João, C. F. C., A. C. Baptista, I. M. M. Ferreira, J. C. Silva, and J. P. Borges,
"https://vtt.pure.elsevier.com/en/publications/transflexteg-large-area-transparent-thin-film-thermoelectric-devi",
Fibrous and textile materials for composite applications, Singapore, Springer, pp. 261-299, 2016.
AbstractCellulose and chitin are the two most abundant natural polysaccharides. Both have a semicrystalline microfibrillar structure from which nanofibres can be extracted. These nanofibres are rod-like microcrystals that can be used as nanoscale reinforcements in composites due to their outstanding mechanical properties. This chapter starts by reviewing the sources, extraction methods and properties of cellulose and chitin nanofibres. Then, their use in the fabrication of structural and functional nanocomposites and the applications that have been investigated are reviewed. Nanocomposites are materials with internal nano-sized structures. They benefit from the properties of the nanofillers: low density, nonabrasive, nontoxic, low cost, susceptibility to chemical modifications and biodegradability. Diverse manufacturing technologies have been used to produce films, fibres, foams, sponges, aerogels, etc. Given their natural origin and high stiffness, these polymers have attracted a lot of attention not only in the biomedical and tissue engineering fields but also in areas such as pharmaceutics, cosmetics, agriculture, biosensors and water treatment.
Soares, P. I. P., C. A. T. Laia, A. Carvalho, L. C. J. Pereira, J. T. Coutinho, I. M. M. Ferreira, C. M. M. Novo, and J. P. Borges,
"Iron oxide nanoparticles stabilized with a bilayer of oleic acid for magnetic hyperthermia and MRI applications",
Appl Surf Sci, vol. 383, pp. 240-247, 2016.
AbstractIron oxide nanoparticles (Fe3O4, IONPs) are promising candidates for several biomedical applications such as magnetic hyperthermia and as contrast agents for magnetic resonance imaging (MRI). However, their colloidal stability in physiological conditions hinders their application requiring the use of biocompatible surfactant agents. The present investigation focuses on obtaining highly stable IONPs, stabilized by the presence of an oleic acid bilayer. Critical aspects such as oleic acid concentration and pH were optimized to ensure maximum stability. NPs composed of an iron oxide core with an average diameter of 9 nm measured using transmission electron microscopy (TEM) form agglomerates with an hydrodynamic diameter of around 170 nm when dispersed in water in the presence of an oleic acid bilayer, remaining stable (zeta potential of −120 mV). Magnetic hyperthermia and the relaxivities measurements show high efficiency at neutral pH which enables their use for both magnetic hyperthermia and MRI.
Soares, P. I. P., D. Machado, C. Laia, L. C. J. Pereira, J. T. Coutinho, I. M. M. Ferreira, C. M. M. Novo, and J. P. Borges,
"Thermal and magnetic properties of chitosan-iron oxide nanoparticles",
Carbohydr Polym, vol. 149, pp. 382-390, 2016.
AbstractChitosan is a biopolymer widely used for biomedical applications such as drug delivery systems, wound healing, and tissue engineering. Chitosan can be used as coating for other types of materials such as iron oxide nanoparticles, improving its biocompatibility while extending its range of applications.
In this work iron oxide nanoparticles (Fe3O4 NPs) produced by chemical precipitation and thermal decomposition and coated with chitosan with different molecular weights were studied. Basic characterization on bare and chitosan-Fe3O4 NPs was performed demonstrating that chitosan does not affect the crystallinity, chemical composition, and superparamagnetic properties of the Fe3O4 NPs, and also the incorporation of Fe3O4 NPs into chitosan nanoparticles increases the later hydrodynamic diameter without compromising its physical and chemical properties. The nano-composite was tested for magnetic hyperthermia by applying an alternating current magnetic field to the samples demonstrating that the heating ability of the Fe3O4 NPs was not significantly affected by chitosan.
Soares, P. I. P., A. I. Sousa, I. M. M. Ferreira, C. M. M. Novo, and J. P. Borges,
"Towards the development of multifunctional chitosan-based iron oxide nanoparticles: Optimization and modelling of doxorubicin release",
Carbohydr Polym, vol. 153, pp. 212-221, 2016.
AbstractIn the present work composite nanoparticles with a magnetic core and a chitosan-based shell were produced as drug delivery systems for doxorubicin (DOX). The results show that composite nanoparticles with a hydrodynamic diameter within the nanometric range are able to encapsulate more DOX than polymeric nanoparticles alone corresponding also to a higher drug release. Moreover the synthesis method of the iron oxide nanoparticles influences the total amount of DOX released and a high content of iron oxide nanoparticles inhibits DOX release. The modelling of the experimental results revealed a release mechanism dominated by Fickian diffusion.
Bianchi, C., J. Loureiro, P. Duarte, J. Marques, J. Figueira, I. Ropio, and I. Ferreira,
"V2O5 Thin Films for Flexible and High Sensitivity Transparent Temperature Sensor",
Advanced Materials Technologies, vol. 1, issue 6, pp. 1600077, 2016.
AbstractThis work reports the optimization of V2O5 Seebeck coefficient to obtain high sensitivity and transparent temperature sensors. It is observed that the film thickness plays a major role on the thermoelectric properties, together with the annealing step, obtaining a Seebeck coefficient of −690 μV K−1, for 75 nm thick V2O5 films deposited on glass, after an annealing step of 1 h at 773 K, in air. The V2O5 films are also deposited and optimized on polyimide substrates, but lower annealing temperature is required, 573 K for 3 h, to maintain the flexibility of the substrate and simultaneously high Seebeck coefficient, −591 μV K−1. These films are used in a simple design sensor and tested on the surface of a microfluidic channel (500 μm) made of polydimethylsiloxane, while having hot water flowing through it. The response time is below 1 s and the recovery time around 5 s.
Bianchi, C., L. M. Ferreira, J. Loureiro, A. Rodrigues, P. Duarte, A. C. Baptista, and I. M. Ferreira,
"Vanadium Pentoxide Alloyed with Graphite for Thin-Film Thermal Sensors",
J. Electron. Mater., vol. 45, issue 3, pp. 1987–1991, 2016.
AbstractThe thermoelectric (TE) properties of vanadium pentoxide (V2O5) alloyed with graphite (G) were studied as a function of its incorporation percentage. Variable weight percentages of graphite powder (0–50%) were added to V2O5 powder and their mixtures were evaporated by a thermal evaporation technique to form thin films with a thickness in the range of 30–80 nm. In the infrared wavelength region, the transmittance of the obtained films increased as the G percentage was increased, while in the visible range, it decreased with G up to 10%. The TE properties were improved when G was in the range of 10–30%, while it decreased for the other percentages: Seebeck coefficient (S) changed from 0.6 mV/K to 0.9 mV/K and was zero with a G of 50%; the electrical conductivity varied slightly from 5 (Ωm)−1 to 0.7 (Ωm)−1 while the mobility improved from 0.07 cm2/V s to 1.5 cm2/V s and the respective carrier concentration was reduced, from 1 × 1018 cm−3 to 4 × 1016 cm−3. These films were applied as temperature sensors evaluating the thermovoltage as a function of thermal gradient between two electrodes, in which one was maintained at room temperature.