一种新型的表面声波阻抗传感器及其在液相体系中的应用

一种新型的表面声波阻抗传感器及其在液相体系中的应用姚守拙，陈康，刘德忠，聂利华（湖南大学化学化工系，长沙，４１００８２）关键词表面声波，阻抗传感器，液相应用表面声波传感器（ＳＡＷＳ）具有较高的灵敏度和检测精度，已广泛应用于气体微量组分分析、色谱检测和...     

A fluorescent chemical sensor for Fe based on blocking of intramolecular proton transfer of a quinazolinone derivative

In this paper, 2-(2′-hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), a typical compound that exhibits excited state intramolecular proton transfer (ESIPT) reaction and possesses good photophysical properties, is synthesized and used as fluoroionophore for Fe³⁺ sensitive optochemical sensor. The decrease of fluorescence intensity of HPQ membrane upon the addition of Fe³⁺ was attributed to the blocking of ESIPT reactions of HPQ and quenching its fluorescence. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensor shows a linear response toward Fe³⁺ in the concentration range of 7.1 × 10⁻⁷ M to 1.4 × 10⁻⁴ M with a limit of detection of 8.0 × 10⁻⁸ M, and a working pH range from 2.5 to 4.5. It shows excellent selectivity for Fe³⁺ over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed sensor is applied to the determination of the content of iron ions in pharmaceutical preparations samples with satisfactory results.     

Classification of white wine aromas with an electronic nose

This paper reports the use of a tin dioxide multisensor array based electronic nose for recognition of 29 typical aromas in white wine. Headspace technique has been used to extract aroma of the wine. Multivariate analysis, including principal component analysis (PCA) as well as probabilistic neural networks (PNNs), has been used to identify the main aroma added to the wine. The results showed that in spite of the strong influence of ethanol and other majority compounds of wine, the system could discriminate correctly the aromatic compounds added to the wine with a minimum accuracy of 97.2%.     

Preparation and application of cryptand-coated piezoelectric crystal gas-chromatographic detector

A re-usable and sensitive cryptand-22-coated quartz-crystal membrane piezoelectric sensor with a homemade computer interface for signal acquisition and data processing was prepared and applied as a gas-chromatographic (GC) detector for various organic molecules. The oscillating frequency of the quartz crystal decreased due to the adsorption of organic molecules on cryptand-22. Effects of functional group, molar mass, steric hindrance and polarity of organic molecules on frequency responses of the cryptand-coated piezoelectric crystal detector were investigated. The cryptand-coated piezoelectric crystal GC detector had demonstrated high sensitivity for various polar organic molecules and good reproducibility when re-used. The frequency responses of the cryptand-coated crystal for various molecules were in the following order: carboxylic acids (RCOOH)primary amines (R-NH₂)>alcohols (ROH)>secondary amines (R₂NH)>tertiary amines (R₃N)>ketones. More polar molecules exhibited better frequency responses. The effect of temperature and amount of coating on the frequency responses of cryptand-coated crystal GC detector were also investigated. The cryptand-coated piezoelectric crystal GC detector compared well with the commercial thermal conductivity detector (TCD).     

Effect of the protonation level of poly(o-phenylenediamine) (PoPD) on the ac impedance of humidity-sensitive PoPD/poly(vinyl alcohol) composite film

A composite film consisting of poly(o-phenylenediamine) (PoPD) and poly(vinyl alcohol) (PVA) has been prepared, and the effect of the protonation level of PoPD on the response of the composite to humidity been investigated by ac impedance measurements. The electrochemical system of the PoPD/PVA composite in a humid atmosphere is represented by an electrochemical equivalent circuit containing film (R_film, C_film), Warburg (W) and interfacial (R_ct, C_dl) impedance. R_film was increased with decreasing protonation level of the PoPD in relative humidity regions higher than 40%, but it was almost independent of the protonation level in humidity regions lower than this percentage.     

SDS/n－C5H11OH/n－C7H16/H2O体系中W/O－BI微乳液界面电性质

In the system of SDS/n-C5H11OH/n-C7H16/H2O with the weight ratio of SDS/n-C5H11OH/H2O system at5.0/47.5/47.5, the upper phase of the system was W/O microemulsion, and the lower phase was the bicontinuous microemulsion. When the n-heptane content was less than 1%, with the increase of the n-heptane content, the capacitance (Co, Cod) in the upper phase (W/O) dropped, the capacitance (CB1, CBld) in the lower phase (BI) raised. At the same time, the W/O-BI inteffacial potential (ΔE), capacitance (Ci), and charge-transfer current (ict) decreased.After the n-heptane content reached 1%, with the increase of the n-heptane content, ΔE, Ci and ict demonstrated no significant change.     

