V. Anantha Narayanan

Surface-enhanced Raman detection of nicotinamide in vitamin tablets

Abstract Nicotinamide is analyzed quantitatively in vitamin tablets using surface-enhanced Raman scattering (SERS) on a silver-coated alumina substrate. Calibration curve of SERS signal intensity versus concentration of nicotinamide was established for quantitative analysis of this compound for detection at parts per million (ppm) level. SERS spectra of related compounds, nicotine, nicotinic acid, isonicotinic acid, and isonicotinamide were also recorded. Salient features of their spectra are compared and discussed.

Evaluation of a chemical vapor dosimeter using polymer-coated SERS substrates

Abstract This paper describes the development and evaluation of an improved passive chemical dosimeter using poly(vinylpyrrolidone) coating on a surface-enhanced Raman scattering (SERS) substrate for monitoring airborne chemicals. Experimental studies are performed to demonstrate the longevity, enhancement of Raman signals, and selectivity of the dosimeter. The new substrate has been used to monitor exposure to vapors of benzoic acid, 2-aminopyrimidine, and 2,4-dinitrophenol over 20-day periods. The improved performance of the newly developed polymer-coated substrate is compared to that of uncoated SERS substrates. Results of substrate optimization and shelf-life studies are discussed.

Surface-enhanced Raman scattering interaction of p-aminobenzoic acid on a silver-coated alumina substrate

Abstract The adsorption behavior of p -aminobenzoic acid (PABA) molecules on a silver-coated alumina surface-enhanced Raman scattering (SERS) substrate was investigated. For spotted PABA and PABA in non-polar solvents, the PABA molecule is adsorbed flat on the surface of the SERS substrate. In this orientation, the benzene ring is π-bonded to the substrate, and the molecule is further anchored to the substrate by the binding of the lone pairs of NH 2 and COO − groups onto the metal surface. On the other hand, the adsorption behavior of PABA in a polar solvent is greatly influenced by the hydrogen bonding of the amine group with the polar solvent. In this orientation, the molecule is preferentially adsorbed through the COO ± and assumes a non-flat orientation on the metal surface.

Surface-Enhanced Raman Analysis of some Polycyclic Aromatic Dyes used in the Cosmetics and Food Industries

Abstract The Surface-Enhanced Raman spectra of three important polycyclic aromatic dyes used in the food and cosmetic industries. Erythrosine, Eosine, and Phloxine, are recorded for the first time. The ability of the Surface-Enhanced Raman scattering techniques to detect these dyes at trace level is demonstrated. Such techniques minimize the fluorescence background in these highly fluorescing dyes, bringing out the Surface-Enhanced Raman Spectra features. The Normal Raman Spectra of erythrosine and phtalazine were also recorded and compared with their Surface-Enhanced Raman Spectra to illustrate the fluorescence suppression in Surface Enhanced Raman Spectra. The vibrational spectra features of the three dyes are discussed in terms of their molecular structure and the vibrations of the aromatic rings.

Vibrational spectrum of strychnine: detection at the nanogram level using a raman microscope

The complete vibrational spectra of strychnine is reported. Strychnine, a compound with medicinal value at the proper dosage, is also a potent toxin at certain concentration levels. Down to 5 ng of strychnine were detected from its spectrum using a microscope attached to a Raman spectrophotometer. The complete Raman and Fourier transform IR spectra were also recorded for positive identification. The prominent vibrational band wavenumbers useful as a reference source for the identification of strychnine in an emergency situation are discussed. The Raman spectra of a bulk sample and of a strychnine microcrystal are given to facilitate positive identification. The potential application of the vibrational analysis of strychnine for forensic diagnostics is discussed. Copyright