Ligand-free Gold Nanoparticles as a Reference Material for Kinetic Modelling of Catalytic Reduction of 4-Nitrophenol
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The reduction of 4-nitrophenol by sodium borohydride is a common model reaction to test the catalytic activity of metal nanoparticles. As all reaction steps proceed solely on the surface of the metal nanoparticles (Langmuir–Hinshelwood model), ligand-coverage of metal nanoparticles impedes the merging of theory and experiment. Therefore we analyzed the catalytic activity of bare gold nanoparticles prepared by laser ablation in liquid without any stabilizers or ligands. The catalytic reaction is characterized by a full kinetic analysis including 4-hydroxylaminophenol as an intermediate species. Excellent agreement between theory and experiment is found. Moreover, the suspension of the nanoparticles remains stable. Hence, ligand-free nanoparticles can be used as a reference material for mechanistic studies of catalytic reactions. In addition, the analysis shows that gold nanoparticles synthesized by laser ablation are among the most active catalysts for this reaction.
KeywordsLaser ablation in liquid Ligand-free gold nanoparticles Langmuir–Hinshelwood kinetics
This study was supported by the German federal ministry of education and research (BMBF) within the young investigator competition NanoMatFutur (project INNOKAT, FKZ 03X5523). AZ gratefully acknowledges financial support of the IAS at TUM via the Moessbauer Fellowship. We thank Prof. J. Nakamura (University of Tsukuba) for his support in X-ray diffraction and high resolution transmission electron microscopy and Prof. H. Nienhaus and Dr. U. Hagemann (University of Duisburg-Essen) for their help in X-ray photoelectron spectroscopy.