pH-dependent H2-activation cycle coupled to reduction of nitrate ion by CpIr complexes.

This paper reports a pH-dependent H2-activation [H2 (pH 1-4) --> H+ + H- (pH -1) --> 2H+ + 2e-] promoted by CpIr complexes [Cp = eta5-C5(CH3)5]. In a pH range of about 1-4, an aqueous HNO3 solution of [CpIr(III)(H2O)3]2+ (1) reacts with 3 equiv of H2 to yield a solution of [(CpIr(III))2(mu-H)3]+ (2) as a result of heterolytic H2-activation [2[1] + 3H2 (pH 1-4) --> [2] + 3H+ + 6H2O]. The hydrido ligands of 2 display protonic behavior and undergo H/D exchange with D+: [M-(H)3-M]+ + 3D+ <==>[M-(D)3-M]+ + 3H+ (where M = CpIr). Complex 2 is insoluble in a pH range of about -0.2 (1.6 M HNO3/H2O) to -0.8 (6.3 M HNO3/H2O). At pH -1 (10 M HNO3/H2O), a powder of 2 drastically reacts with HNO3 to give a solution of [CpIr(III)(NO3)2] (3) with evolution of H2, NO, and NO2 gases. D-labeling experiments show that the evolved H2 is derived from the hydrido ligands of 2. These results suggest that oxidation of the hydrido ligands of 2 [[2] + 4NO3- (pH -1) --> 2[3] + H2 + H+ + 4e-] couples to reduction of NO3- (NO3- --> NO2- --> NO). To complete the reaction cycle, complex 3 is transformed into 1 by increasing the pH of the solution from -1 to 1. Therefore, we are able to repeat the reaction cycle using 1, H2, and a pH gradient between 1 and -1. A conceivable mechanism for the H2-activation cycle with reduction of NO3- is proposed.     

New Building Blocks for the Design of Oligonuclear Copper Complexes Based on Amino Carbohydrates

Remarkably high magnetic coupling and O(2)-activation ability analogous to that of catechol oxidase are characteristics of the first structurally defined, low-symmetry oligonuclear copper complexes of tridentate beta-oxoenamine ligands based on amino carbohydrates (the structure of a bis(acetylbutenonylaminoglucosidato)bis(μ-acetato)tricopper(II) complex is shown).     

Recent advances in electrochemical sensing for hydrogen peroxide: a review

Due to the significance of hydrogen peroxide (H(2)O(2)) in biological systems and its practical applications, the development of efficient electrochemical H(2)O(2) sensors holds a special attraction for researchers. Various materials such as Prussian blue (PB), heme proteins, carbon nanotubes (CNTs) and transition metals have been applied to the construction of H(2)O(2) sensors. In this article, the electrocatalytic H(2)O(2) determinations are mainly focused on because they can provide a superior sensing performance over non-electrocatalytic ones. The synergetic effect between nanotechnology and electrochemical H(2)O(2) determination is also highlighted in various aspects. In addition, some recent progress for in vivo H(2)O(2) measurements is also presented. Finally, the future prospects for more efficient H(2)O(2) sensing are discussed.     

胞苷保护的铜纳米簇新型荧光探针检测重铬酸根离子

基于重铬酸根离子(Cr_2O_7~(2-))对胞苷保护的荧光铜纳米簇(Cu NCs)的猝灭作用,构建了一种可用于检测Cr_2O_7~(2-)的荧光传感器.实验结果表明,该传感体系检测Cr_2O_7~(2-)的线性范围为0.05~7.0μmol/L,检出限为24 nmol/L(S/N=3).该传感器对Cr_2O_7~(2-)的检测具有良好的选择性,可用于湖水样中Cr_2O_7~(2-)的检测.     

Structurally integrated organic light emitting device-based sensors for gas phase and dissolved oxygen

