Stress-assisted, clustering-triggered visual emission of cellulose-based materials

Abstract

Cellulose-based materials can be classified as non-conventional luminogens that produce photoluminescence (PL) in the visible range due to specific intermolecular arrangements. Usually such an arrangement is referred to as clusterization. Here, we demonstrate the importance of intramolecular arrangement of ethyl cellulose and bacterial cellulose that demonstrate tunable photoluminescence with multiexponent decay. We show that the observed emission is due to a n–π* electronic transition of carbonyl groups, whose emission intensity depends on the form of the sample preparation, either the powder-form or spin-coated films, displaying different density of the emitting regions on the microscale. Particularly, it is shown that PL emission is produced from disordered amorphous regions rather than from crystalline ones. We show that the emission is also promoted by mechanical stress applied to the sample that is suggested to facilitate formation of hydrogen-bonded carbonyl groups. The observed stress-assisted emission opens up the potential perspective of using this phenomenon in printed photonic devices.