In order to verify whether the hydroxyl (C-OH) groups in the PVP chains were certainly reacted with the silanol (Si-OH) groups in the VTHS domains during sol-gel reactions, X-ray photoelectron spectroscopy (XPS) was employed to measure the evolution of Si-O-CPhenyl bonds. As shown in Fig. 2a, the C1s peaks (shoulders) at ca. 286.5 eV and 288.4 eV were emerged as the PVP content increased, which can be ascribed to the aromatic C-OH because the XPS intensity at this energy range was ignorable for the pristine ASiO films without PVP. Similarly, the O1s shoulders at around 535 eV (aromatic C-O) became pronounced with the PVP content though no XPS signal was measured at this region for the pristine ASiO films. These results confirm the presence of PVP in the hybrid films. Finally, the Si2p peaks revealed the formation of Si-O-CPhenyl bonds because the shoulders between 105 eV and 106 eV were gradually increased with the PVP content compared to no signal for the pristine PVP films (note that the Si-O-CEthyl bonds were almost completely removed during hydrolysis reaction). The evolution of Si-O-Si and Si-O-CPhenyl bonds was measured at the wavenumber range of 900~1200 cm−1 from the Fourier Transform-Infrared (FT-IR) spectra (Fig. 2d)43, which also delivered the gradual increase in the aromatic C-C and C = C peaks with respect to the PVP content44.