Hanxun Qiu

Self-aligned graphene as anticorrosive barrier in waterborne polyurethane composite coatings

Graphene reinforced waterborne polyurethane (PU) composite coatings were fabricated on steel surfaces. When the filler content was 0.4 wt%, self-alignment of graphene was driven by the reduction of the total excluded volume. The superior anticorrosion properties were proven by electrochemical impedance spectroscopy (EIS) analysis for the PU matrix composite coating reinforced by 0.4 wt% of aligned graphene. The interaction mechanism between electrolyte and graphene layers was discussed for the three-dimensional randomly distributed graphene and the in-plane aligned graphene, respectively, to better understand their effects as anticorrosive barriers.

Microwave-assisted simultaneous reduction and titanate treatment of graphene oxide

Simultaneous reduction and functionalization of graphene oxide was conducted with the assistance of microwave irradiation. A titanate coupling agent was utilized for the functionalization of graphene. TEM, XPS and FTIR were employed to characterize the changes in graphene morphology and chemistry. The results suggested that the titanate coupling agent was bonded covalently on the graphene surfaces. The surface of graphene remained hydrophilic after the reduction of graphene oxide, while the electrical conductivity of graphene was partially restored. Titanate functionalized graphene was mixed with the waterborne polyurethane (PU) to prepare nanocomposites. The graphene/PU nanocomposites exhibited a conductive percolation threshold of 0.1 wt%.

Selective removal of metallic single-walled carbon nanotubes by microwave-assisted treatment of SWCNTs with nitronium ions

A facile and rapid technique for the selective removal of metallic single-walled carbon nanotubes (M-SWCNTs) was developed by microwave-assisted treatment of SWCNTs with nitronium ions. Upon exposure to microwaves, M-SWCNTs homogeneously dispersed in organic solution were prone to react with an electron acceptor reagent, i.e., positively charged nitronium ions as compared to their counterpart, namely, semiconducting (S)-SWCNTs. The well-functionalized M-SWCNTs were separated and removed from residual S-SWCNTs by ultracentrifugation and filtration. The resulting material contained highly enriched S-SWCNTs, the proportion of which increased from approximately 62 mol% in as-received SWCNTs to nearly 90 mol%. The effectiveness in removing M-SWCNTs was confirmed by the resonant Raman spectra and UV-vis-NIR absorption spectra. The microwave-enhanced separation mechanism was discussed as well.

Langmuir-Blodgett assembly of transparent graphene oxide-silver microwire hybrid films with an antibacterial property

Abstract Silver microwires (AgMWs) were made amphiphilic by non-covalent functionalization with poly (vinyl pyrrolidone) and hexadecyl mercaptan. The Langmuir-Blodgett (LB) technique was used to transfer graphene oxide (GO) and the functionalized AgMWs (F-AgMWs) onto a quartz substrate to obtain GO-AgMW hybrid films. The films had a high optical transparency and an antibacterial property against Escherichia coli (E. coli). It is proposed that the GO layer not only acts as an adhesive layer for AgMWs, but also is acidic, which provides an ideal reaction condition for AgMWs to release the Ag+ ions that fight E. coli. The influence of pH value on the antibacterial property of the hybrid films was investigated in order to verify the proposed mechanism. Further development of this method may provide a way to produce next generation transparent multifunctional thin films with antibacterial properties.