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Semi-quantitative trace analysis of nuclear fast red by surface enhanced resonance Raman scattering
Authors:I T Shadi  B Z Chowdhry  M J Snowden  R Withnall  
Institution:

School of Chemical and Life Sciences, University of Greenwich, Woolwich, London SE18 6PF, UK

Abstract:The dye nuclear fast red has been detected and determined semi-quantitatively by means of surface enhanced resonance Raman scattering (SERRS) and surface enhanced Raman scattering (SERS), using laser exciting wavelengths of 514.5 and 632.8 nm, respectively, by employing a citrate-reduced silver colloid. A good linear correlation is observed for the dependence of the intensities of the SERRS bands at 989 cm?1 (R=0.9897) and 1278 cm?1 (R=0.9872) on dye concentration over the range 10?9 to 10?7 M, when using an exciting wavelength of 514.5 nm. At dye concentrations above 10?7 M, the concentration dependence of the SERRS signals is non-linear. This is almost certainly due to the coverage of the colloidal silver particles being in excess of a full monolayer of the dye. A linear correlation is also observed for the dependence of the intensities of the SERS bands at 989 cm?1 (R=0.9739) and 1278 cm?1 (R=0.9838) on the dye concentration over the range 10?8 to 10?6 M when using an exciting wavelength of 632.8 nm. Strong fluorescence prevented collection of resonance Raman scattering (RRS) spectra from powdered samples or aqueous solutions of the dye using an exciting wavelength of 514.5 nm, but weak bands were observed in the spectra obtained from both powdered and aqueous samples of the dye using an exciting wavelength of 632.8 nm. A study of the pH dependence of SERRS/SERS and UV–VIS absorption spectra revealed the presence of different ionisation states of the dye. The limits of detection for nuclear fast red by SERRS (514.5 nm), SERS (632.8 nm) and visible spectroscopy (535 nm) are 9, 89 and 1000 ng ml?1, respectively.
Keywords:Nuclear fast red  Silver sol  Surface enhanced resonance Raman spectroscopy (SERRS)  Surface enhanced Raman spectroscopy (SERS)  Resonance Raman spectroscopy (RRS)  Raman spectroscopy (RS)  Trace analysis
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