Hydrophobic Titanium Research Articles

Arrangement of Conductive TiO2 Nanoparticles in Hybrid Inorganic/Organic Thermosetting Materials Using Liquid Crystal

Novel thermoresponsive hybrid inorganic/organic thermosetting materials based on hydrophobic titanium dioxide nanoparticles and amphiphilic poly(styrene-b-ethylene oxide) block-copolymer-dispersed 4′-(hexyl)-4-biphenyl carbonitrile liquid crystals were prepared and characterized. The obtained results confirm that these multiphase materials maintain thermo-optical properties of incorporated liquid crystals and show good dispersion of the titanium dioxide, which the microphase separated within the HBC/PS-block. Moreover, well-dispersed nanoparticles spontaneously form well-defined highly dense arrays of titania nanodots located in the interface between the epoxy matrix and the microphase-separated HBC/PS-block, which, combined with the fact that TiO2 nanoparticles maintain their conductive properties in the investigated systems, can lead to the generation of novel materials with interesting specific properties.

Efficient adsorption and photocatalytic degradation of organic pollutants diluted in water using the fluoride-modified hydrophobic titanium oxide photocatalysts: Ti-containing Beta zeolite and TiO 2 loaded on HMS mesoporous silica

Using the F − media, the hydrophobic zeolite and mesoporous silica can be synthesized. These hydrophobic porous materials exhibit the high ability for the adsorption of organic compounds diluted in water and become the useful supports of photocatalyst. The hydrophobic Ti-Beta(F) zeolite prepared in the F − media exhibited high efficiency than the hydrophilic Ti-Beta(OH) zeolite prepared in OH − media for the liquid-phase photocatalytic degradation of 2-propanol diluted in water to produce CO 2 and H 2O. The TiO 2 loaded on the hydrophobic mesoporous silica HMS(F) (TiO 2/HMS(F)), which was synthesized using tetraethyl orthosilicate, tetraethylammonium fluoride as the source of the fluoride and dodecylamine as templates, also exhibited the efficient photocatalytic performance for the degradation. The amount of adsorption of 2-propanol and the photocatalytic reactivity for the degradation increased with increasing the content of fluoride ions on these photocatalysts. The efficient photocatalytic degradation of 2-propanol diluted in water on Ti-Beta(F) zeolite and TiO 2/HMS(F) mesoporous silica can be attributed to the larger affinity for the adsorption of propanol molecules on the titanium oxide species depending on the hydrophobic surface properties of these photocatalysts.

Implantation of hydrophilic and hydrophobic titanium discs in rat tibia: cellular reactions on the surfaces during the first 3 weeks in bone

In a previous study, a method for evaluation of short-time (1–8 days) healing of titanium implants in rat tibiae was described (J. Biomed. Mater. Res. 66A(3) (2003) 662). The implants were disc-shaped and cells and tissue on the surface were investigated, not the adjacent tissue. In this study healing during the first 3 weeks in bone was examined and the healing response between hydrophilic and hydrophobic titanium was compared. Immunofluorescence techniques were used to detect signs of bone formation on the surfaces. Cell viability, alkaline phosphatase (ALP) activity, presence of osteocalcin and cells positive for bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF) were investigated. Both viable and non-viable cells were found on both surfaces during the first week. Only initially was there a difference between them; 4% viable cells on hydrophilic discs compared to 56% on hydrophobic ones. More BMP-2 positive cells were found on hydrophilic discs than on hydrophobic ones after 1 week. VEGF was detected after 8 days on both surfaces. Osteocalcin positive cells were found from 2 weeks. ALP positive cells were found after 8 days, while at 2–3 weeks ALP positive tissue was abundant on both surfaces. In conclusion, signs of bone formation were detected during the period investigated. Surface energy appeared to be of more importance initially, with higher surface energy resulting in more rapid cell activation and differentiation than lower.

