Investigations On The Modification Of Nanometer Titanium Dioxide With Ionic Liquids And Its Applications In Protein Isolation And Photocatalytic Degradation

The present thesis thoroughly studied the modifications of environment-friendly nano-TiO2by ionic liquids, another environment-friendly material. The experimental details for the modifications at various conditions are scrutinized. The materials are used for the selective isolation of proteins and photocatalysis of the degradation of methyl orange.In the first part, porous nano-titanium dioxide (TiO2) particles with anatase framework are prepared by using an effective template of hydrophobic ionic liquid, i.e., N, N-bis [2-methylbutyl] imidazolium hexafluorophosphate (PPimPF6). The porous nano-TiO2particles are characterized with TEM and BET, resulting in the distribution of the pore diameters centering at7.3nm and26.2nm, attributed to the template effect of the ionic liquid and the aggregation of the TiO2particles, respectively. A much improved surface area of68.31m2g-1and a pore volume of0.2814cm3g-1are obtained with respect to15.16m2g-1and0.0402cm3g-1achieved by the non-templated nano-TiO2counterpart. The porous nano-TiO2particles are used as adsorbent for selective adsorption and isolation of cytochrome c (cyt-c) at certain conditions. An adsorption efficiency of87%is achieved for150μg mL-cyt-c in1.0ml of sample solution at pH9by using2mg of the porous nano-TiO2particles, in comparison to30%obtained by the non-templated nano-TiO2. In addition, an adsorption capacity of112.6μg mg-1is derived for the porous nano-TiO2with respect to25.1μg mg-1for the normal ones. The absorbed cyt-c can be readily recovered by stripping with a0.1mol L-1Na3PO4solution, giving rise to a recovery of ca.90%. The porous nano-TiO2particles are used for the isolation of cyt-c from human whole blood, achieving satisfactory results by assay with SDS-PAGE. The second part of the thesis reported for the first time a novel one-pot procedure for the synthesis of ionic liquid N, N-bis [2-methylbutyl] imidazolium hexafluorophosphate (PPimPF6)-TiO2nanocomposites. During in-situ formation of the TiO2nanoparticles via hydrolysis of tetrabutyl titanate (TBOT), the ionic liquid PPimPF6is simultaneously bound into the TiO2nanostructure via H-bonding. The PPimPF6/TiO2nanocomposites are characterized by means of TEM, HRTEM, FT-IR and XRD showing that it possesses the structure of anatase without any thermally treatment. Moreover, the ionic liquid plays an important role in the formation of nanocomposites with orientation and structural stability agent. It exhibits selective adsorption for neutral proteins, hemoglobin in this particular case, under well controlled experimental conditions. In a Britton-Robinson buffer of pH8, an adsorption efficiency of88.3%for150p.g mL-1of Hb is achieved using2mg of the PPimPF6/TiO2nanocomposites as sorbent, while virtually no adsorption is observed for basic protein cytochrome c (cyt-c) and acidic protein bovine serum albumin (BSA). An adsorption capacity of122.3μg mg-1is obtained for hemoglobin by calculation based on the amount of the incorporated ionic liquid, corresponding to a5-fold improvement with respect to that achieved by pure PPimPF6. The retained hemoglobin on the PPimPF6/TiO2nanocomposites could be readily collected by stripping with0.5%SDS, giving rise to a recovery of ca.73%. The circular dichroism (CD) spectra indicated no conformational change for hemoglobin after the adsorption/elution processes. The selective isolation of hemoglobin from human whole blood is achieved by the nanocomposites.In the last part, N, N-bis [2-methylbutyl] imidazolium hydroxide (PPimOH)-TiO2nanocomposites are synthesized by using hydrophilic ionic liquid N, N-bis (2-methylbutyl) imidazolium hydroxide (PPimOH) as doping agent. The products are characterized by UV-Vis, XRD, FT-IR and TEM analysis, which is consist of pure anatase particles of about10nm. The ionic liquid PPimOH is bound to the surface of the TiO2nanoparticles by the formation of Ti-O-C bonds rather than by physical adsorption. The doping amount of PPimOH directly relates to the response of the PPimOH-TiO2nanocomposites to visible light. Further investigations showed that at a PPimOH and TBOT molar ratio of3:1, the maximum absorption of the PPimOH-TiO2nanocomposites are shifted into visible light region (400nm), corresponding to a decrease of the band gap from3.1eV to2.25eV. That is to say, the PPimOH-TiO2nanocomposites exhibit favorable response to visible light. It has been demonstrated that it is much more active than pure TiO2under visible-light irradiation in the photocatalytic degradation of methyl orange in aqueous solution. The degradation rate of methyl orange in the presence of the nanocomposites is78%(1.5h).