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71.
利用压电频移法测定水中的痕量亚硝酸盐 总被引:8,自引:0,他引:8
提出了利用压电频移法测定亚硝酸盐的方法。方法以碘离子与亚硝酸根之间的氧化还原反应为依据,通过测定由反应生成的碘所引起的压电晶体频率的变化,在被萃取水相中亚硝酸盐浓度为0.009 ̄2.3mg/L范围内,频移值与浓度成正比:ΔF=5.8+2.5×10^3C(mg/L),r=0.9901。方法简便,用于天然水中亚硝酸盐的测定,结果令人满意。 相似文献
72.
B. F. Myasoedov 《Russian Chemical Bulletin》1992,41(3):383-387
The capabilities and development prospects of chemical sensors as a new area in analytical chemistry and instrument engineering are discussed. Problems of terminology, principles of operation, basic characteristics, and also applications of chemical sensors and sensor analyzers made from them are discussed.From the materials of a report given at a joint scientific session of the departments of the physicochemistry and technology of inorganic materials and of general and technical chemistry.V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow 117975. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 487–493, March, 1992. 相似文献
73.
Niu CG Gui XQ Zeng GM Guan AL Gao PF Qin PZ 《Analytical and bioanalytical chemistry》2005,383(2):349-357
A fluorescence ratiometric sensor for pH determination is described in this paper. The sensor incorporated the pH-sensitive
dye meso-5,10,15,20-tetra-(4-allyloxyphenyl)porphyrin (TAPP) as an indicator and a pH-insensitive dye N-(2-methacryloxyethyl)benzo[k,l]thioxanthene-3,4-dicarboximide (MBTD), a benzothioxanthene derivative, as a reference for fluorescence ratiometric measurement.
To prevent leakage of the dyes, both were photocopolymerized with acrylamide, hydroxyethyl methacrylate, and triethylene glycol
dimethacrylate on the silanized glass surface. The reproducibility and response time of the prepared sensor were sufficient.
Most common coexisting inorganic ions and organic compounds did not interfere with pH sensing. In the acidic pH range from
1.5 to 5.0 the fluorescence intensity ratio of the two dyes varied linearly as a function of pH. The sensing membrane was
found to have a lifetime of at least one month. The sensor was applied to the analysis of waste water and artificial samples. 相似文献
74.
Yongcheng Liu Xin Chen Jianghong Qian Haiying Liu Zhengzhong Shao Jiaqi Deng Tongyin Yu 《Applied biochemistry and biotechnology》1997,62(2-3):105-117
The structure and properties of the blend of regenerated silk fibroin (RSF) and poly(vinyl alcohol) (PVA) were investigated.
The two polymers in the blend are in the state of phase segregation. Infrared (IR) spectra indicate that the RSF in the blend
maintains its intrinsic properties, thus, ethanol treatment can transfer silk I structure of RSF to silk II structure. The
water absorption property and mechanical property of the blend are improved in comparison with those of RSF. The blend maintains
the major merit of RSF, that is, it can immobilize glucose oxidase on the basis of the conformational transition from silk
I structure to silk II structure. The properties of the immobilized enzyme are examined. Moreover, the second generation of
glucose sensor based on the immobilized enzyme is fabricated and it has a variety of advantages including easy maintenance
of enzyme, simplicity of construction, fast response time and high stability. 相似文献
75.
