Rodrigo Iost - Academia.edu (original) (raw)

Papers by Rodrigo Iost

Research paper thumbnail of Candida albicans adherence to silver nanoparticle – incorporated denture resin

Research paper thumbnail of Nitrated carbon nanoblisters for High-performance glucose dehydrogenase bioanodes

Biosensors and Bioelectronics, 2015

Recently, many strategies are being explored for efficiently wiring glucose dehydrogenase (GDh) e... more Recently, many strategies are being explored for efficiently wiring glucose dehydrogenase (GDh) enzymes capable of glucose (fuel) oxidation. For instance, the use of GDh NAD(+)-dependent for glucose oxidation is of great interest in biofuel cell technology because the enzyme are unaffected by the presence of molecular oxygen commonly present in electrolyte. Here we present the fabrication of flexible carbon fibers modified with nitrated carbon nanoblisters and their application as high-performance GDh bioanodes. These bioelectrodes could electro-oxidize glucose at -360mV (vs. Ag/AgClsat) in the presence of a molecular oxygen saturated electrolyte with current densities higher than 1.0mAcm(-2) at 0.0V. It is corroborated by open circuit potential, where a potential stabilization occurs at -150mV in a long term stability current-transient experiment. This value is in agreement with the quasi-steady current obtained at very low scan rate (0.1mVs(-1)), where the onset potential for glucose oxidation is -180mV. X-ray photoelectron spectroscopy and scanning electron microscopy revealed that the nitrated blisters and edge-like carbon structures, enabling highly efficient enzyme immobilization and low overpotential for electron transfer, allowing for glucose oxidation with potential values close to the thermodynamic cofactor.

Research paper thumbnail of Langmuir–Blodgett films based on poly(p-phenylene vinylene) and protein-stabilised palladium nanoparticles: Implications in luminescent and conducting properties

Thin Solid Films, 2013

In this paper, poly(p-phenylene vinylene) block copolymers (PPV) were immobilised in stearic acid... more In this paper, poly(p-phenylene vinylene) block copolymers (PPV) were immobilised in stearic acid (HSt) Langmuir-Blodgett (LB) films, and their conducting and luminescent properties were enhanced by the incorporation of palladium nanoparticles stabilised by glucose oxidase (GOx-PdNPs). The nanobiocomposite, based on HSt, PPV, and GOx-PdNPs, was transferred from the air-water interface onto solid supports using the LB technique. The films were characterised by surface pressure-area isotherms, polarisation modulation infrared reflection-absorption spectroscopy, fluorescence spectroscopy, and conductivity measurements. The results indicated that the incorporation of GOx-PdNPs in PPV-HSt LB films enhances the luminescence and conducting properties of the PPV. Based on the higher conductivity and emission obtained with the hybrid LB films and the ability to tune the molecular-level interactions between the film components by changing the experimental conditions, thus allowing for further optimisation, one may envisage applications for these films in optical and electronic devices, such as organic light-emitting diodes.

Research paper thumbnail of Enhancing the Electrochemical and Electronic Performance of CVD-Grown Graphene by Minimizing Trace Metal Impurities

ChemElectroChem, 2014

The presence of unwanted impurities in graphene is known to have a significant impact on its phys... more The presence of unwanted impurities in graphene is known to have a significant impact on its physical and chemical properties. Similar to carbon nanotubes, any trace metals present in graphene will affect the electrocatalytic properties of the material. Here, we show by direct electroanalysis that traces of copper still remain in transferred CVD (chemical vapor deposition)-grown graphene (even after the usual copper etching process) and strongly influence its electrochemical properties. Subsequently, we use a real-time electrochemical etching procedure to remove more than 90 % of the trace metal impurities, with a clear improvement in both the electrochemical and electronic-transport properties of monolayer graphene.

Research paper thumbnail of Glucose Biochip Based on Flexible Carbon Fiber Electrodes: In Vivo Diabetes Evaluation in Rats

Research paper thumbnail of Biofuel Cells: Bioelectrochemistry Applied to the Generation of Green Electricity

Nanoenergy, 2012

ABSTRACT Several studies published in the last decade have pointed to the use of enzymes and micr... more ABSTRACT Several studies published in the last decade have pointed to the use of enzymes and microorganisms in biocatalytic reactions to generate electricity. Enzymes and living organisms can be used in modified electrodes to build the so-called biofuel cells (BFCs). However, a deep understanding of the structure and biocatalytic properties after enzyme immobilization is still lacking because they are immobilized in the solid state and outside of their natural environment. Thus, based on biological molecules and nanostructure materials applied to BFCs, these current topics shall be reviewed here, and prospects for future development in these areas will be presented as well. Moreover, immobilization methodologies and enzyme stability systems that result in BFCs will also be presented. Finally, BFC power density and catalyst support will be widely discussed in this book chapter.

