Reduced Graphene Oxide Chemically Modified with Aggregation-Induced Emission Polymer for Solid-State Optical Limiter

Abstract

Aggregation-induced emission (AIE) materials are usually not suitable for constructing solid nonlinear optical (NLO) devices because strong solid-state aggregation behavior would shorten the excited-state lifetime, add relaxation pathways, and thereby reduce effective NLO absorption. To address this problem a newly synthesized AIE material, poly{[9,9-bis(6-azidohexyl)-9H-fluorene]-alt-(1,1,2,2-tetraphenylethene)} (PAHFTP), was treated with reduced graphene oxide (RGO) to give the soluble derivative of poly[(9,9-dihexyl-9H-fluorene)-alt-(1,1,2,2-tetraphenylethene)] (PFTP) covalently grafted onto RGO (PFTP-RGO). Upon covalent grafting of PAHFTP onto the RGO surface, about 91.89 % of the fluorescence intensity of the PAHFTP film was quenched due to electron transfer from PFTP to RGO, which yielded PFTP^.+ -RGO^.- radical-ion pairs. The as-prepared PFTP-RGO was embedded into a non-optically active poly(methyl methacrylate) (PMMA) matrix to produce the PFTP-RGO/PMMA film with good optical quality. As expected, the PAHFTP/PMMA film did not show any NLO response. In contrast to the PFTP-RGO/PMMA and RGO/PMMA films, the annealed PFTP-RGO/PMMA exhibited superior OL performance, with low OL thresholds of 0.24 GW cm^-2 (1.44 J cm^-2 ) at 532 nm and 0.18 GW cm^-2 (1.08 J cm^-2 ) at 1064 nm. The damage thresholds of the annealed PFTP-RGO/PMMA film are around 33.88 J cm^-2 at 900 μJ at 532 nm and 37.32 J cm^-2 at 1000 μJ at 1064 nm, respectively.

Keywords: fluorescence; laser protection; nonlinear optics; optical limiters; polymers; reduced graphene oxide.