V2O5 has a layered structure interconnected with van der Waals force through V—terminal oxygen (OI)—V bond, which opens the door for finding applications as a new 2D oxide material. 2D V2O5, with V being a transition metal, is expected to show exotic physicochemical and electronic properties. Moreover, it can be employed as cathode material in Li-ion batteries, chemical sensors, and catalysts. There are only a few reports for the formation of a few-layer V2O5 structure. However, none of these studies could provide a comprehensive knowledge of Raman spectroscopic properties of the 2D structure, which should differ distinctly from the bulk. In the present study, we make a conscious effort to synthesize monolayer V2O5 using a modified chemical exfoliation technique with different concentrations of V2O5 in formamide. Thicknesses of the exfoliated layers are measured to be in the range of 1.0 -1.5 nm using atomic force microscopy. Structural and vibrational properties are studied using synchrotron x-ray diffraction and Raman spectroscopy respectively. 10 out of the 21 zone center Raman modes are observed for the bulk at 105 (Ag), 146 (B1g), 198 (B2g), 285 (B3g), 305 (B2g), 406 (Ag), 482 (Ag), 529 (Ag), 703 (B1g) and 994 (Ag) cm-1. The 2D layers showed broadening along with frequency shift in the phonon modes as compared to the bulk values. Hence, a thickness-dependent vibrational decoupling has been observed, particularly for out of plane Raman modes. Further, it has been verified by computing lattice vibrational modes using density functional perturbation theory. However, the low-frequency modes showed a blue shift in contrast to the calculated redshift. This anomaly is attributed to the surface reconstructions that appear during the process of exfoliation. To the best of our knowledge, this is the first attempt to understand the Raman spectroscopic properties of 2D V2O5 in detail.

Raman spectroscopic studies of chemically exfoliated 2D V2O5

ACS Spring Meeting 2021

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