Cadmium sensor

Bronson RT, Michaelis DJ, Lamb RD et al (2005) Efficient immobilization of a cadmium chromosensor in a thin film feneration of a cadmium sensor prototype. Org Lett 7 1105-1108... 

Solid-state cadmium sensors based on chalcogenide thin film layer were prepared [388]. The electrochemical behavior of the sensor in terms of ionic sensitivity, detection Emit, Nernstian response interval and effect of pH was evaluated. 

J.P. Kloock, L. Moreno, A. Bratov, S. Huachupoma, J. Xu, T. Wagner, T. Yoshinobu, Y. Ermolenko, Y.G. Vlasov and M.J. Schoning, PLD-pre-pared cadmium sensors based on chalcogenide glasses—ISFET, LAPS and pISE semiconductor structures, Sens. Actuators B Chem., 118 (2006) 149-155. 

Table 1 Binding affinities, fluorescence wavelengths, and biological applications of fluorescent cadmium sensors. 

A unique but widely studied polymeric LB system are the polyglutamates or hairy rod polymers. These polymers have a hydrophilic rod of helical polyglutamate with hydrophobic alkyl side chains. Their rigidity and amphiphilic-ity imparts order (lyotropic and thermotropic) in LB films and they take on a F-type stmcture such as that illustrated in Fig. XV-16 [182]. These LB films are useful for waveguides, photoresists, and chemical sensors. LB films of these polymers are very thermally stable, as was indicated by the lack of interdiffusion up to 414 K shown by neutron reflectivity of alternating hydrogenated and deuterated layers [183]. AFM measurements have shown that these films take on different stmctures if directly deposited onto silicon or onto LB films of cadmium arachidate [184]. 

Cadmium Telluride. Cadmium teUuride [1306-25-8] CdTe, is another promising thin film. CdTe is a well-known semiconductor often used in high performance infrared sensors. CdTe absorbs visible light very strongly, and very thin films (1—2 llm) are sufficient to absorb most sunlight. 

Apart from transistor-like devices, single-electron junctions can also be useful for sensor applications. The simplest one might be the monitoring of H2S. Since the formation of CdS nanogranules takes place when an initial cadmium arachidate layer is exposed to this gas, we can expect the appearance of single-electron conductivity only when it is present in the atmosphere. 

Zhujun Z., Seitz W.R., A fluorescent sensor for aluminum(III), magnesium(II), zinc(II) and cadmium(II) based on electrostatically immobilized quinolin-8-ol sulfonate. Anal. 

Nickel AML, Seker E, Ziemer BP, Ellis AB. Imprinted poly (acrylic acid) films on cadmium selenide. A composite sensor structure that couples selective amine binding with semiconductor substrate photoluminescence. Chem Mater 2001 13 1391-1397. 

Crown ethers [364] have proved to be an excellent choice as ionophores for the fabrication of ion sensors because of their ability to complex selectively a particular ion. The cadmium selective sensors have been fabricated from poly(vinyl chloride) (PVC) matrix membranes containing macrocyclic ionophores benzo-15-crown-5 [365], monoaza-18-crown-6 [366], dibenzo-24-crown-8 [367], dicyclohexano-18-crown-6 [368], 3,4 ll,12-dibenzo-l,6,... 

The electrochemical flow sensor for in situ monitoring of total cadmium concentration in the presence of EDTA and nitrilotriacetic acid (NTA) ligands has been described [379]. 

A number of Cd(II) sensors based mainly on the Ag2S/CdS mixtures [384, 385] and cadmium chelates [386] were described. Ito etal. [387] used an Ag2S/CdS ion-selective electrode for determination of cadmium ion in industrial wastewater by titration method. 

Chow et al. have described [407] the electrochemical sensor for cadmium ions with gold electrode modified by 3-mercap-topropionic acid followed by covalently coupling the cadmium selective hexapep-tide His-Ser-Gln-Lys-Val-Phe. 

