Amorphous titania modified with boric acid for selective capture of glycoproteins

Amorphous titania was modified with boric acid, and the resulting material was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction and X-ray photoelectron spectrometry. The new material, in contrast to conventional boronate affinity materials containing boronic acid ligands, bears boric acid groups. It is shown to exhibit high specificity for glycoproteins, and this was applied to design a method for solid phase extraction of glycoproteins as shown for ribonuclease B, horse radish peroxidase and ovalbumin. Glycoproteins were captured under slightly alkaline environment and released in acidic solutions. The glycoproteins extracted were detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The binding capacities for ribonuclease B, horse radish peroxidase and ovalbumin typically are 9.3, 26.0 and 53.0 mg ? g^?1, respectively. The method was successfully applied to the selective enrichment of ovalbumin from egg white.

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Graphical abstract Schematic presentation of the capture of glycoproteins by amorphous titania modified with boric acid.

     

Photoinduced oxidation of benzhydrol over lanthana modified sol-gel titania

Lanthana modified sol-gel titania is prepared through particulate sol-gel route and the physico-chemical characterizations of the prepared systems were done using X-Ray diffration, EDX, BET surface area-pore volume measurements and TG-DTG analysis. Benzophenone was observed to be the sole product in the TiO₂ photocatalyzed oxidation of benzhydrol in oxygen purged acetonitrile. The influence of various parameters, like irradiation time, amount of catalyst, concentration of the catalyst and other factors on the photocatalytic oxidation has been investigated. The proposed mechanism envisages the involvement of a superoxide radical anion.     

Organic pigment particles coated with titania via sol-gel process

This paper presented a novel method for the organic pigment coated with titania to improve the weatherability and dispersion ability in waterborne system. The organic pigment was first orderly adsorbed by two kinds of electrolyte: poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC), then coated by titania via sol-gel process from titanium n-butoxide (TBOT). The effects of the numbers of polyelectrolyte layer, water content, and TBOT content on the morphology, particle size, surface element composition, porosity and pore size, thermal stability, and UV shielding property of the organic pigment were systematically investigated. It was found that only two layers of electrolyte adsorption and one-step coating of titania could obviously enhance the UV shielding property even thermal stability of the organic pigment. The thickness of the titania layer could be easily tailored by TBOT content.     

Platinum acetylacetonate effect on sol-gel derived titania catalysts

The band gap (Eg) of sol-gel derived titania has been determined using UV-Vis spectroscopy. When platinum acetylacetonate was added during titanium tetrabutoxide gelation, a significant diminution of the band gap was observed. Low Eg values were stabilized on heat-treated platinum/titania samples.     

The promotion effect of titania nanoparticles on the direct electrochemistry of lactate dehydrogenase sol-gel modified gold electrode

The promotion effect of titania nanoparticles (nano-TiO(2)) on the direct electron transfer between lactate dehydrogenase (LDH) and the silica sol-gel modified gold electrode was investigated by adding nano-TiO(2) (50 nm) in the modification process. This nano-TiO(2)-LDH electrode showed a pair of quasi-reversible cyclic voltammetry peaks with the formal potential of 70 mV (vs. SCE). Compared to the previous result of LDH modified electrode with only an irreversible cathodic peak, an anodic peak appeared and the cathodic peak potential shifted to the positive direction on this nano-TiO(2)-LDH electrode, which demonstrated that the direct electrochemistry of LDH was enhanced by nano-TiO(2). We supposed that the direct electrochemistry of LDH may be due to the redox reaction of some electroactive amino acids in the LDH molecule. The surface morphologies of electrodes characterized by SEM indicated that LDH was successfully immobilized on the sol-gel matrix and also had some interactions with nano-TiO(2). This electrode can be used as a biosensor for the determination of lactic acid. The calibration range of lactic acid was from 1.0 to 20 micromolL(-1) and the detection limit was 0.4 micromolL(-1). Meanwhile, the small K(m)(app) value (2.2 micromolL(-1)) suggested that LDH possessed high enzymatic activity and good affinity to lactic acid owing to the promotion effect of nano-TiO(2).     

溶胶-凝胶基质修饰的镉离子选择性电极

一种以CdS为活性物质,用溶胶 凝胶技术制作的新型镉离子选择性电极。电极的斜率为29mV/decade,线性范围为1.0×10-1～6.0×10-5mol/L,检测下限为4.5×10-5mol/L,适宜的pH3.2～5.9,并对回收率进行了测定。     

Direct modification with tungstophosphoric acid of mesoporous titania synthesized by urea-templated sol-gel reactions

A series of mesoporous titania materials modified with tungstophosphoric acid (TPA) were successfully synthesized by using urea as low-cost template via sol-gel reactions, followed by removing the urea by extraction with water. They were characterized by FT-IR, 31P MAS-NMR, XRD, DTA-TGA, DRS, TEM and BET. The samples presented mesopores with a diameter higher than 3.0 nm. The S(BET) of the solids decreases with the increase of the TPA content and with the increase of the calcination temperature. According to FT-IR and 31P MAS-NMR studies the main species present in the samples is [PW12O40]3- anions, which was partially transformed into [P2W21O71]6- and [PW11O39]7- anion during the synthesis and drying step. The XRD patterns of the modified samples only exhibited the characteristic peaks of anatase phase. The presence of TPA retarded the crystallization of the anatase phase and its transformation into rutile phase. The point of zero charge decreased in parallel with the increment of tungstophosphoric acid in the samples and with the increase of the calcination temperature. The band gap energy decreased as a result of the introduction of TPA into the TiO2 matrix, but remained practically constant with the increase of the calcination temperature.     