Research paper thumbnail of Nanomaterials for Biosensors and Implantable Biodevices

Nanobioelectrochemistry, 2012

ABSTRACT The study of biological recognition elements and their specific functions has enabled th... more ABSTRACT The study of biological recognition elements and their specific functions has enabled the development of a new class of electrochemical modified electrodes called biosensors. Since the development of the first biosensor almost 50 years ago, biosensors technology have experienced a considerable growth in terms of applicability and complexity of devices. In the last decade this growth has been accelerated due the utilization of electrodes-modified nanostructured materials in order to increase the power detection of specific molecules. Other important feature can be associated with the development of new methodologies for biomolecules immobilization. This includes the utilization of several biological molecules such as enzymes, nucleotides, antigens, DNA, aminoacids and many others for biosensing. Moreover, the utilization of these biological molecules in conjunction with nanostructured materials opens the possibility to develop several types of biosensors such as nanostructured and miniaturized devices and implantable biosensors for real time monitoring. Based on recent strategies focused on nanomaterials for electrochemical biosensors development, these topics has presented recent methodologies and tools used until nowadays and the prospects for the future in the area.

Research paper thumbnail of Molecular interactions and structure of a supramolecular arrangement of glucose oxidase and palladium nanoparticles

Physical Chemistry Chemical Physics, 2011

This paper presents studies about the molecular interactions and redox processes involved in the ... more This paper presents studies about the molecular interactions and redox processes involved in the formation of palladium nanoparticles associated to glucose oxidase (GOx-PdNPs) in a supramolecular arrangement. The synthesis occurs in two steps, the Pd reduction and the formation of the 80 nm sized supramolecular aggregates containing multiples units of GOx associated to 3.5 nm sized PdNPs. During synthesis, GOx molecules interact with Pd salt leading to metal ion and FAD reduction probably via the thiol group of the cysteine 521 residue. For the growing of PdNPs, formic acid was necessary as a co-adjuvant reducing agent. Besides the contribution for the redox processes, GOx is also necessary for the NP stability preventing the formation of precipitates resulted from uncontrolled growing of NPs Cyclic voltammetry of the GOx-PdNPs demonstrated electroactivity of the bionanocomposite immobilized on ITO (indium-tin oxide) electrode surface and also the NP is partially blocked due to strong interaction GOx and the surface of PdNPs. Vibrational spectroscopy (FTIR) showed that significant structural changes occurred in GOx after the association to PdNP. These mechanistics and structural studies can contribute for modulation of bionanocomposites properties.

Research paper thumbnail of Evidence of short-range electron transfer of a redox enzyme on graphene oxide electrodes

Physical Chemistry Chemical Physics, 2014

PAPER Frank N. Crespilho et al. Evidence of short-range electron transfer of a redox enzyme on gr... more PAPER Frank N. Crespilho et al. Evidence of short-range electron transfer of a redox enzyme on graphene oxide electrodes Direct electron transfer (DET) between redox enzymes and electrode surfaces is of growing interest and an important strategy in the development of biofuel cells and biosensors. Among the nanomaterials utilized at electrode/enzyme interfaces to enhance the electronic communication, graphene oxide (GO)

Research paper thumbnail of Monolayer Collapse Regulating Process of Adsorption−Desorption of Palladium Nanoparticles at Fatty Acid Monolayers at the Air−Water Interface

Langmuir, 2011

In this paper, we investigate the affinity of palladium nanoparticles, stabilized with glucose ox... more In this paper, we investigate the affinity of palladium nanoparticles, stabilized with glucose oxidase, for fatty acid monolayers at the air-water interface, exploiting the interaction between a planar system and spheroids coming from the aqueous subphase. A decrease of the monolayer collapse pressure in the second cycle of interface compression proved that the presence of the nanoparticles causes destabilization of the monolayer in a mechanism driven by the interpenetration of the enzyme into the bilayer/multilayer structure formed during collapse, which is not immediately reversible after monolayer expansion. Surface pressure and surface potential-area isotherms, as well as infrared spectroscopy [polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS)] and deposition onto solid plates as Langmuir-Blodgett (LB) films, were employed to construct a model in which the nanoparticle has a high affinity for the hydrophobic core of the structure formed after collapse, which provides a slow desorption rate from the interface after monolayer decompression. This may have important consequences on the interaction between the metallic particles and fatty acid monolayers, which implies the regulation of the multifunctional properties of the hybrid material.

