Enhanced reverse saturable absorption of electrostatic self-assembled layer by layer films containing (8-quinolineoxy-5-sulfonic acid)phthalocyanine cobalt and graphene oxide

Abstract

Multilayer films containing α-CoPc(QnSO₃Na)₄ (CoPc), polydiallydimethyldiallylammonium chloride (PDDA) and graphene oxide (GO) were fabricated through electrostatic self-assembled layer by layer (LBL) technique. UV-Vis spectroscopy was used to characterize the assembly process. Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were utilized to explore the microstructure of the film. The third-order nonlinear properties of the film were studied by Z-scan measurements at 532 nm with 4 ns pulses. When excited by laser with the input intensity of 1.16 μJ, the 25 bilayer CoPc/GO film exhibits strong reverse saturable absorption (RSA) effect. The nonlinear absorption coefficient β value is 1.6 × 10⁻⁵ m W⁻¹, which is 5 and 3 orders larger than that of CoPc solution sample and grapheme oxide solution sample, and 1.5 times larger than that of the 35 bilayer CoPc/PDDA film. And also, combination of UV-Vis spectroscopy with Raman spectroscopy was adopted to analyze the enhancement mechanism of nonlinear optical absorption of the film.