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Analytica Chimica Acta. Volume 805, Pages 87–94. 2013.
Ge Zhang, Yangping Wen, Chaoqun Guo, Jingkun Xu*, Baoyang Lu, Xuemin Duan, Haohua He, Jun Yang.
Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal University, Nanchang 330013, China.
Abstract
A highly selective and sensitive fluorescent chemosensor suitable for practical measurement of palladium ion (Pd2+) in agricultural crops and environment samples has been successfully fabricated using polybenzanthrone (PBA). PBA was facilely electrosynthesized in the mixed electrolyte of acetonitrile and boron trifluoride diethyl etherate. The fluorescence intensity of PBA showed a linear response to Pd2+ in the concentration range of 5 nM–0.12 mM with a detection limit of 0.277 nM and quantification limit of 0.925 nM. Different compounds existing in agricultural crops and environment such as common metal ions, anions, natural amino acids, carbohydrates, and organic acids were used to examine the selectivity of the as-fabricated sensor, and no obvious fluorescence change could be observed in these interferents and their mixtures. A possible mechanism was proposed that the coordination of PBA and Pd2+ enhance the aggregation of polymer chains, which led to a significant quenching of PBA emission, and this was further confirmed by absorption spectra monitoring and transmission electron microscopy. The excellent performance of the proposed sensor and satisfactory results of the Pd2+ determination in practical samples suggested that the PBA-based fluorescent sensor for the determination of Pd2+ will be a good candidate for application in agriculture and environment.
Fig. 3 Electrosyntheses of PBA and its application.
Additional Information:
With the development of industrial, urban, and agricultural modernization and the increasing reliance on agrochemicals in the last several decades, the pollution of heavy metals (HMs) has already caused the serious damage of agricultural ecological environment, especially the damage of agricultural soil and water environment, which not only affects soil quality, water quality, crop growth, agricultural production, farm product quality, and so on, but also harms to human health and life quality through the food chain. Palladium, which is one of HMs and has been widely used in various fields, can harm human health, threaten food security and damage agro-ecosystems. It is very essential for monitoring pollution of palladium ions (Pd2+) in agro-ecosystems and studying the absorption and accumulation of Pd2+ in roots, stems, leaves, and seeds of crops, especially studying the tolerance, detoxification, low absorption, and less enrichment of Pd2+ in crops based on physiological, genetic and molecular aspects. Conjugated polymers (CPs) with a delocalized electronic structure allow for electronic coupling between optoelectronic segments and efficient intra/interchain energy transfer, which have widely applications in optics and chemo/biosensors areas. So far, there are only several reports on fluorescent CPs chemosensors for detection of Pd2+, but they have not yet been applied to the analysis of practical samples. Moreover, the electrosynthesized CPs chemosensors used for the determination of Pd2+ in agricultural crops and environment samples (particularly foodstuffs) has not been reported.
In this work, an efficient and practical fluorescent chemosensor based on polybenzanthrone (PBA) which was obtained by electrochemical synthesis for the detection of Pd2+ in ethanol has been successfully fabricated and the possible mechanism between Pd2+ and PBA has been discussed via transmission electron microscopy (TEM). Moreover, this fluorescent CP-based sensor has excellent sensitivity and selectivity, and was employed to practically detect Pd2+ in agricultural crops and environment samples with satisfactory results. This new design will provide an excellent approach to simply and efficiently detect Pd2+ in practical samples using fluorescent PBA based on an aggregation-induced fluorescence quenching mechanism in an innocuous and environmentally friendly solvent.
