1
2
3
4
3
5
6
Osi Arutanti 1 , Takashi Ogi 1 ,*, Asep Bayu Dani Nandiyanto 1,2 , Ferry Iskandar 3 , and Kikuo
Okuyama 1
7 1 Department of Chemical Engineering, Graduate School of Engineering, Hiroshima University,
8 1-4-1 Kagamiyama, Higashi Hiroshima 739-8527, Japan
9 2 Department Kimia, Fakultas Pendidikan Matematika dan Ilmu Pengetahuan Alam, Universitas
10 Pendidikan Indonesia, Jl. Dr. Setiabudhi No.229 Bandung 40154, Indonesia
11 3 Department of Physics, Institut Teknologi Bandung, Jl. Ganesha No. 10 Bandung 40132,
12 Indonesia
13 *Corresponding author: Email: ogit@hiroshima-u.ac.jp; Tel.: +81-82-424-7850.
14
SI-1

1 SI.1. Physicochemical properties of particles at pretreatment condition (Temperature <
2 600  C)
3 Figure S2 shows TG-DTA analysis of ammonium tungstate pentahydrate and SEM
4 images of the prepared particles. However, there is a change in mass examined by the TG-DTA
5 analysis results. In the temperature of 120  C, a mass loss of 6 wt% was found. The mass was
6 then slightly decreasing (about 3 wt%) with the increases in temperature up to 240  C. In the
7 range of 240 to 340  C, major decreases in the mass was found (up to 10 wt%). Then, the mass
8 loss continued up to temperature of 500  C. However, this mass loss was relatively less (about 1
9 wt%). The mass was stable after applying temperature of more than 500  C. The insert of SEM
10 images in Figure S2 show no change in the particle size and morphology with increasing
11 temperature significantly.
12 Figure S3 shows the SEM images of particles prepared at 10 mmol/L under pretreatment
13 process. When the synthesis temperature at 120  C, the particles sizes were 740 nm. When the
14 synthesis temperature increase to 240  C, the particles sizes increased to 923 nm. By increasing
15 temperature up to 300  C, the particles sizes were 890 nm. Particle size decreased to 677 nm
16 when the synthesis temperature increased to 400  C. At high synthesis temperature, the particle
17 sizes reduced to 562 nm.
SI-2

1 Figure S4 presents the photograph images of the prepared particles in every step of
2 thermal decomposition process. Samples prepared at temperatures of 120 and 240  C were white
3 ( Figure S4(a)-(b) ). Color started to change from white to bluish when using a temperature of
4 300  C ( Figure S4(c) ). Then, a change in the color was found at 400  C, in which the color
5 changed into blue ( Figure S4(c) ). Further changes in color were found when using temperature
6 of 600  C. Color transformed into yellowish green ( Figure S4(d) ).
7 Figure S5 shows XRD patterns in the course of thermal decomposition of ammonium
8 tungstate pentahydrate. The XRD patterns show that the synthesis temperature allowed material
9 with different phases and patterns. Samples were amorphous when prepared using temperature of
10 less than 300  C. When using 400  C, XRD peaks started to appear. Strong peaks were observed
11 when using the temperature of 600  C. According to JCPDS no. 76 2187, all peaks were WO
3
12 with hexagonal structure.
13 Based on above results, the formation of WO
3
particles can be described in the
14 following 1-3 :
15 1.
At 50 – 120  C, anhydrous compound formation occurs. During this process, most water is
16 released, in which the simple reaction can be described using the following reaction:
17 (NH
4
)
10
(W
12
O
41
) . 5H
2
O (NH
4
)
10
[W
12
O
42
] + 5 H
2
O (1)
SI-3

1 2.
At 120 – 240  C, paratungstate B anion formation happens. This anion is formed from the
2 following reactions:
3 NH
4
+ NH
3
+ H + (2)
4 [H
2
W
12
O
42
] 10- + 4H + [H
2
W
12
O
42
] 6 + 2H
2
O (3)
5 3.
At 240 – 400  C, hydrate and ammonia are removed from the droplet. This condition leads the
6 major degradation of mass in the droplet. In addition, as a consequence of this removal, WO
3
7 amorphous is formed (confirming by the appearance of XRD peaks in the sample prepared at
8 400  C).
9 At more than 500  C, WO
3
amorphous transformation occurs. This condition results the
10 formation of WO
3
with hexagonal crystal structures (verifying by strong XRD peaks in the
11 sample prepared at 600  C).
12
13 SI.2. Effect of initial precursor concentration in the synthesis process with non-evaporation
14 (temperature of 900  C) and evaporation (temperature of 1200  C) phenomena
15 The XRD patterns of the particles prepared with various initial concentrations at 900  C
16 are shown in Figure S6 . The result showed that all particles were monoclinic WO
3
(JCPDS
SI-4

1 72-1465). The Scherrer calculation at 22.92
 showed that all particles had a constant crystallite
2 size of around 29 nm. This result confirms that the change in initial concentration does not alter
3 the crystallite size and phase of the prepared particles.
4 Figure S7 shows the XRD patterns of particles prepared at 1200  C with various
5 precursor concentrations. All of particles were WO
3
with monoclinic system (JCPDS No.
6 72-1465). Different from results in Figure S6 , the crystallite sizes under temperature of 1200  C
7 were different. The crystallite sizes of particles were 18, 25, 41 and 50 nm, corresponding to the
8 precursor concentration 2.5; 5;10; and 15 mmol/L, respectively.
9
10 SI.2. Effect of initial precursor concentration in the synthesis process with non-evaporation
11 (temperature of 900  C) and evaporation (temperature of 1200  C) phenomena
12
1. Nandiyanto ABD, Arutanti O, Ogi T, Iskandar F, Kim TO, Okuyama K. Synthesis of spherical
13 macroporous WO
3
particles and their high photocatalytic performance. Chem Eng Sci . 2013 in
14 press.
15
2. Fait M, Lunk H-J, Feist M, Schneider M, Dann J, Frisk T. Thermal decomposition of
16 ammonium paratungstate tetrahydrate under non-reducing conditions: characterization by
SI-5

1 thermal analysis, X-ray diffraction and spectroscopic methods. Thermochim Acta .
2
2008;469:12-22.
3
3. Basu A, Sale F. The thermal decomposition of ammonium paratungstate. J Mater Sci .
4
1977;12:1115-1124.
5
6
SI-6

1 Figure captions
2
Figure S1. (a) Nitrogen adsorption and desorption of particles prepared under different synthesis
3 temperatures, (b) pore size distribution analysis.
4
Figure S2 . TG-DTA analysis and insert SEM images of ammonium tungstate pentahydrate.
5
Figure S3 . SEM images of particles prepared under various temperatures: (a) 120, (b) 240, (c)
6
300, (d) 400, and (e) 600

C.
7 Figure S4 . Photograph images in the course of thermal decomposition of ammonium tungstate
8 pentahydrate process: (a) 120

C, (b) 240

C, (c) 300

C, (d) 400

C, and (e) 600

C.
9 Figure S5. XRD patterns in the course of thermal decomposition of ammonium tungstate
10 pentahydrate.
11 Figure S6 . XRD Patterns of particles prepared with various initial precursor concentrations at
12
900

C. Particles were produced using 10 mmol/L of ATP.
13 Figure S7 . XRD Patterns of particles prepared with various initial precursor concentrations at
14
1200

C. Particles were produced using 10 mmol/L of ATP.
SI-7