Solid state potentiometric sensors

Poor adhesion of membrane to metal is the leading cause of failure in solid-state potentiometric sensors [116], For glass membranes, the mismatch of thermal coefficients of expansion between thin glass membrane and metal (mostly Pt) has been attributed to premature failure due to hairline crack formations in the glass layer [60], For polymer-based membranes, water vapor penetration was reported to compromise the membrane-metal interface, therefore affecting the sensor s performance. 

Another type of sensor is a high-temperature solid-state potentiometric sensor for oxygen (>400°C) in industrial processes. These are based on the measurement of the potential of a concentration cell of the type... 

According to previous applications to solid state potentiometric sensors, PEVD seems to be a possible technique to deposit in-situ a layer of an oxygen ion conducting phase on a metallic anode of an SOFC. Thus, a composite anode with both a PEVD product and a metallic anode could be realized to overcome the aforementioned anodic limitations. 

Michalska, A., A. Hulanicki, and A. Lewenstam. 1997. All-solid-state potentiometric sensors for potassium and sodium based on poly(pyrrole) solid contact. Microchem J 57 59. 

Alberti G, Carbone A, Palombari R (2001) Solid state potentiometric sensor at medium temperatures (150-300 °C) for detecting oxidable gaseous species in air. Sens Actuators B 75 125-128 Ando M, Kobayashi T, Haruta M (1996) Humidity-sensitive optical absorption of Co O film. Sens Actuators B 32 157-160... 

Macagnano A, Zampetti E, Pantalei S, De Cesare F, Bearzotti A, Persaud KC (2011) Nanofibrous PANI-based conductive polymers for trace gas analysis. Thin Solid Films 520 978-985 MacDiarmid AG (2002) Synthetic metals a novel role for organic polymers. Synth Met 125 11-22 Maffei N, Kuriakose AK (2004) A solid-state potentiometric sensor for hydrogen detection in air. Sens Actuators B 98 73-76... 

Reference Electrodes in Solid-State Potentiometric Sensors and Appliances for Thermodynamic Measurements... 

The operation of potentiometric sensors is based on the measurements of concentration cell emf (see Chaps. 1 and 8), which makes it possible to extract the activity, concentration, or partial pressure of potential-determining species at the working electrode vs. RE. The WE potential may be established by a thermodynamic equilibrium or by a nonequdihrium steady state, whereas key requirements to the reference electrodes are related to their reversibility, stability, and, often, fast equilihratirMi on changing external conditions. The solid-state potentiometric sensors are used for a wide variety of technological applicatirms and probed species [2,3,5,15,18,86-91] their application for oxidic glass melts is addressed in Chap. 8. 

Solid-state potentiometric sensors that are based on the chemical modulation of the work function of organic semiconductors were reviewed. These include the chemically sensitive field-effect transistor in which the conventional gate of... 

Metal/metal oxides are the materials of choice for construction of all-solid-state pH microelectrodes. A further understanding of pH sensing mechanisms for metal/metal oxide electrodes will have a significant impact on sensor development. This will help in understanding which factors control Nemstian responses and how to reduce interference of the potentiometric detection of pH by redox reactions at the metal-metal oxide interface. While glass pH electrodes will remain as a gold standard for many applications, all-solid-state pH sensors, especially those that are metal/metal oxide-based microelectrodes, will continue to make potentiometric in-vivo pH determination an attractive analytical method in the future. 

J.E. Zachara, R. Toczylowska, R. Pokrop, M. Zagorska, A. Dybko, and W. Wroblewski, Miniaturised all-solid-state potentiometric ion sensors based on PVC-membranes containing conducting polymers. Sens. Actuators B. 101, 207-212 (2004). 

J. Bobacka. T. Lindfors, A. Lewenstam. and A. Ivaska, All-Solid-State Ion Sensors Using Conducting Polymers as Ion-to-Electron Transducers, Am. Lab., February 2004, 13 A. Konopka, T. Sokalski, A. Michalska, A. Lewenstam, and M. Maj-Zurawska, Factors Affecting the Potentiometric Response of All-Solid-State Solvent Polymeric Membrane Calcium-Selective Electrode for Low-Level Measurement, Anal. Chem. 2004, 76, 6410 M. Fouskaki and... 

It is typically on the order of several hundred nanometers. In practice the minimum thickness for polymeric membranes is 50gm or greater, which is far more than one would expect from (6.53). This is apparendy due to the fact that these membranes hydrate in the bulk, thus increasing the dielectric constant. They also form a hydrated layer at the solution/membrane interface (Li et al 1996) which affects their overall electrochemical properties and selectivities. Macroscopic ISEs use relatively thick membranes ( 500jU.m). In contrast, it is desirable to use thin membranes in the construction of asymmetric solid-state potentiometric ion sensors, in order to make their preparation compatible with the thin-layer preparation techniques. 

