Glycothermal Synthesis of Assembled Vanadium Oxide Nanostructures for Gas
Sensing Applications
Haitao Fu,a Xuchuan Jiang, a Xiaohong Yang,a Aibing Yu,a Dawei Su,b and Guoxiu Wangb
a) School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia
b) Department of Chemistry, University of Technology Sydney, Sydney, NSW 2007, Australia
To understand the formation and growth process of vanadium oxide precursors, various parameters have
been investigated in this study, such as pH, temperature, concentration, and surface modifiers, as
detailed below.
Effect of pH
The pH of the system was adjusted from 1 to 5, 7, and 10, while other parameters were kept as constants
(0.15M of Na3VO4 in EG, 120 °C, 12h). Figure S1 shows the TEM images that VEG nanopaticles with
different shape and size were formed at different pH. From the figures, it can be seen that only the
product obtained at pH=1 is uniform rod-like particles with a diameter of ~ 200 nm and a length of 1 μm
(Fig. S1a), which generated from decomposition of microurchins. While other products obtained at
other pH values are irregular shapes. The H+ and its concentration are critical to the formation of urchinlike and rod-like nanoparticles, as described in Equations 1 and 2. That is, the pH greatly affects the
morphology of the obtained VEG particles, and higher pH can help to form microurchins and nanorods.
Effect of temperature
Figure S2 shows the TEM images that the shape and size of VEG nanoparticles are little affected by the
temperature. At 120 and 160 °C (other parameters: 0.15 M of Na3VO4, pH= 1, and t= 12 h), the rod-like
nanoparticles can be prepared. The discrepancy is that high temperature (160°C) can cause the high
reaction rate, compared with low temperature (120 °C).

To whom correspondence should be addressed. Email: xcjiang@unsw.edu.au.
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Effect of concentration of Na3VO4
Different concentrations of Na3VO4 were tested. Figure S3 shows the TEM images of the products
obtained with different concentrations of Na3VO4. Similar with temperature, the concentrations affect
little on the shape and size of VEG particles.
Effect of surface modifiers
We also investigated the effect of surfactants of cationic (CTAB), anionic (SDS) and polymer (PVP).
The molar ratios of the surface modifiers to vanadium are from 0.5, 1 to 2. The ratio little affected the
morphologies of products. Figure S4 shows the hollow microurchins with different morphologies
prepared by the existence of different modifiers. In the present system, the surfactants are proposed to
act as a “soft template”, in which the CTAB, PVP and SDS molecules may form micelles in polar EG
solution The vanadyl ester nanospheres formed at the early stage are easily adsorbed on the surface of
the micelles through the vanadyl groups, and then form urchin-like microstructures.
The similar morphology has been observed by Cao et al.(Cao et al. 2005) who reported the hollow V2O5
structure synthesized by assistance of PVP. Shi et al.(Shi et al. 2007) synthesized V2O5 nanobelts in the
present of SDS as a shape controller via a hydrothermal method. Luca (Luca and Hook 1997; Luca et al.
1995) demonstrated the mesostructure of vanadium oxide via the combination of CTAB (CTA+) and
vanadate in aqueous solution. Besides vanadium oxides, the hollow microurchins have also been
observed in other oxides, such as α-MnO2 (Li et al. 2006), γ-MnO2 (Fu et al. 2009), and TiO2 (Yang and
Zeng 2004). That is, the surfactants may be helpful for the formation of hollow urchin-like particles
under the reported conditions.
Surface area
Figure S6 presents the nitrogen gas adsorption and desorption isotherm of the V2O5 microurchins,
nanorods, and hollow microurchins. The specific areas calculated by standard multipoint BrunauerEmmett-Teller (BET) method. The surface areas of these three samples show a little difference.
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Figure S1 TEM images showing the effect of pH on the VEG particle shape and size: a) pH= 1, b) pH=
5, c) pH= 7, d) pH= 10.
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Figure S2 TEM images showing the effect of the temperature on the VEG particle shape and size: a)
120, and b) 160 °C.
Figure S3 TEM images showing the effect of the concentration of Na3VO4 on the VEG particle shape
and size: a) 0.1 M, b) 0.15 M, and 0.2 M.
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Figure S4 SEM images of the effect of surfactants on the morphology of vanadium oxide precursor:
(A&B) SDS, (C&D) PVP, and (E&F) CTAB.
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Figure S5 XPS pattern of carbon (C1s peak) in the product of V2O3 calcined in N2.
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Surface
area=7.7 m2 g-1
Surface
area=4.8 m2 g-1
Figure S6 The N2 adsorption/desorption isotherms of different shapes of V2O5: a) microurchins, b)
Surface
area=8.1 m2 g-1
nanorods, and c) hollow microurchins. The inset shows the corresponding pore distribution of the
sample.
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Figure S7 Schematic diagram of the gas sensing measurement system.
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