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Continuous-Flow Synthesis of Inorganic Nanoparticles in Near-and Supercritical Water

Edward Evans 

University of Nottingham, Nottingham, United Kingdom




Edward Evans, Paul A. Hamley, Edward Lester, Albertina CabaƄas,
Alexandr A. Galkin and Martyn Poliakoff, Clean Technology Research
Group, School of Chemistry, University of Nottingham, Nottingham NG7
2RD, England

Water has its critical point at 374C, 218 atm. Supercritical and
near-critical water synthesis techniques provide a simple, one-step
route to inorganic oxide nanoparticles with high surface area,
avoiding the use of toxic organic solvents. Flow reactors allow the
straightforward control of pressure and enable reactions to take place
in a very short time. This lecture will review work in this area,
particularly in our laboratory in Nottingham.
Pioneering work in this field was performed by Arai and
co-workers[1][1]. Their method was further developed in Nottingham for
the synthesis of single-phase mixed oxides of cerium and zirconium in
near-critical water; the ratio of Ce:Zr could be changed by changing
the ratio of the two metals in the precursor solution[2][2],[3][3].
These oxides are used as oxygen storing components in automotive
three-way catalysts. Conditions were 300C, 25MPa, yielding samples
with large surface areas (up to 180 m2g-1) and small particle sizes
Similar conditions were used for the synthesis of spinel-type
compounds, MFe[2]O[4] (where M = Fe, Mn, Co, Ni, Cu or Zn)[4][4],
producing particles with size 5-15nm.
Nanoparticles of the perovskite, La[2]CuO[4], a catalyst for many
oxidation reactions, were produced in two steps[5][5]: the flow
reactor was used to make an intimate mixture of CuO and La(OH)[3] that
was then annealed at 600C for 5h to form the desired perovskite which
proved to be eight times more catalytically active than samples
prepared by standard ceramic methods.

[6][1]. Arai, K. and Adschiri, T., Fluid Phase Equilibria, 1999,
158-160, 673
[7][2]. A. Cabanas, J. A. Darr, E. Lester and M. Poliakoff, Chem.
Commun., 2000, 901
[8][3]. A. Cabanas, J. A. Darr, E. Lester and M. Poliakoff, J. Mater.
Chem., 2001, 11, 561
[9][4]. A. Cabanas and M. Poliakoff, J. Mat. Chem., 2001, 11, 1408
[10][5]. A. A. Galkin, B. G. Kostyuk, V. V. Lunin and M. Poliakoff,
Angew. Chem.-Int. Ed., 2000, 39, 2738
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Presentation: oral at E-MRS Fall Meeting 2002, by Edward Evans
See On-line Journal of E-MRS Fall Meeting 2002

Submitted: 2003-02-16 17:33
Revised:   2009-06-08 12:55