Among peaks assigned to PANI, the characteristic peaks around 1,580 and 1,497 cm−1 relate to the stretching vibration of click here quinoid (−N=(C6H4)=N-) ring and benzenoid (−(C6H4)-) ring, respectively. Another main band at 1,303 cm−1 can be assigned to the stretching of C-N in -NH-(C6H4)-NH-. The bands BIBW2992 cost appeared at 1,143 cm−1 and 829 cm−1 which correspond to the stretching of C-H in-plane and C-H out-of-plane bendings. In addition, the bands of N-H (PANI) and O-H (H2O) at 3,230 and 3,400 cm−1, respectively, are observed. As noticed, the band near 3,400 cm−1

(O-H) is becoming intense with the decrease of the acid concentration, which is attributed to the appearance of hydrate MnO2. The above conclusion is proved by the annealing experiments: the band at 3,400 cm−1 (O-H) of hydrate MnO2 vanished after 500°C heat treatment (Additional file 1: Figure S1). The band BMS202 supplier near 1,303 cm−1 is becoming weaker from curves g to a in Figure 4, which suggests that the doping degree of PANI is changing with the acid concentration. The characteristic bands of curves a, b, and c in Figure 4 shifted right compared with the others, which is ascribed to the effect of MnO2 on PANI. It demonstrates that some special interaction exists between MnO2 and PANI. Figure 4 FTIR spectra of the as-prepared samples. Curves a to g: MnO2/PANI fabricated in 0, 0.02, 0.05, 0.1, 0.2, 0.5, and 1 M HClO4, respectively.

Due to the ordered and metallic-like property, conducting polymers possess particular crystallinity and orientation. As shown in the XRD patterns in Figure 5A, there are no identified peaks appeared for the products synthesized in low-acid concentrations (curves a to e: 0.1 M NaOH, and 0, 0.02, 0.05, and 0.1 M HClO4, respectively), which indicates the products are amorphous. For the products obtained at 0.2 (curve f), 0.5 (curve g), and 1 M HClO4 (curve h), two intense XRD peaks 2θ≈20 and 25° are observed corresponding

to pure PANI according to previous literature [2]. All above results confirm that the crystallized PANI can be formed at higher acid concentrations in this work. Figure 5 XRD patterns of the samples. (A) The XRD patterns of the composites, curves a to h: MnO2/PANI fabricated in 0.1 M NaOH and 0, 0.02, 0.05, 0.1, 0.2, 0.5, and 1 M HClO4, respectively. (B) Resminostat XRD pattern of the samples, curves a to d: annealed MnO2/PANI fabricated in 0, 0.02, 0.05, and 0.1 M HClO4, respectively. To further analyze the components at different acid concentrations, the samples were treated at 500°C (at which MnOx is crystallizing and PANI will be burned). The products obtained at 1, 0.5, and 0.2 M HClO4 were burned out with no solids left, which indicates that there is no MnO2 generating at such acid concentrations. The FTIR spectra of the heat-treated composites fabricated in 0.1, 0.05, 0.