Nowadays, afterglow materials with long-lifetime phosphorescence are mainly prepared from metal-containing substances. It is necessary and challenging to find a simple, green and feasible approach to generate afterglow materials with excellent phosphorescence from biomass materials. Herein, a facile strategy is proposed to construct afterglow materials via confining fluorescence carbon dots from lignin into silica (SiO₂). Specifically, a microwave-assisted carboxymethylation process was adopted for the lignin precursor, which endowed the lignin with abundant carboxyl groups (3.69 mmol g⁻¹) and maintained its benzene ring structure. Subsequently, N-doped lignin-based carbon dots (NL-CDs) with nanoscale size (6.07 nm) and excellent fluorescence (quantum yield = 30.6%) were prepared through the hydrothermal treatment of carboxymethylated lignin. Finally, the NL-CDs were confined in SiO₂ and the generated NL-CDs@SiO₂ exhibited excellent phosphorescence behavior in both solid-state and aqueous solution. The obtained afterglow materials achieved 5.97% of phosphorescence quantum yield and 834 ms of lifetime, which could be observed for 6 s by the naked eye. Meanwhile, a multi-modal information encryption strategy was designed based on the phosphorescence characteristics of the afterglow materials. The proposed strategy in this paper will pave the way to generate afterglow materials from lignin biomass and provide guidance for high-value utilization of lignin.

The electrostatic effects of separators under the internal electric field are often overlooked, leading to the unreliability of traditional theoretical models. Here we introduce the dielectric constant as a descriptor and develop a high dielectric constant fiber separator primarily composed of phosphorylated cellulose. Under the internal electric field, the intense electron displacement polarization within the high dielectric constant separator enhances the charge transfer kinetics and optimizes the solvation structure, thus mitigating the formation of amorphous organic oligomers at the solid-electrolyte interphase. Furthermore, the separator induces the formation of LiF, thereby forming a robust and low-resistance solid-electrolyte interphase. The separator exhibits high ionic conductivity (0.76 mS cm⁻¹ at 25 °C) and Li⁺ transference number (0.68). Consequently, the Li||LiFePO₄ pouch cell with the prepared separator achieve high specific energy exceeding 350 Wh kg⁻¹ (relative to the mass of pouch cells) under practical quantities of active materials and electrolyte.

The poor water solubility, large particle size, and low accessibility of cellulose, the most abundant bioresource, have restricted its generalization to carbon dots (CDs). Herein, nitrogen and sulfur co-doped fluorescent carbon dots (N, S-CDs) were hydrothermally synthesized using cellulose nanocrystals (CNC) as a carbon precursor, exhibiting a small particle size and excellent aqueous dispersion. Thiourea was selected as a nitrogen and sulfur dopant to introduce abundant fluorescent functional groups into N, S-CDs. The resulting N, S-CDs exhibited nanoscale size (6.2 nm), abundant functional groups, bright blue fluorescence, high quantum yield (QY = 27.4%), and high overall yield (16.2%). The excellent optical properties of N, S-CDs endowed it to potentially display a highly sensitive fluorescence “turn off” response to rutin. The fluorescence response for rutin allowed a wide linear range of 0–40 mg·L⁻¹, with a limit of detection (LOD) of 0.02 μM, which revealed the potential of N, S-CDs as a rapid and simple sensing platform for rutin detection. In addition, the sustainable and large-scale production of the N, S-CDs in this study paves the way for the successful high-value utilization of cellulose.