Are you R.G. Singh?

Claim your profile

Publications (2)5.66 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Solubilization of two different types of organic dyes, Quinizarin with an anthraquinone structure and Sudan I with an azo structure, has been studied in aqueous solutions of a series of cationic gemini surfactants and of a conventional monomeric cationic surfactant, dodecyltrimethylammonium bromide (DTAB). Surfactant concentrations both above and below the critical micelle concentration were used. The concentration of solubilized dye at equilibrium was determined from the absorbance of the solution at λ(max) with the aid of a calibration curve. The solubilization power of the gemini surfactants was higher than that of DTAB and increased with increasing alkyl chain length. An increase in length of the spacer unit resulted in increased solubilization power while a hydroxyl group in the spacer did not have much effect. Ester bonds in the alkyl chains reduced the solubilization power with respect to both dyes. A comparison between the absorbance spectra of the dyes in micellar solution with spectra in a range of solvents of different polarity indicated that the dye is situated in a relatively polar environment. One may therefore assume that the dye is located just below the head group region of the micelle. Attractive π-cation interactions may play a role for orienting the dye to the outer region of the micelle.
    Journal of Colloid and Interface Science 03/2012; 376(1):112-8. · 3.55 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, the solubilization of two organic dyes, Sudan I (1-phenylazo-2-naphtol) and Quinizarin (1,4-dihydroxyanthraquinone), was studied in the presence of different types of surfactants (nonionic, anionic, cationic, and nonionic block copolymers) using UV–vis spectroscopy. The effects of temperature, pH and electrolyte on dye solubilization were investigated for single surfactants and for binary surfactant mixtures. The results showed that the solubilization of both dyes in the surfactant micelles increased with the temperature and with addition of salt and that there was no synergy when a mixture of surfactants was used. A straight chain alkyl tail seemed to be better than an alkylaryl tail, as judged from the comparison of solubilization power for the pairs sodium dodecyl sulphate (SDS)/sodium dodecyl benzene sulphonate (SDBS) and penta(ethylene glycol)monoundecyl ether (C11E5)/nona(ethylene glycol)monononylphenyl ether (NPE9). While the solubilization of both dyes in the presence of SDS and C11E5 remained almost the same within the pH interval 3–12, the solubilization of the dyes was much higher above pH 8.2 in the presence of the cationic surfactant dodecyltrimethylammonium bromide. This was attributed to an attractive interaction between the ionized form of the dye and the positively charged head group of the micellized surfactant.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 417:133–139. · 2.11 Impact Factor