Room-temperature ultrasonic-assisted self-assembled synthesis of silkworm cocoon-like COFs@GCNTs composite for sensitive detection of diuron in food samples

Better Together: Synergistic Enhancement of AuNPs and Bifunctional Monomers in a Dual-Channel Molecularly Imprinting Electrochemical Sensor for Simultaneous Detection of Diuron and Thidiazuron

The combination of diuron (DU) and thidiazuron (TDZ) is commonly used in cotton production for its excellent adaptability to low temperatures, which may lead to increased crop and soil pollution. The simultaneous detection of DU and TDZ poses significant challenges due to their weak and overlapping signals, along with an unclear electrochemical detection mechanism for TDZ. This study developed a dual-channel multifunctional molecularly imprinted electrochemical (MMIP-EC) sensing platform by optimizing the substrate material and MIP layer for high performance. First, amino-functionalized graphene-based poly(pyrrole)-poly(3,4-ethylenedioxythiophene) (NH2-rGO/PPy-PEDOT) with high conductivity was synthesized as the substrate. Subsequently, MMIPs were prepared in one step using electropolymerization by introducing chloroauric acid (HAuCl4) and bifunctional monomers (dopamine and thiophene). This method not only enhanced specific binding capacity of the MMIP layer but also amplified the signal through the synergistic effect of reduced AuNPs and bifunctional monomers. Furthermore, two independent modules (MMIP-DU and MMIP-TDZ) were integrated into a dual-channel EC platform for simultaneous transmission of DU and TDZ responses to separate windows. Finally, based on high-performance liquid chromatography-mass spectrometry (HPLC-MS) and electrochemical kinetics studies, it was speculated that the electrochemical oxidation of TDZ via the carbonylation of a secondary amine under strongly acidic conditions, followed by hydrolysis to form a carboxyl group, reveals the electrochemical oxidation mechanism of TDZ. The developed sensor exhibited excellent performance in selectivity and sensitivity, with low detection limits of 26.6 pg/mL (DU) and 39.2 pg/mL (TDZ). In conclusion, this sensing platform presents a novel perspective for the cost-effective and highly efficient detection of diverse environmental pollutants.

Room-temperature fabrication of zeolitic imidazolate framework-8 nanoparticles combined with graphitized and carbonylated carbon nanotubes networks for the ultrasensitive gallic acid electrochemical detection

Gallic acid (GA) has important application value in several fields of foods, medicines, and chemical engineering. However, the excessive intake of GA may cause gastrointestinal discomfort and nerve damage. Herein, an economical room-temperature fabrication strategy was reported for the preparation of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles combined with graphitized and carbonylated carbon nanotubes (GCMCN) networks, which were used to achieve the ultrasensitive electrochemical detection of GA. The GCMCN@ZIF-8 nanocomposite modified electrode realized an accurate and rapid analysis of GA (Linear concentration range: 0.1-20 μM, LOD: 4.77 nM). GCMCN networks with graphitization and carboxylation boosted the electrical conductivity of electrode modification layer and enhanced the electrochemical interface area between sensing electrode and electrolyte. ZIF-8 nanoparticles with more active interaction sites and high porosity possessed high adsorption capacity for GA molecules. The fabricated electrochemical sensing platform exhibited good GA quantitative analysis property in food samples (Recovery: 93.88-106.73 %, RSD: 1.04-3.73).

Synchronous activation of praseodymium vanadate/graphitic carbon nitride nanocomposite: A promising electrode material for detection of flavonoid- Quercetin

Flavonoids or phenolic compounds are part of the daily intake of every human being. Though they are positive traders for metabolism, excessive intakes bring about detrimental impacts on human health. Herein, the anti-cancer capacitive nature quercetin (Qc) was electrochemically detected through the rare earth metal-based sphere like praseodymium vanadate (PrVO4) entrapped graphitic carbon nitride (g-CN) as electrode modifiers. The nanocomposite was prepared by the one-pot hydrothermal method and characterized by phase compositional and morphology-based techniques. The existing synergistic nature between the PrV@g-CN (praseodymium vanadate@graphitic carbon nitride) makes them have an enhanced electrochemical response towards the Qc than the individual material. The obtained cyclic voltammogram and differential pulse voltammogram profile show one major oxidation peak which is attributed to the conversion of quercetin to quercetin-o-quinone. The PrV@g-CN/GCE (GCE- glassy carbon electrode) shows a good electrochemical active surface area (A = 110 cm2) and linear range between 0.05 and 252.00 μM with a LOD (limit of detection) of 0.002 µM. Moreover, the PrV@g-CN/GCE exhibits good current retention (94.76 %) around 14 days and appreciable repeatability (RSD- 0.5 %) and reproducibility (RSD- 1.3 %) towards the Qc. The real-time implementation of the proposed sensor exhibits a good recovery range towards the black tea (95.00-98.10 %) and green tea (97.80-99.60 %).

Advances of Electrochemical and Electrochemiluminescent Sensors Based on Covalent Organic Frameworks

Covalent organic frameworks (COFs), a rapidly developing category of crystalline conjugated organic polymers, possess highly ordered structures, large specific surface areas, stable chemical properties, and tunable pore microenvironments. Since the first report of boroxine/boronate ester-linked COFs in 2005, COFs have rapidly gained popularity, showing important application prospects in various fields, such as sensing, catalysis, separation, and energy storage. Among them, COFs-based electrochemical (EC) sensors with upgraded analytical performance are arousing extensive interest. In this review, therefore, we summarize the basic properties and the general synthesis methods of COFs used in the field of electroanalytical chemistry, with special emphasis on their usages in the fabrication of chemical sensors, ions sensors, immunosensors, and aptasensors. Notably, the emerged COFs in the electrochemiluminescence (ECL) realm are thoroughly covered along with their preliminary applications. Additionally, final conclusions on state-of-the-art COFs are provided in terms of EC and ECL sensors, as well as challenges and prospects for extending and improving the research and applications of COFs in electroanalytical chemistry.