A compact photoluminescence (PL)-based O2 sensor utilizing an organic light emitting device (OLED) as the light source is described. The sensor device is structurally integrated. That is, the sensing element and the light source, both typically thin films that are fabricated on separate glass substrates, are attached back-to-back. The sensing elements are based on the oxygen-sensitive dyes Pt- or Pd-octaethylporphyrin (PtOEP or PdOEP, respectively), which are embedded in a polystyrene (PS) matrix, or dissolved in solution. Their performance is compared to that of a sensing element based on tris(4,7-diphenyl-l,10-phenanthroline) Ru II (Ru(dpp)) embedded in a sol-gel film. A green OLED light source, based on tris(8-hydroxy quinoline Al (Alq3), was used to excite the porphyrin dyes; a blue OLED, based on 4,4'-bis(2,2'-diphenylviny1)-1,1'-biphenyl, was used to excite the Ru(dpp)-based sensing element. The O2 level was monitored in the gas phase and in water, ethanol, and toluene solutions by measuring changes in the PL lifetime tau of the O2-sensitive dyes. The sensor performance was evaluated in terms of the detection sensitivity, dynamic range, gas flow rate, and temperature effect, including the temperature dependence of tau in pure Ar and O2 atmospheres. The dependence of the sensitivity on the preparation procedure of the sensing film and on the PS and dye concentrations in the sensing element, whether a solid matrix or solution, were also evaluated. Typical values of the detection sensitivity in the gas phase, S(g) identical with tau(0% O2)/tau(100% O2), at 23 degrees C, were approximately 35 to approximately 50 for the [Alq3 OLED[/[PtOEP dye] pair; S(g) exceeded 200 for the Alq3/PdOEP sensor. For dissolved oxygen (DO) in water and ethanol, S(DO) (defined as the ratio of tau in de-oxygenated and oxygen-saturated solutions) was approximately 9.5 and approximately 11, respectively, using the PtOEP-based film sensor. The oxygen level in toluene was measured with PtOEP dissolved directly in the solution. That sensor exhibited a high sensitivity, but a limited dynamic range. Effects of aggregation of dye molecules, sensing film porosity, and the use of the OLED-based sensor arrays for O2 and multianalyte detection are also discussed.     

Cooperative Catalysis of Ru(III)-Porphyrin in CO2-Involved Synthesis of Oxazolidinones

CO₂-transformations into high value-added products have become a fascinating area in green chemistry. Herein, a Ru(III)-porphyrin catalyst (RuCl₃ ⋅ 3H₂O−H₂TPP) was found highly efficient in the three-component reaction of CO₂, aliphatic amines and dichloroethane (or its derivative) for synthesis of oxazolidinones in the yields of 71∼91%. It was indicated by means of the control experiments and UV-vis spectra that CO₂ was stoichiometrically activated by the involved aliphatic amine substrates to form a stable carbamate salt while 1,2-dichloroethane (or its derivative) was independently activated by the involved Ru(III)-porphyrin catalyst. The combination of CO₂-activation by aliphatic amines with 1,2-dichloroethane activation by Ru(III)-porphyrin catalyst cooperatively contributed to this successful transformation.     

共价嫁接钌(Ⅱ)配合物SBA-15介孔分子筛的光学氧传感行为

使用P123(EO20PO70EO20)作为表面活性剂, 并通过正硅酸乙酯与含可以水解烷氧基团的[Ru(Phen)2Phen—Si]2+功能化配合物的水解和共缩聚反应, 成功地制备了共价嫁接[Ru(Phen)3]2+分子片断的复合SBA-15介孔杂化材料. 用红外光谱和发光强度猝灭Stern-Volmer曲线对样品进行了表征, 并分别用Demas双格位模型以及Lehrer模型对所获得的复合Ru-SBA-15样品的Stern-Volmer曲线进行了拟合. 实验结果表明, 所制备的传感样品对氧气具有较高的传感灵敏度. 发光分子与分子筛之间产生强有力的CH2—Si化学键使得该杂化材料具有可逆的氧传感信号和较好的光化学稳定性.     

Recoverable solution reaction of HiPco carbon nanotubes with hydrogen peroxide

There is increasing interest in developing single-walled carbon nanotubes (SWNTs)-based optical biosensors for remote or in vitro and in vivo sensing because the near-IR optical properties of SWNTs are very sensitive to surrounding environmental changes. Many enzyme-catalyzed reactions yield hydrogen peroxide (H(2)O(2)) as a product. To our knowledge, there is no report on the interaction of H(2)O(2) with SWNTs from the optical sensing point of view. Here, we study the reaction of H(2)O(2) with an aqueous suspension of water-soluble (ws) HiPco SWNTs encased in the surfactant sodium dodecyl sulfate (SDS). The SWNTs are optically sensitive to hydrogen peroxide in pH 6.0 buffer solutions through suppression of the near-IR absorption band intensity. Interestingly, the suppressed spectral intensity of the nanotubes recovers by increasing the pH, by decomposing the H(2)O(2) into H(2)O and O(2) with the enzyme catalase, and by dialytically removing H(2)O(2). Preliminary studies on the mechanisms suggest that H(2)O(2) withdraws electrons from the SWNT valence band by charge transfer, which suppresses the nanotube spectral intensity. The findings suggest possible enzyme-assisted molecular recognition applications by selective optical detection of biological species whose enzyme-catalyzed products include hydrogen peroxide.     

