The W-O stretching modes are less intense, and changes in the low-frequency modes may indicate some modifications in the tungsten-oxide framework. This is possibly

owing to the fact that the surface of exfoliated Q2D WO3 itself contains various defects. In general, the majority of experimental phenomena discussed above were associated to adsorption on expected sites of oxide nanoflake surface (co-ordinatively unsaturated cations, hydroxyls and their pair). However, the MLN2238 purchase appearance of the most active surface centres suggests a connection with defects in nanoflakes [38, 40]. The other factors influencing properties of the ‘real’ oxide surfaces are (i) the presence of different lattice defects in the surface layer of nanoflake and (ii) their

chemical composition, which in many cases, may differ from that in the microstructured material. There was also one stretch observed at 1,265 cm-1 (Si), which directly relates to the substrate platform. The WO3 FTIR spectra also indicated that there were no impurities present in the prepared and exfoliated samples. Raman spectroscopy was employed to determine the vibration and rotation information BI 6727 ic50 in relation to chemical bonds and symmetry of molecules in sol-gel-developed WO3, sintered at 550° and 650°C, respectively, and exfoliated ultra-thin Q2D WO3. Raman spectra for sol-gel-developed WO3 and exfoliated Q2D WO3 nanoflakes in the perturbation area of the spectrum are shown in Figure 7. In both cases, Raman peaks corresponding to WO3 were observed. The bending modes of WO3 are usually located between 600 and 900 cm-1, while the stretching modes can be observed between 200 and 500 cm-1 [41]. The prominent band situated at 802 cm-1

has been assigned to the symmetric stretching mode of terminal (W6+ = O) groups which may also be vibrationally coupled [42]. This peak represents lattice discontinuities which lead to short-range (lattice) order. The presence of O-W-O bond is typically associated with β-WO3 [43]. There were no other substantial peaks noted, suggesting that no impurities were present in the samples. Bridging (O-W-O) vibrations, which occur around 700 cm-1, are influenced significantly by hydration [30], and as a result, the recorded 712 cm-1 band can be used as a spectral marker for hydration level Lepirudin of WO3 [44]. However, care should be exercised using this approach, since the crystalline hexagonal phase (h-WO3) also exhibits bands at these frequencies but is likely to be NVP-BGJ398 concentration absent in sample prepared without a thermal annealing step. Figure 7 Raman spectra (perturbation region within 600 to 1,000 cm -1 ) for sol-gel-developed WO 3 and exfoliated Q2D WO 3 nanoflakes. Sintered at 550°C (A) and 650°C (B), respectively. It is noteworthy that the intensity of the peaks for the exfoliated Q2D WO3 nanoflakes sintered at 550°C was about two times higher than that the strength of peaks for the same sol-gel-developed WO3.