Surface-enhanced Raman scattering (SERS) from molecular probes adsorbed on Au:Ag bimetallic nanoparticles with various compositions was investigated. Au:Ag bimetallic nanoparticles (NPs), with the ...diameters between 3-5 nm, were prepared and characterized by HRTEM and UV-Vis absorption. Their SERS properties were examined by using four different probe molecules, and compared with NPs made of pure Au or Ag. It is found that the SERS property of the alloy NPs is not only dependent on the Au:Ag ratio of the bimetallic NPs, but also on the chemical nature of the SERS probe. For the two positively charged SERS probes, oxazine 720 (Oxa) and Nile Blue A (NBA), the alloy NPs with higher Au content provided the largest SERS signal. However, for the probes 4-hydroxythiophenol (HTP) and thiophenol (TP), the best SERS performance was obtained for the highest Ag ratio. DFT calculations indicated a charge-transfer between Au and Ag atoms in the alloys, creating positively charged domains rich in Ag atom, and negatively charge regions dominated by Au atoms. It is proposed that the probe-specific enhancement is related to the selective binding of probe molecules to the partially charged surface domains in the alloys. Our results suggest that SERS substrate optimizations based on bimetallic nanoparticles should consider the nature of the probes and the electronic-induced effects from the alloys.
The nanoring structure of cycloparaphenylenes (CPPs) can be considered as the shortest fragment of a carbon nanotube. Herein, we successfully prepared a double-walled carbon nanoring of 6CPP⊂12CPP, ...which can be regarded as the shortest double-walled carbon nanotube. 6CPP⊂12CPP was constructed through the supramolecular assembly, and its crystallographic structure was unambiguously determined by single-crystal X-ray diffraction. The host-guest interaction and charge transfer in 6CPP⊂12CPP were disclosed by UV-Vis absorption, fluorescence, and electrochemical studies. Electron paramagnetic resonance (EPR) spectroscopy disclosed the stability of the 6CPP⊂12CPP cation radical, whose unpaired spin was fully delocalized on the inner 6CPP and well protected by outer 12CPP. Moreover, 6CPP⊂12CPP shows highly enhanced photoconductivity and photocurrent under light irradiation compared to those of pristine monomers. The self-assembly behavior of 6CPP⊂12CPP was also studied, and it was found that 6CPP⊂12CPP molecules tend to form a square rod structure in the DMF solution. Thus, these results demonstrate that this double-walled carbon nanoring material has a great potential application in photoelectronic devices and organic semiconductors.
The shortest double-walled carbon nanotube of 6CPP⊂12CPP is constructed through the supramolecular assembly, it shows varied electronic structure, high photoconductivity, and self-assembly behavior deduced by host-guest interactions.
K‐rich adakite‐like rocks (KARs) in post‐collisional settings, such as in Tibet, have been widely linked with the melting of pre‐existing thickened crust. Here, we investigate geochemical data of the ...Late Eocene (38–34 Ma) volcanic rocks including KARs from the southern Qiangtang terrane (SQT) of central Tibet. The data reveal that: (a) the volcanic rocks define a fractionation trend from high‐K alkaline basalt to high‐K calc‐alkaline rhyolite, with a continuous compositional range and (b) they are characterized by a narrow range of depleted Sr–Nd isotopic compositions relative to the pre‐Eocene SQT crust. We contend that the KARs in the SQT resulted from fractional crystallization of hydrous, alkaline melts derived from the lithospheric mantle where fractionation was dominated by amphibole and plagioclase. Partial melting of the lithospheric mantle beneath the SQT was possibly triggered by thermal perturbations owing to the north‐directed subduction of the Indian continental lithosphere beneath southern Tibet.
