Papers by Vinicius Gonçales
In this work, polystyrene spheres were employed as templates to prepare polypyrrole inverse opal ... more In this work, polystyrene spheres were employed as templates to prepare polypyrrole inverse opal filmson the surface of platinum electrodes. The facilitated access for both outer and inner active sites, aswell as the exhibited electrochemical behaviour, turned macroporous PPy into a material more suitablethan bulk PPy for electrochemically determining ammonium in samples. However, independently ofemploying bulk or macroporous polypyrrole, the loss of conductivity suffered by the polymer duringthe mediating process led to an irreversible increase of the electrical resistance that compromised thesensor’s analytical performance. Here, it is shown that the incorporation of magnetite nanoparticlesinto the walls of the polypyrrole inverse opal films generated a protective effect. This increased thestability of the macroporous mediator due to the preservation of the polaron state, as shown by Ramanspectroscopy experiments. Finally, the interaction between polypyrrole and magnetite also positivelyaffected the observed analytical parameters, improving linear range, detection limit and sensitivity ofthe ammonium sensor.
Electrochimica Acta, 2015
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Electrochimica Acta, 2015
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Journal of the Brazilian Chemical Society, 2009
Partículas coloidais têm sido empregadas na síntese dirigida por molde de diversos materiais, tai... more Partículas coloidais têm sido empregadas na síntese dirigida por molde de diversos materiais, tais como semicondutores, metais e ligas. Esse método permite um controle da espessura do material resultante através da escolha adequada da carga aplicada no sistema e é possível produzir materiais densamente depositados, sem rachaduras. Esses materiais são fidedignos à estrutura do molde e, devido às amplas áreas superficiais obtidas, são muito interessantes em aplicações eletroquímicas. Neste trabalho, a distribuição de um molde de poliestireno monodisperso foi realizada sobre substratos de ouro, platina e carbono vítreo com o intuito de exemplificar a eletrodeposição de um óxido, um polímero condutor e um material híbrido orgânico-inorgânico, com aplicações em supercapacitores e sensores. Os desempenhos dos eletrodos nanoestruturados foram comparados com os análogos massivos e os resultados obtidos são descritos.
Journal of Solid State Electrochemistry, 2010
The present work describes the synthesis of platinum nanoparticles followed by their electrophore... more The present work describes the synthesis of platinum nanoparticles followed by their electrophoretic deposition onto transparent fluorine-doped tin oxide electrodes. The nano-Pt-modified electrodes were characterized by voltammetric studies in acidic solutions showing a great electrocatalytic behavior towards H + reduction being very interesting for fuel cell applications. Morphological characterization was performed by atomic force microscopy on different modified electrodes showing a very rough surface which can be tuned by means of time of deposition. Also, nickel hydroxide thin films were galvanostatically grown onto these electrodes showing an interesting electrochemical behavior as sharper peaks, indicating a faster ionic exchange from the electrolyte to the film.
Journal of The Electrochemical Society, 2008
ABSTRACT Prussian Blue has been introduced as a mediator to achieve stable, sensitive, reproducib... more ABSTRACT Prussian Blue has been introduced as a mediator to achieve stable, sensitive, reproducible, and interference-free biosensors. However, Na +, Li+, H+, and all group II cations are capable to block the activity of Prussian Blue and, because Na+ can be found in most human fluids, Prussian Blue analogs have already been developed to overcome this problem. These analogs, such as copper hexacyanoferrate, have also been introduced in a conducting polypyrrole matrix to create hybrid materials (copper hexacyanoferrate/polypyrrole, CuHCNFe/Ppy) with improved mechanical and electrochemical characteristics. Nowadays, the challenges in amperometric enzymatic biosensors consist of improving the enzyme immobilization and in making the chemical signal transduction more efficient. The incorporation of nanostructured materials in biosensors can optimize both steps and a nanostructured hybrid CuHCNFe/Ppy mediator has been developed using a template of colloidal polystyrene particles. The nanostructured material has achieved sensitivities 7.6 times higher than the bulk film during H 2O2 detection and it has also presented better results in other analytical parameters such as time response and detection limit. Besides, the nanostructured mediator was successfully applied at glucose biosensing in electrolytes containing Prussian Blue blocking cations.
Electrochimica Acta, 2013
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Biosensors and Bioelectronics, 2010
Here we report the derivatization of mesoporous TiO 2 thin films for the preparation of H 2 O 2 a... more Here we report the derivatization of mesoporous TiO 2 thin films for the preparation of H 2 O 2 amperometric sensors. The coordination of the bifunctional ligand 1,10 phenantroline, 5,6 dione on the surface Ti(IV) ions provides open coordination sites for Fe(II) cations which are the starting point for the growth of a layer of Prussian blue polymer. The porous structure of the mesoporous TiO 2 allows the growth, ion by ion of the coordination polymer. Up to four layer of Prussian blue can be deposit without losing the porous structure of the film, which results in an enhanced response of these materials as H 2 O 2 sensors. These porous confined PB modified electrodes are robust sensors that exhibit good reproducibility, environmental stability and high sensitivity towards H 2 O 2 detection.
Chemical Communications, 2005
Prussian blue (PB) particles with the size of ca. 5 nm were synthesized and immobilized in a mult... more Prussian blue (PB) particles with the size of ca. 5 nm were synthesized and immobilized in a multilayer structure, as a strategy for the potential development of an amperometric transducer for oxidase-enzyme-based biosensors. Multilayer films composed of PB and poly(allylamine hydrochloride) (PAH) were prepared via layer-by-layer (LbL) sequential deposition. The process was carefully monitored by UV-vis spectroscopy and cyclic voltammetry. The increase of the redox current peaks during the layer-by-layer deposition demonstrated that charge propagation within the film occurs. Linear increase of UV-vis absorbance with the number of deposited bilayers indicates that well-organized systems have been elaborated. ITO electrodes coated with PB/PAH films were used successfully for detecting H 2 O 2 , sensitivity being dependent on the number of PB/PAH layers.
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Papers by Vinicius Gonçales