Research paper thumbnail of Effects of Self-Assembled Materials Prepared from V 2 O 5 for Lithium Ion Electroinsertion

Langmuir, 2011

Advances in materials science have been very important for the development of rechargeable lithiu... more Advances in materials science have been very important for the development of rechargeable lithium batteries and electrochromic devices. Some transition metal oxides can be employed as host matrices for the electro-insertion of lithium ions, according to the following equation

Research paper thumbnail of An intravenous implantable glucose/dioxygen biofuel cell with modified flexible carbon fiber electrodes

Lab on a Chip, 2013

An intravenous implantable glucose/dioxygen hybrid enzyme-Pt micro-biofuel cell (BFC) was investi... more An intravenous implantable glucose/dioxygen hybrid enzyme-Pt micro-biofuel cell (BFC) was investigated.

Research paper thumbnail of Highly Stable Magnetite Modified with Chitosan, Ferrocene and Enzyme for Application in Magneto-Switchable Bioelectrocatalysis

Journal of the Brazilian Chemical Society, 2013

O direcionamento por campo magnético tem sido aplicado em Bioeletroquímica, principalmente com in... more O direcionamento por campo magnético tem sido aplicado em Bioeletroquímica, principalmente com intuito de transportar enzimas ou mediadores redox imobilizados em partículas de magnetita (Fe 3 O 4 ) para a superfície de eletrodos, proporcionando o controle comutável das correntes faradaicas provenientes da biocatálise. Neste trabalho, relata-se um avanço no controle magnético de reações bioeletroquímicas por meio da construção de um sistema que contém simultaneamente partículas magnéticas (para transporte controlado), enzima redox (para biocatálise) e um mediador redox (para mediação da transferência eletrônica). Para isso, sintetizou-se um novo material que consiste em partículas de Fe 3 O 4 modificadas com ferroceno insolúvel (Fc) e quitosana (Chi) entrecruzada com glicose oxidase (GOx). Quando esse material foi utilizado em suspensão em estudos eletroquímicos, observou-se um aumento de 70% da corrente catalítica de oxidação de glicose quando um campo de 0,24 T foi aplicado perpendicularmente ao plano do eletrodo. Esta é a primeira vez que um controle de processos bioeletrocatalíticos foi relatado utilizando enzima, mediador e magnetita em um sistema único controlado por campo magnético.

Research paper thumbnail of Flexible Carbon Cloth Electrode Modified by Hollow Core-Mesoporous Shell Carbon as a Novel Efficient Bio-Anode for Biofuel Cell

Journal of Nanoscience and Nanotechnology, 2012

A new approach is described to produce an efficient electrode material for biofuel cells using fl... more A new approach is described to produce an efficient electrode material for biofuel cells using flexible carbon cloth (FCC) and hollow core-mesoporous shell carbon (HCMSC) nanospheres as bioanode materials. The bio-electrochemical activity of glucose oxidase (GOx) enzyme adsorbed on this bio-anode was evaluated, with the maximum anodic current density varying from 80 A cm −2 to 180 A cm −2 for glucose concentrations up to 5.0 mmol L −1 for the FCC modified electrode with HCMSCs. The open circuit cell voltage was E 0 = 380 mV, and the catalytic electro-oxidation current of glucose reached 0.1 mA cm −2 at 0.0 V versus Ag/AgCl. This new system employing HCMSCbased FCC is promising toward novel bio-anodes for biofuel cells using glucose as a fuel.

Research paper thumbnail of Diffusion Mechanisms in Nanoelectrodes: Evaluating the Edge Effect

Electrochimica Acta, 2014

Keywords: diffusion mechanism nanoelectrodes charge transfer edge effect.

