Novel magnetic materials : from coordination compounds to nanomaterials

Doutoramento em QuímicaA presente tese aborda a síntese de unidades finitas de complexos do tipo metal-ligando e polímeros de coordenação infinitos, a síntese e modificação superficial de nanopartículas de magnetite, bem como o fenómeno de magnetismo observado nestes materiais. São também investigadas as várias possibilidades de coordenação de ligandos, com determinados tamanhos e formas, a metais de estrutura electrónica única, obtendo-se assim novas estruturas de tamanhos e dimensionalidades diferentes, e como as propriedades magnéticas são alteradas. Os resultados de magnetismo neste trabalho são interpretados do ponto de vista da magnetoquímica. O Capítulo 1 é uma breve introdução à química dos metais de transição e mostra a correlação entre a estrutura e as propriedades magnéticas. Neste capítulo foi feita também uma revisão de compostos de coordenação magnéticos importantes e a descrição dos fenómenos fundamentais de magnetismo. No Capítulo 2 é explorada a química de coordenação dos ligandos ambidentados derivados dos ácidos piridina-carboxílicos para síntese de novos complexos de metais de transição. As estruturas e propriedades magnéticas duma série de novos compostos foram investigadas. O Capítulo 3 consiste na descrição de polímeros de coordenação com lantanídeos (Eu3+, Tb3+, Sm3+) com a presença simultânea na estrutura dum ligando aromático quelato (ácido picolínico) e um ligando de ponte flexível (acido glutárico). Foram estudadas as propriedades estruturais, luminescentes e magnéticas. O Capítulo 4 descreve o comportamento magnético de híbridos orgânicoinorgânicos com ácido N-(fosfonometil)iminodiacético e metais da 1ª série de transição. A investigação abordada no Capítulo 5 relaciona-se com a modificação superficial e a funcionalização das nanopartículas ferrimagnéticas de magnetite (Fe3O4). Foi feito o estudo das possibilidades de aplicar estes últimos materiais na remoção de iões de metais pesados em águas poluídas. No Capítulo 6 são generalizadas as conclusões deste trabalho. Detalhes da parte experimental e das técnicas de caracterização podem ser consultadas no Capítulo 7.The research in this thesis is focused on the synthesis of bulk finite units of metal-ligand complexes and infinite coordination polymers as well as the synthesis and surface modification of Iron oxide nanoparticles. Subject of study is the magnetic phenomena raised in those materials. This is a research of the possibilities of the ligands with such size and shape that makes them able to trap a metal with unique electronic structure and build the new molecular assemblies with different structures, dimensionalities and sizes and of the study if / how the magnetic phenomena changes. The magnetic results in this work are interpreted in the frame of magnetochemistry. Chapter 1 is an introduction to transition metals chemistry and correlation between structure and magnetic properties. It contains a short review of the existing magnetic coordination compounds and a description of some fundamentals in magnetism. Also some basic magnetic properties and correlations are explained. In Chapter 2 the coordination chemistry of derivatives of pyridine-carboxylic acids as ambidentate ligands is exploited to synthesize a series of transition metal complexes. Novel coordination compounds were synthesized and in particular their structures and magnetic properties are described. In Chapter 3 is discussed the simultaneous presence of a chelating aromatic ligand (picolinic acid) and a highly flexible bridging ligand (glutaric acid) in lanthanide-organic coordination polymers with Eu3+, Tb3+, Sm3+. The structural, luminescent and magnetic properties are studied. In Chapter 4 the magnetic behaviour of organic-inorganic hybrids with the multidentate chelating ligand N-(phosphonomethyl)iminodiacetic acid and 1st row transition metals were investigated. In Chapter 5 is described the surface modification and functionalization of ferrimagnetic magnetite (Fe3O4) nanoparticles and their application for removal of heavy meals in waste waters. Conclusions from this work are generalized in Chapter 6. In Chapter 7 can be seen details about the experimental part and the characterization techniques

Poly[bis(2,2′-bipyridine-κ2 N,N′)heptadeca-μ-oxido-tetraoxidodicopper(II)divanadate(IV)hexavanadate(V)]

