Assemblying And Property Studies Of Dye Molecules/Layered Double Hydroxides Composite Films

The photophysical and photochemical properties of intercalation compounds of layered hosts and chromophors are the subject of recent papers and reviews. The topic is of considerable interest because of the potential applications of these intercalation compounds in photophysical devices and in nonlinear optics. The preparation of intercalation compounds with anionic dyes requires the use of host-layered compounds with positively charged layers, such as layered double hydroxides(LDHs). LDHs is an anion clay, it has a good anion-exchange property, many reports about the intercalation of organic anions such as surfactants, large polyoxometalates, and various functional molecules have been published. The research of dyes/LDHs nanocomposites or composite film materials not only have theoretic meaning, but also have potential application in preparing new kinds of functional material with novel properties and a candidate to act as sensors, optical storage devices. In this study, we prepared [Mg-Al-Cl]LDHs by a non-steady coprecipitation, and studied its property of ion exchange by preparing dyes/LDHs nanocomposites. Moreover, the composite films of arachidic acid/layered double hydroxides/dyes(Methyl Orange, MO and Congo Red, CR)[abbreviated as AA/LDHs/Dyes hereafter] have been fabricated by a combination of the Langmuir-Blodgett method and ion intercalation techniques. The structural properties of the composite films are characterized by π-A isotherm, UV-Vis spectra, FTIR spectra, LAXRD, polarized UV-Vis spectra.1. Studies on the Preparation and ion-exchange properties of LDHsCurrently, LDHs has attached more and more attention, because it is the only one of layered material, which can be used as an intercalation host material. It presents the advantage of a large variety of compositions and a turnable layer charge density, its sheets are constituted of one polyhedra-made layer and are more flexible than other bidimensional frameworks such as the 2:1 layered silicate. In this chapter, the [Mg-Al-Cl]LDHs was prepared by non-steady coprecipitation. The production was characterized by AFM, XRD, and IR. The results showed that the [Mg-Al-Cl]LDHs had good layered structure. AFM analysis revealed that the shape of [Mg-Al-Cl]LDHs was hexagonal particles, approximately 100-200nm long, and 5nm thick.The ion exchange property of LDHs was studied by the intercalation reactions between the LDHs and functional dye molecules(MO and CR). The XRD and 1R results showed that dye molecules could be intercalated into the gallery of LDHs, and organic-inorganic nanocomposites were obtained.2. Assemblying and characterization of arachidic acid/layered double hydroxides/dyes composite filmsIn recent years, the technological interest should be the LDHs/dyes systems with ordered and constrained structure, in solid-state. As we know, the Langmuir-Blodgett (LB) method provides a novel technique to assemble molecular ordered multilayer films. It is easy to control the sequence of the layers in the multilayer at molecular level. In this paper, we fabricated the arachidic acid/layered double hydroxides/dyes (MO and CR) composite films by a combination of the Langmuir-Blodgett method and ion intercalation techniques, and studied their structural characteristics and spectra properties by TEM, UV-Vis spectra, Polarized UV-Vis spectra, XRD and IR spectra.The results of π-A isotherms and TEM images showed that AA molecules hybridized with LDHs particles at the air-water interface, and formed stable and uniform floating monolayer. The composite films showed the better layered periodicity and the uniformity in the vertical direction. The MO and CR molecules could be intercalated into the AA/LDHs hybrid films with an ion-exchange mechanism. The MO molecules almost stand vertically in the gallery of the LDHs forming H-aggregates and the CR molecules almost lie flatly on the layer surface in the LDHs forming J-aggregates. Due to the rigid layered structure of LDHs, the dyes intercalated into the hybrid films had a better conformational stability in the UV-radiation. With this property, we can prepare varieties of functional nanocomposites.