Facile and economical synthesis of large hollow ferrites and their applications in adsorption for As(V) and Cr(VI).

Unlike the previous ferrites (MFe2O4; M=Fe, Co, Zn, and Mn) solid nanospheres/nanoparticles, which were prepared by polluted solvothermal (glycol) approaches, here controllable monodisperse porous ferrites hollow nanospheres are promptly synthesized by a nontemplate hydrothermal method which has introduced an addition agent, polyacrylamide. The hollow nanospheres with different size can be prepared by varying the synthetic compositions. Scanning/transmission micros-graphs show the outside diameters of ferrite nanospheres are 180-380 nm and the shell thicknesses of that are only 20-45 nm, which could be adjusted by controlling CH3COONa concentration. X-ray diffraction (XRD) and X-ray photoelectron (XPS) spectroscopy, scanning electron (SEM) and transmission electron (TEM) microscopy, energy-dispersive spectrometer (EDS), the measurement of N2 adsorption-desorption isotherms and Brunauer-Emmett-Teller (BET) surface area, and superconducting quantum interference device (SQID) magnetometer were adopted to analyze their phase composition, morphology, porosity, and magnetic properties, respectively. The results of controlled experiments show that citrate and polyacrylamide are vital for the phase purities and morphology of ferrites. In particular, the as-obtained samples exhibit a large adsorption capacity for the toxic solution containing As(V) and Cr(VI) ions, and the calculated result of the maximum adsorption capacity is 340 mg/g based on Langmuir model, which shows excellent As(V) and Cr(VI) ions uptake capacity in contrast to other solid nanosphere materials.

Structural, optical, and magnetic studies of manganese-doped zinc oxide hierarchical microspheres by self-assembly of nanoparticles.

In this study, a series of manganese [Mn]-doped zinc oxide [ZnO] hierarchical microspheres [HMSs] are prepared by hydrothermal method only using zinc acetate and manganese acetate as precursors and ethylene glycol as solvent. X-ray diffraction indicates that all of the as-obtained samples including the highest Mn (7 mol%) in the crystal lattice of ZnO have a pure phase (hexagonal wurtzite structure). A broad Raman spectrum from as-synthesized doping samples ranges from 500 to 600 cm-1, revealing the successful doping of paramagnetic Mn2+ ions in the host ZnO. Optical absorption analysis of the samples exhibits a blueshift in the absorption band edge with increasing dopant concentration, and corresponding photoluminescence spectra show that Mn doping suppresses both near-band edge UV emission and defect-related blue emission. In particular, magnetic measurements confirm robust room-temperature ferromagnetic behavior with a high Curie temperature exceeding 400 K, signifying that the as-formed Mn-doped ZnO HMSs will have immense potential in spintronic devices and spin-based electronic technologies.