Ana Guadalupe | University of Puerto Rico Rio Piedras (original) (raw)
Papers by Ana Guadalupe
ECS Meeting Abstracts, 2010
not Available.
Biosensors '94, 1994
This chapter discusses a study focusing on coupling of electrochemical and enzymatic reactions fo... more This chapter discusses a study focusing on coupling of electrochemical and enzymatic reactions for controlled drug release. Copolymers of 4-vinylpyridine (4-VP) and vinylferrocene (VF) quaternized with 1-chloroethanol or iodomethane were synthesized and the enzyme, glucose oxidase (GOx) incorporated by covalent bonding to the pyridine. The copolymers were synthesized in a 1:7 and 1:1 mole ratio of VF/4-VP, respectively. Spectrophotometric assay of enzyme activity demonstrated that the enzyme was active after its immobilization in the copolymers. Carbon paste electrodes were prepared by mixing the paste with the copolymers. They were tested for the electroregeneration of the enzyme cofactor when dipped in a glucose solution 0.5549 M, at pH 5.1 in acetate buffer or at pH 7.1 in phosphate buffer solution. The studies were conducted using cyclic voltammetry and amperometry. Small catalytic current was observed as a result of the enzymatic reaction. Pellets of 4-VP and VF copolymer quaternized with 1-chloroethanol with the immobilized GOx and insulin incorporated by physical entrapment were made. The release of insulin was monitored measuring its absorbance in 278 nm as function of time. Insulin release was observed with an approximate t R (95%) = 9.18 min.
The Journal of Physical Chemistry A, 1997
... Laura A. Worl, Sharon Gould, Ana Guadalupe, B. Patrick Sullivan, § Jonathan V. Caspar, Ro... more ... Laura A. Worl, Sharon Gould, Ana Guadalupe, B. Patrick Sullivan, § Jonathan V. Caspar, Robert L. Leasure, James R. Gardner, and Thomas J. Meyer*. ... (1) For general reviews see: (a)Balzani, V.; Juris, A.; Venturi, M.; Camagna, S.; Serroni, S. Chem. Rev. 1996, 96, 759. ...
![Research paper thumbnail of Novel chemical pathways and charge-transport dynamics of electrodes modified with electropolymerized layers of [Co(v-terpy)2]2+](https://attachments.academia-assets.com/92726419/thumbnails/1.jpg)
](Journal of the American Chemical Society, 1988
Electropolymerized films of [Co(~-terpy)~]*' (v-terpy is 4'-vinyl-2,2':6',2''-terpyridinyl) exhib... more Electropolymerized films of [Co(~-terpy)~]*' (v-terpy is 4'-vinyl-2,2':6',2''-terpyridinyl) exhibit reactivity patterns, especially with regard to ligand exchange, that differ significantly from those exhibited by [ C~(t e r p y)~]~+ in solution. These differences are attributed to the physically constrained environment present in the polymer f h. The charge-transport properties follow the model of Dahms and Ruff and the predicted concentration dependence of the diffusion coefficient. These electropolymerized films are also active in the electrocatalytic reduction of carbon dioxide.
