Tomer Zidki

Water oxidation catalyzed by cobalt(II) adsorbed on silica nanoparticles.

A novel, highly efficient, and stable water oxidation catalyst was prepared by a pH-controlled adsorption of Co(II) on ~10 nm diameter silica nanoparticles. A lower limit of ~300 s(-1) per cobalt atom for the catalyst turnover frequency in oxygen evolution was estimated, which attests to a very high catalytic activity. Electron microscopy revealed that cobalt is adsorbed on the SiO(2) nanoparticle surfaces as small (1-2 nm) clusters of Co(OH)(2). This catalyst is optically transparent over the entire UV-vis range and is thus suitable for mechanistic investigations by time-resolved spectroscopic techniques.

Reactions of alkyl-radicals with gold and silver nanoparticles in aqueous solutions

Silver and gold nanoparticles are very efficient catalysts for the dimerization of methyl-radicals in aqueous solutions. The rate constants for the reaction of methyl-radicals with the gold and silver nanoparticles were measured and found to be 3.7 x 10(8) M(-1) s(-1) and 1.4 x 10(9) M(-1) s(-1), respectively. The results thus suggest that alkyl-radicals, also not reducing ones, are scavenged by these nanoparticles. This might explain the role, if such a role exists, of these nanoparticles in medical applications.

Photochemical induced growth and aggregation of metal nanoparticles in diode-array spectrophotometer via excited dimethyl-sulfoxide

Ag(0) and Au(0) nanoparticles suspended in dilute aqueous solutions containing (CH(3))(2)SO are photochemically unstable. The light source of a diode-array spectrophotometer induces, within less than a minute, particle growth and aggregation. The results indicate that this process is triggered by UV light absorption by the (CH(3))(2)SO.

Effect of Hydrogen Pretreatment of Platinum Nanoparticles on their Catalytic Properties: Reactions with Alkyl Radicals – A Mechanistic Study

Methyl radicals react with platinum nanoparticles (NPs) suspended in aqueous solutions to form (Pt0‐NPs)‐(CH3)n as a stable major product. Hydrogen gas treatment of the Pt0‐NPs affects the composition of the products and the surface reactions. The results clearly point out that pretreatment of Pt0‐NPs and (Pt0‐NPs)‐(CH3)n with H2 considerably affects their reactions with methyl radicals. The implications of the results on catalytic processes are discussed.

The effect of negatively charged metallic nanocatalysts on their reactions with alkyl radicals

Abstract Stored electrons on Au and Ag nanoparticles (NPs) have been found to catalyze various reduction processes initiated by ionizing irradiation or light illumination in which the NPs act as “nano-electrodes”. In the present study, we explored the effect of charging colloidal gold and silver NPs on their reaction with methyl radicals, ·CH3. The results show that charging the colloidal metal NPs by excess of electrons, (NP)n−, affected their reaction mechanism with methyl radicals and resulted in different product composition in comparison to the analogous reactions with uncharged particles. These results should be considered in photo(electro)catalytic processes when alkyl radicals are formed near the catalyst surface. Graphical Abstract