Haiqing Yao

Facile decoration of Au nanoparticles on reduced graphene oxide surfaces via a one-step chemical functionalization approach

A facile way to fabricate functionalized and reduced graphene oxide (RGO) was reported by introducing the dual-function reagent N1-(3-trimethoxysilylpropyl) diethylenetriamine (TSPD), in which (i) the amine functional groups of the organosilane can effectively restore the π bonds of the GO; and (ii) the silanol parts react with the hydroxyl groups of GO and subsequently cross-link to form a monolayer on the graphene surface. The exposed amine groups of the functionalized GO could effectively template the Au nanoparticles (AuNPs) assembly on the graphene surface with high density and good dispersity. TEM images indicate that AuNPs retained their original size and were well-anchored on the graphene surfaces with an average inter-particle distance of 15 nm. The resultant graphene sheets decorated by AuNPs has the capability of sensing single molecules on its surface, e.g., Rhodamine 6G (Rh6G), through the surface-enhanced Raman spectroscopy (SERS).

Self-assembly of Au nanoparticles on graphene sheets as a catalyst with controlled grafting density and high reusability

In the present work, we have developed a method to achieve self-assembly of Au nanoparticles (NPs) on graphene sheets through chemical functionalization. Transmission electron microscopy and UV-Vis spectroscopy results indicate that the grafting density of Au NPs on graphene sheets can be controlled by changing the types of functional groups. The ability to control the density of Au NPs cannot be overestimated, because it provides tunable catalytic activity. These graphene/Au composites display good stability against agglomeration and show excellent catalytic activity in a model reduction reaction of 4-nitrophenol into 4-aminophenol. This study demonstrates a general approach to the preparation of tunable and reusable catalysts containing densely loaded and well dispersed Au NPs.

Highly efficient oil–water separators based on dual superhydrophobic and superoleophilic properties of multiwall-carbon nanotube filtration films

A new alkyl-pyrene has been synthesized and is used to modify multiwall-carbon nanotube to form films that are both superhydrophobic and superoleophilic. The superhydrophobic property of the MWCNT films prevents water from going through and the superoleophilic property of the films attracts oil, facilitating it to pass through the MWCNT filtration films. This film can also be easily recycled to prepare brand new water–oil separation filters and can be easily scaled up for large sizes. Our results reveal that the modified MWCNT film prepared here is a promising candidate for use in removal of oils and other organic pollutants from water.

Effect of surface modifier on flow properties of epoxy suspensions containing model plate-like nanoparticles

The influence of inter-particle interaction on the rheology of an uncured epoxy containing model α-zirconium phosphate (ZrP) nanoplatelets with aspect ratio of 160 is reported. Epoxy suspensions containing nanoplatelets exfoliated with tetra-n-butyl ammonium hydroxide (TBA), a low molecular weight quaternary ammonium cation, show short-range repulsive potential with weak elastic response at low concentration. At semi-dilute concentrations, the suspensions are solid-like at intermediate frequency and transition to viscous flow for time scales longer than the rotary diffusion process. The weak elasticity at intermediate frequency is attributed to the effect of Brownian motion on the rotational motion of the isolated plates. Suspensions containing nanoplatelets exfoliated with hydrophilic polyetheramine oligomers show similar behaviour to the ZrP-TBA system, but shifted to lower concentration. The rheological behaviour is attributed to steric stabilization of the nanoplatelets by extended oligomer brushes with short-range repulsive interactions. For suspensions containing nanoplatelets exfoliated with hydrophobic polyetheramines with shorter length, there is evidence for elastic response on local length scales and the flow behaviour shows strong history and temperature dependence. Rheological signatures associated with equilibrium nanoplatelet dispersions with repulsive interactions are discussed.