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31.
《中国化学快报》2020,31(9):2442-2446
Nanobubble is a rising research field, which attracts more and more attentions due to its potential applications in medical science, catalysis, electrochemistry and etc. To better implement these applications, it is urgent to understand one of the most important mechanisms of nanobubbles, the evolution. However, few attentions have been paid in this aspect because of the methodology difficulties. Here we successfully used dark-field microscopy to study the evolution process of single nanobubbles generated from formic acid dehydrogenation on single Pd-Ag nanoplates. We found some of the nanobubbles in this system can exhibit three distinct states representing different sizes, which can transform among each other. These transitions are not direct but through some intermediate states. Further kinetic analysis reveals complicated mechanisms behind the evolution of single nanobubbles. The results acquired from this study can be applicable to nanobubble systems in general and provide insights into the understanding of mechanisms affecting the stability of nanobubbles and their applications. 相似文献
32.
We report optical and nonlinear optical properties of CuS quantum dots and nanoparticles prepared through a nontoxic, green, one-pot synthesis method. The presence of surface states and defects in the quantum dots are evident from the luminescent behavior and enhanced nonlinear optical properties measured using the open aperture Z-scan, employing 5 ns laser pulses at 532 nm. The quantum dots exhibit large effective third order nonlinear optical coefficients with a relatively lower optical limiting threshold of 2.3 J cm−2, and the optical nonlinearity arises largely from absorption saturation and excited state absorption. Results suggest that these materials are potential candidates for designing efficient optical limiters with applications in laser safety devices. 相似文献
33.
By employing the perturbation formulae of the spin Hamiltonian parameters (SHPs) (g factors gxx, gyy, gzz, hyperfine structure constants Axx, Ayy, Azz and superhyperfine parameters Axx׳, Ayy׳, Azz׳) for a 3d1 ion in orthorhombically elongated octahedra and tetrahedra, the defect structures and the experimental EPR spectra are theoretically and systematically investigated for the two orthorhombic Ti3+ centers C1 and C2 in ZnWO4. Center C1 is ascribed to the impurity Ti3+ at host W6+ site associated with two nearest neighbor oxygen vacancies due to charge compensation. The resultant tetrahedral [TiO4]5– cluster is determined to undergo the local orthorhombic elongation distortion, characterized by the axial distortion angle Δθ (=θ–θ0≈–6.84°) of the local impurity-ligand bond angle θ related to θ0 (≈54.74°) and the perpendicular distortion angle Δε (=ε–ε0≈2.5°) related to ε0 (≈45°) of an ideal tetrahedron because of the Jahn–Teller effect. Center C2 is attributed to Ti3+ on Zn2+ site, and this octahedral [TiO6]9– cluster may experience the local axial elongation ΔZ (≈0.001 Ǻ) and the planar bond angle variation Δφ (≈9.1°) due to the Jahn–Teller effect, resulting in a more regular oxygen octahedron. All the calculated SHPs (i.e., g factors for both centers, the hyperfine structure constants for center C2 and superhyperfine parameters of next nearest neighbor ligand W for center C1) show good agreement with the observed values. However, the theoretical results based on the previous assignment of center C1 as Ti3+ on W6+ site with only one nearest planar oxygen vacancy (i.e., five-fold coordinated octahedral [TiO5]7– cluster) show much worse agreement with the experimental data. The defect structures and the SHPs (especially the g anisotropies) are discussed for both centers. The present studies on the superhyperfine parameters of ligand W6+ for center C1 would be helpful to further investigations on the superhyperfine interactions of cation ligands which were rather scarcely treated before. 相似文献
34.
35.
In situ autocombustion has been developed as a novel and efficient route for the synthesis of perovskite–carbon nanocomposites for the oxygen reduction reaction (ORR) in alkaline media. We demonstrate the synthesis of crystalline LaMnO3 + δ perovskite–Vulcan composite with a high accessibility of active sites and high electronic conductivity required for efficient electrocatalysis. The rotating disc electrode measurements evidenced an excellent activity of the composite for the ORR. 相似文献
36.
