Photo-organometallic, Nanoparticle Nucleation on Graphene for Cascaded Doping.
basic_science · Level V
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- Record sourced from PubMed, PMID 31609585.
- Also identified by DOI 10.1021/acsnano.9b05484.
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Abstract
Controlling the doping levels in graphene by modifying the electric potential of interfaced nanostructures is important to understand "cascaded-doping"-based applications of graphene. However, graphene does not have active sites for nanoparticle attachment, and covalently adding functional groups on graphene disrupts its planar sp<sup>2</sup>-hybridization, affecting its cascaded doping. Here we show a hexahepto (η<sup>6</sup>) photo-organometallic chemistry to interface nanoparticles on graphene while retaining the sp<sup>2</sup>-hybridized state of carbon atoms. For testing cascaded doping with ethanol interaction, transition metal oxide nanoparticles (TMONs) (Cr<sub>2</sub>O<sub>3</sub>/CrO<sub>3</sub>, MoO<sub>3</sub>, and WO<sub>3</sub>) are attached on graphene. Here, the transition metal forms six σ-bonds and π-back-bonds with the benzenoid rings of graphene, while its opposite face binds to three carbonyl groups, which enable nucleation and growth of TMONs. With a radius size ranging from 50 to 100 nm, the TMONs downshift the Fermi level of graphene (-250 mV; p<i>-</i>doping) <i>via</i> interfacial charge transfer. This is consistent with the blue shift of graphene's G and 2D Raman modes with a hole density of 3.78 × 10<sup>12</sup> cm<sup>-2</sup>. With susceptibility to ethanol, Cr<sub><i>x</i></sub>O<sub>3</sub> nanoparticles on graphene enable cascaded doping from ethanol that adsorbs on Cr<sub><i>x</i></sub>O<sub>3</sub>, leading to doping of graphene to increase the electrical resistance of the TMONs-graphene hybrid. This nanoparticle-on-graphene construct can have several applications in gas/vapor sensing, electrochemical catalysis, and high-energy-density supercapacitors.