Premium
In situ Synthesis of Gold Nanoparticles inside the Pores of MCM‐48 in Supercritical Carbon Dioxide and its Catalytic Application
Author(s) -
Chatterjee M.,
Ikushima Y.,
Hakuta Y.,
Kawanami H.
Publication year - 2006
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200606137
Subject(s) - supercritical carbon dioxide , particle size , supercritical fluid , nanoparticle , chemistry , hamaker constant , chemical engineering , particle (ecology) , van der waals force , mesoporous material , colloidal gold , nanotechnology , catalysis , materials science , organic chemistry , molecule , oceanography , van der waals radius , engineering , geology
Abstract Gold nanoparticles are deposited into the channels of MCM‐48 through a simple H 2 ‐assisted reduction of HAuCl 4 (aqueous solution) in supercritical carbon dioxide medium at 70 °C within 2–4 h. The nanoparticles were characterized by powder X‐ray diffraction (PXRD), N 2 adsorption‐desorption, transmission electron microscopy (TEM), and UV‐Vis spectroscopy. The particle size of the synthesized material is tunable with the pressure (density) of the supercritical carbon dioxide medium. At the fixed temperature (70 °C) and hydrogen pressure [ P (H 2 )=2 MPa], the Au particle size varies from ca. 25 nm to ca. 2 nm with the change in CO 2 pressure from 7 MPa to 17 MPa. At the low solvent density conditions, larger particles of ∼25 nm were obtained. On the contrary, a high solvent density of CO 2 slows down particle aggregation, resulting in the small particle size within the range of 2–5 nm. This change in particle size with CO 2 pressure and the interaction of the particles with the silica support were correlated well with long‐range van der Waals interactions and consequently the Hamaker constant for the gold nanoparticle‐CO 2 ( A 131 ) and silica‐gold core‐CO 2 ( A 132 ), respectively. Supercritical carbon dioxide alone can provide a unique environment for stabilizing gold nanoparticles in the channels of the cubic mesoporous MCM‐48 support and exquisite control of the particle size without perturbing the support structure. The synthesized material is highly stable, recyclable and no metal nanoparticle leaching was observed. The selective hydrogenation of crotonaldehyde with the synthesized material provides convincing evidence that the particles are inside the pores and available to the reactant molecules.