Produção e caraterização de nanopartículas magnéticas para aplicação biotecnológica

Dissertação de mestrado em Micro e Nano TecnologiasNas últimas décadas têm-se assistido a importantes desenvolvimentos na área dos nanomateriais. Exemplo disso é a crescente aplicação biotecnológica de nanopartículas magnéticas. Para isso, muito contribuiu a aplicação de novos métodos de síntese, que permitiram um controlo profícuo do tamanho, propriedades magnéticas e propriedades da superfície das nanopartículas. Assim sendo, o objectivo deste trabalho foi otimizar um método de síntese de nanopartículas magnéticas, caraterizá-las e aplicar as mesmas – avaliando o seu desempenho. Para sintetizar nanopartículas magnéticas de óxido de ferro foi empregue o método de coprecipitação. A utilização de ácido cítrico como agente estabilizador/surfatante das nanopartículas mostrou-se eficaz, obtendo-se partículas menores e mais estáveis. A caraterização permitiu obter valores para o tamanho das nanopartículas por dispersão dinâmica de luz (21,9 nm), difração de raios-X (17,91 nm) e microscopia eletrónica de transmissão (10 nm). Por difração de raios-X foi ainda possível identificar a estrutura cristalina da amostra e indexá-la à maghemite (ɣ-Fe2O3). A morfologia prismática foi observada por análise das imagens de microscopia eletrónica de transmissão. O estudo da carga superficial das partículas (potencial ζ) revelou que as nanopartículas são pouco estáveis (tendência a aglomerar), sendo que o revestimento da superfície é fundamental para a sua estabilização e aplicação. Na última fase do trabalho, foram produzidas esferas (≈ 400 nm) com nanopartículas aprisionadas em matriz porosa de sílica. Para o efeito foi aplicado o método de Stober combinado com tratamento hidrotermal. Foi usado brometo de cetiltrimetilamónio (CTAB) como agente surfatante e a aplicação do processo hidrotermal (120 °C durante 48 h) assegurou uma boa distribuição de tamanhos das esferas magnéticas porosas de sílica. A morfologia esférica e porosa foi confirmada por microscopia eletrónica de transmissão e por microscopia eletrónica de varrimento. As esferas obtidas foram testadas como adsorventes de catiões de níquel em solução aquosa. Os estudos realizados por espetroscopia de absorção atómica mostraram que 100% do conteúdo de Ni2+ foi removido com sucesso da solução aquosa, sem necessidade de funcionalizar (e.g. quelantes) a superfície da sílica.In the last few decades huge developments were achieved in nanomaterials science. These breakthroughs were in part a consequence of the application of new magnetic nanoparticles production methods, allowing an efficient control of their size, magnetic and surface properties. Therefore, the goal of this work lied on the optimization of synthesis, characterization, and application of magnetic nanoparticles – studying their efficiency. To synthesize iron oxide magnetic nanoparticles it was used the coprecipitation method. Additionally, the application of citric acid proved to be an efficient surfactant, producing smaller and more stable nanoparticles. The size of nanoparticles was accessed by dynamic light scattering (21.09 nm), X-ray diffraction (1791 nm) and transmission electron microscopy (10 nm). X-ray diffraction also allowed the identification of the crystalline structure of the samples and indexing it to maghemite (ɣ-Fe2O3). The prismatic morphology of magnetic nanoparticles was observed trough transmission electron microscopy image analysis. The nanoparticles surface charge (zeta potential) study revealed that nanoparticles are unstable (tend to agglomerate), showing the importance of a coating process to stabilize and allow their efficient application. In the last phase of the work, porous magnetic silica spheres of about 400 nm diameter were synthesized using the classical Stober method combined with hydrothermal treatment. Cetyltrimethylammonium bromide (CTAB) was used as surfactant agent. The application of the hydrothermal process (120 °C during 48h), before the calcination, leaded to formation of homogeneous and narrow size distribution porous magnetic silica spheres. The obtained silica spheres were evaluated as adsorbents for nickel cations in aqueous solution. The results, obtained by atomic absorption spectrometric method, showed that 100% of the Ni2+ content was successfully removed from the aqueous solution without need of functionalizing the silica surface

Development of photocatalytic poly(vinylidenefluoride-trifluoroethylene)/TiO₂ porous membranes

