Catalysis with Metal Nanoparticles Immobilized within the Pores of Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are highly ordered crystalline porous materials prepared by the self-assembly of metal ions and organic linkers having low-density framework structures of diversified topologies with tunable pore sizes and exceptionally large surface areas. Other than outstanding gas/molecule storage properties, loading of metal nanoparticles (MNPs) into the pores of MOFs could afford heterogeneous catalysts having advantages of controlling the particle growth to a nanosize region, resulting in highly active sites and enhanced catalytic performances, and these entrapped MNPs within MOF pores could be accessed by reactants for chemical transformations. This is a rapidly developing research area, and this Perspective addresses current achievements and future challenges for diverse MOF-immobilized MNPs within their pores, focusing especially on their preparation, characterization, and application as heterogeneous catalysts.

Surfactant-free Pd nanoparticles immobilized to a metal–organic framework with size- and location-dependent catalytic selectivity

Pd nanoparticles immobilized to a metal–organic framework show size- and location-dependent catalytic activity and selectivity for vanillin reduction.

Anticandidal effect of Ocimum sanctum essential oil and its synergy with fluconazole and ketoconazole

Holy basil, Ocimum sanctum (L.) is time-honored for its medicinal properties; however its antimicrobial characteristics are used only in 'Ayurvedic medicines'. Attention has been drawn to antifungal activity and a possible synergistic antifungal effect of Ocimum sanctum essential oil (OSEO) and established azole antimycotics-fluconazole and ketoconazole. To put forward this approach, antifungal activity has been assessed in seventy four fluconazole-sensitive and sixteen fluconazole-resistant Candida isolates. Hemolytic activity on human erythrocytes was also studied to rule out the possibility of allied additional cytotoxicity. The observed selectively fungicidal characteristics signify a promising candidature of O. sanctum essential oil as an antifungal agent in combinational treatments for candidosis.

From a metal–organic framework to hierarchical high surface-area hollow octahedral carbon cages

High surface-area hollow octahedral carbon cages have been fabricated for the first time by carbonization of a metal–organic framework, which exhibit significant CO₂ and H₂ adsorption capacities and dye uptake.

Structural variation in Zn(ii) coordination polymers built with a semi-rigid tetracarboxylate and different pyridine linkers: synthesis and selective CO2 adsorption studies

The C_2v or C_s symmetry in the flexible 3,3′,5,5′-tetracarboxydiphenylmethane ligand directs the stability and porosity of the resulting frameworks in the presence of Zn(ii) ions, and pyridine linkers of comparable lengths.

Management of heparin allergy in pregnancy

Thromboembolic disease during pregnancy has traditionally been treated with heparin. If heparin cannot be used, then treatment options remain limited. Despite the recent availability of new anticoagulation agents, data relating to their use during pregnancy is lacking. Hirudin, a relatively new anti-thrombotic agent, through animal models has been shown to have a very low transplacental transfer, thus making it a candidate drug to be used during pregnancy in case of heparin allergy. This report describes a case of heparin allergy in a pregnant patient with recurrent DVT that was successfully managed with hirudin and coumadin.

Factors influencing recent dental graduates' location and sector of employment in Victoria

BACKGROUND

Recruitment and retention of dentists in the public sector and rural areas in Victoria has become increasingly difficult in recent years. There are little available data on the factors that influence the sector and location of practice of new dental graduates. The objective of this study was to investigate the factors considered by new graduates in determining the location and sector of employment after graduation, and influencing any early changes in career path.

METHODS

Questionnaires were sent to dentists who Mgraduated from The Univrersity of Melbourne from graduated from The University of Melbourne from 2000-2003 who were currently practising in Victoria. There were 154 subjects to whom questionnaires were sent and 109 useable questionnaires were returned, a response rate of 74 per cent.

RESULTS

Upon graduation, 53 per cent of the new graduates chose to work in the private sector only, compared to 15 per cent in public sector only and 33 per cent in both. At present, 71 per cent work in the private sector only, 17 per cent in the public sector only and 12 per cent in both. The most important factors for choosing to work in the private sector were receiving broad range of clinical experience, opportunities to familiarize with practice management and providing a continuity of care. The principal factors for practising in the public sector were clinical mentoring and advice, consolidating clinical skills and work environment. Initially, 48 per cent of the sample chose to work in metropolitan areas only, 39 per cent in rural areas only and 13 per cent in both. Factors that influenced the decision to work in rural areas were the broad range of clinical experience and remuneration, while the main factors for choosing to work in metropolitan areas were lifestyle and proximity to family and friends.

CONCLUSIONS

This study found that a large proportion of new dental graduates initially chose to work in the public sector and rural areas on graduation primarily as a means of consolidating their clinical skills. However, retention of dentists in both these areas appears to be a problem, with less than 10 per cent of 2000-2001 graduates still than 10 per cent of 2000-2001 graduates still working in the public sector and only 20 per cent of 2000-2001 graduates still working in rural areas.

Dual Single-Atomic Co-Mn Sites in Metal-Organic-Framework-Derived N-Doped Nanoporous Carbon for Electrochemical Oxygen Reduction

Synthesizing dual single-atom catalysts (DSACs) with atomically isolated metal pairs is a challenging task but can be an effective way to enhance the performance for electrochemical oxygen reduction reaction (ORR). Herein, well-defined DSACs of Co-Mn, stabilized in N-doped porous carbon polyhedra (named CoMn/NC), are synthesized using high-temperature pyrolysis of a Co/Mn-doped zeolitic imidazolate framework. The atomically isolated Co-Mn site in CoMn/NC is recognized by combining microscopic as well as spectroscopic techniques. CoMn/NC exhibited excellent ORR activities in alkaline (E1/2 = 0.89 V) as well as in acidic (E1/2 = 0.82 V) electrolytes with long-term durability and enhanced methanol tolerance. Density functional theory (DFT) suggests that the Co-Mn site is efficiently activating the O-O bond via bridging adsorption, decisive for the 4e- oxygen reduction process. Though the Co-Mn sites favor O2 activation via the dissociative ORR mechanism, stronger adsorption of the intermediates in the dissociative path degrades the overall ORR activity. Our DFT studies conclude that the ORR on an Co-Mn site mainly occurs via bridging side-on O2 adsorption following thermodynamically and kinetically favorable associative mechanistic pathways with a lower overpotential and activation barrier. CoMn/NC performed excellently as a cathode in a proton exchange membrane (PEM) fuel cell and rechargeable Zn-air battery with high peak power densities of 970 and 176 mW cm-2, respectively. This work provides the guidelines for the rational design and synthesis of nonprecious DSACs for enhancing the ORR activity as well as the robustness of DSACs and suggests a design of multifunctional robust electrocatalysts for energy storage and conversion devices.