Journal of the American Chemical Society, 1987
4'-Vinyl-2,2':6',2"-terpyridinyl was conveniently prepared from 2-acetylpyridine via a-oxoketene ... more 4'-Vinyl-2,2':6',2"-terpyridinyl was conveniently prepared from 2-acetylpyridine via a-oxoketene dithioacetal methodology, the intermediate 4'-(methylthi0)-2,2':6',2''-terpyridinyl being converted into the corresponding 4'-methyl derivative with methylmagnesium bromide and bis(triphenylphosphino)nickel(II) dichloride followed by generation of the methyl anion with lithium tetramethylpiperidide, reaction of the anion with chloromethyl methyl ether, and introduction of the vinyl group by treatment of the ether with potassium tert-butoxidelTHF. Analogous reactions led to the 4-vinyl-and 6-vinyl isomers by using the appropriate methyl-substituted 2-acetylpyridine except that in these instances desulfurization of the 4'-rnethylthio group with nickel boride was an additional step. These vinyl-substituted ligands formed a variety of readily electropolymerizable simple and mixed-ligand complex monomers with cobalt. ruthenium, and iron with polymerization rates whose magnitude varied with position and number of vinyl substituents. Interest in the use of 2,2'-bipyridinyl as a ligand for transition-metal ions continues unabated,' and, more recently, vinylsubstituted 2,2'-bipyridinyls have been utilized* in polymer formation, in chemically modified electrode studies,3a4 and in solar energy c o n~e r s i o n .~~f The results obtained in these studies strongly suggested that analogous terpyridinyl derivatives would be of special i n t e r e~t .~ However, apart from terpyridinyl itself and several aryl-substituted derivative^,^ very few terpyridinyls and especially vinyl-substituted terpyridinyl ligands have been described in the literature. Their coordination chemistry, electrochemistry and polymerization chemistry remain relatively unexplored areas. In this publication we describe the first syntheses of the title ligands 1-3 and related derivatives, and their application in the preparation and electropolymerization of new simple-and mixed-ligand vi-nyI-"2':6',2''-terpyridinyl coordination complex monomers. 3 v 2 d I Synthesis of Ligands The parent 2,2':2',2"-terpyridinyl ligand, although first isolated6 in 1932, has usually been made by coupling procedures which present obstacles when considered for the synthesis of substituted terpyridinyls. This is especially true for methyl-substituted terpyridinyls which are conceptually precursors to vinyl-substituted terpyridinyls. W e have recently described' the synthesis of 2,2':6',2"-terpyridinyl utilizing a-oxoketene dithioacetal methodology,' and variation of this synthetic route now provides ready access to 4-, 6-, and 4'-methyI-2,2':6',2''-terpyridinyls. 4and 6-Methyl-2,2':6',2"-terpyridinyls were prepared by reaction of 2-acetylpyridine potassium enolate with 1 equiv of carbon disulfide followed by 2 equivs of methyl iodide to give the cor
Journal of Physics: Conference Series, 2013
This report describes the synthesis of [Ru(Fe-Phen)2dppz](PF6)2 (Ru-Fe complex) for a label-free ... more This report describes the synthesis of [Ru(Fe-Phen)2dppz](PF6)2 (Ru-Fe complex) for a label-free approach to detect DNA hybridization. The Ru-Fe complex showed oxidation signals at +608 mV and +1192 mV corresponding to the RuII/III and FeII/III centers, respectively. We used the Ru-Fe complex and the Ferrocene covalently attached to the target to monitor the hybridization event of a 70-mer oligo immobilized in 10.3KD NHS-PS-NHS. The lowest target detectable concentration for the DNA fragment was around 0.4 μM.
Journal of Pharmaceutical and Biomedical Analysis, 1999
A functionalized sol-gel thin film modified glassy carbon electrode has been prepared for the det... more A functionalized sol-gel thin film modified glassy carbon electrode has been prepared for the determination of mercury. The tetrasulfide in the sol-gel matrix has a high affinity for mercury species. The chemically integrated functional groups in the sol-gel precursor ensure a high chemical and mechanical stability of the modified electrodes, and therefore a stable and reproducible analytical performance. By medium exchange anodic stripping voltammetry, this modified electrode allows reliable, low cost and interference-free determination of mercury.
Journal of The Electrochemical Society, 2010
Electrochemical and Spectroscopical Characterization of Ferrocenyl Chalcones. [Journal of The Ele... more Electrochemical and Spectroscopical Characterization of Ferrocenyl Chalcones. [Journal of The Electrochemical Society 157, F104 (2010)]. Rocío A. Cardona, Kenneth Hernández, Laura E. Pedró, Myrna R. Otaño, Ingrid Montes, Ana R. Guadalupe. Abstract. ...
