This paper surveys materials, design concepts, and applications for electrochromic devices. Speci... more This paper surveys materials, design concepts, and applications for electrochromic devices. Specific discussions are given on the electronic structure and optical properties of crystalline WO3, and of the Li+ dynamics in heavily disordered TiO2.
Polypyrrole is the most widely used conducting polymer to the construction of sensors and biosens... more Polypyrrole is the most widely used conducting polymer to the construction of sensors and biosensors, once their conductivity and electroactivity do not strongly depend on pH of the electrolytic. The aim of the present work remains in the improvement of amperometric ammonia analysis, using a polypyrrole film doped with DBSA anions. This large amphiphilic dopant promotes changes on the polymeric film presenting a more accentuated response and extending the linear response over a wide range of concentrations, when compare with films doped with small inorganic anions, such as chloride. The substituted pyrrole monomers, as N-methyl-pyrrole, was also used with the aim of investigating the role played by acid hydrogen present in polypyrrole. The response of the sensor was followed by EQCM and Raman Spectroscopy experiments as tools to propose to elucidate the mechanism of ammonia detection.
IN ELECTROCATALYSIS, ELECTROCHROMISM AND SECONDARY BATTERIES. The present review paper describes ... more IN ELECTROCATALYSIS, ELECTROCHROMISM AND SECONDARY BATTERIES. The present review paper describes the main features of nickel hydroxide modified electrodes covering its structural and electrochemical behavior and the newest advances promoted by nanostructured architectures. Important aspects such as synthetic procedures and characterization techniques such as X-Ray diffraction, Raman and Infrared spectroscopy, Electronic Microscopy and many others are detailed herein. The most important aspect concerning nickel hydroxide is related to its great versatility covering different fields in electrochemical-based devices such as batteries, electrocatalytic systems and electrochromic electrodes, the fundamental issues of these devices are also commented. Finally, some of the newest advances achieved in each field by the incorporation of nanomaterials will be shown.
We demonstrate, for the first time, the electrosynthesis of uniformly dispersed nickel hydroxide ... more We demonstrate, for the first time, the electrosynthesis of uniformly dispersed nickel hydroxide nanoparticles (NPs) on polycrystalline boron-doped diamond (pBDD). This has been achieved by electrogenerating OHat the pBDD surface in the presence of Ni 2þ to create local conditions near the electrode where highly supersaturated (relative saturation ratio > 10 5 ) nickel hydroxide solutions are generated for short periods of time (approximately seconds). This results in the deposition of nickel hydroxide NPs directly on the electrode surface, as confirmed by X-ray photoelectron spectroscopy. The NPs have a reasonably homogeneous size distribution and are deposited uniformly across the heterogeneous pBDD surface. We show that by simply increasing the electrogeneration time and, hence, increasing both the local concentration of OHand extent of the precipitation reaction, it is possible to increase the size of the NPs. For example, after 1 s, NPs with dimensions of 12 ( 3 nm form, whereas after 15 s, NPs of size ∼39 ( 9 nm result. Longer times result in larger particles, which form aggregated structures. The effect of nickel hydroxide NP size on electrocatalytic activity was investigated by measuring the steady-state current for the oxidation of glucose in alkaline media. For NPs g 25 nm in size, glucose oxidation is close to diffusion-controlled. However, for the smallest NPs produced (∼12 nm) the currents passed suggest kinetic limitations. For glucose at an effective surface coverage of nickel hydroxide of ∼20 nmol cm -2 , equivalent to 15 ng of nickel hydroxide, this functionalized electrode showed a sensitivity of 330 μA mM -1 cm -2 and a limit of detection of 400 nM. The latter represents one of the lowest limits of detection for glucose for nickel hydroxide-based electrodes. The electrocatalytic oxidation properties of this electrode toward methanol and ethanol was also found to be very efficient, yielding very high density currents of ∼1010 A g -1 for 0.5 M ethanol and 990 A g -1 for 0.47 M methanol.
describing the basic aspects and methodologies employed for the construction and analyses of diff... more describing the basic aspects and methodologies employed for the construction and analyses of different modified electrodes. The work presents the classic materials used for the construction of electrochromic electrodes, such as WO 3 and a view on the basic concepts of chromaticity as a useful approach for analyzing colorimetric results. The report also addresses how the incorporation of nanomaterials and the consequent novel modification of electrodes have furthered this area of science, producing electrochromic electrodes with high performance, high efficiency and low response times.
