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Supporting Information
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Controllable Crystallite and Particle Sizes of WO3
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Particles Prepared by a Spray-Pyrolysis Method and
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Their Photocatalytic Activity
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Osi Arutanti1, Takashi Ogi1,*, Asep Bayu Dani Nandiyanto1,2, Ferry Iskandar3, and Kikuo
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Okuyama1
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1
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1-4-1 Kagamiyama, Higashi Hiroshima 739-8527, Japan
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2
Department of Chemical Engineering, Graduate School of Engineering, Hiroshima University,
Department Kimia, Fakultas Pendidikan Matematika dan Ilmu Pengetahuan Alam, Universitas
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Pendidikan Indonesia, Jl. Dr. Setiabudhi No.229 Bandung 40154, Indonesia
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3
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Indonesia
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*Corresponding author: Email: [email protected]; Tel.: +81-82-424-7850.
Department of Physics, Institut Teknologi Bandung, Jl. Ganesha No. 10 Bandung 40132,
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SI-1
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SI.1. Physicochemical properties of particles at pretreatment condition (Temperature <
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600C)
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Figure S2 shows TG-DTA analysis of ammonium tungstate pentahydrate and SEM
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images of the prepared particles. However, there is a change in mass examined by the TG-DTA
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analysis results. In the temperature of 120C, a mass loss of 6 wt% was found. The mass was
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then slightly decreasing (about 3 wt%) with the increases in temperature up to 240C. In the
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range of 240 to 340C, major decreases in the mass was found (up to 10 wt%). Then, the mass
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loss continued up to temperature of 500C. However, this mass loss was relatively less (about 1
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wt%). The mass was stable after applying temperature of more than 500C. The insert of SEM
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images in Figure S2 show no change in the particle size and morphology with increasing
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temperature significantly.
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Figure S3 shows the SEM images of particles prepared at 10 mmol/L under pretreatment
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process. When the synthesis temperature at 120C, the particles sizes were 740 nm. When the
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synthesis temperature increase to 240C, the particles sizes increased to 923 nm. By increasing
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temperature up to 300C, the particles sizes were 890 nm. Particle size decreased to 677 nm
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when the synthesis temperature increased to 400C. At high synthesis temperature, the particle
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sizes reduced to 562 nm.
SI-2
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Figure S4 presents the photograph images of the prepared particles in every step of
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thermal decomposition process. Samples prepared at temperatures of 120 and 240C were white
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(Figure S4(a)-(b)). Color started to change from white to bluish when using a temperature of
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300C (Figure S4(c)). Then, a change in the color was found at 400C, in which the color
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changed into blue (Figure S4(c)). Further changes in color were found when using temperature
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of 600C. Color transformed into yellowish green (Figure S4(d)).
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Figure S5 shows XRD patterns in the course of thermal decomposition of ammonium
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tungstate pentahydrate. The XRD patterns show that the synthesis temperature allowed material
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with different phases and patterns. Samples were amorphous when prepared using temperature of
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less than 300C. When using 400C, XRD peaks started to appear. Strong peaks were observed
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when using the temperature of 600C. According to JCPDS no. 76 2187, all peaks were WO3
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with hexagonal structure.
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Based on above results, the formation of WO3 particles can be described in the
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following1-3:
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1. At 50 – 120C, anhydrous compound formation occurs. During this process, most water is
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released, in which the simple reaction can be described using the following reaction:
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(NH4)10(W12O41) . 5H2O
(NH4)10[W12O42] + 5 H2O
(1)
SI-3
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2. At 120 – 240C, paratungstate B anion formation happens. This anion is formed from the
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following reactions:
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NH4+
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[H2W12O42]10- + 4H+
NH3 + H+
(2)
[H2W12O42]6- + 2H2O
(3)
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3. At 240 – 400C, hydrate and ammonia are removed from the droplet. This condition leads the
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major degradation of mass in the droplet. In addition, as a consequence of this removal, WO 3
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amorphous is formed (confirming by the appearance of XRD peaks in the sample prepared at
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400C).
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At more than 500C, WO3 amorphous transformation occurs. This condition results the
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formation of WO3 with hexagonal crystal structures (verifying by strong XRD peaks in the
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sample prepared at 600C).
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SI.2. Effect of initial precursor concentration in the synthesis process with non-evaporation
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(temperature of 900C) and evaporation (temperature of 1200C) phenomena
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The XRD patterns of the particles prepared with various initial concentrations at 900C
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are shown in Figure S6. The result showed that all particles were monoclinic WO3 (JCPDS
SI-4
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72-1465). The Scherrer calculation at 22.92 showed that all particles had a constant crystallite
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size of around 29 nm. This result confirms that the change in initial concentration does not alter
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the crystallite size and phase of the prepared particles.
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Figure S7 shows the XRD patterns of particles prepared at 1200C with various
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precursor concentrations. All of particles were WO3 with monoclinic system (JCPDS No.
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72-1465). Different from results in Figure S6, the crystallite sizes under temperature of 1200C
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were different. The crystallite sizes of particles were 18, 25, 41 and 50 nm, corresponding to the
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precursor concentration 2.5; 5;10; and 15 mmol/L, respectively.
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SI.2. Effect of initial precursor concentration in the synthesis process with non-evaporation
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(temperature of 900C) and evaporation (temperature of 1200C) phenomena
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1. Nandiyanto ABD, Arutanti O, Ogi T, Iskandar F, Kim TO, Okuyama K. Synthesis of spherical
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macroporous WO3 particles and their high photocatalytic performance. Chem Eng Sci. 2013 in
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press.
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2. Fait M, Lunk H-J, Feist M, Schneider M, Dann J, Frisk T. Thermal decomposition of
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ammonium paratungstate tetrahydrate under non-reducing conditions: characterization by
SI-5
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thermal
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2008;469:12-22.
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3. Basu A, Sale F. The thermal decomposition of ammonium paratungstate. J Mater Sci.
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1977;12:1115-1124.
analysis,
X-ray
diffraction
and
spectroscopic
methods.
Thermochim
Acta.
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SI-6
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Figure captions
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Figure S1. (a) Nitrogen adsorption and desorption of particles prepared under different synthesis
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temperatures, (b) pore size distribution analysis.
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Figure S2. TG-DTA analysis and insert SEM images of ammonium tungstate pentahydrate.
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Figure S3. SEM images of particles prepared under various temperatures: (a) 120, (b) 240, (c)
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300, (d) 400, and (e) 600C.
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Figure S4. Photograph images in the course of thermal decomposition of ammonium tungstate
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pentahydrate process: (a) 120C, (b) 240C, (c) 300C, (d) 400C, and (e) 600C.
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Figure S5. XRD patterns in the course of thermal decomposition of ammonium tungstate
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pentahydrate.
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Figure S6. XRD Patterns of particles prepared with various initial precursor concentrations at
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900C. Particles were produced using 10 mmol/L of ATP.
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Figure S7. XRD Patterns of particles prepared with various initial precursor concentrations at
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1200C. Particles were produced using 10 mmol/L of ATP.
SI-7
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