The present work describes the fabrication of superhydrophobic and superoleophilic reduced graphene oxide-coated cotton (rGO@cotton) by a facile one-step hydrothermal used method for oil-water separation. Results from X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM) analysis show the formation of a composite structure with the presence of an ultrathin coating of rGO on the cotton fibers. The contact angle (CA) between a static water droplet and the rGO@cotton surface in air was measured ~ 162.9°, which suggests the formation of a superhydrophobic surface on the synthesized product. Moreover, the rGO@cotton showed excellent absorption capacity for oils where 1 g of rGO@cotton was able to remove ~ 30-40 g of various oils in the first cycle from oil-water mixtures. The flexible rGO@cotton was reusable and demonstrated oil retention up to ~ 35-50% at the tenth cycle using simple sorption-mechanical squeezing test. Overall, the present work identifies that the rGO@cotton is an efficient absorbent for effective separation of oil from oil-water mixtures.

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A polyacrylamide inverse-opal hydrogel (IOH PAM ) film was synthesized by in situ polymerization in a polystyrene colloidal crystal template. The IOH PAM has a periodically ordered interconnecting porosity that endows the film with a band gap and structural color. The IOH PAM film exhibits a rapid reversible change in volume and in refractive index in response to alcohols and, consequently, the structural color and reflection peak of the IOH PAM film are quickly synchronized with these changes. The reflection peak of the IOH PAM film shows obvious blue or red-shifts that depend on the structure of the alcohols. The extent of the shift not only depends on the number of -OH groups, but also on the chain length, structure and concentration of the alcohols. The IOH PAM film is also sensitive to polyethylene glycol (PEG) and displays different blue-shift responses to PEGs with different molecular weights. Since the IOH PAM films have different reflectance spectra and structural colors in response to different types and concentrations of alcohols, this provides a potential way to visually detect alcohols.

An environmentally friendly approach to reduce graphene oxide (GO) with L-lysine (L-Lys) was developed by using carboxymethyl starch (CMS) as a stabilizing agent and a stable suspension of reduced graphene oxide (RGO) was obtained. UV visible absorption spectroscopy was used to monitor the deoxygenating process and the factors that affect the GO reduction, such as the ratio of GO/L-Lys, the temperature and pH were optimized. The reduction of the GO was verified by Fourier transform infrared spectroscopy, Xray diffraction, thermo-gravimetric analysis, Raman spectroscopy and X-ray photoelectron spectroscopy.Ordered porous RGO/CMS foams were prepared by a unidirectional freeze-drying method (UFDM) and used as absorbents for copper ions. Since L-Lys and CMS are natural and edible chemicals, this approach provides a green method to produce stable RGO from GO on a large scale. The nontoxic biodegradable RGO/CMS foams show potential applications for metal ions removal from wastewater.