In the title complex, [Cu2V8O21(2,2′-bpy)2]n (bpy = bipyridine, C10H8N2), the asymmetric unit contains four independent V atoms briged by 11 O atoms, one of which lies on an inversion center, and a [Cu(2,2′-bpy)]2+ unit. Three V atoms in the polyoxoanion exhibit distorted tetra­hedral coordination geometries while the fourth V atom adopts a trigonal-bipyramidal geometry. The Cu atom adopts a square-pyramidal geometry being coordinated by two nitro­gen donors of a 2,2′-bpy ligand, and three bridging O atoms which are linked with V atoms. The V8 polyoxoanion is connected to [Cu(2,2′-bpy)]2+ cations, resulting in a two-dimensional layer structure extending parallel to (010). C—H⋯O hydrogen bonding consolidates the structure

Desenvolvimento de novos materiais com propriedades biocidas para aplicação como consolidantes em Património

Estudos recentes em conservação e restauro têm visado a definição das etapas e das técnicas de intervenção no património cultural. As tendências atuais de investigação confirmam que a perda de coesão das argamassas históricas, por efeito da dissolução do ligante e/ou de destruição da estrutura porosa, é uma evidência frequente em superfícies arquitetónicas antigas. A etapa de consolidação surge como uma das principais fases de intervenção nos revestimentos históricos e, enquanto técnica de intervenção, a aplicação de consolidantes tem adquirido bastante interesse para o campo da investigação. Neste contexto, a aposta em consolidantes inorgânicos tem ganho terreno e assenta no facto de serem altamente compatíveis com os suportes e apresentarem baixo custo , o que representam vantagens quando comparados com os consolidantes de natureza orgânica. Contudo, a fraca eficácia registada no uso da água de cal e no silicato de etilo tem justificado, ao longo dos anos, o aparecimento de outras alternativas como as dispersões em álcool de nanopartículas de cal. O projeto de desenvolvimento de novos materiais com propriedades biocidas para aplicação como consolidantes em Património Cultural, realizado no Laboratório HERCULES, no âmbito do projeto de estágio da licenciatura em Biotecnologia, teve o propósito de desenvolver métodos de preparação e otimizar as condições de síntese de nanomateriais visando a sua potencial aplicação como consolidantes em substratos de argamassas de cal. O estudo que aqui se apresenta consistiu na preparação de vários tipos de materiais, nomeadamente, materiais inorgânicos, hidróxido de cálcio (Ca(OH)2), materiais híbridos preparados pelo método sol-gel a partir de alcóxidos de silício e de titânio (Si(OEt)4 e Ti(OPri)4), e materiais híbridos preparados pelo método sol-gel modificado preparados igualmente a partir dos alcóxidos de silício e titânio e usando n-octilamina como surfactante. Adicionalmente foram realizados ensaios que permitiram avaliar a eficácia dos materiais preparados como biocidas.SFRH/BPD/97692/2013 (FCT

Micro- and nanoparticles based on alkali-earth metal hydroxides for cultural heritage conservation

Wall renders are subject of constant aging and deterioration and they therefore need repair and treatment. The polymers used in the past for consolidation show many drawbacks and often accelerate the deterioration. This implies the need of new non-toxic materials, preferably of the same composition as the original art work, compatible, with long-term efficiency, without side effect, easy for application. Different inorganic materials have been proposed. The lime-based materials are convenient but not efficient enough, so that different approaches to enhance their efficiency must be found. Nanomaterials exhibit distinct properties when compared to their bulk analogues and have been seen as a good alternative of compatible materials for long term preservation [1]. In this context our research intends to study and optimize successful preparative strategies of micro- and nanolimes, and to improve their efficiency in the inhibition of the degradation process and in the consolidation of wall renders and stone [2,3]. The work is focused on the innovation of the tradition lime materials towards long-term efficiency and compatibility with the surfaces of original works, taking into account environmental and human risk factors. In this communication we report the synthesis and characterization of micro- and nanoparticles based on alkali-earth metal hydroxides for cultural heritage conservation. We discuss synthetic strategies applied and optimum preparative conditions, such as temperature, synthesis duration, addition of surfactant and others, in order to obtain well defined functional magnesium and calcium hydroxides nanoparticles. The composition, morphology and crystallinity are analysed mainly by microscopical techniques and by X-ray powder diffraction. Additional structural and chemical data are collected with other common techniques: Energy Dispersive X-Ray Spectrometry, micro-FTIR, micro-Raman, simultaneous thermal analysis (TGA/DTA) among others, when needed. We also discuss the laboratory tests conducted to assess the efficiency of the nanolimes on mortar specimens (porosity, dynamic elastic modulus, compressive and flexural mechanical behaviour) and the feasibility of their application. References: [1] Baglioni P., Carretti E., Chelazzi D., Nature Nanotechnology 10, Apr 2015, 287-290. [2] Girginova, P.I.; Galacho, C.; Mirão, J.; Veiga, R.; Silva, A.S.; Candeias, A., Conservar património 23, 2016, 103-107. [3] Borsoi, G.; Lubellia, B.; van Hees, R.; Veiga, R.; Silva, A.S.; J. Cult Herit. 18, 2016, 242

