Morphological evolution and visible light-induced degradation of Rhodamine 6G by nanocrystalline bismuth tungstate prepared using a template-based approach

Abstract

The cleaning of water contaminated with organic dyes is a crucial problem nowadays. The search for good catalysts is intense, and bismuth tungstates have attracted a lot of attention because of their catalytic properties which are related to their crystal structure and morphology. In this study, we show that Bi 2 WO 6 (BWO) crystals synthesized by the surfactant-assisted hydrothermal method create a different morphology than non-assisted crystals. With the assistance of the PVP surfactant, even the BWO crystalline structure could change, crystallizing into a high-symmetry metastable phase. These changes in morphology imply a decrease in BWO catalytic activity, which shows that insightful control of BWO synthesis is necessary to improve the BWO properties. & 2016 Elsevier Ltd. All rights reserved. [5,9] and other titanium doped oxides [15-18] being some of the most investigated. Bismuth oxides and derivatives show enormous potential in remediating environments contaminated by organic or inorganic pollutants [19-21]. In particular, tungstates, which constitute another class of metal oxides, are very promising for such applications [22-24]. In particular, bismuth tungstates have attracted attention in the research of nanostructured materials because of their applications as catalysts [25-29]. Bi 2 WO 6 (BWO) has an orthorhombic structure with P2 1 ab space group and belongs to the Aurivillius family of compounds. These compounds have a general formula of (Bi 2 O 2) 2 þ (A n À 1 B n O 3n À 1), where A represents a mono-, bi-, or trivalent ion; B denotes a tetra-, penta-, or hexavalent ion; and n is the BO 6 octahedra number in each pseudo-perovskite block [30]. Many papers have described structural change as a key factor in the enhancement of catalytic properties [19,20]. Therefore, various synthesis methods have been used to obtain new structured materials to enhance the BWO properties [31-33]. The template method, using templates such as ethylene glycol (EG) [34], cetyltrimethylammonium bromide (CTAB) [35], and glycine (gly) [36], has been widely used to promote structural changes in BWO. The compounds obtained in the presence of Contents lists available at ScienceDirect

Enhancement of symmetry-induced photoluminescence in bismuth tungstate microcrystals

“…2(d)). As discussed previously [6], the presence of PVP during synthesis induces a B2cb metastable structure, which can be transformed into the usual P2 1 ab structure by annealing (Fig. 2c).…”

“…X-ray powder diffraction (XRPD) patterns were obtained using a D/Max-2500PC diffractometer (Rigaku, Japan) with Cu-Kα radiation (1.5406 Å) at 40 kV and 150 mA, between a 2θ angle range of 5-85°; these patterns were used to confirm the structures against those previously obtained [6]. Fourier transform Raman (FT-Raman) spectra were recorded using a Bruker-RFS 100 (Germany) spectrometer.…”

“…Bi 2 WO 6 samples were obtained by a previously reported surfactant-assisted hydrothermal method [6]. Typically, 1.0 mmol (0.3332 g) of sodium tungstate dihydrate (Na 2 WO 4 Á 2H 2 O, 99% purity, Aldrich) and 2.0 mmol (0.9898 g) of bismuth nitrate (Bi (NO 3 ) 3 , 99% purity, Aldrich) were added to 100 mL of surfactant solution (SDS, PVP).…”

“…Metal tungstates have been the subject of much attention because of their large range of chemical and physical properties [1,2]. Bi 2 WO 6 (BWO), in particular, has been widely investigated because of its interesting ferroelectric [3] and piezoelectric [4] properties, as well as its catalytic potential [5,6], optical properties [7], and magnetic characteristics [8]. It is crucial to investigate the photoluminescence (PL) properties of bismuth tungstates because these materials are promising candidates for application as optical scintillators [7,9].…”

Wastewater depollution of textile dyes and antibiotics using unmodified and copper oxide/zinc oxide nanofunctionalised graphene oxide materials

“…4–6 These aromatic dye molecules cannot be easily eliminated from wastewater systems, and can thus be detected in surface water affecting the surrounding aquatic biota. 7,8 These dye molecules also give a colour to the water body, decreasing light penetration, and thus reducing the rate of photosynthesis. 4,9 As a result, the levels of dissolved oxygen will decrease leading to the death of aquatic organisms due to formation of an anoxic environment.…”