Table 6.7 Potentiometric solid-state gas sensors (adapted from Fouletier, 1982)... 

In order to fully utilize solid-state ion sensors in potentiometric measurements there is a need for a durable and reliable solid-state reference electrode as well. It was shown recently that it is possible to construct... 

Conducting polymers have been studied as potentiometric ion sensors for almost two decades and new sensors are continuously developed. The analytical performance of solid-state ion sensors with conducting polymers as ion-to-electron transducer (solid-contact ISEs) has been significantly improved over the last few years. Of particular interest is the large improvement of the detection limit of such solid-contact ISEs down to the nanomolar level. Further optimization of the solid contacts as well as the ion-selective membranes will most certainly extend the range of practical applications. 

Pasierb, P., and Rekas, M. 2009. Solid-state potentiometric gas sensors-current status and future trends. Journal of Solid State Electrochemistry 13, 3-25. 

Nafe, H. (2005) Potentiometric solid-state CO2 sensor and the role of electronic conductivity of the electrolyte. Sens. Actuators B, 105 (2), 119-23. 

Miura. N.. Yan. Y. Sato. M., Yao, S., Nonaka. S.. Shimizu. Y. and Yamazoe, N. (1995) Solid state potentiometric CO2 sensors using anion conductor and metal carbonate. Sens. Actuators B, 24-25, 260-5. 

Further development of new impedance-based gas sensors is likely to allow their introduction to niche applications in the field of zirconia-based, solid-state gas sensors. Impedance spectroscopy has the potential to measure changes not detectable with simple current or voltage measurements. Although it is not practical to implement complete impedance spectroscopy in an operating sensor, an optimized frequency suitable for a specific gas sensor may be used. So far, these sensors are still more complex and expensive as compared to the potentiometric zirconia-based gas sensors. However, they have two important advantages (1) measurement of total NOx concentration, regardless of the NO/NO2 ratio in exhausts and (2) near equal sensitivity to NO and NO2 at 700°C. These are essential prerequisites to their practical implementation in vehicle exhausts. Therefore, further investigation is... 

Examples of Potentiometric Gas Analysis with Solid-State Gas Sensors. 1134... 

The common element in all the electrochemical solid-state CO2 sensors is the solid electrolyte as an ionic conductor. According to the way the measurement is performed, they can be classified into two groups amperimetric and potentiometric. Electrochemical sensors for CO2 detection are usually mixed potential sensors, a subcategory of potentiometric sensors to detect other gases than oxygen. The mixed potential sensors generally involve oxide semiconductors as electrode materials. 

An application of disposable all-solid-state potentiometric electronic tongue micro-system for the discrimination of Korean green tea was reported. An ampero-metric eiectronic tongue was also employed as a sensors array system for the detection of flavor reiated phenols [53]. 

PPy is known to exhibit anionic or cationic potentiometric responses depending on the doping ion. PPy films doped with mobile inorganic anions show anionic sensitivity, while PPy films doped with anions of low mobility such as sulfate, large organic anions, or polyanions show cationic sensitivity. This bifunctionality of ionic and redox sensitivity makes PPy apphcable as an all-sohd-state, ion-selective electrode. All-solid-state, potentiometric PPy sensors were developed for potassium and sodium sensing, which showed better response time, selectivity and most importantly long-term stabihty than the coated wire electrode [130]. 

There are two basic types of solid-state chemical sensor (i) potentiometric devices, and (ii) field effect devices, e.g. ion-selective field effect transistors (ISFETs or CHEMFETs). Electrodes of the potentiometric type usually have a metal as the back contact and they also have a high output impedance. Field-effect devices are a variant of the metal oxide field-effect transistor (MOSFET) familiar in electronics, and they have a low output impedance. Hybrid devices attempt to combine the advantages of both. 

A conventional solid-state potentiometric gas sensor cmisists of two electrodes (usually comprised of porous metal layers) attached to both sides of a solid electrolyte (Fig. 3a). One electrode is exposed to the gas to be detected, while the other electrode (reference) is facing a reference gas with a constant concentration. The measured gas is converted to the predominant mobile ion of the solid electrolyte, i.e., the electrolyte should have a common species with the electrode or gas phase (gas electrode). The electrode (interface) potential of such type of electrodes, referred to as electrodes of the first... 

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