Research paper thumbnail of Layer-by-layer self-assembly and electrochemistry: Applications in biosensing and bioelectronics

Biosensors and Bioelectronics, 2012

This paper provides an overview of different nanostructured architectures utilised in electrochem... more This paper provides an overview of different nanostructured architectures utilised in electrochemical devices and their application in biosensing and bioelectronics. Emphasis is placed on the fabrication of nanostructured films based on a layer-by-layer (LBL) films approach. We discuss the theory and the mechanism of charge transfer in polyelectrolyte multilayer films (PEM), as well as between biomolecules and redox centres, for the development of more sensitive and selective biosensors. Further, this paper presents an overview of topics involving the interaction between nanostructured materials, including metallic nanoparticles and carbon materials, and their effects on the preservation of the activity of biological molecules immobilised on electrode surfaces. This paper also presents examples of biological molecules utilised in film fabrication, such as DNA, several kinds of proteins, and oligonucleotides, and of the role of molecular interaction in biosensing performance. Towards the utilisation of LBL films, examples of several architectures and different electrochemical approaches demonstrate the potential of nanostructured LBL films for several applications that include the diagnosis and monitoring of diseases. Our main aim in this review is to survey what can assist researchers by presenting various approaches currently used in the field of bioelectrochemistry utilising supramolecular architectures based on an LBL approach for application in electrochemical biosensing.

Research paper thumbnail of Enzyme immobilization on Ag nanoparticles/polyaniline nanocomposites

Biosensors and Bioelectronics, 2009

We show a simple strategy to obtain an efficient enzymatic bioelectrochemical device, in which ur... more We show a simple strategy to obtain an efficient enzymatic bioelectrochemical device, in which urease was immobilized on electroactive nanostructured membranes (ENMs) made with polyaniline and silver nanoparticles (AgNP) stabilized in polyvinyl alcohol (PAni/PVA-AgNP). Fabrication of the modified electrodes comprised the chemical deposition of polyaniline followed by drop-coating of PVA-AgNP and urease, resulting in a final ITO/PAni/PVA-AgNP/urease electrode configuration. For comparison, the electrochemical performance of ITO/PAni/urease electrodes (without Ag nanoparticles) was also studied. The performance of the modified electrodes toward urea hydrolysis was investigated via amperometric measurements, revealing a fast increase in cathodic current with a well-defined peak upon addition of urea to the electrolytic solution. The cathodic currents for the ITO/PAni/PVA-AgNP/urease electrodes were significantly higher than for the ITO/PAni/urease electrodes. The friendly environment provided by the ITO/PAni/PVA-AgNP electrode to the immobilized enzyme promoted efficient catalytic conversion of urea into ammonium and bicarbonate ions. Using the Michaelis-Menten kinetics equation, a K M app of 2.7 mmol L −1 was obtained, indicating that the electrode architecture employed may be advantageous for fabrication of enzymatic devices with improved biocatalytic properties.

Research paper thumbnail of Strategies of nano-manipulation for application in electrochemical biosensors

Manipulation techniques of materials at nanoscale level have been pointed in the last decades as ... more Manipulation techniques of materials at nanoscale level have been pointed in the last decades as a promising tool to develop a new class of modified electrodes applicable in biosensors. Also, the high control of material properties is crucial to detect single events at molecular and atomic level. For instance, nanostructured thin films obtained by Langmuir-Blodgett (LB) and Layer-by-layer (LbL) techniques has been reported as an interesting approach to obtain more selective and sensitive modified electrodes and in addition to nanostructured materials are promising strategies for the fabrication of electrochemical biodevices. Thus, our main focus in this review paper is to show an overview on recent trends in the utilization of manipulation techniques applied to the development of electrochemical biosensors. Emphasis will be given in the utilization of different techniques utilized on the modification of electrodes to enhance electrochemical biosensing performance of enzyme-, protein-and DNA-based biosensors and nano-based electrochemical biosensors for diagnosis.

Research paper thumbnail of Recent advances in nano-based electrochemical biosensors: application in diagnosis and monitoring of diseases

Frontiers in bioscience (Elite edition)

Based on biological molecules combined with nanostructured components, the news generations of el... more Based on biological molecules combined with nanostructured components, the news generations of electrochemical biosensors can employ different transducers (potentiometric, amperometric and impedimetric) converting the chemical information into a measurable amperometric signal. Following this contemporary theme, our main focus in this review is to discuss different methodologies for application in biosensing, whose signal transduction is based on electrochemical principles. We apply a discussion on recent trends involving different nanostructured materials, but without daring to contemplate all nanomaterials incessantly cited in literature, which leads us to believe that this moment is an unprecedented revolution in the preparation of electrochemical biodevices. Besides, some structures of bio-nano interface and different electrochemical biosensors involved in diagnosis systems are also discussed. We outline in several parts of the report how nanoscience technologies are emerging in ...

