Sensors, copper ions

Nafion is thought to form dimers giving rise to a biexponential decay. 44,46) Using diode laser excitation at 670 nm, the fluorescence of oxazine in Nafion and its quenching by copper ions has been shown to give rise to a complex fluorescence decay.(47) Despite such complications there is still room for optimism. For example, Zen and Patonay(48) have demonstrated a pH sensor based on cyanine dye fluorescence intensity in Nafion excited with 30 mW diode laser excitation at 780 nm. 

Lehmann M, Riedel K, Adler K, Kunze G (2000) Amperometric measiuement of copper ions with a deputy substrate using a novel Saccharomyces cerevisiae sensor. Biosens Bioelectron 15 211-219... 

It is well known that copper ion (Cu +) is able to quench Eu(III) emission. Recently, the Eu(III)-cyclen-p/ien conjugate Eu-1 (Eigure 13.5) has been reported as a luminescent copper sensor. The addition of Cu + to the solution of Eu-1 at pH 7.4 induced the quenching of Eu(III) luminescence at 615nm [36]. 

Suitably modified fiber optic sensors can also be used for detecting gas vapors, humidity, ions, and organic compounds. Fiber inclusions that show length variation were used to develop humidity sensors, whereas ion-responsive lipid bilayers formed the basis for the detection of inorganic ions. Immobilized neutral and ionic crown ethers in polymeric membranes were designed as sensors for determination of barium and copper (Wolfbeis 2000). 

As mentioned above, type II sensors have the advantage of accumulating the signal. In return, however, these sensors do not respond easily to dynamic changes in analyte concentration over time. The number of examples is to date fairly limited but useful sensors for copper ions [6], phosphor organics [7],... 

One of the typical chemical characteristics of metal ions and/or their complexes is their ability to bind specifically and reversibly with small molecules, such as alkene, carbon monoxide, molecular nitrogen, and moleeular oxygen [1-3]. For instance, ethylene coordinatively binds with silver or copper ions, and molecular oxygen with metalloporphyrins. When such metal ions or metalloporphyrins are molecularly bound in macromolecules to form metal complexes, the reversible binding of small molecules with the metal complexes in macromolecules offers extensive potential applications, such as separation membranes, absorbents, and sensors. 

There are a number of uses for chiral metallic nanoparticles. One such application for chiral nanoparticles are as chiral sensors. This is considered feasible as it has been already demonstrated that uncoated gold nanoparticles can show selective aggregation in the presence of D-tryptophan and copper ions while none in the presence of L-tryptophan and other aminoacids. ° Similar work was conducted for diols (Fig. 5) using functionalised gold nanoparticles and for the chiral dicationic helicene, helquat. ... 

The luminescence intensity and decay time of EuCls in carboxymethyl cellulose membranes is decreased in presence of heavy metal ions like Cu" or Cu ", but also Cr " and Fe " exert a distinct quenching effect [111]. It is not likely that a sensor with high specificity can be prepared on the basis of LLCs that is free of interferences from other metal ions. However, an adequate choice of the ligand system may help to improve the selectivity of the response. Another approach uses a sol-gel technique to embed a complex of Eu " and silanized 2,6-pyridine-dicarboxylic acid as antenna in a silica network. This luminescent material can sense copper ion concentrations in water down to 50 pg but the sensor was not evaluated with respect to interferences of other metal ions or in environmental samples [112]. 

An imidazole-functionalized disubstituted acetylene polymer (42 in Figure 15) has been synthesized via a postfrmc-tional strategy and evaluated as sensor for copper ions and a-amino acids by fluorescence quenching. Fluorescence quenching is observed at low Cu (7.0 x 10" M" ) concentration. The fluorescence intensity sharply decreases with an increase in Cu concentration. The addition of a-amino acids to the solution of 42/Cu complex enhances the fluorescence of 42, presumably due to the removal of copper ions from the complex by a-amino acids. Upon addition of glycine, the quenched fluorescence turns on immediately. The detection limit is as low as 6.0 x 10" M . ... 

Gao, L. Lue, K Xia, H. Ding, L. Fang, Y. Fluorescent film sensor for copper ion based on an assembled monolayer of pyrene moieties. Spectrochim. Acta, Part A 2011, 79,437-442. 

Non-stoichiometric Zn/Cr and Cu/Cr mixed oxides are one of the principal examples of these unusual solids. They have applications as both solid state gas sensors (5) and catalysts for hydrogenation reactions (of CO to methanol and/or methanol-higher alcohol mixtures, and of many organic molecules) (6-12). These systems have been widely investigated over the last few years, and results obtained show that their peculiar catalytic properties may be associated with the presence of non-stoichiometric phases (with a M /M ratio higher than 0.5, M= metal), in which some of the zinc or copper ions are present in octahedral positions, i.e., with an unusual coordination. However, until now very few data have been reported regarding the changes in structure and reactivity as a function of the composition in ternary systems (for instance Cu/Zn/Cr). 

Qin, W., Zhang, Z., and Liu, H., Chemiluminescence flow-through sensor for copper based on anodic stripping voltammetric flow cell and ion-exchange column with immobilized reagents., Anal. Chem., 70, 3579, 1998. 

Chemical structure of the Zincon- Response of a Zincon-based sensor membrane tetraoctylammonium ion pair to different pM concentrations of copper(II) at... 

When the Zincon ion-pair is exposed to an aqueous sample containing the analyte, the latter diffuses into the sensor membrane to react with the indicator, and gives a colour transition from pink to blue at near neutral pH. The pKa value of Zincon for the color transition from pink to blue is above 13, therefore, the sensor membrane is virtually insensitive to pH changes. However, due to the high complexation constant of Zincon for copper and zinc, the response of sensor membrane is irreversible and must be evaluated kinetically12. 

T. Mayr, I. Klimant, O.S. Wolfbeis and T. Werner, Dual lifetime referenced optical sensor membrane for the determination of copper(II) ions, Anal. Chim. Acta, 462(1) (2002) 1-10. 

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