Browsing by Author "P.C. Pandey"

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A new glucose biosensor based on sandwich configuration of organically modified sol-gel glass
(Wiley-VCH Verlag, 1999) P.C. Pandey; S. Upadhyay; H.C. Pathak
A new glucose biosensor was developed based on the sandwich configuration of organically modified sol-gel glasses. The new sol-gel glass was developed using 3-aminopropyltrimethoxy silane and 2-(3,4-epoxycyclohexyl)-ethyltrimethoxy silane. Two types of sol-gel glasses were used to develop glucose biosensors that differ in absence (A) and the presence of graphite powder [particle size 1-2μ] (B). An additional additive (polyethylene glycol, Mol. wt. 6000) was also incorporated in both types of the upper sol-gel glass layer. The new sol-gel matrix with immobilized glucose oxidase was analyzed by scanning electron microscopy (SEM).The sandwich configuration was developed using a bilayer of sol-gel glasses having a layer of glucose oxidase in between the bilayer. This electrode with special configuration was used to form a layer of sol-gel glass of ca. 0.2mm thickness. The performance of sol-gel glasses (A & B) was analyzed based on cyclic voltammetry using ferrocene monocarboxylic acid. The results show a diffusion limited condition of ferrocene across the sol-gel matrix. The characterization of sol-gel glass based biosensor was recorded based on the cyclic voltammograms in absence and presence of glucose. The results show an increase in anodic current which is also characteristic of hydrogen peroxide oxidation in both cases (A & B). The responses of the sol-gel glasses based biosensors were analyzed based on chronoamperometric measurements. An amplified signal on the addition of the same concentrations of glucose was recorded with the B-type sol-gel glass electrode which was attributed to its relatively high porosity and better conductivity of the graphite loaded sol-gel glass. These observations were in accordance with the results on the diffusion of ferrocene and the magnitude of anodic current resulting from hydrogen peroxide oxidation. The calibration plots for glucose analysis using both type of sensors are reported. Data on the mediated electrochemical oxidation of glucose oxidase using soluble ferrocene were also reported based on cyclic voltammograms and amperometric measurement.
A new solid-state pH sensor and its application in the construction of all solid-state urea biosensor
(Wiley-VCH Verlag, 2000) P.C. Pandey; S. Upadhyay; G. Singh; R. Prakash; R.C. Srivastava; P.K. Seth
A new solid-state pH sensor is developed using neutral poly(3-cyclohexyl thiophene) assembled over a Pt disk electrode. The new sensor is developed following two different approaches; 1) the neutral poly(3-cyclohexyl-thiophene) dissolved in chloroform and subsequent coating on to a Pt disk electrode; 2) the neutral polymer is incorporated into plasticized poly(vinyl chloride) matrix membrane. In both cases the polymer modified electrode is sensitive to pH and a reversible super Nernstian behavior is observed. The typical response of the pH sensor and its reversibility are reported. The polymer coated electrode is subsequently used to construct an all solid-state urea sensor. The construction of this new urea sensor involves the following two major steps; a) 20 μL of urease solution (40 mg/mL) is allowed to assemble overnight at 4 °C over neutral poly (3-cyclohexyl thiophene) modified electrode; b) an organically modified sol-gel layer is allowed to form over the urease adsorbed polymer modified electrode. The new solid-state urea sensor provides excellent reproducibility of the measurements and is stable for 3 months when stored at 4 °C under dry condition. The typical response of the solid-state urea sensor and the calibration plot of urea analysis are reported.
