GO@Polyaniline Nanorod Array Hierarchical Structure: A Photothermal Agent with High Photothermal Conversion Efficiency for Fast Near-Infrared Responsive Hydrogels

Near-infrared (NIR) responsive hydrogels are of significance in remote control microvalves. However, the development and the application of NIR responsive hydrogels were either limited by high cost or limited by long response time (on the order of minutes) and modest volume change. To address this problem, in this work, a graphene oxide@ polyaniline (GO@PANI) hybrid nanocomposite with nanorod array hierarchical structure was fabricated by dilute polymerization. The as-synthesized hierarchical GO@PANI nanosheets exhibited high NIR photothermal conversion efficiency (PTCE) (49%), which was approximately 188% the magnitude of that of GO sheets. Due to its high photothermal conversion efficiency, when GO@PANI was incorporated into temperature-responsive poly(N-isopropylacrylamide) (PNIPA), a highly responsive hydrogel with rapid and significant NIR-induced volume change (over 50%) was obtained. When this material was applied as a remote-controllable microvalve, it exhibited a fast NIR response (similar to 30 s).