a team of researchers from brown university has developed a method for producing metal oxide films with intricate crumple patterns that have demonstrated greater electrical conductivity, which builds on research on crumpled graphene oxide sheets that the team published in march.
wrinkled graphene has been used as a templates for metal oxide films. (brown university)
in its original work, researchers introduced wrinkles and crumpled structures in graphene oxide sheets at the nanoparticle level. they accomplished this by compressing the sheets multiple times, which gave the graphene advanced water resistance and electrical conductivity, according to a report on the brown website.
metal oxides are much stiffer and the compression technique would not work because compression would crack the material. instead, the researchers used the graphene sheets as templates for making the crumpled metal oxides.
the graphene sheets were placed in a water-based solution with positively-charged metal ions. the negatively charged graphene would pull the ions into the spaces between the sheets where they would bond in the interlayer space, matching the contours of the graphene.
the graphene was oxidized away leaving wrinkled metal oxide sheets. researchers showed that the process worked with zinc, aluminum, manganese and copper oxides.
according to the report, “they showed that wrinkled manganese oxide, when used as a battery electrode, had charge-carrying capacity that was four times higher than a planar sheet. that’s probably because the wrinkle ridges give electrons a defined path to follow, enabling the material to carry more of them at a time.”
the abstract of the report, which was published in acs nano, stated:
“confined assembly in the intersheet gallery spaces of two-dimensional (2d) materials is an emerging templating route for creation of ultrathin material architectures. here we demonstrate a general synthetic route for transcribing complex wrinkled and crumpled topographies in graphene oxide (go) films into textured metal oxides.
“intercalation of hydrated metal ions into textured go multilayer films followed by dehydration, thermal decomposition, and air oxidation produces zn, al, mn, and cu oxide films with high-fidelity replication of the original go textures, including ‘multi-generational’, multi-scale textures that have been recently achieved through extreme graphene compression.
“the textured metal oxides are shown to consist of nanosheet-like aggregates of interconnected particles, whose mobility, attachment, and sintering are guided by the 2d template. this intercalation templating approach has broad applicability for the creation of complex, textured films, and provides a bridging technology that can transcribe the wide variety of textures already realized in graphene into insulating and semiconducting materials.
“these textured metal oxide films exhibit enhanced electrochemical and photocatalytic performance over planar films and show potential as high-activity electrodes for energy storage, catalysis and biosensing.”
read the full report at http://pubs.acs.org/doi/abs/10.1021/acsnano.6b05179.
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