S. S. Levichev

Enzyme semiconductor sensor based on butyrylcholinesterase

Abstract An enzyme field-effect transistor with a gelatin membrane containing butyrylcholinesterase (BCE) is investigated. The membrane formation procedure and experimental conditions are optimized. The sensor exhibits sensitivity to butyrylcholine in the range 10−4−10−2 mol/l with a response time 2 min. The influence of reversible and irreversible inhibitors on the sensor characteristics is studied.

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.

Integrated multi-sensor chip with photocured polymer membranes containing copolymerised plasticizer for direct pH, potassium, sodium and chloride ions determination in blood serum

An analytical system based on a sensor array with ion-selective field effect transistors (ISFETs) monolithically integrated in one chip covered with photocured polymer membranes containing copolymerized plasticizer and a sequential injection analysis (SIA) is shown to offer an automation of the analysis of blood serum components. For sequential injection system a custom made dual channel flow cell for the sensor array was developed. Optimisation of ion-sensitive membrane characteristics and calibration solution compositions were carried out. The system was used to analyze sodium, potassium, chloride ion contents in blood serum samples. The precision of the ion determination in samples was typical for potentiometric method with standard deviation of about 3-5%.

New photocurable composition for ISFET polymer membranes

Abstract A new ion-selective membrane composition for an ISFET based on mono- and bifunctional methacrylates is developed; the membrane can be deposited and photolithographically structured on a wafer containing the ISFETs. Compatibility of the polymer matrix with various plasticizers commonly used in PVC-based ion-selective membrane formulations is established and it is shown that the membrane may hold up to 45% of different plasticizers. The characteristics of a calcium-sensitive ISFET with the developed membrane are presented and the applicability of the photocurable polymer for potassium-sensitive membrane formation is shown.

The influence of CO2 on ISFETs with polymer membranes and characterization of a carbonate ion sensor

The influence of CO(2) and acetic acid on the response of ISFET sensors with PVC and photocured polyurethane polymer membranes with valinomycin as an ionophore was assessed. Experimental results show that the presence of these compounds has no effect on sensors parameters even after prolonged soaking in a water solution. Using a photocured polyurethane polymer as an ion-selective membrane matrix for an ISFET, a carbonate ion sensor was developed with hexyl-p-trifluoroacetylbenzoate (HE) as an ionophore. Effect of cationic and anionic lipophilic additives on the sensors response was studied. Sensors with the optimized membrane composition based on HE (7.9%, w/w) and tridodecylmethylammonium chloride (5.7%, w/w) show sensitivity of 27-30mV per decade of carbonate ion concentration, sufficient selectivity in front of chloride ions, and a lifetime of 3-5 months.

New flow-through analytical system based on ion-selective field effect transistors with optimised calcium selective photocurable membrane for bovine serum analysis

An analytical system based on ion-selective field effect transistors (ISFETs) with Ca(2+) ion selective photocurable membranes is developed to offer a semiautomatic analysis of serum calcium concentration of ruminants. Optimisation of ion-sensitive membrane composition containing different copolymerised plasticizers was performed to minimise the effect of a highly lipophilic samples on sensors characteristics. To improve the system reliability the set of calibration solutions and measurement sequence were also optimised. The system was used to determine total calcium concentration in bovine sera. The precision of the ion determination was higher than reported for double charge ions with a standard deviation of about 3-7%. It is shown that the presence of coagulant in blood serum samples does not affect the determined total calcium concentration.

Interaction of a bispyrazole-based ligand with metal cations in ethanol

A new ligand based on two pyrazole cycles linked with each other was synthesized. Its interaction with Cu(II), Ni(II), Co(II), Mn(II), Cr(III), Zn(II), and Cd(II) cations in ethanol was studied by the spectrophotometric method.

Dye molecules as nanosize sensors for low-temperature fuel cells

Dye molecules were suggested as a sensitive element for an optical sensor of parameters determining the efficiency of a fuel cell with a proton-exchange membrane, in which a water-methanol mixture is used as a fuel. The sensitivity of representatives of three different types of dyes to the concentrations of protons and methanol was examined.