Construction of sensitive and selective zirconia-based CO sensors using ZnCr2O(4)-based sensing electrodes

The carbon monoxide (CO) sensitivity of a mixed-potential-type yttria-stabilized zirconia (YSZ)-based tubular-type sensor utilizing a ZnCr(2)O(4) sensing electrode (SE) was tuned by the addition of different precious metal nanoparticles (Ag, Au, Ir, Pd, Pt, Ru and Rh; 1 wt % each) into the sensing layer. After measuring the electromotive force (emf) response of the fabricated SEs to 100 ppm of CO against a Pt/air-reference electrode (RE), the ZnCr(2)O(4)-Au nanoparticle composite electrode (ZnCr(2)O(4)(+Au)-SE) was found to give the highest response to CO. A linear dependence on the logarithm of CO concentration in the range of 20-800 ppm at an operational temperature of 550 °C under humid conditions (5 vol % water vapor) was observed. From the characterization of the ZnCr(2)O(4)(+Au)-SE, we can conclude that the engineered high response toward CO originated from the specific properties of submicrometer sized Au particles, formed via the coalescence of nanosized Au particles located on ZnCr(2)O(4) grains, during the calcining process at 1100 °C for 2 h. These particles augmented the catalytic activities of the gas-phase CO oxidation reaction in the SE layer, as well as to the anodic reaction of CO at the interface; while suppressing the cathodic reaction of O(2) at the interface. In addition, the response of the ZnCr(2)O(4)(+Au)-SE sensor toward 100 ppm of CO gradually increased throughout the 10 days of operation, and plateaued for the remainder of the month that the sensor was examined. Correlations between SEM observations and the CO sensing characteristics of the present sensor were suggestive that the sensitivity was mostly affected by the morphology of the Au particles and their catalytic activities, which were in close proximity to the ZnCr(2)O(4) grains. Furthermore, by measuring the potential difference (emf) between the ZnCr(2)O(4)(+Au) and a ZnCr(2)O(4) electrode, sensitivities to typical exhaust component gases other than CO were found to be negligible at 550 °C.     

In2O3/CdO复合材料的制备及气敏特性

采用水热合成方法制备了花状In2O3纳米材料.利用X射线衍射(XRD)、扫描电镜(SEM)、能量色散X射线光谱(EDX)及透射电镜(TEM)对材料的结晶学特性及微结构进行了表征.制备的In2O3材料呈现花状,是由粒径约20nm的椭球状小颗粒构成的分级结构材料.将制备的In2O3与纳米CdO以摩尔比1:1混合后,发现制成的In2O3/CdO复合材料经热处理后呈现葡萄状多孔结构.测试In2O3/CdO复合材料制作的气敏元件处于最佳工作温度(410°C)时,对0.05×10-6(体积分数,φ)的甲醛气体表现出较高的灵敏度.对比测试发现,In2O3/CdO复合材料制作的气敏元件对不同浓度甲醛的灵敏度明显优于纯花状In2O3纳米材料.同时In2O3/CdO复合材料制作的气敏元件在乙醇、甲苯、丙酮、甲醇以及氨气等干扰气体中具有对甲醛良好的选择性.讨论了In2O3/CdO复合材料气敏元件的敏感机理.     

Preparation and bifunctional gas sensing properties of porous In2O3-CeO2 binary oxide nanotubes

The porous binary In(2)O(3)-CeO(2) oxides nanotubes (NTs) in cubic phase were first fabricated by electrospinning (ESP) method and characterized by SEM, TEM, XRD, XPS and UV-vis absorption techniques. By adjusting the In(2)O(3) and CeO(2) molar ratio, the out diameters and wall thicknesses of the final composites were tuned ranging of 90-180 nm and 15-9 nm, respectively. The band gap of the binary oxides gradually decreases, and the ratio of Ce(3+) to Ce(4+) increases with the increase of CeO(2), implying that surface oxygen vacancies gradually increase. The gas sensing test reveals that when the content of CeO(2) is appropriate, the as fabricated In(2)O(3)-CeO(2) NTs could be bifunctional gas sensors to detect H(2)S at low temperature(25-110 °C) while acetone at relative high temperature (300 °C). The In(75)Ce(25) NTs sensor is an optimum one, which exhibits the highest response of 498 to H(2)S at 80 °C and the highest response of 30 to acetone at 300 °C. In contrast to the pure In(2)O(3) sensor, the response and recovery times, as well as the sensing reaction barrier height, for In(75)Ce(25) both degrade considerably. The above temperature-dependent sensing properties were attributed to two different gas sensing mechanisms, sulfuration at low temperature and adsorption at high temperature.     

