Ultrahigh Sensitivity of Au/1D α‑Fe₂O₃ to Acetone and the Sensing Mechanism

Hematite (α-Fe₂O₃) is a nontoxic, stable, versatile material that is widely used in catalysis and sensors. Its functionality in sensing organic molecules such as acetone is of great interest because it can result in potential medical applications. In this report, microwave irradiation is applied in the preparation of one-dimensional (1D) α-FeOOH, thereby simplifying our previous hydrothermal method and reducing the reaction time to just a few minutes. Upon calcination, the sample was converted to porous α-Fe₂O₃ nanorods, which were then decorated homogeneously by fine Au particles, yielding Au/1D α-Fe₂O₃ at nominally 3 wt % Au. After calcination, the sample was tested as a potential sensor for acetone in the parts per million range and compared to a similarly loaded Pt sample and the pure 1D α-Fe₂O₃ support. Gold addition results in a much enhanced response whereas Pt confers little or no improvement. From tests on acetone in the 1–100 ppm range in humid air, Au/1D α-Fe₂O₃ has a fast response, short recovery time, and an almost linear response to the acetone concentration. The optimum working temperature was found to be 270 °C, which was judged to be a compromise between the thermal activation of lattice oxygen in hematite and the propensity for acetone adsorption. The surface reaction was investigated by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and a possible sensing mechanism is proposed. The presence of Au nanoparticles is believed to promote the dissociation of molecular oxygen better in replenishing O vacancies, thereby increasing the instantaneous supply of lattice oxygen to the oxidation of acetone (to H₂O and CO₂), which proceeds through an adsorbed acetate intermediate. This work contributes to the development of next-generation sensors, which offer ultrahigh detection capabilities for organic molecules

Facile Solvothermal Synthesis of Phase-Pure Cu₄O₃ Microspheres and Their Lithium Storage Properties

Phase-pure Cu₄O₃ microspheres were synthesized for the first time via a facile solvothermal method, using Cu­(NO₃)₂·3H₂O as the precursor. A formation mechanism was proposed based on the observation of a series of reaction intermediates. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, temperature-programmed reduction and oxidation, X-ray photoelectron spectroscopy, and nitrogen adsorption. It was found that the composition of the prepared products were highly dependent on the synthesis conditions, particularly the hydrate water content in the copper precursor of Cu­(NO₃)₂. Pure Cu₄O₃ microspheres with a diameter of 2–10 μm could be obtained via the symproportionation reaction (2CuO + Cu₂O → Cu₄O₃), which was regarded not being feasible in aqueous media under mild synthesis conditions. The electrochemical properties of the Cu₄O₃ microspheres as anode materials for Li-ion batteries were also investigated. Compared to the simple physical mixture of CuO and Cu₂O with an equivalent atomic ratio of 2:1, the as-prepared Cu₄O₃ exhibited unique lithium storage behaviors at a low voltage range and superior electrochemical performances as an anode material for Li-ion batteries. The successful preparation of pure Cu₄O₃ material could provide opportunities to further explore its physicochemical properties and potential applications

Hollow Fiber Membrane Decorated with Ag/MWNTs: Toward Effective Water Disinfection and Biofouling Control

The currently applied disinfection methods during water treatment provide effective solutions to kill pathogens, but also generate harmful byproducts, which are required to be treated with additional efforts. In this work, an alternative and safer water disinfection system consisting of silver nanoparticle/multiwalled carbon nanotubes (Ag/MWNTs) coated on a polyacrylonitrile (PAN) hollow fiber membrane, Ag/MWNTs/PAN, has been developed. Silver nanoparticles of controlled sizes were coated on polyethylene glycol-grafted MWNTs. Ag/MWNTs were then covalently coated on the external surface of a chemically modified PAN hollow fiber membrane to act as a disinfection barrier. A continuous filtration test using <i>E. coli</i> containing feedwater was conducted for the pristine PAN and Ag/MWNTs/PAN composite membranes. The Ag/MWNT coating significantly enhanced the antimicrobial activities and antifouling properties of the membrane against <i>E. coli</i>. Under the continuous filtration mode using <i>E. coli</i> feedwater, the relative flux drop over Ag/MWNTs/PAN was 6%, which was significantly lower than that over the pristine PAN (55%) at 20 h of filtration. The presence of the Ag/MWNT disinfection layer effectively inhibited the growth of bacteria in the filtration module and prevented the formation of biofilm on the surface of the membrane. Such distinctive antimicrobial properties of the composite membrane is attributed to the proper dispersion of silver nanoparticles on the external surface of the membrane, leading to direct contact with bacterium cells