Contributos para a atuação do SEPNA no âmbito da educação ambiental: proposta de um plano de ação

O trabalho apresentado descreve um projeto de investigação de um de mestrado em Educação Ambiental. Este trabalho tem como objetivo fornecer ao SEPNA um conjunto de recursos de Educação Ambiental que contribuam para melhoria da atuação desta especialidade da GNR junto da comunidade das aldeias rurais do concelho de Bragança, no que diz respeito à sensibilização e educação ambiental de forma a promover a mudança de comportamentos a favor do ambiente. O trabalho divide-se em três fases principais: 1ª - Pretende-se fazer um levantamento de informações relacionadas com as áreas de atuação do SEPNA. O número de coimas nos útimos 4 anos, dentro de cada área de intervenção, assim com as metodologias e recursos usados pelo SEPNA para a sensibilização ambiental da população, são um exemplo. 2ª - Utilizando as informações obtidas na fase anterior, será planificado um conjunto de atividades a usar pelo SEPNA para intervir na população. 3ª – Pretende-se aplicar no terreno, conjuntamente com elementos do SEPNA, o plano de atividades desenvolvido. Espera-se que, através da intervenção do plano elaborado, ocorra uma melhoria dos comportamentos pró-ambientais da população e que se este plano passe a ser uma ferramenta a usar pelo SEPNA na sua atuação na população.info:eu-repo/semantics/publishedVersio

Elucidating the Germanium Distribution in ITQ-13 Zeolites by Density Functional Theory

ITQ-13 is a medium-pore zeolite that can be prepared in all-silica form and as silicogermanate with Si/Ge ratios as low as 3. Usually synthesised in the presence of fluoride, ITQ-13 is among the very few systems containing fluoride anions in two distinct cage types, cube-like d4r units and [4 ⋅ 56 ] cages. Here, dispersion-corrected density functional theory (DFT) calculations are used to investigate the energetically most favourable Ge distributions for Si/Ge ratios between 55 and 6. The calculations show Ge atoms are incorporated at both the corners of d4r cages and at the basal plane of the [4 ⋅ 56 ] cages, in accordance with 19 F NMR spectroscopy. Two Ge atoms at adjacent corners of [4 ⋅ 56 ] cages are stable at the highest Ge content considered (Si/Ge=6). Such a local environment has not yet been considered in the experimental literature. A calculation of the corresponding 19 F NMR resonance points to overlap with other resonances, which might preclude its clear identification. Additional calculations investigate the variation of the dynamic behaviour of the fluoride anions as a function of the local environment as well as the selective defluorination of the [4 ⋅ 56 ] cages.publishe

RMN de materiais híbridos inorgânicos-orgânicos cristalino : métodos e aplicações

