Continuous‐Bed Columns Containing Sol‐Gel Bonded Packing Materials for Capillary Electrochromatography

Sol‐gel bonded packing materials in continuous‐bed columns have been prepared for capillary electrochromatography (CEC). Three packing materials were investigated: small‐pore Spherisorb ODS1 (3 μm, 80 Å) with octadecyl as stationary phase, small‐pore mixed‐mode Spherisorb ODS/SCX (3 μm, 80 Å) with octadecyl and propyl sulfonic acid as stationary phases, and large‐pore Nucleosil ODS (7 μm, 1 400 Å) with octadecyl as stationary phase. The characteristics of these columns were compared in terms of electroosmotic flow, efficiency, inertness, and retention factors. In contrast to columns containing sol‐gel bonded ODS, columns containing sol‐gel bonded mixed‐mode ODS/SCX generated nearly pH independent electroosmotic flow (EOF) over pH 2–9. Columns containing sol‐gel bonded large‐pore ODS produced nearly three times lower reduced plate height than those containing small‐pore ODS. Efficiencies of 220,000 plates per meter and 175,000 plates per meter were obtained from columns containing sol‐gel bonded 7 μm, 1 400 Å ODS and columns containing sol‐gel bonded 3 μm, 80 Å ODS, respectively, which are among the highest reported efficiencies for continuous‐bed columns. In CEC, over one million plates per meter and pH independent EOF are expected from continuous‐bed columns containing sol‐gel bonded 1.5 μm particles with large pores and mixed‐mode stationary phases.     

Low‐Temperature Sol‐Gel Synthesis of Nanostructured Polymer/Titania Hybrid Films based on Custom‐Made Poly(3‐Alkoxy Thiophene)

A low‐temperature route to directly obtain polymer/titania hybrid films is presented. For this, a custom‐made poly(3‐alkoxy thiophene) was synthesized and used in a sol‐gel process together with an ethylene‐glycol‐modified titanate (EGMT) as a suitable titania precursor. The poly(3‐alkoxy thiophene) was designed to act as the structure‐directing agent for titanium dioxide through selective incorporation of the titania precursor. The nanostructured titania network, embedded in the polymer matrix, is examined with atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements. By means of the scattering technique grazing incidence wide‐angle X‐ray scattering (GIWAXS), a high degree of crystallinity of the polymer as well as successful transformation of the precursor into the rutile phase of titania is verified. UV/Vis measurements reveal an absorption behavior around 500 nm which is similar to poly(3‐hexyl thiophene), a commonly used polymer for photoelectronic applications, and in addition, the typical UV absorption behavior of rutile titania is observed.     

UV‐Irradiation Cured Organic‐inorganic Hybrid Nanocomposite Initiated by Ethoxysilane‐modified Multifunctional Polymeric Photoinitiator through Sol‐gel Process

The UV‐cured organic‐inorganic hybrid nanocomposite (nano‐Si‐m‐PI) was prepared through the photopolymerization of acrylic resin initiated by ethoxysilane‐modified multifunctional oligomeric photoinitiator (Si‐m‐PI). The esterification reaction of 2‐hydroxy‐4′‐(2‐hydroxyethoxy)‐2‐methylpropiophenone (Irgacure 2959) with thioglycolic acid, and the following addition reactions with dipentaerythritol hexaacrylate and then 3‐aminopropyltriethoxysilane were carried out for preparing the Si‐m‐PI. The Si‐m‐PI exhibits the similar UV absorption and molar extinction coefficient with Irgacure 2959. The photoinitiating activity study by photo‐DSC analysis showed that the Si‐m‐PI possesses high photopolymerization rate at the peak maximum (R_p^max) and final unsaturation conversion (P^f) in the cured hybrid films. From the scanning electron microscope (SEM) observation, the SiO₂ nanoparticles dispersed uniformly in the formed nano‐Si‐m‐PI, whereas the aggregation of nanoparticals occurred in nano‐Irg, which was prepared through the photopolymerization of acrylic resin initiated by Irgacure 2959. Moreover, compared with the UV‐cured pure polymer and nano‐Irg, the nano‐Si‐m‐PI showed remarkably enhanced thermal stability and mechanical properties.     

