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Fast Response Time (fast + response_time)
Selected AbstractsThe NADH Electrochemical Detection Performed at Carbon Nanofibers Modified Glassy Carbon ElectrodeELECTROANALYSIS, Issue 14 2007Adina Arvinte Abstract In this work, the capability of carbon nanofibers to be used for the design of catalytic electrochemical biosensors is demonstrated. The direct electrochemistry of NADH was studied at a glassy carbon electrode modified using carbon nanofibers. A decrease of the oxidation potential of NADH by more than 300,mV is observed in the case of the assembled carbon nanofiber-glassy carbon electrode comparing with a bare glassy carbon electrode. The carbon nanofiber-modified electrode exhibited a wide linear response range of 3×10,5 to 2.1×10,3,mol L,1 with a correlation coefficient of 0.997 for the detection of NADH, a high specific sensitivity of 3637.65 (,A/M cm2), a low detection of limit (LOD=3,) of 11,,M, and a fast response time (3,s). These results have confirmed the fact that the carbon nanofibers represent a promising material to assemble electrochemical sensors and biosensors. [source] Glucose Biosensor Mediated by 1,2-Diferrocenylethane in a Sono-Gel Composite ElectrodeELECTROANALYSIS, Issue 2-3 2007Barbara Ballarin Abstract An amperometric glucose biosensor was constructed based on a renewable carbon composite sono-gel matrix incorporating 1,2-diferrocenylethane as electron transfer mediator between the electrode and the active site of glucose oxidase. The enzyme was immobilized on the electrode surface by cross-linking with glutaraldehyde and bovine serum albumin. The process parameters for the fabrication of the biosensor and the influence of various experimental conditions (i.e., pH, temperature, operating potential) were investigated. Cyclic voltammetry and amperometric measurements were used to study the response of the glucose sensor, which displayed fast response time and good reproducibility. The analytical performances and the apparent Michaelis-Menten constant of the biosensor were evaluated. [source] Silver(I)-Selective PVC Membrane Potentiometric Sensor Based on a Recently Synthesized Calix[4]areneELECTROANALYSIS, Issue 10 2006Ayça Demirel Abstract A new PVC membrane potentiometric sensor for Ag(I) ion based on a recently synthesized calix[4]arene compound of 5,11,17,23-tetra- tert -butyl-25,27-dihydroxy-calix[4]arene-thiacrown-4 is developed. The electrode exhibits a Nernstian response for Ag(I) ions over a wide concentration range (1.0×10,2,1.0×10,6 M) with a slope of 53.8±1.6,mV per decade. It has a relatively fast response time (5,10,s) and can be used for at least 2 months without any considerable divergence in potentials. The proposed electrode shows high selectivity towards Ag+ ions over Pb2+, Cd2+, Co2+, Zn2+, Cu2+, Ni2+, Sr2+, Mg2+, Ca2+, Li+, K+, Na+, NH4+ ions and can be used in a pH range of 2,6. Only interference of Hg2+ is found. It is successfully used as an indicator electrode in potentiometric titration of a mixture of chloride, bromide and iodide ions. [source] Iodide-Selective Electrode Based on Copper PhthalocyanineELECTROANALYSIS, Issue 23 2002Saeed Shahrokhian Abstract Copper phthalocyanine was used as ion carrier for preparing polymeric membrane selective sensor for detection of iodide. The electrode was prepared by incorporating the ionophore into plasticized poly(vinyl chloride) (PVC) membrane, coated on the surface of graphite electrode. This novel electrode shows high selectivity for iodide with respect to many common inorganic and organic anions. The effects of membrane composition, pH and the influence of lipophilic cationic and anionic additives and also nature of plasticizer on the response characteristics of the electrode were investigated. A calibration plot with near-Nernestian slope for iodide was observed over a wide linear range of five decades of concentration (5×10,6,1×10,1,M). The electrode has a fast response time, and micro-molar detection limit (ca. 1×10,6,M iodide) and could be used over a wide pH range of 3.0,8.0. Application of the electrode to the potentiometric titration of iodide ion with silver nitrate is reported. This sensor is used for determination of the minute amounts of iodide in lake water samples. [source] Single-Crystalline