A novel ferrocene encapsulated palladium-linked ormosil-based electrocatalytic dopamine biosensor
(2001) P.C. Pandey; S. Upadhyay; Ida Tiwari; G. Singh; V.S. Tripathi
A novel finding on the development of electrocatalytic biosensor for dopamine is reported. The new electrocatalytic dopamine biosensor is developed using ferrocene encapsulated palladium (Pd)-linked organically-modified sol-gel glass (ormosil). The alkoxy precursors used for the preparation of new ormosil-based electrocatalytic biosensor are palladium-linked glycidoxypropyltrimethoxysilane and trimethoxysilane. The optimum concentrations of these precursors are added in aqueous solution of ferrocene monocarboxylic acid and HCl followed by gelation for 30 h at 25°C to form ormosil. The ferrocene encapsulated ormosil is characterized based on cyclic voltammetric measurements. The CV results shows peak separation of 57-59 mV and a linear relation between peak current and square root of scan rate suggesting well behaved reversible electrochemistry of ormosil encapsulated ferrocene. The CV results and the detection of ferrocene in working medium shows that ferrocene is not leached out of ormosil matrix. The tyrosinase is immobilized within polyvinyl alcohol over the ferrocene encapsulated new ormosil and finally mounted using nucleopore membrane. The electrocatalytic response of immobilized tyrosinase over new ormosil is observed and the results are reported. The performance, stability, and reproducibility of new ormosil-based dopamine biosensor are reported. © 2001 Elsevier Science B.V.
A novel ferrocene-encapsulated palladium-linked ormosil-based electrocatalytic biosensor. The role of the reactive functional group
(Wiley-VCH Verlag, 2001) P.C. Pandey; S. Upadhyay; Ida Tiwari; Soma Sharma
A novel palladium-linked ormosil material with encapsulated ferrocene is reported along with its application in bioelectrocatalysis. The Pdglycidoxypropyltrimethoxysilane is made by mixing an aqueous solution of palladium chloride and glycidoxypropyltrimethoxysilane. The linkage of palladium with glycidoxypropyltrimethoxysilane is confirmed by UV-vis, mass and 13C spectroscopy. It is suggested that Pd is sandwiched between two molecules of glycidoxypropyltrimethoxysilane replacing oxygen. The new ormosil is made using Pd-linked silane precursor containing ferrocene monocarboxylic acid, trimethoxysilane and HC1. The formation of ormosil at two different temperatures (10 and 30°C) is also studied, with the result that the ormosil formed at 10°C does not show electrocatalysis of glucose oxidase whereas the ormosil made at 30°C is found to be an efficient bioelectrocatalyst. The cyclic voltammetry results show peak separation of 57-59 mV of encapsulated ferrocene made at 30°C and relatively large peak separation of the one made at 10°C. The performance, stability, and reproducibility of the new ormosil based glucose biosensor are discussed. Another important investigation in support of the above outcome is reported showing the self-assembly of palladium on the reactive solid state ormosil surface. The reactive ormosil is developed using a mixture of trimethoxysilane and 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane in acidic medium.
A novel ormosil based electrocatalytic biosensor for glucose/ethanol based on dehydrogenase modified electrode
(Wiley-VCH Verlag, 2001) P.C. Pandey; S. Upadhyay; Ida Tiwari; V.S. Tripathi
A novel ormosil material for designing electrocatalytic biosensors for glucose and ethanol based on dehydrogenase catalyzed reactions is reported. The electrode material is prepared using palladium-linked glycidoxypropyltrimethoxysilane, ferrocene monocarboxylic acid, trimethoxysilane and HCl. The ormosil prepared from these ingredients shows reversible electrochemistry of ormosil encapsulated ferrocene. The electrocatalytic oxidation of NADPH/NADH and subsequently novel dehydrogenase based biosensors for glucose and ethanol are developed. The results based on cyclic voltammetry and amperometry are reported. The enzyme sensors are developed based on the modification of electrode material by dehydrogenase enzymes. The modification of electrode material is made by two approaches of enzyme immobilization: immobilization of dehydrogenase within polyvinyl alcohol and sandwiching the dehydrogenase within two layers of ormosils among which the first layer being the electrode material itself and the second layer of ormosil prepared without palladium linkage precursor and ferrocene. The biosensor made by the second approach shows high stability and much better reproducibility of enzyme electrode performance. The results on glucose and alcohol sensing based on electrochemical measurements are reported.
