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Rapid and sensitive determination of pesticide residues in fruits and vegetables is critical for human health and ecosystems. This paper used an Ag-modified CuO sphere-cavity array (CuO@Ag) electrode as a thiram SERS/electrochemical dual readout detection platform. Numerous Raman "hotspots" generated by uniformly distributed silver nanoparticles, charge transfer at the CuO@Ag interface, and the formation of Ag-thiram complexes contribute to the significant enhancement of this SERS substrate, which results in excellent SERS performance with an enhancement factor up to 1.42 × 106. When using SERS as the readout technique, the linear range of the substrate for thiram detection was 0.05–20 nM with a detection limit (LOD) of up to 0.0067 nM. Meanwhile, a correlation between the value of change in current density and thiram concentration was established due to the formation of stable complexes of thiram with Cu2+ generated at specific potentials. The linear range of electrochemical detection was 0.05–20.0 μM, and the detection limit was 0.0167 μM. The newly devised dual-readout sensor offers notable sensitivity and stability. The two signal readout methods complement each other in terms of linear range and detection limit, making it a convenient tool for assessing thiram residue levels in agro-food. At the same time, the combination of commercially available portable equipment makes on-site monitoring possible. Ag-modified CuO cavity arrays have been established as SERS-electrochemical dual-signal platforms for thiram detection. [Display omitted] • CuO@Ag cavity arrays were used as SERS/electrochemical dual-signal sensors. • The EM and CT synergistic effect endow CuO@Ag with excellent SERS performance. • The highly ordered array structure ensures excellent SERS signal reproducibility. • The complex between the electrode and thiram enhances the electrochemical response. • The sensor demonstrated the feasibility of detecting thiram in real samples. [ABSTRACT FROM AUTHOR]

Metronidazole (MNZ) is non-biodegradable and highly soluble in water, it is easy to accumulate in the aquatic environment, which has toxic effects in clinical applications such as causing peripheral neuritis, cardiogenic shock and pseudomembranous colitis. In this paper, Co/NC@w-NiSO 4 ·NiS 2 nanospheres were successfully constructed by coating w-NiSO 4 ·NiS 2 on the surface of ZIF-67 as the growth substrate via hydrothermal method and subsequent calcination for electrochemical detection of metronidazole (MNZ). The nanostructure and composition of the materials were confirmed by SEM, TEM, FT-IR and XPS. The sensitivity of Co/NC@w-NiSO 4 ·NiS 2 sensor for MNZ detection is 1977.14 μA/(mM·cm2); the limit of detection (LOD) is as low as 0.009 μM and the linear range is 1 ∼ 200 and 200 ∼ 1000 μM. Moreover, the modified sensor can resist the interference from many traditional living substances, and has good reproducibility and stability. High catalytic activity requires effective molecular transport and exposure of active sites. The successful construction of Co/NC@w-NiSO 4 ·NiS 2 nanostructure promotes the dispersion of materials and the migration of reactants on the electrode surface, and the w-NiSO 4 ·NiS 2 coating on the irregular particles of ZIF-67-derived cobalt/nitrogen-doped carbon suppressed the stacking of the w-NiSO 4 ·NiS 2 nanosheets to expose more catalytic sites. These factors are conducive to increasing the catalytic activity of the modified sensor for highly sensitive MNZ detection and ensuring the activity of catalyst in multiple catalytic cycles. [Display omitted] • Co/NC@w-NiSO 4 ·NiS 2 composite was synthesized via hydrothermal method and pyrolysis. • The composite suppressed the stacking of nanosheets to expose more catalytic sites. • The sensitivity of electrochemical sensor is 1977.14 μA/(mM·cm2). • The electrochemical sensor was used for MNZ analysis in human blood plasma samples. [ABSTRACT FROM AUTHOR]

• Perchlorates in environment rise concerns, sensitive determination techniques needed. • Analysis and critical evaluation of published electrochemical perchlorate sensors. • Voltammetric methods superior over „classical" potentiometric ISE. • Electrochemical impedance and capacitance sensors - the lowest detection limit. • Capability of electrochemical sensors to replace ion/mass chromatography shown. Growing concerns about adverse effects of perchlorate (ClO 4 −) together with its relatively frequent occurrence in the environment demand sensitive analytical methods. It is also anticipated that ClO 4 − sensors will find their application in future extra-terrestrial missions. Ion chromatography (IC) and mass spectroscopy (MS) provide sufficiently low detection limit (LOD) but lack transportability and field analysis possibility that are provided by most electrochemical analytical methods. On the other side, commercially available potentiometric ion-selective electrodes (ISEs) cannot compete with IC or MS in terms of sensitivity. To answer the question whether (and how) such drawback can be overcome, in this paper electrochemical methods of ClO 4 − determination are introduced and evaluated. Starting with potentiometric ISEs which can theoretically reach LOD suitable for assessment of WHO-set limits of ClO 4 −, it is further shown that ISEs operating in voltammetric mode are superior in terms of sensitivity. Next section covers impedimetric and capacitance ClO 4 − sensors, concluding that they can reach detection limits of IC or MS while retaining their advantages. In further sections related issues are discussed including biosensing or direct electrochemical reduction of perchlorate as well as diversity of (nano)materials applicable for perchlorate sensors preparation. This critical review thus shows that electrochemical ClO 4 − sensors can reach sensitivity of standard methods while retaining their portability and ease of operation. [ABSTRACT FROM AUTHOR]

A properly designed sensing interface is crucial for the accurate and sensitive detection of biologically active molecules. Single-atom nanozymes from transition metal and nitrogen-doped carbon materials (M-N-C) have caught attention owing to their large surface area and strong bionic enzyme activity. Herein, a three-dimensional layered electrochemical electrode consisting of a Co–N–C nanoenzyme embedded in a reduced graphene oxide aerogel was prepared for the detection of hydrogen peroxide (H 2 O 2), dopamine (DA) and uric acid (UA). Due to its unique three-dimensional layered structure, rGA has excellent electrical conductivity and high material loading and is used to enhance the electrocatalytic performance of Co–N–C. The combination of single-atom nanozymes and electrochemical detection shows unique advantages in catalytic activity and selectivity. The limit of detection and detection range are 0.74 μM and 3–2991 μM respectively for H 2 O 2. Furthermore, it has been successfully implemented for the in-situ detection of H 2 O 2 in living cells. In addition, their simultaneous detection is also realized by the sensors for DA and UA. And it can accurately capture the signal of UA and DA in the urine. Meanwhile, the electrode displays satisfactory stability and repeatability. Therefore, this paper provides a new detection strategy for a variety of bioactive molecules, showing great potential in cell biology, pathophysiology and diagnostics. A novel electrochemical sensor based on single-atom nanozymes Co–N–C for bioactive molecules detection. [Display omitted] • Single-atom nanozymes Co–N–C exhibited peroxidase activity. • Co–N–C/rGA was used to detect H 2 O 2 in living cells, and successfully realized the simultaneous detection of DA and UA. • It provides a new method for the detection of bioactive molecules. [ABSTRACT FROM AUTHOR]