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Terahertz (THz) light, probing electronic responses near the Fermi level, is closely linked to DC transport. In this study, we investigate the in situ THz and DC conductivity of epitaxial VO 2 films near the heating-induced insulator–metal transition. We find that the THz conductivity transition occurs at lower temperatures than the DC conductivity transition, with the separation increasing with film thickness and crystallization quality. Analysis of the complex conductivity spectra attributes this separation to released carrier confinement at THz frequencies. Our findings contribute to a deeper understanding of electron dynamics in VO 2 films. [ABSTRACT FROM AUTHOR]

Helianthus annuus seed byproduct is a residual product obtained after seed oil extraction. The present study investigated the preventive and repair effects of the H. annuus seed byproduct ethanol extract (HSE) on ultraviolet radiation (UVR)‐induced injury in human immortalized keratinocytes (HaCaTs) and human skin fibroblasts (HSFs). Results revealed that the total phenolic acid and oligosaccharide content in HSE was >50%. HSE had a stronger preventive effect on UVR‐induced injury than the repair effect. Moreover, phenolic acids were the main active component of HSE mediating the preventative effect. In HaCaTs and HSFs, HSE prevented UVR‐induced injury by inhibiting excessive ROS production. It reduced the secretion of tumor necrosis TNF‐α, IL‐1α, IL‐1β, IL‐6, and IL‐8 by inhibiting the level of ROS, thus reducing inflammation‐mediated injury to skin cells. In addition, HSE inhibited the expression of various mRNA kinases in the MAPK–ERK/p38/JNK pathway. This downregulated the expression of activator protein‐1 (AP‐1) mRNA and further reduced the secretion of matrix metalloproteinase (MMP)‐1, MMP‐3, and MMP‐9 as well as reduced UVR‐induced injury to the cells. In conclusion, HSE is a broad‐spectrum, natural UV filter with high efficiency and low toxicity that has the potential to be used in sunscreen products. [ABSTRACT FROM AUTHOR]

The efficient three‐component cascade coupling reaction of 3‐haloisoquinolines, haloalkanes, and sp3‐carbon nucleophiles (acetophenone or nitromethane) led to a series of structurally novel 1,2‐disubstituted‐3‐isoquinolinones through the formation of C(sp3)−C(sp2), C−N, and C=O bonds. The NaOAc‐promoted reaction described in this work is simple to operate, environment friendly, and highly selective. [ABSTRACT FROM AUTHOR]

The application of lead halide perovskite nanocrystals is challenged by the lack of strategies in rapid room-temperature synthesis with controlled morphologies. Here, we report on an initial study of adopting organic titanates as a model activator that promotes rapid room-temperature synthesis of shape-controlled, highly luminescent CsPbBr3 nanocrystals and their derivatives. [ABSTRACT FROM AUTHOR]

Abstract: Cesium lead halide perovskite (CsPbX3) nanocrystals (NCs) exhibit an excellent photoelectric performance, which is directly governed by fine‐tuning of the composition and preparation of materials with a special phase structure and morphology. However, it is still facing challenges to achieve highly stable and luminescent CsPbX3 NCs at room temperature. Herein, we report on a novel exchange reaction, in which metal halides MX2 (M=Zn, Mg, Cu, or Ca; X=Cl, Br, or I) solids act as anion source to directly prepare CsPbX3 NCs at room temperature without any pretreatment. Introducing small amount of oleic acid or oleylamine speed up the exchange reaction through different promotion mechanisms. Oleic acid coordinates to the surface of the NCs, which increases the reaction activity, and oleylamine greatly enhances the dissolution of ZnCl2. XRD and TEM tests demonstrate that the cubic phase structure and the morphology of the parent CsPbX3 were well preserved. Moreover, the band‐gap energies and photoluminescence (PL) spectra were readily tunable over the entire visible spectral region of λ=406–685 nm. Our findings could open up the possibilities of using metal halide solids as new anion sources to prepare high‐quality CsPbX3 NCs at room temperature. [ABSTRACT FROM AUTHOR]

Detection of H 2 S in the biological system has attracted enormous attention in recent years. In this work, a new vinyl-functionalized metal-organic framework (MOF), [(Me 2 NH 2 ) 2 ] [Eu 6 (μ 3 -OH) 8 (BDC-CH═CH 2 ) 6 (H 2 O) 6 ] (Eu-BDC-CH═CH 2 , BDC-CH═CH 2 = 2-vinylterephthalic acid), was synthesized under solvothermal conditions. The vinyl groups in the ligands can not only modulate the "antenna effect" of the ligand on Eu 3+ ions but also serve as an exposed reactive site to allow for the quantitative detection of H 2 S by Eu-BDC-CH═CH 2 . The ratiometric fluorescent probe has the advantages of water stability, acid-base stability (pH = 2-11), fast response (<2 min), high selectivity, and sensitivity (LOD = 38.4 μM). We also used Eu-BDC-CH═CH 2 to detect and analyze H 2 S in tap and lake waters, demonstrating the potential of the probe for biological and environmental applications. In addition, the MOF-based agarose hydrogel film allows for the visual detection of H 2 S via a smartphone by identifying the RGB values. The vinyl-functionalized MOF can thus be a powerful sensing platform for H 2 S.

