Recently, the Sensing Technology Laboratory of Shanghai Institute of Microsystems and Information Technology, Chinese Academy of Sciences (SIIST) has made important progress in the research of thin-film fluorescent sensors. This work provides an effective strategy for the preparation of excellent thin-film fluorescent sensors, and experimentally verifies and theoretically calculates the synergistic process of fluorescence sensing and gas adsorption.
In recent years, thin-film fluorescent sensors have played a crucial role in the field of gas sensing, especially in the field of sensing of social hazards such as explosives, nerve agents and drugs. Due to their high sensitivity, responsiveness and selectivity, they are one of the most promising technologies for trace substance detection. However, most fluorescent sensitive materials suffer from aggregated fluorescence quenching (ACQ) effect and photobleaching phenomenon, which makes fluorescent sensing materials that meet the requirements of practical applications rare. This greatly limits the application of fluorescent sensitive materials in gas detection, and there is an urgent need to develop new high-performance sensitive materials for gas sensing. Aiming at the problems of poor solid-state fluorescence quantum efficiency and poor photostability faced by thin-film organic fluorescent probe materials, the researchers developed a new type of host-guest thin-film fluorescent gas sensor with high 3S (sensitivity, selectivity, stability) for gas analytes by piggybacking an organic fluorescent guest onto a metal-organic framework (MOF), which provided a flexible method for constructing thin-film fluorescent sensors to satisfy different needs. flexible approach.
In this work, the ACQ molecule Me4BOPHY-1 was used as an encapsulated organic guest, which was embedded into a metal-organic framework ZIF-8 using a simple solid-phase synthesis method, and its fluorescence emission characteristics were adjusted by adjusting the loading ratio.The MOFs (ZIF-8) provided the guest molecule with a The MOFs (ZIF-8) provide various nanocavities for the guest molecules, thus reducing the self-aggregation of fluorescent molecules and effectively overcoming the ACQ effect of Me4BOPHY-1. The solid-state fluorescence quantum efficiency (QY) of the molecule was increased from 0.76% to 19.72% with different ratios of guest molecules. Further, gas-phase identification of diethyl chlorophosphate (DCP), an analog of the nerve agent sarin, was achieved (Figure 1).
Figure 1. Enhancement of fluorescence quantum efficiency and sensing performance of organic fluorescent small molecule probes using host-guest embedded structures.
MEMS cantilever beam adsorption studies have shown that the pre-enrichment of the host-guest embedded MOF sensor for the gas to be measured endowed the probe with excellent gas sensing ability, with a response time of up to 3 s and a detection limit as low as 1.13 ppb. What's more, the caging effect of the MOF improves the selectivity of the analyte, and the Me4BOPHY-1＠ZIF-8 is highly selective to the interfering gas HCl. -8 is significantly weaker in response to the interfering gas HCl, which was unavoidable in the previous literature. Meanwhile, the "caging effect" of the organometallic framework structure also ensures the good photostability and thermal stability of the sensor. The thermal decomposition temperature of the organofluorescent molecules was increased from 200 °C to 527 °C, and the initial fluorescence intensity was maintained even after 4800 s of laser irradiation in the excitation band. In summary, the subject-object embedded design strategy provides a thin-film fluorescent gas sensor with high 3S (sensitivity, selectivity, and stability) for gas analytes, and offers a flexible method for constructing thin-film fluorescent sensors to satisfy different needs. An advanced design strategy for thin-film fluorescent sensors with promising applications in hazardous gas sensing is proposed (Figure 2).
Figure 2. Host-guest embedded MOF sensor realizes high 3S (sensitivity, selectivity, stability) synthesis
The first author of the paper is Zhengqi Shen, a master's student of our institute, and the corresponding authors are Yanyan Fu, a researcher, Jiangong Cheng, and Min Tu, a young researcher. The work was also assisted by Young Researcher Kai Qi, Project Associate Xiuyun Jiang and Prof. Zhiyong Fan of the Hong Kong University of Science and Technology. The related work was supported by the National Key Research and Development Program of the Ministry of Science and Technology (2022YFB3203500, 2021YFB3200800), the National Natural Science Foundation of China (62022085, 62301544, 61831021, 22201289), and the Shanghai Science and Technology Commission (22QA1410800).
