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 Zn 2+ 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/Hg 2 Cl 2 ), respectively. Finally, it was revealed that the nanoZnO@(Zn-TPyVIO) n hybrids displayed well photochromic behaviors under light radiation.
BangSen Li,Wenya Zhu,Jinrui Liu,Shishu Sun,Yan Zhang,DaShuai Zhang,Chen Li,Jianjun Shi,Zaifeng Shi
A practical “grafting-from” strategy is described to grow photochromic polymer brushes bearing spiropyran (SP) functional groups on graphene oxide (GO) surfaces via surface-initiated ring-opening metathesis polymerization (SI-ROMP). The Grubbs II catalyst was fixed on the GO surface, and the norbornene derivatives functionalized using spiropyran were synthesized from this active site via the ROMP method. The results indicated that the spiropyran-modified polymer brushes were obtained on the GO surface in the form of thin films. The solubility of GO modified by spiropyran polymers (GO-SPs) in organic solvents was significantly improved. The GO-SPs exhibited excellent photochromic properties, including fast coloration/decoloration. The modified GO with an isomeric structure was colored in 90 s under ultraviolet irradiation and decolored in 360 s under white light. The fading kinetic rate in the dark was slow and the kinetic attenuation curve followed bi-exponential decay. The GO-SP composite materials took more than 2 h to return to thermodynamically stable forms. The reversible change in the water contact angle reached 8° after continuous cycling with ultraviolet and visible light. GO-SP maintained its photochromic performance and possessed excellent fatigue resistance after more than six successive UV/light cycles. This work describes a practical strategy for the preparation of photochromic polymer brush modified GO composite materials and extends the applications of GO in photochromic materials.
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