Journal of Biotechnology, 2005
The immobilization of short ss-DNA (18-and 36-mer) and their hybridization were studied at gold a... more The immobilization of short ss-DNA (18-and 36-mer) and their hybridization were studied at gold and glassy carbon substrates modified with low molecular weight (∼12, 18 and 24 kg/mol) polystyrene thin films. Amino-modified DNA was attached to the surface by reaction with succinimide ester groups bound to the polystyrenes. A ferrocene modified DNA target was used to confirm the probe-target hybridization. Atomic force microscopy studies showed significant morphological changes after probe immobilization and hybridization compared to the featureless structure of the polystyrene film. Single-stranded DNA samples had a globular morphology with an average density of 3.8 and 2.2 (×10 11) globules/cm 2 for the 18-and 36-mer, respectively. The formation of a porous structure with a 2.0 and 1.0 (×10 11) average pore density corresponding to the 18-and 36-mer was observed after hybridization. A surface composition analysis was done by X-ray photoelectron spectroscopy to confirm and support the images interpretation. Ferrocene oxidation (+323 mV/18-mer, +367 mV/36-mer, versus Ag/AgCl) proved the presence of ds-DNA at the modified surfaces.
Inorganica Chimica Acta, 2000
Ruthenium polypyridyl complexes containing 2,2′-bipyrimidine, [Ru(bpy)2bpm](PF6)2 (I) and [Ru(phe... more Ruthenium polypyridyl complexes containing 2,2′-bipyrimidine, [Ru(bpy)2bpm](PF6)2 (I) and [Ru(phen)2bpm](PF6)2 (II), were synthesized with high yield and purity. An extensive characterization was carried out using ESMS, UV–Vis, 1H and 13C NMR, electrochemistry and X-ray single crystal diffraction analysis. The experimental results show that the spectroscopic and electrochemical properties of I and II are similar to those of their parent complexes [Ru(bpy)3](PF6)2
Inorganic Chemistry, 1992
complexes: Pd (1.0) < Ni (1.7) < Pt (10.2), determined in methanol.29a Qualitative studies of the... more complexes: Pd (1.0) < Ni (1.7) < Pt (10.2), determined in methanol.29a Qualitative studies of the acidities of group 9 complexes give the following order of decreasing acidities: HRhL4 > HCoL4 > HIrL, (L = CO, PF3, re~pectively).~, Recently, Morris and c o-w o r k e r~~~ reported increasing pK, values of ~~U~~-[MH(~~-H~)(PR~CH~CH~PR~)~]+ (R = Ph, p-CF3C6H4) complexes in the order Fe < Os < Ru. This latter example and that of 3 and 8 (Table I) are the first reported examples of a reversal between complexes of second-and third-row metals. A H H M of Cp*,M, Where M = Ru, Os. The basicities of the C P *~M complexes, 9 and 10, also increase on going down the column from Ru (A H H M =-19.0 kcal mol-') to OS (AHHM =-26.6 kcal mol-'). In terms of equilibrium constants for protonation, 10 is 4 X lo5 times more basic than 9 assuming ASe is the same for both reactions. Qualitative studies of the basicities of Cp2Fe and Cp2Ru reported p r e v i o~s l y~~~.~~ indicate that the Ru complex is more basic than the Fe complex. This suggests that Cp*zFe will also be less basic than Cp*,Ru (9) although we were unable to obtain a A H H M value for Cp*,Fe. In contrast to those of complexes 1,2, and 7 above, the electrochemical potentials (vs SCE in CH2C12)33 of 9 (Ell2 = 0.55 V) and 10 (Ell2 = 0.46 V) decrease as one goes down the group. Basicities of Organonitrogen Complexes, A H H N. The wide range of A H H M values from-19.0 kcal mol-' for complex 4 to-38.7 kcal mol-' for complex 6 demonstrates that substantial changes in metal basicity occur upon changing the metal and/or the chelate ligand. A comparable range of A H H N values was (34) (a) Vidal,
Electrochimica Acta, 1991
Studies on the transport properties of the cationic dyes methylene blue, thionine, safranine and ... more Studies on the transport properties of the cationic dyes methylene blue, thionine, safranine and meldola blue in Nafion-coated electrodes are reported. Diffusion coefficients for the reduced and oxidized forms of the dyes are unusually high (up to 9 × 10−7 cm2s−1 at low dye concentrations in the film and show a dramatic decrease with increasing concentration. The results are interpreted in terms of recently proposed models for transport through Nafion as well as to the formation of dye dimers and/or higher aggregates in the Nafion film. This is demonstrated for methylene blue by spectrophotometric experiments where the dye was incorporated in Nafion films at different concentrations.
