Center for Nanotechnology and Smart Materials

Vila Nova de Famalicão, Portugal

Center for Nanotechnology and Smart Materials

Vila Nova de Famalicão, Portugal
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California A.,Center for Nanotechnology and Smart Materials | Silva A.S.,Center for Nanotechnology and Smart Materials | Goncalves J.,Center for Nanotechnology and Smart Materials | Branco A.,Ynvisible | And 2 more authors.
Solar Energy Materials and Solar Cells | Year: 2016

Low-cost electrochromic devices presenting fast switching continue to have an enormous interest for industrial applications; however the durability of the devices is a parameter of critical importance. The present work describes the preparation and characterization of ITO free electrochromic devices, being the use of hybrid electrodes for low-cost electrochromic devices the main focus. It was used silver grids (silver ink) as electrically conductive electrodes. These grids were screen-printed on polyethylene terephthalate (PET), using two different patterns and different line widths. The printing of a conductive polymer film on top of the grids for electrochemical protection of the metal was evaluated. These grids were characterized in terms of equivalent resistance and light transmission, considering each pattern, as well as electrochemical stability. The resulting electrochromic devices were tested using cyclic voltammetry, spectroelectrochemistry and colorimetry. The durability of the devices was characterized through the analysis of color contrast over time during continuous operation conditions using a cycling program. These experiments displayed electrochromic devices performing 100 cycles before degradation with switching times of 4.5 s and a color contrast (ΔE) of 27 or a variation in transmittance of 50% between redox states. © 2016 Elsevier B.V. All rights reserved.


Silva M.P.,University of Minho | Costa C.M.,Center for Nanotechnology and Smart Materials | Sencadas V.,University of Minho | Paleo A.J.,University of Minho | Lanceros-Mendez S.,University of Minho
Journal of Polymer Research | Year: 2011

The effect of annealing temperature and time on the dielectric and piezoelectric response of poly(vinylidene fluoride), PVDF, was studied. The observed decrease in the value of the dielectric, ε, and piezoelectric, d 33, constants is related to depoling of the material and not to variations of the degree of crystallinity or the electroactive β-phase content. In a general way, the dielectric and piezoelectric responses decrease strongly in the first 4 h at a given temperature, in particular for temperatures higher that 80 °C, reaching stable values for longer annealing times. For most applications, the temperature of 100 °C will set the limit of suitable performance. Nevertheless, the material still retains a stable piezoelectric response of ca. 4 pC/N after reaching temperatures of 140 °C. The mechanisms behind the observed behavior are discussed. © 2010 Springer Science+Business Media B.V.


Kiersztyn I.,University of Porto | Neto L.,University of Porto | Carneiro A.,University of Porto | Carneiro A.,Center for Nanotechnology and Smart Materials | And 3 more authors.
Journal of Solid State Electrochemistry | Year: 2012

Poly[Cu(3-MeOsalpd)] films with good physical, chemical and electrochemical stability may be potentiodynamically electrodeposited with high deposition efficiency from acetonitrile solutions of the monomer. Comparative coulometric assays with the Ni-based analogue show that themetal in the salen motif does play a role in the electronic structure of the polymer, but that the electroactive response is ligand (not metal) based. The dynamics of redox switching are ultimately limited by coupled electron/counter ion diffusion, but this process is sufficiently rapid that it influences the voltammetric response only for thick films (Γ >420 nmol cm -2) at high scan rates. Redox cycling in monomer-free electrolyte shows a voltammetric signature that responds, via interaction with the pseudo-crown ether receptor sites, to the presence of Li +, K +, Mg 2+ and Ba 2+ ions in solution. The most prominent change is associated with the first anodic peak in the i-E signature. For each of the metal ions considered, this peak potential responds logarithmically to concentration in a manner that varies with individual complexed cation and film thickness and to an extent greater than predicted by the Nernst equation. The film characteristics offer some analytical promise, including a tradeoff between sensitivity and dynamic range and signal amplification, possibly due to supramolecular effects. © Springer-Verlag 2012.


Neto R.,Center for Nanotechnology and Smart Materials | Cardoso A.P.,Center for Nanotechnology and Smart Materials | Silva C.J.S.M.,Center for Nanotechnology and Smart Materials
Progress in Organic Coatings | Year: 2015

This work describes the functionalization of a natural and a man-made textile substrate, namely cotton and polyamide 6.6, with inclusion agents, β-cyclodextrins (β-CDs) that are able to release gradually to the user active ingredients. In this study we used aescin (aesculus hippocastanum extract), which is a natural agent with benefits for the treatment of varicose veins. 1H NMR and UV-vis data supported the role of β-CDs as an aescin complexing agent, and the covalent nature of the linkage between β-cyclodextrins and the textile substrates, which showed a wash fastness to more than 45 washing cycles. © 2014 Elsevier B.V.


