Three-Dimensional Self-Assembled Hierarchical Architectures of Gamma-Phase Flowerlike Bismuth Oxide

Abstract

Three-dimensional (3D) self-assembled hierarchical bismuth oxide architectures were prepared via a solution precipitation synthesis at 85 degrees C in 45 min with the aid of polyethylene glycol-8000 (PEG-8000) as a capping agent. The morphology and crystalline phase evolution was studied versus reaction time and capping agent concentration and interpreted in terms of growth mechanisms. At higher capping agent concentrations, the as-grown 3D hierarchical flowerlike bismuth oxide was crystalline cubic gamma-phase that was previously formed only at temperature > or =640 degrees C. The morphology and crystal structure of these 3D cubic gamma-phase bismuth oxide flowers were not changed with calcining up to 600 degrees C. Photoluminescence was attributed to emission from the Bi(3+) ion by a (3)P(0),(1) --> (1)S(0) transition and from defects. The gamma-phase flowerlike bismuth oxide shows better ion conductivity than that of rodlike bismuth oxide formed without the capping agent. The flowerlike morphology was attributed to modification of the nucleation and growth kinetics by the capping agent.

Studying Impact of Different Precipitating Agents on Crystal Structure, Morphology and Photocatalytic Activity of Bismuth Oxide

“…The change in color indicated the formation of Bi2O3. As bismuth oxynitrate was used as a bismuth precursor as compared to previous reports that used bismuth nitrate [14][15][16][17][18][19], the reaction chemistry (with NH4OH) is presented as follows:…”

“…The calcination temperature used during the synthesis of Bi2O3 in the current study and by Iyyapushpam et al [14] is higher than that used by Iyyapushpam et al [15] which could be the reason for the formation of α-Bi2O3. It is known that α-Bi2O3 is a stable phase of bismuth oxide and other phases of Bi2O3 transform to the α-Bi2O3 phase under high temperature [19,23]. This indicates that both the resultant pH and the calcination temperature determine the phase of Bi2O3.…”

“…The deposition method determines whether the catalyst is uniformly distributed on the support or accumulation of the oxide takes place on the areas of the support [10,11,12]. Therefore, various methods have been reported for synthesis Bi2O3 that include hydrothermal [13], direct precipitation [14][15][16][17][18][19], microwave [6,20], solution combustion [21,22], and sol gel [1]. Of all these methods, described for the synthesis of Bi2O3 particles, the precipitation method is one of the least complex and energy efficient.…”

“…NH4OH and NaOH) have an effect structural and photocatalytic properties of Bi2O3. Additionally we used bismuth oxy nitrate as a source of bismuth as compared to the commonly used bismuth nitrate [14][15][16][17][18][19]. The results suggested that the Bi2O3 synthesized using NH4OH formed α-Bi2O3, whereas the one synthesized using NaOH formed a mixture of α-Bi2O3 and γ-Bi2O3.…”

Poly(vinyl pyrrolidone)-assisted hydrothermal synthesis and enhanced visible-light photocatalytic performance of oxygen-rich bismuth oxychlorides

“…One peak at $524 nm in BP0 is attributed to the charge-transfer transitions between the VB and CB of Bi 12 O 17 Cl 2 . Another strong peak at $488 nm is related to the surface-defect emission, which is determined by the surface states such as oxygen vacancies originated from the fast growth rate [32]. However, other BPx samples show merely one broad peak centered at nearly 520 nm with relatively low PL intensity in comparison with sample BP0.…”