Sensor covers

Fig.4.14. Kinetics of variation of resistance of pure ZnO sensor and of ZnO sensor covered with a layer of H2O i,3 — interaction of H- and D-atoms with pure surface of ZnO 2,4 - interaction of H- and D- atoms with surface of ZnO covered with layer of H2O.

The IR detector utilizes a combination of three IR sensors of extremely narrow band response. One covers the typical CO2 emission spectral band, and the two other sensors cover different adjacent specially selected spectral bands. While the CO2 emission band sensor is responsible for the detection of... 

Someday we will have small portable devices that sample and analyze during exposure to the workplace atmosphere. Devices small enough to be worn comfortably by an active person, devices that will give warnings in real-time when danger of hazardous exposure occurs. These devices may be in the form of integrated circuits with sensors covered with permi-selective membranes, the combination of which will lead to both sensitive and selective measurements. Ten years from now current methods and devices may be, for the most part, but a memory. 

Fig. 20. The surface of a hydrophobic SPR-sensor (covered with long chain alkanethiols) was enlarged to an artificial membrane by application of lipid vesicles with a defined size distribution. Application of a Ras-lipopeptide construct with both a farnesyl- and a palmitoyl-modification leads to increase in resonance signal assumed to indicate membrane insertion (grey trace). Washing with buffer induces the slow decrease in signal. A Ras protein without hydrophobic modification (black trace) does not lead to signal increase...

Another urea electrode uses a carbon dioxide sensor covered with urease to measure the second product of the urea-urease reaction, HCOs. Na " and K" " had no influence on this electrode and the linear range was 0.1-10 mM (64). 

Gas pressures in vacuum applications are usually either recorded via membrane transducers, systems that monitor the gas density via partial ionisation of the gas or sensors that make use of the fact that the thermal conductivity or diffusivity of a gas is pressure dependent. The first type of transducer is sensitive to the total gas pressure while the other methods yield gas dependent signals. In terms of application properties such as the response time of the sensor, the sensitivity and the pressure range that the sensor covers are important technical specifications. The response of a membrane pressure sensor to a step-like pressure change is essentially an exponential function characterized by a relaxation time r for a MKS transducer, type Baratron 220 [1], r was determined to be 0.227 s (see Fig. 1), the actual pressure and the value as recorded by the transducer therefore do not match within the error bars given for the sensor until more than a second passed. 

RNPs, A02/7mC-Rev, A35/7mC-Rev, and A26/7mC-Rev, were spaced at approximately one order of magnitude intervals (Fig. 10.7b), with KD values being 2.2, 15.7, and 156 dM, respectively. A31/7mC-Rev appeared to show fluorescence response at the ATP concentration of l-10mM (Fig. 10.7a). Simultaneous application of these four sensors covers ATP concentration ranges from 10 7 to 10 2M. 

Another sensor type [158] utilizes the effect of water vapor on the fluorescence quantum yield of adsorbed fluorophores. Thus, a silica-gel-adsorbed perylene dy when excited with an LED at 490 nm, shows a ca 90 Fo reduction in fluorescence on going from 0 to 100% relative humidity. Although this sensor covers the whole humidity range, the response is not linear, and oxygen interferes to some atent. 

A needle-type glucose sensor covered by a biocompatible membrane has been described recently [47]. However, no in vivo results are reported. 

Figure 9.56. Scheme for the elaboration ofa sensor covered with a membrane... 

Tests carried out on a Sn02 sensor covered with a thin platinum film show that this material must be used in great quantities to be fully efficient on the catalytic plan. Beyond 10 nm, we notice noxious short-circuit effects at the level of the information capture. Below 10 nm, the catalytic performance ceases to be satisfying. 

The use of Sn02 sensors covered with a porous membrane has been studied by many researchers. 

Figure 9.61. Behavior of a sensor covered with a protective film as a function of time...