Research paper thumbnail of Candida albicans adherence to silver nanoparticle – incorporated denture resin

Research paper thumbnail of Nitrated carbon nanoblisters for High-performance glucose dehydrogenase bioanodes

Biosensors and Bioelectronics, 2015

Recently, many strategies are being explored for efficiently wiring glucose dehydrogenase (GDh) e... more Recently, many strategies are being explored for efficiently wiring glucose dehydrogenase (GDh) enzymes capable of glucose (fuel) oxidation. For instance, the use of GDh NAD(+)-dependent for glucose oxidation is of great interest in biofuel cell technology because the enzyme are unaffected by the presence of molecular oxygen commonly present in electrolyte. Here we present the fabrication of flexible carbon fibers modified with nitrated carbon nanoblisters and their application as high-performance GDh bioanodes. These bioelectrodes could electro-oxidize glucose at -360mV (vs. Ag/AgClsat) in the presence of a molecular oxygen saturated electrolyte with current densities higher than 1.0mAcm(-2) at 0.0V. It is corroborated by open circuit potential, where a potential stabilization occurs at -150mV in a long term stability current-transient experiment. This value is in agreement with the quasi-steady current obtained at very low scan rate (0.1mVs(-1)), where the onset potential for glucose oxidation is -180mV. X-ray photoelectron spectroscopy and scanning electron microscopy revealed that the nitrated blisters and edge-like carbon structures, enabling highly efficient enzyme immobilization and low overpotential for electron transfer, allowing for glucose oxidation with potential values close to the thermodynamic cofactor.

Research paper thumbnail of Langmuir–Blodgett films based on poly(p-phenylene vinylene) and protein-stabilised palladium nanoparticles: Implications in luminescent and conducting properties

Thin Solid Films, 2013

In this paper, poly(p-phenylene vinylene) block copolymers (PPV) were immobilised in stearic acid... more In this paper, poly(p-phenylene vinylene) block copolymers (PPV) were immobilised in stearic acid (HSt) Langmuir-Blodgett (LB) films, and their conducting and luminescent properties were enhanced by the incorporation of palladium nanoparticles stabilised by glucose oxidase (GOx-PdNPs). The nanobiocomposite, based on HSt, PPV, and GOx-PdNPs, was transferred from the air-water interface onto solid supports using the LB technique. The films were characterised by surface pressure-area isotherms, polarisation modulation infrared reflection-absorption spectroscopy, fluorescence spectroscopy, and conductivity measurements. The results indicated that the incorporation of GOx-PdNPs in PPV-HSt LB films enhances the luminescence and conducting properties of the PPV. Based on the higher conductivity and emission obtained with the hybrid LB films and the ability to tune the molecular-level interactions between the film components by changing the experimental conditions, thus allowing for further optimisation, one may envisage applications for these films in optical and electronic devices, such as organic light-emitting diodes.

Research paper thumbnail of Enhancing the Electrochemical and Electronic Performance of CVD-Grown Graphene by Minimizing Trace Metal Impurities

ChemElectroChem, 2014

The presence of unwanted impurities in graphene is known to have a significant impact on its phys... more The presence of unwanted impurities in graphene is known to have a significant impact on its physical and chemical properties. Similar to carbon nanotubes, any trace metals present in graphene will affect the electrocatalytic properties of the material. Here, we show by direct electroanalysis that traces of copper still remain in transferred CVD (chemical vapor deposition)-grown graphene (even after the usual copper etching process) and strongly influence its electrochemical properties. Subsequently, we use a real-time electrochemical etching procedure to remove more than 90 % of the trace metal impurities, with a clear improvement in both the electrochemical and electronic-transport properties of monolayer graphene.

Research paper thumbnail of Glucose Biochip Based on Flexible Carbon Fiber Electrodes: In Vivo Diabetes Evaluation in Rats

Research paper thumbnail of Biofuel Cells: Bioelectrochemistry Applied to the Generation of Green Electricity

Nanoenergy, 2012

ABSTRACT Several studies published in the last decade have pointed to the use of enzymes and micr... more ABSTRACT Several studies published in the last decade have pointed to the use of enzymes and microorganisms in biocatalytic reactions to generate electricity. Enzymes and living organisms can be used in modified electrodes to build the so-called biofuel cells (BFCs). However, a deep understanding of the structure and biocatalytic properties after enzyme immobilization is still lacking because they are immobilized in the solid state and outside of their natural environment. Thus, based on biological molecules and nanostructure materials applied to BFCs, these current topics shall be reviewed here, and prospects for future development in these areas will be presented as well. Moreover, immobilization methodologies and enzyme stability systems that result in BFCs will also be presented. Finally, BFC power density and catalyst support will be widely discussed in this book chapter.

