Silver/Polyaniline Composite Nanotubes: One-Step Synthesis and Electrocatalytic Activity for

Neurotransmitter Dopamine

Yu Gao, Decai Shan, Fei Cao, Jian Gong,* Xia Li, Hui-yan Ma, Zhong-min Su, and Lun-yu QuKey Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast

Normal UniVersity, Changchun, Jilin 130024, P. R. ChinaJ. Phys. Chem. C 2009, 113, 15175–15181

指導老師 : 陳澄河 教授 研究生 : 甘宜婷

報告日期 :

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Introduction

• Recently, the multifunctionality of metal/PANI composites is particularly useful, which have attracted considerable attention due to their enhanced gas sensing properties and electrocatalytic activity, memory devices.

• Although the composites based on PANI and Ag have been reported, the preparation for the composites with nanostructure is still a novel challenge.

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Introduction

• Thus far, dramatic efforts have been dedicated to develop new methods for the fabrication of Ag/PANI composite nanostructures in different systems.

• In this paper, they developed a simple self-assembly polymerization method for the synthesis of highly uniform and monodisperse Ag/PANI composite nanotubes without using any acid molecule reagent and hard template.

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Experiment

0.117 mole AgNO30.117 mole AgNO3

0.965 mole APS+8ml DI water0.965 mole APS+8ml DI water

0.322 mole 苯胺單體

Dried under vacuum for 24 h at 50℃

Dried under vacuum for 24 h at 50℃

SEM 、 EDX 、 TEM 、 XPS 、FT-IR 、 UV-vis 、 X-ray and

Electrochemical experiments

SEM 、 EDX 、 TEM 、 XPS 、FT-IR 、 UV-vis 、 X-ray and

Electrochemical experiments

Stirred for 6 h

Immobilized for 48 h at 0-5 ℃

Precipitate was washed with DI water, ethanol, and ethyl ether

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Results and Discussion -Characterization of Ag/PANI Composite Nanotubes

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Figure 1. (A, B) SEM images and (C) TEM image of Ag/PANI composite nanotubes. (D) Corresponding EDX pattern of the Ag/PANI composite nanotubes. Synthetic conditions: [An], 0.322 mM; [APS], 0.965 mM; [AgNO3], 0.117 mM; 15 °C; 48 h.

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Figure 2. (A) SEM image and (B) corresponding EDX pattern of pure PANI. Synthetic conditions: [An], 0.322 mM; [APS], 0.965 mM; 15 °C; 48 h.

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Figure 4. UV-vis spectra of (a) pure PANI and (b) Ag/PANI composite nanotubes.

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Figure 6. XPS spectra of (A) Ag/PANI composite nanotubes, (B) Ag 3d, (C) C 1s, and (D) N 1s.

Results and Discussion -Possible Formation of Ag/PANI Composite Nanotubes

• The standard reduction potential of Ag+ + e- →Ag is E0)+0.79 V, which is lower than 1.02 V of aniline. Thus, it is hard for AgNO3 to act as an oxidant in the early stages of aniline polymerization.

• Aniline monomer is oxidized first by APS,

S2O82- + 2e- → 2SO4

2- (+2.01 V), to form reactive aniline cation-radicals, simultaneously producing H2SO4 by the reduction of APS in the early stages.

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• Two initially formed aniline cation-radicals combine into a dimer which is further oxidized by APS to form a dimer cation-radical.

• These dimer cation-radicals can act as surfactants to template the formation of nanotubes under the condition of excess oxidant.

• Then the Ag anion provided by AgNO3 acts as an electron acceptor and is reduced to Ag0 while the dimer cation-radical oxidizes to as-synthesized resulting PANI.

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• Meanwhile, the dimer cation-radical surfactant transforms from spherical micelles into tubular structured micelles for the later formation of the nanotubes.

• The growth process of the silver nanoparticles and polymerization of the dimer cation-radical surfactant continue simultaneously.

• Finally, the PANI nanotubes with dispersed Ag nanoparticles decorated on the surface are successfully prepared.

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S2O82- + 2e- → 2SO4

2- (+2.01 V)

S2O82- + 2e- → 2SO4

2- (+2.01 V)

Ag+ + e- → Ag (+0.79V)

H2SO4

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Results and Discussion - Electrochemical Behavior of PANI Composite Nanotubes

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Figure 7. CVs of the ITO electrodes modified with (A) Ag/PANI composite nanotubes and (B) pure PANI in 0.1 M N2-saturated H2SO4 with different scan rates (from inner curve to outer curve: 10, 20, 30, 40, 50, 60, 80, and 100 mV/s, respectively). Insets show the relationship of the redox current of peak I and scan rate.

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Figure 8. CVs of ITO electrodes modified with (A) Ag/PANI composite nanotubes and (B) pure PANI cross-linking as work electrodes in 0.1 M N2-saturated H2SO4 solution containing DA with various concentrations of 0.0, 0.5, 1.0, 2.0, 3.0, and 4.0 mM (a-f). Scan rate: 50 mV/s.

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Results and Discussion - Sensitivity Behavior of PANI Composite Nanotubes

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Conclusion

• They successfully prepared Ag/PANI composite nanotubes by a self-assembly polymerization process using ammonium persulfate (APS) and silver nitrate as oxidant.

• Dispersed Ag nanoparticles decorate the surface of the PANI nanotubes.

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• The Ag/PANI composite nanotubes can be applied to the chemically modified electrode, which show enhanced electrocatalytic activity for oxidation of DA compared with that of the pure PANI-modified electrode.

• This composite nanomaterial has super gas sensitivity because of its high surface area, small diameter, and porous nature of the tubular morphology and the introduction of the silver nanoparticles.

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