Yu. Mourzina

Development of multisensor systems based on chalcogenide thin film chemical sensors for the simultaneous multicomponent analysis of metal ions in complex solutions

Abstract A new type of thin film chemical microsensors based on chalcogenide glass-sensitive materials was developed by means of silicon planar technology and pulsed laser deposition technique. These miniaturised ion-selective electrodes (ISEs) exhibit Nernstian responses over five concentration decades with detection limits of 1×10 −7 mol/l towards the primary ions Cu and Pb, and 4×10 −7 and 3×10 −5 mol/l towards Cd and Tl, respectively. The thin film microsensors have been shown to be perspective instruments for the simultaneous multicomponent analysis of complex liquid media based on the principles of an ‘electronic tongue’ device. Incorporating the thin film sensors into a sensor array allowed the multicomponent analysis of heavy metal-ion species (Pb 2+ , Cd 2+ , Zn 2+ and Fe 3+ ). The concentrations of Pb 2+ -, Cd 2+ - and Zn 2+ -ions can be determined simultaneously by direct potentiometric measurements using a sensor array of seven all-solid-state thin film chemical microsensors with an accuracy of 15–30%. The sensor array allows overcoming the problem of an insufficient selectivity of single sensors. The suggested microsystem-compatible fabrication technique favours a further miniaturisation, aimed to a fully integrated electrochemical microsystem.

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.

Copper, cadmium and thallium thin film sensors based on chalcogenide glasses

All-solid-state copper, cadmium and thallium sensors based on chalcogenide thin film layers prepared by means of the pulsed laser deposition (PLD) technique have been developed. The sensitive layers have been investigated using Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM). The electrochemical behaviour of the sensors in terms of ionic sensitivity, limit of detection, Nernstian response interval, the effect of the pH, selectivity coefficients, dynamic response time and drift has been evaluated. The results of copper, cadmium and nickel analysis in industrial solutions using the developed sensors are presented.

Pulsed Laser Deposition – An Innovative Technique for Preparing Inorganic Thin Films

The pulsed laser deposition (PLD) technique, originally invented in the seventies, has been investigated as an alternative preparation method to realize thin film materials for chemical microsensor applications. Dielectric oxide materials of Al2O3 and Ta2O5 serve as pH-sensitive gate insulators for capacitive EIS (electrolyte-insulator-semiconductor) structures. Chalcogenide glass materials are the basis of potentiometric thin film ISEs (ion-selective electrodes): Their application field is the heavy metal determination of, e.g., cadmium, lead, copper and thallium. For both sensor types a high, nearly-Nernstian sensitivity, a good long-term stability, a short response time and a selectivity behavior that is comparable with macroscopic bulk sensors have been achieved.

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.