Solid sensor materials

Square-planar ds platinum complexes could perhaps be used as the chemically sensitive layer for a chemical sensor system. These complexes are robust and form colored solid-state materials that respond spectroscopically to a wide range of volatile organic compounds (VOCs) this process has been named vapochromism. The vapochromic shifts occur in the solid-state UV-vis,... 

The combination of dyes with microporous materials opens-up a way to develop selective chemosensors microporous zeolites with an anchored squaraine 27 (Fig. 13) and some other types of dyes can be used as chemosensors for the chromogenic discrimination of amines [75], These dye-zeolite hosts are expected to be promising sensor materials allowing the visible discrimination of selected target guests by size and/or polarity within families or closely related molecules. It was found that the response of the solid to amines was basically governed by the three-dimensional architecture of the solid material. 

The choice of sensor material determines range, sensitivity, and stability. By considering the latter factors, it is found that inorganic insulating compounds, such as most lamp phosphors and many solid state laser materials, are the most suitable materials for thermometric applications. Indeed, these materials are most commonly used in the existing commercial fluorescence thermometer schemes. 

An excihng new scientific direction emerged in the 1980s and 1990s for exploring molecular sieves as advanced solid state materials. In a 1989 review, Ozin et al. [88] speculated that zeolites (molecular sieves) as microporous molecular electronic materials with nanometer dimension window, channel and cavity architecture represent a new fronher of solid state chemistry with great opportunihes for innovahve research and development . The applicahons described or envisioned included molecular electronics, quantum dots/chains, zeolite electrodes, batteries, non-linear ophcal materials and chemical sensors. More recently there have been significant research reports on the use of zeolites as low k dielectric materials for microprocessors [89]. 

Fraunhofer Institution for Modular Solid State Technologies EMFT, Workgroup Sensor Materials, Josef-Engert-Strasse 9, D-93053 Regensburg, Germany... 

This is a preliminary approach to the use of a new generation of solid-state sensors based on the capacity of the sensor element to catalyze the photodegradation of various kinds of organic compounds and to recognize their structure on the basis of the type of process catalyzed. The electron holes present in the Ti02 structure are able to promote the oxidative process of substances present in the environment, in particular the ones easily adsorbed on it. Titanium dioxide is a well-known photocatalyst [5-13]. Less famous are its characteristics as sensor material [14-18] of the ability of the organic molecules to be completely degraded, that is mineralized. 

Successful detection of S3P-labeled molecules separated by capillary electrophoresis using the above detection schemes, in which a sensor was positioned external to the separation channel, was made possible by several factors. These included (1) the large energy associated with 0 decay of S3P (1.7 MeV), (2) the high sensitivity and small size of commercially available semiconductor detectors, (3) the availability of efficient solid scintillator materials and sensitive photomultiplier tubes, (4) the short lengths of fused silica (capillary wall thickness) and aqueous electrolyte through which the radiation must pass before striking the detector, and (5) the relatively short half-life of S3P (14.3 days). 

Therefore, local dissolution and recrystallization seem to play an important role in the gas uptake mechanism in these type of sensor materials. The coordination of SO2 to the platinum center (and the reverse reaction) is therefore likely to take place in temporarily and very locally formed solutes in the crystalline material, whereas the overall material remains crystalline. The full reversibility of the solid-state reaction was, furthermore, demonstrated with time-resolved solid-state infrared spectroscopy (observation at the metal-bound SO2 vibration, vs= 1072 cm-1), even after several repeated cycles. Exposure of crystalline samples of 26 alternat-ingly to an atmosphere of SO2 and air did show no loss in signal intensities, e.g. due to the formation of amorphous powder. The release of SO2 from a crystal of 27 was also observed using optical cross-polarization microscopy. A colourless zone (indicative of 26) is growing from the periphery of the crystal whereas the orange colour (indicative for 27) in the core of the crystal diminishes (see Figure 9). 

Because all electrochemical devices such as batteries, fuel cells, sensors, and electrochromics require an electrolyte, the potential applications for ionic conductors are enormous. In addition to these more conventional applications, solid electrolyte materials are investigated for use as electrochemical memory devices, oxygen pumps, gas phase electrolyzers, and thermoelectric generators. ... 

Scheidtmann, J. Frantzen, A. Frenzer, G. Maier, W. F., A combinatorial technique for the search of solid state gas sensor materials, Meas. Sci. Technol. 2005, 16, 119-127... 

Potyrailo, R. A. Leach, A. M., Gas sensor materials based on semiconductor nanocrystal/ polymer composite films, In Proceedings of Transducers 05, the 13th International Conference on Solid-state Sensors, Actuators and Microsystems, Seoul, Korea, June 5-9, 2005 1292-1295... 

Today, principally new materials often require totally new methods and processes. Traditional sensor materials or improved versions of them usually simply require improved versions of traditional manufacturing processes to reach new levels of performance. Such improvements may be achieved in the sensor development process itself, or through development of special procedures for employing a traditional process. These facts are directly related to the development of solid electrolyte sensors in general and zirconia-based sensors measuring specific gaseous species in particular. 

Other potential applications of ordered mesoporous materials are in chromatographic applications and in the separation of molecules of biological interest, for which their uniform large pores can allow the development of new ways to products of high added value [ 103-105]. The field of sensors and solid-state materials are also promising [106-109]. 

Solid state materials that exhibit high ion transport properties are of interest from both academic as well as applied points of view. Polymer solid electrolytes are materials of high technological promise in several electrochemical applications such as high energy density batteries, gas sensors, electrochemical devices etc. These polymeric materials have attracted much attention and hold great promise in this area. 

In practice, sensors with oxoanionic solid electrolytes are less successful till now, especially in tests of long-term stability. There are many reasons for this, a fundamental reason is given by the electrode processes taking place during unevitable current flows. Every direct current causes on one side a loss of solid electrolyte material in consequence of alkali ion migration and gas delivery. On the other side the discharge of alkali ions causes chemical reactions with gas components forming compounds like oxides, hydroxides, basic salts or hydrates which do not correspond to the solid electrolyte material. Every flow of direct current produces an asymmetry in the body of the oxoanionic solid electrolyte. At the cathode, besides the reactions (25-66) and (25-67), simultaneously electrode reactions are possible, for example. 

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