Stimuli-responsive fluorescence based on the solid-state bis[2-(2-benzothiazoly)phenolato]zinc(ii) complex and its fiber thin film

Abstract

While metal-based complexes with single-stimulus-responsive fluorescence have been largely developed recently, examples of dual-stimuli-responsive systems are still relatively limited. In this work, a bis[2-(2-benzothiazoly)phenolato]zinc(II) complex was synthesized through a one-step solution process, and the as-prepared solid-state sample exhibited fluorescent emission changes upon dual external stimuli such as mechanical force and pH. In addition, the related luminescent properties (such as wavelength, fluorescence lifetime, color, and two-photon emission) after mechanical- and pH-stimuli can be easily recovered and recycled several times. Moreover, to develop a film material for easy operation, the Zn(BTZ)₂ complex was further incorporated into a poly(vinyl alcohol) (PVA) matrix to obtain a microfiber thin film based on an electrospinning process, and the as-fabricated Zn(BTZ)₂@PVA system showed changeable luminescence upon heat treatment. These observations confirm that the Zn(BTZ)₂ complex is a stimuli-responsive luminescent system sensitive to pH and force external changes in the powder state, and sensitive to temperature changes in the film state. Therefore, compared with the well-developed noble metal-based complexes with stimuli-responsive properties, this work suggests that the Zn-based complex can provide an alternative to develop potential low-cost luminescent sensors and optical antiforgery systems.