Deposition of Co nanoparticles on mesoporous-silica supports using supercritical CO2

A. SASTRE; S. ASPROMONTE; A. BOIX; M. J. COCERO; E. ALONSO

The Hague

Encuentro; 13th European Meeting On Supercritical Fluids; 2011

ISASF

Mesoporous materials with uniform and tailorable pore dimensions and high surface areas, are currently being employed in a number of applications that include catalysis [1,2] and their used as templates for controlling the aspect ratio of quantum-confined nanoparticles and nanowires [3], among others. MCM41 is a mesoporous-silica material that contains unidirectional channels arranged in a regular hexagonal pattern in the range 15 -100 Å. In recent times, in the literature, it can be found attempts to insert transition metals [4], such as, Cu, Ca, Mg, Ti, Cr, Mn or Fe into the MCM41 framework, and this incorporation has been generally performed by wet impregnation or co-precipitation [5]. Supercritical fluid deposition (SFD) is an alternative technique in which an organometallic precursor is dissolved in supercritical carbon dioxide (scCO2), and its subsequent decomposition allows the precipitation and deposition of metal or metal oxides over the mesoporous support. It takes advantage of the excellent physical properties of scCO2, which are easily adjustable with small variations of pressure and/or temperature. The low viscosity, high diffusivity and zero surface tension of scCO2 achieve better penetrating and wetting of pores than conventional liquid solvents. Furthermore, simple removal from the substrate by depressurization avoids problems of solvent residues or pore collapse. This work presents the deposition of Co nanoparticles into MCM41 and Al-MCM41 mesoporous matrix by the decomposition of cobaltocene (CoCp2) using supercritical carbon dioxide, and its subsequent characterization by means of different techniques, such as SEM/EDX, TEM, SAXS or Laser Raman Spectroscopy (LRS). Experimental results showing the effect of precursor concentration, pressure and operation time on the obtained composite materials will be presented in the full work.