Determination of glutamate pyruvate transaminase activity in clinical specimens using a biosensor composed of immobilized l-glutamate oxidase in a photo-crosslinkable polymer membrane on a palladium-deposited screen-printed carbon electrode

The determination of glutamate pyruvate activity (GPT) is of particular clinical importance. A portable GPT sensor for both diagnostic and home-care purpose is highly expected. A highly sensitive and stable l-glutamate sensor was fabricated for the rapid detection of the GPT activity in serum. The sensor is composed of immobilized l-glutamate oxidase in a photo-crosslinkable polymer (PVA-SbQ) membrane on a palladium-deposited screen-printed carbon electrode. The sensor exhibited high sensitivity (detection limit of 50 nM for monosodium glutamate), remarkable long-term stability in storage (5 months in the dry dark state and 1 month in buffer solution) and good reproducibility (R.S.D.=2.6%, n=100). The electrode-to-electrode reproducibility was found to depend on the composition of the polymeric matrix. The optimal substrate composition for the detection of GPT activity was 1 mM α-ketoglutarate and 100 mM l-alanine. The GPT activity in serum can be determined within 3 min. The response of the sensor to GPT activity is linear over the range of 8-250 U/l. Good correlation between the sensor and the Sigma GPT assay kit was achieved (R²=0.9958). The sensor is potentially applicable to a home-care purpose when a portable measuring device is adapted.     

A nanoscale vesicular polydiacetylene sensor for organic amines by fluorescence recovery

We report a nanoscale lipid membrane-based sensor of conjugated polydiacetylene (PDA) vesicles for fluorescence detection of organic amines. The vesicle sensor was constructed by incorporation of a BODIPY fluorescent dye into the PDA vesicles. The fluorescent properties of the resulting vesicles can be manipulated by adjusting lipid components, and are controlled by environmental and solution conditions. The fluorescence of the BODIPY dye was significantly quenched in the polymerization of diacetylene lipid vesicles by a UV irradiation process. However, it was sufficiently recovered by external stimuli such as a hike of solution pH. The fluorescence recovery process was reversible, and a decrease in solution pH resulted in repeated quenching. The reported system transforms an external stimulus into a large fluorescence intensity change, demonstrating great potential in developing new signal reporting method for biosensor design. The quench-recovery phenomenon of the BODIPY-PDA is believed to be related to the energy transfer between the dye and the PDA conjugate backbone. The vesicle sensor was applied for detecting an organic amine, triethylamine (TEA) and a large linear relationship was obtained between the increase in fluorescence intensity and the concentrations of TEA. The detection limit of TEA by vesicle sensors using fluorescence recovery was found to be 10 μM.     

Improving the lower detection limit of potentiometric sensors by covalently binding the ionophore to a polymer backbone

The lower detection limit of polymeric membrane ion-selective electrodes (ISEs) is impaired by zero-current ion fluxes through the organic phase. This adverse effect is largely eliminated by covalently attaching the ionophore to a polymer backbone. To this purpose, the Pb²⁺-selective ligand, 4-tert-butylcalix[4] arene-tetrakis(N,N′-dimethylthioacetamide) is substituted on its upper rim by a diol derivative which is subsequently copolymerized with poly(tetrahydrofuran)diol and 2,2,4-trimethylhexamethylene diisocyanate to the corresponding polyurethane. By measurements on sandwich membranes, it is shown that through binding the ionophore to the polymer, the mobility of Pb²⁺ in the ISE membrane is strongly reduced. As a consequence, the response range of such an ISE is extended by several orders of magnitude. This is the case even when using an internal electrolyte that with an ISE based on a mobile ionophore leads to strong deviations from the linear response because of ion uptake from the sample into the membrane or ion release from the membrane into the sample. With a conventional inner filling solution of 10⁻¹ M Pb(NO₃)₂, a lower detection limit of 1.7×10⁻⁹ M Pb²⁺ has been achieved in the presence of 10⁻⁴ M Na⁺.     

纳米硅胶颗粒的制备及其对金属离子的识别

利用sol-gel方法制得了纳米级的硅胶悬浮液.通过表面化学修饰引入了具有发射荧光能力的萘基基团.在稳态荧光研究中清晰地观察到在微小粒子表面上萘基基团会因溶剂不同而发生重新排组,并呈现出激基缔合物发光.研究了不同过渡金属离子对粒子表面荧光的猝灭效应,发现只有Cu2＋对纳米微球荧光有强烈的猝灭特征,这种优良的选择能力使其有望发展成为一种分析检测Cu2＋的荧光化学敏感器.