Acetylthiocholine/acetylcholine and thiocholine/choline electrochemical biosensors/sensors based on an organically modified sol-gel glass enzyme reactor and graphite paste electrode
(Elsevier Sequoia SA, 2000) P.C. Pandey; S. Upadhyay; H.C. Pathak; C.M.D. Pandey; Ida Tiwari
Electrochemical sensors for acetylthiocholine and acetylcholine are described. The non-mediated electrochemistry of acetylthiocholine and thiocholine is studied on the surface of graphite paste electrode and results show that acetylthiocholine is directly oxidized/reduced at >0.32 V vs. Ag/AgCl in both acidic and basic medium. In basic medium, both cathodic and anodic peak currents are less as compared to that of the same amount in acidic medium, which shows that the kinetics of non-enzymatic hydrolysis of acetylcholine into electroactive thiocholine is faster in acidic medium and slower in basic medium. Thiocholine is directly oxidized/reduced at >0.35 V vs. Ag/AgCl with relatively larger anodic current compared to cathodic peak current similar to that of acetylcholine results recorded in acidic medium (pH 6.0). The electrochemical sensor/biosensors for acetylthiocholine/acetylcholine and thiocholine/choline are developed using two enzyme reactors: (1) acetylcholinesterase (AChE) encapsulated organically modified sol-gel glass, and (2) choline oxidase (ChO) immobilized within mediators (tetracyanoquinodimethane (TCNQ), tetrathiafulvalene (TTF), and dimethyl ferrocene (dmFc))-modified graphite paste electrodes. The AChE-immobilized into organically modified sol-gel glass behaves as the reactor for enzymatic hydrolysis of acetylthiocholine/acetylcholine into thiocholine/choline, whereas mediator- and ChO-modified paste electrodes are used for the detection of thiocholine/choline through mediated mechanism. The electrochemistry of AChE-generated thiocholine is studied at the mediator-modified electrodes in the presence and absence of ChO. It is observed that thiocholine undergoes both mediated and non-mediated oxidation in the absence of ChO as well as oxidation through enzyme-catalyzed mediated reactions. The results based on cyclic voltammetry on the oxidation of thiocholine at the surface of mediator-modified electrodes in the presence and absence of ChO are reported. In the presence of the ChO large anodic current is observed near the mediator's redox potentials as compared to the anodic current in the absence of enzyme, which shows mediated bioelectrochemistry of thiocholine. The typical response curves for the detection of thiocholine/choline using mediators and ChO-modified electrodes below 0.24 V vs. Ag/AgCl in 0.1 M Tris-HCl buffer pH 8.0 are reported. Comparative analytical performance on the mediated electrochemical responses of the biosensors is discussed.
Amperometric enzyme sensor for glucose based on graphite paste-modified electrodes
(1992) P.C. Pandey; A.M. Kayastha; V. Pandey
Amperometric enzyme electrode for glucose is described based on the incorporation of glucose oxidase (GOD) into graphite paste modified with tetracyanoquinodimethane (TCNQ). The incorporated enzyme exhibits high activity and long-term stability over the earlier TCNQ-based glucose sensor (1). The sensor provides a linear response to glucose over a wide concentration range. The response time of the sensor is 15-50 sec, and the detection limit is 0.5 m M. Stable response to the substrate was obtained during a period of 35 d. Application of the sensor in the plasma analysis is reported. © 1992 Humana Press Inc.
