Chemical Sensors for Electronic Nose Systems

Chemical sensors have been widely used for the analysis of volatile organic compounds. Employing chemical sensors in an array format with pattern recognition provides a higher degree of selectivity and reversibility leading to an extensive range of applications. When such systems are used for odour analysis they are termed electronic noses. Application of electronic noses ranges from the food industry, medical industry to environmental monitoring and process control. Many types of different gas sensors have been employed in the array. These include conducting polymers, metal oxide semiconductors, piezoelectric, optical fluorescence and amperometric gas sensors The transducer principle of these sensors is varied and is discussed in detail within this review. Examples of the current trends in sensor array technology as well as the applications to which the sensor-based noses have been applied are also discussed.     

[Cr2CoO（O2CCH3）6Py3].Py簇合物的分子结构和电子结构

合成并测定了标题化合物的分子结构,Ca空间群,a=2.1933(2)nm,b=1.2447(3)nm,c=1.5912(5)nm,β=117.02(2)°,I＇=3.8679 nm~3,Z=4,最后根据I>3G(I)的2849个独立衍射点的强度数据,把结构精修到R=0.036.在晶体结构测定基础上进行了EHMO计算,以研究其簇骼成键性质,结果表明,该分子虽不存在金属-金属键,但M与μ-O之间除了σ键外,还存在四中心d-ρπ键,它是该类化合物稳定的主要因素。     

Electron correlation effects on the shape of the Kohn–Sham molecular orbital

Even systems in which strong electron correlation effects are present, such as the large near-degeneracy correlation in a dissociating electron pair bond exemplified by stretched H₂, are represented in the Kohn–Sham (KS) model of non-interacting electrons by a determinantal wavefunction built from the KS molecular orbitals. As a contribution to the discussion on the status and meaning of the KS orbitals we investigate, for the prototype system of H₂ at large bond distance, and also for a one-dimensional molecular model, how the electron correlation effects show up in the shape of the KS σ _g orbital. KS orbitals φ^HL and φ^FCI obtained from the correlated Heitler-London and full configuration interaction wavefunctions are compared to the orbital φ^LCAO, the traditional linear combination of atomic orbitals (LCAO) form of the (approximate) Hartree-Fock orbital. Electron correlation manifests itself in an essentially non-LCAO structure of the KS orbitals φ^HL and φ^FCI around the bond midpoint, which shows up particularly clearly in the Laplacian of the KS orbital. There are corresponding features in the kinetic energy density t _s of the KS system (a well around the bond midpoint) and in the one-electron KS potential v _s (a peak). The KS features are lacking in the Hartree-Fock orbital, in a minimal LCAO approximation as well as in the exact one. Received: 11 December 1996 / Accepted: 10 January 1997     

电子亲和势法判断负离子聚合单体的活性

提出了利用不同取代基烯类单体的电子亲和势来判断其负离子聚合反应活性的方法.采用密度泛函理论的B3LYP/6-31G(d)方法优化了不同取代基烯类单体几何构型,在B3LYP/6-311++G(3df,2p)水平上计算了其电子亲和势.通过电子亲和势计算值与文献报道实验数据比较,表明本文采用的计算方法是比较可靠的.结合不同取代基烯类单体的电子亲和势的计算结果,通过与Q-e关系及取代基常数σ数据进行比较表明,电子亲和势可以用来判断不同单体负离子聚合反应的活性高低.     

The Difference of Electronic Properties and the Effect of Hydrogen－bondofcis－and trans－Polyazomethine

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Some ruthenium complexes containing cyanocarbon ligands: syntheses, structures and extent of electronic communication in binuclear systems

The preparation of several ruthenium complexes containing cyanocarbon anions is reported. Deprotonation (KOBu^t) of [Ru(NCCH₂CN)(PPh₃)₂Cp]PF₆ (1) gives Ru{NCCH(CN)}(PPh₃)₂Cp (2), which adds a second [Ru(PPh₃)₂Cp]⁺ unit to give [{Ru(PPh₃)₂Cp}₂(μ-NCCHCN)]⁺ (3). Attempted deprotonation of the latter to give the μ-NCCCN complex was unsuccessful. Similar chemistry with tricyanomethanide anion gives Ru{NCC(CN)₂}(PPh₃)₂Cp (4) and [{Ru(PPh₃)₂Cp}₂{μ-NCC(CN)CN}]PF₆ (5), and with pentacyanopropenide, Ru{NCC(CN)C(CN)C(CN)₂}(PPh₃)₂Cp (6) and [{Ru(PPh₃)₂Cp}₂{μ-NCC(CN)C(CN)C(CN)CN}]PF₆ (7). The Ru(dppe)Cp* analogues of 6 and 7 (8 and 9) were also prepared. Thermolysis of 6 (refluxing toluene, 12 h) results in loss of PPh₃ and formation of the binuclear cyclic complex {Ru(PPh₃)Cp[μ-NC{C(CN)C(CN)₂}CN]}₂ (10). The solid-state structures of 2-4 and 8-10 have been determined and the nature of the isomers shown to be present in solutions of the binuclear cations 7 and 9 by NMR studies has been probed using Hartree-Fock and density functional theory.     

