FCT: CENIMAT - Artigos em revista internacional com arbitragem científica
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- Optical fiber immunosensors based on surface plasmon resonance for the detection of Escherichia coliPublication . Oliveira, Sandro C.; Soares, Simone; Rodrigues, Andreia C. M.; Gonçalves, Bárbara V.; Soares, Amadeu M. V. M.; Santos, Nuno; Kumar, Santosh; Almeida, Pedro; Marques, Carlos; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Optical Society of AmericaEvery year, millions of people suffer some form of illness associated with the consumption of contaminated food. Escherichia coli (E. coli), found in the intestines of humans and other animals, is commonly associated with various diseases, due to the existence of pathogenic strains. Strict monitoring of food products for human consumption is essential to ensure public health, but traditional cell culture-based methods are associated with long waiting times and high costs. New approaches must be developed to achieve cheap, fast, and on-site monitoring. Thus, in this work, we developed optical fiber sensors based on surface plasmon resonance. Gold and cysteamine-coated fibers were functionalized with anti-E. coli antibody and tested using E. coli suspensions with concentrations ranging from 1 cell/mL to 105 cells/mL. An average logarithmic sensitivity of 0.21 ± 0.01 nm/log(cells/mL) was obtained for three independent assays. An additional assay revealed that including molybdenum disulfide resulted in an increase of approximately 50% in sensitivity. Specificity and selectivity were also evaluated, and the sensors were used to analyze contaminated water samples, which verified their promising applicability in the aquaculture field.
- Flash Sintered Potassium Sodium NiobatePublication . Serrazina, Ricardo; Tkach, Alexander; Pereira, Luís; Senos, Ana M. O. R.; Vilarinho, Paula M.; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Molecular Diversity Preservation International (MDPI)Alternative sintering technologies promise to overcome issues associated with conventional ceramic sintering such as high thermal budgets and CO2 footprint. The sintering process becomes even more relevant for alkali-based piezoelectric ceramics such as K0.5Na0.5NbO3 (KNN) typically fired above 1100 °C for several hours that induces secondary phase formation and, thereby, degrades their electrical characteristics. Here, an ability of KNN ceramics to be of high performance is successfully demonstrated, using an electric field- and current-assisted Flash sintering technique at 900 °C only. Reported for the first time, Flash sintered KNN ceramics have room-temperature remnant polarization Pr = 21 μC/cm2 and longitudinal piezoelectric coefficient d33 = 117 pC/N, slightly superior to that of conventional ones due to the reduced content of secondary phases. High-performance KNN ceramics Flash sintered at a low-thermal budget have implications for the development of innovative low carbon technologies, electroceramics stakeholders, and piezoelectric energy harvesters.
- Atmosphere-Assisted FLASH Sintering of Nanometric Potassium Sodium NiobatePublication . Serrazina, Ricardo; Pereira, Luís; Vilarinho, Paula M.; Senos, Ana M.; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); MDPI AGDicarboxymethyl cellulose (DCMC) was synthesized and tested for protein adsorption. The prepared polymer was characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and solid state nuclear magnetic resonance (ssNMR) to confirm the functionalization of cellulose. This work shows that protein adsorption onto DCMC is charge dependent. The polymer adsorbs positively charged proteins, cytochrome C and lysozyme, with adsorption capacities of 851 and 571 mg g−1, respectively. In both experiments, the adsorption process follows the Langmuir adsorption isotherm. The adsorption kinetics by DCMC is well described by the pseudo second-order model, and adsorption equilibrium was reached within 90 min. Moreover, DCMC was successfully reused for five consecutive adsorption–desorption cycles, without compromising the removal efficiency (98–99%).