An amperometric enzyme electrode for lactate based on graphite paste modified with tetracyanoquinodimethane
(1994) P.C. Pandey; V. Pandey; S. Mehta
An amperometric enzyme electrode for lactate is described. The construction of an enzyme electrode involves the incorporation of tetracyanoquinodimethane (TCNQ) and lactate dehydrogenase (LDH) into the graphite paste. The response of the electrode to lactate is based on the oxidation of NADH at 220 mV vs SCE based on a LDH catalyzed reaction through the mediated mechanism. Data are also reported on the oxidation of NADH within the TCNQ mediated graphite paste electrode without LDH as a function of binder composition. It has been found that the response of the electrode is decreased on increasing the binder ratio. This is attributed to the limited transport of NADH within the paste. Similarly, the effect of enzyme (LDH) concentration incorporated in the graphite paste vs the enzyme electrode response for NADH is also reported. An increase in enzyme concentration results in the decreased response of the electrode, again related to the limited mass-transport at the oil-solution interface. The response curve for lactate is slightly dependent on the anodic potential. The effects of interferences (pH and temperature) on the response of the enzyme sensor are also reported. It was found that the response is nearly constant within a 6·5-8·5 pH range whereas the variation of the temperature shows a biphasic curve on the response, probably attributed to the heterogeneous reaction at a lower temperature and homogeneous reaction at a higher temperature. The stability of the enzyme sensor is better, with a loss of a 45% response after 30 d on storage at room temperature in phosphate buffer (0.1 M, pH 7·5). © 1994.
An amperometric flow injection analysis enzyme sensor for sucrose using a tetracyanoquinodimethane modified graphite paste electrode
(Elsevier Science Ltd, 1996) J.L. Lima Filho; P.C. Pandey; H.H. Weetall
A flow injection analysis (FIA) enzyme sensor for sucrose is described. Two approaches were employed for the construction of the biosensor. In the first approach, the enzymes invertase and mutarotase were covalently coupled to controlled pore glass (CPG) particles and placed in a packed bed reactor. Glucose oxidase (GOD) and the electron transfer mediator tetracyanoquinodimethane (TCNQ) were incorporated into the graphite paste electrode. In the second approach, invertase, GOD and TCNQ were incorporated into the graphite paste electrode. The first system was capable of measuring sucrose in a concentration range of 0.025-200 × 10-3 mol/l, whereas the second system was able to measure sucrose concentrations up to 2000 × 10-3 mol/l. Assay times were 6 min with the first system and 12 min with the second system.; A flow injection analysis (FIA) enzyme sensor for sucrose is described. Two approaches were employed for the construction of the biosensor. In the first approach, the enzymes invertase and mutarotase were covalently coupled to controlled pore glass (CPG) particles and placed in a packed bed reactor. Glucose oxidase (GOD) and the electron transfer mediator tetracyanoquinodimethane (TCNQ) were incorporated into the graphite paste electrode. In the second approach, invertase, GOD and TCNQ were incorporated into the graphite paste electrode. The first system was capable of measuring sucrose in a concentration range of 0.025-200 x 10-3 mol/l, whereas the second system was able to measure sucrose concentrations up to 2000 x 10-3 mol/l. Assay times were 6 min with the first system and 12 min with the second system.
An ocean wave transformation model for shallow waters
(1998) A.K. Varma; C.M. Kishtawal; Raj Kumar; W.J. Prakash; P.C. Pandey; K.P. Singh
In this paper a coastal wave transformation model is presented. The implementation of different wave theories and the terms for refraction, shoaling, bottom friction, percolation, viscous dissipation and wave breaking are described. A few trial runs of the model have been made with various deep water wave characteristics. The change in characteristics of a shoreward propagating wave is as expected. A comparative study of model derived wave heights with satellite altimeter wave heights is also done. It is found that model derived wave heights follow the same trend as altimeter wave heights, and thus confirms the validity of the model for estimation of shallow water wave heights.