Plain Language Summary
Adakites were originally defined as silica‐rich magmas produced by melting of basalts in subducting oceanic crust. They are Na‐rich with low K2O and K2O/Na2O, and are characterized by high Sr/Y and La/Yb and low Y and Yb. In post‐collisional settings, such as in Tibet, silica‐rich magmatic rocks with high Sr/Y and La/Yb have been identified, but they are not sodic as true adakites, and are rich in K2O, forming K‐rich adakite‐like rocks (KARs). They have been linked with the melting of pre‐existing crustal rocks at high pressures where garnet is present. We investigate geochemical data of the Late Eocene (38–34 Ma) volcanic rocks that include KARs from the southern Qiangtang terrane (SQT) of central Tibet. We conclude that these KARs were not products of crustal melting at high pressures, but resulted from extreme fractional crystallization of lithospheric mantle‐derived, hydrous, primitive alkaline melts. Given that extreme fractional crystallization commonly occurs in a compressive regime, we argue that the lithospheric mantle underneath the SQT underwent melting during a compressive regime possibly due to thermal perturbations, driven by north‐directed subduction of the Indian continental lithosphere beneath southern Tibet.
Key Points
Late Eocene K‐rich adakite‐like rocks (KARs) in the S. Qiangtang terrane resulted from fractional crystallization of a primitive alkaline melt
Fractionation was dominated by amphibole and plagioclase
KARs from the S. Qiantang terrane have a different origin from those of the Lhasa terrane
A photocatalytic chemodivergent reaction for the selectivity formation of C–S and C–N bonds in a controlled manner was proposed. The reaction medium, either neutral or acidic, is critical to dictate ...the formation of 2-amino-1,3,4-thiadiazoles and 1,2,4-triazole-3-thiones from isothiocyanates and hydrazones. This is a practical protocol to achieve the chemoselectivity under mild and metal-free conditions.
Toll‐like receptors (TLRs) recognize pathogen‐associated molecular patterns and trigger an inflammatory response via the myeloid differential factor 88 (MyD88)‐dependent and toll‐interleukin‐1 ...receptor domain‐containing adapter‐inducing interferon‐β (TRIF)‐dependent pathways. Lindenane type sesquiterpene dimers (LSDs) are characteristic metabolites of plants belonging to the genus Sarcandra (Chloranthaceae). The aim of this study was to evaluate the potential anti‐inflammatory effects of the LSDs shizukaol D (1) and sarcandrolide E (2) on lipopolysaccharides (LPS)‐stimulated RAW264.7 macrophages in vitro, and explore the underlying mechanisms. Both LSDs neutralized the LPS‐induced morphological changes and production of nitric oxide (NO), as determined by CCK‐8 assay and Griess assay, respectively. Furthermore, shizukaol D (1) and sarcandrolide E (2) downregulated interferon β (IFNβ), tumor necrosis factor α (TNFα) and interleukin‐1β (IL‐1β) mRNA levels as measured by reverse transcription polymerase chain reaction (RT‐PCR), and inhibited the phosphorylation of nuclear factor kappa B p65 (p65), nuclear factor kappa‐Bα (IκBα), Jun N‐terminal kinase (JNK), extracellular regulated kinase (ERK), mitogen‐activated protein kinase p38 (p38), MyD88, IL‐1RI‐associated protein kinase 1 (IRAK1), and transforming growth factor‐β‐activated kinase 1 (TAK1) proteins in the Western blotting assay. In conclusion, LSDs can alleviate the inflammatory response by inhibiting the TLR/MyD88 signalling pathway.
Six new limonoids, munropins A−F (1–6), were isolated from the aerial parts of a Chinese medicinal plant, Munronia pinnata (Meliaceae). The structures of 1–6 were assigned by detailed analyses of ...their spectroscopic data. Munropins A (1) and B (2) are limonoids possessing a prieurianin skeleton with α,β-unsaturated γ-lactam moieties at C-17. Munropins C (3), D (4), and E (5) are also prieurianin type limonoids with an α,β-unsaturated γ-lactone moiety, an acetyl group, and an acetoxyacetyl group at C-17, respectively. Munropin F (6) was assigned as a nimbolinin type limonoid with a γ-hydroxy-α,β-unsaturated γ-lactone moiety.