Doutoramento em QuímicaNa primeira das três partes em que esta tese está organizada apresentam-se algumas ideias e conceitos fundamentais em Ressonância Magnética Nuclear (RMN). Em particular, dá-se uma panorâmica dos métodos disponíveis para realizar o desacoplamento homonuclear 1H-1H por impulsos, baseados no desacoplamento dito Frequency-Switched Lee-Goldburg (FS-LG). Discute-se, também, como optimizar as condições experimentais que permitem registar espectros de alta resolução de RMN bidimensional (2D). A segunda parte desta tese apresenta casos de estudo de RMN dos seguintes materiais híbridos inorgânicos-orgânicos: complexos (i) binuclear e (ii) hexanuclear de germânio, ambos contendo ácidos fosfónicos como ligandos (respectivamente, pmida4- e hedp4-); (iii) um aluminofosfato microporoso, e (iv) um γ-titanofosfato lamelar tendo como hóspedes, respectivamente, metilamina e hexilamina. Estes sólidos são ricos em núcleos 1H e, por esta razão, as linhas espectrais de RMN de 1H sofrem alargamento homogéneo devido ao forte acoplamento dipolar homonuclear. Assim, não é de estranhar que os materiais híbridos tenham, até a data, sido objecto de poucos estudos de RMN de 1H. Nesta tese mostra-se que o desacoplamento FS-LG é uma técnica muito poderosa e robusta para estudar estes materiais, permitindo a aquisição, sob condições de alta resolução de 1H, de espectros 2D com correlação homo e heteronuclear 1H-X (X = 1H, 13C, 31P, 27Al). Ilustra-se, também, o uso de técnicas de reacoplamento dipolar, nomeadamente BABA, POSTC7 e RFDR. Usada em combinação com dados de difracção de raios-X, a informação RMN permite construir um modelo claro da estrutura dos materiais híbridos. Na terceira parte desta tese propõe-se uma nova técnica de RMN para estudo de núcleos quadrupolares, de spin 3/2 e 5/2, em sólidos. Concretamente, relata-se um método para a obtenção de espectros de núcleos quadrupolares de spin semi-inteiro, que permite o registo simultâneo dos chamados “multiple coherence transfer pathways (CTP)”, reduzindo consideravelmente o tempo de experiência. Usa-se uma ciclagem de fases do tipo “multiplex”, com registo separado de cada CTP na memória do computador, tendo em vista a selecção e o processamento de sinal após a aquisição. A aplicação, a estes conjuntos de dados, de uma mudança discreta da fase numérica permite gerar os CTPs alvo e combiná-los de forma a obter espectros 2D sem componentes dispersivas. Mostra-se, ainda, que é possível realizar experiências múltiplas com diferentes CTPs, durante o tempo de uma única experiência, por exemplo a aquisição de espectros 3QMAS/5QMAS, MQMAS/STMAS e MQMAS/DQFSTMAS. Finalmente, demonstra-se que acoplando o chamado soft-pulse added mixing (SPAM) e uma ciclagem de fases do tipo “multiplex duplo” permite adicionar construtivamente os CTPs, mesmo se estes tiverem sinal oposto. Encurta-se, desta forma, consideravelmente o tempo experimental, relativamente ao método multiplex simples.This thesis is organised in three parts, and the first one presents some basic NMR concepts and ideas. In particular, an overview of the 1H-1H homonuclear decoupling pulse methods, based on Frequency-Switched Lee-Goldburg (FSLG) decoupling, is given. The optimisation of the experimental conditions which afford high-resolution two-dimensional (2D) NMR spectra is also discussed. In its second part, this thesis presents a number of NMR case studies centred on the following inorganic-organic hybrid materials: (i) a germanium binuclear and (ii) a germanium hexanuclear complex, both containing phosphonic acid ligands (pmida4- and hedp4-, respectively); (iii) a microporous aluminophosphate, and (iv) a layered γ-titanium phosphate containing, respectively, methylamine and hexylamine guests. These solids are rich in 1H nuclei and, because of this, their 1H NMR spectral lines are usually broadened homogeneously by the strong homunuclear dipolar couplings. It is, thus, no wonder that hybrid materials have not been much studied by 1H NMR. Here, I show that FS-LG decoupling is a very powerful and robust technique to study these materials, allowing the acquisition, under 1H high-resolution, of 2D homoand hetero-nuclear correlation 1H-X (X = 1H, 13C, 31P, 27Al) NMR spectra. Dipolar recoupling techniques such as BABA, POSTC7 and RFDR were also employed. When used in tandem with X-ray diffraction data, the information forthcoming from these NMR studies provides a clear structural picture of the hybrid materials. In the third part of this thesis I introduce a new NMR method to study I = 3/2 and 5/2 quadrupole nuclei in powdered solids. More specifically, a new processing method to obtain 2D NMR spectra of half-integer quadrupole nuclei is described. This scheme allows the simultaneous acquisition of multiplecoherence transfer pathways (CTP), thus shortening considerably the experimental time. A “multiplex” phase cycling procedure is employed, which allows recording separately in the computer memory each CTP, for postacquisition signal selection and processing. By applying a numerical phase shift to these data sets it is possible to generate the targeted CTPs and combine them to obtain pure-absorption 2D spectra. I also demonstrate the feasibility of performing multiple experiments with distinct CTPs, during the timespan of a single experiment, for example the simultaneous acquisition of 3QMAS/5QMAS, MQMAS/STMAS and MQMAS/DQF-STMAS. Finally, I demonstrate that coupling the so-called “soft-pulse added mixing” (SPAM) and “double-multiplex” phase cycling allows the constructive addition of CTPs, even if they have opposite signs. The result is a considerable reduction in the experimental time as compared to the simple multiplex method

Unravelling the structure of chemisorbed CO2 species in mesoporous aminosilicas: a critical survey

