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1.
Aura Valinien Povilas Virbickas Giedr Medvikyt Arnas Ramanavi
ius 《Electroanalysis》2020,32(3):503-509
Prussian blue (PB) is an electrochromic material, which can be used as a signal transducer in the formation of optical urea biosensors. The previous researches in electrochromic properties of PB demonstrated the optical PB response to ammonium ions, which occurs when ammonium ions are interacting with PB layer at a constant 0.2 V vs Ag|AgCl|KClsat potential. In this work PB optical dependence on ammonium ions concentration was applied in the formation of electrochromic urea biosensor. Biosensor was formed by modifying the optically transparent indium tin oxide (ITO) coated glass electrode (glass/ITO) with Prussian blue layer and immobilizing urease (glass/ITO/PB‐urease). Calibration curve showed the linear dependency (R2=0.995) between the change of maximal absorbance (ΔA) and urea concentration in concentration range varying from 3 mM to 30 mM. The highest sensitivity (4 ΔA M?1) of glass/ITO/PB‐urease biosensor is in the concentration range from 7 mM to 30 mM. It was determined that working principle of the glass/ITO/PB‐urease biosensor is not related to pH changes occurring during enzymatic hydrolysis of urea. 相似文献
2.
Electrical conduction in the temperature range of 120–370 K has been studied in sandwiched structures of Al/Ta2O5/Si. The tantalum oxide films were prepared by evaporation of tantalum on a p-Si crystal substrate, followed by oxidation
at a temperature of 600°C. The temperature-dependent current-voltage (I–V) characteristics are explained on the basis of a phonon-assisted tunnelling model. The same explanation is given for I–V data measured on Ta2O5 films by other investigators. From the comparison of experimental data with theory the density of states in the interface
layer is derived and the electron-phonon interaction constant is assessed.
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3.
4.
Asta Ines Rekertait Aura Valinien Povilas Virbickas Arunas Ramanavicius 《Electroanalysis》2019,31(1):50-57
In this work, three types of electrodes suitable for amperometric glucose biosensors were designed. One type of electrode was based on bio‐selective layer of polypyrrole/(glucose oxidase)/(Prussian Blue) (Ppy/GOx/PB) and it was used as a control electrode regarding to which electrochemical properties of two other types of electrodes were compared. During the formation of Prussian blue layers graphite electrodes were additionally modified by Ni‐hexacyanoferrate (NiHCF) and by Co‐hexacyanoferrate (CoHCF) in order to design Ppy/GOx/PB‐NiHCF and Ppy/GOx/PB‐CoHCF electrodes, respectively. Some physicochemical characteristics of all three types of electrodes were evaluated and compared. The Ppy/GOx/PB‐NiHCF electrode showed wider linear range of the calibration curve than Ppy/GOx/PB and Ppy/GOx/PB‐CoHCF electrodes. The effect of temperature on analytical performance of the Ppy/GOx/PB‐NiHCF based biosensor has been evaluated and activation energy of enzyme catalysed reaction has been calculated within the temperature range of 15 °C to 30 °C. 相似文献
5.
Povilas Virbickas Gerda Ziziunaite Arunas Ramanavicius Aušra Valiūnienė 《Electroanalysis》2023,35(4):e202200230
In this research a Hg2+ ion biosensor was developed by combining Prussian blue (PB) with glucose oxidase (GOx) – an enzyme that can be inhibited by Hg2+ ions. An application of PB in the design of Hg2+ ion biosensor enabled detecting changes in hydrogen peroxide reduction current at low operational potential of 0.2 vs Ag|AgCl,KClsat. The described Hg2+ ion biosensor exhibited wide linear range from 27 μM to 247 μM of Hg2+ and higher maximal detectable concentration of Hg2+ than other GOx inhibition-based biosensors, making it convenient for the analysis of samples with high concentration of Hg2+ ions. 相似文献
6.