Thrombin, kallikrein and complement C5b-9 adsorption on hydrophilic and hydrophobic titanium and glass after short time exposure to whole blood

Hydrophilic and hydrophobic titanium and glass were exposed to capillary whole blood between 5 s and 24 h. The time-sequence for adsorption of thrombin, kallikrein and complement C5b-9, and their relationship with adherent platelets and polymorphonuclear granulocyte (PMN) activation were investigated. Adsorbed thrombin and kallikrein were measured by cleavage of specific chromogenic substances, S-2238 and S-2303, respectively. Complement C5b-9 and expression of CD11b, CD66b, CD62P and Pan-platelets were measured by immunofluorescence. Thrombin and kallikrein were present on the surfaces during the whole investigated periods. Platelet adhesion and PMN cell adhesion and activation on all surfaces and activation of platelets on hydrophobic surfaces showed a similar pattern to thrombin adsorption. Kallikrein adsorption had a different pattern on each surface. C5b-9 was detected between 32 min and 24 h of blood exposure and a varying pattern of C5b-9 coverage was observed on each surface. In conclusion, our results indicate that the interaction between material and blood coagulation and kinin-activating proteins regulate the adhesion and activation of blood cells, whereas after longer time the coagulation and kallikrein-kinin system play minor roles and the complement system is decisive for mediating and elongating the inflammatory process.

Ammoximation of ketones catalyzed by titanium-containing ethane bridged hybrid mesoporous silsesquioxane.

The first example of ammoximation of bulky ketones over highly hydrophobic titanium incorporated ethane bridged hybrid mesoporous silsesquioxane with high selectivity of oximes is presented.

Role and effect of supercritical fluid extraction of template on the Ti(IV) active sites of Ti-MCM-41

Supercritical fluid (supercritical carbon dioxide mixed with methanol) has been used as an extraction medium for the removal of template for a series of titanosilicates. Mesoporous titanosilicates Ti-MCM-41 with variable Si/Ti ratio (200–25) have been prepared by hydrothermal method. The location and coordination of titanium in the calcined and extracted titanosilicate mesoporous molecular sieve was studied by FTIR, UV–Vis spectroscopy, photoluminescence spectra, 29Si NMR, combined with XRD and TG/DTA. Up to 97% template can be removed by extraction and the extracted material are hydrophobic in character. Removal of template by supercritical fluid extraction have no effect what so ever on the elemental composition of Ti-MCM-41 as well as it improves the structural ordering which was confirmed by XRD. Unequivocal evidences are presented to confirm the presence of same chemical environment of active titanium site after extraction, as present in as-synthesized material. It was also reported that, the entire extracted solid exhibited catalytic activity superior to that of the calcined product for epoxidation of cyclohexene because of the hydrophobic character and unchanged active framework titanium site.

Rheology of fumed hydrophilic and hydrophobic titania suspensions dispersed in silicone oils

The rheological properties of fumed titania particles suspended in various silicone oils were investigated by steady-state viscosity measurements as functions of titania contents and surface properties of the fumed titania particles. Adsorption behavior of the silicone oils and optical microscopy observation were also examined. When the fumed hydrophilic titania particles were dispersed in the silicone oils, the larger amounts of the silicone oils were adsorbed on the titania particles, the larger flocculated structures were formed, and the stronger shear thinning behavior was observed, as compared to the fumed hydrophobic titania suspensions. The difference should be mainly attributed to the interaction between the titania surface and the silicone oils. The relative viscosities of the fumed titania suspensions at the same titania concentration could be superimposed on the master curve by taking into account the Peclet number, irrespective of the silicone oil.