Chemisorbent materials, based on porous aminosilicas, are among the most promising adsorbents for direct air capture applications, one of the key technologies to mitigate carbon emissions. Herein, a critical survey of all reported chemisorbed CO2 species, which may form in aminosilica surfaces, is performed by revisiting and providing new experimental proofs of assignment of the distinct CO2 species reported thus far in the literature, highlighting controversial assignments regarding the existence of chem- isorbed CO2 species still under debate. Models of carbamic acid, alkylammonium carbamate with different conformations and hydrogen bonding arrangements were ascertained using density functional theory (DFT) methods, mainly through the comparison of the experimental 13C and 15N NMR chemical shifts with those obtained computationally. CO2 models with variable number of amines and silanol groups were also evaluated to explain the effect of amine aggregation in CO2 speciation under confinement. In addition, other less commonly studied chemisorbed CO2 species (e.g., alkylammonium bicarbonate, ditethered carbamic acid and silylpropylcarbamate), largely due to the difficulty in obtaining spectroscopic identification for those, have also been investigated in great detail. The existence of either neutral or charged (alkylammonium siloxides) amine groups, prior to CO2 adsorption, is also addressed. This work extends the molecular-level understanding of chemisorbed CO2 species in amine-oxide hybrid surfaces showing the benefitof integrating spectroscopy and theoretical approaches.publishe

Exploring Molecular Dynamics of Adsorbed CO2 Species in Amine-Modified Porous Silica by Solid-State NMR Relaxation

Previous studies on CO2 adsorbents have mainly addressed the identification and quantification of adsorbed CO2 species in amine-modified porous materials. Investigation of molecular motion of CO2 species in confinement has not been explored in depth yet. This work entails a comprehensive study of molecular dynamics of the different CO2 species chemi- and physisorbed at amine-modified silica materials through the determination of the rotating frame spin-lattice relaxation times (T 1ρ) by solid-state NMR. Rotational correlation times (τC) were also estimated using spin relaxation models based on the Bloch, Wangsness, and Redfield and the Bloembergen-Purcell-Pound theories. As expected, the τC values for the two physisorbed CO2 species are considerably shorter (32 and 20 μs) than for the three identified chemisorbed CO2 species (162, 62, and 123 μs). The differences in molecular dynamics between the different chemisorbed species correlate well with the structures previously proposed. In the case of the physisorbed CO2 species, the τC values of the CO2 species displaying faster molecular dynamics falls in the range of viscous liquids, whereas the species presenting slower dynamics exhibit T 1ρ and τC values compatible with a CO2 layer of weakly interacting molecules with the silica surface. The values for chemical shift anisotropy (CSA) and 1H-13C heteronuclear dipolar couplings have also been estimated from T 1ρ measurements, for each adsorbed CO2 species. The CSA tensor parameters obtained from fitting the relaxation data agree with the experimentally measured CSA values, thus showing that the theories are well suited to study CO2 dynamics in silica surfaces.publishe