Electroanalysis, 2006
We present a carbon paste electrode (CPE) modified using the electron mediator bis(1,10-phenanthr... more We present a carbon paste electrode (CPE) modified using the electron mediator bis(1,10-phenanthroline-5,6-dione) (2,2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-bipyridine)ruthenium(II) ([Ru(phend)(2)bpy](2+)) exchanged into the inorganic layered material zirconium phosphate (ZrP). X-Ray powder diffraction showed that the interlayer distance of ZrP increases upon [Ru(phend)(2)bpy](2+) intercalation from 10.3 Å to 14.2 Å. The UV-vis and IR spectroscopies results showed the characteristic peaks expected for [Ru(phend)(2)bpy](2+). The UV-vis spectrophotometric results indicate that the [Ru(phend)(2)bpy](2+) concentration inside the ZrP layers increased as a function of the loading level. The exchanged [Ru(phend)(2)bpy](2+) exhibited luminescence even at low concentration. Modified CPEs were constructed and analyzed using cyclic voltammetry. The intercalated mediator remained electroactive within the layers (E°&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; = -38.5 mV vs. Ag/AgCl, 3.5 M NaCl) and electrocatalysis of NADH oxidation was observed. The kinetics of the modified CPE shows a Michaelis -Menten behavior. This CPE was used for the oxidation of NADH in the presence of Bakers&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; yeast alcohol dehydrogenase. A calibration plot for ethanol is presented.
Chemistry of Materials, 1999
A Prussian Blue (PB) sol-gel composite thin film was prepared via post-chemical derivatization of... more A Prussian Blue (PB) sol-gel composite thin film was prepared via post-chemical derivatization of a functionalizable sol-gel thin film. Bis[3-(triethoxysilyl)propyl] tetrasulfide (SIS) forms tough and crack-free films by sol-gel process with excellent adhesion on various solid surfaces. The sulfur chain (-S 4-) can be chemically oxidized to sulfonic groups (-SO 3-). After oxidation, PB sol-gel composite thin films were prepared by ion-exchange with ferrous ion followed by complexation with ferricyanide. The PB sol-gel composite thin films were characterized by electrochemistry, spectroscopy, and microscopy. Applications in the development of a potassium ion-selective electrode and an optical pH indicator are demonstrated.
Chemical Communications, 1999
A functional aerogel composed of interconnected silica nanoparticles has been synthesized from a ... more A functional aerogel composed of interconnected silica nanoparticles has been synthesized from a metastable lamellar composite based on a novel type of cooperative interaction between silica and surfactant species.
Bioelectrochemistry and Bioenergetics, 1994
... Bioelectrochemistry and Bioenergetics, 34 (1994) 169-175 Ruthenium complexes as redox mediato... more ... Bioelectrochemistry and Bioenergetics, 34 (1994) 169-175 Ruthenium complexes as redox mediators for malate and lactate dehydrogenases Neftali Rivera, Yanira Colon and Ana R.Guadalupe Department of Chemistry, PO ... 10 SA Wring and JP Hart, Analyst, 117 (1992) 1215. ...
Analytical Letters, 1986
The analytical utility of electrodes modified with functionalized polymer films for the determina... more The analytical utility of electrodes modified with functionalized polymer films for the determination of aromatic amines is demonstrated. The analysis is based on the preconcentration of the protonated amines into a functionalized polymer film that contains styrene sulfonate groups. Good sensitivity and high reproducibility were obtained for concentrations down to 10 M. Aliphatic amines do not interfere in the determination.
Analytical Chemistry, 1985
Analytical Chemistry, 1985
Flgure 7. Primary ion dose dependence for a category C (damage products) fragment ion (Table V): ... more Flgure 7. Primary ion dose dependence for a category C (damage products) fragment ion (Table V): (-) m / e 72 (C6-). tional groups also can be monitored by using the ion microscope and correlated with quantitative XPS data.