Vazzana M.,Messina University | Andreani T.,University of Trás os Montes e Alto Douro | Andreani T.,Center for Research and Technology of Agro Environmental and Biological science | Fangueiro J.,University of Coimbra | And 7 more authors.
Biomedicine and Pharmacotherapy | Year: 2015

Tramadol hydrochloride (TrHC) is a synthetic analgesic drug exhibiting opioid and non-opioid properties, acting mainly on the central nervous system. It has been mostly used to treat pain, although its use to treat anxiety and depression has also been documented. These properties arise from the fact that they inhibit serotonin (5-HT) reuptake augmenting 5-HT concentration on the synaptic cleft. Despite this, TrHC has also been described to have several side effects which are mainly due to its fast metabolization and excretion which in turn requires multiple doses per day. To surpass this limitation, new pharmaceutical formulations are being developed intending the protection, target and sustained delivery as well as a reduction on daily dose aiming a reduction on the side effects. In the present work we have revised the efficacy, safety, biological and adverse effects of TrHC, and the added value of developing a novel drug delivery system for topical administration. © 2015 Elsevier Masson SAS.


Couto S.,University of Porto | Campos J.B.L.M.,University of Porto | Mayor T.S.,Center for Nanotechnology and Smart Materials
International Journal of Clothing Science and Technology | Year: 2011

Purpose: The purpose of this paper is to investigate the heat transfer on an alpine-climbing mitt featuring an electrical heating multilayer, in order to provide information for the optimization of its thermal performance. Design/methodology/approach: A numerical model was developed to simulate the heat transfer across an electrical-heated alpine mitt. The model was used to study the heat losses as a function of the environmental conditions, to optimise the positioning of the heating elements, to determine the optimal power input to the heating system, to estimate the battery capacity requirements and to assess the effect of low-emissivity surfaces. Findings: The results show that: the heating elements assure approximately constant temperatures across the skin provided they are not more than 6-7 mm apart; the use of low-emissivity surfaces facing the skin can reduce the total heat loss by 8-36 per cent (for air layer thicknesses in the range 10-3 to 10-2 m) and to increase the skin temperature during the transient operation of the heating multilayer; the heat losses from the mitt are practically independent of the chosen heating power; and a battery capacity of 4 A h assures active temperature regulation for more than 18-23 h. Practical implications: By enhancing the thermal performance of an electrical heating mitt, the use of low-emissivity surfaces (facing the skin) can favour the thermal comfort perception of its user. Originality/value: The influence of several parameters on the thermal performance of an electrical-heated mitt is analysed and discussed. The findings are relevant for improving the performance of existing electrical heating garments. © Emerald Group Publishing Limited.


Mayor T.S.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Couto S.,Center for Nanotechnology and Smart Materials | Psikuta A.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Rossi R.M.,Empa - Swiss Federal Laboratories for Materials Science and Technology
International Journal of Biometeorology | Year: 2015

The ability of clothing to provide protection against external environments is critical for wearer’s safety and thermal comfort. It is a function of several factors, such as external environmental conditions, clothing properties and activity level. These factors determine the characteristics of the different microclimates existing inside the clothing which, ultimately, have a key role in the transport processes occurring across clothing. As an effort to understand the effect of transport phenomena in clothing microclimates on the overall heat transport across clothing structures, a numerical approach was used to study the buoyancy-driven heat transfer across horizontal air layers trapped inside air impermeable clothing. The study included both the internal flow occurring inside the microclimate and the external flow occurring outside the clothing layer, in order to analyze the interdependency of these flows in the way heat is transported to/from the body. Two-dimensional simulations were conducted considering different values of microclimate thickness (8, 25 and 52 mm), external air temperature (10, 20 and 30 °C), external air velocity (0.5, 1 and 3 m s−1) and emissivity of the clothing inner surface (0.05 and 0.95), which implied Rayleigh numbers in the microclimate spanning 4 orders of magnitude (9 × 102–3 × 105). The convective heat transfer coefficients obtained along the clothing were found to strongly depend on the transport phenomena in the microclimate, in particular when natural convection is the most important transport mechanism. In such scenario, convective coefficients were found to vary in wavy-like manner, depending on the position of the flow vortices in the microclimate. These observations clearly differ from data in the literature for the case of air flow over flat-heated surfaces with constant temperature (which shows monotonic variations of the convective heat transfer coefficients, along the length of the surface). The flow patterns and temperature fields in the microclimates were found to strongly depend on the characteristics of the external boundary layer forming along the clothing and on the distribution of temperature in the clothing. The local heat transfer rates obtained in the microclimate are in marked contrast with those found in the literature for enclosures with constant-temperature active walls. These results stress the importance of coupling the calculation of the internal and the external flows and of the heat transfer convective and radiative components, when analyzing the way heat is transported to/from the body. © 2015 ISB