Harmful algae and toxis in paranaguá bay , Brazil: bases for monitoring

O complexo estuarino de Paranaguá (CEP; 25º30'S, 48º30'W), localizado no litoral sul do Brasil, abriga extensas áreas preservadas de manguezais e tem a pesca e aqüicultura como importantes atividades econômicas. Este trabalho investigou a ocorrência de microalgas nocivas no CEP e a presença de ficotoxinas no molusco bivalve Mytella guyanensis. Para tanto, foram coletadas amostras com periodicidade aproximadamente mensal, entre agosto de 2002 e outubro de 2003. Foram avaliadas variáveis físico-químicas, densidade de espécies nocivas e a presença de toxinas nos moluscos através de bioensaio com camundongos (DSP e PSP) e por cromatografia líquida (ASP). As espécies nocivas encontradas foram Pseudo-nitzschia spp., Dinophysis acuminata,Prorocentrum minimum,Gymnodinium catenatum,Phaeocystis spp., Chattonella spp. e Heterosigma akashiwo. Além dessas, Trichodesmium erythraeum e Coscinodiscus wailesii foram também incluídas no estudo pelo potencial de produzirem eventos nocivos na região. Toxinas diarréicas (DSP) foram detectadas em moluscos em dezembro de 2002 associadas à presença de D. acuminata (até 4.566 cel.l-1). Toxinas paralisantes e amnésicas foram produzidas por cepas cultivadas em laboratório. Primavera (de outubro a dezembro no hemisfério Sul) e final do verão (fevereiro a abril) foram os períodos de maior abundância de algas nocivas principalmente nos setores euhalino e polihalino interno do CEP.The estuarine complex of Paranaguá - ECP (South Brazil, 25º30'S, 48º30'W) is a large subtropical system, where pristine mangrove forests are still present, and fishery and aquaculture are important economic activities. This work investigated the occurrence of harmful algae in Paranaguá Bay, as well as the presence of toxins in the filter feeding mussel Mytella guyanensis, a local fishery resource. Samples along the Paranaguá sub-system were collected almost monthly from August 2002 to October 2003. Besides physical and chemical variables, cell densities of harmful species and presence of toxins in the mussel by mouse bioassay (DSP, PSP) and HPLC (ASP) were performed. HAB species included Pseudo-nitzschia spp., Dinophysis acuminata,Prorocentrum minimum,Gymnodinium catenatum,Phaeocystis spp., Chattonella spp. and Heterosigma akashiwo.Trichodesmium erythraeum and Coscinodiscus wailesii were also included in this study due to their potential for harmful bloom formation. Toxin results showed the occurrence of DSP (December 2002) in shellfish related to the presence of D. acuminata (max. 4,566 cells.l-1). Additionally, cultivated strains produced paralytic and amnesic toxins in laboratory. Spring (October to December, Southern Hemisphere) and late summer (February to April) were the periods of higher abundance of harmful algae, mainly in euhaline and inner polyhaline sectors of the ECP

What is being measured with p-bearing nmr probe molecules adsorbed on zeolites?

Elucidating the nature, strength, and siting of acid sites in zeolites is fundamental to fathom their reactivity and catalytic behavior. Despite decades of research, this endeavor remains a major challenge. Trimethylphosphine oxide (TMPO) has been proposed as a reliable probe molecule to study the acid properties of solid acid catalysts, allowing the identification of distinct Brønsted and Lewis acid sites and the assessment of Brønsted acid strengths. Recently, doubts have been raised regarding the assignment of the 31P NMR resonances of TMPO-loaded zeolites. Here, it is shown that a judicious control of TMPO loading combined with two-dimensional 1H-31P HETCOR solid-state NMR, DFT, and ab initio molecular dynamics (AIMD)-based computational modeling provides an unprecedented atomistic description of the host-guest and guest-guest interactions of TMPO molecules confined within HZSM-5 molecular-sized voids. 31P NMR resonances usually assigned to TMPO molecules interacting with Brønsted sites of different acid strength arise instead from both changes in the probe molecule confinement effects at ZSM-5 channel system and the formation of protonated TMPO dimers. Moreover, DFT/AIMD shows that the 1H and 31P NMR chemical shifts strongly depend on the siting of the framework aluminum atoms. This work overhauls the current interpretation of NMR spectra, raising important concerns about the widely accepted use of probe molecules for studying acid sites in zeolites.publishe

Moisture effect on the separation of CO2/CH4 mixtures with amine-functionalised porous silicas

The effect of minor amounts of water on the CO2 and CH4 adsorption on primary and secondary amine-functionalised mesoporous silicas (APTES@SBA-15 and DEAPTES@SBA15, respectively) was studied with a combination of high-pressure gas adsorption, solid state NMR of labelled 13CO2 and density functional theory (DFT) calculations. Known amounts of water were pre-adsorbed on the materials (0.047 to 0.157 mmol∙g−1) and the adsorption performance for CO2 and CH4 was compared to the performance of the dry samples. We observed that even when only minor amounts of water are present, the tertiary amine-functionalised material revealed a significant enhancement of the selectivity for CO2 (from ca. 5.8 to 208) while the one with primary amine maintained the same adsorption properties. This is related to the change in the adsorption mechanism in DEAPTES@SBA15 when water is present since water participates in the reaction of the tertiary amine with CO2 to produce bicarbonate (confirmed by NMR and DFT results). Such species was not observed in APTES@SBA-15 with water. From a broader perspective, the results presented in this work are relevant to confirm the suitability of this type of hybrid adsorbents in industrial applications related with CO2 adsorption, where minor amounts of water may be present in the process streams, such as during bio, landfill, or natural gas upgrading, or also in carbon capture applications.publishe