An organically modified silicate-based ethanol biosensor
(Academic Press Inc., 2001) P.C. Pandey; S. Upadhyay; Ida Tiwari; V.S. Tripathi
A novel electrocatalytic ethanol biosensor using ferrocene-encapsulated palladium (Pd)-linked organically modified sol-gel glass (ormosil) is reported. The alkoxy precursors used to prepare the new ormosil-based electrocatalytic biosensor are Pd-linked glycidoxypropyltrimethoxysilane and trimethoxysilane. Pd-glycidoxypropyltrimethoxysilane (black solution) is made by mixing aqueous solutions of palladium chloride and glycidoxypropyltrimethoxysilane. The new ormosil is made using a Pd-linked silane precursor, trimethoxysilane, an aqueous solution of ferrocene monocarboxylic acid, and HCl. Alcohol dehydrogenase (ADH) is assembled over the ferrocene-ormosil layer using polyvinyl alcohol and then protecting the immobilized enzyme layer using Millipore filter membranes (pore size 1 μm). The electrocatalytic response of immobilized ADH, soluble nicotinamide adenine dinucleotide, and Pd-linked ormosil-encapsulated ferrocene is then observed. The electrocatalytic oxidation of NADH and the subsequent ADH-catalyzed formation of NADH are monitored electrochemically. Typical results recorded after the addition of varying concentrations of ethanol are reported; however, the sensor is sensitive to other alcohol and known ADHsensitive substrates. The stability and reproducibility of the new ethanol biosensor are reported. © 2001 Academic Press.
Application of Photochemical Reaction in Electrochemical Detection of DNA Intercalation
(1994) P.C. Pandey; H.H. Weetall
A flow injection analysis (FIA) system for the detection of the compounds that intercalate within DNA is reported. A derivative of 9,10-anthraquinone has been used as the reference compound for photoelectrochemical detection. The sodium salts of 9,10-anthraquinone-2,6-disulfonic acid and 9,10- anthraquinone-2-suifonic acid are photochemically activated and then reduced in the presence of an electron donor (glucose). The electrochemical signal is based on the measurement of the anodic current resulting from the oxidation of the reduced form of 9,10-anthraquinone. The reduced form of the 9,10- anthraquinone is oxidized through a mediated mechanism at the surface of a tetracyanoquinodimethane-(TCNQ)-modified graphite paste electrode covered by a Nucleopore membrane. TCNQ acts as an efficient mediator for the oxidation of reduced 9,10-anthraquinone. Cyclic voltammetry, photocyclic voltammetry, and the photoelectrochemical FIA response of 9,10- anthraquinone are reported. Experimental results show that these anthraquinones can be intercalated within the helix of double-stranded calf thymus DNA. The anthraquinone molecules that are intercalated within DNA cannot be oxidized due to their limited transport to the modified electrode surface. This results in a decrease in the anodic current at a constant concentration of anthraquinone after intercalation. There is a linear relation between the decrease in electrochemical response and the DNA concentration at a constant concentration of anthraquinone. The intercalated anthraquinone molecules can be completely replaced by another intercalating agent (i.e., ethidium bromide) that is more strongly intercalated within DNA, thereby regenerating the electrochemical response. The calibration curve for the analysis of this compound is reported. © 1994, American Chemical Society. All rights reserved.
Attenuation of metal toxicity by frankial siderophores
(2010) A. Singh; S.S. Singh; P.C. Pandey; A.K. Mishra
In order to investigate the role of frankial siderophores in minimizing metal toxicity, Frankia strains were grown at different concentrations of Mg2+, Cu2+, and Zn2+. Growth was observed up to 500 mmol L-1 Mg2+, 10 μ mol L-1 Cu2+, and 10 μmolL-1 Zn2+ while the maxima were at 200 μmol L-1 Mg2+, 1 μmol L-1 Cu2+, and 1 μmol L-1 Zn2+. The siderophore production was increased up to 500 μmol L-1 Mg2+, 10 μmol L-1 Cu2+, 100 μmol L-1 (hydroxamate type), and 200 μmol L-1 (catecholate type) Zn2+ while maximum production was found at Mg2+ (200 μmol L-1), Cu2+ (10 μmol L-1), and Zn2+ (10 μ molL-1). The results suggested that the growth was protected at higher concentrations of Mg2+ (up to 500 μmol L-1), Cu2+ (10 μ molL-1), and Zn2+ (10 μ mol L-1), possibly due to enhanced siderophore production. Thus, siderophores minimize the metal-induced inhibition of growth in Frankia, likely due to regulation of nutritional imbalances and metabolic processes during adaptation towards metal stress and/or metal toxicity. © 2010 Taylor & Francis.