Effect of phosphate ions in the properties of titania sol-gel

Sol-gel titania was phosphated in two different ways: i) “in situ” phosphation using phosphoric acid as hydrolysis catalyst in the titanium butoxide gelling system, and ii) gelling with nitric acid and impregnation with ammonium phosphate solution. In calcined samples at 600°C a positive effect on the specific surface area for the “in situ” phosphated sample was found. X-ray diffraction patterns showed that the presence of phosphates ions stabilized the anatase phase. FTIR-pyridine adsorption identified only Lewis acid sites in phosphated samples. In the isopropanol decomposition for “in situ” phosphated titania, the activity was six times higher than that obtained for titania phosphated by impregnation, showing strong acidity for the in situ phosphated TiO₂ catalyst.     

Molecular imprinting in ultrathin titania gel films via surface sol-gel process

Recent progresses of molecular imprinting in metal oxide matrices were summarized. Application of the surface sol-gel process to mixtures of organic carboxylic acids and titanium alkoxide provides ultrathin layers of titania gel (10-20 nm thick), in which molecule-sized cavities are kept intact upon removal of the organic templates. The imprinted cavity reflects the structural and functional features of the template molecule, and the enantioselective imprinting of dipeptide isomers is observed. Robustness and flexibility of the ultrathin titania layer is demonstrated by the formation of interconnected titania hollow structures. Possible practical applications and unsolved problems of this technique are discussed.     

Ternary luminescent lanthanide-centered hybrids with organically modified titania and polymer units

Nicotinic acid (NA) is grafted to titanium alkoxide to achieve functional precursor Ti-NA, which then is coordinated to lanthanide ions (Tb³⁺/Eu³⁺) to prepare the binary titania hybrid materials Ti-NA-Eu/Ti-NA-Tb via a sol–gel process in the presence of water. Furthermore, two types of ternary titania hybrid materials, Ti-NA-Ln-PMAA/Ti-NA-Ln-PVP, are assembled by the introduction of the organic polymers polymethacrylic acid (PMAA)/polyvinylpyrrolidone (PVP) into the above system. The FTIR spectra of these titania hybrid materials confirm their basic composition, and the X-ray diffraction patterns reveal that they are amorphous. Luminescence spectra and lifetimes of these titania hybrids are recorded, revealing that these hybrid materials with organic polymers exhibit longer luminescence lifetimes and higher quantum efficiencies.     

Effect of hydrolysis catalyst and thermal treatment on titania synthesis via sol-gel

The effect of acidic and basic catalysts and of thermal treatment on the preparation of TiO₂ by the sol-gel method has been studied. The resultant solids were characterized by UV-Vis spectroscopy. A displacement of the band due to a fundamental transition to lower energies was observed when acid catalysts were used.

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Photocatalytic mechanisms of modified titania under visible light

Heterogeneous photocatalysis with titania under visible light has increasingly been a focus for research. Metal or non-metal doping, surface sensitization, semiconductor coupling, precious metal deposition and increasing crystal defects have been used to enhance the photocatalytic activity of titania under visible light. Based on the research results of different modification methods in recent years, some mechanisms from the excitation, bulk diffusion and surface transfer of photoinduced charge carriers, such as band gap modification, changing the excitation path, promoting the separation of photogenerated charge carrier, improving the surface adsorption and reaction, and synergistic effects, for photocatalysis under visible light are discussed and the development trend in this field is predicted.     

Synthesis of willemite by modified sol-gel technique

Silicate luminophor Zn₂SiO₄ : Mn was synthesized using silica gel as an active form of silicon dioxide. Factors affecting the degree of crystallinity of the silicate obtained were studied. Willemite was doped with manganese(II) in the course of synthesis. The luminescence parameters of the resulting samples were estimated.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1605–1609.Original Russian Text Copyright © 2004 by Golovkin, Grekov, Chernovets.     

Low-temperature sol-gel synthesis of modified nickel ferrite

A low-temperature method has been developed for preparing nickel ferrite doped with cobalt and copper (Ni_0.9Co_0.1Cu_0.1Fe_1.9O_{4 − δ}). This method provides the target product at 170–200°C with nanosized particles. The role of ammonium nitrate in the considerable reduction of ferrite synthesis temperature was studied.     