The surface and materials science of tin oxide 总被引:3,自引:0,他引:3
The study of tin oxide is motivated by its applications as a solid state gas sensor material, oxidation catalyst, and transparent conductor. This review describes the physical and chemical properties that make tin oxide a suitable material for these purposes. The emphasis is on surface science studies of single crystal surfaces, but selected studies on powder and polycrystalline films are also incorporated in order to provide connecting points between surface science studies with the broader field of materials science of tin oxide. The key for understanding many aspects of SnO2 surface properties is the dual valency of Sn. The dual valency facilitates a reversible transformation of the surface composition from stoichiometric surfaces with Sn4+ surface cations into a reduced surface with Sn2+ surface cations depending on the oxygen chemical potential of the system. Reduction of the surface modifies the surface electronic structure by formation of Sn 5s derived surface states that lie deep within the band gap and also cause a lowering of the work function. The gas sensing mechanism appears, however, only to be indirectly influenced by the surface composition of SnO2. Critical for triggering a gas response are not the lattice oxygen concentration but chemisorbed (or ionosorbed) oxygen and other molecules with a net electric charge. Band bending induced by charged molecules cause the increase or decrease in surface conductivity responsible for the gas response signal. In most applications tin oxide is modified by additives to either increase the charge carrier concentration by donor atoms, or to increase the gas sensitivity or the catalytic activity by metal additives. Some of the basic concepts by which additives modify the gas sensing and catalytic properties of SnO2 are discussed and the few surface science studies of doped SnO2 are reviewed. Epitaxial SnO2 films may facilitate the surface science studies of doped films in the future. To this end film growth on titania, alumina, and Pt(1 1 1) is reviewed. Thin films on alumina also make promising test systems for probing gas sensing behavior. Molecular adsorption and reaction studies on SnO2 surfaces have been hampered by the challenges of preparing well-characterized surfaces. Nevertheless some experimental and theoretical studies have been performed and are reviewed. Of particular interest in these studies was the influence of the surface composition on its chemical properties. Finally, the variety of recently synthesized tin oxide nanoscopic materials is summarized. 相似文献
76.
77.
Thanner H. Krempl P. W. Selic R. Wallnöfer W. Worsch P. M. 《Journal of Thermal Analysis and Calorimetry》2003,71(1):53-59
Quartz-homeotypic gallium (ortho-) phosphate, GaPO4, is of special interest for resonator applications asking for temperature compensated cuts with higher electro-mechanical coupling than quartz and operational temperatures up to 970°C. The crystal microbalance technique, well known for quartz (QCM) which can be used only at moderate temperatures, can now be extended to much higher temperatures using GaPO4 crystals, benefiting from all three advantages mentioned above. Two different experiments were done to demonstrate the advantages of a crystal microbalance based on GaPO4. First, the GaPO4 resonator was used for film thickness determination and compared with a commercial QCM. This experiment demonstrated that the measuring range can be extended by using GaPO4 resonators instead of quartz. The second experiment demonstrates the possibility for thermogravimetric analysis up to 720°C by using a new concept for resonator mounting.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
78.
水热法合成K0.5Bi0.5TiO3纳米陶瓷粉体 总被引:3,自引:0,他引:3
K0.5Bi0.5TiO3(KBT)nanocrystalline particles were hydrothermally synthesized from Bi(NO3)3·5H2O, TiO2 and KOH. The crystal phase, chemical composition and microstructure were characterized by XRD, XRF, Raman scattering spectroscopy and TEM. The results indicated that the products were pure perovskite structured K0.5Bi0.5TiO3 with chemical stoichiometry and perovskite structure. The TEM observation revealed that the particles possessed a feature of cubic shape and a nano-scale of about 40 nm. The KBT ceramics sintered at 1 040 ℃ from hydrothermal powders show higher density and better electric properties than that prepared by a solid-state reaction method. 相似文献
79.
A new optical CO2 sensor based on the luminescence intensity change of the europium(III) complex tris(thenoyltrifluoroacetonato) europium(III) dihydrate ([Eu(tta)3]) caused by the absorption change of various pH indicators—thymol blue, phenol red, or cresol red—with CO2 was developed and its CO2 sensing properties were investigated. For all the CO2 sensors using pH indicators the observed luminescence intensity from [Eu(tta)3] at 613 nm increased with increasing CO2 concentration. The linear calibration method based on the plot of (I100–I0)/(I–I0) versus the inverse of CO2 concentration was suggested, where I0 and I100 were luminescence intensities at 613 nm of the CO2 sensor film in 100% nitrogen and 100% gaseous CO2. In all cases the plots showed good linearity and the correlation factors of the plots, r2, were 0.991 for thymol blue, 0.990 for phenol red, and 0.998 for cresol red. The slopes of the plots (A/B) for thymol blue, phenol red, and cresol red were 2.2, 5.2, and 9.0%, respectively. The response times of the CO2 sensor film were 4.0 s for thymol blue, 4.4 s for phenol red, and 8.8 s for cresol red for switching from nitrogen to CO2, and the recovery times of films were 36 s for thymol blue, 39.2 s for phenol red, and 56.6 s for cresol red for switching from CO2 to nitrogen. The signal changes were fully reversible and hysteresis was not observed during the measurements. The highly sensitive CO2 sensor was developed using thymol blue as an indicator for the CO2-sensing probe. 相似文献
80.