Abel Santos - Academia.edu (original) (raw)

Papers by Abel Santos

Four types of high aspect ratio nanoporous anodic alumina funnels with one, two, three and four s... more Four types of high aspect ratio nanoporous anodic alumina funnels with one, two, three and four segments are fabricated by following sequentially anodizing and pore widening steps. The length of each segment is controlled by the total current charge passed through the system, and the pore diameter is regulated by the pore widening time length. Both the segment length and its diameter are previously established by corresponding calibration processes, which allow design with high degree of accuracy the resulting nanostructures. The geometric characteristics of the fabricated nanostructures are analyzed in detail through environmental scanning electron microscopy. It is demonstrated that the key factor to control the fabrication process of nanoporous anodic alumina funnels with high aspect ratio under controlled potential conditions is the total current charge passed through the anodization system. It is expected that this nanostructures will have multiple potential applications such as arrays of nanotubes or nanowires with various diameter-modulated segments based on multiple materials (e.g. metals, polymers, ceramics, etc.), optoelectronic devices and so forth.

Success of sheet metal forming operations is greatly influenced by mechanical properties of sheet... more Success of sheet metal forming operations is greatly influenced by mechanical properties of sheet material. A fundamental characterization of the material is usually performed by the stress-strain relationship obtained by a standardized test -tensile test. However the range of strain obtained in tensile test is under the strain values found in many forming processes. This paper presents the development of a measuring system to be incorporated in a hydraulic bulge test machine, which permits stress-strain determination up to higher levels of plastic deformation. A continuous increasing of pressure produces a biaxial tension applied to a sheet metal specimen up to the rupture point. By measuring the vertical displacement using a spherometer and the deformation changes with an extensometer, one can estimate the strain and stress being applied to the specimen. Preliminary results indicate an efficient method to obtain real time data for stress-strain sheet metal characterization.

Scientific reports, 2015

Herein, we present a systematic study on the development, optimisation and applicability of inter... more Herein, we present a systematic study on the development, optimisation and applicability of interferometrically coloured distributed Bragg reflectors based on nanoporous anodic alumina (NAA-DBRs) in the form of films and nanoporous microparticles as visual/colorimetric analytical tools. Firstly, we synthesise a complete palette of NAA-DBRs by galvanostatic pulse anodisation approach, in which the current density is altered in a periodic fashion in order to engineer the effective medium of the resulting photonic films in depth. NAA-DBR photonic films feature vivid colours that can be tuned across the UV-visible-NIR spectrum by structural engineering. Secondly, the effective medium of the resulting photonic films is assessed systematically by visual analysis and reflectometric interference spectroscopy (RIfS) in order to establish the most optimal nanoporous platforms to develop visual/colorimetric tools. Then, we demonstrate the applicability of NAA-DBR photonic films as a chemically...

Analytical chemistry, 2015

Herein, we present an interferometric sensor based on the combination of chemically functionalize... more Herein, we present an interferometric sensor based on the combination of chemically functionalized nanoporous anodic alumina photonic films (NAA-PFs) and reflectometric interference spectroscopy (RIfS) aimed to detect trace levels of enzymes by selective digestion of gelatin. The fabrication and sensing performance of the proposed sensor were characterized in real-time by estimating the changes in effective optical thickness (i.e., sensing principle) of gelatin-modified NAA-PFs (i.e., sensing element) during enzymatic digestion. The working range (WR), sensitivity (S), low limit of detection (LLoD), and linearity (R(2)) of this enzymatic sensor were established by a series of experiments with different concentrations of gelatin (i.e., specific chemical sensing element) and trypsin (i.e., analyte), a model protease enzyme with relevant implications as a biomarker in the diagnosis of several diseases. The chemical selectivity of the sensor was demonstrated by comparison of gelatin dig...

