Graphene holds great potential for
fabricating ultrathin selective
membranes possessing high permeability without compromising selectivity
and has attracted intensive interest in developing high-performance
separation membranes for desalination, natural gas purification, hemodialysis,
distillation, and other gas–liquid separation. However, the
scalable and cost-effective synthesis of nanoporous graphene membranes,
especially designing a method to produce an appropriate porous polymer
substrate, remains very challenging. Here, we report a facile route
to fabricate decimeter-scale (∼15 × 10 cm2)
nanoporous atomically thin membranes (NATMs) via the direct casting
of the porous polymer substrate onto graphene, which was produced
by chemical vapor deposition (CVD). After the vapor-induced phase-inversion
process under proper experimental conditions (60 °C and 60% humidity),
the flexible nanoporous polymer substrate was formed. The resultant
skin-free polymer substrate, which had the proper pore size and a
uniform spongelike structure, provided enough mechanical support without
reducing the permeance of the NATMs. It was demonstrated that after
creating nanopores by the O2 plasma treatment, the NATMs
were salt-resistant and simultaneously showed 3–5 times higher
gas (CO2) permeance than the state-of-the-art commercial
polymeric membranes. Therefore, our work provides guidance for the
technological developments of graphene-based membranes and bridges
the gap between the laboratory-scale “proof-of-concept”
and the practical applications of NATMs in the industry.
We present a kind of aperiodic structure for the generation of multiple-wavelength second harmonic in a quasi-phase-matching scheme. In order to confirm its efficiency, a LiTaO3 superlattice with such an aperiodic domain-inverted structure was designed and fabricated. The second-harmonic generation at four present wavelengths was experimentally demonstrated from the superlattice with high and nearly equal conversion efficiencies. The tested result is in good agreement with theoretical consideration. The method may be used for the design of optical superlattices to construct multiple-wavelength lasers and wavelength converters for all-optical network.
Membranes are widely used for liquid separations such as removing solute components from solvents or liquid/liquid separations. Due to negligible vapor pressure, adjustable physical properties, and thermal stability, the application of ionic liquids (ILs) has been extended to fabricating a myriad of membranes for liquid separations. A comprehensive overview of the recent developments in ILs in fabricating membranes for liquid separations is highlighted in this review article. Four major functions of ILs are discussed in detail, including their usage as (i) raw membrane materials, (ii) physical additives, (iii) chemical modifiers, and (iv) solvents. Meanwhile, the applications of IL assisted membranes are discussed, highlighting the issues, challenges, and future perspectives of these IL assisted membranes in liquid separations.
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