We report the structures, stability and catalysis properties of two Ag21 nanoclusters, namely Ag21(H2BTCA)3(O2PPh2)6SbF6 (1) and Ag21(C≡CC6H3‐3,5‐R2)6(O2PPh2)10SbF6 (2) ...(H4BTCA=p‐tert‐butylthiacalix4arene, R=OMe). Both Ag21 structures possess an identical icosahedral kernel that is surrounded by eight peripheral Ag atoms. Single‐crystal structural analysis and ESI‐MS revealed that 1 is an 8‐electron cluster and 2 has four free electrons. Theoretical results show that the P‐symmetry orbitals are found as HOMO‐1 and HOMO states in 1, and the frontier unoccupied molecular orbitals (LUMO, LUMO+1 and LUMO+2) show D‐character, indicating 1 is a superatomic cluster with an electronically closed shell 1S21P6, while 2 has an incomplete shell configuration 1S21P2. These two Ag21 clusters show superior stability under ambient conditions, and 1 is robust even at 90 °C in toluene and under oxidative conditions (30 % H2O2). Significantly, 2 exhibits much higher activity than 1 as catalyst in the reduction of 4‐nitrophenol. This work demonstrates that ligands can influence the electronic structures of silver clusters, and further affect their stability and catalytic performance.
Two diphenylphosphonate‐protected silver nanoclusters, Ag21(H2BTCA)3(O2PPh2)6SbF6 (1) and Ag21(C≡CC6H3‐3,5‐R2)6(O2PPh2)10SbF6 (2), have identical icosahedral kernels but different number of free electrons. Cluster 2 exhibits much higher activity than the more stable 1 in the catalytic reduction of 4‐nitrophenol. This work shows that the electronic structures of metal nanoclusters can be modulated via different combinations of ligands.
The first all‐amidinate‐protected gold nanocluster Au28(Ph−form)12(OTf)2 (Ph‐form=N,N′‐diphenylformamidinate) (Au28) has been synthesized and structurally resolved. Single crystal X‐ray diffraction ...reveals that Au28 has a compact Au4@Au24 tetrahedral core–shell structure of T symmetry, which is fully protected by 12 bridging formamidinate ligands. This cluster is quite robust as indicated by the fact that it can stay intact in solution at 80 °C for 6 d. It exhibits excellent catalytic performance for the electroreduction of CO2 with 96.5 % Faradaic efficiency (FE) at −0.57 V and a maximum TOF of 1731 h−1 at −0.87 V. Its superior stability is also manifested in the fact that the supported catalyst Au28/CNTs maintains stable potentials at ca. −0.69 V for 40 h with FE(CO)s>91 %. A superatomic electron configuration of 1S21P62S21D4 has been clarified by DFT computations, and the strong gold–ligand binding and geometric shell closure account for the superior stability of Au28.
The first all‐amidinate‐supported gold nanocluster Au28 has been synthesized and structurally resolved. This cluster is quite robust manifested by the fact that it can stay intact in solution at 80 °C for 6 d and maintain high FE(CO)s and activity over 40 hour operation for electroreduction of CO2. The strong gold–ligand binding and geometric closure account for the superior stability of Au28.
Anhedonia is associated with reward-processing deficits of the dopamine system, which may increase the risk of depression. Nevertheless, few previous studies have examined the influence of hedonic ...tone on event-related potential (ERP) measures of reward processing in major depressive disorder. A simple gambling task was used to elicit feedback negativity (FN), an ERP component elicited by feedback indicating gain versus loss, in 27 patients with major depression and 27 healthy participants. We found that participants with depression were characterized by reduced FN responses, especially towards monetary gains, but not losses, compared with healthy individuals. In addition, the amplitude of FN to gain feedback in participants with depression was related to anhedonia severity and depressive symptoms. These findings indicate an association between low hedonic capacity and reduction in FN. As a neural measure of reward sensitivity, FN may be generated in part by reward-related activity.
•Depressed patients demonstrated reduced feedback negativity (FN).•The FN amplitude to gain in depressed patients was related to anhedonia severity and depressive symptoms.•Trait anhedonia may exert a direct influence on the neutral activities to feedback processing.
Abstract
Electron band topology is combined with intrinsic magnetic orders in MnBi
2
Te
4
, leading to novel quantum phases. Here we investigate collective spin excitations (i.e. magnons) and spin ...fluctuations in atomically thin MnBi
2
Te
4
flakes using Raman spectroscopy. In a two-septuple layer with non-trivial topology, magnon characteristics evolve as an external magnetic field tunes the ground state through three ordered phases: antiferromagnet, canted antiferromagnet, and ferromagnet. The Raman selection rules are determined by both the crystal symmetry and magnetic order while the magnon energy is determined by different interaction terms. Using non-interacting spin-wave theory, we extract the spin-wave gap at zero magnetic field, an anisotropy energy, and interlayer exchange in bilayers. We also find magnetic fluctuations increase with reduced thickness, which may contribute to a less robust magnetic order in single layers.
