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An amperometric electrode based on multiwall carbon nanotubes (MWCNTs) and Fe nanoparticles (NPs) has been successfully fabricated. The electrode combined with Flow Injection Analysis (FIA) exhibits linear response in the concentration range of 0.1–12 μM and the sensitivity of 30.0 nA μM −1 for most of amino acids, confirming good complexation of amino acids (AAs) with Fe NPs on the modified electrode. The determination of 17 amino acids in the hypothalamus microdialysis fluids of guinea pigs, illustrates that it is a powerful tool to investigate physiology and pathology mechanisms.

In this work, we report the development of a highly sensitive and stable choline/acetylcholine sensor based on the synergetic effect of multi-walled carbon nanotubes and ZnO nanoparticles. This unique multi-layer structure provided a favorable microenvironment to maintain the bioactivity of choline oxidase and acetylcholinesterase, which led to a rapid amperometric response to choline and acetylcholine. This nanomaterials-based choline/acetylcholine sensor was highly sensitive and showed good stability over a relatively long-term storage (90 days). The sensor prepared by loading 1.0-unit choline oxidase and acetylcholinesterase showed a linear response range of 1.0 μM to 0.8 mM and 1.0 μM to 1.0 mM, a sensitivity of 178 μA mM−1 cm−2 and 180 μA mM−1 cm−2, and a detection limit of 0.3 μM, respectively. The sensor prepared was used to detect choline in human blood plasma samples, and the obtained results were consistent with those of the HPLC–MS/MS assay.

In this work, we report the development of a highly sensitive and stable glucose sensor based on the synergetic effect of multi-walled carbon nanotubes (MWNTs) and ZnO nanoparticles. Since the isoelectric point (IEP) of glucose oxidase (GOx) is significantly different from that of ZnO nanoparticles, GOx was electrostatically bound to ZnO nanoparticles decorated onto a negatively charged MWNTs layer at the electrode surface via VLS growth. A cationic polydiallyldimethylammonium chloride (PDDA) layer was further coated onto the GOx-contained ZnO nanoparticle layer to prevent the leakage of GOx. This unique multi-layer structure (PDDA/GOx/ZnO/MWNTs) provided a favorable microenvironment to maintain the bioactivity of GOx, which led to rapid amperometric response toward glucose. By loading 0.5-U GOx at the sensor surface, we obtained a wide linear response range of 0.1-16mM for this sensor. High sensitivity of 50.2 mA cm(-2) M(-1) was obtained with increased loading of GOx (2.0U), leading to an even lower detection limit of 250 nM. This nanomaterials-based glucose sensor was highly sensitive and showed favorable stability over a relatively long-term storage (160 days). Importantly, we challenged our sensor with 100 human blood serum samples, and obtained consistent results with the classic spectrometric assay (correlation coefficient, 0.997). (c) 2009 Elsevier B.V. All rights reserved.

The paper describes fluidic networks consisting of individually controlled branches. The networks’ basic building blocks are conduits equipped with two electrodes positioned on opposing walls. The entire device is either subjected to an external uniform magnetic field or fabricated within a magnetic material. When a prescribed potential difference is applied across each electrode pair, it induces current in the liquid (assumed to be at least weakly conductive solution). Analogously with electric circuits, by judicious application of the potential differences at various branches, one can direct liquid flow in any desired way without a need for mechanical pumps or valves. Equipped with additional, internally located electrodes, the network branches double as stirrers capable of generating chaotic advection. The paper describes the basic building blocks for such a network, the operation of these branches as stirrers, a general linear graph-based theory for the analysis and optimal control of fluidic magneto-hydrodynamic (MHD) networks, an example of a network fabricated with low temperature, co-fired ceramic tapes, and preliminary experimental observations that illustrate that the ideas described in this paper can, indeed, be implemented in practice.

A micromachined 3×6 mm chip with a 3D silicon chamber (1.2×1.2 mm 2 and 300 μm thick)was developed for the construction of micro-size chemical sensors and biosensors. Anisotropic etching was used for the formation of the chamber on the p -type silicon wafer (100) and then was anodic bonded to the Pyrex glass down-substrate with pre-deposited platinum electrode. The electrochemical characterization of its Pt electrode and Ag/AgCl reference electrode is reported. It could be used as the substrate electrode for the sensing part of designed chemical sensors and biosensors with a protective and controlled environment. The preliminary application in the detection of H 2 O 2 , potassium ion and glucose is also reported. A cyclodextrin-ferrocene inclusion complex was prepared and used as the charge transfer mediator for glucose oxidase with promising results.

This paper describes the preparation of a TiO 2 -doped Nb 2 O 5 thin film using the ion-beam-enhanced deposition technique and the development of a new automobile air/fuel sensor with an additionally integrated platinum temperature sensor and a Pt heater. The resistive jump at the stoichiometric point in the characteristic curve is three orders of magnitude. The response time of the sensor is almost identical with that of the ZrO 2 oxygen sensor. The performance of the sensor becomes stable after seven measurement periods. Preliminary results indicate that this sensor exhibits attractive performance and the potential to monitor the λ-value for automobile exhaust gas.

A high-response glucose has recently been developed by modifying an immobilized GOD (glucose oxidase) membrane and coating Nafion diffusion-limiting membrane over an amperometric H 2 O 2 MAE (microarray electrode), which is fabricated by using standard planar processing. The chip of the sensor is 2.5 mm by 15 mm. The MAE is composed of an Ag/AgCl RE (refence electrode), at Pt CE (counter electrode) and two sets of Pt WEs (working electrodes), each set consisting of five bands. Silicon nitride is chosen as the top insulator. Six MAEs different in both width and length of the band are examined and the MAE with the narrowest bandwidth (10 μm) exhibits the best electrochemical performance. The glucose sensor based on the MAE B1–2 presents a linear range of 0.5–40 mM glucose at 37 °C with a sol1 5 M phosphate buffer solution (pH=7.0) as supporting electrolyte. The sensitivity, background current, response time, coefficient of variation and long-term stability of the sensor are 7.1±0.5 nA/mM, 2±0.5 nA, 30 s, 3.4% and 6 days (or 250 assays), respectively.