Amphiphilic gold nanoparticles supported on carbon nanotubes: Catalysts for the oxidation of lipophilic compounds by wet peroxide in biphasic systems

作者：Lorencon E^*; Ferreira D C; Resende R R; Krambrock K

来源：Applied Catalysis A: General , 2015, 505: 566-574.

DOI：10.1016/j.apcata.2015.05.016

• Gold nanoparticles
• Carbon nanotubes
• Hydrogen peroxide
• Amphiphilic catalysts
• Oxidation

Amphiphilic catalyst composed of Au NPs supported on a hydrophobic CNT (Au/CNT) has been prepared. The attachment of Au NPs on CNTs sidewall was performed without previous functionalization of CNTs by "in situ" redox reaction between Au3+ ions and negatively charged CNTs. The prepared materials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) showed that metallic Au NPs with mean diameter of 5.8 nm were randomly deposited on CNT surface. The catalytic activity of the Au/CNT was firstly evaluated by the degradation of methylene blue (MB) in aqueous solution. The results from these experiments provide evidence that Au/CNT interacts with the H2O2 aqueous phase to produce highly reactive oxygen species, which mineralize MB molecules. Under biphasic water/cyclohexane mixture, Au/CNT showed amphiphilic behavior, encapsulating and stabilizing emulsion droplets. EPR measurements using PBN (N-t-butyl-alpha-phenylnitrone) in cyclohexane phase as spin trap revealed that hydroxyl radicals chemically generated by interaction of Au/CNT with H2O2 can be transferred to organic phase. Kinetics of hydroxyl radical transfer using DPPH (1,1-diphenyl-2-picrylhydrazyl) as model molecule at different H2O2 concentrations was evaluated. The catalyst was shown to have a relatively high S-tolerant in the oxidation reaction with H2O2, as well as high reusability. This work opens the way for applications of Au/CNT as catalyst in oxidation of a wide range of lipophilic molecules by hydrogen peroxide.

• 出版日期2015-9-25