Surfactant-Assisted Hydrothermal Synthesis and Magnetic Properties of Urchin-like MnWO₄ Microspheres

Abstract

Three-dimensional (3D) urchin-like MnWO4 microspheres with a diameter of ca. 1−1.2 μm assembled by nanorods with a length of 240 nm and an aspect ratio of ca. 9 have been fabricated by a cationic surfactant cetyltrimethyl ammonium bromide (CTAB) assisted hydrothermal method. The result demonstrated that CTAB played an important role as a soft template in directing growth and self-assembly of urchin-like MnWO4 microspheres, and suitable pH values and reaction temperature are also essential for the formation of urchin-like microspheres. Magnetic measurement indicates that urchin-like MnWO4 microspheres show a weak ferromagnetic ordering at low temperature due to spin-canting and surface spins of microspheres, while much shorter MnWO4 nanorods show antiferromagnetism at low temperature.

Electronic structure and magnetic properties of FeWO4 nanocrystals synthesized by the microwave-hydrothermal method

“…Metal tungstates have attracted attention in the last decades since they are a fascinating class of materials that offer a large wide of technological applications, such as catalysts, 1 optics, 2 humidity sensors, 3 and magnetic, 1,4,5,6 properties. Iron tungstate (FeWO 4 ) is one of the most promising materials of this family and their electronic and magnetic properties have been studied to explore its potential applications.…”

“…1,13,17 In the structure of FeWO 4 with two formulas per unit cell, every metal atom is surrounded by six oxygen atoms, FeO 6 and WO 6 ; zigzag chains of oxygen octahedral FeO 6 are aligned along the c axis, see Figure 1(a). The existence of two non-equivalent positions for oxygen atoms is a characteristic of the structure of FeWO 4 .…”

Size- and Shape-Controlled Synthesis of Monodisperse Metal Oxide and Mixed Oxide Nanocrystals

“…Hence, it has attracted considerable research interest for potential applications such as photocatalysts, humidity sensors, optical fibers, photoluminescence and scintillator materials (Xing et al 2008, Qu et al 2000, Bharati, Singh and Wanklyn 1982. Several efforts have been devoted to the synthesis of MnWO 4 nanoparticles and especially focused on the shape and dimensional control (Zhou et al 2008b. We recently developed a new approach for the aqueous-phase "one-step" synthesis of uniform singlecrystalline MnWO 4 nanoparticles with controlled shape and the self-assembled mesocrystal microspheres/microapples with high yield using Mn(NO 3 ) 2 and Na 2 WO 4 as precursors and bifunctional amino acid biomolecules as capping agent.…”

“…The photoluminescence results indicated that the PL emission intensity of the MnWO 4 n a n o b a r s i s h i g h e r t h a n t h a t o f t h e M n W O 4 microspheres indicating the decrease in the luminescence efficiency of the microspheres due to nanobars inside of microspheres (Nguyen et al 2011b). MnWO 4 nanomaterials have been synthesized and revealed several morphologies such as flower-like clusters, nanowires, nanoplates, and nanorods (Zhang et al 2007b, Zhou et al 2008b, Thongtem, Wannapop and Thongtem 2009, Chen et al 2003, Zhou et al 2008a. Additionally, the kinetic control of MnWO 4 nanoparticles grown for tailored structural properties were studied by Li et al (Tong et al 2010).…”

Photocatalytic Degradation of 2-Propanol and Phenol Using Au Loaded MnWO4 Nanorod Under Visible Light Irradiation

“…Among the others, manganese tungstate (MnWO 4 ) with monoclinic huebnerite structure has attracted particular attention because MnWO 4 has a variety of applications including humidity sensor fabrication and magnetic devices [13,14], microwave applications [15], catalyst [16]. Thus far, manganese tungstates have been prepared by solid state reaction [17], complexation-precipitation [18] and solvothermal method [19].…”