I. T. Shadi

Semi-quantitative analysis of indigo carmine, using silver colloids, by surface enhanced resonance Raman spectroscopy (SERRS).

The application of surface enhanced resonance Raman spectroscopy (SERRS) to the semi-quantitative analysis of the dye, indigo carmine, has been examined using citrate-reduced silver colloids. Good linear correlations are observed for the dye band at 1580 cm(-1) in the concentration range 10(-7)-10(-5) and 10(-9)-10(-5) mol dm(-3), using laser exciting wavelengths of 514.5 [(R=0.9983)] and 632.8 nm [(R=0.9978)], respectively. At concentrations of dye above 10(-6) M the concentration dependence of the SERRS signals is non-linear due to the coverage of the surface of the colloidal particles by the dye being in excess of a full monolayer. At concentrations above 10(-6) M resonance Raman spectroscopy (RRS) can be employed for the quantitative analysis of the dye. An internal standard was used and a good linear correlation (R=0.997) was observed for the dependence of dye signal intensities at 1580 cm(-1) in the concentration range 10(-5)-10(-4) M using a laser exciting wavelength of 514.5 nm. The limits of detection of indigo carmine by SERRS (514.5 nm), SERRS (632.8 nm) and solution RRS (514.5 nm) are found to be 0.9, 1 and 38 ppm, respectively.

Semi-quantitative analysis of indigo by surface enhanced resonance Raman spectroscopy (SERRS) using silver colloids

In this paper we report for the first time semi-quantitative analysis of indigo using surface enhanced Raman spectroscopy (SERS) and surface enhance resonance Raman spectroscopy (SERRS). Indigo, a dye widely used today in the textile industry, has been used, historically, both as a dye and as a pigment; the latter in both paintings and in printed material. The molecule is uncharged and largely insoluble in most solvents. The application of SERS/SERRS to the semi-quantitative analysis of indigo has been examined using aggregated citrate-reduced silver colloids with appropriate modifications to experimental protocols to both obtain and maximise SERRS signal intensities. Good linear correlations are observed for the dependence of the intensities of the SERRS band at 1151 cm(-1) using laser exciting wavelengths of 514.5 nm (R=0.9985) and 632.8 nm (R=0.9963) on the indigo concentration over the range 10(-7)-10(-5) and 10(-8)-10(-5) mol dm(-3), respectively. Band intensities were normalised against an internal standard (silver sol band at 243 cm(-1)). Resonance Raman spectra (RRS) of aqueous solutions of indigo could not be collected because of its low solubility and the presence of strong fluorescence. It was, however, possible to obtain RS and RRS spectra of the solid at each laser excitation wavelength. The limits of detection (L.O.D.) of indigo by SERS and SERRS using 514.5 and 632.8 nm were 9 ppm at both exciting wavelengths. Signal enhancement by SERS and SERRS was highly pH dependent due to the formation of singly protonated and possibly doubly protonated forms of the molecule at acidic pH. The SERS and SERRS data provide evidence to suggest that an excess of monolayer coverage of the dye at the surface of silver colloids is observed at concentrations greater than 7.85x10(-6) mol dm(-3) for each exciting wavelength. The data reported herein also strongly suggest the presence of multiple species of the indigo molecule.

Analysis of the conversion of indigo into indigo carmine dye using SERRS

In a novel application SERRS has been used, by employing a silver sol, to monitor and analyse the conversion of indigo into the indigo carmine dye.

Quantitative Detection of Alcian Blue 8GX in the Low Concentration Range Using Surface-Enhanced Resonance Raman Spectroscopy:

The viability of the application of surface-enhanced resonance Raman spectroscopy (SERRS) to the quantitative analysis of the dye alcian blue 8GX has been examined with the use of citrate- and borohydride-reduced silver colloids. A good linear correlation is observed for the dependence of the SERRS signal intensities at 1344 and 1536 cm−1 (R = 0.992 and 0.994, respectively) on dye concentrations in the range of 10−9–10−7 M, when using the citrate-reduced silver sol. Likewise, a good linear correlation is also observed for the dependence of the SERRS signal intensities at 1344 and 1536 cm−1 (R = 0.978 and 0.959, respectively) on dye concentrations in the range 10−10–10−9 M, when using the borohydride-reduced silver sol. At concentrations of dye above 10−7 M, the concentration dependence of the SERRS signals is nonlinear, almost certainly due to the coverage of the surface of the colloidal silver particles by the dye being in excess of a full monolayer. However, at concentrations of alcian blue greater than 10−7 M, resonance Raman spectroscopy (RRS) can be employed for quantitative analysis of the dye. When performing RRS, using methanol as an internal standard, we observed a good linear correlation for the dependence of the signal intensities at 1344 and 1536 cm−1 (R = 0.995 for both bands) on the dye concentration in the 10−6–10−3 M range. The limits of detection of alcian blue by SERRS using a citrate-reduced silver sol, SERRS using a borohydride-reduced silver sol, RRS, and visible absorption spectroscopy are found to be 26 ppb, 203 ppt, 2 ppm, and 0.7 ppm, respectively.

Analysis of microgels as a function of temperature by SERS

There is a paucity of data relating to the use of SERS for the investigation of temperature dependent phenomena, particularly in relation to cross-linked supra-molecular polymeric systems. Microgels-also known as SMART materialsundergo a reversible volume phase transition (VPT) [1] as a function of temperature (Fig.1). Macroscopically the VPT results from a combination of effects: the loss of interstitial bulk water molecules, changes in non-covalent molecular interactions (microgel-solvent, solvent-solvent and intra/inter-polymer chain) and conformational changes in the polymer backbone [2]. A silver sol was employed as the SERS substrate [3, 4].

Synthesis and analysis of the dye indigo carmine from indigo using SERRS

Surface enhanced resonance Raman spectroscopy (SERRS) has found wide utility as a sensitive analytical tool in a multitude of interdisciplinary scientific investigations (including e.g. chemical analysis, clinical, forensic, environmental and biological sciences, archaeological/historical applications and drug analysis) [1]. There has been a growing interest in the use of SERRS for highly sensitive quantitative chemical analyses, in a wide range of matrices, even down to the single molecule level [2, 3]. In an attempt to extend and develop novel applications of SERRS (using a silver sol) the technique has been used to monitor and analyse the synthesis of the dye indigo carmine from indigo (see Fig.1).

Raman spectroscopy of 1, 3-dicyclohexylcarbodiimide

As a prelude to examining structurally and functionally related molecules particularly in terms of the kinetics of reactions in which such compounds are involved, using vibrational spectroscopy, the Raman spectral profile of DCC has been examined. Vibrational band assignments have been made on the basis of group frequency considerations and ab initio calculations performed using the hybrid SCF-DFT (B3-LYP) method incorporating a cc-pVDZ basis set.

Surface Enhanced Resonance Raman Spectroscopy (SERRS) of Nuclear Fast Red

Nuclear fast red [4-amino-1, 3-dihydroxy-anthracene-9, 10-dione-2-sulfonic acid (sodium salt); Fig. 1] is widely used as a dye for nuclei or plasma staining of histological and haematological specimens [1–2]. Its usefulness stems from the specificity of the take up of the dye. Such formulations are used to make aqueous solutions according to standard staining protocols [3].