New Polymeric films for Smart Windows with Permanent Memory Effect

In the field of the liquid crystals in device applications, the polymer dispersed liquid crystal (PDLC) with permanent memory effect can become feasible in technological applications. Although studies of the liquid crystals in technological applications were extensively reviewed in the literature, not so much has been reported on the permanent memory effect (PME) in PDLCs. PDLCs can change transmittance from a totally opaque state to a totally transparent state during the application of an external electric field. Typically, the opaque appearance returns to the PDLC when the electric field is switched OFF. However, in this work PDLCs have been produced that use the electric field to create a highly transparent state but the transparent state remains even when the electric field is switched OFF giving rise to a permanent alignment state of LC molecules. This property is called a permanent memory effect (PME). For optimizing this effect a series of linear polyethylene glycol di(meth)acrylate and multi-arm polyethylene glycol with linear chains arms extending radially from a central core with reactive (meth)acrylate end groups were synthesized and characterized. The resulting pre-polymers and also some commercial ones were then tested in preparation of PDLCs. The 70 % of PME and the reproducibility even after multiple repetitions of the heating and electric field cycles application make the poly(ethyleneglycol) dimethacrylate of molecular weight 875 g mol-1 the most appropriate pre-polymer in preparation of PDLCs with PME. This effect is also dependent on the thermal polymerization which produces a polymer ball morphology type in the polymer matrix. In addition, PME is also highly dependent on the alignment layer type coating the glass PDLC cell (homogeneous alignment). With the high transparent state permanently displayed at room temperature through PME (70 %), an efficient procedure to allow the PDLC to acquire its opaque state has been achieved. A method of removing the PME has been outlined by Joule effect with the application of the electric current to the conductive layer (ITO) of the glass PDLC cell. This procedure makes the experimental setup to destroy the LC alignment structure simpler and more practical than by radiation heat. Conventional PDLCs need continuity of energy supply for keeping the ON state, which can be a very limiting aspect for many applications. However, PDLCs with PME besides having lower power consumption can be used in digital memory devices based on write-read-erase cycles. For this, a prototype has been assembled as proof of the concept to be used in the digital process of recording information with the binary language

Selective synthesis under microwave irradiation of new monomers for potential applications in PDLC films

Dissertation to obtain the degree of master in BioorganicPolymer dispersed liquid crystal (PDLC) films consist, commonly, on nematic liquid crystal domains dispersed in a polymeric matrix. These composites can be switched electrically from an opaque scattering state to a highly transparent state by an applied electric field. The molecular structure of the polymerisable monomers that can be incorporated as polymeric matrix plays an important role in the performance of PDLCs. Therefore, the aims of this work were to design and synthesise several new monomers that could be polymerised photochemically and thermally to be incorporated as polymeric matrices in PDLCs and investigate the influence of the molecular structure on the performance of these devices. Several monomers were synthesised in order to achieve better miscibility between the liquid crystal and the monomers during preparation of PDLC films. For this purpose, the monomers were synthesised so as to mimic some structural elements of the E7 liquid crystal molecules. Thus, several aromatic mono- and dimethacrylates with and without a linear chain spacer with five methylene units, as well as vinylic monomers were successfully synthesised. Mild and solvent freeprocedures were developed with reaction times as short as 1 to 5 min, using microwave irradiation. The structures of all isolated monomers were supported by 1H NMR, 13C NMR and FTIR spectroscopy, elemental analysis and melting point. Of all the synthesised monomers, the monomers that included in their structure aromatic rings bearing a cyano group and/or a linear chain spacer with five methylene units were fully characterised due to their higher molecular structure affinity with the E7 liquid crystal molecules. In order to evaluate the effect of these groups, these monomers were compared with those of similar structure but without the respective groups. Thus, DSC and POM with temperature ramps were used for the thermal characterisation of the monomers. The structural morphologies of the polymeric matrices were characterised by SEM. The monomers were also copolymerised with glycidyl methacrylate and the molecular weights of the resulting polymers were evaluated by GPC. The electro-optical properties of the PDLC films were determined by measuring the voltage dependence on the transmitted light.Fundação para a Ciência e Tecnologia - Project PTDC/CTM/69145/200

Estudos de adsorção de fluoxetina por carvões activados antes e após modificação química