The electrodes modified by hexacyano-ferrates compounds were also used as voltammetric sensors [409-412]. The cadmium hexacyanoferrate-based composite ion-sensitive electrode for voltammetry was explored by Scholz and coworkers [409]. The potential of such electrode depends linearly on the logarithm of concentration of alkali and alkaline-earth metals ions in the solutions. Bo and fin have studied [410] Prussian blue (PB)/Pt modified electrode in GdGh electrolyte by cyclic voltammetry and in situ Fourier transform IR spectroscopy (FTIR) spectro-electrochemistry. Cadmium hexacyanofer-rates were formed on a PB film. 

Moreover, the use of resistant strains is of interest. Slama et al. [21] described a heavy metal resistant BOD-sensor using Alcaligenes eufrop/jus, which contains plasmids encoding resistance to nickel, copper, cadmium, and zinc. An arsenic resistant BOD-sensor based on Pseudomonas putida was developed by Ohki et al. [35]. Another interesting possibility is the elimination of heavy metals by covering the BOD-sensor with a poly(4-vinylpyridine)-coated polycarbonate membrane [36] or polyfsodium styrene sulfonate) [62]. 

Tauriainen S, Karp M, Chang W, Virta M (1998) Luminescent bacterial sensor for cadmium and lead. Biosens Bioelectron 13 931-938... 

Cd2+ and the Pb2+ and all electrodes display the two peaks but to different extents. Despite the peak overlap, the electrode array can be calibrated for each metal ion using a three-way partial least squares regression (AT-PLS) [53]. The electrode array was employed to analyse three test samples of known concentration of Cu2+, Cd2+ and Pb2+ and the concentrations of each analyte predicted by the calibrated electrode array are shown in Table 10.1. As can be seen from Table 10.1 there is reasonable agreement between the actual and predicted values despite the fact that all electrodes respond to all analytes and that the electrochemical responses to lead and cadmium overlap. Further improvements would be expected if the calibrations were performed with a box experimental design, which encompassed the linear range of all the sensors. 

Determination of cadmium concentration and pH value in aqueous solutions by means of a handheld light-addressable potentiometric sensor (LAPS) device... 

The objective of this protocol is the fabrication of a light-addressable potentiometric sensor (LAPS) for the detection of the pH value and the cadmium-ion concentration in aqueous solutions. For the pH-sensitive LAPS, use, e.g., Ta205 as a sensor membrane, and for the cadmium-selective LAPS, use a Cd2+-selective chalcogenide glass thin film as a heavy metal-sensitive material. The electrochemical sensor characterisation of the LAPS structure perform current vs. voltage (I/V) and constant current (CC) measurements. 

Figure 6.4a shows typical CC-mode data of the measurement procedure. For a constant pH value at pH 3, only a small deviation is observable, due to slightly different pH adjustments, when using different Cd2+-ion concentrations. The calibration plots in Fig. 6.4b clarify, therefore, a good sensitivity towards Cd2+ in the cadmium-sensitive part of the LAPS with a slope, in this example, of about 27 mV/decade, whereas the pH-sensitive area of the LAPS is not influenced by the different Cd2+-ion concentrations. For more details concerning the pH-and cadmium-sensitive behaviour of the LAPS sensor, see elsewhere [10-12],... 

The combination of different fluorescent metal indicators with inert luminescent reference beads consisting of poly(acrylonitrile) containing Ru(dpp)3 leads to a sensor array in a microwell plate format, suited for ratiomet-ric time-resolved imaging [95]. The data can be acquired with the help of the f-DLR method (for details see Sect. 2.3). A cross-reactive sensor array was arranged for the determination of mixtures of calcium(II), copper(II), nickel(II), cadmium(II), and zinc(II) ions by nine different commercially available fluorescent indicators (Table 3). For a successful application, it is mandatory that all luminophores can be excited at the same wavelength range between 400 and 500 nm, and that the excitation and emission spectra of all indicators overlap with those of the reference dye encapsulated in the nanobeads. 

A charge transfer device infrared sensor matrix 22 comprises CCD elements 24 arranged in rows and columns. Each element 24 is formed on a mercury cadmium telluride substrate. The electrodes of the CCD elements are connected by metallized bus lines 44 to a four phase... 

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