Electrocatalytic Activity of Palladium Nanocatalysts Supported on Carbon Nanoparticles in Formic Acid Oxidation

采用化学还原法制备了碳纳米粒子支撑的钯纳米结构(Pd-CNP). 透射电镜表征显示在Pd-CNP纳米复合物中，金属Pd呈菜花状结构，粒径约20~30 nm。它们由许多更小的Pd纳米粒子（3~8 nm）组成. 电化学研究表明，虽然Pd-CNP的电化学活性面积比商业Pd黑低40%（可能原因是部分Pd表面被一层碳纳米粒子覆盖），但其对甲酸氧化却表现出更好的电催化活性：质量比活性和面积比活性都比Pd黑高几倍. 催化活性增强的原因可能是碳纳米粒子支撑的Pd纳米结构具有特殊的层次化结构，可以形成更多的活性位，以及表面位更利于反应进行.Palladium nanostructures were deposited onto carbon nanoparticle surface by a chemical reduction method. Transmission electron microscopic studies showed that whereas the resulting metal-carbon (Pd-CNP) nanocomposites exhibited a diameter of 20 to 30 nm, the metal components actually showed a cauliflower-like surface morphology that consisted of numerous smaller Pd nanoparticles (3 to 8 nm). Electrochemical studies showed that the effective surface area of the Pd-CNP nanoparticles was about 40% less than that of Pd black, possibly because the Pd nanoparticles were coated with a layer of carbon nanoparticles; yet, the Pd-CNP nanocomposites exhibited marked enhancement of the electrocatalytic activity in formic acid oxidation, as compared to that of Pd black. In fact, the mass- and surface-specific activities of the former were about three times higher than those of the latter. This improvement was likely a result of the enhanced accessibility of the Pd catalyst surface and the formation of abundant active sites of Pd on the carbon nanoparticle surface due to the hierarchical structure of the metal nanocatalysts.This work was supported, in part, by the National Science Foundation (CHE–1012256 and DMR–0804049) and by the ACS-Petroleum Research Fund (49137–ND10). J. H. was supported, in part, by a research fellowship from the China Scholarship Council. TEM work was performed as a User Project at the National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, which is supported by the US Department of EnergyThis work was supported, in part, by the National Science Foundation (CHE–1012256 and DMR–0804049) and by the ACS-Petroleum Research Fund (49137–ND10). J. H. was supported, in part, by a research fellowship from the China Scholarship Council. TEM work was performed as a User Project at the National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, which is supported by the US Department of Energy作者联系地址：1. 加利福尼亚大学化学与生物化学系，美国 圣克鲁兹 95064; 2. 西北工业大学凝固技术国家重点实验室，陕西 西安710072Author's Address: 1. Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States; 2. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China通讯作者E-mail：[email protected]

Butylphenyl-functionalized palladium nanoparticles as effective catalysts for the electrooxidation of formic acid

Monodisperse butylphenyl-functionalized palladium (Pd-BP, dia. 2.24 nm) nanoparticles were synthesized through co-reduction of butylphenyldiazonium and H(2)PdCl(4) by NaBH(4). Because of this unique surface functionalization and a high specific electro-chemical surface area (122 m(2) g(-1)), the Pd-BP nanoparticles exhibited a mass activity similar to 4.5 times that of commercial Pd black for HCOOH electrooxidation.National Science Foundation[CHE-0832605, CHE-1012258

Inferring Social Functions Available in the Metro Station Area from Passengers’ Staying Activities in Smart Card Data

The function of a metro station area is vital for city planners to consider when establishing a context-aware Transit-Oriented Development policy around the station area. However, the functions of metro station areas are hard to infer using the static land use distribution and other traditional survey datasets. In this paper, we propose a method to infer the functions occurring around the metro station catchment areas according to the patterns of staying activities derived from smart card data. We first define the staying activities by the spatial and temporal constraints of the two consecutive alighting and boarding records from the individual travel profile. Then we cluster and label the whole staying activities by considering the features of duration, frequency, and start time. By analyzing the percentage of different types of aggregated activities happening around each metro station, we cluster and explore the functions of the metro station area. Taking Wuhan as a case study, we analyze the results of Wuhan metro systems and discuss the similarities and differences between the functions and the land use distribution around the station area. The results show that although there exist some agreements, there is also a gap between the human activities and the land uses around the station area. These findings could give us deeper insight into how people act around the stations by metro systems, which will ultimately benefit the urban planning and policy development

Chemical analysis of surface oxygenated moieties of fluorescent carbon nanoparticles

