Structural and Molecular Confinement of Luminescent Wood Hydrogel.

Wood is a typically hierarchical porous material with an anisotropic structure and properties. For example, the anisotropic optical performance of wood is often governed by its anisotropic structure. So far, the challenge remains in integrating anisotropic wood, yet with an isotropic light-scattering performance. Moreover, wood-based porous scaffolds have not been fully exploited in their investigation of structural and molecular confinement associated with optical properties. Herein, a luminescence-enhanced wood hydrogel is developed by combining with the three-dimensional -isopropylacrylamide (NIPAM) polymer network and the surface-carboxylated CdSe/ZnS quantum dots (QDs). Wood nanotechnology is applied to the nanostructural control of the wood-based hydrogel, which results in the isotropic optical performance and mechanical enhancement of the luminescent wood hydrogel. This associates with the mesoporous structure of the cellulose scaffold reinforced with the NIPAM hydrogel polymers, where the surface carboxyl groups of QDs are polarized and confined in the cellulose/NIPAM network. The luminescent property of the functional hydrogel can be tailored by altering the temperature around the critical solution temperature of the NIPAM polymers. The domain confinement effect of a wood-based hydrogel on QDs in terms of molecules and structures is investigated. Furthermore, the functional hydrogel demonstrates a great potential for the smart window application with optical regulation, energy savings, and UV-shielding characteristics. We envision that this functional wood-based hydrogel could be applied in the fields of biological imaging, flexible optics, smart sensors, and anticounterfeiting tags.