O estudo cinético realizado demonstrou que o equilíbrio é rapidamente atingido, na maioria dos casos após 60 minutos de contacto, pelo que se considerou um tempo óptimo de 120 minutos para realizar os ensaios de adsorção. Os materiais de carbono testados apresentam uma vasta gama de características com ponto de carga zero entre 3 e 12, área aparente BET (ABET) entre 780 e 2500m2/g e volume poroso (Vp, determinado pelo método s) entre 0.3 e 1.1cm3/g. Na generalidade dos casos a quantidade adsorvida a pH=7.5 é maior do que a adsorvida a pH=1.2 devido às interacções electroestáticas entre a molécula da fluoxetina, que aos valores de pH referidos está na forma ionizada e portanto com carga positiva, e a carga média da superfície que é sempre mais favorável a pH=7.5. Ao comparar adsorventes com valores aproximadamente iguais de ponto de carga zero (pcz) podemos verificar que o volume poroso determina nestes casos a capacidade máxima de adsorção, por exemplo Carbomix vs Maxsorb30. Podemos também verificar que a capacidade máxima de adsorção aumenta à medida que o valor de pcz dos materiais diminui. Os ensaios demonstraram que os materiais testados possuem potencial para efectuarem a adsorção da fluoxetina tendo-se conseguido obter quantidades adsorvidas superiores aos referenciados na literatura. Podemos também concluir que as fibras de carbono activadas utilizadas possuem um comportamento distinto do observado para as amostras de carvões activados, nomeadamente no que diz respeito à influência das interacções electrostáticas na adsorção de fluoxetina. Aparentemente no caso dos carvões activados o mecanismo de adsorção depende em maior escala deste tipo de interacções enquanto que no caso das fibras de carbono activadas e factor mais relevante será as interacções de natureza dispersiva. A modificação dos carvões activados por oxidação leva a um incremento da quantidade máxima adsorvida de fluoxetina justificado pela natureza ácida da mesma

Um estudo em tempo de pandemia

UIDB/04647/2020 UIDP/04647/2020Oartigo apresentaalguns resultados de um estudo desenvolvido pela primeira autora no âmbito do Mestrado em Educação Pré-Escolar da Escola Superior de Educação do Instituto Politécnico de Setúbal, realizado emcontextode estágioacadémico, durante o tempo da pandemia. O estudo teve como foco o envolvimento das famílias em creche e jardim de infância, com a finalidade de compreender como se pode promover o envolvimento das famíliase quais as estratégias postas em prática pelas educadorascooperantes.Baseia-se numametodologia qualitativa, orientada pelos princípios da investigação-ação, tendo sido utilizadosdiferentes procedimentosde recolha de informações, taiscomo a observação participante, notas de campo, registo fotográfico e inquérito por questionárioàs educadoras.Resultante do envolvimentodas famílias no contexto educativo, identificam-se múltiplos benefícios para as crianças, famílias e equipa pedagógica. | The article presents some results of a study developed within the scope of the Masters in Pre-School Education at School of EducationofPolitécnicInstitute ofSetúbal, carried out in the context of academic internshipduring the time of the pandemic. The study was focused onthe involvement of families in nursery centersand kindergartens, in order to understand howto promote the involvement of families and what strategies are put into practice by the cooperating educators. It is based on a qualitative methodology, guided bythe principles of action-research, having used different procedures for collecting information, such as participant observation, field notes, photographic records and questionnaire surveys to educators.As a result of the involvement of families in the educational context, multiple benefits are identified for children, families and the pedagogical team.publishersversionpublishe

Slow pyrolysis of cork granules under nitrogen atmosphere: by-products characterization and their potential valorization

ABSTRACT: Cork granules (Quercus suber L.) were slowly pyrolyzed at temperatures between 400-700 degrees C and under N-2 flow. While preserving its structure, some cells of the cork biochar became interconnected, allowing such carbon residue to be used as templates for manufacturing ceria redox materials. The pyrolytic char morphology was similar to that of the natural precursor. The produced cork biochar belonged to Class 1 (C > 60%) and possessed a high heating value of 32 MJ kg(-1). Other pyrolysis-derived compounds were identified and quantified through GC-FID and GC-MS analyses. The yield of gases released during cork pyrolysis was strongly dependent on the temperature used due to the thermal decomposition reactions involved in the degradation of cork. In particular, rising pyrolysis temperature from 500 to 700 T resulted in reducing the total hydrocarbon gases from 74 to 24 vol%. On the other hand, the yield of H-2 increased from 0 to 58% by increasing the pyrolysis temperature from 400 to 700 T. Due to the presence of suberin in cork, the composition and yield of bio-oil could be regulated by the pyrolysis temperature. Cork bio-oil was found to consist of long-chain hydrocarbons (from C11 to C24). The bio-oil resulting from the slow pyrolysis of cork residues is suitable as an appropriate feedstock for producing aliphatic-rich pyrolytic biofuels or as a source of olefms. Overall, the findings of this study suggest that Quercus suber L. could be a promising feedstock for biochar and biofuel production through the pyrolytic route and could contribute to the environmental and economic sustainability of the cork production industry.info:eu-repo/semantics/publishedVersio

In vitro adsorption study of fluoxetine in activated carbons and activated carbon fibres

We study the in vitro adsorption of fluoxetine hydrochloride by different adsorbents in simulated gastric and intestinal fluid, pH 1.2 and 7.5, respectively. The tested materials were two commercial activated carbons, carbomix and maxsorb MSC30, one activated carbon fibre produced in our laboratory and also three MCM-41 samples, also produced by us. Selected samples were modified by liquid phase oxidation and thermal treatment in order to change the surface chemistry without significant modifications to the porous characteristics. The fluoxetine adsorption follows the Langmuir model. The calculated Q0 values range from 54 to 1112 mg/g. A different adsorption mechanism was found for the adsorption of fluoxetine in activated carbon fibres and activated carbons. In the first case the most relevant factors are the molecular sieving effect and the dispersive interactions whereas in the activated carbons the mechanism seams to be based on the electrostatic interactions between the fluoxetine molecules and the charged carbon surface. Despite the different behaviours most of the materials tested have potential for treating potential fluoxetine intoxications

