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A novel electrochemical method has been developed, based on a covalent organic framework (COF) and reduced graphene oxide (rGO), to detect fentanyl and alfentanil. COF nanomaterials with chrysanthemum morphology obtained by solvothermal reaction contain rich active sites for electrochemical catalytic reaction, thus improving the detection performance of the designed sensor. Reduced graphene oxide improves the sensor's sensitivity due to enhanced electron transfer. Under optimized experimental conditions, the fabricated electrode presents a linear range of 0.02 to 7.26 μM for alfentanil and 0.1 to 6.54 μM for fentanyl, with detection limits of 6.7 nM and 33 nM, respectively. In addition, the sensor possesses excellent selectivity, outstanding reproducibility, and acceptable stability. The proposed sensor is feasible for the reliable monitoring of fentanyl and alfentanil in human serum samples, with acceptable reliability and high potential in real-world applications. Finally, the electrochemical characteristic fingerprint of fentanyl is investigated by studying the electrochemical behavior of alfentanil and fentanyl on the electrode surface. [ABSTRACT FROM AUTHOR]

In this study, a simple electrochemical sensor based on l -arginine membrane (P-L-arg/GCE) was developed for rapid and sensitive detection of MDMA and MDA. A polyarginine membrane was obtained through one-step direct electropolymerization, which provides more reaction sites for the analyte and improves the sensitivity of the sensor. Following the optimized selection parameters, the MDMA detection range was established at 1.0 × 10−7∼3.5 × 10−5 mol L−1, with a detection limit of 3.3 × 10−8 mol L−1. Similarly, the detection range for MDA was established at 1.0 × 10−7∼5.3 × 10−5 mol L−1 with a detection limit of 3.3 × 10−8 mol L−1. Additionally, the potential oxidation mechanism of MDMA and MDA during the REDOX process was analyzed by cyclic voltammetry. Furthermore, the proposed sensor exhibited superior selectivity, excellent reproducibility, and satisfactory stability. The proposed sensors can be used for reliable monitoring of MDMA or MDA in human urine and hair samples, respectively, and it has acceptable analytical reliability and enormous potential for practical applications. A simple and highly sensitive electrochemical technique has been developed to quantitatively detect MDMA and MDA using P-L-arg/GCE. By means of this sensor, the electrochemical characteristics of both analytes were thoroughly investigated. The sensor demonstrates sound selectivity, repeatability, and long-term stability in the detection of MDMA and MDA. Furthermore, the method can be applied to the determination of MDMA and MDA in human urine and blood samples. [Display omitted] • A high-sensitive sensor for trace detection of ecstasy was designed. • The possible mechanisms of MDMA and MDA were deduced. • The sensor exhibited a wide detection range and low detection limit. • The sensor was successfully applied to the detection of MDMA and MDA in human serum. [ABSTRACT FROM AUTHOR]

Flower-like TpTa-COF was synthesized by the one-step solvothermal method, and a novel electrochemical platform for separation and simultaneous sensitive detection of trace Pb(II) and Cd(II) in surface water was constructed based on TpTa-COF. The proposed sensor has the advantages of low detection limit, high sensitivity, and good stability, and has been successfully applied to the determination of Pb (II) and Cd(II) in two actual water samples. [Display omitted] • Flower-like TpTa-COF was synthesized by the simple solvent method for the first time. • TpTa-COF can provide abundant active sites for trace detection of Pb(II) and Cd(II). • The sensor exhibited a wide detection range and low detection limit. • The detection mechanism of TpTa-COF was explored through XPS and simulation calculation. Heavy metal pollution in aquatic environment poses an enormous risk to ecosystems and human health. In this study, a flowerlike covalent organic framework (TpTa-COF) was synthesized by one-step solvothermal method with 2,4,6-triformylphloroglucinol (Tp) and 4, 4-diamino-tribiphenyl (Ta) as building elements. Then it was used as an effective trap to establish an electrochemical sensing platform for simultaneously sensitive detection of trace Pb(II) and Cd(II) in water. This three-dimensional flower-shaped structure exhibited exceptional adsorption capacity, large surface area, high stability, and all of which enhanced the detection sensitivity of the sensor and facilitated full contact between ions and substrate. The high oxygen content in the structure provided abundant active sites for Pb(II) and Cd(II), further enhancing its electrochemical response. The constructed sensor exhibited a linear response to Pb(II) within the concentration range of 3–60 µg/L under the optimal conditions, with a detection limit of 0.16 µg/L. Similarly, a linear response was observed for Cd(II) in the concentration range of 5–60 µg/L, with a detection limit of 0.29 µg/L. Low detection limits, excellent sensitivity, and strong stability were all features of the suggested approach. It has been successfully employed in determining Pb(II) and Cd(II) concentrations in two actual water samples. XPS, SEM-EDS mapping, and density functional theory calculations confirmed that TpTa-COF interacted with metal ions mainly via coordination with carbonyl oxygen atoms in the structure. Overall, these findings will broaden the applications of COF in the field of chemical analysis. [ABSTRACT FROM AUTHOR]