ECS Meeting Abstracts, 2010
not Available.
Biosensors '94, 1994
This chapter discusses a study focusing on coupling of electrochemical and enzymatic reactions fo... more This chapter discusses a study focusing on coupling of electrochemical and enzymatic reactions for controlled drug release. Copolymers of 4-vinylpyridine (4-VP) and vinylferrocene (VF) quaternized with 1-chloroethanol or iodomethane were synthesized and the enzyme, glucose oxidase (GOx) incorporated by covalent bonding to the pyridine. The copolymers were synthesized in a 1:7 and 1:1 mole ratio of VF/4-VP, respectively. Spectrophotometric assay of enzyme activity demonstrated that the enzyme was active after its immobilization in the copolymers. Carbon paste electrodes were prepared by mixing the paste with the copolymers. They were tested for the electroregeneration of the enzyme cofactor when dipped in a glucose solution 0.5549 M, at pH 5.1 in acetate buffer or at pH 7.1 in phosphate buffer solution. The studies were conducted using cyclic voltammetry and amperometry. Small catalytic current was observed as a result of the enzymatic reaction. Pellets of 4-VP and VF copolymer quaternized with 1-chloroethanol with the immobilized GOx and insulin incorporated by physical entrapment were made. The release of insulin was monitored measuring its absorbance in 278 nm as function of time. Insulin release was observed with an approximate t R (95%) = 9.18 min.
The Journal of Physical Chemistry A, 1997
... Laura A. Worl, Sharon Gould, Ana Guadalupe, B. Patrick Sullivan, § Jonathan V. Caspar, Ro... more ... Laura A. Worl, Sharon Gould, Ana Guadalupe, B. Patrick Sullivan, § Jonathan V. Caspar, Robert L. Leasure, James R. Gardner, and Thomas J. Meyer*. ... (1) For general reviews see: (a)Balzani, V.; Juris, A.; Venturi, M.; Camagna, S.; Serroni, S. Chem. Rev. 1996, 96, 759. ...
Journal of the American Chemical Society, 1988
Electropolymerized films of [Co(~-terpy)~]*' (v-terpy is 4'-vinyl-2,2':6',2''-terpyridinyl) exhib... more Electropolymerized films of [Co(~-terpy)~]*' (v-terpy is 4'-vinyl-2,2':6',2''-terpyridinyl) exhibit reactivity patterns, especially with regard to ligand exchange, that differ significantly from those exhibited by [ C~(t e r p y)~]~+ in solution. These differences are attributed to the physically constrained environment present in the polymer f h. The charge-transport properties follow the model of Dahms and Ruff and the predicted concentration dependence of the diffusion coefficient. These electropolymerized films are also active in the electrocatalytic reduction of carbon dioxide.
