Cellulose Nanorods Modified with Polyethylenimine and Carbon Dots for Applications as Piezoelectric and Fluorescent Materials

The development of eco-friendly electroactive nanomaterials has attracted great attention in recent years. Here, a biogenic piezoelectric and fluorescent nanocomposite was designed and fabricated. Cellulose nanorods (CNRs) were first modified with polyethylenimine (PEI)-functionalized carbon dots (CDs) with dual-band green/yellow photoluminescence (PL). The CD-modified CNRs were incorporated into an electrospun poly(vinyl alcohol) (PVA) nanofiber with a piezo-phase alignment. CDs with an amino-rich polymeric chain not only enhanced the crystallinity of the CNRs but also mediated flexible linking between the CNRs and PVA matrix, which facilitated a large-scale preferential alignment of the CNRs in the nanofibers. The piezoelectric output voltage of the composite was improved two times through introduction of the CDs. Furthermore, the inhomogeneous distribution of the dual-emissive CDs in the nanofiber endowed the composite film with a unique thickness-dependent fluorescent chromic behavior. An information encryption was also realized owing to the structural-sensitive fluorescence of the composite film, which showed the high potential of the multifunctional nanocomposite in various applications.