ACS applied materials & interfaces, Jan 9, 2015

In this study, we produce for the first time biomimetic films and microsized particles based on n... more In this study, we produce for the first time biomimetic films and microsized particles based on nanoporous anodic alumina distributed Bragg reflectors (NAA-DBRs) by a rational galvanostatic pulse-anodization approach. These biomimetic photonic structures can feature a broad range of vivid bright colors, which can be tuned across the UV-visible spectrum by engineering their nanoporous structure through different anodization parameters. The effective medium of NAA-DBRs films is systematically assessed as a function of the anodization period, the anodization temperature, and the current density ratio by reflectometric interference spectroscopy (RIfS). This analysis makes it possible to establish the most sensitive structure toward changes in its effective medium. Subsequently, specific detection of vitamin C molecules is demonstrated. The obtained results reveal that NAA-DBRs with optimized structure can achieve a low limit of detection for vitamin C molecules as low as 20 nM, a sensit...

Análise Psicológica, 2012

A Disfunção Eréctil (DE) designa a «incapacidade do homem conseguir a erecção do pénis como parte... more A Disfunção Eréctil (DE) designa a «incapacidade do homem conseguir a erecção do pénis como parte de um processo global e multifacetado do funcionamento sexual masculino» (NIH Consensus Statement, 1992, p. 1). É a forma adequada para expressar o que antes se designava por impotência e que é considerado um termo pejorativo.

The Journal of Physical Chemistry C, 2015

… , Saúde e Doenças, Vol. 9, supl …, 2008

Erectile dysfunction (ED) is an important public health issue for which accurate clinical evaluat... more Erectile dysfunction (ED) is an important public health issue for which accurate clinical evaluating tools are necessary. The abridged International Index of Erectile Function (IIEF-5) was developed for that purpose. The aim of the present research is to develop a Portuguese version of the IIEF-5 and to study preliminary structural metric properties. The present study used a sample of 113 healthy men. The results show that the metric properties are accurate.

ACS Applied Materials & Interfaces, 2015

Structural engineering of porous anodic aluminum oxide (AAO) nanostructures by anodization has be... more Structural engineering of porous anodic aluminum oxide (AAO) nanostructures by anodization has been extensively studied in the past two decades. However, the transition of this technique into the fabrication of AAO-based one-dimensional photonic crystal is still challenging. Herein, we report for the first time on the fabrication of AAO optical microcavities by a rationally designed anodization approach. In our study, two feasible methods are used to fabricate microcavities with tunable resonance peak across the visible and near-infrared spectra. Distributed Bragg reflector (DBR) nanostructures are first fabricated by pulse anodization approach, in which the anodization voltage was periodically manipulated to achieve pseudosinusoidal modulation of the effective refractive index gradient along the depth of the AAO nanostructures. Microcavities were created by creating a nanoporous layer of constant porosity between two AAO−DBR nanostructures, and by introducing a shift of the phase of the porosity gradient along the depth of AAO. The position of the resonance peak in these microcavities can be linearly tuned by means of the duration of the high voltage anodization. These optical nanostructures are sensitive to alterations of the effective media inside the nanopores. The AAO microcavity shows a central wavelength shift of 2.58 ± 0.37 nm when exposed to water vapor. Our research highlights the feasibility of anodization technique to fabricate AAO-based photonic nanostructures for advanced sensing applications.

Para a obtenção das propriedades mecânicas de chapas metálicas utiliza-se o ensaio de tração como... more Para a obtenção das propriedades mecânicas de chapas metálicas utiliza-se o ensaio de tração como método clássico. No entanto, o valor da deformação durante o ensaio de tração é limitado, em virtude da ocorrência de estricção. O ensaio bulge é uma alternativa para obtenção de valores de deformações mais elevadas, permitindo uma melhor caracterização do comportamento do material, com menor extrapolação e consequente melhoria dos valores dos parâmetros dos modelos de encruamento. Este artigo apresenta uma análise de sensibilidades para variáveis influentes utilizadas nas medições obtidas por um sistema experimental desenvolvido para a obtenção da curva tensão-extensão para este ensaio, tendo como objetivo a escolha das variáveis que represente o melhor compromisso para a melhor qualidade da curva de encruamento. Adicionalmente, considerando os resultados do ensaio bulge até à rotura, são apresentadas estratégias de calibração do modelo de dano Ito-Goya, usado na previsão de estricção ...

