Co-assembly of gold nanocluster with imidazolium surfactant into ordered luminescent fibers based on aggregation induced emission strategy

Abstract

Metal nanoclusters (NCs) with outstanding luminescent nature have been engineered as an emerging material, while the application of NCs in aqueous solution is subjected to major limitations because of their luminescence quenching in water. Herein, imidazolium surfactant 1-hexadecyl-3-methylimidazoliumbromide (C16mimBr) with opposite charge was used to overcome this issue based on aggregation induced emission (AIE) strategy through mild co-assembly of Au-NCs with C16mimBr. Of interest is that not only the luminescence of Au-NCs was enhanced but also fibers with strikingly regular layer-like periodic structures were obtained which is rarely prepared at room temperature. The underlying mechanism for the formation of ordered fibers was systematically investigated by a series of experiments. Firstly, the electrostatic interaction between Au-NCs and C16mimBr induces the aggregation of Au-NCs while the directional H-bonding facilitates the elongation of aggregates into 1D ordered structures. Besides, the hydrophobic interaction of alkyl chains is also crucial for the formation of fibers. Importantly, the emission of fibers exhibited reversible pH-responsiveness, i.e. when adding H+, the emission turns off meaning that the aggregates disintegrate along with fluorescence quenching. While with the addition of equal OH−, it turns on again. Such a type of optical materials with ordered structure will have potential applications in pH sensors and photoelectronic devices. It can be expected that this work will serve as a simple and low-cost platform for the preparation of ordered luminescent materials based on metal NCs.