We synthesized a novel series of compounds based on a ruthenium(II) dicarboxybipyridine (dcbpy) c... more We synthesized a novel series of compounds based on a ruthenium(II) dicarboxybipyridine (dcbpy) complex containing chloro and trans-1,4-bis[2-(4-pyridyl)ethenyl]benzene (BPEB) ligands. The binuclear species Na 6 [{[Ru II (dcbpy) 2 Cl} 2 (BPEB)] exhibits an ...
The electrochromic behavior of iron complexes derived from tetra-2-pyridyl-1,4-pyrazine (TPPZ) an... more The electrochromic behavior of iron complexes derived from tetra-2-pyridyl-1,4-pyrazine (TPPZ) and a hexacyanoferrate species in polyelectrolytic multilayer adsorbed films is described for the first time. This complex macromolecule was deposited onto indium-tin oxide (ITO) substrates via self-assembly, and the morphology of the modified electrodes was studied using atomic force microscopy (AFM), which indicated that the hybrid film containing the polyelectrolyte multilayer and the iron complex was highly homogeneous and was approximately 50 nm thick. The modified electrodes exhibited excellent electrochromic behavior with both intense and persistent coloration as well as a chromatic contrast of approximately 70%. In addition, this system achieved high electrochromic efficiency (over 70 cm(2) C(-1) at 630 nm) and a response time that could be measured in milliseconds. The electrode was cycled more than 10(3) times, indicating excellent stability.
Biosensors Based on Gold Nanostructures J. Braz. Chem. Soc. 4 Scheme 1. Representation of the use... more Biosensors Based on Gold Nanostructures J. Braz. Chem. Soc. 4 Scheme 1. Representation of the use of AuNPs in the biosensors.
This paper concerns the deposition of metal alloys formed by nickel and copper on electrode surfa... more This paper concerns the deposition of metal alloys formed by nickel and copper on electrode surface aiming at the development of electrocatalytic systems. Such alloys were formed on platinum electrodes by direct reduction of Ni 2+ and Cu 2+ sulfate salts in different proportions in a simple and straightforward electrochemical treatment. After the deposition, the conversion to the electrocatalytic oxide form was done in alkaline solutions by cyclic voltammograms. The experimental parameters, such as deposition time and the proportion of copper and nickel in the synthetic solution, were investigated toward the catalytic oxidation of glucose. The materials were characterized by electrochemical experiments, infrared and Raman spectroscopies, and X-ray diffraction, showing that the material is not a simple mixture of nickel and copper oxides. The modified electrodes showed remarkable electrocatalytic properties, indicating an interesting application in the sensor and fuel cell development.
The present paper describes the catalytic oxidation of urea performed by nickel hydroxide and nic... more The present paper describes the catalytic oxidation of urea performed by nickel hydroxide and nickel/cobalt hydroxide modified electrodes by using both electrodeposited films and nanoparticles. The incorporation of Co foreign atoms leads to a slight increase in sensitivity besides the shift in redox process, avoiding the oxygen reaction. Nanostructured Ni 80 Co 20 (OH) 2 was synthesized by sonochemical route producing 5 nm diameter particles characterized by high-resolution transmission electron microscopy (HRTEM) being immobilized onto electrode by using the electrostatic Layer-by-layer technique, yielding attractive modified electrodes for sensor development.
Polypyrrole is the most widely used conducting polymer for sensors and biosensors construction on... more Polypyrrole is the most widely used conducting polymer for sensors and biosensors construction once their conductivity and electroactivity do not strongly depend on the pH of the electrolyte. The aim of the present article is the improvement of amperometric ammonia determination, using dodecylbenzenesulfonate (DBSA) doped polypyrrole film. This large amphiphilic dopant promotes changes on the polymeric film leading to a more accentuated current and extending the linear response over a wide concentration range, when compared with films doped with small inorganic anions, such as chloride. The sensor×s response was followed by EQCM and Raman spectroscopy experiments with the aim of elucidating the mechanism of ammonia detection.
IN ELECTROCATALYSIS, ELECTROCHROMISM AND SECONDARY BATTERIES. The present review paper describes ... more IN ELECTROCATALYSIS, ELECTROCHROMISM AND SECONDARY BATTERIES. The present review paper describes the main features of nickel hydroxide modified electrodes covering its structural and electrochemical behavior and the newest advances promoted by nanostructured architectures. Important aspects such as synthetic procedures and characterization techniques such as X-Ray diffraction, Raman and Infrared spectroscopy, Electronic Microscopy and many others are detailed herein. The most important aspect concerning nickel hydroxide is related to its great versatility covering different fields in electrochemical-based devices such as batteries, electrocatalytic systems and electrochromic electrodes, the fundamental issues of these devices are also commented. Finally, some of the newest advances achieved in each field by the incorporation of nanomaterials will be shown.