Four types of high aspect ratio nanoporous anodic alumina funnels with one, two, three and four s... more Four types of high aspect ratio nanoporous anodic alumina funnels with one, two, three and four segments are fabricated by following sequentially anodizing and pore widening steps. The length of each segment is controlled by the total current charge passed through the system, and the pore diameter is regulated by the pore widening time length. Both the segment length and its diameter are previously established by corresponding calibration processes, which allow design with high degree of accuracy the resulting nanostructures. The geometric characteristics of the fabricated nanostructures are analyzed in detail through environmental scanning electron microscopy. It is demonstrated that the key factor to control the fabrication process of nanoporous anodic alumina funnels with high aspect ratio under controlled potential conditions is the total current charge passed through the anodization system. It is expected that this nanostructures will have multiple potential applications such as arrays of nanotubes or nanowires with various diameter-modulated segments based on multiple materials (e.g. metals, polymers, ceramics, etc.), optoelectronic devices and so forth.

Success of sheet metal forming operations is greatly influenced by mechanical properties of sheet... more Success of sheet metal forming operations is greatly influenced by mechanical properties of sheet material. A fundamental characterization of the material is usually performed by the stress-strain relationship obtained by a standardized test -tensile test. However the range of strain obtained in tensile test is under the strain values found in many forming processes. This paper presents the development of a measuring system to be incorporated in a hydraulic bulge test machine, which permits stress-strain determination up to higher levels of plastic deformation. A continuous increasing of pressure produces a biaxial tension applied to a sheet metal specimen up to the rupture point. By measuring the vertical displacement using a spherometer and the deformation changes with an extensometer, one can estimate the strain and stress being applied to the specimen. Preliminary results indicate an efficient method to obtain real time data for stress-strain sheet metal characterization.

Scientific reports, 2015

Herein, we present a systematic study on the development, optimisation and applicability of inter... more Herein, we present a systematic study on the development, optimisation and applicability of interferometrically coloured distributed Bragg reflectors based on nanoporous anodic alumina (NAA-DBRs) in the form of films and nanoporous microparticles as visual/colorimetric analytical tools. Firstly, we synthesise a complete palette of NAA-DBRs by galvanostatic pulse anodisation approach, in which the current density is altered in a periodic fashion in order to engineer the effective medium of the resulting photonic films in depth. NAA-DBR photonic films feature vivid colours that can be tuned across the UV-visible-NIR spectrum by structural engineering. Secondly, the effective medium of the resulting photonic films is assessed systematically by visual analysis and reflectometric interference spectroscopy (RIfS) in order to establish the most optimal nanoporous platforms to develop visual/colorimetric tools. Then, we demonstrate the applicability of NAA-DBR photonic films as a chemically...

Analytical chemistry, 2015

Herein, we present an interferometric sensor based on the combination of chemically functionalize... more Herein, we present an interferometric sensor based on the combination of chemically functionalized nanoporous anodic alumina photonic films (NAA-PFs) and reflectometric interference spectroscopy (RIfS) aimed to detect trace levels of enzymes by selective digestion of gelatin. The fabrication and sensing performance of the proposed sensor were characterized in real-time by estimating the changes in effective optical thickness (i.e., sensing principle) of gelatin-modified NAA-PFs (i.e., sensing element) during enzymatic digestion. The working range (WR), sensitivity (S), low limit of detection (LLoD), and linearity (R(2)) of this enzymatic sensor were established by a series of experiments with different concentrations of gelatin (i.e., specific chemical sensing element) and trypsin (i.e., analyte), a model protease enzyme with relevant implications as a biomarker in the diagnosis of several diseases. The chemical selectivity of the sensor was demonstrated by comparison of gelatin dig...