Journal of the American Chemical Society, 1987
4'-Vinyl-2,2':6',2"-terpyridinyl was conveniently prepared from 2-acetylpyridine via a-oxoketene ... more 4'-Vinyl-2,2':6',2"-terpyridinyl was conveniently prepared from 2-acetylpyridine via a-oxoketene dithioacetal methodology, the intermediate 4'-(methylthi0)-2,2':6',2''-terpyridinyl being converted into the corresponding 4'-methyl derivative with methylmagnesium bromide and bis(triphenylphosphino)nickel(II) dichloride followed by generation of the methyl anion with lithium tetramethylpiperidide, reaction of the anion with chloromethyl methyl ether, and introduction of the vinyl group by treatment of the ether with potassium tert-butoxidelTHF. Analogous reactions led to the 4-vinyl-and 6-vinyl isomers by using the appropriate methyl-substituted 2-acetylpyridine except that in these instances desulfurization of the 4'-rnethylthio group with nickel boride was an additional step. These vinyl-substituted ligands formed a variety of readily electropolymerizable simple and mixed-ligand complex monomers with cobalt. ruthenium, and iron with polymerization rates whose magnitude varied with position and number of vinyl substituents. Interest in the use of 2,2'-bipyridinyl as a ligand for transition-metal ions continues unabated,' and, more recently, vinylsubstituted 2,2'-bipyridinyls have been utilized* in polymer formation, in chemically modified electrode studies,3a4 and in solar energy c o n~e r s i o n .~~f The results obtained in these studies strongly suggested that analogous terpyridinyl derivatives would be of special i n t e r e~t .~ However, apart from terpyridinyl itself and several aryl-substituted derivative^,^ very few terpyridinyls and especially vinyl-substituted terpyridinyl ligands have been described in the literature. Their coordination chemistry, electrochemistry and polymerization chemistry remain relatively unexplored areas. In this publication we describe the first syntheses of the title ligands 1-3 and related derivatives, and their application in the preparation and electropolymerization of new simple-and mixed-ligand vi-nyI-"2':6',2''-terpyridinyl coordination complex monomers. 3 v 2 d I Synthesis of Ligands The parent 2,2':2',2"-terpyridinyl ligand, although first isolated6 in 1932, has usually been made by coupling procedures which present obstacles when considered for the synthesis of substituted terpyridinyls. This is especially true for methyl-substituted terpyridinyls which are conceptually precursors to vinyl-substituted terpyridinyls. W e have recently described' the synthesis of 2,2':6',2"-terpyridinyl utilizing a-oxoketene dithioacetal methodology,' and variation of this synthetic route now provides ready access to 4-, 6-, and 4'-methyI-2,2':6',2''-terpyridinyls. 4and 6-Methyl-2,2':6',2"-terpyridinyls were prepared by reaction of 2-acetylpyridine potassium enolate with 1 equiv of carbon disulfide followed by 2 equivs of methyl iodide to give the cor
Journal of Physics: Conference Series, 2013
This report describes the synthesis of [Ru(Fe-Phen)2dppz](PF6)2 (Ru-Fe complex) for a label-free ... more This report describes the synthesis of [Ru(Fe-Phen)2dppz](PF6)2 (Ru-Fe complex) for a label-free approach to detect DNA hybridization. The Ru-Fe complex showed oxidation signals at +608 mV and +1192 mV corresponding to the RuII/III and FeII/III centers, respectively. We used the Ru-Fe complex and the Ferrocene covalently attached to the target to monitor the hybridization event of a 70-mer oligo immobilized in 10.3KD NHS-PS-NHS. The lowest target detectable concentration for the DNA fragment was around 0.4 μM.
Journal of Pharmaceutical and Biomedical Analysis, 1999
A functionalized sol-gel thin film modified glassy carbon electrode has been prepared for the det... more A functionalized sol-gel thin film modified glassy carbon electrode has been prepared for the determination of mercury. The tetrasulfide in the sol-gel matrix has a high affinity for mercury species. The chemically integrated functional groups in the sol-gel precursor ensure a high chemical and mechanical stability of the modified electrodes, and therefore a stable and reproducible analytical performance. By medium exchange anodic stripping voltammetry, this modified electrode allows reliable, low cost and interference-free determination of mercury.
Journal of The Electrochemical Society, 2010
Electrochemical and Spectroscopical Characterization of Ferrocenyl Chalcones. [Journal of The Ele... more Electrochemical and Spectroscopical Characterization of Ferrocenyl Chalcones. [Journal of The Electrochemical Society 157, F104 (2010)]. Rocío A. Cardona, Kenneth Hernández, Laura E. Pedró, Myrna R. Otaño, Ingrid Montes, Ana R. Guadalupe. Abstract. ...
