TG-DTA study on the lanthanoid trifluoromethanesulfonate complexes

The thermal decomposition of the lanthanoid trifluoromethanesulfonate (triflate) complexes {Ln(CF₃SO₃)₃·9H₂O; Ln=La-Lu{ was studied by TG and DTA methods. From the endothermic and exothermic data of Ln(CF₃ SO₃)3·9H₂O complexes, pyrolysis behavior of the complexes is classified into three groups: 1) La-Nd salts, 2) Sm-Ho salts, 3) Er-Lu salts. It has also shown that all the final decomposition products were found to result in the formation of LnF₃. This revised version was published online in July 2006 with corrections to the Cover Date.     

Highly permeable mesoporous silica membranes synthesized by vapor infiltration of tetraethoxysilane into non-ionic alkyl poly(oxyethylene) surfactant films

Mesoporous silica membranes were prepared on porous alumina substrates by a vapor infiltration of tetraethoxysilane (TEOS) into a non-ionic poly(oxyethylene) (Brij56) surfactant film. Periodic mesostructured silica membranes were formed on both α- and γ-alumina substrates pre-treated with polystyrene. The polystyrene polymer plugged the pores of the alumina substrates and inhibited the deposition of silica in the alumina pores, resulting in the formation of a very thin silica membrane without a silica/alumina composite layer at the interface between mesoporous silica and the alumina substrates. The calcined mesoporous silica membrane showed very high nitrogen permeance (>10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹). The single gas permeation was governed by the Knudsen diffusion mechanism. The durability of the mesoporous silica membrane against moisture in air was improved by a silylation with trimethylethoxysiliane.     

Meso- to Macro-Porous Oxides as Semiconductor Gas Sensors

The present article reviews our latest studies directed to improving gas sensing properties of semiconductor metal oxides, SnO₂ and TiO₂, by controlling their porous structure in the range of nano- to micro-meter size. Thermally stable mesoporous oxide powders and submicron-size porous thick films were fabricated by a templating method employing supramolecular surfactants or polymethylmethacrylate microspheres and also by a sol–gel process in a polyethylene glycol matrix. Advantages of these methods in improving the sensing properties are overviewed and then remaining problems are discussed.     

Nano-architectural silica thin films with two-dimensionally connected cagelike pores synthesized from vapor phase

Novel mesostructured silica thin films were prepared on a Si substrate by a vapor-phase synthesis. Vapor of tetraethoxysilane (TEOS) was infiltrated into a surfactant film consisting of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer. Nanophase transition from a lamellar structure to a two-dimensional cage structure of a silica-surfactant nanocomposite was found under vapor infiltration. The rearrangement into the cage structure implies high mobility of the silica-surfactant composites in solid phase. The silica thin films have two-dimensionally connected cagelike mesopores and are isotropic parallel to the film surface. The structure of pores of the films is advantageous for next-generation low-k films. The mesoporous structure has a large lattice parameter d of approximately 102 A, silica layer thickness of approximately 58 A, pillar diameter in the middle of approximately 60 A, pore size of approximately 72 A, BET surface area of approximately 729 m(2)/g, and pore volume of approximately 1.19 cm(3)/g. The films synthesized by the vapor infiltration show a lower concentration of residual Si-OH groups compared to the films prepared by a conventional sol-gel method. The films show high thermal stability up to 900 degrees C and high hydrothermal stability. This method is a simpler process than conventional sol-gel techniques and attractive for mass production of a variety of organic-inorganic composite materials and inorganic porous films.     

Electrochemiluminescence Sensor Having a Pt Electrode Coated Doubly with Ru(bpy)32+-Modified Chitosan and Silica Gel Membranes. Influence of the Introduction of Functional Groups into the Silica Gel on the Substrate Selectivity

Considerable research efforts are being devoted toward the development of chemical sensors and biosensors based on the so卜gel technology. We have prepared an ECL-optic sensor having a Pt electrode coated doubly with a Ru(bpy)₃²⁺-modified chitosan and silica gel membrane. In the present paper we would like to report on the substrate selectivities of ECL electrode having a silica gel layers modified with amino or alkyl groups. The new ECL electrode were prepared by the same method as reported previously, except that organotrialkoxysilanes were added to the silica-sol precursor solution. Experimental results at an applied potential of 1.10 V vs. Ag/AgCI in 0.05 M phosphate buffer (pH 6.8) for a several substrates are summarized as follows.     