Sequential injection system with higher dimensional electrochemical sensor signals Part 1. Voltammetric e-tongue for the determination of oxidizable compounds

A sequential injection analysis (SIA) system was developed with the aim of obtaining an automatic and versatile way to prepare standards needed in the study of systems with higher dimensional sensor signals. To illustrate this, different analytical techniques were used in determinations of several analytes. Automated potentiometric calibrations of different potentiometric sensors, with and without interference, were carried out. Useful determinations of selectivity coefficients with two degrees of freedom were obtained. Simultaneous voltammetric determinations have also been done. Firstly, simultaneous determinations of lead and cadmium, using epoxy-graphite composite as the working electrode, have enabled a separate calibration for each metal to be obtained. Next, a voltammetric electronic tongue was designed and applied to the determination of oxidizable species. The use of artificial neural networks has solved the overlapped signal of ascorbic acid, 4-aminophenol and 4-acetamidophenol (paracetamol). A set of 63 data points was prepared automatically and has facilitated the training of an electronic tongue for these three analytes. Accurate predictions of test solutions, in the range of 12–410 μM for ascorbic acid, 17–530 μM for 4-aminophenol and 10–420 μM for paracetamol, have been achieved with RMSEs lower than 0.10 μM.     

A practical approach to the implementation of autoverify

Autoverification is a process in which computer software will automatically evaluate laboratory test results, verify result integrity, and then release the results to the hospital interface without any technologist intervention. Autoverify release criteria are user defined and can be customized. The process of developing, implementing, and monitoring autoverify is achievable for most test results in laboratory medicine. The use of autoverification will improve result quality, increase revenue, and create faster turn-around times. All of this put together will ultimately lead to improved customer satisfaction. Computers and autoverification are survival tools in the competitive market of laboratory diagnostics services.Presented at the 8th Conference on Quality in the Spotlight, 17–18 March 2003, Antwerp, Belgium     

Direct calculation of ionization potentials of closed-shell atoms and molecules

Vertical ionization potentials, electron affinities and information about quasi-particles can be obtained by using the technique of the single-particle propagator. The expansion of the self-energy part up to third order perturbation theory can be evaluated numerically, but does not lead, in most cases, to satisfying results. A theoretical and numerical analysis of the diagrammatic expansion of the self-energy part requires the introduction of a renormalized interaction and renormalized hole and particle lines.     

(A19N7)[In4]2 (A = Ca,Sr) and (Ca4N)[In2]: Synthesis,Crystal Structures,Physical Properties,and Chemical Bonding

Single phase powders of (A₁₉N₇)[In₄]₂ (A = Ca, Sr) and (Ca₄N)[In₂] were prepared by reaction of melt beads of the metallic components with nitrogen. The crystal structure of (Ca₁₉N₇)[In₄]₂ was refined based on neutron and X‐ray powder diffraction data. The crystal structure of (Sr₁₉N₇)[In₄]₂ was solved from the X‐ray powder pattern. The structure refinements in combination with results from chemical analyses ascertain the compositions. The compounds (A₁₉N₇)[In₄]₂ (A = Ca, Sr) are isotypes of (Ca₁₉N₇)[Ag₄]₂; (Ca₁₉N₇)[In₄]₂ is probably identical to the earlier reported (Ca_18.5N₇)[In₄]₂. The crystal structure of the isotypes (A₁₉N₇)[In₄]₂ (A = Ca, Sr; cubic, , Ca: a = 1471.65(3) pm; Sr: a = 1561.0(1) pm) contains isolated [In₄] tetrahedra embedded in a framework of edge‐ and vertex‐sharing (A₆N) octahedra. Six of these octahedra are condensed by edge‐sharing around one central A²⁺ ion to form “superoctahedra” (A₁₉N₆) which are connected three‐dimensionally via further octahedra by corner‐sharing. The crystal structure of (Ca₄N)[In₂] (tetragonal, I4₁/amd, a = 491.14(4) pm, c = 2907.7(3) pm) consists of alternating layers of perovskite type slabs of vertex‐sharing octahedra (Ca₂Ca_4/2N) and parallel arranged infinite zigzag chains equation/tex2gif-stack-1.gif[In₂]. In the sense of Zintl‐type counting the compounds (A²⁺)₁₉(N^3?)₇[(In^2.125?)₄]₂ present an electron excess, (Ca²⁺)₄(N^3?)[(In^2.5?)₂] is electron deficient. Metallic properties are supported by electrical resistivity and magnetic susceptibility measurements. The analysis of the electronic structures gives evidence for the existence of homoatomic interactions In–In and significant heteroatomic metal–metal interactions Ca–In which favor the deviations of the title compounds from the (8 – N) rule.