Electron Transfer through Clay Monolayer Films Fabricated by the Langmuir−Blodgett Technique

ArticleinLangmuir 22(23):9591-7 · December 2006with9 Reads
DOI: 10.1021/la061668f · Source: PubMed
Hybrid films composed of amphiphilic molecules and clay particles were constructed by the modified Langmuir-Blodgett (LB) method. Clays used were sodium montmorillonite (denoted as mont) and synthetic smectite containing Co(II) ions in the octahedral sites (denoted as Co). Two kinds of amphiphilic molecules were used-[Ru(dC(18)bpy)(phen)2](ClO4)2 (dC(18)bpy = 4,4'-dioctadecyl-2,2'-bipyridyl and phen = 1,10-phenanthroline) (denoted as Ru) and octadecylammonium choloride (ODAH+Cl- or denoted as ODAH). Three kinds of hybrid films (denoted as Ru-mont, Ru-Co, and ODAH-Co films) were prepared by spreading an amphiphilic molecule onto an aqueous suspension of a clay. Atomic force microscopy (AFM) analyses of the films deposited on silicon wafers indicated that closely packed films were obtained at 20 ppm for all the above three cases. Cyclic voltammetry (CV) was measured on an ITO electrode modified with a hybrid film or a monolayer film of pure Ru(II) complex salt (denoted as Ru film). The Ru(II) complexes incorporated in the Ru-mont film lost their redox activity, indicating that montmorillonite layers acted as a barrier against electron transfer. In contrast, the same complexes in the Ru-Co film were electrochemically active with the simultaneous appearance of the redox peaks due to the Co(II)/Co(III) (or Co(II)/Co(IV)) couple. The results implied that electron transfer through cobalt clay layers was possible via mediation by Co(II) ions in a clay sheet. For an aqueous solution containing nitrite ions (NO2-) at pH 3.0, a large catalytic oxidation current was observed for both the electrodes modified with the Ru-mont and Ru-Co films. The results were interpreted in terms of the mechanisms that the charge separation of an incorporated Ru(II) complex took place to produce a pair of a Ru(III) complex and an electron and that the generated Ru(III) complex was reduced by a nitrite ion before it recombined with the electron.
    • "Layered materials like clay minerals (Umemura et al., 2001Umemura et al., , 2002Umemura et al., , 2009 Yamamoto et al., 2004b; Junxiang et al., 2005; Yoshida et al., 2006; Gengler, 2010; Gengler et al., 2010 Gengler et al., , 2012a Toma et al., 2010), graphene, and/or graphene oxide (GO) (Cote et al., 2009; Gengler et al., 2010; Zheng et al., 2011b; Michopoulos et al., 2014), or other carbon-based nanostructures (Bourlinos et al., 2012aBourlinos et al., ,b, 2013) have been used to produce hybrid thin multilayers with unique properties. Clay minerals with amphiphilic species and other complexes were combined to fabricate monolayers and multilayers used as photoprobes (Hagerman et al., 2002), sensors (Junxiang et al., 2005), catalysts (Yoshida et al., 2006), and photomagnetic films (Yamamoto et al., 2004a,b). Moreover, the optoelectronic and mechanical properties of graphene can be modified, tuned, or enhanced by layer-by-layer assembly techniques such as the LB method, as has been reported in various studies over the last 3–4 years (for a review, see ). "
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