Research paper thumbnail of Nanomaterials for Biosensors and Implantable Biodevices

Nanobioelectrochemistry, 2012

ABSTRACT The study of biological recognition elements and their specific functions has enabled th... more ABSTRACT The study of biological recognition elements and their specific functions has enabled the development of a new class of electrochemical modified electrodes called biosensors. Since the development of the first biosensor almost 50 years ago, biosensors technology have experienced a considerable growth in terms of applicability and complexity of devices. In the last decade this growth has been accelerated due the utilization of electrodes-modified nanostructured materials in order to increase the power detection of specific molecules. Other important feature can be associated with the development of new methodologies for biomolecules immobilization. This includes the utilization of several biological molecules such as enzymes, nucleotides, antigens, DNA, aminoacids and many others for biosensing. Moreover, the utilization of these biological molecules in conjunction with nanostructured materials opens the possibility to develop several types of biosensors such as nanostructured and miniaturized devices and implantable biosensors for real time monitoring. Based on recent strategies focused on nanomaterials for electrochemical biosensors development, these topics has presented recent methodologies and tools used until nowadays and the prospects for the future in the area.

Research paper thumbnail of Molecular interactions and structure of a supramolecular arrangement of glucose oxidase and palladium nanoparticles

Physical Chemistry Chemical Physics, 2011

This paper presents studies about the molecular interactions and redox processes involved in the ... more This paper presents studies about the molecular interactions and redox processes involved in the formation of palladium nanoparticles associated to glucose oxidase (GOx-PdNPs) in a supramolecular arrangement. The synthesis occurs in two steps, the Pd reduction and the formation of the 80 nm sized supramolecular aggregates containing multiples units of GOx associated to 3.5 nm sized PdNPs. During synthesis, GOx molecules interact with Pd salt leading to metal ion and FAD reduction probably via the thiol group of the cysteine 521 residue. For the growing of PdNPs, formic acid was necessary as a co-adjuvant reducing agent. Besides the contribution for the redox processes, GOx is also necessary for the NP stability preventing the formation of precipitates resulted from uncontrolled growing of NPs Cyclic voltammetry of the GOx-PdNPs demonstrated electroactivity of the bionanocomposite immobilized on ITO (indium-tin oxide) electrode surface and also the NP is partially blocked due to strong interaction GOx and the surface of PdNPs. Vibrational spectroscopy (FTIR) showed that significant structural changes occurred in GOx after the association to PdNP. These mechanistics and structural studies can contribute for modulation of bionanocomposites properties.

Research paper thumbnail of Evidence of short-range electron transfer of a redox enzyme on graphene oxide electrodes

Physical Chemistry Chemical Physics, 2014

PAPER Frank N. Crespilho et al. Evidence of short-range electron transfer of a redox enzyme on gr... more PAPER Frank N. Crespilho et al. Evidence of short-range electron transfer of a redox enzyme on graphene oxide electrodes Direct electron transfer (DET) between redox enzymes and electrode surfaces is of growing interest and an important strategy in the development of biofuel cells and biosensors. Among the nanomaterials utilized at electrode/enzyme interfaces to enhance the electronic communication, graphene oxide (GO)

Research paper thumbnail of Monolayer Collapse Regulating Process of Adsorption−Desorption of Palladium Nanoparticles at Fatty Acid Monolayers at the Air−Water Interface

Langmuir, 2011

In this paper, we investigate the affinity of palladium nanoparticles, stabilized with glucose ox... more In this paper, we investigate the affinity of palladium nanoparticles, stabilized with glucose oxidase, for fatty acid monolayers at the air-water interface, exploiting the interaction between a planar system and spheroids coming from the aqueous subphase. A decrease of the monolayer collapse pressure in the second cycle of interface compression proved that the presence of the nanoparticles causes destabilization of the monolayer in a mechanism driven by the interpenetration of the enzyme into the bilayer/multilayer structure formed during collapse, which is not immediately reversible after monolayer expansion. Surface pressure and surface potential-area isotherms, as well as infrared spectroscopy [polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS)] and deposition onto solid plates as Langmuir-Blodgett (LB) films, were employed to construct a model in which the nanoparticle has a high affinity for the hydrophobic core of the structure formed after collapse, which provides a slow desorption rate from the interface after monolayer decompression. This may have important consequences on the interaction between the metallic particles and fatty acid monolayers, which implies the regulation of the multifunctional properties of the hybrid material.

