A comparison indicates that the composites exhibit a higher intensity ratio of Q to B ring modes than pure PANI, suggesting that there are more quinoid units in the composites than pure PANI. This result can be attributed to the adding of HAuCl4 and H2PtCl6, which can serve not only as the resource of metal particles, but also as strong oxidants, which can enhance the oxidation degree
of the PANI in composites [22, 23]. Figure 3 represents the UV-vis absorption spectra of PANI, PANI(HAuCl4·4H2O), and PANI(H2PtCl6·6H2O) in m-cresol solution. The characteristic peaks of PANI and composites at approximately 320 to 330 nm, approximately 430 to 445 nm, and 820 to 870 nm are attributed to π-π*, selleck polaron-π*, and π-polaron transitions, respectively . Feng et al. reported that pure Au nanoparticles usually show Barasertib chemical structure an absorption peak at approximately 510 nm as a result of the surface plasmon resonance , whereas Pt nanoparticles usually have no absorption peak at 300 to 1,000 nm [25, 26]. However, in this case, the surface plasmon resonance
bands of Au nanoparticles are not observed, which may be caused by the changing of their surrounding environment . However, the absorption peaks of π-polaron change significantly, and the intensity ratio (A820–870/A320–330) of the composites is higher than PANI, indicating that the doping level of the PANI in composites is higher than that of pure PANI . Therefore, the results from the UV-vis absorption spectra imply that the HAuCl4 or H2PtCl6 have certain effects on the polymer chains. Figure 3 UV-vis spectra. Morin Hydrate Curves (a) PANI, (b) PANI(HAuCl4·4H2O), and (c) PANI(H2PtCl6·6H2O). Figure 4 is the EDS of the composites. It can be concluded from Figure 4 that the Au and Pt elements do exist in the polymer matrix, and the weight percentages are 7.65 and 6.07 for Au and Pt elements, respectively. Figure 5
shows the XRD patterns of PANI, PANI(HAuCl4·4H2O), and PANI(H2PtCl6·6H2O). As indicated in Figure 5, the PANI exhibits two peaks at 2θ approximately 20° and approximately 26°, which are ascribed to the periodicity parallel and MM-102 perpendicular to the polymer chains, respectively . In the case of PANI(HAuCl4·4H2O), the strong peaks appeared at 2θ values of 38°, 44°, and 64.5° which can be assigned to Bragg’s reflections from the (111), (200), and (220) planes of metal Au . These Bragg’s reflections are in good agreement with the data (JCPDS-ICCD, 870720), which can further prove the existence of Au nanoparticles in the PANI(HAuCl4·4H2O). However, there is no characteristic Bragg’s reflection for metal Pt in the case of PANI(H2PtCl6·6H2O), which is a similar phenomenon to that of Pt nanoparticles deposited on carbon nanotubes using PANI as dispersant and stabilizer .