10 / 2026-02-25 15:54:11

High-Pressure Crystallography-Optical spectroscopy reveals Piezochromic fluorescent γ- and β-polymorphs of Nanocarbon molecular crystals

crystal structure,photoluminescence,polymorphism,single crystal XRD

高压物理与材料科学 > 静高压物理与材料科学

Aromatic organic molecular solids with tuneable polymorphism are of increasing fundamental importance due to the high demand for functional materials in organic opto-electronics, organic semiconductors, and nanoelectronics. Ability to exhibit polymorphism is an important in materials science as it can lead to multiple materials with drastically different properties from the same chemical component. A prominent example is perylene (C₂₀H₁₂), carbon-rich polycyclic aromatic hydrocarbons (PAHs), where they exhibit two polymorphs with different molecular tilts and packing, significantly affect its band gap and fluorescence properties.[1]

Although much efforts have been made, a detailed understanding of the structure-property relationship in many PAHs remains elusive. This is primarily due to difficulties in developing stable and reproducible crystallization processes for various polymorphs. The energy differences between these polymorphs are often minute, rendering the systems highly sensitive to external conditions and making it difficult to control their formation, isolate specific polymorphs, and determine their crystal structures. In this contest, high-pressure characterization using a diamond anvil cell (DAC) has emerged as a powerful technique for discovering new polymorphs [2] and investigate their physical properties [3], as pressurization can directly alter molecular packing and intermolecular distances.

In this work, we demonstrate that the combination of in-situ synchrotron single-crystal XRD with multimodal spectroscopy is not just a diagnostic tool, but a powerful discovery platform for establishing comprehensive understanding to uncover pressure-induced structural and optical responses in π-conjugated solids. We selected coronene (C₂₄H₁₂) as a model system due to its high symmetry and well-defined self-trapped exciton emission at ambient pressure, providing an ideal benchmark for probing how intermolecular interactions dictate optoelectronic function. This work aims to establish a general methodology to efficiently identify and characterize previously inaccessible functional phases, not only suggesting that hydrostatic pressure can be used as a precise tool for tuning crystal structures, but also to generate a database containing both crystal structure and opto-electronic properties, that can provide a selective target for further crystal engineering.  



[1] K. Sato et al Chem. Phys. Lett. 730, 312-315 (2019)

[2] W. Zhou et al Commun. Chem. 7:209 (2024)

[3] T. Nakagawa et al Commun. Mater. 6:98 (2025)