Study On Preparation And Photoelectric Characteristics Of Lanthanide-Doped Ordered Macroporous Nano-TiO₂Film

In this thesis, the polymethylmethacrylate （PMMA） microspheres weresynthetized firstly by using the soap-free emulsion polymerization method.The optimal experimental program to prepare the monodispersepolymethylmethacrylate （PMMA） microspheres was obtained by using theorthogonal design, which was listed here. The concentration of the monomerwas1.75mol/L and the one of the initiator was2.06mmol/L. The reactiontemperature was set at75℃and the reaction time was10h. When dipped for4min and pulled at30mm/min, the PMMA template with the averageparticle diameter of473.9nm was obtained.The best experimental program to prepare the TiO2precursor sol wasobtained by using the orthogonal design and the mole ratio of thase foursolutions was nTi（OC4H9）4: nC2H5OH: nH2O: nCH3COOH=1:20:2:0.9. Thelanthanum-doped of0.5%（molar ratio） ordered macroporous TiO2film wasprepared when PMMA samples with the average particle diameter of473.9nm was designed as the template. The optimum heat treatment process was asfollows. The samples were heated to500℃at a rate of2℃/min and held fortwo hours. The morphology of the samples was observed by the field emissionscanning electron microscope. The results showed that the more orderlymacroporous films were obtained with the Lanthanum-doped. The crystallinephase was analysed and the grain size was calculated by using the X-raydiffractometer （XRD）. The results indicated that the transformation of TiO₂anatase to rutile was restrained and the grain is refined with the doping oflanthanum. It was found that the specific surface area of lanthanum-dopedsample increased significantly and the one of film specimen was furtherincreased compared with that of the powder samples. The increase of thespecific surface area indicated that the grain size of the sample decreases andthis result is verified mutually with the result of XRD. The heat treatmentprocess parameters were obtained through the differential thermal （DSC-TG）analysis to the samples. The electron transition and lattice vibration modewere characterized by photovoltage （SPV）, Laser Raman andUltraviolet-Visible （UV-VIS） spectroscopy. The experimental results showedthat a strong surface photovoltaic response with a wide range was obtainedwith the lanthanum doping.The surface band structure, partial density of states and optical properties were calculated by using Materials Studio software for the （101）plane of TiO₂anatase as well as the adsorbed water and ethanol molecules ofthe （101） plane of lanthanum-doped anatase. The results showed that theband gap of （101） plane of anatase became narrowed, the absorption peaksshifted towards blue and the absorption coefficient improved significantlywith the lanthanum-doped. The different adsorption materials had significanteffect on the band structure and optical properties of （101） plane oflanthanum-doped anatase.