A fluorescence microsphere suspension array technique has been developed as a promising tool for the molecular detection of Listeria monocytogene (LM), which is a dangerous food borne pathogen that can cause severe food intoxication in both humans and animals. In such a technique, fluorescent microspheres as the key matrix for detection are often decorated with neutral organic dyes, which usually suffer from instability, easy photobleaching and loss from the matrix. Herein, we design and synthesize a new organic–inorganic hybrid POM–pyrene compound [N(C4H9)4]2[V6O13{(OCH2)3CNH–CH2–C16H9}2] (1), which is employed as a negatively-charged fluorescent material to prepare a new class of fluorescent microspheres by a layer-by-layer electrostatic self-assembly method. As a result, such POM–pyrene-decorated fluorescent microspheres possess obvious luminescence properties, superior photo-stability and long-term stability. Therefore, the POM–pyrene-decorated fluorescent microspheres are conjugated by monoclonal anti-LM antibodies, and introduced into the fluorescence microsphere-based suspension immunoassay system for the detection of LM in food, which exhibits a high sensitivity. The lowest limit of detection (LOD) of LM in artificially contaminated meat is down to 6 CFU g−1 without cross-reactivity with other pathogens. Furthermore, the suspension immunoassay based on PS@POM–pyrene microspheres shows excellent specificity to LM, good repeatability and high efficiency in contrast to the conventional culture-based method.
Yan Xin,Yang Jianming,Zhang Hexin,Yoon Keun-Byoung,Chen Min
The single-sited metallocene catalyst has attracted significant attention due to its high activity and application in olefin polymerization industry. In this work, we introduced a strategy of in situ modification of metallocene catalyst with pyrene through π–π stacking to study the effect in olefin polymerization. After activated by MMAO, the pyrene-modified metallocene catalyst exhibited high activities (up to 1333 kg mol −1 h −1 ) in ethylene polymerization, which was 1.9 times higher than that of the pyrene free catalyst system. This could be because the electron-donating ability of cyclopentene to the transition metal was enhanced through π–π interaction of pyrene with cyclopentene. The copolymerization of ethylene and 1-hexene was also studied. The pyrene-modified metallocene catalyst system performs with higher activity in the copolymerization with a lower monomer incorporation ratio. Density functional theory (DFT) calculations indicated the formation of π–π interaction between the Zr center with pyrene molecule leading to the increase in steric hindrance and electron density. Graphical abstract
Capturing and detecting Fe 3+ ions in aqueous solution is of great significance in biological systems as well as the water treatment industry. Herein, pyrene-modified cellulose nanocrystal (CNC-1-Pyr) acting as a fluorescent probe was prepared by a one-step esterification reaction, which shows geometry relaxation under UV-light excitation. Experiments and density functional theory-based simulations revealed that the structural geometry relaxation is controlled by the electron excitation and fluorescence emission. The S1 state of CNC-1-Pyr provides a conformation match for coordination with Fe 3+ under the excitation of UV light, facilitating the detecting and capturing of Fe 3+ efficiently.
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