Luminescent Transparent Wood Based on Lignin-derived Carbon Dots as a Building Material for Dual-channel, Real-time and Visual Detection of Formaldehyde Gas.

Formaldehyde (FA) is a widespread indoor air pollutant, and its efficient detection is a large industrial challenge. The development of a building material with real-time and visual self-detection of FA gas is highly desirable for meeting both construction and human health demands. Herein, a luminescent transparent wood (LTW) as the building material was developed for dual-channel, real-time, and visual detection of FA gas. It was fabricated by encapsulating multicolor lignin-derived carbon dots (CDs) and poly (vinyl alcohol) (PVA) into a delignified wood framework. It exhibited 85% optical transmittance, tunable room temperature phosphorescence (RTP) and ratiometric fluorescence (FL) emission. The tunable luminescence was attributed to different CD graphitization and surface functionalization. The color-responsive ratiometric FL and delayed RTP detections of FA were displayed over the range 20-1500 μM (R2=0.966, LOD=1.08 nM) and 20-2000 μM (R2=0.977, LOD=45.8 nM), respectively. The LTW was also used as an encapsulation film on a UV-emitting InGaN chip to form white light emitting diodes, indicating the feasibility as a FA-responsive planar light source. The operational notion of functional LTW can expand its applications to new fields such as stimuli-responsive light-transmitting window or planar light sources, while monitoring indoor air pollutants, temperature and humidity.