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•A Chinese traditional herbal medicine, Munronia pinnata, was studied.•Prieurianin and nimbolinin type limonoids were isolated from M. pinnata.•Their structures were elucidated by detailed spectroscopic analyses.•Munropins A and B are rare limonoids with γ-lactam moieties at C-17.
In the course of a phytochemical and chemotaxonomical investigation of
species (Fagaceae), three new phenolic compounds, (3
,1'
)-1'-(6″-
...-galloyl-β-d-gluco-pyranosyl)oxyethyl-3-hydroxy-dihydrofuran-2(3
)-one (
), (2
,3
)-2-2'-(galloyl)oxyethyl-dihydroxybutanoic acid (
), and (3
,4
)-3-hydroxymethyl-3,4-dihydro-5,6,7-trihydroxy-4-(4'-hydroxy-3'-methoxyphenyl)-1
-2-benzopyran-1-one (
) were isolated from the fresh leaves of
. In addition, a known phenolic glycoside, gentisic acid 5-
-α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranoside (
) was also isolated and identified. Their structures were elucidated by means of spectroscopic methods including one- and two-dimensional NMR techniques.
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A class of novel mogrol derivatives modified on A ring were synthesized. The screening result showed that indole-fused derivatives exhibited lower toxicity and better ...anti-inflammatory activity in LPS-induced RAW 264.7 cells model than mogrol and other compounds. Derivative B8 exerted superior inhibitory result of NO production (IC50 = 5.05 μM) and inhibitory ability of TNF-α and IL-6 secretion to mogrol through iNOS/NF-κB pathway. Besides, the CCK8 assay was performed to evaluate their anti-proliferative activity against non-small cell lung cancer including A549, NCI-H460, H1299 and H1975 cells. Compared with mogrol, compound B8 showed moderate anti-proliferative activities against A549 and H1975 cells, while derivatives bearing α, β-unsaturated ketone scaffold displayed broad-spectrum growth inhibition against four cell lines. Among them, compound A9 showed 12-fold higher activity than mogrol against H1299 and H1975 cells. The suppressive effect on expression level of p-p65 might account for the compound A9-induced growth inhibition and cell cycle arrest at G1 phase.
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•Investigation of a medicinal plant Sarcandra glabra gave sarcaglabrins A-C.•Their structures were assigned by spectroscopic analyses including ECD calculation.•Sarcaglabrin A was ...assigned as a new conjugate of C15 and C10 terpenes.
A new C25 terpene consisting of C15 and C10 terpenes, sarcaglabrin A, and two new sesquiterpene dimers, sarcaglabrins B and C, were isolated from the aerial parts of a medicinal plant Sarcandra glabra used in Guangxi Zhuang Autonomous Region, China. Their structures were elucidated on the basis of detailed spectroscopic analyses including calculation of the ECD spectrum. Sarcaglabrin A was assigned as a conjugate of lindenane type sesquiterpene and ocimene type monoterpene, while sarcaglabrins B and C were elucidated to be lindenane sesquiterpene dimers. Their cytotoxicity against human cancer cell lines were evaluated.
Intertwined spin and charge orders have been widely studied in high-temperature superconductors, since their fluctuations may facilitate electron pairing; however, they are rarely identified in ...heavily electron-doped iron selenides. Here, using scanning tunneling microscopy, we show that when the superconductivity of (Li
Fe
OH)Fe
Se is suppressed by introducing Fe-site defects, a short-ranged checkerboard charge order emerges, propagating along the Fe-Fe directions with an approximately 2a
period. It persists throughout the whole phase space tuned by Fe-site defect density, from a defect-pinned local pattern in optimally doped samples to an extended order in samples with lower T
or non-superconducting. Intriguingly, our simulations indicate that the charge order is likely driven by multiple-Q spin density waves originating from the spin fluctuations observed by inelastic neutron scattering. Our study proves the presence of a competing order in heavily electron-doped iron selenides, and demonstrates the potential of charge order as a tool to detect spin fluctuations.
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