Research paper thumbnail of Effects of Self-Assembled Materials Prepared from V 2 O 5 for Lithium Ion Electroinsertion

Langmuir, 2011

Advances in materials science have been very important for the development of rechargeable lithiu... more Advances in materials science have been very important for the development of rechargeable lithium batteries and electrochromic devices. Some transition metal oxides can be employed as host matrices for the electro-insertion of lithium ions, according to the following equation

Research paper thumbnail of An intravenous implantable glucose/dioxygen biofuel cell with modified flexible carbon fiber electrodes

Lab on a Chip, 2013

An intravenous implantable glucose/dioxygen hybrid enzyme-Pt micro-biofuel cell (BFC) was investi... more An intravenous implantable glucose/dioxygen hybrid enzyme-Pt micro-biofuel cell (BFC) was investigated.

Research paper thumbnail of Highly Stable Magnetite Modified with Chitosan, Ferrocene and Enzyme for Application in Magneto-Switchable Bioelectrocatalysis

Journal of the Brazilian Chemical Society, 2013

O direcionamento por campo magnético tem sido aplicado em Bioeletroquímica, principalmente com in... more O direcionamento por campo magnético tem sido aplicado em Bioeletroquímica, principalmente com intuito de transportar enzimas ou mediadores redox imobilizados em partículas de magnetita (Fe 3 O 4 ) para a superfície de eletrodos, proporcionando o controle comutável das correntes faradaicas provenientes da biocatálise. Neste trabalho, relata-se um avanço no controle magnético de reações bioeletroquímicas por meio da construção de um sistema que contém simultaneamente partículas magnéticas (para transporte controlado), enzima redox (para biocatálise) e um mediador redox (para mediação da transferência eletrônica). Para isso, sintetizou-se um novo material que consiste em partículas de Fe 3 O 4 modificadas com ferroceno insolúvel (Fc) e quitosana (Chi) entrecruzada com glicose oxidase (GOx). Quando esse material foi utilizado em suspensão em estudos eletroquímicos, observou-se um aumento de 70% da corrente catalítica de oxidação de glicose quando um campo de 0,24 T foi aplicado perpendicularmente ao plano do eletrodo. Esta é a primeira vez que um controle de processos bioeletrocatalíticos foi relatado utilizando enzima, mediador e magnetita em um sistema único controlado por campo magnético.

Research paper thumbnail of Flexible Carbon Cloth Electrode Modified by Hollow Core-Mesoporous Shell Carbon as a Novel Efficient Bio-Anode for Biofuel Cell

Journal of Nanoscience and Nanotechnology, 2012

A new approach is described to produce an efficient electrode material for biofuel cells using fl... more A new approach is described to produce an efficient electrode material for biofuel cells using flexible carbon cloth (FCC) and hollow core-mesoporous shell carbon (HCMSC) nanospheres as bioanode materials. The bio-electrochemical activity of glucose oxidase (GOx) enzyme adsorbed on this bio-anode was evaluated, with the maximum anodic current density varying from 80 A cm −2 to 180 A cm −2 for glucose concentrations up to 5.0 mmol L −1 for the FCC modified electrode with HCMSCs. The open circuit cell voltage was E 0 = 380 mV, and the catalytic electro-oxidation current of glucose reached 0.1 mA cm −2 at 0.0 V versus Ag/AgCl. This new system employing HCMSCbased FCC is promising toward novel bio-anodes for biofuel cells using glucose as a fuel.

Research paper thumbnail of Diffusion Mechanisms in Nanoelectrodes: Evaluating the Edge Effect

Electrochimica Acta, 2014

Keywords: diffusion mechanism nanoelectrodes charge transfer edge effect.

