Dual-Mode Circularly Polarized Light Emission and Metal-Enhanced Fluorescence Realized by the Luminophore–Chiral Cellulose Nanocrystal Interfaces

Abstract

Circularly polarized (CP) light has attracted wide attention for its great potential in broad applications. However, it remains a challenge to generate left-handed and right-handed circularly polarized (LCP and RCP) light from cellulose nanocrystal (CNC)-based materials only with an intrinsic left-handed chiral structure, owing to the pattern of CP light emission primarily based on the chirality of materials. Herein, a separation structure of luminophore layers and chiral CNCs was provided to achieve dualmode CP light emission by building a luminophore−chiral CNC interface. By directly exciting the back and front of two-layer films, LCP and RCP light could be easily emitted without any assisting means and specific setting angles. In addition, owing to the formation of the luminophore−chiral CNC interface, metal-enhanced fluorescence (MEF) was achieved to offset the brightness loss caused by circular polarization. By incorporating gold triangular nanoprisms in CNC chiral layers, the fluorescence enhancement of the ensemble was as high as 6.5-fold. The decisive role of the luminophore−chiral CNC interface in enhancing luminescence and dual-mode CP light emission was carefully investigated by contrasting the systems with and without luminophore−chiral CNC interfaces in this study. We believe that this dual-mode CP light emission film with MEF enables a promising approach to extending the application of CP light materials.

Polymer‐Based Circularly Polarized Luminescent Materials

“…Cellulose nanocrystals (CNCs), due to their intriguing hierarchical chirality, especially that derived from self-assembled cholesteric structures, are considered as powerful chiral nanomaterials to manufacture CPL-active platform. [43,[147][148][149][150][151][152][153] The hydroxyl and charged groups on the CNCs surface can form non-covalent bonds with achiral luminophores, such as organic luminophores, [16,149,[154][155][156][157] quantum dots, [158][159][160] carbon dots (CDs), [161][162][163][164][165] upconverting nanoparticles, [166] and so on. [167,168] The CPL performance of CNCs-based materials is summarized in Table 3.…”

Responsive Chiral Photonic Cellulose Nanocrystal Materials

“…Recently, there has been an increased focus on CNC-based CPL materials in which CNC acts as a chiral template to load achiral guest molecules, yielding strong CPL. [174][175][176][177][178] Due to the intrinsic left-handed chiral nematic structure of CNC films, right-handed CPL (RCPL) is detected. It has been reported that the CPL wavelength and intensity are related to the coupling between the luminescence and photonic bandgap.…”

Biomolecule‐Based Circularly Polarized Luminescent Materials: Construction, Progress, and Applications

“…Left-and right-handed CPL emission can be realized by directly exciting the back and front of the bilayer film. [126] NPs have good physical and chemical properties and rich emission spectra because of their unique 4 f-4 f electron transition in the inner shell. [127] Jalilah and coworkers reported that the 4 f-4 f transition in the thin-film state shows CPL after the rare-earth element (Eu III and Tb III ) tris(β-diketonate) complexes intercalate into cellulose triacetate, cellulose acetate butyrate, D-/L-glucose pentamethyl esters, and D-/L-arabinose tetramethyl esters.…”

“…In another work, they further developed the system and proposed novel dual‐mode CP light‐emitting films with MEF realized by the light emitter–AuTNP/CNC interface. Left‐ and right‐handed CPL emission can be realized by directly exciting the back and front of the bilayer film [126] . NPs have good physical and chemical properties and rich emission spectra because of their unique 4 f–4 f electron transition in the inner shell [127] .…”