基于sol-gel过程的二阶NLO极化聚合物进展

介绍了用sol－gel制备二阶NLO极化聚合物材料的方法，综述了其进展。     

An Organic Sol‐Gel Film as Modifier to Construct Biosensor

A new amperometric biosensor for hydrogen peroxide (H₂O₂) was developed by adsorbing hemoglobin (Hb) on an organic sol‐gel film. The organic sol‐gel was prepared using resorcinol and formaldehyde as monomers. This sol‐gel film shows a biocompatible microenvironment for retaining the native activity of the adsorbed Hb. The direct electron transfer between Hb and electrode is achieved. Hb adsorbed on the film shows an enzyme‐like catalytic activity for the reduction of H₂O₂. The reduction peak currents are proportional linearly to the concentration of hydrogen peroxide in the range of 6×10^?8 to 3.6×10^?6 M, with a detection limit of 2.4×10^?8 M (S/N=3). This research enlarges the applications of organic sol‐gel materials in biosensor field.     

Suppression of Thermochromism in a Poly(di‐n‐hexylsilane)‐Zirconia Hybrid

Summary: Poly(di‐n‐hexylsilane) (PDHS)‐containing zirconia hybrid thin films were prepared by a sol‐gel reaction of PDHS copolymers and zirconium alkoxide, and it was found that the thermochromic properties of PDHS due to the transformation of the Si Si main chain were suppressed in the PDHS‐zirconia hybrid thin film.

Structure of poly(di‐n‐hexylsilane)‐zirconia hybrid.     

Amperometric Nitrite Sensor Based on PVP‐Os Entrapped in Titania Sol‐Gel Matrix

A novel nitrite sensor was developed based on the immobilization of a partially quaternized poly(4‐vinylpyridine) complexed with [Os(bpy)₂Cl]^+/2+ (PVP‐Os) in a porous TiO₂ sol‐gel matrix by a vapor deposition method. The preparation process simplified the traditional sol‐gel process and prevented the cracking of conventional sol‐gel derived glasses. Electrochemical behavior of the sensor was characterized by cyclic voltammetry and shows excellent electrocatalytic response for the reduction of nitrite. Effect of operating potential on electrochemical responses of the sensor was explored for optimum analytical performance by using the amperometric method. The stability of the sensor was also evaluated.     

Preparation of Monolithic Ti‐incorporated Mesoporous Silica Materials via Tartaric Acid Templated Sol‐gel Process

Monolithic and transparent Ti‐incorporated mesoporous silica materials of large size (e.g. 2 mm) in dimension have been prepared with tartaric add (TA) as template via sol‐gel reactions of tetraethyl orthosilicate (TEOS) and tetrabutyl titanate (TBT). The materials are characterized by infrared (IR), nitrogen adsorption‐desorption isotherms, powder X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicate that the monolithic materials exhibit large specific surface areas (ca. 1200 mVg) and pore volumes (ca. 0.900 cm³/g).     

Direct Electrochemistry of Cytochrome c on a Silica Sol‐Gel Film Modified Electrode

Dilute silica sol‐gel was simply dropped on the surface of a basal plane graphite electrode (BPGE) to form a silica sol‐gel film modified electrode. Direct electrochemical response of cytochrome c (Cyt c) on the modified electrode was observed by cyclic voltammetry (CV). The results suggested that Cyt c could be tightly adsorbed on the surface of the silica sol‐gel film modified electrode. A couple of well‐defined and nearly reversible redox peaks can be observed in a phosphate buffer solution (pH 7.0), which anodic and cathodic peak potentials were at ?0.243 and ?0.306 V (vs. Ag/AgCl), respectively. Cyt c adsorbed on the surface of silica sol‐gel film shows a remarkable electrocatalytic activity for the reduction of oxygen. Based on these, a third‐generation biosensor could be constructed to detect the concentration of oxygen in aqueous solution.     

