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Biodegradable poly(lactic acid) (PLA)-based composites were prepared using PLA and basalt scale (BS) via a solution-blending method. BS surfaces were treated using a silane coupling agent, and their surface properties were characterized by high-resolution scanning electron microscopy, energy-dispersive X-ray spectrometry, and X-ray photoelectron spectrometry. Moreover, the influence of BS content on the thermal properties, flexural properties, impact strength, and morphology of the PLA/silane-coupling-agent-treated BS (KH-BS) composites was analyzed. The thermal stability of the composites significantly increased due to the addition of KH-BS. Impact strength tests showed that the impact strength of the PLA/KH-BS composite with 4 wt% KH-BS was 3.14kJ/m2, which is 51% higher than that of pristine PLA (2.07 kJ/m2). The analysis of the fracture surfaces of the composites after the impact strength tests revealed a rough morphology with numerous river-like micro-cracks. The study results demonstrate that the addition of KH-BS significantly improves the thermal stability and impact strength of PLA/KH-BS composites. [ABSTRACT FROM AUTHOR]

Long persistent phosphors (LPPs) have drawn tremendous research interest owing to their mysterious optical phenomena and widespread applications. LPPs in the ultraviolet‐C (UVC, 200–280 nm) spectral range particularly hold promise in terms of sterilization, drug release, and cancer therapy. However, all reported UVC LPPs have so far relied on the use of Pr3+ as the emitter, resulting in a limited scope of such phosphors. Here, a new concept for designing UVC LPPs is proposed, leading to the birth of the first non‐rare‐earth phosphor (YPO4:Bi3+) with a UVC afterglow duration of more than 2 h. Experimental characterizations including thermoluminescence spectra and high‐resolution synchrotron X‐ray diffraction, coupled with first‐principles calculations, reveal that various intrinsic defects in YPO4, such as Y vacancies and Y–O vacancy complexes, serve as hole traps to capture and store a large number of holes created by X‐ray irradiation, while Bi3+ ions can trap thermalized electrons. This work highlights the key role of Bi3+ ions in mediating energy storage and release in persistent phosphors by acting as both electron traps and emitters, and thus offers new opportunities for rationally designing non‐RE‐activated UVC LPPs. [ABSTRACT FROM AUTHOR]

Long persistent phosphors (LPPs) have attracted enduring attention owing to their wide applications. However, the discovery of LPPs is thus far largely the results of trial and error. Here, theory‐guided defect tuning through topochemical reactions is demonstrated for accelerated discovery of emerging LPPs. First‐principles calculations are employed to identify the thermodynamic charge‐transition levels of different defect states, which help examine whether the candidate structure is a suitable host for afterglow. Rationally tuning the species and concentrations of defects through topochemical reactions is then illustrated, which leads to discovery of Pr3+‐doped LaPO4 featuring ultraviolet C afterglow with a lasting time of over 2 h. Such a strategy, in conjunction with advanced characterizations including high‐resolution synchrotron X‐ray diffraction, positron annihilation lifetime spectroscopy, and electron spin resonance, suggests a radical‐involved afterglow mechanism. Importantly, it is illustrated that this concept can be extended for the discovery of more LPPs. It is suggested that theory‐guided defect engineering enabled by topochemical reactions can be used as a powerful tool to accelerate discovery of novel LPPs with much clearer afterglow mechanisms, with implications even for the design of other optoelectronic materials. [ABSTRACT FROM AUTHOR]

We revisit the idea that the Galactic Center (GC) is the dominant source of galactic cosmic rays (GCRs), based on a series of new observational evidence. A unified model is proposed to explain the new phenomena of GCRs and ?-rays simultaneously. The GCRs are thought to be accelerated during past activities of the GC. The pair production process of GCRs in the strong radiation field due to the GC activity is responsible for the knee structure of the CR spectra. A fraction of e+e- produced by pair production interactions can be reaccelerated in the induced bipolar jets and be transported into the halo, leaving the Fermi ?-ray bubbles and WMAP microwave haze as the remnant signal. Finally, the CRs diffuse in the bulge could further interact with the interstellar medium to produce low energy e+e-. After cooling down, these positrons may annihilate to produce the 511 keV line emission as discovered by INTEGRAL. [ABSTRACT FROM AUTHOR]

Ethylene polymerization catalyzed by Ni(II) complexes that bear new bidentate ligands with a functional hybrid of amine and imine has been studied. A class of new α-aminoaldimines and their nickel complexes [R1R2NCMe2CH=N(2,6-R32C6H3)]NiBr2 (R1 = R2 = Me, R3 = Me (Ni-1b); R3 = iPr (Ni-1c); 1 = R2 = Et, R3 = H (Ni-2a); Me (Ni-2b); iPr (Ni-2c); R1 = R2 = nPr, R3 = iPr (Ni-3c); (R1R2) = c-C3H6 R3 = tPr (Ni-4c); (R1R2) = c-C4H8, R3 = iPr (Ni-5c)) were synthesized. The molecular structures of six nickel complexes were determined by X-ray crystallography, showing distorted tetrahedral configurations. The SQUID data of Ni-1c confirms its ground state of triplet spin. Using methylaluminoxanes (MAO) as the activator, the nickel complexes are found to catalyze ethylene polymerization under moderate pressure and ambient temperature. The activity reaches to 106 g PE mol Ni-1 h-1, and increases with the ethylene pressure in the range of 14-28 bar. The highly branching PE products have Mn ∼ 105 with PDI < 2. The amine and imine functionalities demonstrate independent control to the polymerization reactions, wherein the activity appears to be facilitated by using the catalysts installed with bulky imino substituents as well as with less sterically hindered amino substituents. This is ascribed to the C2 unsymmetric coordination in the square planar resting state in which the bulky polymer chain prefers cis to the imine and the small ethylene monomer is cis to the amine. [ABSTRACT FROM AUTHOR]

New α-aminoaldimines with the formula of Et2NCMe2CHNR (R = iPr, tBu, Ph) and their dichloro or diacetato complexes of Ni, Pd, Pt are prepared and structurally characterized. A nickel complex is in a distorted tetrahedral configuration, and the Pd and Pt complexes (4–6) are of square planar form. The α-aminoaldimines can chelate to the metal in a C2-unsymmetric bidentate motif through the hetero functionalities of amine and imine, which show comparable transinfluence. Square planar organometallic palladium derivatives bearing α-aminoaldimines, including Pd–methyl, Pd–acetyl, and Pd–(η2-acetylnorboryl) (7–10), are also synthesized. The latter two species are a result of CO-insertion into Pd–methyl complexes and ensuing norbornene-insertion, respectively. The geometrical isomerism is found in the transconfiguration in most studied cases. Such a stereoselectivity results from the thermodynamic stability governed predominantly by steric control. The stereoselectivity is also supported by DFT calculations. [ABSTRACT FROM AUTHOR]