Pressure-induced phase transition in hydrothermally grown ZnO nanoflowers investigated by Raman and photoluminescence spectroscopy

Abstract

This paper reports the pressure-dependent photoluminescence and Raman spectral investigation of hydrothermally synthesized ZnO nanoflowers at room temperature. Intrinsic near-band-edge UV emission from ZnO nanoflowers is monotonously blue-shifted under pressures up to 13.8 GPa with a pressure coefficient of 26 meV GPa(-1), and this pressure value is nearly 5 GPa above the transition pressure from the wurtzite to the rock salt phase for bulk ZnO. The Raman band corresponds to the wurtzite phase, the [Formula: see text] and [Formula: see text] modes were observed up to about 11 GPa from the spectra. The apparent discrepancy in the transition pressures as determined from photoluminescence and Raman studies suggests that it is a consequence of the gradual phase transition, in which the smallest nanoparticles are expected to remain in the wurtzite phase up to 13-15 GPa.

Pressure-Induced Enhancement of Photoelectric Properties of ZnO Nanoparticles in the Ultraviolet Band: Implications for Electronic Device Applications

“…Also, the different pressure coefficient of Raman modes under different hydrostatic conditions have been obtained by our previous report. 35 All Raman modes show positive pressure coefficients and Gruneisen parameters except of E 2 low and 2TA, which is consistent with previous report. 36 The blue shift of the Raman peaks signifies a reduction in interatomic distances within the zinc oxide lattice under high pressure, culminating in augmented atomic interactions.…”

“…The Grüneisen parameters γ could be calculated from γ = false( B 0 / ω 0 false) false( ∂ ω / ∂ P false) where ω 0 is the Raman frequency and B 0 is the bulk modulus of ZnO at ambient conditions with the value of 143 GPa . The variance in estimating the Grüneisen parameters relative to ref originates from variations in hydrostatic conditions. In our Raman experiment, no pressure medium was used to achieve a similar nonhydrostatic condition with high pressure photocurrent measurements.…”

Reciprocating Compression of ZnO Probed by X-ray Diffraction: The Size Effect on Structural Properties under High Pressure

“…Previous studies, as summarized in Table 1, demonstrate that the initial transition pressure of bulk ZnO lies between 7.0 and 11.1 GPa, and the completion pressure lies between 11.0 and 15.5 GPa. Then, on the one side, the P i of 50 nm ZnO nanocrystalline, 22 nanotube, 18 nanobelts, 19 and nanorods 17 are all identical to that of bulk polycrystalline ZnO, whereas the P i of 12 nm ZnO, 16 nanodots, 28 nanowires, 20 and nanoflowers 29 are enhanced compared to that of bulk ZnO. On the other side, the P c of nanotube and nanorods are higher than that of bulk ZnO.…”

Electric field-assisted laser ablation fabrication and assembly of zinc oxide/carbon nanocomposites into hierarchical structures for supercapacitor electrodes

“…This band can be tentatively assigned to the E 2 high -E 2 low second order Raman mode. 56 The band at 205 cm −1 can be attributed to the 2E 2 (low) vibrational mode. 55,57 Besides, a broad band in the range of 1060-1130 cm −1 is observed, which can be the result of the overlap of several multi-phonon bands.…”