Baptista, A. C., A. M. Botas, A. P. C. Almeida, A. T. Nicolau, B. P. Falcão, M. J. Soares, J. P. Leitão, R. Martins, J. P. Borges, and I. Ferreira,
"Down conversion photoluminescence on PVP/Ag-nanoparticles electrospun composite fibers",
Opt. Mater., vol. 39, pp. 278-281, 2015.
AbstractThe influence of Ag nanoparticles (Ag NPs) on the luminescence of electrospun nonwoven mats made of polyvinylpyrrolidone (PVP) has been studied in this work. The PVP fibers incorporating 2.1–4.3 nm size Ag NPs show a significant photoluminescence (PL) band between 580 and 640 nm under 325 nm laser excitation. The down conversion luminescence emission is present even after several hours of laser excitation, which denotes the durability and stability of fibers to consecutive excitations. As so these one-dimensional photonic fibers made using cheap methods is of great importance for organic optoelectronic applications, fluorescent clothing or counterfeiting labels.
Baptista, A. C., I. Ropio, B. Romba, J. P. Nobre, C. Henriques, J. C. Silva, J. I. Martins, J. P. Borges, and I. Ferreira,
"Cellulose-based electrospun fibers functionalized with polypyrrole and polyaniline for fully organic batteries",
J Mater Chem A, vol. 6, issue 1, pp. 256-265, 2018.
AbstractA novel cellulose-based bio-battery made of electrospun fibers activated by biological fluids has been developed. This work reports a new concept for a fully organic bio-battery that takes advantage of the high surface to volume ratio achieved by an electrospun matrix composed of sub-micrometric fibers that acts simultaneously as the separator and the support of the electrodes. Polymer composites of polypyrrole (PPy) and polyaniline (PANI) with cellulose acetate (CA) electrospun matrix were produced by in situ chemical oxidation of pyrrole and aniline on the CA fibers. The structure (CA/PPy|CA|CA/PANI) generated a power density of 1.7 mW g−1 in the presence of simulated biological fluids, which is a new and significant contribution to the domain of medical batteries and fully organic devices for biomedical applications.
Bianchi, C., A. C. Marques, R. C. da Silva, T. Calmeiro, and I. Ferreira,
"Near infrared photothermoelectric effect in transparent AZO/ITO/Ag/ITO thin films",
Scientific reports, vol. 11, pp. 1-11, 2021.
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.
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.