Growing attention has been paid to nanoclusters with face-centered cubic (fcc) metal kernels, due to its structural similarity to bulk metals. We demonstrate that the use of tetradentate ...formamidinate ligands facilitate the construction of two fcc silver nanoclusters: Ag52(5-F-dpf)16Cl4(SbF6)2 (Ag 52 , 5-F-Hdpf = N,N′-di(5-fluoro-2-pyridinyl)formamidine) and Ag53(5-Me-dpf)18(NO3)5 (Ag 53 , 5-Me-Hdpf = N,N′-di(5-methyl-2-pyridinyl)formamidine). Single-crystal X-ray structural analysis revealed that the silver atoms in both clusters are in a layer-by-layer arrangement, which can be viewed as a portion of the fcc packing of silver. The nitrogen donors of amidinate ligands selectively passivate the {111} facets. All silver atoms are involved in the fcc packing, that is, no staple motifs are observed due to the linear arrangement of the four N donors of the dpf ligands. The characteristic optical absorption bands of Ag 52 and Ag 53 have been studied with a time-dependent density functional theory. This work provides a facile access to assembling atomically precise fcc-type nanoclusters and shows the prospect of amidinates as protecting ligands in synthesizing metal nanoclusters.
•Ultrasonic modified starch and quercetin combined was formed non-inclusion complex.•Addition of quercetin could protect the damage of starch granule size by ultrasonic.•Quercetin and starch binding ...through H-bonds and van der Waals interactions.•Ultrasonic modified and quercetin combined affected starch physicochemical properties.
In order to provide a reference for improving the physicochemical properties of starch, the study of starch polyphenol complex interaction has aroused considerable interest. As a common method of starch modification, ultrasound can make starch granules have voids and cracks, and make starch and polyphenols combine more closely. In this research, canistel seed starch was modified by ultrasonic treatment alone or combined with quercetin. The molecular structure, particle characteristics and properties of starch were evaluated. With the increase of ultrasonic temperature, the particle size of the dextrinized starch granules increased, but the addition of quercetin could protect the destruction of starch granule size by ultrasonic; X-ray diffraction and infrared spectra indicated that quercetin was bound to the surface of canistel seed starch through hydrogen bonding, and the complex and the original starch had the same crystal structure and increased crystallinity; by molecular simulation, quercetin bound inside the starch molecular helix preserved the crystalline helical configuration of starch to some extent and inhibited the complete unhelicalization of starch molecules. Meanwhile, hydrogen bonding was the main driving force for the binding of starch molecules to quercetin, and van der Waals interactions also promoted the binding of both. In the physicochemical properties, as the temperature increased after the combination of ultrasonic modified starch combined with quercetin, the solubility, swelling force and apparent viscosity of the compound increased significantly, and it has higher stability and shear resistance.
Great attention has been paid to nanoclusters having face-centered-cubic (fcc) metal kernels, because of the similarity of metal packing to that of bulk gold. So far, there is no precedent example of ...an all-alkynyl-protected fcc gold nanocluster with more than 100 gold atoms. We report the synthesis and total structure determination of an alkynyl-protected gold nanocluster NEt3H2Au110(p-CF3C6H4CC)48 (Au 110 ). It has an fcc Au86 kernel with 24 peripheral Au(CCR)2 staples. The Au86 kernel consists of six close packing layers in the pattern of Au6:Au16:Au21:Au21:Au16:Au6. Electronic absorption spectroscopy shows Au 110 has a molecular-like discrete electronic structure, and transient absorption experiments reveal its nonmetallic nature.
The acaricidal activity of Adonis coerulea extracts was investigated against Psoroptes cuniculi. The aqueous, methanol, acetic ether and petroleum ether extracts all showed marked acaricidal activity ...in vitro. Especially, the acetic ether extract possessed strong toxicity against mites in vitro with LT50 values 0.743h, 2.730h, 5.919h and 22.536h at concentrations of 500, 250, 125 and 62.5mg/ml, respectively. At the same time, the acetic ether extract showed the best effectiveness topically to infested rabbits in vivo. After three times treatment, at the day 20, rabbits treated with A. coerulea extract were observed only small scabs or secretions in ear canal, but no mites. These findings suggested that as a potential insecticide, A. coerulea should be studied further to develop active components or a new acaricidal drug.
Dear Editor, Persistent infection with human papillomavirus (HPV) is the main cause of cervical cancer. Screening of cervical specimens for high-risk human papillomaviruses (HR-HPV) has become a ...routine part of patient care in most countries. The Roche cobas 4800 system (Roche Molecular Systems Inc., Pleasanton, CA, USA), a fully automated system that uses in vitro qualitative real-time PCR technology, displays high sensitivity and specificity for HR-HPV detection 1. However, a small proportion of invalid results may occur in specimens showing mucopurulent discharge because of pipetting errors, clot formation, or failed amplification, which could cause a delay in the results and lead to additional waiting time for patients and extra work hours for staff, although most cases are resolved by vortexing the specimens and retesting. To the best of our knowledge, no researcher has tried to overcome this problem by pretreating specimens with an appropriate concentration of Sputasol (Oxoid Ltd., Basingstoke, United Kingdom); Sputasol (dithiothreitol 1.4%) has been used to aid culturing and DNA extraction from sputum specimens in some laboratories 2. Here, we propose a standard method to improve HR-HPV detection without affecting the performance of the cobas 4800 HPV system. KCI Citation Count: 0
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