Study of the Effect of External Additives on Toner Performance

External additives for toners such as hydrophobic fumed silica and hydrophobic titania have been widely used for improvement of toner performance. Toners formulated for use in laser printers and PPC (Plain Paper Copiers) are being developed, aimed at high speed copying, high image quality and downsizing. To meet the challenges of more demanding requirements, toners are designed utilizing both smaller and larger particle size external additives to achieve better flowability, higher durability, higher image density and stable electrostatic charge under ambient conditions. Usage levels are also increasing. In addition to improved overall toner flow and charge properties, this trend is associated with improving cleaning properties such as reduced fogging and adherence of toner to paper.As such properties can be influenced by external additives, it is important for the toner formulator to know which characteristics need improvement in the already design stage.This paper describes the design and the selection of external additives. It will address the influence of mixing time of external additives on the tribo-electrostatic charge (T-ESC), charge distribution, and flowability of toners. In addition, the influence of surface chemistry of external additive on the admix performance is discussed. Finally, experimental results of the performance of color toner mixed with several kinds of external additives are reported.

Polymorphonuclear leukocytes in coagulating whole blood recognize hydrophilic and hydrophobic titanium surfaces by different adhesion receptors and show different patterns of receptor expression

The mechanism of healing or rejection of implant materials is unknown, but the process always starts at the contact with coagulating blood. Here, the initial reactions of clean (hydrophilic) and alkylated (hydrophobic) titanium with blood were investigated by short-term exposure to human blood and detection of polymorphonuclear leukocyte (PMNL) surface antigens with an immunofluorescence technique. The fluorescence intensity was quantitated by computer-aided image analysis. Antibodies specific to CD11b, CD16, CD18, CD62L, and CD162 were used to block PMNL adhesion. The respiratory burst of adhering cells was stimulated with opsonized zymosan and measured by chemiluminiscence. The thrombin dependence of PMNL reactions was studied by using hirudin, a specific thrombin inhibitor. The expression of CD62L decreased with increasing exposure time, and the rate of decrease was faster at the hydrophilic surface. At the hydrophilic surface, the CD16 exposure was high after 8 minutes of blood contact, and it decreased with time. At the hydrophobic surface, a peak in CD16 expression was seen after 32 minutes of blood exposure. At the hydrophobic surface, the expression of CD11b increased slowly with increasing blood exposure time, whereas at the hydrophilic surface, a peak of CD11b expression was seen after 32 minutes of blood exposure. The expression of CD11b and that of CD16 were found to be thrombin dependent. At the hydrophilic surface, adhesion of PMNLs was blocked by CD16 antibodies, whereas adhesion to the hydrophobic surface was blocked by anti-CD162. Mixing blood with antibodies to CD11b, CD18, and CD62L amplified the adhesion of PMNLs to the hydrophilic surface. (J Lab Clin Med 2001;137:296-302)

Respiratory burst response of peritoneal leukocytes adhering to titanium and stainless steel.

Titanium sheets, made hydrophilic by oxidative cleaning or hydrophobic by treatment with butanol, and stainless steel sheets with different patterns of pores (straight phi = 0.8 mm) were implanted into the peritoneal cavity of mice. The implants were removed after 2 h, and the surface-adhering leukocytes were stained with propidium iodide and fluorescein diacetate to quantitate cell adhesion and to indicate the presence of leaks in the cell membrane. The ability of the surface-adhering leukocytes to mount a respiratory burst response after stimulation with PMA or zymosan was measured by chemiluminiscence. The results show that stainless steel without pores induces membrane leakage in 80% of the surface-adhering leukocytes compared with 65% of cells adhering to porous steel. Hydrophilic titanium induces membrane leakage in 48% of the surface-adhering leukocytes compared with 19% of cells adhering to hydrophobic titanium. The respiratory burst response of the surface-adhering leukocytes stimulated with PMA was attenuated on stainless steel and hydrophilic titanium compared with hydrophobic titanium. Thus, butanol treatment of titanium and pores in stainless steel increase the biocompatibility of the materials.

Reusable adsorbents for dilute solution separation. 4: Adsorption of 1,2 dichlorobenzene and phenanthrene on a surfactant-modified semiconductor (titania) surface

The surface of a semi-conducting surface, viz., titania was modified by adsorbing an anionic surfactant, viz., sodium dodecyl sulfate (SDS) at aqueous pH values less than the point of zero charge of 6.8. The hydrophobic titania surface was capable of adsorbing hydrophobic organic compounds, such as 1,2-dichlorobenzene and phenanthrene at dilute concentrations from the aqueous phase. The adsorption partition coefficients for both compounds on SDS hemi-micelles on TiO2 are of magnitudes similar to their octanol–water partition constants, which are indicators of similar hydrophobic environments. The potential uses of SDS-coated TiO2 for simultaneously adsorbing and photo-chemically degrading hydrophobic organic compounds as a means of treating dilute wastewater streams are suggested.