Research paper thumbnail of Layer-by-layer self-assembly and electrochemistry: Applications in biosensing and bioelectronics

Biosensors and Bioelectronics, 2012

This paper provides an overview of different nanostructured architectures utilised in electrochem... more This paper provides an overview of different nanostructured architectures utilised in electrochemical devices and their application in biosensing and bioelectronics. Emphasis is placed on the fabrication of nanostructured films based on a layer-by-layer (LBL) films approach. We discuss the theory and the mechanism of charge transfer in polyelectrolyte multilayer films (PEM), as well as between biomolecules and redox centres, for the development of more sensitive and selective biosensors. Further, this paper presents an overview of topics involving the interaction between nanostructured materials, including metallic nanoparticles and carbon materials, and their effects on the preservation of the activity of biological molecules immobilised on electrode surfaces. This paper also presents examples of biological molecules utilised in film fabrication, such as DNA, several kinds of proteins, and oligonucleotides, and of the role of molecular interaction in biosensing performance. Towards the utilisation of LBL films, examples of several architectures and different electrochemical approaches demonstrate the potential of nanostructured LBL films for several applications that include the diagnosis and monitoring of diseases. Our main aim in this review is to survey what can assist researchers by presenting various approaches currently used in the field of bioelectrochemistry utilising supramolecular architectures based on an LBL approach for application in electrochemical biosensing.

Research paper thumbnail of Enzyme immobilization on Ag nanoparticles/polyaniline nanocomposites

Biosensors and Bioelectronics, 2009

We show a simple strategy to obtain an efficient enzymatic bioelectrochemical device, in which ur... more We show a simple strategy to obtain an efficient enzymatic bioelectrochemical device, in which urease was immobilized on electroactive nanostructured membranes (ENMs) made with polyaniline and silver nanoparticles (AgNP) stabilized in polyvinyl alcohol (PAni/PVA-AgNP). Fabrication of the modified electrodes comprised the chemical deposition of polyaniline followed by drop-coating of PVA-AgNP and urease, resulting in a final ITO/PAni/PVA-AgNP/urease electrode configuration. For comparison, the electrochemical performance of ITO/PAni/urease electrodes (without Ag nanoparticles) was also studied. The performance of the modified electrodes toward urea hydrolysis was investigated via amperometric measurements, revealing a fast increase in cathodic current with a well-defined peak upon addition of urea to the electrolytic solution. The cathodic currents for the ITO/PAni/PVA-AgNP/urease electrodes were significantly higher than for the ITO/PAni/urease electrodes. The friendly environment provided by the ITO/PAni/PVA-AgNP electrode to the immobilized enzyme promoted efficient catalytic conversion of urea into ammonium and bicarbonate ions. Using the Michaelis-Menten kinetics equation, a K M app of 2.7 mmol L −1 was obtained, indicating that the electrode architecture employed may be advantageous for fabrication of enzymatic devices with improved biocatalytic properties.

Research paper thumbnail of Strategies of nano-manipulation for application in electrochemical biosensors

Manipulation techniques of materials at nanoscale level have been pointed in the last decades as ... more Manipulation techniques of materials at nanoscale level have been pointed in the last decades as a promising tool to develop a new class of modified electrodes applicable in biosensors. Also, the high control of material properties is crucial to detect single events at molecular and atomic level. For instance, nanostructured thin films obtained by Langmuir-Blodgett (LB) and Layer-by-layer (LbL) techniques has been reported as an interesting approach to obtain more selective and sensitive modified electrodes and in addition to nanostructured materials are promising strategies for the fabrication of electrochemical biodevices. Thus, our main focus in this review paper is to show an overview on recent trends in the utilization of manipulation techniques applied to the development of electrochemical biosensors. Emphasis will be given in the utilization of different techniques utilized on the modification of electrodes to enhance electrochemical biosensing performance of enzyme-, protein-and DNA-based biosensors and nano-based electrochemical biosensors for diagnosis.

Research paper thumbnail of Recent advances in nano-based electrochemical biosensors: application in diagnosis and monitoring of diseases

Frontiers in bioscience (Elite edition)

Based on biological molecules combined with nanostructured components, the news generations of el... more Based on biological molecules combined with nanostructured components, the news generations of electrochemical biosensors can employ different transducers (potentiometric, amperometric and impedimetric) converting the chemical information into a measurable amperometric signal. Following this contemporary theme, our main focus in this review is to discuss different methodologies for application in biosensing, whose signal transduction is based on electrochemical principles. We apply a discussion on recent trends involving different nanostructured materials, but without daring to contemplate all nanomaterials incessantly cited in literature, which leads us to believe that this moment is an unprecedented revolution in the preparation of electrochemical biodevices. Besides, some structures of bio-nano interface and different electrochemical biosensors involved in diagnosis systems are also discussed. We outline in several parts of the report how nanoscience technologies are emerging in ...