Luminescence Quenching Behavior of Oxygen Sensing ORMOSIL Films Based on Ruthenium Complex

An organically modified silicate(ORMOSIL) based optical sensor response to gaseous O2 or O2 dissolved in water is presented. The oxygen sensing film mechanism is based on the principle of fluorescence quenching of tris(4,7-diphenyl-l , 10-phenanthroline) ruthenium ( ) ([Ru(dpp)3]2+), which has been entrapped in a porous ORMOSIL film. In order to establish optimum film-processing parameters, comprehensive investigations, including the effects of the polarity and the hydrophobicity of the sensing film on oxygen quenching response and response time, were carried out. The film hydrophobicity increased as a function of dimethyl-dimethoxysilane (DiMe-DMOS) content, which is correlated with enhanced oxygen sensor performance. The sensor developed in the present work exhibits the advantages of fast response time and good reversibility. The detection limits are 0. 5 % and 0. 3 g/mL for O2 in the gaseous and the aqueous phases, respectively.     

Glucose and choline on-line biosensors based on electropolymerized Meldola's blue

Electropolymerized film of Meldola's blue (MB) was prepared and demonstrated as electron shuttle between the immobilized horse peroxidase (HRP) and glassy carbon electrode (GCE) for sensing hydrogen peroxide (H(2)O(2)) produced by enzyme catalytical reactions. Electrochemical polymerization of Meldola's blue was carried out by cyclic voltammetry (CV) in a phosphate buffer solution (pH 7.00) in a potential window from -0.60 to +1.30 V. The pH of the electropolymerization solution was found to be closely related to the resulted polymeric MB and the best polymeric film was obtained in a pH 7.00 phosphate buffer. The polymeric MB was demonstrated to shuttle the electron transfer between the immobilized HRP and GCE and utilized as a mediator for HRP immobilized biosensor for biocatalytical reduction of H(2)O(2) at a potential of -0.30 V (versus AgCl/Ag). The H(2)O(2) sensing system was applied to construct glucose and choline on-line sensors by wiring H(2)O(2) produced by enzyme oxidase catalytical reaction. The possibility of these sensors as on-line detectors for on-line and continuous measurement was explored off-line. The operating potential, interference, and lifetime of these sensors were also examined.     

α-Fe2O3负载Ag复合纳米材料的制备、表征和气敏性能

采用简单的FeCl3溶液水热方法, 结合焙烧处理合成了α-Fe2O3 纳米粉体; 以所制备的α-Fe2O3为载体负载Ag纳米粒子, 得到Ag/α-Fe2O3 复合纳米材料. 使用X射线衍射、 透射电子显微镜、 氮气吸附-脱附和X射线光电子能谱等对样品进行表征, 并考察了Ag/α-Fe2O3复合材料在260℃下对甲醇、 乙醇、 乙醚、 丙酮、 正丁醇和正己醇等挥发性有机物的气敏行为. 结果表明, Ag/α-Fe2O3传感器对这几种挥发性有机物展示了较高的灵敏度和快速、 可逆的响应-恢复特性; 与纯α-Fe2O3相比, Ag/α-Fe2O3复合材料的气敏性能显著提高, 这可能与该复合材料表面独特的多孔结构和活性Ag纳米粒子对敏感反应的催化作用有关.     

Preparation of porous α-Fe2O3-supported Pt and its sensing performance to volatile organic compounds

Porous α-Fe2O3 was synthesized by a simple hydrothermal treatment of FeCl3 aqueous solution followed by a calcination process. In the synthesis of porous α-Fe2O3, no templates or pore-directing agents were used. The as-prepared porous α-Fe2O3 was further employed as a support for loading Pt nanoparticles. The gas sensing performance of the obtained porous α-Fe2O3-supported Pt to VOCs was investigated. The sensor presented a high response and fast response-recovery characteristic to several VOCs including acetone, ether, methanol, ethanol, butanol and hexanol. Meanwhile, it exhibited a much higher response than the pure α-Fe2O3 at the operating temperature of 260°C. The enhanced sensing properties may be related to the unique porous structure of the α-Fe2O3 support and the promoting effect of active Pt nanoparticles for the sensing reactions.     