Journal of Biotechnology, 2005
The immobilization of short ss-DNA (18-and 36-mer) and their hybridization were studied at gold a... more The immobilization of short ss-DNA (18-and 36-mer) and their hybridization were studied at gold and glassy carbon substrates modified with low molecular weight (∼12, 18 and 24 kg/mol) polystyrene thin films. Amino-modified DNA was attached to the surface by reaction with succinimide ester groups bound to the polystyrenes. A ferrocene modified DNA target was used to confirm the probe-target hybridization. Atomic force microscopy studies showed significant morphological changes after probe immobilization and hybridization compared to the featureless structure of the polystyrene film. Single-stranded DNA samples had a globular morphology with an average density of 3.8 and 2.2 (×10 11) globules/cm 2 for the 18-and 36-mer, respectively. The formation of a porous structure with a 2.0 and 1.0 (×10 11) average pore density corresponding to the 18-and 36-mer was observed after hybridization. A surface composition analysis was done by X-ray photoelectron spectroscopy to confirm and support the images interpretation. Ferrocene oxidation (+323 mV/18-mer, +367 mV/36-mer, versus Ag/AgCl) proved the presence of ds-DNA at the modified surfaces.
Inorganica Chimica Acta, 2000
Ruthenium polypyridyl complexes containing 2,2′-bipyrimidine, [Ru(bpy)2bpm](PF6)2 (I) and [Ru(phe... more Ruthenium polypyridyl complexes containing 2,2′-bipyrimidine, [Ru(bpy)2bpm](PF6)2 (I) and [Ru(phen)2bpm](PF6)2 (II), were synthesized with high yield and purity. An extensive characterization was carried out using ESMS, UV–Vis, 1H and 13C NMR, electrochemistry and X-ray single crystal diffraction analysis. The experimental results show that the spectroscopic and electrochemical properties of I and II are similar to those of their parent complexes [Ru(bpy)3](PF6)2
Inorganic Chemistry, 1992
complexes: Pd (1.0) < Ni (1.7) < Pt (10.2), determined in methanol.29a Qualitative studies of the... more complexes: Pd (1.0) < Ni (1.7) < Pt (10.2), determined in methanol.29a Qualitative studies of the acidities of group 9 complexes give the following order of decreasing acidities: HRhL4 > HCoL4 > HIrL, (L = CO, PF3, re~pectively).~, Recently, Morris and c o-w o r k e r~~~ reported increasing pK, values of ~~U~~-[MH(~~-H~)(PR~CH~CH~PR~)~]+ (R = Ph, p-CF3C6H4) complexes in the order Fe < Os < Ru. This latter example and that of 3 and 8 (Table I) are the first reported examples of a reversal between complexes of second-and third-row metals. A H H M of Cp*,M, Where M = Ru, Os. The basicities of the C P *~M complexes, 9 and 10, also increase on going down the column from Ru (A H H M =-19.0 kcal mol-') to OS (AHHM =-26.6 kcal mol-'). In terms of equilibrium constants for protonation, 10 is 4 X lo5 times more basic than 9 assuming ASe is the same for both reactions. Qualitative studies of the basicities of Cp2Fe and Cp2Ru reported p r e v i o~s l y~~~.~~ indicate that the Ru complex is more basic than the Fe complex. This suggests that Cp*zFe will also be less basic than Cp*,Ru (9) although we were unable to obtain a A H H M value for Cp*,Fe. In contrast to those of complexes 1,2, and 7 above, the electrochemical potentials (vs SCE in CH2C12)33 of 9 (Ell2 = 0.55 V) and 10 (Ell2 = 0.46 V) decrease as one goes down the group. Basicities of Organonitrogen Complexes, A H H N. The wide range of A H H M values from-19.0 kcal mol-' for complex 4 to-38.7 kcal mol-' for complex 6 demonstrates that substantial changes in metal basicity occur upon changing the metal and/or the chelate ligand. A comparable range of A H H N values was (34) (a) Vidal,
Electrochimica Acta, 1991
Studies on the transport properties of the cationic dyes methylene blue, thionine, safranine and ... more Studies on the transport properties of the cationic dyes methylene blue, thionine, safranine and meldola blue in Nafion-coated electrodes are reported. Diffusion coefficients for the reduced and oxidized forms of the dyes are unusually high (up to 9 × 10−7 cm2s−1 at low dye concentrations in the film and show a dramatic decrease with increasing concentration. The results are interpreted in terms of recently proposed models for transport through Nafion as well as to the formation of dye dimers and/or higher aggregates in the Nafion film. This is demonstrated for methylene blue by spectrophotometric experiments where the dye was incorporated in Nafion films at different concentrations.
