The disorder in c-alon is caused by random arrangement of nitrogen atoms and aluminum vacancies. To understand the properties and electronic structure of c-alon by theoretical methods, the most reasonable structure model is needed. We examined the site preference of nitrogen atoms and aluminum vacancies by first-principles density functional theory (DFT) calculations on Al 24 O 24 N 8 and Al 23 O 27 N 5 . The calculated results for Al 24 O 24 N 8 with the lowest total energy indicated that nitrogen atoms prefer to be far away from each other, rather than in a completely random arrangement. The further investigation on Al 23 O 27 N 5 shows that the aluminum vacancies tend to possess octahedral sites and coordinate only with oxygen atoms. Evaluated by lattice variances (D a and D h ) and simulated XRD pattern, the most reasonable structure model of Al 23 O 27 N 5 has little deviation from the experimental results. The calculated bulk modulus of 200.9 GPa in Al 23 O 27 N 5 is slightly lower than the experimental value. The electronic structure reveals that the bonds of Al-N and Al-O have partially covalent and ionic characterization, while the covalent bond strength of Al-N is stronger than that of Al-O. The calculated band gap is 3.99 eV, which is much closer to the experimental 4.56 eV than previous suggestions. W.-Y. Ching-contributing editor Manuscript No. 32185.

Few‐layer black phosphorus (FL‐BP) has been intensively studied due to its attractive properties and great potential in electronic and optoelectronic applications. However, the intrinsic instability of FL‐BP greatly limits its practical application. In this study, the amphiphobic FL‐BP is achieved by functionalization of 1H,1H,2H,2H‐perfluorooctyltrichlorosilane (PFDTS) on the surface of FL‐BP. The obtained PFDTS coated FL‐BP (FL‐BP/PFDTS) demonstrates enhanced stability, which is not observed during significant degradation for 2 months in high moisture content environment (95% humidity). Particularly, attributing to the surface amphiphobicity, FL‐BP/PFDTS exhibits strong surface water repellency in the presence of oleic acid (as the contaminant), while other passivation coating layers (such as hydrophilic or hydrophobic coating) become hydrophilicity under such conditions. Owing to this advantage, the obtained FL‐BP/PFDTS demonstrates enhanced stability in high moisture content environment for 2 months, even though the surface is contaminated by oil liquid or other organic solvents (such as oleic acid, CH2Cl2, and N‐methyl‐2‐pyrrolidone). The passivation of FL‐BP by amphiphobic coating provides an effective approach for FL‐BP stabilization toward future applications.

in 65-85% isolated yields. X-ray analyses show these complexes have decreasing steric hindrance in the coordination spheres of the metal centers in the order 1 > 2 > 3 > 4 > 5 > 6. A mechanism involving intramolecular alkyl and hydrogen migration is supported on the basis of DFT calculations to account for ligand alkylation. Activated by [Ph 3 C]-[B(C 6 F 5 ) 4 ], all of these iminoamido rare earth metal dialkyl complexes are active for living polymerization of isoprene, with activity and selectivity being significantly dependent on the steric hindrance around the metal center to yield homopolyisoprene materials with different microstructures and compositions. The sterically crowded complexes 1-3 give a mixture of 3,4-and trans-1,4-polyisoprenes (3,4-selectivities: 48-82%, trans-1,4-selectivities: 50-17%), whereas the less sterically demanding complexes 4-6 show high 3,4-selectivities (3,4-selectivities: 90-100%). In the presence of 2 equiv of Al i Bu 3 , the complexes 1-6/activator systems exhibit higher activities and 3,4-selectivities in the living polymerization of isoprene. A similar structure-reactivity relationship in polymerization catalysis can be also observed in these ternary systems. A possible mechanism of the isoprene polymerization processes is proposed on the basis of the DFT calculations.

Lateral flow assay (LFA) is one of the most prevalent commercially available techniques for point-of-care tests due to its simplicity, celerity, low cost and robust operation. However, conventional colorimetric LFAs have inferior limits of detection (LODs) compared to sophisticated laboratory-based assays. Here, we report a simple strategy of test-zone pre-enrichment to improve the LoD of LfA by loading samples before the conjugate pad assembly. The developed method enables visual LODs of miR-210 mimic and human chorionic gonadotropin protein, to be improved by 10-100 fold compared with a conventional LfA setup without introducing any additional instrument and reagent except for phosphate running buffer, while no obvious difference occurred for Aflatoxin B1 (AFB1). It takes about 6-8 min to enrich every 50 μL of sample diluted with phosphate running buffer, therefore we can get visual results within 20 min. We identified a parameter by modeling the entire process, the concentration of probe-analyte conjugate at test zone when signaling unit being loaded, to be important for the improvement of visual limit of detection. In addition, the test-zone pre-enrichment did not impair the selectivity when miR-210 mimic was adopted as target. Integrated with other optimization, amplification and modification of LfAs, the developed test-zone pre-enrichment method can be applied to further improve LoD of LfAs. Lateral flow assay (LFA), a paper-based in-situ detection platform, has been widely used in diverse fields such as biomedicine, environmental health, quality control and food safety due to its rapid, inexpensive, portable measurements 1. Basing on affinity interactions such as hybridization of oligonucleotide or aptamer-target, antibody-antigen or biotin-streptavidin, the signal of the test zone on the LFA test strip changes with the concentration of a particular analyte of interest when a liquid sample is applied 2,3. There are two basic formats of LFA: sandwich format and competitive format. In addition, the competitive format could be designed in the following two ways: fixing the capture probe of target at test zone (competitive format I) or fixing the competitive analogue at test zone (competitive format II). Generally, there are two strategies to load signaling unit in the conventional LFA. The first one is the direct sampling method with drying signaling unit on the conjugate pad fixed between the nitrocellulose (NC) membrane and the sample pad before sampling. This strategy is the most widely used and easily handled one and the results usually show significant concentration dependence. However, the limit of detection (LOD) is usually poor, which is the main drawback of this conventional LFA. The other strategy is the pre-mixing/pre-incubation sampling method with mixing signaling unit with sample solution to load together onto the sample pad 4. Signaling unit is greatly diluted by sample solution in this strategy, resulting in a prolonged interaction between signaling unit and capture molecules at test zone and ...