PubMed | European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Center for Nanotechnology and Smart Materials and Technological Center for Textile and Clothing Industry
Type: | Journal: Journal of tissue engineering and regenerative medicine | Year: 2016

Textile-based technologies are powerful routes for the production of three-dimensional porous architectures for tissue engineering applications because of their feasibility and possibility for scaling-up. Herein, the use of knitting technology to produce polybutylene succinate fibre-based porous architectures is described. Furthermore, different treatments have been applied to functionalize the surface of the scaffolds developed: sodium hydroxide etching, ultraviolet radiation exposure in an ozone atmosphere and grafting (acrylic acid, vinyl phosphonic acid and vinyl sulphonic acid) after oxygen plasma activation as a way to tailor cell adhesion. A possible effect of the applied treatments on the bulk properties of the textile scaffolds has been considered and thus tensile tests in dry and hydrated states were also carried out. The microscopy results indicated that the surface morphology and roughness were affected by the applied treatments. The X-ray photoelectron spectroscopy and contact angle measurements showed the incorporation of oxygen-containing groups and higher surface free energy as result of the surface treatments applied. The DNA quantification and scanning electron microscopy analysis revealed that these modifications enhanced cell adhesion and altered cell morphology. Generally, sodium hydroxide treatment altered most significantly the surface properties, which in turn resulted in a high number of cells adherent to these surfaces. Based on the results obtained, the proposed surface treatments are appropriate to modify polybutylene succinate knitting scaffolds, influencing cell adhesion and its potential for use in tissue engineering applications. Copyright 2016 John Wiley & Sons, Ltd.


PubMed | University of Trás os Montes e Alto Douro, University of Barcelona, University of Coimbra, University of Naples Federico II and 2 more.
Type: | Journal: Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie | Year: 2015

Tramadol hydrochloride (TrHC) is a synthetic analgesic drug exhibiting opioid and non-opioid properties, acting mainly on the central nervous system. It has been mostly used to treat pain, although its use to treat anxiety and depression has also been documented. These properties arise from the fact that they inhibit serotonin (5-HT) reuptake augmenting 5-HT concentration on the synaptic cleft. Despite this, TrHC has also been described to have several side effects which are mainly due to its fast metabolization and excretion which in turn requires multiple doses per day. To surpass this limitation, new pharmaceutical formulations are being developed intending the protection, target and sustained delivery as well as a reduction on daily dose aiming a reduction on the side effects. In the present work we have revised the efficacy, safety, biological and adverse effects of TrHC, and the added value of developing a novel drug delivery system for topical administration.


PubMed | Center for Nanotechnology and Smart Materials and Empa - Swiss Federal Laboratories for Materials Science and Technology
Type: Journal Article | Journal: International journal of biometeorology | Year: 2015

The ability of clothing to provide protection against external environments is critical for wearers safety and thermal comfort. It is a function of several factors, such as external environmental conditions, clothing properties and activity level. These factors determine the characteristics of the different microclimates existing inside the clothing which, ultimately, have a key role in the transport processes occurring across clothing. As an effort to understand the effect of transport phenomena in clothing microclimates on the overall heat transport across clothing structures, a numerical approach was used to study the buoyancy-driven heat transfer across horizontal air layers trapped inside air impermeable clothing. The study included both the internal flow occurring inside the microclimate and the external flow occurring outside the clothing layer, in order to analyze the interdependency of these flows in the way heat is transported to/from the body. Two-dimensional simulations were conducted considering different values of microclimate thickness (8, 25 and 52 mm), external air temperature (10, 20 and 30 C), external air velocity (0.5, 1 and 3 m s(-1)) and emissivity of the clothing inner surface (0.05 and 0.95), which implied Rayleigh numbers in the microclimate spanning 4 orders of magnitude (910(2)-310(5)). The convective heat transfer coefficients obtained along the clothing were found to strongly depend on the transport phenomena in the microclimate, in particular when natural convection is the most important transport mechanism. In such scenario, convective coefficients were found to vary in wavy-like manner, depending on the position of the flow vortices in the microclimate. These observations clearly differ from data in the literature for the case of air flow over flat-heated surfaces with constant temperature (which shows monotonic variations of the convective heat transfer coefficients, along the length of the surface). The flow patterns and temperature fields in the microclimates were found to strongly depend on the characteristics of the external boundary layer forming along the clothing and on the distribution of temperature in the clothing. The local heat transfer rates obtained in the microclimate are in marked contrast with those found in the literature for enclosures with constant-temperature active walls. These results stress the importance of coupling the calculation of the internal and the external flows and of the heat transfer convective and radiative components, when analyzing the way heat is transported to/from the body.

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