Yijian Zhao,Xiaohan Zheng,Qinzhi Wang,Taotao Zhe,Yaowen Bai,Tong Bu,Meng Zhang,Li Wang
Various pesticides employed in modern agriculture result in large amounts of pesticide residues in agricultural production, greatly threatening human health. Herein, we report a facile approach to fabricate a reduced graphene oxide/cyclodextrin modified glassy carbon electrode (rGO/CD/GCE) for the sensitive electrochemical sensing of imidacloprid (IDP). Three different modified electrodes using CDs ( α -, β -, γ -CD) were fabricated, and their electrochemical performance was further studied. The results demonstrate that α -CD possesses the best signal amplification for IDP. Compared with wet-chemical synthesis of rGO/CDs (W-rGO/CDs), the electrochemical synthesis of rGO/CDs (E-rGO/CDs) produced sensors that showed better performance for IDP sensing. Taking advantage of prepared E-rGO/ α -CD nanocomposite, the fabricated sensor offered a low detection limit (0.02 μM) with a wider linear range (0.5–40 μM) and long-term stability. The new sensor was successfully applied for the detection of IDP in brown rice, providing a new technique for efficient and convenient monitoring of pesticide residues in food.
Mercury (Hg 2+ ) is one of the most toxic heavy metals in farm products, so rapid detection of trace Hg 2+ has always been sought after with high interest. Herein, we report a biosensor to specifically recognize Hg 2+ in leaching solutions of brown rice flour. This sensor is simple and of low cost, with a very short assay time of 30 s. Another merit is the ultra-low limit of detection (LOD) at fM level. In addition, the specific aptamer probe realizes a good selectivity above 10 5 : 1 against the interferences. This sensor is developed based on an aptamer-modified gold electrode array (GEA) for capacitive sensing. Alternating current electrothermal (ACET) enrichment is induced during the AC capacitance acquirement. Thus, the enrichment and detection are coupled as a single step, and pre-concentration is needless. Owing to the sensing mechanism of solid–liquid interfacial capacitance and ACET enrichment, Hg 2+ level can be sensitively and rapidly reflected. Also, the sensor has a wide linear range from 1 fM to 0.1 nM and a shelf life of 15 days. This biosensor shows advantages on overall performance, enabling easy-to-operate, real-time, and large-scale Hg 2+ detection in farm products.
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