Norkus Eugenijus Vaškelis Algirdas Grigucevičienė Asta Rozovskis Grigorijus Reklaitis Jonas Norkus Povilas 《Transition Metal Chemistry》2001,26(4-5):465-472
Oxidation of aqueous Co(NO3)2–ethylenediamine (En) solutions with air oxygen was investigated at 20 °C and pH 5.2–7.0, with and without mechanical stirring, by measuring the CoII concentration, pH and redox potential on an Au electrode. In most cases, the oxidation rate was proportional to the concentration of CoEn
2+
n
(n = 2, 3) complexes, and the influence of the solution pH on the rate of reaction was accounted for by the pH dependence of the CoII complex distribution. It was found that sulphate inhibits and bromide accelerates the oxidation process. Possible oxidation routes are discussed. The oxidation process is limited to some extent by O2 transport from the air to the bulk solution. 相似文献
7.
Ona Adomėnienė Povilas Adomėnas Antanas Gleiznys Aldona Beganskienė Lidija Poloudina Yasuyuki Gotoh 《Molecular Crystals and Liquid Crystals》2013,570(1):739-743
Abstract A synthesis of a number of 5-alkyl-2-pyrimidinol esters was conducted, their mesomorphic properties were examined. Two ring esters of said pyrimidinols are nonmesomorphic, while three ring esters are typical mesogens, forming nematic either nematic-smectic mesophases. 相似文献
8.
Experimental results on the current-voltage characteristics of polydiacetylene (PDA) single crystals reported by Aleshin et
al [Phys. Rev. Vol. B 69, (2004) art. 214203] are reinterpreted in terms of the phonon-assisted electron tunnelling model. It is shown that
the experimental results, measured in the temperature range from 1.8 K to 300 K are consistent with the tunnelling rate dependence
on field strength, computed for the same range of temperatures. An advantage of this model over that of Aleshin et al, using
the variable range hopping (VRH) model, is the possibility of describing the behaviour of I — V data measured at both high and low temperatures with the same set of parameters characterizing this material. This assertion
is confirmed by comparison of the temperature-dependent current-voltage data extracted from Aleshin et al’s work with tunnelling
rate dependence on temperature, computed using two different expressions of the phonon-assisted tunnelling theory. The temperature
dependence of the conductivity of an ion implanted PDA crystals [B. S. Elman et al, Appl. Phys. Lett., Vol. 46, (1985) p.
100] and polypyrrole [P. Dutta et al, Synth. Met., Vol. 139 (2003) p. 201] are also explained on the basis of this model.
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9.
Laurynas Staišiūnas Konstantinas Leinartas Meilutė Samulevičienė Povilas Miečinskas Asta Grigucevičienė Remigijus Juškėnas Eimutis Juzeliūnas 《Journal of Solid State Electrochemistry》2013,17(6):1649-1656
Nanocrystalline Mg–Nb and Mg–Nb–Al–Zn alloy films were deposited by dc magnetron sputtering on glass and quartz substrates in a wide range of niobium concentrations from 6 to 80 at.%. Structural, electrochemical and corrosion properties of the films were studied by X-ray diffraction, dc voltammetry, electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance. Development of body-centred cubic Nb structure in the Mg–Nb alloy matrix yielded the effects of lattice contraction, grain refining and electrochemical passivity. The measurements showed high corrosion resistance of the films in alkaline solutions when niobium content was one third or more. An increased corrosion resistance was achieved by introducing minor amounts of Al (ca. 2 at.%). In particular, such Al effect was pronounced at lower Nb concentrations (20 to 30 at.%). Semiconductor properties of spontaneously formed oxide on Mg–Nb alloy were studied by Mott–Schottky plots, which indicated highly doped n-type oxide structures on Mg–Nb surface. The paper fills some gap in understanding of niobium–magnesium systems, which show potential for applications in hydrogen storage, switchable mirrors and corrosion protection. 相似文献
10.
Milda M. Burbuliene Rita Mazeikaite Povilas Vainilavicius 《Journal of heterocyclic chemistry》2008,45(2):607-610
Reaction of 2‐methylthio‐4(3H)‐quinazolinone with chloroacetone, ω‐bromoacetophenone or ethyl bromoacetate in different solvents (methanol, acetonitrile, dimethylformamide and toluene) using sodium methoxide or potassium carbonate as a base were studied. Regioselective N(3)‐alkylation took place in toluene using potassium carbonate, whereas in dimethylformamide O‐acylmethyl derivatives were obtained. However chloroacetone reacted with 2‐methylthio‐4(3H)‐quinazolinone under various conditions to give a mixture of N(3)/O‐isomers. 相似文献