloids as a new photocatalytic system resembling the photosynthetic reaction center is analyzed. It was seen that the coupling of HPA with TiO2, which transfers electrons directly to interfacial HPA, could enhance the photoreduction of HPA.

The dominant physical transport processes are analyzed in a free-surface microfluidic and surface-enhanced Raman spectroscopy (SERS) chemical detection system. The analysis describes the characteristic fluid dynamics and mass transport effects occurring in a microfluidic detection system whose analyte absorption and concentration capability is designed to operate on principles inspired by canine olfaction. The detection system provides continuous, real-time monitoring of particular vapor-phase analytes at concentrations of 1 ppb. The system is designed with a large free-surface-to-volume ratio microfluidic channel which allows for polar or hydrophilic airborne analytes to readily be partitioned from the surrounding gas phase into the aqueous phase for detection. The microfluidic stream can concentrate certain molecules by up to 6 orders of magnitude, and SERS can enhance the Raman signal by 9-10 orders of magnitude for molecules residing in the so-called SERS "hot spots", providing extremely high detection sensitivity. The resulting vibrational spectra are sufficiently specific to identify the detected analyte unambiguously. Detection performance was demonstrated using a nominal 1 ppb, 2,4-dinitrotoluene (2,4-DNT) vapor stream entrained within N2 gas. Applications to homeland security arise from the system's high sensitivity and its ability to provide highly reproducible, continuous chemical detection monitoring with minimal sampling requirements. [ABSTRACT FROM AUTHOR]

Arrays of periodically disposed silver nano- wires embedded in alumina were shown to be capable of conducting plasmons excited by laser illuminating one end of the array to its opposite end where surface-enhanced Raman of molecules resident among the tips of the nanowires was excited. The SERS signals, in turn, excited plasmons which propagated back to the originally illuminated ends of the nanowires where they emitted light signals that were collected and spectroscopically dispersed, in essence creating a sensor capable of exciting and collecting SERS remotely. For nanowire arrays with interwire gaps of ~11 nm and lengths of ~3.3 μm (i.e., after a ~6.6 μm round trip) the SERS signals obtained by remote sensing were rather strong, ~5% the intensity of those obtained by exciting the molecules resident among the nanowire tips directly. [ABSTRACT FROM AUTHOR]

Uniform nanogaps were produced in silver nanowires previously fabricated by AC electrodeposition in porous anodic alumina templates and released by dissolving the oxide matrix. Configuring the nanowires with electrodes and passing current through them created nanogaps by electromigration. Uniform nanogaps approximately perpendicular to the axes of the nanowires were produced with widths in the range ∼17 to ∼40 nm. Gaps as small as 5 nm but with less uniform geometries could also be produced in this manner. A heuristic model, in which electromigrative and diffusional effects are included, is used to relate the size of the nanogap produced to the local resistance of the region in the nanowire where the gap ultimately forms. Intense surface-enhanced Raman spectra were observed from Rhodamine 6G adsorbed on the nanowire in the gap. For gaps that uniformly divided the nanowire across its width, the surface enhanced Raman spectroscopy intensity was maximum when the electric vector of the exciting light was oriented across the gap, as predicted by electromagnetic enhancement calculations. [ABSTRACT FROM AUTHOR]

Single silver nanowires produced by DC electrodeposition in porous anodic alumina templates were surface-functionalized with the bifunctional molecule 4-aminobenzenthiol (ABT) then exposed to aqueous silver nanoparticles resulting in a silver nanoparticle-decorated silver nanowire. The polarization dependent surface-enhanced Raman (SERS) signal from this system showed significant intensity anisotropy when measured at a midsection of the nanowire, where the largest SERS intensities were observed when the incident light was polarized perpendicular to the nanowire’s long axis but was almost isotropic near the tip of the nanowire. The observed effects were accounted for in terms of the electromagnetic fields concentrated in the collection of hot spots created through the ABT-linker-driven nanoparticle-nanowire self-assembly process. [ABSTRACT FROM AUTHOR]

The article provides information on a study that investigates hot spots in silver nanowire bundles for surface-enhanced Raman spectroscopy. It demonstrated a simple strategy for obtaining hot spots of the form "metal/molecule/metal", which automatically and eventually positions many analyte molecules in the junction between neighboring tips of silver nanowires that were fabricated in porous aluminum oxide (PAO) then exposed by the controlled dissolution of the alumina matrix. The article informs that silver nanowires were grown in highly ordered PAO template by AC electrodeposition.

The article reports on a study concerning the utility of the surface-enhanced Raman spectroscopy (SERS) method for DNA Detection. In this study, researchers analysed how a single-stranded DNA (ssDNA) identification method takes advantage of surface-bound acids (PNAs) and an interplay of electrostatic interactions which produces SERS signals upon ssDNA/PNA hybridization.