Chem. Mater. 2010, 22, 4519–4521 4519
DOI:10.1021/cm101191a
oxide, oleic acid or octylamine) in order to prevent the
aggregation of the nanoparticles. These routes offer an
excellent control over size and shape, but adsorbed surfac-
tant may influence the toxicity of the nanoparticles and
decrease both the accessibility to the nanoparticle surface
and also its reactivity, which is a major drawback for appli-
cations in sensors or catalysis.15-17 In 2002, Niederberger
et al. reported an elegant synthesis to TiO2 nanoparticles in
which benzyl alcohol is used as an oxygen donor, a solvent
and a stabilizing agent.18 This “solvent-controlled” route
was later extended to the synthesis of a large variety of metal
oxide nanoparticles.11
In this work we report the synthesis of TiO2 anatase
nanocrystals by reaction at 80-150 °C of TiCl4 with a
stoichiometric amount of diisopropyl ether (iPr2O) in
dichloromethane (eq 1), in the absence of surfactant or
coordinating solvent. This nonhydrolytic route (the so-called
“ether route”) has recently proven successful for the pre-
paration of mesoporous mixed oxide catalysts,19,20 and
silica-based nanoparticles.21 We have previously reported
the synthesis of TiO2 powdersbythisroute,22,23 but it has not
been used so far to prepare titania nanoparticles. The novel
results presented here show that heating dilute solutions of
TiCl4 and iPr2O in CH2Cl2 leads in high yields (>80%) to
phase-pure, unaggregated anatase nanoparticles, as sols
or redispersible powders. In addition, the average size of
the nanoparticles can be adjusted from about 4 to 15 nm
depending on the reaction temperature. Interestingly, the
surface of these nanoparticles present residual chloride and
isopropoxide groups instead of hydroxyl groups. This un-
ique surface chemistry accounts for the observed absence of
aggregation and for the reactivity of the particles, for
instance toward surface silanols or phosphonic acids, afford-
ing simple ways to form nanoparticles monolayers or to
modify the surface of the particles with organic groups.
Reactive and Organosoluble Anatase Nanoparticles by a
Surfactant-Free Nonhydrolytic Synthesis
A. Aboulaich, B. Boury, and P. H. Mutin*
Institut Charles Gerhardt Montpellier, UMR5253 CNRS-
ꢀ
UM2-ENSCM-UM1, Universite Montpellier 2- CC1701,
Place Eugeꢁne Bataillon, 34095 Montpellier Cedex 5, France
Received April 28, 2010
Revised Manuscript Received July 15, 2010
Last year, more than 10000 publications were devoted
to titanium dioxide (TiO2), and among them, more than
500 dealt with nanoparticles and nanostructure aspects of
this material. Owing to its unique properties, TiO2 has
attracted tremendous interest for environmental and en-
ergy applications,1 including photocatalysis,2 water-split-
ting3 and photovoltaic conversion.2,4Accordingly, much
effort has been devoted to finding new synthetic routes to
TiO2 nanoparticles. Since the first report by Colvin’s group
on the nonhydrolytic synthesis of titania anatase nanocryst-
als by reaction of titanium(IV) isopropoxide (Ti(OiPr)4)
with titanium(IV) chloride (TiCl4) in the presence of trioc-
tylphosphine oxide,5 nonhydrolytic (or nonaqueous) sol-
gel routes6 have been found to provide particularly versatile
and cost-effective methods for the synthesis of metal oxide
nanoparticles with various structures, sizes and shapes. Sev-
eral reviews have been recently dedicated to this topic.7-11
Nonhydrolytic routes have been found particularly useful
toaddressseveral drawbacks of hydrolytic sol-gel, such as
high and different hydrolysis-condensation rates of metal
alkoxides, particle agglomeration and poor crystallinity of
the crude precipitates.
Thus, TiO2 nanoparticles have been prepared by different
nonhydrolytic routes involving the reaction of titanium(IV)
chloride or alkoxide precursors with various oxygen
donors.11-14 In most cases, these syntheses were carried
out in the presence of surfactants (e.g., trioctylphosphine
80 - 150°C
CH2Cl2
TiCl4 þ 2iPr2O
TiO þ 4iPrCl
ð1Þ
f
2
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r
2010 American Chemical Society
Published on Web 07/28/2010
pubs.acs.org/cm