Flexible and transparent free-standing films with enhanced magnetic and luminescent anisotropy

Abstract

Flexible and robust free-standing films are fabricated via layer-by-layer (LBL) assembly of layered double hydroxide (LDH) nanoplatelets, poly(vinyl alcohol) (PVA) and a styrylbiphenyl derivative (BTBS), and show enhanced magnetic and luminescent anisotropy simultaneously. UV-vis absorption and fluorescence spectra demonstrate a stepwise and regular growth of the films upon increasing the number of deposition cycles. XRD, AFM and SEM indicate that the films possess a periodic layered and uniform surface morphology. In contrast to the disordered LDH/PVA/BTBS film prepared by a solvent evaporation method, the (LDH/PVA/LDH/BTBS)_n films with ordered structures exhibit enhanced magnetic and optical properties, including higher saturation magnetization, longer luminescence lifetime and stronger polarized photoemission. Moreover, owing to the highly arrayed 2D-organized structure formed through LBL assembly, the presence of the free-standing film means that the alignment of the spins of the LDH nanoplatelets in random directions is avoided and imparts a high level of dispersion and orientation to the BTBS, which displays enhanced magnetic and luminescent anisotropy. Therefore, this work provides a facile method for the fabrication of anisotropic 2D-organized materials based on the LDH/PVA/LDH/BTBS system, which can be potentially used in magneto-optical sensors, magnetic data storage and magneto-resistive devices.