Morphological and Phase Controlled Tungsten Based Nanoparticles: Synthesis and Characterization of Scheelites Wolframites and Oxides Nanomaterials

摘要

For the first time tungsten based nanoparticles (WNPs) of scheelite (MWO4; M = Ca, Sr, Ba, Pb), wolframite (MWO4; M = Mn, Fe, Zn & (Mg0.60Mn0.17Fe0.26)WO4), and the oxide (WO3 and W18O49) were synthesized from solution precipitation (i.e.,trioctylamine or oleic acid) and solvothermal (i.e., benzyl alcohol) routes. The resultant WNPs were prepared directly from tungsten (VI) ethoxide (W(OCH2CH3)6, >1) and stoichiometeric mixtures of the following precursors: [Ca(N(SiMe3)2)2]2 (>2), Pb(N(SiMe₃)₂)₂ (>3), Mn[(μ-Mes)₂Mn(Mes)]₂ (>4), [Fe(μ-Mes)(Mes)]₂ (>5), Fe(CO)₅ (>6), H⁺[Ba₂(μ₃-ONep)(μ-ONep)₂(ONep)(ONep)₃(py)]⁻₂ (>7), H⁺[Sr₅(μ₄-O)(μ₃-ONep)₄(μ-ONep)₄(ONep)(py)₄]⁻ (>8), and [Zn(Et)(ONep)(py)]₂ (>9) where Mes = C₆H₂(CH₃)₃-2,4,6, ONep = OCH₂CMe₃, Et = CH₂CH₃, and py = pyridine. Through these routes, the WNP morphologies were found to be manipulated by the processing conditions, while precursor selection influenced the final phase observed. For the solution precipitation route, >1 yielded (5 × 100 nm) W₁₈O₄₉ rods while stochiometeric reactions between >1 and (>2 – >9) generated homogenous sub 30 nm nano-dots, -diamonds, -rods, and -wires for the MWO₄ systems. For the solvothermal route, >1 was found to produce wires of WO₃ with aspect ratios of 20 while (>1 & >2) formed 10 – 60 nm CaWO₄ nanodots. Room temperature photoluminescent (PL) emission properties of select WNPs were also examined with fluorescence spectroscopy (λ_ex = 320 nm). Broad PL emissions = 430, 420, 395, 420 nm were noted for 5 × 100 nm W₁₈O₄₉ rods, 5 × 15 nm, CaWO₄ rods, 10 – 30 nm CaWO₄ dots, and 10 nm BaWO₄ diamonds, respectively.