Colloidal lithography for photovoltaics: An attractive route for light management

DFA/BD/7882/2020The pursuit of ever‐more efficient, reliable, and affordable solar cells has pushed the development of nano/micro‐technological solutions capable of boosting photovoltaic (PV) performance without significantly increasing costs. One of the most relevant solutions is based on light management via photonic wavelength‐sized structures, as these enable pronounced efficiency improvements by reducing reflection and by trapping the light inside the devices. Furthermore, optimized microstructured coatings allow self‐cleaning functionality via effective water repulsion, which reduces the accumulation of dust and particles that cause shading. Nevertheless, when it comes to market deployment, nano/micro‐patterning strategies can only find application in the PV industry if their integration does not require high additional costs or delays in high‐throughput solar cell manufacturing. As such, colloidal lithography (CL) is considered the preferential structuring method for PV, as it is an inexpensive and highly scalable soft‐patterning technique allowing nanoscopic precision over indefinitely large areas. Tuning specific parameters, such as the size of colloids, shape, monodispersity, and final arrangement, CL enables the production of various templates/masks for different purposes and applications. This review intends to compile several recent high‐profile works on this subject and how they can influence the future of solar electricity.publishersversionpublishe

Soft-Microstructured Transparent Electrodes for Photonic-Enhanced Flexible Solar Cells

H2020-LCE-2017-RES-RIA DFA/BD/7882/2020Microstructured transparent conductive oxides (TCOs) have shown great potential as photonic electrodes in photovoltaic (PV) applications, providing both optical and electrical improvements in the solar cells’ performance due to: (1) strong light trapping effects that enhance broadband light absorption in PV material and (2) the reduced sheet resistance of the front illuminated contact. This work developed a method for the fabrication and optimization of wavelength-sized indium zinc oxide (IZO) microstructures, which were soft-patterned on flexible indium tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) substrates via a simple, low-cost, versatile, and highly scalable colloidal lithography process. Using this method, the ITO-coated PET substrates patterned with IZO micro-meshes provided improved transparent electrodes endowed with strong light interaction effects—namely, a pronounced light scattering performance (diffuse transmittance up to ~50%). In addition, the photonic-structured IZO mesh allowed a higher volume of TCO material in the electrode while maintaining the desired transparency, which led to a sheet resistance reduction (by ~30%), thereby providing further electrical benefits due to the improvement of the contact conductance. The results reported herein pave the way for a new class of photonic transparent electrodes endowed with mechanical flexibility that offer strong potential not only as advanced front contacts for thin-film bendable solar cells but also for a much broader range of optoelectronic applications.publishersversionpublishe

Optically-Boosted Planar IBC Solar Cells with Electrically-Harmless Photonic Nanocoatings

Funding Information: This work received funding from the FCT (Fundação para a Ciência e Tecnologia, I.P.) under the projects LA/P/0037/2020, UIDP/50025/2020 and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodeling, and Nanofabrication—i3N, and by the projects TACIT (PTDC/NAN‐OPT/28837/2017) and FlexSolar (PTDC/CTM‐REF/1008/2020). The authors also acknowledge the support of the H2020 Solar‐ERANET program, which funded the development of the IBC cells within the framework of the BOBTANDEM project. The work was also funded by the European Union's Horizon 2020 research and innovation program under the project Synergy (H2020‐Widespread‐2020‐5, CSA), proposal n° 952169. M.A. and J.B. acknowledge funding by FCT‐MCTES through the grants SFRH/BD/148078/2019 and BD/14557/2022, respectively. Publisher Copyright: © 2023 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH.Advanced light management via front-coated photonic nanostructures is a promising strategy to enhance photovoltaic (PV) efficiency through wave-optical light-trapping (LT) effects, avoiding the conventional texturing processes that induce the degradation of electrical performance due to increased carrier recombination. Titanium dioxide (TiO2) honeycomb arrays with different geometry are engineered through a highly-scalable colloidal lithography method on flat crystalline silicon (c-Si) wafers and tested on standard planar c-Si interdigitated back-contact solar cells (pIBCSCs). The photonic-structured wafers achieve an optical photocurrent of 36.6 mA cm−2, mainly due to a broad anti-reflection effect from the 693 nm thick nanostructured coatings. In contrast, the pIBCSC test devices reach 14% efficiency with 679 nm thick TiO2 nanostructures, corresponding to a ≈30% efficiency gain relative to uncoated pIBCSCs. In addition, several designed structures show unmatched angular acceptance enhancements in efficiency (up to 63% gain) and photocurrent density (up to 68% gain). The high-performing (yet electrically harmless) LT scheme, here presented, entails an up-and-coming alternative to conventional texturing for c-Si technological improvement that can be straightforwardly integrated into the established PV industry.publishersversionpublishe