RESUMO
In this work, reduced graphene oxide (RGO) was used as a material to fabricate superhydrophobic lotus-leaf-like surfaces through soft-lithographic duplication. In the process, a polydimethylsiloxane (PDMS) stamp was prepared by replica molding against the surfaces of fresh lotus leaves that functioned as masters. A dispersion of octadecylamine-modified reduced graphene oxide (ODA-RGO) in tetrahydrofuran (THF) was used as "ink". The lotus-leaf-like surfaces were fabricated by microcontact printing on the solid substrates. The results showed that due to the good processibility of the ODA-RGO dispersion, the printed layers display papillary micro/nano-structures with high fidelity to the surfaces of lotus leaves. The RGO-based lotus-leaf-like surfaces possess superhydrophobic characteristics with a water contact angle larger than 160° and the contact angle hysteresis less than 5°. Due to the excellent chemical stability of the RGO sheets, as-prepared surfaces show remarkable superhydrophobic stability. The lotus-leaf-like surfaces maintain the superhydrophobicity after heating treatment at 150 °C for 24 h or being exposed to corrosive solutions with different pH values for 12 h. The present findings prove that the RGO-based material is an ideal candidate for fabrication of environment-durable lotus-leaf-like surfaces, which can be expected to have applications in different areas.
RESUMO
Properly controlling the rheological properties of nanoparticle inks is crucial to their printability. Here, it is reported that colloidal gels containing a dynamic network of graphene oxide (GO) sheets can display unusual rheological properties after high-rate shearing. When mixed with polyaniline nanofiber dispersions, the GO network not only facilitates the gelation process but also serves as an effective energy-transmission network to allow fast structural recovery after the gel is deformed by high-rate shearing. This extraordinary fast recovery phenomenon has made it possible to use the conventional air-brush spray technique to print the gel with high-throughput and high fidelity on nonplanar flexible surfaces. The as-printed micro-supercapacitors exhibit an areal capacitance 4-6 times higher than traditionally spray-printed ones. This work highlights the hidden potential of 2D materials as functional yet highly efficient rheological enhancers to facilitate industrial processing of nanomaterial-based devices.
RESUMO
Herein we report a new approach to fabricating nanoscrolls through the self-assembly of graphene oxide (GO) sheets in a dispersion. The assembly process for GO nanosheets was induced by the dropwise addition of an appropriate organic solvent such as N,N-dimethylformamide (DMF) into the aqueous dispersion. The results show that nanoscrolls were gradually formed from the GO sheets by rolling-up in a piece-by-piece manner with the increase of the DMF content. The transmission electron microscopic analysis indicates that for a typical case, the nanoscrolls have an average diameter of 242 ± 102 nm at the central part and the interlayer spacing between adjacent GO layers is 0.58 nm. The scrolls were estimated to have 207 turns and include on average 42 pieces of GO sheets per scroll. By this method, GO sheets with different sizes and oxidation degrees were proved to be able to form GO nanoscrolls in a similar way. Moreover, it is interesting that the diffraction efficiency of surface-relief-gratings photoinduced on the film of azo molecular glass was significantly enhanced by doping the GO nanoscrolls with a very low content (0.5 wt%); this suggests a possible new application for the GO scrolls in optical devices. This facile approach, which is also feasible by using other organic solvents such as ethanol, can be used to fabricate GO nanoscrolls for large scale applications in supercapacitors, sensors and other devices.
