Exfoliative Luminescent Hydrogen‐Bonded Organic Cocrystals With Large Stokes Shift Toward Optical Waveguide Sensing

ABSTRACT

Luminescent materials with large Stokes shifts (LSS) have attracted considerable research interest owing to their negligible self‐absorption, high energy utilization efficiency, and excellent optical anti‐interference performance, particularly advantageous for optical waveguide applications. However, the rigid solid‐state structure of conventional optical waveguide materials often restricts excited‐state conformational relaxation, posing a fundamental challenge to achieving an LSS. Herein, we report two hydrogen‐bonded organic cocrystals (HOCs) assembled from identical components, dodeca‐5,7‐diynedioic acid (DDA) and 4‐(2,4,5‐tripyridin‐4‐ylphenyl)pyridine (TPB), but with distinct stoichiometries, yielding markedly different photophysical properties. Confinement within a hydrogen‐bonding microenvironment enables the TPB‐DDA ₂ cocrystal (1:2 ratio) to exhibit bright green emission with an exceptional LSS of ∼215 nm, featuring an ultra‐low optical loss coefficient of 0.0032 dB µm ⁻¹ and an emission dichroic ratio of about 1.5. Notably, this HOC undergoes facile liquid‐phase self‐exfoliation to yield uniform one‐dimensional microrods that retain their green emission and waveguide performance even after extended suspension in aqueous media. These HOCs enables efficient fluorescence quenching toward short‐chain perfluoroalkyl acids (SC‐PFCAs), thereby facilitating the development of a novel optical waveguide‐based sensor of persistent environmental contaminants for SC‐PFCAs detection.