Efficient fluorescent recognition of carboxylates in aqueous media using facilely electrosynthesized poly(9-aminofluorene)

Journal of Fluorescence, Volume 23, Issue 5, pp 1053-1063. September 2013.

Ge Zhang, Yangping Wen, Yuzhen Li, Jingkun Xu*, Chaoqun Guo, Baoyang Lu, Danhua Zhu.

Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal University, Nanchang, 330013, China &

Key Laboratory of Crop Physiology, Ecology and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang, 330045, China &

Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai, 200433, China.

 

Abstract
A variety of carboxylates were recognized using poly(9-aminofluorene) (P9AF) in the HEPES buffer (pH 7.4), and a proposed possible mechanism was proposed as following. The intermolecular hydrogen bonding interactions resulted in electron transfer between P9AF and carboxylates. P9AF was facilely electrosynthesized in boron trifluoride diethyl etherate and could be used as an efficient fluorescent sensing material for the detection of AcO−. On binding to AcO−, fluorescence quenching of P9AF was demonstrated by a maximum 80 % reduction in the fluorescence intensity, while no obvious fluorescence change could be observed in the presence of some other common anions. Some different carboxylates could be recognized at different levels by P9AF. Substituent groups in carboxylates could affect the intermolecular interaction between carboxylates and P9AF. These could be explained by a possible mechanism that hydrogen bonding was the main way of intermolecular interactions between P9AF and carboxylates, which was further confirmed by absorption spectra monitoring and density functional calculations. The significant advantage of this strategy is that it does not require a prequenching procedure and the polymer can be used directly for analyte detection.

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Efficient fluorescent recognition of carboxylates in aqueous media using facilely electrosynthesized poly(9-aminofluorene)

Fig. 2 Electropolymerization of P9AF and its recognition of carboxylate anions and carboxylates.

Additional Information:

Anions play a major role in many biological processes and in biological structures, such as amino acids, neurotransmitters, organic acids, enzyme substrates, co-factors, and nucleic acids. They are also important components in a variety of industries, such as in the production of fertilisers, in food additives, and in the water supply. Among different kinds of anions, carboxylates are important target species in molecular recognition as they serve important functions in biological systems. With this consideration, water-soluble fluorescent conjugated polymer molecular wires have been widely explored as highly sensitive chemosensors because they can offer a myriad of opportunities for coupling analyte-receptor interactions, as well as nonspecific interactions, into an observed response. The commonly employed reactions for the synthesis of water-soluble conjugated polymers (CPs) are known as palladium-catalyzed coupling reactions (Suzuki, Heck, and Sonogashira), Wessling reaction, topopolymerization reaction, and FeCl3 oxidative polymerization. The electrochemical method is scare, but it has significant advantages of rapid analyses, accuracy, precision, and requiring small amounts of material.

In this study, water-soluble fluorescent P9AF has been successfully synthesized via electrochemical polymerization and was used as an efficient and practical technique for the detection of AcO in the HEPES buffer (pH 7.4). Additionally, this sensor was employed to recognize a variety of carboxylates and a possible mechanism was proposed through UV-vis spectra and DFT calculations. This investigation provides new opportunities and fundamental guidelines for designing CP-based chemo/biosensor. The proposed chemosensor can pave the way for further practical use in biological science and plant physiology.

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