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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]