Flower-like Bi Research Articles

The effects of citrate ion on morphology and photocatalytic activity of flower-like Bi2O2CO3

Abstract Flower-like Bi 2 O 2 CO 3 was synthesized in an aqueous solution containing bismuth nitrate, citric acid and urea. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, N 2 adsorption–desorption and UV-visible diffuse reflectance spectroscopy. The photocatalytic activity was evaluated by the photocatalytic degradation of methyl orange in an aqueous solution under Xe lamp irradiation. The effects of citrate ion on the morphology and photocatalytic activity were investigated. The results show that citrate ions facilitate the formation of hierarchical flower-like Bi 2 O 2 CO 3 microsphere. The amount of citric acid is an important parameter to control the morphology and size of Bi 2 O 2 CO 3 microsphere. The flower-like Bi 2 O 2 CO 3 exhibited an enhanced photocatalytic activity than Bi 2 O 2 CO 3 blocks. The highest photocatalytic performance can be achieved for the Bi 2 O 2 CO 3 microspheres synthesized in the solution with the C 6 H 8 O 7 /Bi(NO 3 ) 3 M ratio of 2:1 due to the synergic effects of several factors, including its better crystallinity, larger surface area, stronger UV-visible absorption and unique hierarchical microsphere structure.

Microwave hydrothermal synthesis and optical properties of flower-like Bi2MoO6 crystallites

Abstract Flower-like Bi 2 MoO 6 crystallites were successfully synthesized by the microwave hydrothermal process using Bi(NO 3 ) 3 ·5H 2 O and Na 2 MoO 4 ·2H 2 O as source materials and adding hexamethylene tetramine (HMT) as a template. X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) were used to characterize the products. Ultraviolet–visible (UV–vis) spectroscopy was employed to study the optical properties of Bi 2 MoO 6 . Results show that the product morphology is flower-like on adding the template. These flower-like Bi 2 MoO 6 crystallites are a self-assembly of many thin nanoplates. HMT plays an important role in the formation of the flower-like morphology. UV–vis absorption spectra of all the Bi 2 MoO 6 samples show strong photoabsorption properties from the ultraviolet region to the visible-light region with wavelength shorter than 500 nm. The band gap of flower-like Bi 2 MoO 6 crystallites displays a slight red-shift compared with the Bi 2 MoO 6 plate-like structures.

The facile synthesis of PbS cubes and Bi 2S 3 nanoflowers from molecular precursors at room temperature

PbS and Bi 2S 3 nanocrystals with well-controlled sizes and shapes were easily produced from molecular precursors (xanthate) in ethylene diamine (en) solution at room temperature. When lead or bismuth ethylxanthate were added into en solution, the precipitates were instantly formed, and subsequently, PbS cubes and flower-like Bi 2S 3 hierarchical structures were obtained if the mixtures were left still for 5 days under ambient conditions. This work not only provides a facile route to synthesize chalcogenides with well-defined nano- and microstructures in a solution-phase system, but also gives insight into understanding on decomposition behavior of molecular precursors in various solvents.

Microwave-assisted solution-phase preparation of flower-like Bi2WO6and its visible-light-driven photocatalytic properties

We report here the preparation of flower-like Bi2WO6via a simple, rapid, microwave-assisted solution-phase process. Powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HRTEM) were employed to characterize the phase and morphologies of the products. The time-dependent experiments showed an Ostwald ripening mechanism in the crystal growth process. The as-prepared Bi2WO6 was able to efficiently degrade Rhodamine B (RhB) under visible light irradiation. Calcination was found to decrease the photocatalytic performance of flower-like Bi2WO6.

Facile solvothermal synthesis of hierarchical flower-like Bi2MoO6hollow spheres as high performance visible-light driven photocatalysts

A facile template-free method has been developed for the controllable fabrication of novel hierarchical flower-like Bi2MoO6 hollow spheres via a solvothermal process in the presence of ethylene glycol. The formation mechanism was proposed based on the evolution of morphology as a function of solvothermal time, which involves the initial formation of nanoparticles followed by their self-aggregation to microspheres and transformation into hierarchical flower-like hollow spheres by Ostwald ripening. The integer appearance of the hierarchical flower-like Bi2MoO6 hollow spheres was maintained after calcination at 400 °C for 3 h. Furthermore, the calcined hierarchical flower-like Bi2MoO6 hollow spheres exhibited excellent visible-light-driven photocatalytic efficiency for the degradation of Rhodamine B, up to 95% within 2 h, which was much higher than that of Bi2MoO6 prepared by solid-state reaction and TiO2 (P25). The improved photocatalytic performance could be ascribed to the special hierarchical hollow sphere structure, good permeability and large surface area.

Facile hydrothermal synthesis of 3D hierarchical Bi2SiO5 nanoflowers and their luminescent properties

Facile hydrothermal synthesis of novel hierarchical flowerlike Bi 2 SiO 5 nanostructures consisting of single-crystal nanosheets is reported using polyvinylpyrrolidone (PVP, K30) as capping reagent in the presence of NaOH. The obtained products are systematically characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. Control experiments are carried out to investigate various factors that affect the morphology and size of the products. The results indicate that the nucleation and growth of the flowerlike nanostructures are dominated by a nucleation–dissolution–recrystallization growth mechanism. It is demonstrated that the concentrations of PVP and NaOH play important roles in the formation of the hierarchical nanoflowers. Moreover, the room-temperature photoluminescence properties of the Bi 2 SiO 5 nanoflowers are also investigated.

Synthetic Bi 2O 2CO 3 nanostructures: Novel photocatalyst with controlled special surface exposed

In this work a novel Bi 2O 2CO 3 photocatalyst was first put forward by virtue of structural understanding. In particular, the flower-like Bi 2O 2CO 3 hierarchitecture with the controlled special {0 0 1} plane exposed was first synthesized via a mild route, showing the excellent photocatalytic activity due to the large distortion of Bi–O on the exposed surface. The Bi 2O 2CO 3 nanostructures have proved to be not only a new photocatalyst under solar light irradiation, but also a possible example for investigating the key factors of which may impact on the photocatalytic ability. The results confirmed that the higher efficiency of the photocatalytic activity should be contributed synergistically by the higher BET surface area and the special exposed surface.

Microwave-assisted synthesis and characterization of 3D flower-like Bi 2S 3 superstructures

Bismuth sulfide (Bi 2S 3) microcrystallines with three-dimensional (3D) flower-like superstructures were prepared by the microwave irradiation method with bismuth nitrate (Bi(NO 3) 3·5H 2O) and thiourea ((NH 2) 2CS) as raw materials and ethylene glycol as solvent. The powder X-ray diffraction (XRD) pattern shows the product belongs to the orthorhombic Bi 2S 3 phase. The quantification of X-ray photoelectron spectra (XPS) analysis peaks gives an atomic ratio of 1.9:3.0 for Bi:S. Transmission electron microscopic (TEM) and scanning electron microscopy (SEM) studies reveal that the superstructure of the as-prepared Bi 2S 3 consists of sticks extending radially from a nucleation site. The reaction progress and a possible mechanism were proposed.