Interfacial Behavior of Sulforhodamine 101 at the Polarized Water|1,2-Dichloroethane Interface Studied by Spectroelectrochemical Techniques

Department of Applied Chemistry, Faculty of Engineering, Nagasaki University, Bunkyo, Nagasaki, 852-8521, Japan.
Analytical and Bioanalytical Chemistry (Impact Factor: 3.44). 11/2006; 386(3):633-8. DOI: 10.1007/s00216-006-0497-z
Source: PubMed


The transfer mechanism of an amphoteric rhodamine, sulforhodamine 101 (SR101), across the polarized water/1,2-dichloroethane (DCE) interface was investigated using cyclic voltammetry, differential voltfluorometry and potential-modulated fluorescence (PMF) spectroscopy. The voltammetric response for the ion transfer of SR101 monoanion from water to DCE was observed as the diffusion-controlled transfer process. An unusual voltammetric response was found at 0.15 V more negative than the formal transfer potential of SR101(-) (deltaW(O)phi degrees') in the cyclic voltammogram and voltfluorogram. The frequency dependence of the PMF responses confirmed the presence of the adsorption processes at negative potentials. In addition, a further transient adsorption step was uncovered at deltaW(O)phi degrees'. The interfacial mechanism of SR101 is discussed by comparing the results obtained from each technique.

Download full-text


Available from: Hubert H Girault,
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ion transfer and adsorption of amphoteric rhodamines, that is, Rhodamine B (RB), Rhodamine 19 (R19), and Rhodamine 110 (R110), and a cationic rhodamine, Rhodamine 123 (R123), at a polarized 1,2-dichloroethane/water (DCE/W) interface, were studied by means of cyclic voltammetry and potential-modulated fluorescence (PMF) spectroscopy. For all rhodamines, a well-defined voltammetric wave was obtained and the pH dependence of the reversible half-wave potential (i.e., midpoint potential) was investigated to prepare the ionic partition diagram. Theoretical considerations of the diagrams showed that the voltammetric waves obtained for the amphoteric rhodamines were not due to a simple transfer of the protonated form (R+) but due to the transfer of H+ facilitated by the amphoteric form (R±) in DCE (and partly in W for R110):  H+(W) + R±(DCE or W) → R+(DCE). In PMF spectroscopy, the PMF signal due to the adsorption of R+ at the interface could be obtained for RB, R19, and R123, only when the Galvani potential difference across the interface ( φ) was lower than −0.14 V, suggesting a significant role of φ in the interfacial adsorption of the rhodamines. The PMF spectrum obtained for the rhodamines under these conditions suggested that the xanthene ring of the adsorbed species should be located in the DCE phase. Furthermore, the dependence of PMF on the angle of polarization of the excitation beam suggested that the longitudinal axis of the xanthene ring should tilt only by 20−25° with respect to the interface.
    The Journal of Physical Chemistry C 06/2007; 111(26). DOI:10.1021/jp0723315 · 4.77 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Potential-modulation spectroelectrochemical methods at solid/liquid and liquid/liquid interfaces are reviewed. After a brief summary of the basic features and advantages of the methods, practical applications of potential-modulation spectroscopy are demonstrated using our recent studies of solid/liquid and liquid/liquid interfaces, including reflection measurements for a redox protein on a modified gold electrode and fluorescence measurements for various dyes at a polarized water/1,2-dichloroethane interface. For both interfaces, the use of linearly polarized incident light enabled an estimation of the molecular orientation. The use of a potential-modulated transmission-absorption measurement for an optically transparent electrode with immobilized metal nanoparticles is also described. The ability of potential-modulated fluorescence spectroscopy to clearly elucidate the charge transfer and adsorption mechanisms at liquid/liquid interfaces is highlighted.
    Analytical Sciences 10/2007; 23(9):1041-8. DOI:10.2116/analsci.23.1041 · 1.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An overview on electrochemistry on the interfaces between two immiscible electrolyte solutions is given.
    Journal of the Chilean Chemical Society 06/2008; 53(2). DOI:10.4067/S0717-97072008000200002 · 0.35 Impact Factor
Show more