All rights reserved (including those of translation in other languages). No part of this book may be reproduced in any form -by photoprinting, microfilm, or any other means -nor transmitted or translated into machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law. PrefaceChemical sensors are intended to solve analytical problems complementary to that provided by standard analytical instruments. In order to become commercially viable, chemical sensors have to be combined with an appropriate sampling device and electronics in such a way that the overall dimensions of the final device, the price and ease in handling, are acceptable. These parameters determine the profile of sensing devices in the vast range of applications in industrial and bio-process control, in environmental monitoring and in monitoring of toxic effluents (e.g. cyanide), in food technology, in field measurements, in emergency-care analysis, and point-ofcare testing (POCT) in medicine. An unexplored area is the use of chemical sensors in toxicology. In order to cope with various fields of applications, the brand "the Lab in the Bag" was coined specifying the trend of further developments.Several comprehensive volumes on chemical sensors had been published. However most of them are more focused on the development of the physical part, the transducers. This volume intends to provide an overview on the variety of chemical sensors focusing on analyticalchemical aspects generally, and on biological applications specifically. The field of chemical sensors could be depicted as a space which is spread by 3 coordinates: the biological or life sciences along one axis, physical-chemistry and chemistry along another, and mathematics and statistics along the third axis. This %pace'' reflects the complexity of the field. This volume tries to take sufficient account of each axis and gives an overview of the field with special focus on the developments in the goup of Prof. W. Simon, Laboratory for Organic Chemistry, involving the habilitation thesis of the author, and on developments in the Centre for Chemical Sensors/Biosensors and bioAnalytical Chemistry at ETH Ziirich-Technopark. Each chapter is devoted to a separate theme. So the references have been inserted after each thematic block or chapter, beginning with chapter 1. Each thematic block or section is closed by conclusions.In the first chapter, the question as to whether chemical sensors and biosensors have to be differenciated is discussed. In the course of this chapter, chemical sensors are defined and related to particular areas in analytical chemistry. A brief history of the field is given describing the development of chemical sensors. This is followed by a discussion of market trends and comments on possible future developments of the general situation in analytical laboratories.The second and third chapter sets out to give an overview on the chemic...

A new class of dyes has been investigated that reversibly interacts with aliphatic amines, resulting in changes in absorbance or fluorescence. These dyes, which combine the properties of both a chemical reagent and a ligand, are termed "reactands". When embedded in plasticized PVC membranes, the reactand 4-(N,N-dioctylamino)-4′trifluoroacetylazobenzene (ETH T 4001) shows a significant signal change on exposure to aqueous amine solutions, with a decrease in absorbance around 490 nm and an increase in absorbance around 420 nm wavelength. This change in absorbance is caused by a conversion of the trifluoroacetyl group of the reactand into a hemiaminal or a zwitterion. Upon interaction with 1-butylamine, the sensor layer exhibits a dynamic range from 1 to 100 mM 1-butylamine, with maximum relative signal changes of 90%. The limit of detection with this approach is 0.3 mM. The forward response time (t 95 ) for a decade change in activity is 10 min, and the reverse response time is 5 min. The selectivity of ETH T 4001 toward amines correlates with the lipophilicity of the amines in plasticized PVC. Sterical factors additionally affect selectivity in that the reactions of secondary, tertiary, and bulky primary amines with the trifluoroacetyl group are hindered. A similar response is observed for the fluorescent reactand 4-(N,Ndioctylamino)-4′-trifluoroacetylstilbene (ETH T 4004). When this reactand is exposed to 1-butylamine, a decrease in fluorescence around 580 nm is observed, which can be as high as 90% of the total fluorescence intensity. To prevent interferences from ions and ambient light, the sensor layer is coated with a protective layer of microporous white PTFE.

No abstract

In this study, a novel phosphorescent Ir(III) complex [Ir(2-phenylpyridine)2(4,4'-bis(2-(4-N,N-methylhexylaminophenyl)ethyl)-2-2'-bipyridine)Cl] (for convenience, the complex was given the synonym N-948) has been designed and synthesized, to be used as an oxygen probe. It was characterized by spectroscopic and analytical methods when incorporated in a polystyrene and nanostructured metal oxide support. N-948 is the first Ir complex in the literature with a luminescence emission at a wavelength higher than 650 nm (665 nm), with a quantum yield higher than 0.50 (0.58 +/- 0.05) and an extremely long phosphorescence lifetime (102 micros) which has been used for developing oxygen-sensitive films. In addition, the new complex shows a Stern-Volmer constant which is 20 times higher than that of other Ir complexes known from the literature when they are immobilized in polystyrene. The sensing film shows long-term stability (up to 12 months), complete reversibility of the signal quenched by oxygen and a quick response time to various oxygen concentrations (<2 s changing from 10 vol% pO2 to 90 vol% pO2). Thus, it is an interesting and promising complex for developing oxygen-selective sensors for gas analysis and the analysis of dissolved oxygen.

No abstract

An iron(II) phthalocyanine (FePc) complex solubilized by decylamine (DA) and benzylamine (BA) is incorporated into a nanoparticulate metal oxide matrix to develop optical sensor films sensitive to NO2 and CO. Eleven amine solvents have been tested as N‐donor ligands that permit ligand exchange with the gas molecules. We have systematically investigated the suitability of different N‐donor ligands, studied the thermal stability of the NO2‐ and CO‐sensing films at 4, 25, 60, and 80 °C by photometry, and corroborated our findings by using NMR experiments. A satisfactory thermal stability of the films has not been obtained for chemically unmodified nanoparticulate metal oxide matrices. We have therefore developed a second generation of nanostructured metal oxide supports that show increased thermal stability and adequate sensitivity to NO2 and CO. These novel nanostructured matrices have been chemically modified using amines, alumina oligomers, and/or anti‐gas‐fading agents. These components have been integrated into the metal oxide matrices to avoid degradation of the optical films and to preserve their sensitivity.

No abstract

A new class of fluorogenic copolymers has been synthesized that reversibly interacts with dissolved aliphatic amines resulting in a change in fluorescence. The copolymers are composed of different methacrylate monomeric units, such as hexyl methacrylate and the dye monomer 4-[N,N-bis(11-methacroyloxyundecyl)amino]-4‘-trifluoroacetylstilbene (ETHT 4014). Upon exposure to aqueous amine solutions, thin layers of the copolymers show a decrease in fluorescence at a wavelength around 520 nm and an increase in fluorescence at around 420 nm. The change in fluorescence is based on the nucleophilic addition of amines to the trifluoroacetyl group of the reactand, thus causing a change in the degree of electron delocalization. Since the sensor layers are composed of copolymerized components, they exhibit superior operational stability to sensors based on plasticized PVC, and their lack of plasticizers enhances the shelf lifetime.