Controlling the photoactuation in free-standing polydopamine/rGO nanofilms

Graphene derivatives, such as graphene oxide (GO), hold significant potential in photonics, photoelectronics, photosensing, and photoactuation. However, their widespread application is hindered by a trade-off between processability and desired properties. GO, while easily dispersible, lacks conductivity. Conversely, reduced graphene oxide (rGO) is conductive but challenging to integrate into solution-based or flexible systems. We present a novel one-pot method to simultaneously reduce GO and embed it within free-standing polydopamine (PDA) films. This process utilizes boric acid and mild hydrothermal treatment, yielding boric acid-modified polydopamine and reduced graphene oxide (BAPDA/rGO) films. These films exhibit enhanced electrical conductivity compared to pure PDA, demonstrating high sensitivity to both white and UV light, even at low power densities (2 mW cm-2). Furthermore, the photoactuation behavior of BAPDA/rGO films is unique. The thermal expansion of rGO dominates over the typical water desorption-induced contraction of PDA, resulting in an opposing photoresponse to pure PDA. This characteristic opens doors for complementary applications. These mechanically robust, nanometrically thin films are transferable to diverse surfaces, making them highly promising for flexible nanoengineering solutions.