- Water Molecular Dynamics in the Porous Structures of Ultrafiltration/Nanofiltration Asymmetric Cellulose Acetate-Silica MembranesPublication . Cunha, João; da Silva, Miguel P.; Beira, Maria J.; Corvo, Marta C.; Almeida, Pedro L.; Sebastião, Pedro José; Figueirinhas, João L.; de Pinho, Maria Norberta; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); MDPI AGThis study presents the characterization of water dynamics in cellulose acetate-silica asymmetric membranes with very different pore structures that are associated with a wide range of selective transport properties of ultrafiltration (UF) and nanofiltration (NF). By combining 1H NMR spectroscopy, diffusometry and relaxometry and considering that the spin-lattice relaxation rate of the studied systems is mainly determined by translational diffusion, individual rotations and rotations mediated by translational displacements, it was possible to assess the influence of the porous matrix's confinement on the degree of water ordering and dynamics and to correlate this with UF/NF permeation characteristics. In fact, the less permeable membranes, CA/SiO2-22, characterized by smaller pores induce significant orientational order to the water molecules close to/interacting with the membrane matrix's interface. Conversely, the model fitting analysis of the relaxometry results obtained for the more permeable sets of membranes, CA/SiO2-30 and CA/SiO2-34, did not evidence surface-induced orientational order, which might be explained by the reduced surface-to-volume ratio of the pores and consequent loss of sensitivity to the signal of surface-bound water. Comparing the findings with those of previous studies, it is clear that the fraction of more confined water molecules in the CA/SiO2-22-G20, CA/SiO2-30-G20 and CA/SiO2-34-G20 membranes of 0.83, 0.24 and 0.35, respectively, is in agreement with the obtained diffusion coefficients as well as with the pore sizes and hydraulic permeabilities of 3.5, 38 and 81 kg h-1 m-2 bar-1, respectively, reported in the literature. It was also possible to conclude that the post-treatment of the membranes with Triton X-100 surfactants produced no significant structural changes but increased the hydrophobic character of the surface, leading to higher diffusion coefficients, especially for systems associated with average smaller pore dimensions. Altogether, these findings evidence the potential of combining complementary NMR techniques to indirectly study hydrated asymmetric porous media, assess the influence of drying post-treatments on hybrid CA/SiO2 membrane' surface characteristics and discriminate between ultra- and nano-filtration membrane systems.
- Study on the Incorporation of Chitosan Flakes in Electrospun Polycaprolactone ScaffoldsPublication . Querido, Diana; Vieira, Tânia; Ferreira, José Luís; Henriques, Célia; Borges, João Paulo; Silva, Jorge Carvalho; DF – Departamento de Física; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; MDPI - Multidisciplinary Digital Publishing InstituteHybrid scaffolds obtained by combining two or more biopolymers are studied in the context of tissue regeneration due to the possibility of achieving new functional properties or structural features. The aim of this work was to produce a new type of hybrid polycaprolactone (PCL)/chitosan (CS) electrospun mat through the controlled deposition of CS flakes interspaced between the PCL fibers. A poly(ethylene oxide) (PEO) solution was used to transport CS flakes with controlled size. This, and the PCL solution, were simultaneously electrospun onto a rotatory mandrel in a perpendicular setup. Different PCL/CS mass ratios were also studied. The morphology of the resulting fibers, evaluated by SEM, confirmed the presence of the CS flakes between the PCL fibers. The addition of PEO/CS fibers resulted in hydrophilic mats with lower Young's modulus relatively to PCL mats. In vitro cell culture results indicated that the addition of CS lowers both the adhesion and the proliferation of human dermal fibroblasts. The present work demonstrates the feasibility of achieving a controlled deposition of a polymeric component in granular form onto a collector where electrospun nanofibers are being deposited, thereby producing a hybrid scaffold.
- Tuning the 1H NMR Paramagnetic Relaxation Enhancement and Local Order of [Aliquat]+-Based Systems Mixed with DMSOPublication . Cordeiro, Rui; Beira, Maria J.; Cruz, Carlos; Figueirinhas, João L; Corvo, Marta C; Almeida, Pedro L; Rosatella, Andreia A.; Afonso, Carlos A. M.; Daniel, Carla I.; Sebastião, Pedro J.; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); LAQV@REQUIMTE; DQ - Departamento de Química; MDPI - Multidisciplinary Digital Publishing InstituteUnderstanding the behavior of a chemical compound at a molecular level is fundamental, not only to explain its macroscopic properties, but also to enable the control and optimization of these properties. The present work aims to characterize a set of systems based on the ionic liquids [Aliquat][Cl] and [Aliquat][FeCl4] and on mixtures of these with different concentrations of DMSO by means of 1H NMR relaxometry, diffusometry and X-ray diffractometry. Without DMSO, the compounds reveal locally ordered domains, which are large enough to induce order fluctuation as a significant relaxation pathway, and present paramagnetic relaxation enhancement for the [Aliquat][Cl] and [Aliquat][FeCl4] mixture. The addition of DMSO provides a way of tuning both the local order of these systems and the relaxation enhancement produced by the tetrachloroferrate anion. Very small DMSO volume concentrations (at least up to 1%) lead to enhanced paramagnetic relaxation without compromising the locally ordered domains. Larger DMSO concentrations gradually destroy these domains and reduce the effect of paramagnetic relaxation, while solvating the ions present in the mixtures. The paramagnetic relaxation was explained as a correlated combination of inner and outer-sphere mechanisms, in line with the size and structure differences between cation and anion. This study presents a robust method of characterizing paramagnetic ionic systems and obtaining a consistent analysis for a large set of samples having different co-solvent concentrations.
