TY - CHAP A1 - Katz, Eugenii A1 - Willner, Itamar T1 - Magneto-controlled quantized electron transfer to surface-confined redox units and metal nanoparticles N2 - Hydrophobic magnetic nanoparticles (NPs) consisting of undecanoate-capped magnetite (Fe3O4, average diameter ca. 5 nm) are used to control quantized electron transfer to surface-confined redox units and metal NPs. A two-phase system consisting of an aqueous electrolyte solution and a toluene phase that includes the suspended undecanoatecapped magnetic NPs is used to control the interfacial properties of the electrode surface. The attracted magnetic NPs form a hydrophobic layer on the electrode surface resulting in the change of the mechanisms of the surface-confined electrochemical processes. A quinone-monolayer modified Au electrode demonstrates an aqueous-type of the electrochemical process (2e-+2H+ redox mechanism) for the quinone units in the absence of the hydrophobic magnetic NPs, while the attraction of the magnetic NPs to the surface results in the stepwise single-electron transfer mechanism characteristic of a dry nonaqueous medium. Also, the attraction of the hydrophobic magnetic NPs to the Au electrode surface modified with Au NPs (ca. 1.4 nm) yields a microenvironment with a low dielectric constant that results in the single-electron quantum charging of the Au NPs. KW - Biosensor KW - Nanoparticles KW - magnetic particles KW - quantum charging KW - modified electrode Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:a96-opus-1528 ER - TY - CHAP A1 - Pijanowska, Dorota G. A1 - Remiszewska, Elzbieta T1 - pH-based detection of phenylalnine by potentiometric and colorimetric methods N2 - In this paper, methods of sample preparation for potentiometric measurement of phenylalanine are presented. Basing on the spectrophotometric measurements of phenylalanine, the concentrations of reagents of the enzymatic reaction (10 mM L-Phe, 0,4 mM NAD+, 2U L-PheDH) were determined. Then, the absorption spectrum of the reaction product, NADH, was monitored (maximum peak at 340 nm). The results obtained by the spectrophotometric method were compared with the results obtained by the colourimetry, using pH indicators. The above-mentioned two methods will be used as references for potentiometric measurements of phenylalanine concentration. KW - Biosensor KW - Phenylalanine determination KW - enzymatic methods KW - pH-based biosensing Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:a96-opus-1536 ER - TY - CHAP A1 - Arida, Hassan A. A1 - Kloock, Joachim P. A1 - Schöning, Michael Josef T1 - Novel organic membrane-based thin-film microsensors for the determination of heavy metal cations N2 - A first step towards the fabrication and electrochemical evaluation of thin-film microsensors based on organic PVC membranes for the determination of Hg(II), Cd(II), Pb(II) and Cu(II) ions in solutions has been realised. The membrane-coating mixture used in the preparation of this new type of microsensors is incorporating PVC as supporting matrix, o-nitrophenyloctylether (o-NPOE) as solvent mediator and a recently synthesized Hg[dimethylglyoxime(phene)]2+ and Bis-(4-hydroxyacetophenone)-ethylenediamine as electroactive materials for Hg(II) and Cd(II), respectively. A set of three commercialised ionophores for Cd(II), Pb(II) and Cu(II) has been also used for comparison. Thin-film microsensors based on these membranes showed a Nernstian response of slope (26-30 mV/dec.) for the respective tested cations. The potentiometric response characteristics (linear range, pH range, detection limit and response time) are comparable with those obtained by conventional membranes as well as coated wire electrodes prepared from the same membrane. The realisation of the new organic membrane-based thin-film microsensors overcomes the problem of an insufficient selectivity of solid-state-based thinfilm sensors. KW - Biosensor KW - Heavy metal detection KW - thin-film microsensors KW - organic PVC membranes Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:a96-opus-1545 ER - TY - CHAP A1 - Barek, Jiri A1 - Fischer, Jan A1 - Navratil, Tomas A1 - Peckova, Karolina A1 - Yosypchuk, Bogdan T1 - Silver solid amalgam electrodes as sensors for chemical carcinogens N2 - The applicability of differential pulse voltammetry (DPV) and adsorptive stripping voltammetry (AdSV) at a non-toxic meniscus-modified silver solid amalgam electrode (m-AgSAE) for the determination of trace amounts of genotoxic substances was demonstrated on the determination of micromolar and submicromolar concentrations of 3-nitrofluoranthene using methanol - 0.01 mol L-1 NaOH (9:1) mixture as a base electrolyte and of Ostazine Orange using 0.01 mol L-1 NaOH as a base electrolyte. KW - Biosensor KW - Solid amalgam electrodes KW - voltammetry KW - carcinogens KW - 3-nitrofluoranthene KW - Ostazine Orange Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:a96-opus-1554 ER - TY - CHAP A1 - Baronas, Romas A1 - Ivanauskas, Feliksas A1 - Kulys, Juozas T1 - Mathematical modeling of biosensors based on an array of enzyme microreactors N2 - This paper presents a two-dimensional-in-space mathematical model of biosensors based on an array of enzyme microreactors immobilised on a single electrode. The modeling system acts under amperometric conditions. The microreactors were modeled by particles and by strips. The model is based on the diffusion equations containing a nonlinear term related to the Michaelis-Menten kinetics of the enzymatic reaction. The model involves three regions: an array of enzyme microreactors where enzyme reaction as well as mass transport by diffusion takes place, a diffusion limiting region where only the diffusion takes place, and a convective region, where the analyte concentration is maintained constant. Using computer simulation, the influence of the geometry of the microreactors and of the diffusion region on the biosensor response was investigated. The digital simulation was carried out using the finite difference technique. KW - Biosensor KW - Reaction-diffusion KW - modeling biosensor KW - microreactor Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:a96-opus-1569 ER - TY - CHAP A1 - Lei, Yu A1 - Mulchandani, Priti A1 - Chen, Wilfred A1 - Mulchandani, Ashok T1 - Biosensor for direct determination of fenitrothion and EPN using recombinant Pseudomonas putida JS444 with surface expressed organophosphorus hydrolase. 1. modified clark oxygen electrode N2 - This paper reports a first microbial biosensor for rapid and cost-effective determination of organophosphorus pesticides fenitrothion and EPN. The biosensor consisted of recombinant PNP-degrading/oxidizing bacteria Pseudomonas putida JS444 anchoring and displaying organophosphorus hydrolase (OPH) on its cell surface as biological sensing element and a dissolved oxygen electrode as the transducer. Surfaceexpressed OPH catalyzed the hydrolysis of fenitrothion and EPN to release 3-methyl-4-nitrophenol and p-nitrophenol, respectively, which were oxidized by the enzymatic machinery of Pseudomonas putida JS444 to carbon dioxide while consuming oxygen, which was measured and correlated to the concentration of organophosphates. Under the optimum operating conditions, the biosensor was able to measure as low as 277 ppb of fenitrothion and 1.6 ppm of EPN without interference from phenolic compounds and other commonly used pesticides such as carbamate pesticides, triazine herbicides and organophosphate pesticides without nitrophenyl substituent. The applicability of the biosensor to lake water was also demonstrated. KW - Biosensor KW - Organophosphorus KW - fenitrothion KW - EPN KW - biosensor KW - Pseudomonas putida Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:a96-opus-1573 ER - TY - CHAP A1 - Näther, Niko A1 - Juárez, Leon M. A1 - Emmerich, Rüdiger A1 - Berger, Jörg A1 - Friedrich, Peter A1 - Schöning, Michael Josef T1 - Detection of hydrogen peroxide (H2O2) at exposed temperatures for industrial processes N2 - An H2O2 sensor for the application in industrial sterilisation processes has been developed. Therefore, automated sterilisation equipment at laboratory scale has been constructed using parts from industrial sterilisation facilities. In