From VO2 (B) to VO2 (A) nanobelts: first hydrothermal transformation, spectroscopic study and first principles calculation

Abstract

The phase transition process from VO(2) (B) to VO(2) (A) was first observed through a mild hydrothermal approach, using hybrid density functional theory (DFT) calculations and crystallographic VO(2) topology analysis. All theoretical analyses reveal that VO(2) (A) is a thermodynamically stable phase and has a lower formation energy compared with the metastable VO(2) (B). For the first time, X-ray absorption spectroscopy (XAS) of the V L-edge and O K-edge was performed on different VO(2) phases, and the differences in the electronic structure of the two polymorphic forms provide further experimental evidence of the more stable VO(2) (A). Consequently, transformation from VO(2) (B) to VO(2) (A) is much easier to be realized from a dynamical point of view. Notably, the transformation of VO(2) (B) into VO(2) (A) show the sequence VO(2) (B)-high-temperature VO(2) (A(H)) phase-low-temperature VO(2) (A) phase, which was achieved by hydrothermal treatment, respectively. Also, an alternative synthesis route was proposed based on the above hydrothermal transformation, and VO(2) (A) was successfully prepared via the simple one-step hydrothermal method by hydrolysis of VO(acac)(2) (acac = acetylacetonate). Therefore, VO(2) nanostructures with controlled phase compositions can be obtained in high yields. Through elucidating the structural evolution in the crystallographic shear mechanism, we can easily guide the design of other metal oxide nanostructures with controllable phases.

Pressure-induced metallization and amorphization inVO2(A)nanorods

“…By extrapolating the linear portion of the curve to the abscissa we obtained the band gap (E g ). At ambient condition E g is 0.21 eV, which is the same as the theoretical value [38]. As shown in Fig.…”

“…VO 2 (A) can be regarded as a Mott insulator according to previous theoretical study [38]. At generate potential nucleation centers for the phase transition and finally, transform a stable structure into an amorphous one.…”

VO2(B) conversion to VO2(A) and VO2(M) and their oxidation resistance and optical switching properties

“…[5,6,[29][30][31][32]. Recently, an increasing attention has been paid to tetragonal VO 2 (A) (space group P42/ncm) [26,33,34], because it shows a metal-semiconductor transition with the phase transition temperature (T c ) at 162°C, accompanied by a crystallographic transition between a low temperature phase (LTP, P4/ncc, 130°C below 162°C) and a high temperature phase (HTP, I4/m, 87°C above 162°C). In the past decades, the synthesis, characterization and properties of VO 2 (B), VO 2 (M) and VO 2 (A) have been extensively studied, however, the oxidation resistance properties of VO 2 (B), VO 2 (A) and VO 2 (M) in air atmosphere have rarely been reported.…”

Synthesis and formation mechanism of VO2(A) nanoplates with intrinsic peroxidase-like activity

“…24 Xie et al reported the large-scale fabrication of VO 2 (A) nanobelts by simple hydrolysis of VO(acac) 2 and observed an intermediate phase VO 2 (B). 25 In addition, Dai et al prepared 1D VO 2 (A) nanostructures via a one-step hydrothermal method using VOSO 4 and NH 3 $H 2 O as precursors; the prepared material was used as a high performance cathode in LIBs. 26 Much effort has been put into developing synthetic strategies for the fabrication of VO 2 nanostructures, using methods such as sol-gel, templating, ion implantation, precursor pyrolysis, hydrothermal and solvothermal syntheses, magnetron sputtering and gas-phase deposition.…”