Laser induced fluorescence of HNO and DNO ã1A″ — -X1A′ in a supersonic free jet

The SRVL fluorescenee lifetimes and fluorescence excitation spectra of the HNO ã¹A″ -X¹AA′ transition were measured in a supersonic free jet. The cooling of a rotational temperature in the jet made it possible to clear up the parity-selected perturbations in the asymmetric rotor under higher resolution condition. The fluorescence lifetimes of strongly perturbed levels, i.e. HNO ã¹A″ 011 rovibronic levels were observed with dual exponential decay profiles, while non-perturbed levels exhibited single ones. The SRVL fluorescence lifetimes and fluorescence excitation spectra of DNO ã¹″ -X¹A′ were measured under the same condition as HNO. The rotationll analysis of the DNO ã¹A″ 011 rovibronic levels was first carried out in the jet.     

Elimination of ingredients effect to improve the detection of anti HIV-1 p24 antibody in human serum using SPR apparatus.

Highly sensitive detection of proteins in serum becomes difficult in some cases during surface plasmon resonance (SPR) measurements, because some ingredients in the serum hugely enhance non-specific reactions on the sensing chip of SPR. It is well recognized that the antibody against core protein p24 of HIV in serum is one of the most important proteins in the accurate diagnosis of infection with HIV. In this study, we could attain the accurate detection of anti p24 antibody in human serum by eliminating the serious effects of the ingredients in serum on the measurement of SPR by employing these procedures: 1) blocking the gold surface of the sensing chip with human serum and 2) heating the serum sample at 56 degrees C for 30 min. Without these treatments, the signal of SPR was considerably suppressed on the measurements of the anti p24 antibody which contained human serum, making the accurate detection difficult. However, with introducing the above two treatments, the sensing of anti p24 antibody in human serum was improved, while a small non-specific reaction was still observed. By removing the non-specific reaction caused by the ingredients in the serum, we could accurately measure the antibody for p24 in human serum sample over the range from 1 to 20 micrograms/ml.     

Synthesis of 3D pore mesostructured silica films by vapor infiltration of tetraethoxysilane

Nonionic alkyl poly(oxyethylene) surfactants (Brij 56) films on a silicon substrate were treated with a tetraethoxysilane (TEOS) vapor. Mesostructured silica films were formed through a nano-phase transition under the infiltration of TEOS into the surfactant films. It was found that the calcined film had a 3D pore structure from the field emission scanning electron microscope (FE-SEM) observations in a different orientation. Grazing angle of incidence small angle X-ray scattering (GISAXS) measurement results showed that the symmetry of the film was an Fmmm space group oriented with the (010) plane parallel to the surface. The ordered structure of the films showed higher thermal stability than the films prepared by a conventional solvent-evaporation method.     

Synthesis of ordered mesoporous zirconium phosphate films by spin coating and vapor treatments

Ordered mesoporous zirconium phosphate films were prepared on a silicon substrate by spin coating using a mixture of zirconium isopropoxide, triethyl phosphate, Pluronic P123 triblock copolymer, nitric acid, ethanol, and water. The spin-on film was consecutively treated with vapors of phosphoric acid and ammonia. The post-vapor treatments effectively enhanced the thermal stability of an ordered mesostructure when heated to 500 degrees C. XRD and TEM analyses show that the calcined zirconium phosphate film has a hexagonal structure with straight channels parallel to the film surface. The zirconium phosphate film exhibited high proton conductivity of 0.02 S/cm parallel to the film surface at 80% RH and 25 degrees C.