Two-Dimensional Topological Structures Boost the Construction of Nonequilibrium Array for Optical Pressure Sensing

Pressure-induced optical materials show great potential in optical devices, pressure sensing, and information anticounterfeiting. However, pressure-induced room temperature phosphorescent (RTP) molecules in a thermodynamic steady state are insensitive to external stimuli, limiting their practical application. Here, layered double hydroxide (LDH) with a 2-D topological structures can bring carbon dots (CDs) into a thermodynamic nonequilibrium state, which is a prerequisite for the enhancement in pressure sensitivity. Furthermore, considering the inherent rigidity of LDH contradicts the pressure sensitivity, the dual buffering layers are introduced, where the borate ions and polymer polyvinyl alcohol (PVA) as internal and external buffer layers, respectively. The dual buffering layers can help interlayer molecules to achieve highly anisotropic arrangement and induce the initial formation of thermodynamic nonequilibrium arrays. Thus, the CDs@BO3-LDH-PVA film can change the RTP intensity significantly under the extremely low pressure of 12 MPa. This strategy links the nonequilibrium state with the buffer layer, which provides a new idea for the design of pressure-induced optical sensing material.