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121.
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
122.
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
123.
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
124.
Mariko Kusabe Hiromitsu Kozuka Satoru Abe Hiroshi Suzuki 《Journal of Sol-Gel Science and Technology》2007,44(2):111-118
Hydroxypropylcellulose (HPC)–titania hybrid thin films were prepared by sol–gel method where titanium tetraisopropoxide Ti(OC3H7
i
)4 was hydrolyzed under acidic conditions in the presence of HPC, followed by dip-coating and drying at 120 °C for 24 h. The
viscosity average molecular weight of HPC was 55,000–70,000 or 110,000–150,000, and the TiO2/(HPC + TiO2) mass ratio ranged from 0 to 1, which was calculated on the assumption that all Ti(OC3H7
i
)4 is converted into TiO2. The films were 0.35–1.0 μm thick, transparent in visible region and opaque in ultraviolet (UV) region, where the optical
absorption coefficient in UV region increased with increasing titania content. The refractive index increased with increasing
titania content, ranging from 1.6 to 1.8 for the hybrid thin films. The pencil hardness increased from 6B to 5H, the durability
in hot water significantly increased and the contact angle of water on films increased from 35° to 89° with increasing titania
content. Crack-free films could be deposited on organic polymer substrates irrespective of titania or HPC contents, where
cracking did not occur at higher HPC contents even when the substrate was bent. 相似文献
125.
《Journal of separation science》2003,26(14):1259-1262
Microemulsion electrokinetic chromatography (MEEKC) has been applied to the separation of some UV filters (Eusolex 4360, Eusolex 6300, Eusolex OCR, Eusolex 2292, Eusolex 6007, Eusolex 9020, Eusolex HMS, Eusolex OS, and Eusolex 232) commonly used in sunscreen lotions. Use of a MEEKC buffer with a mixed surfactant system to stabilize the oil droplets and an organic modifier in the aqueous phase allowed separation of most of the selected analytes in a single run in a system fitted with a diode array detector recording three wavelengths (240 nm, 300 nm, and 380 nm) simultaneously. The microemulsion employed consisted of 2.25 g of SDS, 0.75 g of Brij 35, 6.6 g 1‐butanol, 0.8 g n‐octane, 17.5 g 2‐propanol, and 72.1 g of 10 mM borate buffer (pH 9.2). Detection limits from 0.65 to 6.0 μg/mL were obtained and the calibration plots were linear over at least one order of magnitude for all analytes. The developed method could be applied to the determination of UV filters in several sun protection products including lotions, milks, and oils. Comparison of the obtained data with those from an HPLC method described in the literature showed acceptable agreement. 相似文献
126.
Summary A new system for the rapid and sensitive analysis of underivatized carbohydrates has been established using capillary zone electrophoresis with indirect UV detection. At an applied potential of 28 kV, sugars and sugar acids could be separated by the combined effects of electroendosmosis and electrophoresis within 20 minutes in a fused silica capillary of 50 m internal diameter and an effective length of 100 cm using 6mM sorbic acid, pH 12.1, as both carrier electrolytie and chromophore. The alkaline pH ensured ionization of the sugars and, hence, their detection by means of charge displacement. Furthermore, the chosen concentration of sorbic acid allowed the smallest fractional change in the background signal to be measured. While the electrophoretic mobilities of the sugars were found to increase within a pH range of 11.9 to 12.3, those of the sugar acids were not affected. Due to the increasing competition of hydroxide ions in the displacement of the chromophore with rising pH, a significant loss of sensitivity is observed at pH values higher than 12.1 and this pH was found to provide sufficient resolution, optimum sensitivity, and a acceptably short analysis time. Under these conditions, a lower detection limit of 2 pmol was obtained for glucose. 相似文献
127.
UV/Vis-spectra of Cyclosilanes (SiX
2)
n
withX=Cl, Br, I, OMe andn=4, 5, 6 are recorded and interpreted qualitatively. The spectra exhibit increasing influence of the substituents on the Si-Si-bond system within the rings in the order Cl OMe Br I. At the low energy side of the spectra weak absorption bands, possibly due to intramolecular charge transfer transitions, appear. The strong inductive effect of the electronegative substituents is documented by a marked increase of the first IP's compared to permethylcyclosilanes. 相似文献
128.
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
129.
Vladislav?Tomi?i?Email author Vjekoslav?Butorac Jadranka?Viher Vladimir?Simeon 《Journal of solution chemistry》2005,34(6):613-616
The effect of temperature on the π∗←π transition band in the UV absorption spectrum of NO3−(aq) centered at ≈200 nm was studied in the temperature range 10–70 ∘C. The observed temperature independence of this band was in contrast to the significant influence of temperature on the nitrate π∗←n transition reported recently by us. However, taking into account the electronic states involved in both the transitions, it was concluded that this finding was in accordance with our previous assumption that interconversion between spectrally distinct (with respect to π∗←n band) nitrate species included the rupture/formation of hydrogen bond(s) in the hydration shell of the nitrate ion. 相似文献
130.
A continuous-wave 280 nm light-emitting diode (LED) was used as the excitation source for native fluorescence detection of proteins in CE. The operating current and temperature of the LED were optimized in order to achieve high luminescence power. It was found that a forward current of 30 mA and a temperature of approximately 5 degrees C gave the best S/N. By using a set of two ball lenses to focus light from the LED, we achieved a spot of approximately 200 mum with a power of 0.1-0.2 mW on the detection window. Fluorescence was collected with a ball lens at 90 degrees angle through a bandpass filter onto a photomultiplier tube. In CZE an LOD of 20 nM for conalbumin was reached. In capillary gel electrophoresis all eight proteins from a commercial standard kit were detected with high S/N. For a 10 microg/mL total protein mixture, S/N was better than 3 for all proteins in solution. Further improvement in LOD should be possible on utilization of an LED with higher luminescence power. 相似文献