Realizing near-infrared mechanophosphorescence from an organic host/guest system

Abstract

Near-infrared mechanoluminescence materials have great potential in higher order encryption and biomechanical visualization in vivo because of their unique properties such as biopenetrability and invisibility to the naked-eye. However, organic NIR mechanoluminescence materials remain unexplored. Herein, the design, synthesis and photophysical studies of the first organic host/guest (H/G) NIR mechanoluminescence system with the organometallic complex Pt(II)F₂₀TPPL as the guest and N-hexyl carbazole (N-hexyl Cz) as the host are reported. Based on the efficient triplet energy transfer and rigid host environment in this H/G system, pure NIR mechanophosphorescence can be detected at 746 nm with high efficiency and the phosphorescence lifetime can be prolonged up to 167 μs when doping 2.0% (w/w) Pt(II)F₂₀TPPL into the N-hexyl Cz crystal. Further studies on theoretical calculations have been carried out to gain a deeper understanding of the energy transfer process in this organic H/G system. Additionally, when this material is subjected to a friction, the naked-eye invisible pure NIR mechanophosphorescence could be clearly detected using a NIR camera. This organic H/G NIR mechanophosphorescence material has also demonstrated potential application in higher order encryption and biomechanical visualization due to its naked-eye invisible pure NIR mechanophosphorescence.