Water-soluble carbon nanoparticles were prepared by refluxing natural gas soot in concentrated nitric acid. The surface of the resulting nanoparticles was found to be decorated with a variety of oxygenated species, as suggested by spectroscopic measurements. Back potentiometric titration of the nanoparticles was employed to quantify the coverage of carboxylic, lactonic, and phenolic moieties on the particle surface by taking advantage of their vast difference of acidity (pK a ). The results were largely consistent with those reported in previous studies with other carbonaceous (nano)materials. Additionally, the presence of ortho-and para-quinone moieties on the nanoparticle surface was confirmed by selective labelling with o-phenylenediamine, as manifested in X-ray photoelectron spectroscopy, photoluminescence, and electrochemical measurements. The results further supported the arguments that the surface functional moieties that were analogous to 9,10-phenanthrenequinone were responsible for the unique photoluminescence of the nanoparticles and the emission might be regulated by surface charge state, as facilitated by the conjugated graphitic core matrix

Ligand-Mediated Electrocatalytic Activity of Pt Nanoparticles for Oxygen Reduction Reactions

High-performance electrocatalysts for oxygen reduction reactions (ORR) are crucial for the development of proton exchange membrane fuel cells (PEMFCs). In this study, a novel method was developed by which the ORR activity of Pt nanoparticles was deliberately manipulated by selective organic capping ligands. By coreduction of diazonium salts and H₂PtCl₄, a series of Pt nanoparticles (core size 2.0–2.5 nm) stabilized by para-substituted (R = −CH₃, −F, −Cl, −OCF₃, and −CF₃) phenyl groups were synthesized. The experimental results demonstrated that the electron-withdrawing capability of the substituent moieties, as manifested by the Hammet substituent constant (σ), plays a key role in controlling the ORR activity, where the higher σ, the higher ORR activity. Within the present experimental context, Pt nanoparticles stabilized by trifluoromethylphenyl groups (Pt–Ar–CF₃) exhibit the highest catalytic activity among the series, with an ORR specific activity 3.2 times higher than that of commercial Pt/C catalysts. The enhanced activity may be correlated with the weakened oxygen adsorption by the electronegative ligands

Platinum nanoparticles functionalized with acetylene derivatives: Electronic conductivity and electrocatalytic activity in oxygen reduction

National Science Foundation [CHE - 1012256, DMR - 0804049]; ACS Petroleum Research Fund [49137 - ND10]Stable platinum nanoparticles were prepared by the self assembly of acetylene derivatives (1-alkynes, 4-ethylphenylacetylene, and 4-tert-butylphenylacetylene) onto bare Pt colloid surfaces. Transmission electron microscopic measurements showed that the nanoparticles exhibited an average core size of 2.85 +/- 0.62 nm. FTIR study showed that with the acetylene ligands adsorbed onto the Pt nanoparticle surface, the C-H vibrational stretches disappeared completely, along with a substantial redshift of the C C vibrational stretch, as compared to those of the monomeric ligands. These were ascribed to the breaking of the C-H bond and the formation of Pt-surface-H and Pt-surface-C at the metal-ligand interface. The conjugated bonding interactions between the triple bond and Pt were found to lead to extensive intraparticle charge delocalization between the acetylene moieties, and hence unique photoluminescence properties of the nanoparticles. For nanoparticles functionalized with 4-ethylphenylacetylene or 4-tert-butylphenylacetylene, the excitation and emission peak positions showed an apparent redshift as compared to those of 1-alkyne-capped platinum nanoparticles. Electronic conductivity measurements of the nanoparticle solids showed that for the nanoparticles capped with 1-alkynes or 4-ethylphenylacetylene, the temperature dependence of the ensemble conductivity was consistent with that of semiconducting materials, whereas for the 4-tert-butylphenylacetylene-capped nanoparticles, metallic behaviors were observed instead. An apparent discrepancy was also observed in the electrocatalytic reduction of oxygen in alkaline media, where the specific activity was all markedly better than that of commercial Pt/C catalysts, with the best performance by the 4-ethyphenylacetylene-capped Pt nanoparticles. These observations were accounted for by the deliberate manipulation of the electronic structure of the Pt nanoparticles by the organic ligands. (C) 2012 Elsevier B.V. All rights reserved

Diagnosis of fungal keratitis caused by Nectria haematococca through next-generation sequencing: review of literature and report of three cases

Objectives: Fungal keratitis (FK) is a kind of serious corneal infection and penetrating keratoplasty (PKP) is needed when medical therapy fails. Although Nectria haematococca is found as endophytes in the roots of some plant species, there has been no report of N. haematococca infection in human. Methods: We reviewed 46 patients who underwent PKP due to FK in our hospital from July 2021 to December 2021, and there were three patients who had relapsed. The next-generation sequencing revealed that all three corneas were infected with N. haematococca. Results: Based on the ocular manifestation and treatment course of three cases, we summarize the characteristics of N. haematococca FK: the scope of corneal infection was widespread with severe hypopyon. The effect of local use of fluconazole and voriconazole was not ideal, and PKP was the main treatment. Even after a large-scale corneal lesion resection, the lesion may recur. The recurrence occurred primarily in the second week after PKP. Conclusion: This is the first clinical report of N. haematococca infection in humans. Compared with the other currently known FK caused by the Fusarium solani species complex, N. haematococca keratitis is more severe and more likely to recur