Identification of metabolites of rupestonic acid in rat urine by liquid chromatography combined with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry 下载免费PDF全文
Dongyu Gu Yi Yang Qibin Chen Madina Habasi Jiangyu Zhao Haji Akber Aisa 《Biomedical chromatography : BMC》2015,29(4):595-603
Rupestonic acid, a potential anti‐influenza agent, is an important and characteristic compound in Artemisia rupestris L., a well‐known traditional Uighur medicine for the treatment of colds. In the present study, high‐performance liquid chromatography combined with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry was used to detect and identify the metabolites in rat urine after oral administration of rupestonic acid. A total of 10 metabolites were identified or partially characterized. The structure elucidations of the metabolites were performed by comparing the changes in accurate molecular masses and fragment ions with those of the parent compound. The results showed that the main metabolites of rupestonic acid in rat urine were formed by oxidation, hydrogenation and glucuronidation. A metabolism pathway was proposed for the first time based on the characterized structures. This metabolism study can provide essential information for drug discovery, design and clinical application of rupestonic acid. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
37.
The non-resonant Raman spectra of homogeneous bundles of C60 peapods (C60 inserted in single-walled carbon nanotubes) are calculated in the framework of spectral moment method, together with a bond-polarizability model. The evolutions of the low wavenumber range of the Raman spectrum of homogeneous bundles of C60 peapods as a function of the nanotube diameter and the size of bundles are discussed. The effect of the C60 filling factor is investigated in detail. The results are compared to experimental Raman data measured on various samples of C60 peapods. 相似文献
38.
The Effect of Metal‐Ligand Affinity on Fe3O4_Supported Co–Rh Catalysts for Dicyclopentadiene Hydroformylation 下载免费PDF全文
Yubo Ma Shaojun Qing Nana Li Letao Zhang Shouzhu Li Zhixian Gao Hongyi Li Wumanjiang Eli Tianfu Wang 《国际化学动力学杂志》2015,47(10):621-628
The catalytic performances of Co‐Rh/Fe3O4 catalysts modified with phosphine ligands (PPh3) and its analogues on dicyclopentadiene hydroformylation were evaluated. Among these catalysts, Co‐Rh/Fe3O4 modified with tris(p‐trifluoromethylphenyl)phosphine was determined to be effective for monoformyltricyclodecanes production, whereas Co‐Rh/Fe3O4 modified with PPh3 or tri‐p‐tolylphosphine was effective for the diformyltricyclodecanes production. To investigate the ligand effects, the complex catalyst system (Co‐Rh/Fe3O4 and phosphine ligand) was subjected to pretreatment with syngas and then characterized by thermogravimetry and differential thermal analysis (TG‐DTA). It was determined that the threshold decomposition temperature reflected the corresponding Rh‐phosphine interaction strength, affecting the catalytic selectivity toward different products. A weak Rh‐phosphine interaction was desirable to produce monoformyltricyclodecanes with fast reaction kinetics, whereas a strong Rh‐phosphine complex was required for the synthesis of diformyltricyclodecanes. In addition to the selectivity rule shown in the PPh3 series, experiments with other ligands also demonstrated similar selectivity trends. 相似文献
39.
Field-effect transistors (FETs) are one of the most widely-used electronic sensors for continuous monitoring and detection of contaminants such as pharmaceuticals and endocrine-disrupting compounds at low concentrations. FETs have been successfully utilized for the rapid analysis of these environmental pollutants due to their advantageous material properties like the disposability, rapid responses and simplicity. This paper presented an up-to-date overview of applied strategies with different bio-based materials in order to enhance the analytical performances of the designed sensors. Comparison and discussion were made between characteristics of recently engineered FET bio-sensors used for the detection of famous and selected pharmaceutical compounds in the literature. The recent progress in environmental research applications, comments on interesting trends, current challenge for future research in endocrine-disrupting chemicals’ (EDCs) detection using FETs biosensors were highlighted. 相似文献
40.
As a new type of quantum dots (QDs), hexagonal boron nitride quantum dots (BNQDs) exhibit promising potential in the applications of disease diagnosis, fluorescence imaging, biosensing, metal ion detection, and so on, because of their remarkable chemical stability, excellent biocompatibility, low cytotoxicity, and outstanding photoluminescence properties. However, the large-scale fabrication of homogeneous BNQDs still remains challenging. In this article, the properties and common fabrication methods of BNQDs are summarized based on the recent research progress. Then, the corresponding yields, morphologies, and fabrication mechanisms of these as-obtained BNQDs are discussed in detail. Moreover, the applications of these as-obtained BNQDs in different fields are also discussed. This article is expected to inspire new methods and improvements to achieve large-scale fabrication of homogeneous BNQDs, which will enable their practical applications in future. 相似文献