Supporting Information
From nanocorals to nanorods to nanoflowers
nanoarchitecture for efficient dye-sensitized solar
cells at relatively low film thickness: All Hydrothermal
Process
Sawanta S. Mali[a], [d], Chirayath A. Betty[b], Popatrao N. Bhosale[c] and Pramod S.
Patil*[a] Chang Kook Hong[d]*
[a]Thin
Film Materials Laboratory, Department of Physics, Shivaji University, Kolhapur, India -
416 004. E-mail: psp_phy@unishivaji.ac.in; sawantamali@yahoo.co.in; Fax: +91-02312691533; Tel: +91-231-2609229
[b]
[c]
Chemistry Division, Bhabha Atomic Research Center (BARC), Trombay-Mumbai, India -85
Materials Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur M. S.
India -416004
[d]School
of Applied Chemical Engineering, Chonnam National University, Gwangju, 500-757
(South Korea),
*Corresponding Author: E-mail: psp_phy@unishivaji.ac.in (PSP) Fax: +91-0231-2691533;
Tel: +91-231-2609229, hongck@chonnam.ac.kr (CKH)sawantamali@yahoo.co.in (SSM)
Tel:062-530-0635; Fax: 062-530-1849
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S1. Experimental Section
S.1.1 Effective Dye Loading
Dye-sensitized solar cells were assembled as follows: TiO2 films were immersed in a
mild piranha solution (1 part Millipore water, 3 parts sulfuric acid, and 2 parts hydrogen
peroxide) for 30 minutes at 50 0C, rinsed in Millipore water and ethanol and dried in a oven
at 60 0C. These TiO2 films were subsequently soaked in ethanolic 0.3 mM N719 dye
solution at room temperature for 24 h in dark and then washed carefully in ethanol. The
dyed film was rinsed in acetonitrile and dried in air.
S.1.2 Characterizations
The surface morphology of the films was examined by analyzing the Field emission
scanning electron microscopy (FESEM) images recorded using a scanning electron
microscope (Hitachi S4800, Japan). The TiO2 films were coated with 10 nm platinum layer
using Polaron scanning electron microscope sputter coating unit (Japan) before recording
the SEM images. The thickness of the resulting TiO2 thin films was estimated using surface
profiler (Ambios XP-1) and also from FESEM cross sections. Transmission Electron
Microscope (JEOL 3010) with a selected-area electron diffractometer (SAED) TEM was
used to examine the structural morphology and crystalline nature of the TiO2
nanostructures at an accelerating voltage of 200 kV. The structural properties of the TiO2
films were studied from X-ray diffraction (XRD) patterns recorded using an X-ray
diffractometer (Philips, PW 3710, Almelo, Holland) operated at 25 kV, 20 mA with CuKα
radiation (λ = 1.5406 Å). The Raman spectra of the films were recorded in the spectral
range of 35–4000 cm−1 using Raman spectrometer (Bruker MultiRAM, Germany Make)
Nd:YAG laser source with excitation wavelength of 1064 nm and resolution
4 cm-1.
Electrochemical Impedance Spectroscopy (EIS) was conducted using electrochemical
workstation (model Iviumstat Ivium Technologies B.V., Eindhoven, the Netherlands). The
EIS data was analyzed using Z-view 2.8d software for equivalent circuit. The specific
surface area of TiO2 samples were measured at the N2 adsorption–desorption isotherm by
the Brunauer–Emmett–Teller (BET, for specific surface area) and Barrett–Joyner–Halenda
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(BJH, for average pore diameter) methods using a Quanta chrome Autosorb 1-MP analyzer.
UV–visible absorbance spectra of TiO2 thin films were obtained using a UV–visible
spectrophotometer (UV-1800, Shimadzu, Japan).
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Figures
T (220)
T (213)
T (105)
T (211)
T (200)
T (112)
Intensity (a.u.)
T (103)
T (101)
FTO/TiO2
Anatase:01-21-1272
SnO2:46-1088
20
30
40
50
60
70
80
2 (Degree)
Figure S1 X-ray diffraction pattern of the synthesized anatase TiO2 TNC film on FTO coated
glass substrate. Vertical lines a) magenta JCPDS-21-1272 b) black FTO Ref [1].
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(002)
(310)
(301)
(211)
220)
(110)
(002)
(101)
(111)
Intensity (a.u.)
(110)
(b)
20
30
(002)
(310)
(301)
(211)
220)
(110)
(002)
(101)
(111)
(110)
(a)
60
50
40
2/ (Degree)
70
Figure S2 X-ray diffraction patterns of the synthesized rutile TiO2 films on glass substrate
(a) TNR; (b) TNF [Ref [2]].
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The structural identification of the phase formed was studied with the help of XRD
technique. Figure S1 shows the XRD pattern of TNC sample. The comparison of ‘d’ values in
observed XRD patterns with those from the standard diffraction data (JCPDS # 21 1272)
confirms the crystallization of TiO2 phase with tetragonal anatase crystal symmetry. Eight
distinct reflections such as (004), (200), (105), (211), (204), (116) and (008) besides a
prominent (101) reflection are seen. The other peaks shown by (■) symbols are due to the
FTO substrate. Figure S2 shows the XRD pattern of TiO2 TNR and TNF samples matched
well with the standard pattern of rutile (JCPDS 01-089-4920). Eleven distinct reflections such
as (100), (002), (101), (111), (211), (220), (002), (310), (301) and (112) besides a
prominent (110) reflection are seen.
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Transmitance (T%)
(c)
(b)
(a)
1800
1600
1400
1200
1000
800
-1
600
Wavenumber (cm )
Figure S3 IR spectra of (a) TiO2, (b) TNF-[BMIM][HSO4] and (c) [BMIM][HSO4] ionic liquid.
The band at 664 cm−1 is due to the stretching of Ti–O–Ti. The sharp peak at 1400
cm−1 can be attributed to the lattice vibrations of TiO2. The absorption band at 1627 cm−1
was caused by a bending vibration of coordinated H2
[HSO4] is immobilized on to TiO2 blocks , the peak of the hydroxyl groups of quasi-aligned
TiO2 nanowires downshifts by 60 cm−1 (from νmax, 3477 to 3397 cm−1), indicating a strong
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interaction between [CMIM][HSO4] and the TiO2 surface. Besides, the absorption bands at
1386, 1213, and 647 cm−1 in Figure S2 (c), which was assigned to the skeleton stretching
vibration of the methylimidazoliurn ring, the absorption spectra indicate strong
interactions between [CMIM][HSO4] and the TiO2 surface as shown by star.
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Figure
S4
Nitrogen
adsorption-desorption
isotherms
plots
for
different
TiO2
nanostructures (a) commercial P25 powder, (b) TNC (c) TNR and (d) TNF samples. The
samples were preheated at 350°C before the analyses.
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References:
[1] Mali S.S., Shinde P.S., Betty C.A., Bhosale P.N., Lee W.J., Patil P.S. Nanocoral architecture
of TiO2 by hydrothermal process: Synthesis and Characterization, Appl. Surf. Sci. 2011, 257,
9737- 9746.
[2] Mali S.S., Betty C.A., Bhosale P.N., Devan R.S., Ma Y.R., Kolekar S.S., Patil P.S.
Hydrothermal synthesis of rutile TiO2 nanoflowers using Brønsted Acidic Ionic Liquid
[BAIL]: Synthesis, characterization and growth mechanism, CrystEngComm, 2012,
14,1920-1924.
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