Controllable synthesis of Y2O3 microstructures for application in cataluminescence gas sensing

Y(2)O(3) dumbbells, microspheres, and nanosheets were synthesized by a facile hydrothermal procedure followed by calcination. Electron microscopy, X-ray diffraction, and N(2) adsorption measurements were used to characterize the yttrium oxide microstructures. On the basis of a time-dependent study of nanostructure evolution and the effect of other processing parameters, a kinetic "homogeneous nucleation-self assembly-anisotropic growth" mechanism is proposed to explain the growth of these microstructures under hydrothermal conditions. The sensitivity of as-prepared Y(2)O(3) structures to a series of gaseous chemicals was examined by using a homemade cataluminescence sensing system. The designed cataluminescence sensor based on the yttrium oxide dumbbells shows good sensing performance for 16 common volatile organic compounds.     

H2O broadening of a CO2 line and its nearest neighbors near 6360 cm(-1)

Remote sensing of CO(2) requires high-fidelity reference data of spectral line parameters to be successful. The 6360 cm(-1) region is commonly used by satellites, field campaigns, and point-source gas sensors because it contains well-characterized and relatively isolated transitions of appropriate line strengths for atmospheric applications. However, the presence of gases other than CO(2), N(2), and O(2) can be a source of uncertainty for atmospheric measurements. Near 6360 cm(-1), there are numerous H(2)O and HDO transitions. Water makes up approximately 1-4% of Earth's lower atmosphere and can interfere with remote sensing measurements by (1) appearing as a direct spectral interference or (2) acting as a foreign broadener for CO(2) lines. The primary goal of this work was to quantify H(2)O broadening of CO(2) through precision spectroscopy measurements on the R16e transition at 6359.967 cm(-1) and its two nearest neighbors. A secondary goal was to assess the accuracy of H(2)O reference line parameters in the HITRAN 2008 database for spectrally removing typical levels of moisture from air samples containing approximately 400 ppm of CO(2).     

Gas sensing with nano-indium oxides (In2O3) prepared via continuous hydrothermal flow synthesis

A rapid, clean, and continuous hydrothermal route to the synthesis of ca. 14 nm indium oxide (In(2)O(3)) nanoparticles using a superheated water flow at 400 °C and 24.1 MPa as a crystallizing medium and reagent is described. Powder X-ray diffraction (XRD) of the particles revealed that they were highly crystalline despite their very short time under hydrothermal flow conditions. Gas sensing substrates were prepared from an In(2)O(3) suspension via drop-coating, and their gas sensing properties were tested for response to butane, ethanol, CO, ammonia, and NO(2) gases. The sensors showed excellent selectivity toward ethanol, giving a response of 18-20 ppm.     

Label-free fluorescent detection of thrombin using G-quadruplex-based DNAzyme as sensing platform

We report herein a label-free and sensitive fluorescent method for detection of thrombin using a G-quadruplex-based DNAzyme as the sensing platform. The thrombin-binding aptamer (TBA) is able to bind hemin to form the G-quadruplex-based DNAzyme, and thrombin can significantly enhance the activity of the G-quadruplex-based DNAzyme. The G-quadruplex-based DNAzyme is found to effectively catalyze the H(2)O(2)-mediated oxidation of thiamine, giving rise to fluorescence emission. This allows us to utilize the H(2)O(2)-thiamine fluorescent system for the quantitative analysis of thrombin. The assay shows a linear toward thrombin concentration in the range of 0.01-0.12 nM. The present limit of detection for thrombin is 1 pM, and the sensitivity for analyzing thrombin is improved by about 10,000-fold as compared with the reported colorimetric counterpart. The work also demonstrates that thiamine is an excellent substrate for the fluorescence assay using the G-quadruplex-based DNAzyme as the sensing platform.     

Nickel oxide Nanoparticles/Carbon Nanotubes Nanocomposite for Non-enzymatic Determination of Hydrogen Peroxide

In this work, nickel oxide nanoparticles-modified multi-walled carbon nanotubes (CNTs) were prepared and used for H2O2 sensing application. Firstly, ex situ NiO nanoparticles (NPs) were prepared and further used to decorate polyethylenimine (PEI)-modified carboxylated CNTs. The obtained nanocomposite and its precursors were identified by using X-ray diffraction, thermal analysis, Raman spectroscopy and SEM and TEM images, N2 adsorption-desorption isotherms, and electrochemical techniques. The sensing properties of the NiO-modified nanocomposite toward H2O2 were studied by electrochemical techniques using glassy carbon electrodes (GCEs) as support material. After optimizing the sensor construction, the sensor sensitivity was about of 0.83±0.01 A M⁻¹ cm⁻² with a LOD of about 1.0 μM. In addition, it showed excellent anti-interference properties, reproducibility, and stability (over 4 months). Finally, such sensors were coupled to a flow injection device and the H2O2 concentration of some commercial antiseptic solutions were successfully obtained (with recovery ratios between 96.3–102.4 %).