Microstructure analysis of sol‐gel‐derived nanocrystalline ITO thin films

The technique for ITO (Tin‐doped indium oxide) thin films by sol‐gel process is presented in this paper. After annealing at 500° for 15 min, ITO gel films get transformed into nanocrystallined indium tin oxide films. We studied the microstructure of ITO thin film which is closely related to optical and electrical properties. The microstructure of ITO thin film can be observed through high‐resolution transmission electronic spectroscopy (HRTEM) and the Fast Fourier Transform (FFT) technique. The film is nanocrystallite with grain sizes about 20 nm. Also, the surface chemical components were studied by XPS spectra. The transmission and the resistivity of ITO films is 97.0% and 3.5 × 10^?3 Ω?cm, respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

Organically Modified Sol‐Gel/Chitosan Composite Based Glucose Biosensor

A new type of organically modified sol‐gel/chitosan composite material was developed and used for the construction of glucose biosensor. This material provided good biocompatibility and the stabilizing microenvironment around the enzyme. Ferrocene was immobilized on the surface of glassy carbon electrode as a mediator. The characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The effects of enzyme‐loading, buffer pH, applied potential and several interferences on the response of the enzyme electrode were investigated. The simple and low‐cost glucose biosensor exhibited high sensitivity and good stability.     

Gel‐to‐Sol and Sol‐to‐Gel Transitions Utilizing the Interaction of α‐Cyclodextrin with Dodecyl Side Chains Attached to a Poly(acrylic acid) Backbone

Summary: By utilizing the interaction of α‐cyclodextrin (α‐CD) with dodecyl side chains in polymers of x mol‐% dodecyl‐modified poly(acrylic acid) (p(AA/C₁₂(x))), systems that undergo gel‐to‐sol and sol‐to‐gel transitions were successfully constructed. Rheological experiments indicated that addition of α‐CD to the hydrogel of p(AA/C₁₂(5)) caused a drastic decrease in the viscosity, while addition of oligo(α‐CD) to the solution of p(AA/C₁₂(2)) led to a remarkable increase in the viscosity.

Photographs for a gel‐to‐sol transition upon addition of α‐CD to 5.0 g · L⁻¹ p(AA/C₁₂(5)).     

Preparation of Durable Emitter of Electrospray Mass Spectrometry by Covalently Coating the Fused‐Silica Capillary Tip with Carbon‐Nanotube Sol‐Gel Composite Material

A simple approach for the preparation of emitter of electrospray ionization mass spectrometry by covalently coating the fused‐silica capillary tip with the conductive carbon‐nanotube sol‐gel composite material (CNTSCM) is described. The CNTSCM was prepared by dispersing single‐walled carbon nanotubes in the sol composed of a mixture of 3‐glycidoxypropyltrimethoxysilane and 3‐aminopropyltrimethoxysilane, and ethanol. The long‐term stability of the prepared ESI emitters was demonstrated by at least 180 h of continuous use. Signal intensity obtained by the prepared emitter was mass‐flux sensitive when the flow rate was lower than 500 nL/min, while the signal intensity performed a concentration dependence when the flow rate was in the range of 500–800 nL/min. The usefulness of such a prepared emitter was demonstrated by the analysis of various types of samples such as organic small molecular drugs, oligosaccharide, peptide, and protein.     

Synthesis and Optical Properties of Sol‐Gel Hybrid Materials that Contain Perfluorocyclobutyl Groups

Summary: A strategy for the synthesis of sol‐gel hybrid materials that contain perfluorocyclobutyl groups is reported. Sol‐gel films have been prepared from three types of siloxane monomers using a typical sol‐gel method in an acidic atmosphere, followed by UV irradiation and dimerization. The materials show high thermal stability that exceeds 400 °C. At a wavelength of 1 550 nm, the refractive index, the birefringence, and the optical loss of the sol‐gel materials are found to be in the ranges of 1.4568–1.4876, −0.0003–0.0029, and 0.34–0.45 dB · cm⁻¹, respectively.