Bistability and electrokinetic oscillations
(Academic Press Inc., 1999) R.P. Rastogi; G.P. Mishra; P.C. Pandey; Kanchan Bala; K. Kumar
Nonlinear dynamic behavior and electrokinetic oscillations have been investigated for the membrane systems (a) 0.1 N NaCl/KCl parallel with Millipore filter parallel with 0.01 N NaCl/KCl; (b) 0.1 N NaCl/KCl parallel with Whatman Inorganic filter parallel with 0.01 N NaCl/KCl; and (c) 0.1 N NaCl/KCl parallel with silver-coated filter parallel with 0.01 N NaCl/KCl, from the viewpoint of testing the theories for the phenomena and elucidating the mechanism. To achieve these objectives, studies on hydrodynamic permeability, electroosmotic permeability, bistability, and electrokinetic oscillations were undertaken. Relaxation time for buildup and decay of electroosmotic pressures was experimentally determined. Bistability was not observed showing that it is not a prerequisite for oscillations and nonlinear relations between (J(v))(Δρ=0) and ΔΦ involving cubic or higher-order terms are necessary for bistability. The oscillations were studied at different current strengths. The period is found to be independent of current, while amplitude A is found to be linearly related to current I which is the bifurcation parameter. The bifurcation point occurs at ~0.4 mA. Studies have also been made with membranes of different pore size that show that amplitude increases with increase in pore size of the membranes. The validity of the two-variable model of Teorell was examined by comparing the experimental results with computer simulation based on parameters determined experimentally. Theory does not meet expectation and the results suggest that modification of theory is needed. The weakness of the theory has been critically examined.
Characterization of electropolymerized polyindole: Application in the construction of a solid-state, ion-selective electrode
(Electrochemical Society Inc., 1998) P.C. Pandey; R. Prokash
The characterization of polyindole made by anodic electropolymerization of indole monomer in dichloromethane is reported based on scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results on SEM snow that the granules in the polymer film are arranged in an ordered manner. The domain of the nuclei in the film made under potentiostatic condition is much smaller as compared to the domain of the nucleation in the polymer film made under potentiodynamic condition. The DSC data shows that the polymer is stable at higher temperature. A solid-state potassium ion-selective electrode (ISE) using polyvinyl chloride (PVC) matrix membrane impregnated with valinomycin at the surface of the polyindole-modified electrode is reported Neutral-carrier impregnated PVC membrane is formed by casting over the surface of the polyindole-modified electrode. The resulting ISE without the incorporation of polyanions in the polyindole film shows high selectivity to K* with negligible drift of the baseline potential with a slope of 59 mV/dec within Nernstian behavior. The detection limit of the potassium ion sensor is 6 × 10-6 M with a wide linearity over almost 5 dec. Typical responses of the neutral-carrier impregnated PVC membrane over the polyindole-modified electrode to potassium ion is reported.
Conducting polymer-coated enzyme microsensor for urea
(1988) P.C. Pandey; A.P. Mishra
A microsensor for urea is described which is based on immobilised urease on the tip of a 10 um diameter ammonia gas electrode made from a polypyrrole film coated on to a platinum wire. The sensor responds rapidly, reaching a steady state within 20-40 s when the concentration of urea in solution is changed from 0.0001 to 0.05 M. The enzymatic response is current limiting. Responses in a wide range of substrate concentrations were achieved (0.001-0.05 M). High storage and operational stability {more than 32 d) have been recorded for the urea microsensor.
Construction of Ru(II) polypyridyl based macrocycles: Synthesis, characterization, electrochemical, Li+ binding, antitumour and anti-HIV properties
(Freund Publishing House Ltd, 2001) L. Mishra; R. Sinha; P.C. Pandey
Some ruthenium (II) polypyridyl complexes with a bis-chalcone (obtained by the condensation of 3-methyl-thiophene-2-carboxaldehyde and 4-acetyl pyridine) have been synthesized and characterized spectroscopically (IR, NMR, UV/Vis), conductimetric, elemental analysis and FAB mass data. Their luminescent, redox and Li+ binding properties have been studied. The anti-HIV and antitumour activities have also been reported.