Figure 9. Microscopic photograph of a carbon fiber (a), Eiectron scanning micrograph (ESM) of the part of the sensor covered with a coat of isolating wax-rosin mixture (b), ESM of a thermally sharpened tip covered with polymeric TMHPPNi (c). (Reprinted with permission from Malinski T, Taha Z. Nature, 1992, 3S8 676)...

Fig. S Scanning electron micrograph of a thin film of polymeric (TMHPP)Ni (a) and the tip of a thermally pointed carbon fiber sensor covered with polymeric (TMHPP)Ni and Nafion...

Figure 11 Schematic illustration of the signaling mechanism of silica nanoparticle sensors covered with TSQ units. System in the absence (a) and presence (b) of Zn + at low zinc concentrations. ...

ISFETs Sensitive to Other Ions. Deposition of an ion-selective membrane on top of the gate insulator opens the way to measurement of ions other than H . Most of the sensitive materials for ISE applications described in Section 28,2.3.1,1 have been used in conjunction with ISFETs, providing sensors covering a wide variety of species. Thus, ISFETs with solid membranes have been described with AgCl-AgBr membranes sensitive to Ag . Cr, and Br [149], for example, or with LaFs membranes sensitive to fluoride [150], Ion-sensitive polymer-matrix membranes (liquid membranes with a polymer matrix) have also been used as sensitive membranes for ISFETs. The first experiments involved mainly PVC membranes [151]. [152], but these membranes show poor adhesion and poor mechanical strength. To improve membrane adhesion, modified PVC was utilized as a matrix material [153], The use of silicones as matrix materials has made it possible to prepare very durable ISFETs with polymer-matrix membranes [154], Other reports describe the use of photopolymerized polymers as matrix materials [155], [156],... 

To measure the particle pressure separately from the gas pressure, the chamber of the sensor covered by the diaphragm should have one or more bypass tubings to make the gas pressure inside equal to the outside, so... 

The detector has two EC sensors covered by a thin diffusion membrane. One sensor detects GA, GB, GD, AC, and CG, and the other detects H and L agents. 

The principal arrangement of the ferrocene-mediated needle-type glucose sensor is shown in Fig. 8, and the performance of the sensor is summarized in Table 3 compared with a poly(vinyl alcohol)(PVA) covered ferrocene-mediated sensor and a standard glucose sensor. The oxygen dependency was improved by the use of ferrocene as a mediator. There was not significant difference between the sensor covered with a poly(MPC-co-BMA) membrane and that with a PVA membrane in the absence of plasma proteins. In serum albumin solution(7 wt % in phosphate buffered solution, pH 7.4 at 37 C), though the output current of the ferrocene-mediated sensor with a PVA membrane decreased to 62% of the initial value after 14 days immersion, that observed on the sensor covered with a poly(MPC-cc -BMA) membrane remained above 92% of the initial value. 

Fig. 9 shows the time dependence of the relative sensor output and the relative response time of the ferrocene-mediated needle-type glucose sensor covered with a poly(MPC-c -BMA) membrane or a PVA membrane when the sensor was inserted continuously into the subcutaneous tissue of rats. By using the mediator, sensor... 

Table 3. Performance of conventional and ferrocene-mediated needle-type glucose sensors covered with various polymers in vitro...

Standard glucose sensor -----— covered with PVA membrane... 

Figure 9. Time course of relative output currents and response times of needle-type standard glucose sensor covered with PVA membrane and these of needle-type ferrocene-mediated glucose sensors covered with PVA membrane or poly(MPC-co-BMA) membrane when these sensors were inserted into subcutaneous tissue of normal rat.

Figure 10. Continuous monitoring of subcutaneous tissue glucose concentrations and blood glucose regulation in an insulin requiring NIDDM patient with a ferrocene-mediated needle-type glucose sensor covered with poly(MPC-co-BMA) membrane.

The term "ChG-based fiber optic sensor" covers a broad range of devices that work in many different ways. Beside chemical and biochemical species sensing, this technology has proven very efficient in the probing of physical parameters such as temperature, pressure, and mechanical deformation. 

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