Luminescent Boron Materials for Imaging and Sensing

摘要

Luminescent boron?β-diketonate (bdk) dyes are known for their intense fluorescence, 2-photon absorbing capability, and environmentally sensitive emission. These useful properties have been incorporated into light emitting boron-containing materials. BF2bdks also display unusual optical properties in the solid state. Specifically, difluoroboron beta-diketonate-poly(lactic acid) derivatives exhibit both intense fluorescence and long-lived room temperature phosphorescence. When fabricated as nanoparticles, these dual-emissive biomaterials serve as cellular optical probes and in vivo ratiometric tumor hypoxia imaging agents with impressive combined spatial and temporal resolution. Boron nanoparticles also serve as a new kind of functional brain imaging agent, advancing neuroscience and epilepsy research in important ways. Difluoroboron β-diketonate dyes also show interesting properties as molecular solids. For example, the difluoroboron complex of avobenzone, BF2AVB a simple sunscreen ingredient, has narrow bandwidth green, cyan, or blue emission depending on the crystalline form. Furthermore, the emission color changes when crystals are crushed or thin films are scratched or gently rubbed. For thin films, the mechanochromic luminescence (ML) is reversible at room temperature. For the avobenzone complex, scratched regions return to the original background color within minutes at room temperature or seconds with heating. The writing-fading process may be repeated many times. Further structure-properties studies show that optical effects, force responsiveness and recovery time are molecular and aggregate structure, substrate, and temperature dependent and negative images are also possible. These simple Scratch the Surface Inks~(TM) show promise as mechanical sensors and rewritable surfaces. They have even inspired creative works in music, art and design.