Inserts: appropriate AFM images of sol-gel-developed and exfoliated WO3 nanoflakes, respectively. All impedance measurements were performed on Q2D WO3 nanoflakes sintered at 550 and 650°C, respectively. AC impedance measurements were done from 106 to 0.1 Hz with an alternative current of 10 mV and results are presented in Figure 5. We found that there are no significant difference between the impedance recorded for Q2D WO3 annealed at 550°C (1.6 ohm) and impedance recorded for Q2D WO3 annealed at 650°C

(1.8 ohm). Due to very small dimensions, the contribution from the Q2D WO3 working electrode into the total impedance confirmed to be very small. The resistance primarily comes from wiring (e.g. cables, alligator clips) and electrolyte, where BAY 80-6946 mouse the resistance of Q2D WO3 nanoflakes is negligible. Figure 5 BAY 73-4506 cost Nyquist plots of Q2D WO 3 nanoflakes annealed at 550°C and 650°C, respectively. In situ FTIR spectroscopy of Q2D WO3 nanoflakes was utilized to determine surface chemistry and surface reactions of the developed crystalline nanostructures [36]. This is a very powerful technique particularly for elucidating changes in hydration and hydroxylation that occur on the surface of Q2D nanoflakes.

The FTIR spectra for Q2D WO3 nanoflakes sintered at 550 and 650°C, respectively, are presented in Figure 6. They illustrate the bonding characteristics of the functional groups in the sol-gel prepared and exfoliated Q2D WO3. The higher surface area enables the detection of bands owing to surface OH and adsorbed water in the 3,700 to 3,100 cm-1 region (not shown in presented Figure 6). Specifically, the sharp peaks at 1,620 cm-1 are various O-H stretching modes due to H2O bending mode. Fluorouracil mouse Generally, about 40% of the total adsorbed water remains strongly bound to the surface up to 150°C [37]. Weak C-H stretching modes at 2,991 cm-1 were also observed. Figure 6 FTIR measurements for WO 3 nanoflakes sintered at 550°C and 650°C. (A) Total IR spectra. (B) Perturbation region

within 400 to 1,200 cm-1. Considering that WO3 contains cations in the highest degree of oxidation (+6), CO molecules do not adsorb on its surface because of full coordination. The frequency values obtained in spectra of CO adsorbed on Q2D WO3 nanoflakes shifted to the lower values compared to the assignments represented for microstructured WO3 [38]. This is connected with the fact that in the analysed Q2D WO3 nanoflakes, the degree of oxidation on some parts of the WO3 surface has been changed and few WO3-x sites appeared on the surface of nanoflakes causing CO adsorption. It should be noted that some residual hydrated WO3 is most likely present in the sample because hydrated WO3 is formed in the sol-gel process and then converted to β-WO3 during sintering [37, 39].