Nanoconsolidants for lime mortars of wall paintings as a good alternative of traditional consolidants

Carbonate stones and wall paintings, as an irremovable part of the architectural heritage, are subject to constant attack by soluble salts and pollutants. They can undergo different kinds of degradation, including corrosion by acid rain, physical erosion, cycles of salts crystallization/solubilization and biodegradation due to bacteria, fungi or lichens. Often, past treatments tend to cause additional substrate damages. For instances, synthetic polymeric materials applied for work of art restoration as consolidants, protectives, adhesives or cleaning agents, initially were seen as a good treatment alternative. However, upon ageing they are subject to degradation which results in cross-linking or chain scission which consequently alter their own initial properties and accelerate the decay of the artwork by changing its physicochemical properties. Nanoconsolidants exhibit distinct properties when compared to their bulk analogues, and for the last decade have been seen as a good alternative of compatible materials for long term preservation of Cultural Heritage.[1,2] A highly efficient consolidant for stone or mortar must meet a large list of requisites: must be effective for long-term, be compatible with the damaged substrate, to induce mechanical improvement and protection from weathering to the material, among others. The application of micro- and nanoparticles (NPs) based on alkali-earth metal hydroxides for cultural heritage conservation has become more relevant, mainly for consolidation of historic lime mortars, biocalcarenite stone and for cellulose materials deacidification purposes. Our research intends to propose successful preparative strategies of sub-micro and nanolimes, and to study their efficiency in the inhibition of the degradation process and in the consolidation of wall renders. In this communication an overview of the main synthesis strategies to prepare nanoconsolidants for restoration of Cultural Heritage is carried out. We also report our attempts to develop nanoconsolidants based on alkali-earth metal hydroxides for lime mortars of wall paintings. Furthermore, we discuss their effectiveness for the improvement of the mechanical properties of lime mortars. [1] Baglioni, P.; Carretti, E.; Chelazzi, D., Nature Nanotechnology 2015, 10, 287. [2] Girginova, P. I.; Galacho, C.; Veiga, R.; Santos Silva, A.; Candeias, A., ChemSusChem 2018, 11, 4168.Post-doctoral grant (P.G.) SFRH/BPD/97692/201

Preliminary Studies of the Effects of Nanoconsolidants on Mural Paint Layers with a Lack of Cohesion

This paper reports the preliminary results of a comparative analysis of the effects of three consolidants on the color appearance of fresco paint layers affected by lack of cohesion. In vitro assays were performed with a laboratory-synthesized nanolime, a commercial nanolime (CaLoSiL® IP25), and a commercial acrylic resin (PrimalTM SF-016 ER®) applied by nebulization over two sets of replicas of buon and lime fresco painted with red and yellow ochres and smalt pigments. The paint layers were surveyed before, one week, and one month after treatment with technical photography in the visible range (Vis) and ultraviolet-induced fluorescence in the visible range (UVF), as well as optical microscopy (OM-Vis), colorimetry, spectrophotometry, and scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM-EDS). Experimental work also comprised the synthesis of nanolime and its characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetry analysis (TGA-DTG). The results show no alteration on pigments’ spectral curves and elemental composition. The increase in the CIEL* coordinate and ∆E color variation noticed after the treatment with the nanolimes is associated with a white haze formation on the paint surfaces. The impact on color appearance is higher on the darker tones.Fundação para a Ciência e a Technologia FCT, Portugal (the Portuguese national funding agency for science, research and technology): UIDB/04449/2020; UIDP/04449/2020; DL 57/2016/CP1372/CT0013; DL/57/2016/CP1338. EMJMD ARCHMAT, co-founded by Erasmus+ program under GA N. 2018-1468/001-00

Os nanomateriais na conservação do Património Cultural: Nanocais para suportes de pinturas murais