Copper (II) ion sensor based on electropolymerized undoped-polyindole modified electrode
(Elsevier Sequoia SA, 1999) P.C. Pandey
A solid-state copper (II) ion sensor based on the application of electropolymerized polyindole-modified electrode is reported. The new sensor shows high selectivity to Cu2+ ions. The polyindole-modified electrode is formed by the electropolymerization of the indole monomer in dichloromethane containing tetrabutyl ammonium perchlorate (TBAP). The polyindole-modified electrode is reduced electrochemically, followed by incubation of the electrode in 1 M KCl solution overnight in order to further remove the perchlorate ions from the polymer interstices. The resulting undoped polyindole shows high sensitivity to Cu2+ ions with a slope of 140 mV/decade within the 10-4-10-3 M concentration range. The sensor is less sensitive to Pb2+ ions with negligible response to Ni2+, Co2+, Fe2+ and Zn2+. A calibration curve for the analysis of Cu2+ ions is reported. For practical applications, the polymer-modified electrode is highly stable for more than 5 months.
Copper(II) ion sensor based on electropolymerized undoped conducting polymers
(2002) Rajiv Prakash; R.C. Srivastava; P.C. Pandey
A solid state copper(II) ion sensor is reported based on the application of electropolymerized undoped (neutral) polycarbazole (PCz) and polyindole (PIn) modified electrodes. The new sensor shows high selectivity to Cu2+ ions with a detection limit of 10-5 M. PCz and PIn are formed respectively by the anodic oxidation of 50 mM carbazole and 5 mM indole monomers in dichloromethane containing 0.1 M tetrabutylammonium perchlorate on a platinum electrode using a single compartment cell. Potentiostatic polymerization of both the monomers are carried out at 1.3 V and 1.0 V vs. Ag/AgCl, respectively. Perchlorate ions were electrochemically removed from the polymer films by applying -0.2 V vs. Ag/AgCl. Polymer-coated electrodes are incubated in 1 M KCl solution for 8 h followed by incubation in distilled water for 2 h before using as a metal ion sensor. The undoped PCz and PIn electrodes were found to be highly selective and sensitive for Cu2+ ions with little selectivity for Pb2+ and negligible response towards Ag+, Hg2+, Cu+, Ni2+, Co2+, Fe2+, Fe3+ or Zn2+. Potentiometric responses for Cu2+ ions are recorded for both the sensor electrodes together with a double-junction Ag/AgCl reference electrode. Calibration curves for Cu2+ are reported for both ion sensors. The polymer-modified electrodes were found to be stable for several weeks.
Dependence of M, N and O states decay kinetics of D96N bacteriorhodopsin on amine and amino compounds and its application in chemical sensing
(Elsevier, 1998) P.C. Pandey; B.C. Upadhyay; C.M.D. Pandey; H.C. Pathak
The dependence of the kinetics of M, N and O states decay of the D96N bacteriorhodopsin (BR) on (i) ammonium ion and (ii) an aromatic amine is reported. The kinetics of decay back to trans BR at 410, 530 and 640 nm, which are the absorption maximum for M, N and O states, respectively, in presence and absence of these analytes are studies for better understanding of the kinetics of M state decay back to trans BR as reported earlier [P.C. Pandey et al. Sensors and Actuators, 35-36 (1996) 470-474]. The half time (T1/2) of these decays and absorption spectra are measured at 410, 530 and 640 nm, respectively. The half time(T1/2) of these decay at 410 nm increases in the presence of amine whereas it decreases in the presence of amino compounds as compared with control. Similar trends have been observed at 530 and 640 nm. The reverse is observed on the measurement of absorption. The variation of these parameters are more apparent when measurements are carried out at 530 nm. The application of the kinetic data in the construction of chemical sensors is discussed and the analysis of ammonium ion and amine is reported. © 1998 Elsevier Science S.A. All rights reserved.