Doping chemistry has become one of the most effective means of tuning materials' properties for diverse applications. In particular for scheelite-type CaWO 4 , high-oxidation-state doping is extremely important, since one may expand the scheelite family and further create prospective candidates for novel applications and/or useful spectral signatures for nuclear forensics. However, the chemistry associated with high-valence doping in scheelite-type CaWO 4 is far from understanding. In this work, a series of scheelite-based materials (Ca 1- x - y - z Eu x K y □ z )WO 4 (□ represents the cation vacancy of the Ca 2+ site) were synthesized by hydrothermal conditions and solid-state methods and comparatively studied. For the bulk prepared by the solid-state method, occupation of high-oxidation-state Eu 3+ at the Ca 2+ sites of CaWO 4 is followed by doping of the low-oxidation-state K + at a nearly equivalent molar amount. The Eu 3+ local symmetry is thus varied from the original S 4 point group symmetry to C 2 v point group symmetry. Surprisingly different from the cases in bulk, for the nanoscale counterparts prepared by hydrothermal conditions, the high-oxidation-state Eu 3+ was incorporated in CaWO 4 at two distinct sites, and its amount is higher than that of the low-oxidation-state K + even though KOH was used as a mineralizer, creating a certain amount of cation vacancies. Consequently, an apparent split emission of 5 D 0 → 7 F 0 was first demonstrated for (Ca 1- x - y - z Eu x K y □ z )WO 4 . The doping chemistry of high oxidation states uncovered in this work not only provides an explanation for the commonly observed spectral changes in rare-earth-ion-modified scheelite structures, but also points out an advanced direction that can guide the design and synthesis of novel functional oxides by solution chemistry routes.

CsCu 2 I 3 mixed with Cs 3 Cu 2 I 5 has shown potential applications as white-light-emitting materials, while their growth, structural evolution behaviors, and their impact on photoluminescence of CsCu 2 I 3 nanocrystals (NCs) are still not known. In this work, we investigated the growth and structural evolution of CsCu 2 I 3 nanocrystals with increasing reaction temperature. At low temperature and in the presence of a high dosage of oleic acid and oleylamine, Cs 3 Cu 2 I 5 nanoparticles, rather than CsCu 2 I 3 NCs, preferred to form in the hot-injection reaction system. Increasing the reaction temperature promoted the formation of CsCu 2 I 3 nanorods. Phase-pure CsCu 2 I 3 nanorods were steadily obtained at 180 °C. Structural evolution from less copper-containing NCs to copper-rich ones in the low-temperature reaction condition is highly related to the coordination of copper ions with OAm. More importantly, accompanying the growth of nanorods and structural evolution from Cu 3 Cs 2 I 5 to CsCu 2 I 3 , the color of photoluminescence emission of NCs changed from blue to nearly white and to yellow, but their photoluminescence quantum yield decreased from 36.00 to 9.86%. The finding in this work would give a view to the structural evolution of copper-containing perovskite-like halides, being helpful for adjusting their photoluminescence in white LEDs., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)

Ongoing demand for accurate self-calibrated noninvasive thermometers for micro-/nano-scale applications, particular biomedical diagnosis, is driving the development of temperature sensors. Here a new type of lanthanide metal-organic framework having near-infrared absorption and near-infrared emission features is presented, and it is based on efficient Nd 3+ -to-Yb 3+ energy transfer in 808 nm photoexcitation. The results show that the ratiometric parameter of Nd 0.5 Yb 0.5 TPTC (TPTC= 1,1':4',1''-terphenyl]-3,3'',5,5''-tetracarboxylic acid) can deliver good exponential-type luminescence response to temperature in the physiological regime (293-328 K) with high relative sensitivity and accurate temperature resolution, as well as good biocompatibility and chemical stability. Such lanthanide-based materials are especially useful in biomedical applications., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The application of lead halide perovskite nanocrystals is challenged by the lack of strategies in rapid room-temperature synthesis with controlled morphologies. Here, we report on an initial study of adopting organic titanates as a model activator that promotes rapid room-temperature synthesis of shape-controlled, highly luminescent CsPbBr3 nanocrystals and their derivatives.