Titania sol

FIGURE 16.4 Scanning electron micrographs of glassy carbon electrodes coated with (a) titania sol-gel and (b) titania sol-gel doped with HRP (adapted from [35]). 

J. Yu and H.X. Ju, Preparation of porous titania sol-gel matrix for immobilization of horseradish peroxidase by a vapor deposition method. Anal. Chem. 74, 3579-3583 (2002). 

J. Yu, S. Liu, and H.X. Ju, Mediator-free phenol sensor based on titania sol-gel encapsulation matrix for immobilization of tyrosinase by a vapor deposition method. Biosens. Bioelectron. 19, 509-514 (2003). 

J. Yu and H.X. Ju, Amperometric biosensor for hydrogen peroxide based on hemoglobin entrapped in titania sol-gel film. Anal. Chim. Acta 486, 209—216 (2003). 

J. Yu and H.X. Ju, Pure organic phase phenol biosensor based on tyrosinase entrapped in a vapor deposited titania sol-gel membrane. Electroanalysis 16, 1305-1310 (2004). 

A possible structural model for the arrangement of the titania sol particles in the interlayer spaces is schematically shown in Fig. 2 [13]. The basal... 

Yang, W. W., Bai, Y., Li, Y. C. and Sun, C. Q. (2005a), Amperometric nitrite sensor based on hemoglobin/colloidal gold nanoparticles immobilized on a glassy carbon electrode by a titania sol-gel film. Anal. Bioanal. Chem., 382(1) 44-50. 

In a similar approach, titania composites doped with CdSe and CdSe/ZnS NCs were prepared. Here the NCs were mixed with titanimn tetrabntoxide in a 2 1 THF/ethanol solvent system, and volnme fractions as high as 13% were reported in films that were spin-coated from the sol solutions. While QYs for the CdSe/ZnS-titania sols remained near 10%, smaller valnes were reported for CdSe NCs that were not initially overcoated with ZnS. In addition, the samples were not very stable, as the PL intensity was observed to decrease in the films almost immediately following processing. 

Similarly, CdS NCs capped with mercaptopro-pyltrimethoxysilane (MPTMS) were added to alcohohc solutions of TEOS or TMOS and subsequently incorporated into sihca matrices. Pb and Hg-based NCs have also been synthesized with MPTMS as the capping agent, and the role of the pendant siloxy groups is again to anchor the NCs to the sihca, silica-titania, or zirconia networks. Zirconia films doped with PbS NCs were prepared with refractive indices up to 1.53 and a third-order susceptibility value of 1.3 X 10 esu. Higher refractive index sihca-titania sol gel films doped with PbS (n = 1.63) were also fabricated. ... 

Particle aggregation during and after the synthesis of the sol can have a significant effect on the properties of the resulting ceramic membrane. Figure 1 illustrates the effect of aging on particle size for titania sols prepared with different H20/Ti mole ratios, using 2-methyl-2-butanol (t-amyl alcohol) as the solvent. 

Effect of acid concentration on particle size of a titania sol... 

Yoneyama et al. [142, 143] formed Ti02 pillars with thickness of about 1.5 nm in the galleries of montmorillonite by intercalation of titania sol followed by decom-... 

In 2003, Dai et al. [80] reported a strategy for a reagentless immunosensor for the determination of carcinoma antigen-125 (CA-125) based on the immobilization of antigen and the direct electrochemistry of HRP bound to an antibody. The immunosensor was prepared by immobilizing CA-125 with titania sol-gel on a GCE by the vapour deposition method. The incubation of the immunosensor in phosphate buffer solution containing HRP-labelled CA 125 antibody leads to the formation of an HRP-modified surface. The immobilized HRP displays its direct electrochemistry with a rate constant of 3.04 1.21 s . With a competition mechanism, a differential pulse voltam-metric determination method for CA-125 was established by the peak current decrease of the immobilized HRP. The current decrease resulted from the... 

Titania sol and gel prepared through the hydrolysis of tetrabutyl titanate in acid water solution are sensitive to ultraviolet (UV) irradiation and turn into blue color [137]. Electron spin-resonance measurement showed that the pho-tochromism was ascribed to the presence of titanium (III) ions in the Ti-O-Ti network. The titanium (III) ions could be oxidized by the oxygen in the atmosphere, and then the sol and gel faded slowly. The absorption peaks in the optical absorption spectra of the titania gel were attributed to the transition of 3-dimensional electrons of a trivalent titanium in certain environments. 

A dispersion of solids can be prepared by dispersing a powder in a liquid or by synthesising the solid particles in situ in a liquid. Examples of the first method are suspensions of submicrometer alumina or zirconia powders in water. Examples of the second method are boehmite sols and titania sols prepared from organo-metallic precursors. ... 

The preparation of titanias and precipitated titania/aluminas using complexing agents enables a systematic control of their pore structures. This method is effective not only for modification of titanium alkoxide which is used as a titania precursor but also for modification of titania sol. 

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