ACS applied materials & interfaces, Jan 9, 2015

In this study, we produce for the first time biomimetic films and microsized particles based on n... more In this study, we produce for the first time biomimetic films and microsized particles based on nanoporous anodic alumina distributed Bragg reflectors (NAA-DBRs) by a rational galvanostatic pulse-anodization approach. These biomimetic photonic structures can feature a broad range of vivid bright colors, which can be tuned across the UV-visible spectrum by engineering their nanoporous structure through different anodization parameters. The effective medium of NAA-DBRs films is systematically assessed as a function of the anodization period, the anodization temperature, and the current density ratio by reflectometric interference spectroscopy (RIfS). This analysis makes it possible to establish the most sensitive structure toward changes in its effective medium. Subsequently, specific detection of vitamin C molecules is demonstrated. The obtained results reveal that NAA-DBRs with optimized structure can achieve a low limit of detection for vitamin C molecules as low as 20 nM, a sensit...

Análise Psicológica, 2012

A Disfunção Eréctil (DE) designa a «incapacidade do homem conseguir a erecção do pénis como parte... more A Disfunção Eréctil (DE) designa a «incapacidade do homem conseguir a erecção do pénis como parte de um processo global e multifacetado do funcionamento sexual masculino» (NIH Consensus Statement, 1992, p. 1). É a forma adequada para expressar o que antes se designava por impotência e que é considerado um termo pejorativo.

The Journal of Physical Chemistry C, 2015

… , Saúde e Doenças, Vol. 9, supl …, 2008

Erectile dysfunction (ED) is an important public health issue for which accurate clinical evaluat... more Erectile dysfunction (ED) is an important public health issue for which accurate clinical evaluating tools are necessary. The abridged International Index of Erectile Function (IIEF-5) was developed for that purpose. The aim of the present research is to develop a Portuguese version of the IIEF-5 and to study preliminary structural metric properties. The present study used a sample of 113 healthy men. The results show that the metric properties are accurate.

ACS Applied Materials & Interfaces, 2015

Structural engineering of porous anodic aluminum oxide (AAO) nanostructures by anodization has be... more Structural engineering of porous anodic aluminum oxide (AAO) nanostructures by anodization has been extensively studied in the past two decades. However, the transition of this technique into the fabrication of AAO-based one-dimensional photonic crystal is still challenging. Herein, we report for the first time on the fabrication of AAO optical microcavities by a rationally designed anodization approach. In our study, two feasible methods are used to fabricate microcavities with tunable resonance peak across the visible and near-infrared spectra. Distributed Bragg reflector (DBR) nanostructures are first fabricated by pulse anodization approach, in which the anodization voltage was periodically manipulated to achieve pseudosinusoidal modulation of the effective refractive index gradient along the depth of the AAO nanostructures. Microcavities were created by creating a nanoporous layer of constant porosity between two AAO−DBR nanostructures, and by introducing a shift of the phase of the porosity gradient along the depth of AAO. The position of the resonance peak in these microcavities can be linearly tuned by means of the duration of the high voltage anodization. These optical nanostructures are sensitive to alterations of the effective media inside the nanopores. The AAO microcavity shows a central wavelength shift of 2.58 ± 0.37 nm when exposed to water vapor. Our research highlights the feasibility of anodization technique to fabricate AAO-based photonic nanostructures for advanced sensing applications.

Para a obtenção das propriedades mecânicas de chapas metálicas utiliza-se o ensaio de tração como... more Para a obtenção das propriedades mecânicas de chapas metálicas utiliza-se o ensaio de tração como método clássico. No entanto, o valor da deformação durante o ensaio de tração é limitado, em virtude da ocorrência de estricção. O ensaio bulge é uma alternativa para obtenção de valores de deformações mais elevadas, permitindo uma melhor caracterização do comportamento do material, com menor extrapolação e consequente melhoria dos valores dos parâmetros dos modelos de encruamento. Este artigo apresenta uma análise de sensibilidades para variáveis influentes utilizadas nas medições obtidas por um sistema experimental desenvolvido para a obtenção da curva tensão-extensão para este ensaio, tendo como objetivo a escolha das variáveis que represente o melhor compromisso para a melhor qualidade da curva de encruamento. Adicionalmente, considerando os resultados do ensaio bulge até à rotura, são apresentadas estratégias de calibração do modelo de dano Ito-Goya, usado na previsão de estricção ...