This paper surveys materials, design concepts, and applications for electrochromic devices. Speci... more This paper surveys materials, design concepts, and applications for electrochromic devices. Specific discussions are given on the electronic structure and optical properties of crystalline WO3, and of the Li+ dynamics in heavily disordered TiO2.
Polypyrrole is the most widely used conducting polymer to the construction of sensors and biosens... more Polypyrrole is the most widely used conducting polymer to the construction of sensors and biosensors, once their conductivity and electroactivity do not strongly depend on pH of the electrolytic. The aim of the present work remains in the improvement of amperometric ammonia analysis, using a polypyrrole film doped with DBSA anions. This large amphiphilic dopant promotes changes on the polymeric film presenting a more accentuated response and extending the linear response over a wide range of concentrations, when compare with films doped with small inorganic anions, such as chloride. The substituted pyrrole monomers, as N-methyl-pyrrole, was also used with the aim of investigating the role played by acid hydrogen present in polypyrrole. The response of the sensor was followed by EQCM and Raman Spectroscopy experiments as tools to propose to elucidate the mechanism of ammonia detection.
IN ELECTROCATALYSIS, ELECTROCHROMISM AND SECONDARY BATTERIES. The present review paper describes ... more IN ELECTROCATALYSIS, ELECTROCHROMISM AND SECONDARY BATTERIES. The present review paper describes the main features of nickel hydroxide modified electrodes covering its structural and electrochemical behavior and the newest advances promoted by nanostructured architectures. Important aspects such as synthetic procedures and characterization techniques such as X-Ray diffraction, Raman and Infrared spectroscopy, Electronic Microscopy and many others are detailed herein. The most important aspect concerning nickel hydroxide is related to its great versatility covering different fields in electrochemical-based devices such as batteries, electrocatalytic systems and electrochromic electrodes, the fundamental issues of these devices are also commented. Finally, some of the newest advances achieved in each field by the incorporation of nanomaterials will be shown.
We demonstrate, for the first time, the electrosynthesis of uniformly dispersed nickel hydroxide ... more We demonstrate, for the first time, the electrosynthesis of uniformly dispersed nickel hydroxide nanoparticles (NPs) on polycrystalline boron-doped diamond (pBDD). This has been achieved by electrogenerating OHat the pBDD surface in the presence of Ni 2þ to create local conditions near the electrode where highly supersaturated (relative saturation ratio > 10 5 ) nickel hydroxide solutions are generated for short periods of time (approximately seconds). This results in the deposition of nickel hydroxide NPs directly on the electrode surface, as confirmed by X-ray photoelectron spectroscopy. The NPs have a reasonably homogeneous size distribution and are deposited uniformly across the heterogeneous pBDD surface. We show that by simply increasing the electrogeneration time and, hence, increasing both the local concentration of OHand extent of the precipitation reaction, it is possible to increase the size of the NPs. For example, after 1 s, NPs with dimensions of 12 ( 3 nm form, whereas after 15 s, NPs of size ∼39 ( 9 nm result. Longer times result in larger particles, which form aggregated structures. The effect of nickel hydroxide NP size on electrocatalytic activity was investigated by measuring the steady-state current for the oxidation of glucose in alkaline media. For NPs g 25 nm in size, glucose oxidation is close to diffusion-controlled. However, for the smallest NPs produced (∼12 nm) the currents passed suggest kinetic limitations. For glucose at an effective surface coverage of nickel hydroxide of ∼20 nmol cm -2 , equivalent to 15 ng of nickel hydroxide, this functionalized electrode showed a sensitivity of 330 μA mM -1 cm -2 and a limit of detection of 400 nM. The latter represents one of the lowest limits of detection for glucose for nickel hydroxide-based electrodes. The electrocatalytic oxidation properties of this electrode toward methanol and ethanol was also found to be very efficient, yielding very high density currents of ∼1010 A g -1 for 0.5 M ethanol and 990 A g -1 for 0.47 M methanol.
describing the basic aspects and methodologies employed for the construction and analyses of diff... more describing the basic aspects and methodologies employed for the construction and analyses of different modified electrodes. The work presents the classic materials used for the construction of electrochromic electrodes, such as WO 3 and a view on the basic concepts of chromaticity as a useful approach for analyzing colorimetric results. The report also addresses how the incorporation of nanomaterials and the consequent novel modification of electrodes have furthered this area of science, producing electrochromic electrodes with high performance, high efficiency and low response times.