- Study of a late bronze age casting mould and its black residue by 3D imaging, pXRF, SEM-EDS, micro-FTIR and micro-ramanPublication . Figueiredo, Elin; Bottaini, Carlo; Miguel, Catarina; Lackinger, Aaron; Mirão, José; Rey, Beatriz Comendador; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); MDPI - Multidisciplinary Digital Publishing InstituteIn the present work, a fragment of a stone mould recently found in Galicia (NW Spain) was studied by multiple analytical techniques approach involving 3D optical imaging reconstruction to obtain data about the shape of the mould, typology of artefact produced, and distribution of a black residue at the surface of the mould and pXRF, SEM-EDS, micro-FTIR, and micro-Raman to investigate the nature of the black residue. The study shows that the mould was likely used for socketed axes with a side loop, was originally composed of two valves and one core, and that it might have been subjected to a repair during use. The black residue is distributed in the carved surface and spreads to nearby surfaces as a result of the use of the mould. The alloy cast in the mould was a ternary bronze (Cu + Sn + Pb). The analyses by SEM-EDS of black residue covering the surface did show the presence of scattered micro particles with P and Ca, and micro-Raman analysis detected the presence of a carbon black of animal source, while micro-FTIR analysis detected remains of proteins, oxalates, and hydroxyapatite. These results are amongst the very few studies made on black residues of ancient moulds and suggest that the mould was dressed with a carbon black of animal origin, such as burned bones, prior to metal casting, probably used as a coating agent to improve the casting and artefact recovery.
- Particle characteristics’ influence on FLASH sintering of potassium sodium niobatePublication . Serrazina, Ricardo; Ribeiro, Camila; Costa, Maria E. V.; Pereira, Luis; Vilarinho, Paula M.; Senos, Ana M. O. R.; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Molecular Diversity Preservation International (MDPI)The considerable decrease in temperature and time makes FLASH sintering a more sustainable alternative for materials processing. FLASH also becomes relevant if volatile elements are part of the material to be processed, as in alkali‐based piezoelectrics like the promising lead‐free K0.5Na0.5NbO3 (KNN). Due to the volatile nature of K and Na, KNN is difficult to process by conventional sintering. Although some studies have been undertaken, much remains to be understood to properly engineer the FLASH sintering process of KNN. In this work, the effect of FLASH temperature, TF, is studied as a function of the particle size and impurity content of KNN powders. Differences are demonstrated: while the particle size and impurity degree markedly influence TF, they do not significantly affect the densification and grain growth processes. The conductivity of KNN FLASH‐sintered ceramics and KNN single crystals (SCs) is compared to elucidate the role of particles’ surface conduction. When particles’ surfaces are not present, as in the case of SCs, the FLASH process requires higher temperatures and conductivity values. These results have implications in understanding FLASH sintering towards a more sustainable processing of lead‐free piezoelectrics.
- Al calor del FuegoPublication . Comendador Rey, Beatriz; Lackinger, Aaron; Figueiredo, Elin; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N)En este artículo se sintetizan diversas acciones llevadas a cabo en el ámbito de la arqueometalurgia prehistórica y la arqueología experimental, con el fin de promover tanto su investigación académica, como su didáctica en distintos contextos educativos. En su mayor parte han estado dirigidos a que se conozcan los principales aspectos de la cadena técnica operativa teórica de producción del metal de base cobre y del hierro. En estas actividades, se busca aportar a los participantes las herramientas teóricas y empíricas básicas para la comprensión de los procesos metalúrgicos en la Prehistoria, a través del aprendizaje basado en la recreación tecnológica y al mismo tiempo, ofertar la participación activa en los procesos y su adquisición experiencial.
- Combining Soft with Hard Condensed Matter for Circular Polarized Light Sensing and Logic OperationsPublication . Grey, Paul; Chapa, Manuel; Alexandre, Miguel; Mateus, Tiago; Fortunato, Elvira; Martins, Rodrigo; Mendes, Manuel J.; Pereira, Luís; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); John Wiley & Sons, Inc.The study shows the incorporation of chiral nematic photonic cellulose nanocrystal (CNC) films, well known for their adaptive character of selective reflection of circular polarized light (CPL), and silicon-based thin-film photodiodes, thus achieving a light sensor capable of discriminating right- from left-handed CPL. The circular polarization (CP) response is maximum for specific wavelengths in the green-to-red region. When subjected to these wavelengths, they produce photocurrents that are over 50% distinct between the two CP states. Proper signal processing, thus, yields a binary output depending on the handedness of the light. Through the addition of monovalent salt to the initial CNC suspension, a blueshift to the photonic band gap is induced, enabling a larger wavelength gamut and application possibilities. The measured results are then used as a basis for electromagnetic simulations that show remarkable consistency with the experimental results, thus defining a new tool that can be used to efficiently optimize the devices’ response. Fast transient responses to CPL are shown with possible logic operations, as well as humidity sensing. The developed devices are, thus, applicable in areas as diverse as imaging, CPL sensing, optoelectronic counterfeiting, and information processing with logic states that depend solely on the handedness of the incident light.
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