Encapsulation of inorganic particles via miniemulsion polymerization. I. Dispersion of titanium dioxide particles in organic media using OLOA 370 as stabilizer

The dispersion of hydrophilic and hydrophobic titanium dioxide (TiO2) particles in organic media (styrene and cyclohexane) was studied to evaluate the effect of dispersion quality (i.e., size and stability) on the encapsulation efficiencies of subsequent miniemulsion polymerizations. Through screening studies of various block copolymers, OLOA 370 (polybutene–succinimide pentamine) was chosen as the stabilizer for detailed dispersion studies on both types of TiO2 particles. As a result of strong interactions between the amine end group of the OLOA 370 stabilizer and the hydroxyl groups on the surface of the hydrophilic TiO2 particles, a good dispersion stability and small particle size (Dv = 39–45 nm) was obtained using 1.0 wt % stabilizer and 20 min of sonification. The dispersions of the hydrophobic TiO2 particles resulted in a larger average particle size (Dv = 60 nm) and poorer stability. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4419–4430, 2000

Hydrophobic titania–silica aerogels: epoxidation of cyclic compounds

Titania–silica mixed oxides with covalently bound methyl or phenyl groups were prepared from the corresponding alkyltrimethoxysilane and tetramethoxysilane using a sol–gel process and ensuing low-temperature supercritical extraction with CO2. Prehydrolysis of the organically modified silicon precursor was applied to compensate for their lower sol–gel reactivity compared to the precursors of the other constituents. Trihexylamine was used as a gelation catalyst. The dominantly mesoporous aerogels were characterized by thermal analysis, N2 adsorption, infrared spectroscopy, 29Si- and 13C-NMR spectroscopy, and transmission electron microscopy. Thermal analysis and 29Si MAS NMR measurements indicated covalent incorporation of the modifying group. 13C NMR spectra confirmed the integrity of the incorporated modifying groups. The materials were tested in the epoxidation of cyclohexene and cyclohexenol with tert-butylhydroperoxide. NH3 adsorption studied by DRIFT spectroscopy indicated no significant acidity of the aerogel surfaces, which was traced to the use of trihexylamine as gelation catalyst. Addition of zeolite 4 A or NaHCO3 did not improve the performance of the unmodified and phenyl-modified aerogel, corroborating the suppressed acidity of the surface. Interestingly, the phenyl-modified aerogel was more selective in the epoxidation of cyclohexenol, when using polar solvents (ethanol or acetone), compared to the reaction in toluene.

Adsorption of metal ion and aromatic compounds by anionic surfactant-coated particles of titanium dioxide

Adsorption of Cu 2+ and 2-naphthol from aqueous solutions was examined by anionic surfactant (sodium dodecyl sulfate, SDS) adsorbed on titanium dioxide. Two types of titanium dioxide were used; one was untreated and the other was hydrophobic with dodecyl chain groups. At pH 3, 4 and 5, the adsorption of Cu 2+ increased with increasing SDS concentration and then decreased slightly on untreated titanium dioxide; the adsorption of Cu 2+ decreased in a following order, pH 5>pH 4>pH 3. The adsorption behavior of Cu 2+ by the SDS adsorbed on hydrophobic titanium dioxide was similar to that on untreated titanium dioxide, although the amount of SDS adsorbed on the former was half as that on the latter. This difference derives from different adsorption states of SDS. In addition, simultaneous adsorption of Cu 2+ and 2-naphthol on both untreated and hydrophobic titanium dioxides by addition of SDS was performed at pH 5; the amount of Cu 2+ adsorbed was almost the same as those without 2-naphthol for both titanium dioxides and the amount of SDS adsorbed was enhanced in the presence of 2-naphthol where 2-naphthol was adsolubilized more efficiently in the SDS adsorbed layer on hydrophobic titanium dioxide than on untreated titanium dioxide. This anionic surfactant-adsorbed layer can remove both metal ions and the nonionic aromatic compound simultaneously.