Electroanalysis, 2006
We present a carbon paste electrode (CPE) modified using the electron mediator bis(1,10-phenanthr... more We present a carbon paste electrode (CPE) modified using the electron mediator bis(1,10-phenanthroline-5,6-dione) (2,2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-bipyridine)ruthenium(II) ([Ru(phend)(2)bpy](2+)) exchanged into the inorganic layered material zirconium phosphate (ZrP). X-Ray powder diffraction showed that the interlayer distance of ZrP increases upon [Ru(phend)(2)bpy](2+) intercalation from 10.3 Å to 14.2 Å. The UV-vis and IR spectroscopies results showed the characteristic peaks expected for [Ru(phend)(2)bpy](2+). The UV-vis spectrophotometric results indicate that the [Ru(phend)(2)bpy](2+) concentration inside the ZrP layers increased as a function of the loading level. The exchanged [Ru(phend)(2)bpy](2+) exhibited luminescence even at low concentration. Modified CPEs were constructed and analyzed using cyclic voltammetry. The intercalated mediator remained electroactive within the layers (E°&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; = -38.5 mV vs. Ag/AgCl, 3.5 M NaCl) and electrocatalysis of NADH oxidation was observed. The kinetics of the modified CPE shows a Michaelis -Menten behavior. This CPE was used for the oxidation of NADH in the presence of Bakers&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; yeast alcohol dehydrogenase. A calibration plot for ethanol is presented.
Chemistry of Materials, 1999
A Prussian Blue (PB) sol-gel composite thin film was prepared via post-chemical derivatization of... more A Prussian Blue (PB) sol-gel composite thin film was prepared via post-chemical derivatization of a functionalizable sol-gel thin film. Bis[3-(triethoxysilyl)propyl] tetrasulfide (SIS) forms tough and crack-free films by sol-gel process with excellent adhesion on various solid surfaces. The sulfur chain (-S 4-) can be chemically oxidized to sulfonic groups (-SO 3-). After oxidation, PB sol-gel composite thin films were prepared by ion-exchange with ferrous ion followed by complexation with ferricyanide. The PB sol-gel composite thin films were characterized by electrochemistry, spectroscopy, and microscopy. Applications in the development of a potassium ion-selective electrode and an optical pH indicator are demonstrated.
Chemical Communications, 1999
A functional aerogel composed of interconnected silica nanoparticles has been synthesized from a ... more A functional aerogel composed of interconnected silica nanoparticles has been synthesized from a metastable lamellar composite based on a novel type of cooperative interaction between silica and surfactant species.
Bioelectrochemistry and Bioenergetics, 1994
... Bioelectrochemistry and Bioenergetics, 34 (1994) 169-175 Ruthenium complexes as redox mediato... more ... Bioelectrochemistry and Bioenergetics, 34 (1994) 169-175 Ruthenium complexes as redox mediators for malate and lactate dehydrogenases Neftali Rivera, Yanira Colon and Ana R.Guadalupe Department of Chemistry, PO ... 10 SA Wring and JP Hart, Analyst, 117 (1992) 1215. ...
Analytical Letters, 1986
The analytical utility of electrodes modified with functionalized polymer films for the determina... more The analytical utility of electrodes modified with functionalized polymer films for the determination of aromatic amines is demonstrated. The analysis is based on the preconcentration of the protonated amines into a functionalized polymer film that contains styrene sulfonate groups. Good sensitivity and high reproducibility were obtained for concentrations down to 10 M. Aliphatic amines do not interfere in the determination.
Analytical Chemistry, 1985
Analytical Chemistry, 1985
Flgure 7. Primary ion dose dependence for a category C (damage products) fragment ion (Table V): ... more Flgure 7. Primary ion dose dependence for a category C (damage products) fragment ion (Table V): (-) m / e 72 (C6-). tional groups also can be monitored by using the ion microscope and correlated with quantitative XPS data.