ZnS Nanobelts as Ultraviolet-Light SensorsADVANCED MATERIALS, Issue 20 2009Xiaosheng Fang Single-crystalline ZnS nanobelts with sharp ultraviolet-light emission (,337,nm) at room temperature have been assembled as UV Sensors. The high spectral selectivity, combined with high photosensitivity and fast response time, justifies the effective utilization of the present ZnS nanobelts as "visible-light-blind" UV photodetectors in different areas. [source] Hopfield neural-network-based dynamic resource allocation scheme for non-real-time traffic in wireless networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2009José F. Monserrat Abstract Dynamic resource allocation (DRA) plays a fundamental role in current and future wireless networks, including 3G systems. In this paper, a scheduling DRA scheme for non-real-time (NRT) packet services in wireless system is proposed based on the use of Hopfield neural networks (HNN). The scheme exploits the fast response time of HNN for solving NP optimization problems and has been particularized for the downlink transmission in a UMTS system, although it could be easily extended to any other radio access technology. The new DRA scheme follows a delay-centric approach, since it maximizes the overall system resource utilization while minimizing the packet delay. Simulation results confirm that the proposed HNN-based DRA scheme is effective in supporting different types of NRT services, while achieving efficient utilization of radio resources. Copyright © 2008 John Wiley & Sons, Ltd. [source] Highly Sensitive Thin Film Sensor Based on Worm-like Carbon Nanofibers for Detection of Ammonia in WorkplaceCHINESE JOURNAL OF CHEMISTRY, Issue 4 2008Jia-Zhi WANG Abstract A thin film sensor was fabricated using the mixture of worm-like carbon nanofibers (WCNF), which were synthesized using aluminium supported iron catalysts via chemical vapour deposition, and glass dust in proportion of 3:2, combined by drops of terpineol. The morphology of the catalyst, the worm-like carbon nanofibers and the film surface were investigated with the help of TEM and SEM. Low single-potential signal was employed to investigate gas sensitivity of the sensor to the deleterious ammonia, in atmospheric pressure at room temperature. The results suggest that the sensor has high sensitivity at low concentration (0.175,0.35 mg/m3), perfect reproducibility, and a fast response time (0.05 s) and restoration time (1 min). [source] Toxicity Assessment of Cyanide and Tetramethylene Disulfotetramine (Tetramine) Using Luminescent Bacteria Vibrio-qinghaiensis and PbO2 Electrochemical SensorCHINESE JOURNAL OF CHEMISTRY, Issue 2 2007Wei Liu Abstract The toxicities of cyanide and tetramethylene disulfotetramine (tetramine) were evaluated by two methods of luminescent bacteria and PbO2 electrochemical sensor. Vibrio-qinghaiensis, a kind of luminescent bacteria, can produce bioluminescence and the bioluminescence was decreased with the addition of toxicants. The toxicities of cyanide and tetramine were expressed as 10 min-EC50 value, which was the concentration of chemical that reduces the light output by 50% after contact for 10 min. Nano PbO2 modified electrode, a rapid toxicity determination method was also described in this work. By the PbO2 modified electrode, the current responses of Escherichia coli (E. coli) were changed with the addition of toxicants. The value of 10 min-EC50 was also provided with the PbO2 electrochemical sensor. Compared with the 10 min-EC50 and detection limits (38.38 and 0.60 µg/mL for cyanide, 0.24 and 0.02 µg/mL for tetramine) with luminescent bacteria, the PbO2 sensor provided a simple and convenient method with lower 10 min-EC50 and detection limits (26.37 and 0.52 µg/mL for cyanide, 0.21 and 0.01 µg/mL for tetramine) and fast response time. [source] A Highly Selective FRET-Based Fluorescent Probe for Detection of Cysteine and HomocysteineCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2010Hoi-Yan Shiu Fluorescent probe: A "turn-on" FRET-based fluorescent probe for selective detection of cysteine (Cys) and homocysteine (Hcy) under physiological conditions was synthesised (see figure). The probe features excellent selectivity, fast response times and good linearity towards Cys and Hcy detection. [source] | ||||||||||