Zeolite Titanium Beta: A Selective Catalyst for the Gas-Phase Meerwein–Ponndorf–Verley, and Oppenauer Reactions

Aluminium-free zeolite titanium beta was tested in the Meerwein–Ponndorf–Verley reduction of 4-methylcyclohexanone with various secondary and primary alcohols as hydrogen donors, using a fixed-bed continuous-flow gas-phase reactor. A high selectivity towards the thermodynamically unfavourablecis-4-methylcyclohexanol was observed, which is ascribed to transition-state selectivity in the straight channels of zeolite beta. However, in the gas-phase, the selectivity to thecis-alcohol is significantly lower than in the liquid-phase when using 2-propanol as the hydrogen donor. Based on kinetic and adsorption experiments, it is concluded that the concentration of alcohol reductant in the zeolite is an important parameter in determining selectivity. More hydrophobic alcohols give rise to an increased selectivity to thecis-alcohol product. From the sorption experiments it was concluded that this is due to a higher internal concentration of the alcohol reductant in the hydrophobic titanium beta zeolite. The observed selectivities and activities are consistent with a mechanism in which this alcohol is not only the hydrogen donor but is also required to remove thecis-alcohol product formed from the catalytic site by alcoholysis, before consecutive reactions can take place.

Zeolite Titanium Beta*1A Selective Catalyst for the Gas-Phase Meerwein–Ponndorf–Verley, and Oppenauer Reactions

Abstract Aluminium-free zeolite titanium beta was tested in the Meerwein–Ponndorf–Verley reduction of 4-methylcyclohexanone with various secondary and primary alcohols as hydrogen donors, using a fixed-bed continuous-flow gas-phase reactor. A high selectivity towards the thermodynamically unfavourablecis-4-methylcyclohexanol was observed, which is ascribed to transition-state selectivity in the straight channels of zeolite beta. However, in the gas-phase, the selectivity to thecis-alcohol is significantly lower than in the liquid-phase when using 2-propanol as the hydrogen donor. Based on kinetic and adsorption experiments, it is concluded that the concentration of alcohol reductant in the zeolite is an important parameter in determining selectivity. More hydrophobic alcohols give rise to an increased selectivity to thecis-alcohol product. From the sorption experiments it was concluded that this is due to a higher internal concentration of the alcohol reductant in the hydrophobic titanium beta zeolite. The observed selectivities and activities are consistent with a mechanism in which this alcohol is not only the hydrogen donor but is also required to remove thecis-alcohol product formed from the catalytic site by alcoholysis, before consecutive reactions can take place.

Initial reactions of whole blood with hydrophilic and hydrophobic titanium surfaces

Commercial sheet titanium was annealed in air at 700–800°C. The hydrophilic, annealed sheets were immersed in sterile distilled water and stored until use. The hydrophilic titanium was made hydrophobic by ultrasonication in water-saturated 1-butanol (1:10) for 30 min, followed by rinsing in absolute ethanol and water. The titanium surfaces were exposed to capillary blood for 5 s. Immobilised plasma proteins and cells were detected with immunofluorescence by specific, fluorescein-labelled antibodies. Quantitation of labelled antigen was made with computer-aided image analysis. Two distinct patterns of blood reactions were seen. On the hydrophobic surface, signals from anti-fibrinogen antibodies were dominant and large amounts of adhering platelets were seen. On the hydrophilic surface, signals from antibodies against complement factor C1 and prothrombin/thrombin were dominant and only a few platelets were found adhering to the surface. The results are discussed in relation to similar findings on hydrophilic and hydrophobic quartz glass surfaces.