Nas últimas décadas os nanomateriais têm sido vistos como uma boa alternativa de materiais para a preservação do Património Cultural [1], nomeadamente, como consolidantes de pedra e de argamassas de cal. Estes materiais apresentam propriedades distintas quando comparados com os tradicionais. O trabalho que tem vindo a ser desenvolvido no Laboratório HERCULES em parceria com o LNEC [2,3] compreende a preparação de nanomateriais consolidantes inovadores, à base de cal, compatíveis com as superfícies originais e eficazes a longo prazo, tendo sempre em consideração a minimização dos fatores de risco ambiental e humano. Nesta comunicação serão apresentadas e discutidas diferentes estratégias para a obtenção de nanopartículas de hidróxidos de metais alcalino-terrosos, nomeadamente, as condições experimentais de síntese. Adicionalmente serão apresentados e discutidos os resultados de estudos de eficiência das dispersões de nanocais preparadas quando aplicadas em provetes de argamassas de cal. [1] Piero Baglioni, Emiliano Carretti and David Chelazzi (2015) Nanomaterials in art conservation. Nature Nanotechnology, 10 APR, 287-29 [2] P.I. Girginova, C. Galacho, J. Mirão, R. Veiga, A.S. Silva, A. Candeias (2016) Estudos preliminares para consolidação de suportes com pintura mural: síntese e caracterização de nanocais. Conservar património, 23, 103-107. [3] G. Borsoi, B. Lubellia, R. van Hees, R. Veiga, A.S. Silva (2016) Understanding the transport of nanolime consolidants within Maastricht limestone. Journal of Cultural Heritage, 18, 242-249.SFRH/BPD/97692/2013 (FCT

Di-μ-glutarato-κ4 O 1:O 5-bis­[aqua­(1,10-phenanthroline-κ2 N,N′)copper(II)]

In the centrosymmetric dinuclear title complex, [Cu2(C5H6O4)2(C12H18N2)2(H2O)2], the CuII atom displays a dis­torted square-pyramidal coordination environment with the basal plane occupied by two phenanthroline N atoms and two O atoms from different glutarate dianions while a water mol­ecule is located at the apical position. Of the two water H atoms, one is engaged in an intra­molecular hydrogen bond with a free oxygen of the dianion whereas the second is engaged in an inter­molecular hydrogen bond, building a corrugated layer parallel to (100). These layers are further connected through π–π stacking inter­actions involving symmetry-related phenanthroline rings [centroid–centroid distance = 3.5599 (17) and 3.5617 (18) Å], building a three dimensionnal network. C—H⋯π inter­actions involving the phenanthroline ring system are also observed

Estudos preliminares para consolidação de suportes com pintura mural: síntese e caracterização de nanocais

-Resumo Neste trabalho apresentam-se os resultados da síntese e da caracterização de nano-materiais de hidróxido de cálcio e de hidróxido de magnésio visando a sua aplicação como consolidantes de suportes com pintura mural. Este estudo preliminar constitui a etapa inicial de um projeto em curso e que tem como principal objetivo o desenvolvimento de novas estratégias de síntese de nano-materiais inovadores para conservação e restauro de revestimentos antigos. - Abstract In this publication, we report the synthesis and characterization of calcium and magnesium hydroxides nanoparticles for consolidation of mural paintings. Some preliminary results are discussed. This research is the initial part of our ongoing project which aims to develop new synthetic strategies towards novel and innovative materials for preservation and restoration of old rend

CARGC Briefs Volume I: ISIS Media

The essays that comprise CARGC Briefs Volume I: ISIS Media began their lives as presentations at a small, by-invitation workshop, “Emerging Work on Communicative Dimensions of Islamic State,” held on May 3-4, 2017 at the Center for Advanced Research in Global Communication at the Annenberg School for Communication. Consistent with CARGC’s mission to mentor early-career scholars, the workshop was a non-public event featuring graduate students, some affiliated with the Jihadi Networks of Communication and CultureS (JINCS) research group at CARGC, and others from around the United States and the world, in addition to postdocs and faculty members. Parameters were purposefully broad to encourage independent thought and intellectual exploration: contributors were asked to write short essays focusing on any single aspect of Islamic State that was part of their research. The result is a group of fascinating essays: using mostly primary sources (textual, visual, or audio-visual), examining several media platforms and modalities, considering multiple levels of theoretical deployment and construction, and shedding light on various aspects of Islamic State communication against the broad back drop of history, ideology and geopolitics, the following include some of the most innovative approaches to Islamic State to date, and promise a wave of fresh voices on one of the most important challenges to global order.https://repository.upenn.edu/cargc_briefs/1000/thumbnail.jp