A metastable molecular array guided by the synergy of confinement and charge repulsion for piezochromic sensors

Abstract

Piezochromic fluorescent materials have attracted the interest of the scientific community due to their obvious fluorescence emission or color change in response to external pressure or mechanical grinding stimulation. However, the aggregation-caused quenching (ACQ) of fluorescent molecules and their insensitivity to external stimuli in a thermodynamically stable state limit the application of piezochromic sensors. In this paper, three components are employed: 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) was selected to provide luminescence, layered double hydroxide (LDH) provides confinement space, and polyvinyl alcohol (PVA) provides repulsive interaction. The as-prepared composite material shows piezochromic behavior with a high sensitivity and good reversibility. The mechanism study shows that the confinement effect of LDH can create a metastable molecule array between layers; exclusion of PVA can further maintain a molecular metastable state. Based on the synergies mentioned above, the metastable HPTS molecule arrays can undergo significant fluorescence changes under an extremely low pressure of 10 MPa. This strategy introduces the molecular metastable effects, which provides a new idea for the development of low-pressure stimulated and high-precision piezochromic sensors.