Photocatalysis has become an attractive process to remove contaminants from aquatic environments1. Photocatalysis consists on the use of solar light to generate highly oxidizing species, most often the hydroxyl radical (•OH), to destroy harmful compounds 2. Catalysts are required in this process and, due to its significant oxidizing properties under UV irradiation, TiO2 is the most widely used photocatalyst [ref?=6]. One disadvantage of the UV/photocatalyst process is the fast recombination rate of the electron-hole pairs3. Doping the photocatalysts with other elements is an effective approach to overcome this problem[ref]. Nevertheless, one of the largest drawbacks of the use of photocatalyst particles is the recycling and reutilization of the nanoparticles, which is time consuming and requires expensive processes2. In order to overcome this drawback, TiO2 immobilization in several substrates (e.g. glass, zeolite, silica and ceramic) has been explored. This work reports the optimization and photocatalytic activity of poly(vinylidenefluoride - trifluoroethylene) (PVDF-TrFE)/TiO2 nanocomposites.Work supported by FEDER (FCT), project PEST-C/FIS/UI607/2011 and PEST-C/QUI/UIO686/2011 and Matepro – Optimizing Materials and Processes”, ref. NORTE-07-0124-FEDER-00003

Solar photocatalytic membranes: an experimental and artificial neural network modeling approach for niflumic acid degradation

The presence of contaminants of emerging concern (CEC), such as pharmaceuticals, in water sources is one of the main concerns nowadays due to their hazardous properties causing severe effects on human health and ecosystem biodiversity. Niflumic acid (NFA) is a widely used anti-inflammatory drug, and it is known for its non-biodegradability and resistance to chemical and biological degradation processes. In this work, a 10 wt.% TiO2/PVDF–TrFE nanocomposite membrane (NCM) was prepared by the solvent casting technique, fully characterized, and implemented on an up-scaled photocatalytic membrane reactor (PMR). The photocatalytic activity of the NCM was evaluated on NFA degradation under different experimental conditions, including NFA concentration, pH of the media, irradiation time and intensity. The NCM demonstrated a remarkable photocatalytic efficiency on NFA degradation, as efficiency of 91% was achieved after 6 h under solar irradiation at neutral pH. The NCM proved effective in long-term use, with maximum efficiency losses of 7%. An artificial neural network (ANN) model was designed to model NFA’s photocatalytic degradation behavior, demonstrating a good agreement between experimental and predicted data, with an R2 of 0.98. The relative significance of each experimental condition was evaluated, and the irradiation time proved to be the most significant parameter affecting the NFA degradation efficiency. The designed ANN model provides a reliable framework l for modeling the photocatalytic activity of TiO2/PVDF-TrFE and related NCM.This research was funded by Fundação para a Ciência e Tecnologia (FCT) grant numbers SFRH/BD/122373/2016 and COVID/BD/151786/2021 and contract 2020.02802.CEECIND.This work was supported by Solar Equipment Development Unit (UDES) and Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Projects UID/FIS/04650/20132019 and UID/QUI/50006/2019 and project PTDC/FIS-MAC/28157/2017. H. Salazar and P. M. Martins thank the FCT for the grants SFRH/BD/122373/2016 and COVID/BD/151786/2021, and the contract 2020.02802.CEECIND. Financial support from the Basque Government Industry and Education Departments under the ELKARTEK program is also acknowledged

Combustion instability and ash agglomeration in wood pellets boiler

The combustion instability and ash agglomeration in a wood pellet boiler were investigated in this study. The tests were conducted using the Taguchi method of orthogonal array L27(133). Several parameters are applied, including grate area (GA), primary to secondary air split ratio (SR), excess air (EA), and fuel power (P). Pine wood pellets were used, and the boiler’s nominal load was 20 kW. The results show that instability during combustion occurs since the fuel bed rises as the accumulation of the unburned wood pellets on the grate causes a slow combustion rate and pressure drop, which creates noise and disturbances. A good combination of the parameters applied to TN9 and TN20 can be useful in obtaining stable combustion. In addition, the ash agglomerations were influenced by the duration of the combustion and the temperature of the fuel bed. The largest size of the ash agglomeration was referred to as test number-TN26 (P: 16 kW, EA: 110%, SR: 30/70, and GA: 115 mm × 75 mm), which is 59 mm, and the duration time is 14,400 s (≈4 h).This work has been supported by FCT—Fundação para a Ciência e Tecnologia within the R&D Units, MEtRICs Project Scope: UIDB/04077/2020; Lelis Fraga was supported through a PhD Grant by Fundo de Desenvolvimento Capital Humano of the Government of Timor Leste

