Organic surface modification and analysis of titania nanoparticles for self-assembly in multiple layers

The characteristics of TiO₂ coatings can greatly influence their final performance in large-scale applications. In the present study, self-assembly of TiO₂ nanoparticles (NPs) in multiple layers was selected as a deposition procedure on various substrates. For this, the main prerequisite constitutes the surface modification of both NPs and substrate with, for example, silane coupling agents. A set of functionalized TiO₂ NPs has been produced by reaction with either (3-aminopropyl)triethoxysilane (APTES) or (3-aminopropyl)phosphonic acid (APPA) to functionalize the NP surface with free amino-groups. Then, the complementary functionalized NP set can be obtained from an aliquot of the first one, through the conversion of free surface amino groups to aldehydes by reaction with glutaraldehyde (GA). Several types of TiO₂ NPs differing in size, shape, and specific surface area have been functionalized. Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), SEM/ energy-dispersive X-ray spectroscopy (EDS), XPS, Auger electron spectroscopy (AES), and Time-of-Flight (ToF)-SIMS analyses have been carried out to evaluate the degree of functionalization, all the analytical methods employed demonstrating successful functionalization of TiO₂ NP surface with APTES or APPA and GA.     

Crosslinking of hyaluronic acid with glutaraldehyde

Hyaluronic acid (HA) was chemically crosslinked with glutaraldehyde (GA) to produce water-insoluble films having low water contents when brought into contact with water. The crosslinking reaction was performed using uncrosslinked HA films in acetone–water mixtures. This method could produce water-insoluble HA films with water contents as low as 60 wt % when subjected to swelling with phosphate-buffered saline of pH 7.4 at 37°C. This 60 wt % water content was lower than any values for HA ever reported. There was an optimal HCl concentration around 0.01N for the HA crosslinking with GA in acetone—water mixtures. To get information on the crosslinking mechanism, alginic acid, which possesses hydroxyl and carboxyl groups in one molecule, similar to HA, and poly(vinyl alcohol) (PVA) and amylopectin, which possess only hydroxyl groups, were subjected to crosslinking with GA. PVA and amylopectin were also found to become water-insoluble after reaction with GA. On the basis of the infrared spectra of these crosslinked films, it was concluded that intermolecular formation of hemiacetal bonds with GA between the hydroxyl groups belonging to different HA molecules led to crosslinking. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3553–3559, 1997     

CS-CMC聚合物电解质膜的制备及在电生成FeO42-中的应用

以戊二醛为交联剂, 制备了壳聚糖(CS)-羧甲基纤维素(CMC)聚合物电解质膜. 用电子显微镜观察其表面形貌. IR分析表明该聚合物薄膜含有COOH, NH₃⁺官能团, 具有两性离子的特征. 与CS膜或CMC膜相比, 该膜能稳定存在于酸碱溶液中. 膜特性研究表明CS-CMC聚合物电解质膜具有离子交换和选择性渗透能力, 可作为隔膜电解制备高铁酸盐.     

Optimization of protease immobilization by covalent binding using glutaraldehyde

Immobilization of a protease, Flavourzyme, by covalent binding on various carriers was investigated. Lewatit R258-K, activated with glutaraldehyde, was selected among the tested carriers, because of the highest immobilized enzyme activity. The optimization of activation and immobilization conditions was performed to obtain high recovery yield. The activity recovery decreased with increasing carrier loading over an optimal value, indicating the inactivation of enzymes by their reaction with uncoupled aldehyde groups of carriers. The buffer concentrations for carrier activation and enzyme immobilization were optimally selected as 500 and 50 mM, respectively. With increasing enzyme loading, the immobilized enzyme activity increased, but activity recovery decreased. Immobilization with a highly concentrated enzyme solution was advantageous for both the immobilized enzyme activity and activity recovery. Consequently, the optimum enzyme and carrier loadings for the immobilization of Flavourzyme were determined as 1.8 mg enzyme/mL and 0.6 g resin/mL, respectively.     

An Ion-Selective Electrode for Dibasic Phosphate Ion

Abstract

A phosphate-selective electrode is developed based on a silver coordination reaction. The electrode responds linearly toward HPO₄ ⁼ in the concentration range of 10^?4 to 10^?1 M (slope = 27 mV/dec.). The electrode also shows good selectivity over sulfate, nitrate, perchlorate and acetate.