In
this article, a type of magnetic molecularly imprinted graphene
composite as a highly efficient adsorbent was prepared by forming
a molecularly imprinted sol–gel polymer on the surface of magnetic
graphene. The magnetic Fe3O4 nanoparticles were
first deposited on a graphene sheet to prepare the magnetic graphene
(MGR). Using the obtained magnetic graphene as a supporting matrix,
4-nitrophenol (4-NP) as template, phenyltriethoxysilane and tetramethoxysilane
as functional monomers, a magnetic molecularly imprinted graphene
composite (MGR@MIPs) was subsequently formed after the sol–gel
polymerization and extraction of 4-NP. The preparation conditions
(concentrations of monomer and template, and reaction time) were optimized.
The as-prepared MGR@MIPs was characterized by FTIR, VSM, SEM, and
TEM images. Under the optimized conditions, the obtained MGR@MIPs
exhibited ultrafast adsorption kinetics (2 min to achieve the equilibrium
state), large binding capacity (142 mg/g), and high selectivity toward
4-NP (the imprinting factor α is 4.25). In addition, a high
saturation magnetization of MGR@MIPs was demonstrated, which allows
easy separation from solution by applying an external magnetic field.
Meanwhile, MGR@MIPs can be regenerated and reused in successive six
cycles with slight loss in adsorption capacity. Finally, MGR@MIPs
was successfully used as a highly adsorbent material for the determination
and separation of 4-NP in real samples combining with high-performance
liquid chromatography (HPLC).
The vacuum, mechanical, and optical characteristics of a "Grasshopper" grazing incidence monochromator, for use with a synchrotron radiation source in the 30–300 eV range, is described. The monochromator is compatible with ultrahigh vacuum (≤ 5 × 10−10 Torr throughout), and the motor driven scan mechanism is linear and reliable. The monochromator has been calibrated using several known absorption edges between 36 and 102 eV and a nonlinear least squares fit to the scan equation. These same absorption edges, plus a scan over zero order, show that the present resolution of the monochromator (with 10 and 16 μm exit and entrance slits respectively) is 0.16 Å (0.06 eV at the Al L2.3 edge). With 10 μm entrance and exit slits, the resolution will be very close to the theoretical Δλ = 0.083 Å.
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