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BackgroundMolten salt systems have been extensively applied in the generation of nuclear and solar energy owing to their excellent heat transfer and storage performance. Therefore, it is essential to explore their physical and chemical properties, which are largely determined by their composition and ionic structure. In this regard, high-temperature (HT) nuclear magnetic resonance (NMR) has been demonstrated as an effective solution for qualitative analysis. Due to the existence of vent holes on the top of the commercialized standard NMR sample cell, it is not suitable for the study of some volatile, toxic or radioactive molten salt systems.PurposeThis study aims to implement ceramic NMR sample cells that are suitable for different molten salt systems.MethodsFirstly, a novel sealed sample cell that meets the requirements of molten salt systems was designed and produced by using an inner tube comprising AlN, BN, and Al2O3 ceramic materials, and an outer tube composed of ZrO2 ceramic materials. Then, with KBr as the standard sample, temperature calibration for this sample cell was conducted on the basis of 79Br NMR method. Finally, LiCl-KCl two-component molten salt (59.2 mol% LiCl-40.8 mol% KCl, eutectic melting point 353 ℃) was selected for HT-NMR experiment to verify the accuracy of temperature calibration, and check the performance of the HT-NMR method.ResultsExperimental results show that the sample cells are applicable in molten salt systems at a maximum temperature of 700 ℃, which meets the detection requirements of most molten salt systems. Additionally, the measurement results of the 79Br chemical shift of the KBr samples and captured HT 35Cl NMR spectra of the LiCl-KCl molten salt verify the reliability of the sample cell.ConclusionsBased on the results, the HT-NMR (High Temperature NMR) sample cells proposed in this study can be widely applied in various fields when the molten salt system requirements are met.

In this work, an "on‐off‐on" nanoprobe for specific detection of Cd2+ was constructed using N‐acetyl‐l‐cysteine (NAC)‐modified CdSe quantum dots (QDs). The prepared CdSe QDs exhibit characteristic green fluorescence. The adsorbed S2− on the surface of CdSe QDs leads to dangling bonds and causes the fluorescence quenching of QDs, where the fluorescence of the system turns "off". When Cd2+ exists, it can react with the adsorbed S2− to form CdS shell, resulting in the fluorescence enhancement of CdSe QDs, where the fluorescence of the system turns "on". Due to the similar lattice structure between CdSe and CdS, CdSe/CdS can be produced by shell deposition, while self‐nucleation of metal sulfide is observed in the presence of other metal ions. Thus, the developed nanoprobe shows high selectivity for Cd2+. Under the optimum sensing conditions, the fluorescence sensing signal of CdSe QDs depends linearly on the Cd2+ in the range of 0.2–9 μM. The limit of detection (LOD) and limit of quantification (LOQ) of this nanoprobe is 27 nM and 90 nM, respectively. Furthermore, the proposed nanoprobe can monitor Cd2+ in drinking water with a recovery rate between 95.82 % and 102.00 %, indicating its good practicability and applicability for real sample analysis. [ABSTRACT FROM AUTHOR]

In this work, an "on‐off‐on" nanoprobe for specific detection of Cd2+ was constructed using N‐acetyl‐l‐cysteine (NAC)‐modified CdSe quantum dots (QDs). The prepared CdSe QDs exhibit characteristic green fluorescence. The adsorbed S2− on the surface of CdSe QDs leads to dangling bonds and causes the fluorescence quenching of QDs, where the fluorescence of the system turns "off". When Cd2+ exists, it can react with the adsorbed S2− to form CdS shell, resulting in the fluorescence enhancement of CdSe QDs, where the fluorescence of the system turns "on". Due to the similar lattice structure between CdSe and CdS, CdSe/CdS can be produced by shell deposition, while self‐nucleation of metal sulfide is observed in the presence of other metal ions. Thus, the developed nanoprobe shows high selectivity for Cd2+. Under the optimum sensing conditions, the fluorescence sensing signal of CdSe QDs depends linearly on the Cd2+ in the range of 0.2–9 μM. The limit of detection (LOD) and limit of quantification (LOQ) of this nanoprobe is 27 nM and 90 nM, respectively. Furthermore, the proposed nanoprobe can monitor Cd2+ in drinking water with a recovery rate between 95.82 % and 102.00 %, indicating its good practicability and applicability for real sample analysis. [ABSTRACT FROM AUTHOR]

The 2LiF-BeF2 (FLiBe) salt melt is considered the primary choice for a coolant and fuel carrier for the generation IV molten salt reactor (MSR). However, the basics of ionic coordination and short-range ordered structures have been rarely reported due to the toxicity and volatility of beryllium fluorides, as well as the lack of suitable high-temperature in situ probe methods. In this work, the local structure of FLiBe melts was investigated in detail using the newly designed HT-NMR method. It was found that the local structure was comprised of a series of tetrahedral coordinated ionic clusters (e.g., BeF42−, Be2F73−, Be3F104−, and polymeric intermediate-range units). Li+ ions were coordinated by BeF42− ions and the polymeric Be–F network through the analysis of the NMR chemical shifts. Using solid-state NMR, the structure of solid FLiBe solidified mixed salts was confirmed to form a 3D network structure, significantly similar to those of silicates. The above results provide new insights into the local structure of FLiBe salts, which verifies the strong covalent interactions of Be–F coordination and the specific structural transformation to the polymeric ions above 25% BeF2 concentration. [ABSTRACT FROM AUTHOR]

Scion-rootstock union formation is a critical step toward the functional assemblage of heterogeneous plants. Interfamilial scion-rootstock interaction often results in graft incompatibility during the assemblage process, and the underlying mechanisms are largely unknown. In this study, we reported that tracheary element (TE) remodeling, including TE segmentation and deformation, rather than de novo formation from callus or adjacent tissues, took place at the early stage of grafting interface between Arabidopsis thaliana and Nicotiana benthamiana (At / Nb). Following cellular deposits, the short TEs from both partners were overlapping, dependent on the homogeneity of contacting TEs, with each other. Without overlapping, the TEs at the interface would grow laterally, and the TEs above and below the interface would undergo self-fusion to form insulating spiraling bundles. Finally, the overlapping TEs constituted a continuous network through alignment. Our results provide a definitive framework for the critical process of TE behavior in the At / Nb distant grafts, including (1) segmentation and/or deformation, (2) matching, overlapping, and cellular deposits, and (3) aligning or spiraling. These insights might guide us in the future into constructing more compatible distant grafts from the perspective of TE homogeneity. [ABSTRACT FROM AUTHOR]