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Light plays a pivotal role in many solid-state materials technologies. High-resolution solid-state nuclear magnetic resonance (NMR) is a key tool for characterizing atomic-scale structures and dynamics in solid compounds, but requisite magic angle spinning (MAS) of the sample-containing rotors limits the measurement of these systems in their irradiated states. Here we report on a bespoke methodology for performing solid-state NMR of a sample irradiated with visible/ultraviolet (vis/UV) light, while undergoing MAS at frequencies ≤15 kHz. A fiber optic insert guides vis/UV light to the spinning NMR rotor, where a glass end cap and dispersion rod act to illuminate the sample inside the rotor. This methodology was used to follow the photopolymerization reaction of n-butyl acrylate, providing well-resolved 1H and 13C NMR assignments of the formation of a semi-solid polymer gel. [ABSTRACT FROM AUTHOR]

The removal of heavy metal ions from wastewater often necessitates the use of ion exchange resins. Current methods for assessing ion exchange efficiency are indirect and destructive. Some heavy metal ions, such as Cu2+ and Ni2+, are paramagnetic and influence the NMR relaxation times of water protons. NMR relaxometry can therefore be utilized to track the removal of these ions by ion exchange resins. In this study, we use relaxometry to monitor in situ the loading with Ni2+ and Cu2+ of Amberlite IR120 and Dowex Marathon MSC resins, with the resin column inserted into a low‐field NMR device. The multiexponential transverse relaxation curves were fitted using a biexponential model. Before and during the loading of the resin, the water with the slowest relaxation corresponds to treated water (free of Ni2+ or Cu2+) flowing between the resin beads. After saturation, the slowest fraction corresponds to the untreated solution (containing Ni2+ or Cu2+) flowing between the resin beads saturated with paramagnetic ions. The evolution with time of the transverse relaxation rate and the amplitude of the slowly relaxing water fraction shows a clear transition, occurring later at the bottom of the resin bed compared with the middle and top. This is interpreted as an indication of the saturation of the studied zone with paramagnetic ions, confirmed by the quantification of Ni2+ or Cu2+ in the effluent using AES spectroscopy. This proof‐of‐concept study demonstrates that NMR relaxometry can be used in situ to monitor the loading of a resin bed with paramagnetic ions. [ABSTRACT FROM AUTHOR]

While 1H-1H J-couplings are the cornerstone of all spectral assignment methods in solution-state NMR, they are yet to be observed in solids. Here we observe 1H-1H J-couplings in plastic crystals of (1S)-(−)-camphor in solid-state NMR at magic angle spinning (MAS) rates of 100 kHz and above. This is enabled in this special case because the intrinsic coherence lifetimes at fast MAS rates become longer than the inverse of the 1H-1H J couplings. For example, at 160 kHz MAS the coherence lifetimes are longer than 20 ms, corresponding to refocused linewidths of less than 15 Hz. As a result, we are able to record two-dimensional 1H-1H J resolved spectra that allow the observation and measurement of 1H-1H J-couplings in solid camphor. The J-couplings also lead to unambiguous through-bond correlations in 1H-1H refocused incredible natural abundance double quantum transfer (INADEQUATE) and uniform-sign cross-peak double-quantum-filtered correlation spectroscopy (UC2QFCOSY) experiments. The authors demonstrate the detection of 1H 1H J-couplings, which are difficult to observe in the solid state, in plastic crystals of camphor using solid state NMR at magic angle spinning rates of 100 kHz and above. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are semiconductor nanocrystals that are used in optoelectronic applications. Most modern QDs are based on toxic metals, for example Cd, and do not comply with the European Restriction of Hazardous Substances regulation of the European Union. Latest promising developments focus on safer QD alternatives based on elements from the III–V group. However, the InP‐based QDs lack an overall photostability under environmental influences. One design path of achieving stability is through encapsulation in cross‐linked polymer matrices with the possibility to covalently link the matrix to surface ligands of modified core–shell QDs. The work focuses on the formation of polymer microbeads suitable for InP‐based QD encapsulation, allowing for an individual protection of QDs and an improved processibility via this particle‐based approach. For this, a microfluidic based method in the co‐flow regime is used that consists of an oil‐in‐water droplet system in a glass capillary environment. The generated monomer droplets are polymerized in‐flow into poly(LMA‐co‐EGDMA) microparticles with embedded InP/ZnSe/ZnS QDs using a UV initiation. They demonstrate how a successful polymer microparticle formation via droplet microfluidics produces optimized matrix structures leading to a distinct photostability improvement of InP‐based QDs compared to nonprotected QDs. [ABSTRACT FROM AUTHOR]

A cooperative OSDA strategy is demonstrated, leading to novel high‐silica FAU zeolites with a large potential for disruptive acid catalysis. In bottom‐up synthesis, the symbiosis of choline ion (Ch+) and 15‐crown‐5 (CE) was evidenced, in a form of full occupation of the sodalite (sod) cages with the trans Ch+ conformer, induced by the CE presence. CE itself occupied the supercages along with additional gauche Ch+, but in synthesis without CE, no trans was found. The cooperation, and thus the fraction of trans Ch+, was closely related to the Si/Al ratio, a key measure for FAU stability and acidity. As such, a bottom‐up handle for lowering the Al‐content of FAU and tuning its acid site distribution is shown. A mechanistic study demonstrated that forming sod cages with trans Ch+ is key to the nucleation of high‐silica FAU zeolites. The materials showed superior performances to commercial FAU zeolites and those synthesized without cooperation, in the catalytic degradation of polyethylene. [ABSTRACT FROM AUTHOR]

