Facile fabrication of robust self-cleaning fluorine-free reduced graphene oxide based superhydrophobic surfaces

Inspired from nature, superhydrophobic surfaces having selective water repelling properties were facilely fabricated without using any fluorinated chemicals. The sessile water contact angle (CA) approximate to 168 degrees with low contact angle hysteresis (CAH) was achieved on this reduced graphene oxide (rGO) surface. Typically, low surface free energy chemicals are employed to fabricate extreme water repellent surface. Herein, graphene oxide (GO) and rGO were coated by drop casting method. Superhydrophobic surfaces were fabricated by coating rGO on one side of the double-sided adhesive tape. The surface wettability of the GO and rGO surfaces were characterized by drop shape analyzer. The water contact angle increases from 61 degrees on GO coated surface to CA approximate to 168 degrees extreme partial wetting (superhydrophobic) for rGO coatings. The CAH reduces from similar to 27 degrees to less than 5 degrees for rGO coated surface. The adhesion of GO and rGO was also achieved using epoxy resin and the surface wettability was compared. The unique combination of surface chemistry and roughness provided very high CA. The surface was stable against hot water, chemicals (acids, bases, alkali) and mechanical abrasion. On such low CAH surface, the self-cleaning ability was shown by removal of deposited impurity by jet of water drops.