Research Progress of Aggregation-Caused Quenching (ACQ) to Aggregation-Induced Emission (AIE) Transformation Based on Organic Small Molecules

Reviewing the evolutive ACQ-to-AIE transformation of photosensitizers for phototheranostics

Photodynamic therapy (PDT) represents an emerging noninvasive treatment technique for cancers and various nonmalignant diseases, including infections. During the process of PDT, the physical and chemical properties of photosensitizers (PSs) critically determine the effectiveness of PDT. Traditional PSs have made great progress in clinical applications. One of the challenges is that traditional PSs suffer from aggregation-caused quenching (ACQ) due to their discotic structures. Recently, aggregation-induced emission PSs (AIE-PSs) with a twisted propeller-shaped conformation have been widely concerned because of high reactive oxygen species (ROS) generation efficiency, strong fluorescence efficiency, and resistance to photobleaching. However, AIE-PSs also have some disadvantages, such as short absorption wavelengths and insufficient molar absorption coefficient. When the advantages and disadvantages of AIE-PSs and ACQ-PSs are complementary, combining ACQ-PSs and AIE-PSs is a "win-to-win" strategy. As far as we know, the conversion of traditional representative ACQ-PSs to AIE-PSs for phototheranostics has not been reviewed. In the review, we summarize the recent progress on the ACQ-to-AIE transformation of PSs and the strategies to achieve desirable theranostic applications. The review would be helpful to design more efficient ACQ-AIE-PSs in the future and to accelerate the development and clinical application of PDT.

Design and Preparation of Ethylene Fluorescence Probes Based on Arylolefins and Grubbs Catalysts

To detect the plant hormone ethylene, three arylolefins were employed to react with ethylene based on olefin metathesis. In this study, three fluorescence probes were successfully prepared using a first-generation Grubbs catalyst (G-1) and arylolefin with terminal vinyl groups. The probes were characterized using various techniques, including UV-vis, fluorescence, FT-IR, ¹H NMR, ¹³C NMR, and ³¹P NMR spectroscopies and HRMS. The probes exhibited an emission maximum at 394 nm and showed excellent ethylene response. The detection limits for the probes were calculated to be 0.128, 0.074, and 0.188 μL/mL (3σ), respectively, based on fluorescence stimulation by ethylene gas. Additionally, the YGTZ-2 probe was used to detect ethylene gas during the storage process of tomatoes. This work expands the application of arylolefin in ethylene detection and provides a foundation for the development of economic, rapid, and convenient photosensitive sensors for ethylene in the future.