Designed Metal-Free Quasi-1D Crystals with Giant Birefringence

초록

Birefringence, a vital property of anisotropic crystals, is indispensable for advanced optical technologies. Quasi-1D structures, with their inherent structural anisotropy, offer fertile ground for discovering materials with exceptional optical anisotropy. In this work, we report four metal-free quasi-1D crystals-(C5H6NO)+(NO3)-(4HPN), (C5H6NO)+(HC2O4)-(4HPO), (C4N3H6)+(NO3)-(2APMN), and (C4N3H6)+(HC2O4)-<middle dot>H2O (2APMO)-designed to feature pseudo-chain structures and grown as centimeter-scale crystals via a facile aqueous-solution method. These crystals display wide bandgaps (3.40-4.48 eV) and exceptional birefringence, with calculated values up to 0.555@546 nm and an experimental maximum of 0.597@546 nm for 4HPN. The giant birefringence stems from their quasi-1D architectures, high-spatial density, and optimal arrangement of the birefringence-active groups (BAGs). This study highlights the promise of metal-free quasi-1D materials for next-generation miniaturized polarization optics and laser-driven applications.

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