Coordination-driven self-assembly of nanoZnO hybrids with tripodal zinc terpyridyl-viologen complex multilayers and their photochromic properties

Abstract Viologen (VIO) functionalized nanomaterials and supramolecular systems have attracted much attention because of their well reversible redox properties, unique photo-/electrochromic and radical-rich features that resulting in potential applications in the fields of coloration and memory devices, energy conversion and biomimetic chemistry. Here, a tripodal terpyridyl-viologen (TPyVIO) multidentate ligand was newly synthesized, which was then used as a linker, together with Zn2+ ion as a connector, to construct Zn-TPyVIO multilayers on the surfaces of nanoZnO particles to produce nanoZnO@(Zn-TPyVIO)n hybrids by a layer-by-layer (LBL) technique. Luminescent emission of nanoZnO semiconductors was largely quenched in the nanoZnO@(Zn-TPyVIO)n hybrids, attributed to a quick electron transfer from the conduction band of excited nanoZnO particles to viologens; this electron transfer process resulted in the formation of colored monovalent viologen radical cations. Reversible redox couple was recorded for the glass carbon electrode modified by the nanohybrids, with the cationic and anionic potentials at approximately −0.78 ~ −0.84 and −0.63 ~ –0.73 mV (vs Hg/Hg2Cl2), respectively. Finally, it was revealed that the nanoZnO@(Zn-TPyVIO)n hybrids displayed well photochromic behaviors under light radiation.