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Projeto de investigação
Large area transparent thin film thermoelectric devices for smart window and flexible applications
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Large-Area Paper Batteries with Ag and Zn/Ag Screen-Printed Electrodes
Publication . Garcia, Diogo Miguel Esperança; Pereira, Ana Sofia Taborda Martins; Almeida, António Carranca; Roma, Urbez Santana; Soler, Alejandra Ben Aissa; Lacharmoise, Paul D.; Ferreira, Isabel Maria Mercês; Simão, Claúdia Custódio Delgado; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); ACS - American Chemical Society
Large-area paper batteries have been explored in this paper, correlating electrode materials and screen printing with the electrochemical performances. The use of office paper embedded in salt solution with two electrodes performed by an easy and large-scale application technique opens doors to a new concept of energy storage. The proposed device is Li-free and uses zinc and silver powder-based screen printable pastes to deposit the electrodes. Cyclic voltammetry and charge-discharge curves reveal the performance of the produced devices using NaCl and KOH solutions in different concentrations. The simulation of electrochemical impedance spectroscopy measurements gave clue of a similar working mechanism to conventional Li-ion batteries. After charging, a single paper battery achieves 1.83 V with 60 mA/cm2 and 90.6% charge-discharge efficiency. As a proof of concept, a small paper battery and a set integrated in series and parallel were used to power a commercial red light-emitting diode.
Microwave Synthesis of Silver Sulfide and Silver Nanoparticles: Light and Time Influence
Publication . Magalhães Sousa, David; Chiappim, William; P. Leitão, Joaquim; Lima, João Carlos; Ferreira, Isabel; LAQV@REQUIMTE; DQ - Departamento de Química
Silver sulfide (Ag2S) is a low band gap material, which absorbs near-infrared light and is of great importance in areas such as nanotechnology and biomedicine. We report the influence of the starting reagents, synthesis time, and light radiation on the geometry and size of silver sulfide nanoparticles and on the fraction of metallic Ag obtained in a microwave reactor. The X-ray diffraction diffractograms confirmed that Ag2S is the main product if the reaction's precursor contains silver in the oxidation state of +1 and mostly metallic silver (Ag°) when it is +2. Small nanoparticles (∼6 nm) of spherical geometry are present in the transmission electron microscopy images for the synthesis performed with the lamp light ON, while with the light switched OFF, wider and hundreds of nanometers longer particles are observed. This discriminative effect occurs with shorter synthesis time duration (<10 min) but when the time of reaction is extended, the particles coalesce for both light and dark conditions. Overall, it was observed by photoluminescence that crystalline Ag and Ag2S 4-8 nm nanoparticles obtained in 15 min and light irradiation during synthesis have a clear relative increase of the radiative recombination channels of the charged carriers, which are typical of materials characterized by the involvement of low density of states inside the band gap.
Conductive electrospun Polyaniline/Polyvinylpyrrolidone nanofibers: Electrical and morphological characterization of new yarns for electronic textiles
Publication . Perdigão, Patrícia; Faustino, Bruno Miguel Morais; Faria, Jaime; Canejo, João Paulo; Borges, João Paulo; Ferreira, Isabel; Baptista, Ana Catarina; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); MDPI - Multidisciplinary Digital Publishing Institute
Advanced functionalities textiles embedding electronic fibers, yarns and fabrics are a demand for innovative smart cloths. Conductive electrospun membranes and yarns based on polyaniline/polyvinylpyrrolidone (PANI/PVP) were investigated using the chemical modification of PANI instead of using conventional coating processes as in-situ polymerization. PANI was synthesized from the aniline monomer and the influence of the oxidant-to-monomer ratio on electrical conductivity was studied. The optimized conductivity of pellets made with pressed PANI powders was 21 S·cm-1. Yarns were then prepared from the t-Boc-PANI/PVP electrospun membranes followed by PANI protonation to enhance their electrical properties. Using this methodology, electrospun membranes and yarns were produced with electrical conductivities of 1.7 x 10-2 and 4.1 x 10-4 S·cm-1.
Carbon threads sweat-based supercapacitors for electronic textiles
Publication . Lima, Nuno; Baptista, Ana C.; Faustino, Bruno Morais; Taborda, Sofia; Marques, Ana; Ferreira, Isabel; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Nature Publishing Group
Flexible and stretchable energy-storage batteries and supercapacitors suitable for wearable electronics are at the forefront of the emerging field of intelligent textiles. In this context, the work here presented reports on the development of a symmetrical wire-based supercapacitor able to use the wearer's sweat as the electrolyte. The inner and outer electrodes consists of a carbon-based thread functionalized with a conductive polymer (polypyrrole) which improves the electrochemical performances of the supercapacitor. The inner electrode is coated with electrospun cellulose acetate fibres, as the separator, and the outer electrode is twisted around it. The electrochemical performances of carbon-based supercapacitors were analyzed using a simulated sweat solution and displayed a specific capacitance of 2.3 F.g-1, an energy of 386.5 mWh.kg-1 and a power density of 46.4 kW.kg-1. Moreover, cycle stability and bendability studies were performed. Such energy conversion device has exhibited a stable electrochemical performance under mechanical deformation, over than 1000 cycles, which make it attractive for wearable electronics. Finally, four devices were tested by combining two supercapacitors in series with two in parallel demonstrating the ability to power a LED.
Image Recording and Processing Chemical Synthesis
Publication . Sousa, David M.; Carlos Lima, João; Ferreira, Isabel; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; DQ - Departamento de Química; LAQV@REQUIMTE; Wiley
The reproducibility of chemical synthesis is of crucial importance for both chemical industry and research. The development of simple yet robust methods and algorithms that generate a set of data to help the community access their method's reproducibility is desirable. We report a method for obtaining, processing and analyzing recorded images, using scripting language Python 3, from any camera that allows continuous visualization and recording of a chemical synthesis. The method can be used to assert synthesis reproducibility, to capture reaction events that might elude the naked eye and later be isolated in posterior reactions, to refine synthesis parameters such as temperature, microwave power and time and also to understand chemical reactions during synthesis. The method was exemplified with two microwave-assisted synthesis, zinc sulfide and silver sulfide, processed at our lab and applied to videos from other authors.
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Entidade financiadora
European Commission
Programa de financiamento
H2020
Número da atribuição
645241