Oxidation reactions may be considered as the heart of chemical synthesis. However, the indiscriminate uses of harsh and corrosive chemicals in this endeavor are threating to the ecosystems, public health, and terrestrial, aquatic, and aerial flora and fauna. Heterogeneous catalysts with various supports are brought to the spotlight because of their excellent capabilities to accelerate the rate of chemical reactions with low cost. They also minimize the use of chemicals in industries and thus are friendly and green to the environment. However, heterogeneous oxidation catalysis are not comprehensively presented in literature. In this short review, we clearly depicted the current state of catalytic oxidation reactions in chemical industries with specific emphasis on heterogeneous catalysts. We outlined here both the synthesis and applications of important oxidation catalysts. We believe it would serve as a reference guide for the selection of oxidation catalysts for both industries and academics.

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It can be concluded that VSC can therefore be considered as potent anticancer agent.

Individual carbon nanotube (CNT) field emission characteristics present a number of advantages for potential applications in electron microscopy and electron beam lithography. Mechanical and electrical reliability of individual CNT cathodes, however, remains a challenge and thus device integration of these cathodes has been limited. In this work, we present an investigation into the reliability issues concerning individual CNT field emission cathodes. We also introduce and analyze the reliability of a novel individual CNT cathode. The cathode structure is composed of a multi-walled carbon nanotube (MWNT) attached by Joule heating to a nickel-coated Si microstructure. The junction of the CNT and the Si microstructure is mechanically and electrically robust to withstand the strong electric field conditions that are typical for field emission devices. An optimal Ni film coating of 25 nm on the Si microstructure is required for mechanical and electrical stability. Experimental current-voltage data for the new cathode structure definitively demonstrates carbon nanotube field emission. Additionally, we demonstrate that our new nanofabrication method is capable of producing sophisticated cathode structures that were previously not realizable, such as one consisting of two parallel MWNTs, with highly controlled CNT lengths with 40 nm accuracy and nanotube-to-nanotube separations of less than 10 µm.

Carbon nanotube pillar arrays (CPAs) for cold field emission applications were grown directly on polished 70∕30at.% NiCr alloy surfaces patterned by photolithography. A carbon nanotube (CNT) pillar is a localized, vertically aligned, and well-ordered group of multiwalled CNTs resulting from van der Waals forces within high-density CNT growth. The edge effect, in which the applied electric field is enhanced along the edge of each pillar, is primarily responsible for the excellent emission properties of CPAs. We achieved efficient emission with turn-on fields as low as 0.9V∕μm and stable current densities as high as 10mA∕cm2 at an applied macroscopic field of 5.7V∕μm. We investigated the effects of pillar aspect ratio, density, and spacing on CPA field emission and quantified the edge effect with respect to pillar aspect ratio through modeling. We also investigated the field emission stability and found substantial improvement with CPAs compared to continuous and patterned CNT films.

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We introduce an innovative geometry carbon nanotube (CNT) field emitter array capable of achieving stable and high current densities. Arrays of toroid CNT pillars were grown directly on bulk metal alloy substrates and on patterned metal catalyst on silicon substrates. Compared to a solid CNT pillar array (CPA), this toroid CPA (tCPA) provides a larger edge area for achieving a higher stable current density of 50 mA/cm2 at an applied dc field of less than 8 V/μm. Electrostatic simulation data confirming the field enhancement at the inner and outer edges of the tCPA are also presented.