Seeking Brightness from Nature: J-Aggregation-Induced Emission in Cellulolytic Enzyme Lignin Nanoparticles

Nanomaterials that show aggregation-induced emission (AIE) have tremendous potential in sensors, bioimaging, phototherapy and organic light-emitting diodes. Although big progress have been achieved in developing AIE nanomaterials and their applications, one downside of most previously described AIE nanomaterials is that they required the complicated organic synthesis of precursor molecules and several preparative steps. Here, a biomass material, cellulolytic enzyme lignin (CEL), was used to prepare AIE nanoparticles (CEL-NPs) by a simple one-step self-assembly method. The J-aggregates were formed in CEL-NPs, which were shown to be the reason for fluorescence emission. The fluorescence of CEL-NPs demonstrated temperature-dependent property and better resistance to photobleaching than that of commercially available 4′,6-diamidino-2-phenylindole (DAPI) dye. The colloidal size of CEL-NPs could be tuned from 80 to 600 nm via changing CEL concentrations and solvent exchange. CEL-NPs showed nice colloidal stability in acidic environment and at low temperature. CEL-NPs and a poly(vinyl alcohol) (PVA)/CEL-NPs composite film demonstrated good fluorescent responses to formaldehyde (FA) solution and vapor, respectively. This work opens up new possibilities for preparation of AIE nanomaterials and also provides a new high value-added routing for utilization of CEL.