3 research outputs found
Ultrahigh Sensitivity of Au/1D α‑Fe<sub>2</sub>O<sub>3</sub> to Acetone and the Sensing Mechanism
Hematite (α-Fe<sub>2</sub>O<sub>3</sub>) 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-Fe<sub>2</sub>O<sub>3</sub> nanorods, which were then decorated homogeneously
by fine Au particles, yielding Au/1D α-Fe<sub>2</sub>O<sub>3</sub> 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-Fe<sub>2</sub>O<sub>3</sub> 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-Fe<sub>2</sub>O<sub>3</sub> 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 H<sub>2</sub>O and CO<sub>2</sub>), 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 Cu<sub>4</sub>O<sub>3</sub> Microspheres and Their Lithium Storage Properties
Phase-pure Cu<sub>4</sub>O<sub>3</sub> microspheres were
synthesized
for the first time via a facile solvothermal method, using CuÂ(NO<sub>3</sub>)<sub>2</sub>·3H<sub>2</sub>O 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 CuÂ(NO<sub>3</sub>)<sub>2</sub>. Pure Cu<sub>4</sub>O<sub>3</sub> microspheres with
a diameter of 2–10 μm could be obtained via the symproportionation
reaction (2CuO + Cu<sub>2</sub>O → Cu<sub>4</sub>O<sub>3</sub>), which was regarded not being feasible in aqueous media under mild
synthesis conditions. The electrochemical properties of the Cu<sub>4</sub>O<sub>3</sub> microspheres as anode materials for Li-ion batteries
were also investigated. Compared to the simple physical mixture of
CuO and Cu<sub>2</sub>O with an equivalent atomic ratio of 2:1, the
as-prepared Cu<sub>4</sub>O<sub>3</sub> 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 Cu<sub>4</sub>O<sub>3</sub> 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