指導老師 : 陳澄河 教授 研究生 :甘宜婷 報告日期 : 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 Qu Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal UniVersity, Changchun, Jilin 130024, P. R. China J. 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 : 南台化材 2017/4/24

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. 南台化材 2017/4/24

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. 南台化材 2017/4/24

FT-IR 、 UV-vis 、X-ray and Electrochemical experiments 0.965 mole APS+8ml DI water 0.117 mole AgNO3 Immobilized for 48 h at 0-5 ℃ 0.322 mole苯胺單體 Stirred for 6 h Precipitate was washed with DI water, ethanol, and ethyl ether SEM、EDX、TEM、XPS、 FT-IR 、 UV-vis 、X-ray and Electrochemical experiments Dried under vacuum for 24 h at 50℃ 南台化材 2017/4/24

Results and Discussion -Characterization of Ag/PANI Composite Nanotubes 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. 南台化材 2017/4/24

Synthetic conditions: [An], 0.322 mM; [APS], 0.965 mM; 15 °C; 48 h. 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. 南台化材 2017/4/24

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Figure 4. UV-vis spectra of (a) pure PANI and (b) Ag/PANI composite nanotubes. 南台化材 2017/4/24

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Figure 6. XPS spectra of (A) Ag/PANI composite nanotubes, (B) Ag 3d, (C) C 1s, and (D) N 1s. 南台化材 2017/4/24

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- → 2SO42- (+2.01 V), to form reactive aniline cation-radicals, simultaneously producing H2SO4 by the reduction of APS in the early stages. 南台化材 2017/4/24

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. 南台化材 2017/4/24

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. 南台化材 2017/4/24

S2O82- + 2e- → 2SO42- (+2.01 V) H2SO4 S2O82- + 2e- → 2SO42- (+2.01 V) Ag+ + e- → Ag (+0.79V) 南台化材 2017/4/24

Results and Discussion - Electrochemical Behavior of PANI Composite Nanotubes 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. 南台化材 2017/4/24

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. 南台化材 2017/4/24

Results and Discussion - Sensitivity Behavior of PANI Composite Nanotubes 南台化材 2017/4/24

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. 南台化材 2017/4/24

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. 南台化材 2017/4/24