PNNL-13501 - Pacific Northwest National Laboratory

Removal of the organics (in Figure 3a) by heat treatment
at 450°C will result in crystal growth. However, in the
presence of metal oxide spacer, such as MoO3
(Figure 3b), particle size and architectural features are
stabilized due to interfacial diffusional barriers at the
nanoscale. Figure 4 shows the entropies of
nanoarchitectured materials and nanoparticle mechanical
mixture relative to bulk rutile TiO2 and bulk baddelyite
ZrO2. The two sets of entropy data are similar, and this
indicates that the stability of the nanoarchitectured
materials is due primarily to the presence of diffusion
barriers (see Figure 3b).
(a)
micelle
(b)
Summary and Conclusions
micelle
TiO2 nanocrystal
TiO2 nanocrystal
metal oxide spacer
Figure 3. A cross-section view of nucleation of TiO 2
nanocrystallites at the surface of CTAC micelles: (a) TiO 2
only, (b) with metal oxide spacer
We have synthesized a series of solid-state
nanocrystalline TiO2- (MoO3) core-shell materials from a
novel surfactant micelle assisted reaction pathway. The
structural and optical properties are governed by, and a
direct result of, the intimate nanoarchitectured
arrangement between the TiO2 core and the MoO3 shell.
We also have a fundamental understanding of the reaction
mechanism for the synthesis of nanoarchitectured
materials and the underlying thermodynamics properties
that gives rise to their stability. The TiO2-(MoO3)
compounds are potentially a significant step in the right
direction for understanding how to synthesize and design
advanced metal oxides with fundamentally new physical
and chemical properties.
ent halpy (kJ/mol)
45
40
35
30
25
20
15
10
5
0
References
Haus JW, HS Shou, I Honma, and H Komiyama. 1993.
“Quantum confinement in semiconductor heterostructure
nanometer-size particles.” Phys. ReV.B 47, 1359.
Kortan AR, et al. 1990. J. Am. Chem. Soc. 112, 1327.
Elder SH, Y Gao, X Li, J Liu, DE McCready, and
CF Windisch, Jr. 1998. “Zirconia-stabilized 25-Å TiO2
anatase crystallites in a mesoporous structure.” Chem.
Mater. 10, 3140.
Nozik AJ and R Memming. 1996. “Physical chemistry
of semiconductor-liquid interfaces.” J. Phys. Chem. 100,
13061.
Publication
nanoarchitectured materials
(measured)
nanoparticle mechanical
mixture (calculated)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
x in xZrO 2 -(1-x)TiO 2
Figure 4. Comparison of entropies of nanoarchitectured
materials and nanoparticle mechanical mixture relative to
bulk rutile TiO 2 and bulk baddelyite ZrO 2
Elder SH, FM Cot, Y Su, SM Heald, AM Tyryshkin,
MK Bowman, Y Gao, AG Joly, ML Balmer,
AC Kolwaite, KA Magrini, and DM Blake. 2000. “The
discovery and study of nanocrystalline TiO2-(MoO3)
core-shell materials.” J. Am. Chem. Soc. 122:5138-5146.
Materials Science and Technology 329