نتایج جستجو برای: transition metal ions

تعداد نتایج: 546120  

Journal: :Nature chemistry 2011
Jin Suntivich Hubert A Gasteiger Naoaki Yabuuchi Haruyuki Nakanishi John B Goodenough Yang Shao-Horn

The prohibitive cost and scarcity of the noble-metal catalysts needed for catalysing the oxygen reduction reaction (ORR) in fuel cells and metal-air batteries limit the commercialization of these clean-energy technologies. Identifying a catalyst design principle that links material properties to the catalytic activity can accelerate the search for highly active and abundant transition-metal-oxi...

Journal: :Nature chemistry 2013
Manish Chhowalla Hyeon Suk Shin Goki Eda Lain-Jong Li Kian Ping Loh Hua Zhang

Ultrathin two-dimensional nanosheets of layered transition metal dichalcogenides (TMDs) are fundamentally and technologically intriguing. In contrast to the graphene sheet, they are chemically versatile. Mono- or few-layered TMDs - obtained either through exfoliation of bulk materials or bottom-up syntheses - are direct-gap semiconductors whose bandgap energy, as well as carrier type (n- or p-t...

2017
Maria Carmen Catapano Václav Tvrdý Jana Karlíčková Thomas Migkos Kateřina Valentová Vladimír Křen Přemysl Mladěnka

Interaction of flavonoids with transition metals can be partially responsible for their impact on humans. Stoichiometry of the iron/copper complex with a flavonoid glycoside isoquercitrin, a frequent component of food supplements, was assessed using competitive and non-competitive methods in four (patho)physiologically-relevant pH values (4.5. 5.5, 6.8, and 7.5). Isoquercitrin chelated all test...

2017
Subrata Panja Boyang Hua Diego Zegarra Taekjip Ha Sarah A Woodson

Twister is a small ribozyme present in almost all kingdoms of life that rapidly self-cleaves in variety of divalent metal ions. We used activity assays, bulk FRET and single-molecule FRET (smFRET) to understand how different metal ions promote folding and self-cleavage of the Oryza sativa twister ribozyme. Although most ribozymes require additional Mg2+ for catalysis, twister inverts this expec...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 1993
T A Steitz J A Steitz

A mechanism is proposed for the RNA-catalyzed reactions involved in RNA splicing and RNase P hydrolysis of precursor tRNA. The mechanism postulates that chemical catalysis is facilitated by two divalent metal ions 3.9 A apart, as in phosphoryl transfer reactions catalyzed by protein enzymes, such as the 3',5'-exonuclease of Escherichia coli DNA polymerase I. One metal ion activates the attackin...

Journal: :journal of particle science & technology 2015
mohsen mehdipour ghazi milad mohammadi hamid modarres

in present study, molecular dynamics simulation of cadmium (ii), lead (ii) and copper (ii) removal from aqueous electrolyte solutions using the ion-exchange process with the zeolite particles was done. the results showed that, most of the particles had the highest affinity of ion exchanging with lead (ii) and the lowest affinity with copper (ii). the calculated mean ion-exchange ratios showed t...

Journal: :Dalton transactions 2014
Yaokang Lv Jun Cheng Peter D Matthews Juan Pedro Holgado Janina Willkomm Michal Leskes Alexander Steiner Dieter Fenske Timothy C King Paul T Wood Lihua Gan Richard M Lambert Dominic S Wright

To what extent the presence of transition metal ions can affect the optical properties of structurally well-defined, metal-doped polyoxotitanium (POT) cages is a key question in respect to how closely these species model technologically important metal-doped TiO2. This also has direct implications to the potential applications of these organically-soluble inorganic cages as photocatalytic redox...

Journal: :Analytical sciences : the international journal of the Japan Society for Analytical Chemistry 2008
Koji Machitani Hidefumi Sakamoto Yoshio Nakahara Keiichi Kimura

Tetraazacyclododecane and tetraazacyclotetradecane derivatives bearing a spirobenzopyran and three carboxymethyl moieties, 1 and 2, and a diethylenetriamine derivative bearing a spirobenzopyran and four carboxymethyl moieties 3 were synthesized. The isomerization behaviors based on the spirobenzopyran moiety of these ligands were studied by UV-visible spectrophotometry in aqueous solutions cont...

Journal: :Annual review of physical chemistry 1997
G U Bublitz S G Boxer

Stark spectroscopy has been applied to a wide range of molecular systems and materials. A generally useful method for obtaining electronic and vibrational Stark spectra that does not require sophisticated equipment is described. By working with frozen glasses it is possible to study nearly any molecular system, including ions and proteins. Quantitative analysis of the spectra provides informati...

Journal: :Analytica chimica acta 2007
Bekir Salih Omür Celikbiçak Serhat Döker Mehmet Doğan

Poly(N-(hydroxymethyl)methacrylamide)-1-allyl-2-thiourea) hydrogels, poly(NHMMA-ATU), were synthesized by gamma radiation using (60)Co gamma source in the ternary mixture of NHMMA-ATU-H(2)O. These hydrogels were used for the specific gold, silver, platinum and palladium recovery, pre-concentration and matrix elimination from the solutions containing trace amounts of precious metal ions. Elimina...

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