Zero mode birefringence (TE: solid, TM: dash dot) of sol‐gel materials (PFSI/TFVOSI/MSI = 6:1:3) (TE and TM represent polarization perpendicular and parallel to the plane of incidence, respectively).     

Synthesis of Pure Cementitious Phases by Sol‐Gel Process as Precursor

Calcium silicates and aluminates are the main constituents of ordinary Portland cement (OPC) and calcium aluminate cements (CAC) and therefore the pure phases are of great importance for the investigation of interactions between binder and additives or admixtures. Additionally, investigations on clinker phases doped with foreign ions enable the improvement of the performance of cements. For this purpose great amounts of pure phases are needed. These phases are hard to synthesize via a solid state reaction of solid educts. Thus there is a need for a new, more efficient route to synthesize these phases. The sol‐gel process as precursor provides an alternative to the conventional method. In this paper experimental evidence is presented for an improved synthesis of calcium silicates and aluminates via sol‐gel processes, the characterisation of these clinker phases and their hydration behaviour.     

Polyurethanes Containing Indole‐Based Non‐Linear Optical Chromophores: from Linear Chromophore to H‐Type

Two new “H” type of indole‐based chromophores were designed and successfully introduced to the polymeric system, the resultant polymers demonstrated enhanced NLO effects, good processability, thermal stability and nearly excellent transparency, indicating the advantages of “H” type chromophore moieties. And they could be promising candidates for the practical applications as new photonic materials.

     

微粒溶胶凝胶法合成锂离子电池用正极材料LiNi0.85Co0.15O2及表征

以LiOH·H₂O、Ni(CH₃COO)₂·4H₂O 和 Co(CH₃COO)₂·4H₂O为原料，在水-乙醇体系中，采用微粒溶胶凝胶方法(PSG)成功地制备了锂离子电池用正极材料LiNi_0.85Co_0.15O₂。使用差热-热重(DTA-TG)方法来研究凝胶的热分解过程。粉末X-射线衍射(XRD)测试表明，在700 ℃、氧气氛中，原料混合物能形成具有较好α-NaFeO₂层状结构的晶型化合物。扫描电镜(SEM)显示，与固相合成方法相比，PSG制备的LiNi_0.85Co_0.15O₂颗粒较细、且颗粒大小分布均匀。充放电实验结果表明，PSG合成的LiNi_0.85Co_0.15O₂首次放电容量为196.4 mAh/g, 10次循环之后，容量还有189.1 mAh/g (3.0～4.3V、18 mA/g)，显示其具有良好的循环性能；而同样条件下，固相法合成的样品，首次放电容量为187.3 mAh/g，10次循环之后，容量衰减为167.1 mAh/g。     

A Fast Response Strontium Ion‐Selective Electrode Prepared by Sol‐Gel Membrane Technique

A sol‐gel electrode, based on 6‐(4‐nitrophenyl)‐2‐phenyl‐4,4‐dipropyl‐3,5‐diaza‐bicyclo [3,1,0] hex‐2‐ene (NPDBH) as a neutral ionophore, was successfully developed for the detection of Sr²⁺ in aqueous solutions. Theoretical calculations confirmed NPDBH selectivity toward strontium in comparison with some other metal ions. The electrode responds to Sr²⁺ ion with a sensitivity of 29.1±0.4 mV/decade over the range 8.0×10^?7–1.0×10^?1 M. Selectivity coefficients determined by matched potential method (MPM) indicate high selectivity for strontium ions. The electrode has a fast response time of 11 s and a working pH range of 3.0–10.0. The sol‐gel electrode shows detection limit of 7.5×10^?8 M.