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In soft condensed matter, Small Angle Neutron Scattering (SANS) is a central tool to probe structures with characteristic sizes ranging from 1 to 100 nm. However, when used as a standalone technique, the dynamic properties of the sample are not accessible. Nuclear Magnetic Resonance (NMR) is a versatile technique which can easily probe dynamical information. Here, we report on the coupling of a low-field NMR system to a SANS instrument. We show that this original set-up makes it possible to obtain structural information and to simultaneously extract in situ on a same sample, long-range translational diffusion coefficient, T 1 and T 2 nuclear spin relaxation times. Such a feature is of major interest when a sample experiences a transient physical state or evolves rapidly. We illustrate the capabilities of alliancing these experimental methods by following the critical temperature-induced phase separation of a concentrated Poly(Methacrylic Acid) solution at its Lower Critical Solution Temperature. The characteristic size related to the domain growth of the polymer-rich phase of the gel is monitored by the evolution of the SANS spectra, while the dynamics of the sol phase (H2O and polymer) is simultaneously characterized by NMR by measuring T 1 , T 2 and the diffusion coefficient. Great care has been taken to design a cell able to optimize the thermalization of the sample and in particular its equilibration time. Details are given on the sample cell specifically designed and manufactured for these experiments. The acquisition time needed to reach good signal-to-noise ratios, for both NMR and SANS, match: it is of the order of one hour. Altogether, we show that in situ low-field NMR/SANS coupling the NMR is meaningful and is a promising experimental approach. [ABSTRACT FROM AUTHOR]

Background Enzymatic hydrolysis is a crucial step of biomass conversion into biofuels and different pretreatments have been proposed to improve the process efficiency. Amongst the various factors affecting hydrolysis yields of biomass samples, porosity and water accessibility stand out due to their intimate relation with enzymes accessibility to the cellulose and hemicellulose fractions of the biomass. In this work, sugarcane bagasse was subjected to acid and alkali pretreatments. The changes in the total surface area, hydrophilicity, porosity and water accessibility of cellulose were investigated by scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). Results Changes in chemical and physical properties of the samples, caused by the partial removal of hemicellulose and lignin, led to the increase in porosity of the cell walls and unwinding of the cellulose bundles, as observed by SEM. 1H NMR relaxation data revealed the existence of water molecules occupying the cores of wide and narrow vessels as well as the cell wall internal structure. Upon drying, the water molecules associated with the structure of the cell wall did not undergo significant dynamical and partial moisture changes, while those located in the cores of wide and narrow vessels kept continuously evaporating until reaching approximately20% of relative humidity. This indicates that water is first removed from the cores of lumens and, in the dry sample, the only remaining water molecules are those bound to the cell walls. The stronger interaction of water with pretreated bagasse is consistent with better enzymes accessibility to cellulose and higher efficiency of the enzymatic hydrolysis. Conclusions We were able to identify that sugarcane bagasse modification under acid and basic pretreatments change the water accessibility to different sites of the sample, associated with both bagasse structure (lumens and cell walls) and hydrophilicity (lignin removal). Furthermore, we show that the substrates with increased water accessibility correspond to those with higher hydrolysis yields and that there is a correlation between experimentally NMR-measured transverse relaxation times and the efficiency of enzymatic hydrolysis. This might allow for semiquantitative estimates of the enzymatic hydrolysis efficiency of biomass samples using inexpensive and non-destructive low-field 1H NMR relaxometry methods. [ABSTRACT FROM AUTHOR]

The demand for more ecological, highly engineered hydrogel beads is driven by a multitude of applications such as enzyme immobilization, tissue engineering and superabsorbent materials. Despite great interest in hydrogel fabrication and utilization, the interaction of hydrogels with water is not fully understood. In this work, NMR relaxometry experiments were performed to study bead–water interactions, by probing the changes in bead morphology and surface energy resulting from the incorporation of carboxymethyl cellulose (CMC) into a cellulose matrix. The results show that CMC improves the swelling capacity of the beads, from 1.99 to 17.49, for pure cellulose beads and beads prepared with 30% CMC, respectively. Changes in water mobility and interaction energy were evaluated by NMR relaxometry. Our findings indicate a 2-fold effect arising from the CMC incorporation: bead/water interactions were enhanced by the addition of CMC, with minor additions having a greater effect on the surface energy parameter. At the same time, bead swelling was recorded, leading to a reduction in surface-bound water, enhancing water mobility inside the hydrogels. These findings suggest that topochemical engineering by adjusting the carboxymethyl cellulose content allows the tuning of water mobility and porosity in hybrid beads and potentially opens up new areas of application for this biomaterial. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate frameworks (ZIFs) are a sub-class of metal-organic frameworks (MOFs). Although generally stable, ZIFs can undergo post-synthetic linker exchange (PSLE) in solution under mild conditions. Herein, we present a novel, solvent-free approach to post-synthetic linker exchange through exposure to linker vapor., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)