Yu. E. Ermolenko

Portable light-addressable potentiometric sensor (LAPS) for multisensor applications

Abstract A novel design of the light-addressable potentiometric sensor (LAPS) for realisation of a portable multisensor device is presented. Light sources and electronics including an oscillator, a multiplexer, a pre-amplifier and a high-pass filter are encapsulated in a pen-shaped case, on which the sensor plate is mounted. This sensor device is capable of measuring up to four different ion species by integrating different ion-selective materials on the sensing surface, each illuminated with an independent light source. The novel design of the sensor system is expected to make the measurement easier and to enlarge the field of practical applications.

Chemical sensors and their systems

The review presents a short record of the evolution of chemical sensors (ion selective electrodes) and multisensor systems of an electronic tongue type, based on the organization principles similar to those of biological sensors. The main types of chemical sensors and multisensor electronic tongue combinations elaborated today are considered along with sensitive materials used in them. Recent advances in chemical sensors, for example, lower detection limits and so-called true selectivity are scrutinized. Also, some widespread analytical applications of electron tongues, including those for the identification and classification of liquid media, for the quantification of various components in there, for the control of industrial processes, as well as the type and intensity evaluation of the taste of food and medications are discussed.

K+-selective field-effect sensors as transducers for bioelectronic applications

A K + -sensitive capacitive electrolyte-membrane-insulator-semiconductor (EMIS) sensor has been developed. The sensor utilizes a valinomycin-containing PVC-based membrane with different contents of plasticizer. This new type of sensor has been investigated in terms of its intrinsic characteristics, like impedance behavior, capacitance/voltage characteristics and frequency dependence. The optimized working conditions of the sensor and various membrane compositions have been studied with regard to the sensitivity performance in different electrolytes. The possibility of future applications for the measurement of extracellular potassium-ion concentrations are discussed.

Anion-selective light-addressable potentiometric sensors (LAPS) for the determination of nitrate and sulphate ions

The technology of fabrication of anion-selective light-addressable potentiometric sensors (LAPS) by using a solid-state microelectronic device integrated with an ion-recognition membrane has been elaborated. The nitrate sensor with ion-exchange membrane exhibits a linear response interval of 3 � 10 � 5 to 1 � 10 � 1 mol/l NO3 � with an ionic sensitivity of 58 � 2 mV/pNO3. The detection limit was found to be 1 � 10 � 5 mol/l of nitrate ions and the working pH interval of the sensor is 2.0–11 for 10 � 2 mol/l NO3 � . The sensor has a high selectivity for nitrate over chloride, sulphate, hydrogen phosphate and acetate ions with selectivity coefficients, KNO3=X ,o f 7� 10 � 3 ,1 � 10 � 3 ,2 � 10 � 4 and 5 � 10 � 3 , respectively, and a response time of about 1 min. The SO4-LAPS with polymeric membrane containing neutral sulphate ionophore demonstrates a sensitivity of 26 � 1 mV/pSO4 in a concentration range of 3 � 10 � 6 to 1 � 10 � 2 mol/l with a reasonable selectivity over chloride, hydrogen carbonate and hydrogen phosphate ions. Selectivity coefficients, KSO4=X, were found to be 0.6, 0.15 and 0.03, respectively.

The double K+/Ca2+ sensor based on laser scanned silicon transducer (LSST) for multi-component analysis.

In the present work a double ion sensor based on a laser scanned semiconductor transducer (LSST) for the simultaneous determination of K(+)- and Ca(2+)-ions in solutions has been developed. Specially elaborated ion-sensitive membrane compositions based on valinomycin and calcium ionophore calcium bis[4-(1,1,3,3-tetramethylbutyl)phenyl] phosphate (t-HDOPP-Ca) were deposited as separate layers on a silanized surface of the Si/SiO(2)/Si(3)N(4)-transducer. The proposed multi-sensor exhibits theoretical sensitivities and the detection limits of the sensor were found to be 2 x 10(-6) mol l(-1) for K(+) and 5 x 10(-6) mol l(-1) for Ca(2+). The elaborated double sensor is proposed for the first time as a prototype of a new type of multi-sensor systems for chemical analysis.

Diffusion of Tl-204 isotope and ionic conductivity in Tl4HgI6 membrane material for chemical sensors

Method for solid-phase synthesis of Tl4HgI6 was developed and the diffusion coefficients of thallium-204 isotope were determined for this compound for the first time. Data on the ionic conductivity and diffusion of thallium ions were obtained and used to calculate the defect concentration and mobility in the thallium sublattice.

Thallium-selective sensor with a membrane based on Tl4HgI6 ionic conductor

Tl4HgI6 solid electrolyte with a high ionic component of conductivity was synthesized for developing a thallium-sensitive sensor. The main sensor characteristics (tilt angle, detection limit, selectivity, pH range, potential drift) of the new thallium sensor were determined. The time stability of its operation and various ways of its application for determining thallium ions in solutions are demonstrated.

Ag2S-As2S3-TlI chalcogenide glasses as perspective material for solid-state chemical sensors

Modern research techniques with radioactive isotopes were used to study the transport characteristics, (conductivity and diffusion) in chalcogenide membrane materials of the Ag2S-As2S3-TlI system. It was demonstrated that, on raising the silver sulfide concentration in a glass, the total electrical conductivity grows by two orders of magnitude, which is due to the pronounced change of the band structure and to the increase in the electronic component of the conductivity. New chemical sensors for determination Tl ions in solutions were developed on the basis of these solid-state studies.

Solid-State Thin-Film Sensors Based on Chalcogenide Materials Obtained by Planar Technology and Pulsed Laser Deposition

Methods of silicon planar technology and pulsed laser deposition were applied to fabricate fully solid-state chemical sensors for determining ions of copper, lead, cadmium, thallium, and also sulfide and chloride ions on the basis of thin chalcogenide films as ion-sensitive membranes.

Diffusion of silver and ionic conductivity in the solid electrolytes Ag8HgS2I6 and Ag6I4WO4

Abstract Ionic conductivity and silver diffusion in the Ag8HgS2I6 and Ag6I4WO4 superionic conductors have been studied. The obtained diffusion coefficients of the silver ions are in equations: Ag8HgS2I6 (100–260°C) D ∗ =2.3×10 −4 exp (−0.128 eV /kT) , Ag6I4WO4 (100–200°C) D ∗ = 6.0×10 −4 exp (−0.183 eV /kT) . The calculated values of Haven ratio confirm the existence of essential differences in transfer properties for the solid electrolytes with α-AgI-type structure.