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Raman Spectroscopy for Characterizing Raman Spectroscopy for Characterizing Gold Nanoparticles on Polyaniline Gold Nanoparticles on Polyaniline (PANI) Thin Films(PANI) Thin Films
Yi-Hsiu Chen, Cai-Wei Lin, Chun-Guey Wu, and Yi-Hsiu Chen, Cai-Wei Lin, Chun-Guey Wu, and
Bor-Chen ChangBor-Chen Chang
Department of ChemistryDepartment of ChemistryNational Central UniversityNational Central UniversityChung-Li 32001, TAIWANChung-Li 32001, TAIWAN
AcknowledgementsAcknowledgements
Cai-Wei LinYi-Hsiu Chen (M.S. 2006)
Prof. Chun-Guey Wu
Students In Collaboration with
Financial Supports:National Science Council, TAIWANNational Central University
Pernigraniline Base (PNB)Violet
Emeraldine Base (EB)Blue
NH NH NH NHn
NH NH N Nn
H2N NH N N
n
H AA
N N N Nn
reductionoxidation
reductionoxidationacidbase
Protonated Emeraldine Salt (ES)Green
Leucoemeraldine Base (LEB)Pale Yellow
Polyaniline (PANI) StructuresPolyaniline (PANI) Structures
MacDiarmid and Epstein, Synth. Met. 29, E409 (1989)
Gold (Au) NanoparticlesGold (Au) Nanoparticles
Green OxidationsGreen Oxidations of primary alcohols of primary alcohols.. Catalysts: Catalysts: Au/TiOAu/TiO22 or Au-Pd/TiO or Au-Pd/TiO22. [G. J. Hutchings and co-. [G. J. Hutchings and co-
workers, workers, NatureNature 437437, 1132 (2005) and , 1132 (2005) and ScienceScience 311311, , 362 (2006).]362 (2006).]
We tried the oxidation of benzyl alcohol with We tried the oxidation of benzyl alcohol with Au/PANI as the catalyst. Au/PANI as the catalyst.
CH2OH CHO COOH
O2 O2
Benzyl Alcohol Benzaldehyde Benzoic Acid
Use HPLC to Monitor the OxidationUse HPLC to Monitor the Oxidation
HPLC Chromatogram
CH2OH
Benzyl Alcohol
CHO
Benzaldehyde
COOH
Benzoic AcidInternal Standard:
1,3,5-benzenetricarboxylic acid
HOOC
COOH
COOH
Catalysis StudyCatalysis Study
Au-CHClAu-CHCl33/PANI has a better catalytic activity /PANI has a better catalytic activity
than Au-Hthan Au-H22O/PANI.O/PANI. The temperature-dependency experiments The temperature-dependency experiments
(273K to 353K) show a smaller activation (273K to 353K) show a smaller activation energy of Au-CHClenergy of Au-CHCl33/PANI (ca. 6 kJ mol/PANI (ca. 6 kJ mol-1-1) than ) than
that of Au-Hthat of Au-H22O/PANI (ca. 23 kJ molO/PANI (ca. 23 kJ mol-1-1).).
Scanning Electron Microscopy (SEM) Images
0 100 200 300 400 500 6000
10
20
30
40
50
Diameter (nm)
249 ± 50 nm
0 10 20 30 40 50 600
10
20
30
40
50 31.4 ± 5.0 nm
Diameter (nm)
Au-H2O/PANI
Au-CHCl3/PANI
Au nanoparticles prepared in an aqueous solution.
Au nanoparticles prepared in a chloroform solution.
Questions?Questions? The size distributions in SEM images are The size distributions in SEM images are
INCONSISTENTINCONSISTENT with the catalytic activities.with the catalytic activities. SEM shows only the Au nanoparticles on surface and SEM shows only the Au nanoparticles on surface and
these particles may not be the real catalytic centers. these particles may not be the real catalytic centers. Small angle X-Ray diffraction (XRD) study shows Small angle X-Ray diffraction (XRD) study shows
the particle sizes of the embedded Au nanoparticles the particle sizes of the embedded Au nanoparticles are roughly the same for differently preparation are roughly the same for differently preparation methods.methods.
Why? Spectroscopy?Why? Spectroscopy?
400 600 800 1000 1200 1400 1600 1800
Raman shift (cm-1)
1513
1622
1621
1511 16
2015
81
1515
1582
Raman Spectra for Raman Spectra for Au-HAu-H22O/PANIO/PANI
Benzoid ring C= C stretch.
Quinoid ring C= C stretch.
C= N stretch.
EB
PNB
PNB
LEB
544
541
542
134412
43
1269
1208
1189
1542
1270
1196
1186
1542
1444
599
1473
1335
598
1445
1339
801
596
802
1240
(a) PANI
(b) Au-H2O/PANI before reaction
(c) Au-H2O/PANI after reaction
400 600 800 1000 1200 1400 1600 1800
Raman shift (cm-1)
1620
1587
1342
1208
1621
1516
1341
124511
90
1583
1445
1511
133912
69
1186
59654
2
1620
1581
1240
1542
Benzoid ring C= C stretch.
Quinoid ring C= C stretch.
C= N stretch.
EB
PNB
PNB
LEB
801
798
(a) PANI
(b) Au-CHCl3/PANI before reaction
(c) Au-CHCl3/PANI after reaction
Raman Spectra for Raman Spectra for Au-CHClAu-CHCl33/PANI/PANI
400 600 800 1000 1200 1400 1600 1800
After reaction
Before reaction
400 600 800 1000 1200 1400 1600 1800
Raman shift (cm-1) Raman shift (cm-1)
PANI
Au-H2O/PANI Au-CHCl3/PANI
The bonding between Au nanoparticles and PANI is stronger in Au-CHCl3/PANI than in Au-H2O/PANI.
SummarySummary
Gold nanoparticles prepared by different Gold nanoparticles prepared by different solvents exhibit distinctively different catalytic solvents exhibit distinctively different catalytic activities.activities.
Raman spectroscopy reveals the bonding Raman spectroscopy reveals the bonding differences between different gold differences between different gold nanoparticles.nanoparticles.
Anisotropy Raman spectroscopy? A probe of Anisotropy Raman spectroscopy? A probe of morphology? morphology?