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Sensing Materials (sensing + material)
Selected AbstractsA novel gaseous dimethylamine sensor utilizing cataluminescence on zirconia nanoparticlesLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 5 2009Chao Yu Abstract A novel cataluminescence (CTL) sensor using ZrO2 nanoparticles as the sensing material was developed for the determination of trace dimethylamine in air samples based on the catalytic chemiluminescence (CL) of dimethylamine on the surface of ZrO2 nanoparticles. The CTL characteristics and the different factors on the signal intensity for the sensor, including nanomaterials, working temperature, wavelength and airflow rate, were investigated in detail. The CL intensity on ZrO2 nanoparticles was the strongest among the seven examined catalysts. This novel CL sensor showed high sensitivity and selectivity to gaseous dimethylamine at optimal temperature of 330°C. Quantitative analysis was performed at a wavelength of 620 nm. The linear range of CTL intensity vs concentration of gaseous dimethylamine was 4.71 × 10,3 to 7.07 × 10,2 mg L,1 (r = 0.9928) with a detection limit (3,) of 6.47 × 10,4 mg L,1. No or only very low levels of interference were observed while the foreign substances such as benzene, hydrochloric acid, methylbenzene, chloroform, n -hexane and water vapor were passing through the sensor. The response time of the sensor was less than 50 s, and the sensor had a long lifetime of more than 60 h. The sensor was successfully applied to the determination of dimethylamine in artificial air samples, and could potentially be applied to analysis of nerve agents such as Tabun (GA). Copyright © 2009 John Wiley & Sons, Ltd. [source] Development of a benzaldehyde sensor utilizing chemiluminescence on nanosized Y2O3LUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 6 2008Yayan Wu Abstract A chemiluminescence sensor has been proposed for sensitive determination of benzaldehyde, with nanosized Y2O3 as the sensing material. Under optimized conditions, the linear range of the CL intensity vs. the concentration of benzaldehyde vapour is 1.8 ng/mL,10.8 µg/mL (r2 = 0.9996), with a detection limit of 0.90 ng/mL (signal:noise ratio = 3:1). The sensor also exhibits high selectivity to benzaldehyde because no or weak CL signals have been detected when foreign substances are introduced into the sensor. In addition, the sensor also shows good stability and longer lifetime within 100 h. The results indicate that the proposed sensor, which has high sensitivity and selectivity, shows great potential for the detection of benzaldehyde. Copyright © 2008 John Wiley & Sons, Ltd. [source] Electrical Response to Organic Vapor of Conductive Composites from Amorphous Polymer/Carbon Black Prepared by Polymerization FillingMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2003Jun Rong Li Abstract In recent years, conductive polymer composites have found applications as gas sensors because of their sudden change in electric resistance of several orders of magnitude when the materials are exposed to certain solvent vapors. However, the composites having this function reported so far are mostly based on crystalline polymeric matrices, which factually sets a limit to materials selection. The present work prepares polystyrene/carbon black composites through polymerization filling and proves that the amorphous polymer composites can also serve as gas sensing materials. The composites' percolation threshold is much lower than that of the composites produced by dispersive mixing. In addition, high responsivity to some organic vapors coupled with sufficient reproducibility is acquired. The experimental data show that molecular weight and molecular weight distribution of the matrix polymer and conducting filler content exert great influence on the electrical response behavior of the composites. As a result, composites performance can be purposely tailored accordingly. Compared with the approaches of melt-blending and solution-blending, the current technique is characterized by many advantages, such as simplicity, low cost, and easy to be controlled. Effect of different organic solvent vapors on the electric resistance of PS/CB composites (CB content,=,10.35 vol.-%). [source] Electrically conductive sensors for liquids based on ternary immiscible polymer blends containing polyanilinePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2004H. Cooper Abstract Electrically conductive blends, containing two immiscible polymers (ethylene vinyl acetate, EVA-19, and copolyamide 6/6.9, CoPA) and polyaniline (PANI), were produced by melt processing. These blends showed a preferred localization of PANI in the CoPA phase, thus enhancing the formation of continuous conducting networks. Electrically conductive PANI-containing filaments produced by a capillary rheometer process at various shear rate levels were studied as sensing materials for a homologous series of alcohols (methanol, ethanol and 1-propanol). All filaments showed a decreasing resistance upon exposure to these solvents. Filaments exposed to methanol, liquid or vapor, exhibited the highest resistance decrease. This behavior was related to the highest polarity of methanol, compared with ethanol and 1-propanol. The filaments' rate of production significantly affects the relative resistance change upon exposure to the various alcohols and their reproducibility. Copyright © 2004 John Wiley & Sons, Ltd. [source] Versatile Self-Complexing Compounds Based on Covalently Linked Donor,Acceptor CyclophanesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2005Yi Liu Dr. Abstract A range of covalently linked donor,acceptor compounds which contain 1) a hydroquinone (HQ) unit, 2) a 1,5-dioxynaphthalene (DNP) ring system, or 3) a tetrathiafulvalene (TTF) unit as the ,-donor, and 4) cyclobis(paraquat- p -phenylene) (CBPQT4+) as the ,-accepting tetracationic cyclophane were prepared and shown to operate as simple molecular machines. The ,-donating arms can be included inside the cyclophane in an intramolecular fashion by virtue of stabilizing noncovalent bonding interactions. What amounts to self-complexing/decomplexing equilibria were shown to be highly temperature dependent when the ,-donating arm contains either an HQ or DNP moiety. The thermodynamic parameters associated with the equilibria have been unraveled by using variable-temperature 1H NMR spectroscopy. The negative ,H° and ,S° values account for the fact that the "uncomplexed" conformation becomes the dominant species, since the entropy gain associated with the decomplexation process overcomes the enthalpy loss resulting from the breaking of the donor,acceptor interactions. The arm's in-and-out movements with respect to the linked cyclophanes can be arrested by installing a bulky substituent at the end of the arm. In the case of compounds carrying a DNP ring system in their side arm, two diastereoisomeric, self-complexing conformations are observed below 272 K in hexadeuterioacetone. By contrast, control over the TTF-containing arm's movement is more or less ineffective through the thermally sensitive equilibrium although it can be realized by chemical and electrochemical ways as a result of TTF's excellent redox properties. Such self-complexing compounds could find applications as thermo- and electroswitches. In addition, the thermochromism associated with the arm's movement could lead to some of the compounds finding uses as imaging and sensing materials. [source] | |||||||||||||