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Synthesis and characterization of a multifunctional nanocatalyst based on a novel type of binary-metal-oxide-coated Fe₃O₄–Au nanoparticle

Zhang, Hongxing, Zhang, Yiwei, Zhou, Yuming, Zhang, Chao, Wang, Qianli, Xu, Yuanmei, Zhang, Mingyu
RSC advances 2016 v.6 no.22 pp. 18685-18694
Fourier transform infrared spectroscopy, X-ray diffraction, aminophenols, burning, catalysts, catalytic activity, energy-dispersive X-ray analysis, gold, iron oxides, magnetic materials, magnetism, microparticles, models, nanogold, nanoparticles, p-nitrophenol, reaction mechanisms, scanning electron microscopy, silica, surface area, thermal stability, thermogravimetry, titanium dioxide, transmission electron microscopy
A novel type of binary-metal-oxide-coated Au nanocatalyst, including a mixed oxide layer, a moveable magnetic Fe₃O₄ core and some Au NPs of 2–5 nm, has been synthesized successfully by a facile hydrothermal synthesis method. SEM, TEM, EDX, FTIR, XRD, and TGA were employed to characterize the prepared samples. The results showed the mSiO₂–TiO₂ layer could increase the thermal stability and reactivity of metal nanocatalysts compared to a pure TiO₂ or SiO₂ layer. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was employed as a model reaction to test catalytic performance in this work. The results showed that the binary-metal-oxide-coated nanocatalyst (550 °C) exhibited significantly enhanced catalytic performance compared with the pure SiO₂ (550 °C) or TiO₂ (550 °C). In particular, the mSiO₂–TiO₂/Au/C/Fe₃O₄ particles calcined at 550 °C showed the highest catalytic activity, compared to the samples calcined at 700 °C, 300 °C and RT. Meanwhile, because of C layer burning, the sample presented a few white spots between the Fe₃O₄ microsphere and the oxide layer, suggesting that the specific surface area was increased by calcination. The sample (550 °C) still has a certain degree of magnetism, suggesting the desired samples could be separated by magnet. Finally, to explain the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), a possible reaction mechanism was also proposed.