We synthesized a novel series of compounds based on a ruthenium(II) dicarboxybipyridine (dcbpy) c... more We synthesized a novel series of compounds based on a ruthenium(II) dicarboxybipyridine (dcbpy) complex containing chloro and trans-1,4-bis[2-(4-pyridyl)ethenyl]benzene (BPEB) ligands. The binuclear species Na 6 [{[Ru II (dcbpy) 2 Cl} 2 (BPEB)] exhibits an ...
The electrochromic behavior of iron complexes derived from tetra-2-pyridyl-1,4-pyrazine (TPPZ) an... more The electrochromic behavior of iron complexes derived from tetra-2-pyridyl-1,4-pyrazine (TPPZ) and a hexacyanoferrate species in polyelectrolytic multilayer adsorbed films is described for the first time. This complex macromolecule was deposited onto indium-tin oxide (ITO) substrates via self-assembly, and the morphology of the modified electrodes was studied using atomic force microscopy (AFM), which indicated that the hybrid film containing the polyelectrolyte multilayer and the iron complex was highly homogeneous and was approximately 50 nm thick. The modified electrodes exhibited excellent electrochromic behavior with both intense and persistent coloration as well as a chromatic contrast of approximately 70%. In addition, this system achieved high electrochromic efficiency (over 70 cm(2) C(-1) at 630 nm) and a response time that could be measured in milliseconds. The electrode was cycled more than 10(3) times, indicating excellent stability.
Biosensors Based on Gold Nanostructures J. Braz. Chem. Soc. 4 Scheme 1. Representation of the use... more Biosensors Based on Gold Nanostructures J. Braz. Chem. Soc. 4 Scheme 1. Representation of the use of AuNPs in the biosensors.
This paper concerns the deposition of metal alloys formed by nickel and copper on electrode surfa... more This paper concerns the deposition of metal alloys formed by nickel and copper on electrode surface aiming at the development of electrocatalytic systems. Such alloys were formed on platinum electrodes by direct reduction of Ni 2+ and Cu 2+ sulfate salts in different proportions in a simple and straightforward electrochemical treatment. After the deposition, the conversion to the electrocatalytic oxide form was done in alkaline solutions by cyclic voltammograms. The experimental parameters, such as deposition time and the proportion of copper and nickel in the synthetic solution, were investigated toward the catalytic oxidation of glucose. The materials were characterized by electrochemical experiments, infrared and Raman spectroscopies, and X-ray diffraction, showing that the material is not a simple mixture of nickel and copper oxides. The modified electrodes showed remarkable electrocatalytic properties, indicating an interesting application in the sensor and fuel cell development.
The present paper describes the catalytic oxidation of urea performed by nickel hydroxide and nic... more The present paper describes the catalytic oxidation of urea performed by nickel hydroxide and nickel/cobalt hydroxide modified electrodes by using both electrodeposited films and nanoparticles. The incorporation of Co foreign atoms leads to a slight increase in sensitivity besides the shift in redox process, avoiding the oxygen reaction. Nanostructured Ni 80 Co 20 (OH) 2 was synthesized by sonochemical route producing 5 nm diameter particles characterized by high-resolution transmission electron microscopy (HRTEM) being immobilized onto electrode by using the electrostatic Layer-by-layer technique, yielding attractive modified electrodes for sensor development.
Polypyrrole is the most widely used conducting polymer for sensors and biosensors construction on... more Polypyrrole is the most widely used conducting polymer for sensors and biosensors construction once their conductivity and electroactivity do not strongly depend on the pH of the electrolyte. The aim of the present article is the improvement of amperometric ammonia determination, using dodecylbenzenesulfonate (DBSA) doped polypyrrole film. This large amphiphilic dopant promotes changes on the polymeric film leading to a more accentuated current and extending the linear response over a wide concentration range, when compared with films doped with small inorganic anions, such as chloride. The sensor×s response was followed by EQCM and Raman spectroscopy experiments with the aim of elucidating the mechanism of ammonia detection.
IN ELECTROCATALYSIS, ELECTROCHROMISM AND SECONDARY BATTERIES. The present review paper describes ... more IN ELECTROCATALYSIS, ELECTROCHROMISM AND SECONDARY BATTERIES. The present review paper describes the main features of nickel hydroxide modified electrodes covering its structural and electrochemical behavior and the newest advances promoted by nanostructured architectures. Important aspects such as synthetic procedures and characterization techniques such as X-Ray diffraction, Raman and Infrared spectroscopy, Electronic Microscopy and many others are detailed herein. The most important aspect concerning nickel hydroxide is related to its great versatility covering different fields in electrochemical-based devices such as batteries, electrocatalytic systems and electrochromic electrodes, the fundamental issues of these devices are also commented. Finally, some of the newest advances achieved in each field by the incorporation of nanomaterials will be shown.
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Papers by Marcio Vidotti