Amperometric biosensor for hydrogen peroxide based on hemoglobin entrapped in titania sol-gel film

Hemoglobin (Hb) was entrapped in a titania sol-gel matrix and used as a mimetic peroxidase to construct a novel amperometric biosensor for hydrogen peroxide. The Hb entrapped titania sol-gel film was obtained with a vapor deposition method, which simplified the traditional sol-gel process for protein immobilization. The morphologies of both titania sol-gel and the Hb films were characterized using scanning electron microscopy (SEM) and proved to be chemically clean, porous, homogeneous. This matrix provided a biocompatible microenvironment for retaining the native structure and activity of the entrapped Hb and a very low mass transport barrier to the substrates. H₂O₂ could be reduced by the catalysis of the entrapped hemoglobin at −300 mV without any mediator. The reagentless H₂O₂ sensor exhibited a fast response (less than 5 s) and sensitivity as high as 1.29 mA mM⁻¹ cm⁻². The linear range for H₂O₂ determination was from 5.0×10⁻⁷ to 5.4×10⁻⁵ M with a detection limit of 1.2×10⁻⁷ M. The apparent Michaelis-Menten constant of the encapsulated hemoglobin was calculated to be 0.18±0.02 mM. The stability of the biosensor was also evaluated.     

Bicontinuous nanodisc and nanospherical titania materials prepared by sol-gel process in reverse microemulsion

TiO₂ nanoparticles with different shapes and sizes were synthesised by the sol-gel route in Water/Brij78/Hexane reverse microemulsions. The aqueous cores of these microemulsions were used as nanoreactors to control sol-gel reactions. We studied the effect of water/surfactant mole ratio (W ₀) on the morphology, and textural properties of the final products. The materials thus obtained were characterised by different techniques. Thermogravimetric and differential thermal analysis (TG-DTA) was used to study the thermal behaviour of the products and X-ray diffraction (XRD) to identify the crystalline phases. The morphological and textural properties of the products were determined by scattering electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) method, respectively. We also studied the influence of thermal treatment on the structure and size of the TiO₂ particles. The effect of W ₀ on the anatase-rutile phase transition temperature was investigated.     

A sensitive mediator-free tyrosinase biosensor based on an inorganic-organic hybrid titania sol-gel matrix

A novel inorganic-organic hybrid titania sol-gel nanocomposite film was prepared to fabricate a sensitive tyrosinase biosensor for the amperometric detection of trace phenolic compounds without additional electron mediators. Acetylacetone worked as a complexing ligand to chelate with Ti atom in the synthesis process, and the pH of the titania solution could be adjusted to the value which was optimum for retaining tyrosinase activity and such a membrane was stably attached on to the surface of a glassy carbon electrode (GCE). This titania matrix could supply a good environment for enzyme loading, which resulted in a high sensitivity of 15.78 μA μM⁻¹ cm⁻² for monitoring phenols with a detection limit of 1×10⁻⁸ M at a signal-to-noise ratio of 3. The TiO₂ sol-gel derived biosensor exhibited a fast response less than 10 s and a good stability for more than 2 months.     

Formation of titania nanofibers: a direct sol-gel route in supercritical CO2

In this letter, we present a new method to synthesize titania nanofibers with nanocrystallites via a sol-gel route in supercritical CO2. The nanofibers were formed by the esterification and condensation of titanium alkoxides using acetic acid as the polymerization agent in supercritical CO2 from 40 to 70 degrees C and 2500 to 8000 psia. The TiO2 nanofiber morphology was characterized by means of SEM and HRTEM, which indicated that the diameters ranged from 9 to 100 nm. N2 physisorption, and powder XRD showed that the nanofibers exhibited relatively high surface areas up to 400 m2/g and anatase and/or rutile nanocrystallites were formed after calcination.     

Removal of plutonium from carbonate medium using titania microspheres prepared by sol-gel route

Spherical beads of titania were prepared by a sol-gel route. During the preparation a cationic surfactant was added in the feed broth to modify the surface characteristics of the microspheres. The absorption behavior of Pu(IV) from carbonate medium on these microspheres was studied by batch experiments. Loading and elution behavior of Pu(IV) on a bed of titania microspheres was studied and the practical capacity was determined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of submicrometer-sized titania spherical particles with a sol-gel method and their application to colloidal photonic crystals

A synthetic method for preparing submicrometer-sized titania particles is proposed, which is based on hydrolysis of titanium alkoxide with the use of a cosolvent and an amine catalyst for alkoxide hydrolysis. The preparation was performed with different amines of ammonia, methylamine (MA), and dimethylamine (DMA) in different solvents of ethanol/acetonitrile, ethanol/methanol, ethanol/acetone, ethanol/acetonitrile, and ethanol/formamide for 0.1-0.3 M water and 0.03 M titanium tetraisopropoxide (TTIP) at temperatures of 10-50 degrees C. The use of the ethanol/acetonitrile solvent with MA was required for preparing monodispersed, spherical particles. The number average of the titania particle sizes and their coefficient of variation were varied from 143 to 551 nm and from 5.7 to 20.6%, respectively, with reaction temperature and concentrations of water and MA. Colloidal crystals of titania particles fabricated with a sedimentation method revealed reflection peaks attributed to Bragg's diffraction. Annealing at 100-1000 degrees C led to shrinkage and crystallization of titania particles followed by an increase in the refractive index of titania particles.