| The intercalation and exfoliation reactions of α-zirconium phosphate, Zr(HPO4)2.H2O (α-ZrP), were studied microscopically by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The reaction of α-ZrP with tetra( n-butylammonium) hydroxide (TBA+OH−) initially produces intercalation compounds, which then separate into unilamellar colloids. A hydrolysis reaction of α-ZrP colloids proceeds from the edges inwards, forming ∼4 nm zirconia particles that decorate the edges of the sheets. The hydrolysis reaction is negligible at 0°C, which permits the synthesis of hydrolysis-free unilamellar colloids. These colloids form monolayer films on amine-derivatized silicon surfaces with a high density that suggests significant surface mobility during the adsorption process.; Multilayer organic/inorganic thin films containing fluorescent probe molecules were assembled on planar glass substrates by sequentially adsorbing monolayers of poly(allylamine hydrochloride) derivatized with fluorescein or rhodamine B, and exfoliated α-ZrP. Different donor-acceptor geometries were prepared by changing the placement and number of α-ZrP and PAH layers separating the fluorescein/PAH and rhodamineB/PAH layers. A Monte Carlo simulation of the Förster energy transfer process in each geometry was compared with the energy transfer efficiency determined from steady-state luminescence spectra. Near-field scanning optical microscopy was used to obtain localized measurements of the energy transfer from RhB-PAH to Texas Red derivatized PAH (TR-PAH).; The construction of more complex systems, which perform multi-step energy/electron transfer reactions, is described. By using three complementary chromophores, excitation is collected from a substantial fraction of the visible spectrum and funneled to a trap molecule that forms a long-lived triplet excited state. This trap molecule then transfers an electron to an acceptor in the next layer. The charge separation quantum efficiency and lifetime can be significantly increased by replacing α-ZrP with the active spacer HTiNbO5, an oxide semiconductor. In this case, there is a five-component energy/electron transfer cascade in which there are no covalent bonds between any of the photo- or redox-active components. |
