Run Li, Pan Liu, Xinyao Mao, Jia Zhang, Ya Zou, Yuxin Xue, Helan Zhang, Ruijuan Wen, Liping Ding, Haonan Peng*, and Yu Fang. J. Phys. Chem. C 2026, 130 (32), 11321-11330. DOI: 10.1021/acs.jpcc.6c04279

*Published as part of The Journal of Physical Chemistry C special issue “Yu Fang Festschrift”.

This research was selected for the inside front cover of The Journal of Physical Chemistry C.

Aniline is an important volatile aromatic amine widely used in the dye, pharmaceutical, and fine-chemical industries. However, its toxicity and potential occupational and environmental exposure risks create a need for rapid, portable, and visual detection of aniline vapor. Fluorescent-film sensors offer fast responses, intuitive optical readouts, and ease of integration, making them promising platforms for the rapid detection and on-site monitoring of volatile organic compounds (VOCs).

Photoinduced electron transfer (PET) is a common response mechanism in fluorescent sensing systems. Conventional molecular-design strategies for PET-based sensors generally focus on tuning the energy-level alignment between a fluorophore and an analyte to facilitate electron transfer. In solid-state fluorescent films, however, sensing performance depends not only on energetic matching but also on molecular aggregation, film microstructure, and the diffusion and accessibility of analyte molecules to emissive sites. Optimizing energy levels alone is therefore often insufficient to achieve both efficient solid-state emission and a rapid PET response. A central challenge is to preserve strong aggregation-induced emission (AIE) while creating PET-quenching pathways that remain readily accessible to the analyte.

To address this challenge, the research team designed and synthesized 2CB-Py-2Ph, an o-carborane-containing pyrene-based AIE luminogen. Its conjugated pyrene framework serves as an efficient emissive core, while the three-dimensional o-carborane units modulate molecular geometry, excited-state electronic properties, and solid-state aggregation. This design suppresses the excessive packing commonly encountered in planar π-conjugated systems and enables the solid-state emission and sensing performance to be tuned synergistically. The pristine solid powder of 2CB-Py-2Ph exhibited a fluorescence quantum yield of 98.7%, demonstrating its strong intrinsic solid-state emission.

The team then varied the film-forming concentration to regulate the surface microstructure and systematically evaluated how film morphology affected emission and sensing. Although compact films showed higher fluorescence quantum yields, relatively loose films provided more open and accessible diffusion pathways, facilitating interactions between aniline molecules and emissive sites and thereby strengthening the PET-mediated quenching response. The optimized film detected aniline vapor across a concentration range of 900 ppt to 900 ppm, with fluorescence quenching occurring within 5 s. After removal of the aniline vapor, the fluorescence recovered to 90% of its initial intensity within 35 s, and the film displayed good cycling stability. Fluorescence-lifetime measurements, density functional theory (DFT) calculations, and femtosecond transient absorption (fs-TA) spectroscopy collectively supported a dynamic-quenching contribution consistent with a PET-mediated pathway.

This study introduces a design strategy that integrates molecular-structure regulation, aggregation-morphology control, and the coordinated optimization of analyte accessibility and PET response. It highlights the key role of film morphology in balancing solid-state emission efficiency and PET quenching, providing a route toward fluorescent vapor-sensing films that combine high brightness, a broad detection range, rapid response, and good reversibility.

Figure 1. Molecular design, aggregation-induced emission behavior, and film-morphology regulation of 2CB-Py-2Ph.

Figure 2. Response of the 2CB-Py-2Ph film to aniline vapor and the PET-mediated fluorescence-quenching mechanism.

First Author: Li Run, master’s student, Shaanxi Normal University

Correspondence Author: Prof. Peng Haonan, Shaanxi Normal University

Full Text Link: https://doi.org/10.1021/acs.jpcc.6c04279