Cyclodextrin-functionalized graphene nanosheets, and their host-guest polymer nanohybrids

β-Cyclodextrin (CD)-functionalized (grafted) reduced graphene oxide (RGO-g-CD) nanosheets were prepared via solution-based synthesis in one-pot, involving the simultaneous solvothermal reduction of graphene oxide (GO) and nitrene addition of azido-labeled CD to RGO. Being water soluble, the grafted CD imparted good dispersibility and stability to the RGO-g-CD nanosheets in water. The RGO-g-CD nanosheets were further functionalized with poly(N-isopropylacrylamide-co-vinylferrocene(II)) (PNIPAM-Fc) and ferrocene-modified hyperbranched polyglycerol (HPG-Fc) via host-guest inclusion complexation of CD and ferrocene (Fc) moieties to form RGO-g-CD/Fc-PNIPAM and RGO-g-CD/Fc-HPG nanohybrids, respectively. Both RGO-g-CD/Fc-PNIPAM and RGO-g-CD/Fc-HPG nanohybrids were dispersible and stable in a wider range of solvents than the RGO-g-CD precursor nanosheets. Due to the thermoresponsive behavior of the attached PNIPAM moieties, the RGO-g-CD/Fc-PNIPAM exhibited reversible dispersibility in aqueous solution at a lower critical solution temperature (LCST) of 28 °C and thus could potentially be developed into thermoresponsive nanodevices. The RGO-g-CD/Fc-HPG nanohybrids exhibited low cytotoxicity towards 3T3 fibroblasts in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) cell viability assay.