Controlling the shape of metal–organic framework (MOF) crystals is important for understanding their crystallization and useful for myriad applications. However, despite the many advances in shaping ...of inorganic nanoparticles, post‐synthetic shape control of MOFs and, in general, molecular crystals remains embryonic. Herein, we report using a simple wet‐chemistry process at room temperature to control the anisotropic etching of colloidal ZIF‐8 and ZIF‐67 crystals. Our work enables uniform reshaping of these porous materials into unprecedented morphologies, including cubic and tetrahedral crystals, and even hollow boxes, by an acid–base reaction and subsequent sequestration of leached metal ions. Etching tests on these ZIFs reveal that etching occurs preferentially in the crystallographic directions richer in metal–ligand bonds; that, along these directions, the etching rate tends to be faster on the crystal surfaces of higher dimensionality; and that the etching can be modulated by adjusting the pH of the etchant solution.
Post‐synthetic wet‐chemical anisotropic etching of colloidal ZIF‐8 and ZIF‐67 crystals enables uniform reshaping of them into unprecedented shapes, including cubic and tetrahedral crystals, and even hollow boxes, by an acid–base reaction and subsequent sequestration of leached metal ions.
Single-Crystal Metal−Organic Framework Arrays Carbonell, Carlos; Imaz, Inhar; Maspoch, Daniel
Journal of the American Chemical Society,
02/2011, Letnik:
133, Številka:
7
Journal Article
Recenzirano
A novel, versatile pen-type lithography-based methodology was developed to control the growth of HKUST-1 crystals on surfaces by direct delivery of femtoliter droplets containing both inorganic and ...organic building block precursors. This approach shows that through the use of surfaces with low wettability it is possible to control the crystallization of a single submicrometer metal−organic framework crystal at a desired location on a surface.
Polymer brush patterns have a central role in established and emerging research disciplines, from microarrays and smart surfaces to tissue engineering. The properties of these patterned surfaces are ...dependent on monomer composition, polymer height, and brush distribution across the surface. No current lithographic method, however, is capable of adjusting each of these variables independently and with micrometer-scale resolution. Here we report a technique termed Polymer Brush Hypersurface Photolithography, which produces polymeric pixels by combining a digital micromirror device (DMD), an air-free reaction chamber, and microfluidics to independently control monomer composition and polymer height of each pixel. The printer capabilities are demonstrated by preparing patterns from combinatorial polymer and block copolymer brushes. Images from polymeric pixels are created using the light reflected from a DMD to photochemically initiate atom-transfer radical polymerization from initiators immobilized on Si/SiO
wafers. Patterning is combined with high-throughput analysis of grafted-from polymerization kinetics, accelerating reaction discovery, and optimization of polymer coatings.
It is demonstrated that metal–organic frameworks (MOFs) can be replicated in a biomimetic fashion from protein patterns. Bendable, fluorescent MOF patterns are formed with micrometer resolution under ...ambient conditions. Furthermore, this technique is used to grow MOF patterns from fingerprint residue in 30 s with high fidelity. This technique is not only relevant for crime‐scene investigation, but also for biomedical applications.
The ever-increasing occurrence and persistence of pharmaceutically active compounds (PhACs) in soils, sediments, drinking water supplies and wastewater effluents are a matter of serious environmental ...concern for governments and researchers worldwide. Nanofiltration as tertiary treatment method can be a viable and practical tool to remove these pollutants from aquatic environments. However, organic matter present in water sources can foul the membrane surface during operation, thus being potentially able to affect the membrane performance. Therefore, fouling mechanisms could heavily influence on the removal efficiencies. The purpose of this study was to investigate the implementation of three nanofiltration membranes (TFC-SR2, NF-270 and MPS-34) and to study both the rejection of trace PhACs and the fouling mechanisms for each membrane as a function of feed solution pH. Fouling mechanisms were predicted by Hermia's model adapted to cross-flow configurations. Results demonstrated that higher removals were obtained at slightly alkaline pH, especially for anionic trace PhACs. At the same conditions, more severe fouling was observed, which resulted in strong flux declines and an increase in hydrophobicity. This indicates that the attached organic matter on the membrane surface acts as a secondary selective barrier for separation.
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•Rejection of eight PhACs and triclosan by three nanofiltration membranes was studied.•Fouling mechanisms were assessed by using Hermia's models.•Effect of both feed solution pH and fouling on the removal of PhACs was analysed.•Gel layer formation demonstrated to be the predominant fouling mechanism.•Rejection of anionic PhACs was strongly pH-dependent.
