Photoswitchable Macroscopic Solid Surfaces Based On Azobenzene‐Functionalized Polydopamine/Gold Nanoparticle Composite Materials: Formation, Isomerization and Ligand Exchange

The facile preparation of dynamic interfaces is presented based on the combination of photoisomerizable azobenzenes and polydopamine (PDA)/Au nanoparticle composite materials. Azobenzenes with different spacer lengths (C3, C6) and surface‐binding groups (SH, NH2) were synthesized. The polymer layer on macroscopic quartz surface was prepared by the facile aerobic autopolymerisation of dopamine hydrochloride under basic conditions. The presence of redox‐active catechol moieties meant that gold nanoparticles were formed on the polymer surface. The obtained UV‐Vis spectroscopic results confirmed that following their successful assembly, the switching of azobenzenes on PDA/Au was not affected by the surface binding group and the spacer length of the azobenzene molecules under the measurement conditions. Furthermore, facilitated by the curved nature of the Au particles, the surface‐bound azobenzene layer could be reconstructed by ligand‐exchange processes, and the photochemical characterization of the mixed layer was performed. Dynamic interfaces: Macroscopic surfaces composed of polydopamine and gold nanoparticles were constructed and functionalized with photoswitchable azobenzenes. The surface‐bound molecules could be reversibly photoisomerized because of the sufficient free volume provided by the curved nanoparticles. Furthermore, the curved nature of the gold particles facilitated the molecular reconstruction of the surfaces through ligand‐exchange processes.