Keynote: A Unifed NMR View of Silicates from Zeolites to Ionic Liquids

Silicates represent a considerable technological and scientific issue from geology to nanomaterials. Among them zeolites are an essential societal issue, impacting about 20% or the mondial economy, directly or indirectly. Formation of nanoporous or dense silicates phases undergoes different chemical or physical states, and are of utmost importance. NMR is a spectroscopic method allowing to assess at a very local scale, chemical or physical state of matter, structure of liquids or of crystalline or amorphous solids and allows to investigate crystalization processes in an unique way. Nucleation, growth of crystals are challenging issues to understand most of geochemical, chemical or crystallogenesis formation of solids from the speciation of molecular state in liquids. NMR can access to structural, topological aspects of crystals, without the constraints of periodic boudaries conditions, liquids an solids state stuctural organization. This represents a unique way to access analytical, speciation or molecular formation of crystals. NMR represents a unique way to link the differents stages of organization from oligomerization to crystal formation. Insitu, ex-situ NMR characterization bring structural and dynamical organization of density flucutuations. As an archetype of silicate chemistry, zeolites formation will be reformulated. Elementary condensation steps will be identified and distinguished carefully, avoiding technical jargon, and favouring phsyco-chemical general concepts. As NMR can access solid state, crystalline or amorphous order, from oligomerization to nanoaggregation and crystalline order, an unified view of the successive condensation elementary steps of silicates formation will be presented. Such a enumeration of the progressive organization of condensed matter from silicic acid to the most complex zeolites may give rise to enumerate many different processes with a common knowledge and language between vastly different scientific and technological disciplines.status: publishe

Multidiagnostic Analysis to Track Zeolite Formation

Introduction The formation of zeolites in presence of tetraalkylammonium cations from so-called clear solutions using silicon alkoxides is a highly complex process. Our research aims to identify the key mechanisms on a molecular scale with the goal of understanding the factors that drive the formation of zeolites [1]. For this purpose we have used electrospray ionization mass spectrometry (ESI-MS), 29Si and 27Al liquid-NMR spectrometry, DOSY NMR (diffusion experiments) and small angle X-ray scattering (SAXS). Results and Discussion Here, we report the molecular mechanisms involved in the formation of microporous zeolite beta from liquid phase (Fig.1). The connectivity of both, oligomers and nanoparticles (NPs), has been quantitatively analysed, as well as the incorporation of Al in NPs and the specific interaction of silica-template within NPs. These data are compared with previous results on zeolites ZSM-5 (MFI), ZSM-11 (MEL) and SSZ-13 (CHA) from which general processes are concluded independently of the zeolite and/or template investigated [2]. Figure1. Zeolite beta crystallization from clear solution monitored by 29Si NMR. [1] Castro et al (2013) Micropor. Mesopor. Mat. (in press). [2] Eilesrten et al (2012) Chem. Mater. 24, 571-578status: publishe

Reported Cases and Diagnostics of Occupational Insect Allergy: A Systematic Review

A significant part of adult-onset asthma is caused by occupational exposure to both high- and low-molecular-mass agents. Insects are occasionally described to cause occupational allergy in professions including anglers and fishers, laboratory workers, employees of aquaculture companies, farmers, bakers, sericulture workers and pet shop workers. Occupational insect allergies are often respiratory, causing asthma or rhinoconjunctivitis, but can be cutaneous as well. The European Union recently approved three insect species for human consumption, enabling an industry to develop where more employees could be exposed to insect products. This review overviews knowledge on occupational insect allergy risks and the tools used to diagnose employees. Despite the limited availability of commercial occupational insect allergy diagnostics, 60.9% of 164 included reports used skin prick tests and 63.4% of reports used specific IgE tests. In 21.9% of reports, a more elaborate diagnosis of occupational asthma was made by specific inhalation challenges or peak expiratory flow measurements at the workplace. In some work environments, 57% of employees were sensitized, and no less than 60% of employees reported work-related symptoms. Further development and optimization of specific diagnostics, together with strong primary prevention, may be vital to the health conditions of workers in the developing insect industry

Self-organization of silicates on different length scales exemplified by amorphous mesoporous silica and mesoporous zeolite beta using multiammonium surfactants

In this study the structure directing effect of a gemini-type piperidine-based multi-ammonium surfactant during hydrothermal zeolite synthesis was investigated for two cases: with and without a source of aluminum. The absence of an aluminum source led to the formation of an amorphous mesoporous MCM-48 type silica material, while the presence of aluminum guaranteed the formation of zeolite beta with a hierarchical pore system. The two opposing cases were studied in a time and temperature-dependent manner. The mobility and through space interaction of these large surfactant molecules were studied by liquid state nuclear magnetic resonance (NMR) at a temperature relevant to hydrothermal synthesis (363 K) in pure water and upon addition of an aluminum and silicon source. In the gel state, at different stages of aging and hydrothermal synthesis, low angle X-ray diffraction (XRD) and solid state magic angle spinning nuclear magnetic resonance (1H MAS NMR) spectrometry determined the developing order within the system. At each of these different synthesis steps the respective intermediate materials were calcined. Transmission electron microscopy then allowed closer inspection of the locally developing mesoscopic order, while N2 physisorption was used to follow the evolution of porosity.status: publishe

Key Molecular Mechanisms for Zeolite Formation

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Key Molecular Mechanisms for Zeolite Formation - Moving Towards Rational Zeolite Design

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