A surface-enhanced Raman study of N-methylquinolinium tricyanoquinodimethanide adsorbed on Ag nanospheres: Determination of molecular orientation and order.

Quinolinium tricyanoquinodimethanides are among the most promising molecules for electronic applications. Disorder can be detrimental to the desired electronic properties of a monolayer, and as such, a reliable method to characterize a monolayer without destroying or creating defects is paramount to determining potential applications. Here, the normal and surface-enhanced Raman scattering spectra of N-methylquinolinium tricyanoquinodimethanide (CH₃Q-3CNQ) on silver coated nanosurfaces have been obtained and analyzed.

Determination of molecular orientation and order of N-(6-mercaptoacetylhexyl)quinolinium tricyanoquinodimethanide adsorbed on Ag nanoparticles.

The surface-enhanced and tip-enhanced Raman scattering spectra of N-(6-Mercaptoacetylhexyl)quinolinium tricyanoquinodimethanides on silver coated nanosurfaces have been obtained, analyzed using Density Functional Theory Calculations, and a complete list of frequencies and assignments for the molecules are presented. The spectroscopic evidence points to the fact that monolayers of the molecule can be formed through the self-assembly process and the SERS data indicate that the monolayer attach to the silver surface through the nitrile groups. SERS spectroscopy was useful in determining the orientation of the monolayer as well as estimating its order.

Large-area plasmonic hot-spot arrays: sub-2 nm interparticle separations with plasma-enhanced atomic layer deposition of Ag on periodic arrays of Si nanopillars.

Initial reports of plasmonic 'hot-spots' enabled the detection of single molecules via surface-enhanced Raman scattering (SERS) from random distributions of plasmonic nanoparticles. Investigations of systems with near-field plasmonically coupled nanoparticles began, however, the ability to fabricate reproducible arrays of such particles has been lacking. We report on the fabrication of large-area, periodic arrays of plasmonic 'hot-spots' using Ag atomic layer deposition to overcoat Si nanopillar templates leading to reproducible interpillar gaps down to <2 nm.

Investigation of chemically modified barium titanate beads as surface-enhanced Raman scattering (SERS) active substrates for the detection of benzene thiol, 1,2-benzene dithiol, and rhodamine 6G.

SERS active surfaces were prepared by depositing silver films using Tollen's reaction on to barium titanate beads. The SERS activity of the resulting surfaces was probed using two thiols (benzene thiol and 1,2-benzene dithiol) and rhodamine 6G. The intensity of the SERS signal for the three analytes was investigated as a function of silver deposition time.

Vibrational assignment of the Raman active modes of 1,10-phenanthroline-5,6-dione using DFT calculations.

A complete assignment of the Raman active modes of 1,10-phenanthroline-5,6-dione in the 100-4000 cm(-1) spectral region is reported. Intense well resolved spectra of solid phendione with high S/N are reported. Assignment of the normal modes with appropriate symmetry representation symbols was achieved by employing density functional theory calculations.

Resonance Raman spectroscopy of oxoiron(IV) porphyrin pi-cation radical and oxoiron(IV) hemes in peroxidase intermediates.

The catalytic cycle intermediates of heme peroxidases, known as compounds I and II, have been of long standing interest as models for intermediates of heme proteins, such as the terminal oxidases and cytochrome P450 enzymes, and for non-heme iron enzymes as well. Reports of resonance Raman signals for compound I intermediates of the oxo-iron(IV) porphyrin pi-cation radical type have been sometimes contradictory due to complications arising from photolability, causing compound I signals to appear similar to those of compound II or other forms. However, studies of synthetic systems indicated that protein based compound I intermediates of the oxoiron(IV) porphyrin pi-cation radical type should exhibit vibrational signatures that are different from the non-radical forms.

Detection of benzopyrene-deoxyguanosine adducts by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

A method for the detection of BPDE-d guanosine adducts using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is described and illustrated. The results indicate that MALDI is capable of detecting two other DNA benzopyrene adducts, which are trace products formed during the synthesis of BPDE-d guanosine. This MALDI-TOFMS method offers the potential for the detection of DNA adducts in human tissue using very limited sample purification and preparation.

Determination of the orientation of azathioprine adsorbed on a silver electrode by SERS and ab initio calculations.

We report the SERS spectrum of azthioprine (AZA) on a silver electrode surface and the results of normal mode calculations using empirical and ab initio calculations of the 6-mercaptopurione (6-MP) component of AZA. The empirical calculations were done with a Urey-Bradley force field (UBFF) and the ab initio calculations with the STO-3G basis set using the UHF, MP2 and BLYP methods. From the difference between the SERS and solid spectra, we determined that AZA attaches edge-on to the surface through the N3 site on the 6-MP component of the molecule.