Preliminary chemical data from basaltic rocks dredged at Great Meteor, Hyeres and Plato seamounts

The seafloor near the Azores archipelago and the southern seamounts are still greatly unexplored. Cruise EMEPC/Açores/G3/2007 was planned to collect geological and geophysical data for the Portuguese Proposal for the Extension of the Continental Shelf under the United Nations Convention on the Law of the Sea (UNCLOS) along a track from the Azores to the Great Meteor seamount. Over 40 dredge operations were performed and a significant volume of cemented carbonate rocks, sedimentary and volcanic breccias, as well basaltic rocks were recovered. Major and trace element data is now available for basalts samples from Great Meteor, Hyeres, and Plato seamounts. In the TAS diagram most samples plot in the basalt or basanite fields above the subalkaline and alkaline divide from Irvine & Baragar (1971). Basaltic rocks are undersaturated (with normative nepheline), relatively unfractionated (MgO normally higher than 5%) and present TiO2 contents higher than 3 wt% typical of OIB lavas. Ratios between incompatible elements (e.g. Ba/Rb, Ba/Th, Ba/Nb) point to the existence of source heterogeneities that will be better constrained by isotopic data. La/Ybn ratios, ranging from 8 to 14, require fractionation of REE during melting in the presence of residual garnet and its increase towards the Great Meteor seamount suggests a dependence of melting with the lithosphere thickness. Comparing REE ratios as (La/Sm)n from the seamounts with the ones found in the Azores islands of Faial, Pico and São Jorge, we find no significant variation with latitude

Enhanced photocatalytic activity of Au/TiO2 nanoparticles against ciprofloxacin

In the last decades, photocatalysis has arisen as a solution to degrade emerging pollutants such as antibiotics. However, the reduced photoactivation of TiO2 under visible radiation constitutes a major drawback because 95% of sunlight radiation is not being used in this process. Thus, it is critical to modify TiO2 nanoparticles to improve the ability to absorb visible radiation from sunlight. This work reports on the synthesis of TiO2 nanoparticles decorated with gold (Au) nanoparticles by deposition-precipitation method for enhanced photocatalytic activity. The produced nanocomposites absorb 40% to 55% more radiation in the visible range than pristine TiO2, the best results being obtained for the synthesis performed at 25 °C and with Au loading of 0.05 to 0.1 wt. %. Experimental tests yielded a higher photocatalytic degradation of 91% and 49% of ciprofloxacin (5 mg/L) under UV and visible radiation, correspondingly. Computational modeling supports the experimental results, showing the ability of Au to bind TiO2 anatase surfaces, the relevant role of Au transferring electrons, and the high affinity of ciprofloxacin to both Au and TiO2 surfaces. Hence, the present work represents a reliable approach to produce efficient photocatalytic materials and an overall contribution in the development of high-performance Au/TiO2 photocatalytic nanostructures through the optimization of the synthesis parameters, photocatalytic conditions, and computational modeling.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the strategic projects UID/FIS/04650/2013 by Fundo Europeu de Desenvolvimento Regional (FEDER) funds through the COMPETE 2020—Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941, project PTDC/CTM-ENE/5387/2014, as well as UID/BIO/04469 unit through COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte. P.M. Martins thanks the FCT for the grant SFRH/BD/98616/2013 and Luciana Pereira for the grant SFRH/BPD/110235/2015. M. Melle-Franco would like to acknowledge support from Centro de Investigação em Materiais Cerâmicos e Compósitos (CICECO)—Aveiro Institute of Materials, POCI-01-0145-FEDER007679 (UID/CTM/50011/2013) and the FCT (IF/00894/2015).info:eu-repo/semantics/publishedVersio

Morphology dependence degradation of electro- and magnetoactive poly(3-hydroxybutyrate-co-hydroxyvalerate) for tissue engineering applications

Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) is a piezoelectric biodegradable and biocompatible polymer suitable for tissue engineering applications. The incorporation of magnetostrictive cobalt ferrites (CFO) into PHBV matrix enables the production of magnetically responsive composites, which proved to be effective in the differentiation of a variety of cells and tissues. In this work, PHBV and PHBV with CFO nanoparticles were produced in the form of films, fibers and porous scaffolds and subjected to an experimental program allowing to evaluate the degradation process under biological conditions for a period up to 8 weeks. The morphology, physical, chemical and thermal properties were evaluated, together with the weight loss of the samples during the in vitro degradation assays. No major changes in the mentioned properties were found, thus proving its applicability for tissue engineering applications. Degradation was apparent from week 4 and onwards, leading to the conclusion that the degradation ratio of the material is suitable for a large range of tissue engineering applications. Further, it was found that the degradation of the samples maintain the biocompatibility of the materials for the pristine polymer, but can lead to cytotoxic effects when the magnetic CFO nanoparticles are exposed, being therefore needed, for magnetoactive applications, to substitute them by biocompatible ferrites, such as an iron oxide (Fe3O4).This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2020, UID/BIO/04469/2020 and UID/QUI/00686/2020, and projects PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017 and Associate Laboratory for Green Chemistry—LAQV, financed by national funds from FCT/MCTES (UIDB/50006/2020). The authors also thank the FCT for the SFRH/BPD/121526/2016 (DMC) grant. The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively.info:eu-repo/semantics/publishedVersio

Photocatalytic activity of TiO2/graphene and TiO2/graphene oxide nanocomposites

Semiconductor-based heterogeneous photocatalysis has been one of the most promising processes for the treatment of contaminated water. Among the available catalysts, titanium dioxide (TiO2) presents the best photocatalytic properties, being chemically and biologically inert, stable, non-toxic, cheap and easy to produce. However, its energy bang gap lies in the ultraviolet (UV) range, which is responsible for a reduced spectral activation, since UV radiation corresponds to only 5% of the solar spectrum [1]. For this reason, one of the main purposes of the scientific community has been to improve the photocatalytic performance of TiO2, namely through an adequate doping of this material, or through the creation of nanocomposites, to enable photocatalysis occurrence by the incidence of visible light. One alternative concerns the application of nanocomposites of TiO2 with graphene and graphene oxide to photocatalytic processes [2]. In this work, nanocomposites of TiO2 with different weight concentrations of graphene and graphene oxide (namely 0.5%, 1%, 1.5% and 3%) were synthetized by a one-step hydrothermal method and characterized in terms of morphology, crystalline structure, vibrational modes and optical band gap. The photocatalytic activity of these nanocomposites was then evaluated through the degradation of methylene blue and ciprofloxacin solutions under UV and visible radiation. The results indicated that the studied nanocomposites presented higher degradation rates of the methylene blue than the pure TiO2, which increased with the content of graphene/graphene oxide. However, these composites proved to be less suitable to degrade the ciprofloxacin solution than the pure TiO2 nanoparticles.Portuguese Foundation for Science and Technology (FCT) - UID/FIS/04650/2013, PTDC/CTM-ENE/5387/2014 and SFRH/BD/98616/2013; Basque Government Industry Department under the ELKARTEK Program.info:eu-repo/semantics/publishedVersio

Environmental impact of nanomaterials: assessment of toxicity in chemical and biological processes for the degradation of micropollutants.

This study was supported by FCT under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norteinfo:eu-repo/semantics/publishedVersio

Thrombus aspiration in patients with ST-elevation myocardial infarction: results of a national registry of interventional cardiology

BACKGROUND: We aimed to evaluate the impact of thrombus aspiration (TA) during primary percutaneous coronary intervention (P-PCI) in 'real-world' settings. METHODS: We performed a retrospective study, using data from the National Registry of Interventional Cardiology (RNCI 2006-2012, Portugal) with ST-elevation myocardial infarction (STEMI) patients treated with P-PCI. The primary outcome, in-hospital mortality, was analysed through adjusted odds ratio (aOR) and 95% confidence intervals (95%CI). RESULTS: We assessed data for 9458 STEMI patients that undergone P-PCI (35% treated with TA). The risk of in-hospital mortality with TA (aOR 0.93, 95%CI:0.54-1.60) was not significantly decreased. After matching patients through the propensity score, TA reduced significantly the risk of in-hospital mortality (OR 0.58, 95%CI:0.35-0.98; 3500 patients). CONCLUSIONS: The whole cohort data does not support the routine use of TA in P-PCI, but the results of the propensity-score matched cohort suggests that the use of selective TA may improve the short-term risks of STEMI..info:eu-repo/semantics/publishedVersio