Preparation and Photophysical Properties of Chromophores Pillared Mg-Al-LDH

Ethyl orange(EO-) and 4-aminoazobenzene-4-sulfonic anion(4A-) were intercalated into the layered double hydroxide(LDH),[Mg 0.66 Al 0.34(OH) 2](CO3) 0.17.0.67H2O or exchanged on the external surface of the host by the method of ion-exchange procedures.The obtained compounds were characterized by X-ray diffraction,in-frared and thermogravimetry techniques.The photophysical properties of the obtained compounds were studied by UV-Vis absorption and fluorescence spectroscope.The guest molecular sizes and structures were investigated util-izing an ab initio(HF/6-31G) method by G03w.These anions were arranged in the interlayer space as a monolayer of species with the main axis perpendicular to the layer plane.These results indicated that the fluorescence of in-tercalated sample of Mg-Al-EO-LDH increased greatly due to a more rigid and constrained environment of the host.However,the fluorescence of intercalated sample of Mg-Al-4A-LDH decreased due to the concentration quenching.Compared with those observed in the pure microcrystalline EO and 4A,the fluorescence intensity of the samples containing only surface-exchanged EO or 4A reduced because the charge transfer between EO or 4A molecules was enhanced.It suggests that the photophysical properties of guests can be changed by the guest-host interaction or guest-guest interaction.