addition, a software tool has been developed for the control of the sterilisation equipment at laboratory scale. First measurements with the developed sensor set-up as part of the sterilisation equipment have been performed and the sensor has been physically characterised by optical microscopy and SEM. KW - Biosensor KW - Gas sensor KW - hydrogen peroxide KW - sterilisation KW - catalytic decomposition Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:a96-opus-1418 ER - TY - CHAP A1 - Wagner, Thorsten A1 - Kohl, Claus-Dieter A1 - Fröba, Michael A1 - Tiemann, Michael T1 - Gas sensing properties of ordered mesoporous SnO2 N2 - We report on the synthesis and CO gas-sensing properties of mesoporous tin(IV) oxides (SnO2). For the synthesis cetyltrimethylammonium bromide (CTABr) was used as a structure-directing agent; the resulting SnO2 powders were applied as films to commercially available sensor substrates by drop coating. Nitrogen physisorption shows specific surface areas up to 160 m2·g-1 and mean pore diameters of about 4 nm, as verified by TEM. The film conductance was measured in dependence on the CO concentration in humid synthetic air at a constant temperature of 300 °C. The sensors show a high sensitivity at low CO concentrations and turn out to be largely insensitive towards changes in the relative humidity. We compare the materials with commercially available SnO2-based sensors. KW - Biosensor KW - Tin oxide KW - sensing properties KW - CO KW - humidity Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:a96-opus-1422 ER - TY - CHAP A1 - Mirmohseni, Abdolreza A1 - Rostamizadeh, Kobra T1 - Quartz crystal nanobalance in conjunction with principal component analysis for identification of volatile organic compounds N2 - Quartz crystal nanobalance (QCN) sensors are considered as powerful masssensitive sensors to determine materials in the sub-nanogram level. In this study, a single piezoelectric quartz crystal nanobalance modified with polystyrene was employed to detect benzene, toluene, ethylbenzene and xylene (BTEX compounds). The frequency shift of the QCN sensor was found to be linear against the BTEX compound concentrations in the range about 1-45 mg l-1. The correlation coefficients for benzene, toluene, ethylbenzene, and xylene were 0.991, 0.9977, 0.9946 and 0.9971, respectively. The principal component analysis was also utilized to process the frequency response data of the single piezoelectric crystal at different times, considering to the different adsorption-desorption dynamics of BTEX compounds. Using principal component analysis, it was found that over 90% of the data variance could still be explained by use of two principal components (PC1 and PC2). Subsequently, the successful identification of benzene and toluene was possible through the principal component analysis of the transient responses of the polystyrene modified QCN sensor. The results showed that the polystyrene-modified QCN had favorable identification and quantification performances for the BTEX compounds. KW - Biosensor KW - Quartz crystal nanobalance (QCN) KW - BTEX compounds KW - principal component Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:a96-opus-1434 ER - TY - CHAP A1 - Kreutz, Christian A1 - Lörgen, Jürgen A1 - Graewe, Boris A1 - Bargon, Joachim A1 - Yoshida, Mayumi A1 - Freso, Zachary M. A1 - Frèchet, Jean M. J. T1 - High frequency quartz micro balances: a promising path to enhanced sensitivity of gravimetric sensors N2 - An array of 50 MHz quartz microbalances (QMBs) coated with a dendronized polymer was used to detect small amounts of volatile organic compounds (VOCs) in the gas phase. The results were compared to those obtained with the commonly used 10 MHz QMBs. The 50 MHz QMBs proved to be a powerful tool for the detection of VOCs in the gas phase; therefore, they represent a promising alternative to the much more delicate surface acoustic wave devices (SAWs). KW - Biosensor KW - Quartz micro balances KW - electronic noses dendronized polymers inverted mesa technology Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:a96-opus-1445 ER -