School of Engineering Physics, Hanoi University of Science and Technology, Hanoi 10000, Vietnam.
Sensors (Basel). 2012;12(6):7965-74. doi: 10.3390/s120607965. Epub 2012 Jun 8.
Polypyrrole/single wall carbon nanotube composites were synthesized by in-situ chemical polymerization using pyrrole (PPy) as precursor and single wall carbon nanotubes (SWNTs) as additive component. Electron microscope images reveal that SWNTs component acts as nucleation sites for PPy growth in the form of spherical and cylindrical core-shell structures. The SWNTs/PPy core-shell results in thin n-p junctions which modify the PPy bandgap and reduce the work function of electrons. As a result of the strong coupling, Raman and IR spectra show that the PPy undergoes a transition from polaron to bipolaron state, i.e., indicating an increase in the conductivity. In the UV-Vis spectra, the 340 nm adsorption band (π*-π transition) exhibits a red shift, while the 460 nm adsorption band (bipolaron transition) experiences a blue shift indicating a change in electronic structure and a relocation of polaron levels in the band gap of PPy. The modification in PPy electronic structure brings in a synergistic effect in sensing feature. Upon exposure to oxygen (an oxidizing agent) and NH(3) gas (a reducing agent), the PPy/SWNTs nanocomposite shows an enhancement in sensitivity exceeding ten folds in comparison with those of PPy or SWNTs.
聚吡咯/单壁碳纳米管复合材料是通过原位化学聚合方法合成的，以吡咯（PPy）为前驱体，单壁碳纳米管（SWNTs）为添加成分。电子显微镜图像显示，SWNTs 成分作为 PPy 生长的成核点，呈现出球形和圆柱形的核壳结构。SWNTs/PPy 核壳结构导致薄的 n-p 结，这改变了 PPy 的能带隙并降低了电子的功函数。由于强耦合作用，拉曼和红外光谱表明 PPy 从极化子状态转变为双极化子状态，即导电性增加。在紫外-可见光谱中，340nm 吸收带（π*-π 跃迁）发生红移，而 460nm 吸收带（双极化子跃迁）发生蓝移，表明电子结构发生变化，极化子能级在 PPy 的能带隙中重新定位。PPy 电子结构的修饰带来了传感特性的协同效应。在暴露于氧气（氧化剂）和 NH3 气体（还原剂）时，PPy/SWNTs 纳米复合材料的灵敏度增强了十倍以上，与 PPy 或 SWNTs 相比。