La aprobación de la Ley Orgánica de regulación de la eutanasia supone un paso importantísimo en el Derecho español hacia el reconocimiento de la capacidad de autodeterminación de la persona, emanada ...de su Dignidad. La LORE no es (solo) una norma despenalizadora —si lo fuera, sería insuficiente—, sino reguladora de una prestación que implica al Estado social y democrático de Derecho en la facilitación a los ciudadanos de la satisfacción de una necesidad deseada y solicitada. Se analiza el detallado procedimiento previsto en la ley y se sugiere la necesidad de evitar ciertas interpretaciones y consecuencias no deseables. Pese a la afirmación anterior, la ley contempla una Disposición final que modifica el Código Penal y que es analizada muy críticamente. Con todo, no quedan satisfechas las consecuencias que deberían inferirse de la vinculación entre la dignidad, el libre desarrollo de la personalidad y la capacidad de autodeterminación personal.
•Rejection of ten PhACs by ceramic fine ultrafiltration membranes was studied.•Effect of feed solution pH on the removal of PhACs was analysed.•Results demonstrated that rejection of anionic PhACs ...was strongly pH-dependent.•The formed foulant layer on the membrane acted as a secondary membrane.
This study investigates the influence of feed solution pH and fouling on the rejection of ten selected pharmaceutically active compounds (PhACs) with different physicochemical characteristics (molecular weight, water solubility, log KOW, pKa, dipole moment, etc.) by three multichannel ceramic ultrafiltration membranes, ranging from 1 to 8kDa, in order to improve their removal from water. For this purpose, the comparison between filtration of PhACs in deionised water (Feed I) and in real wastewater effluent (Feed II) was performed, demonstrating that the variation of pH and the formation of a foulant layer altered the separation mechanism and hence the rejection values of each PhAC varied. Higher rejections of most of the PhACs were higher at slightly alkaline pH, especially for anionic compounds in the filtration with real wastewater. In these conditions, flux decline was more severe. The formed fouling layer onto the hydrophilic membrane surface acted as a secondary barrier for separation with different properties like hydrophobicity and charge. Electrostatic interactions were the main separation mechanism in the filtration of PhACs in deionised water, while the hydrophobic/hydrophilic interactions played a crucial role in the filtration experiments with real wastewater effluent. Thus, the reported results indicated that the rejection of pharmaceutically active compounds was strongly pH-dependent, except for hydrophilic neutral compounds (acetaminophen and caffeine), which showed a pH-independent behaviour with low rejection values.
Here, we show that the surface-initiated thiol-(meth)acrylate polymerization can be used to create brush polymer patterns with precise control over the feature height at each microscale pixel. The ...reaction was studied using a printer where a digital micromirror device controls light delivery to the surface, so multiple reaction conditions can be examined in each print. The resulting increases in experimental throughput and precision were demonstrated by studying systematically the effect of photocatalyst, photoinitiator, and light intensity on feature growth rate. In addition to demonstrating the utility of surface-initiated thiol-(meth)acrylate chemistry for creating complex brush polymer patterns, this work describes an improved and high-throughput approach for studying grafted-from photopolymerizations.
AbstractEngineers use spatial information. Mapping and wayfinding in the real world are activities that use spatial orientation skills. A set of resources available on the Internet whereby engineers ...work with maps and spatial georeferenced information is termed geographic information science (GISc), which allows the use of mapping and exploratory navigation with maps and a continuous three-dimensional (3D) digital image of the real world to simulate navigation at a ground-level perspective. In this case study, a workshop composed of 193 civil engineering students, 35 belonging to a control group, was conducted to determine whether spatial orientation skills can be developed through map reading and the virtual wayfinding experience. After the workshop, the results showed a significant improvement in the spatial orientation skill, ranging between a minimum of 14.56° and a maximum of 26.61° rank in the Perspective Taking/Spatial Orientation Test: training had a positive impact on the development of spatial orientation skills. The control group results confirmed that students who were not subject to specific training did not increase their spatial orientation skill.
A methodology that can be efficiently used to synthesize, isolate, and study out‐of‐equilibrium crystal structures employing controlled and diffusion‐limited microfluidic environments is ...demonstrated. Unlike studies conducted with conventional mixing procedures in a flask, it is proven experimentally and with numerical simulations that microfluidic technologies can undoubtedly fine‐tune reaction times and reagents concentration profiles; factors that enable out‐of‐equilibrium crystal forms to be obtained.
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