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In this work, nitrogen doped carbon dots (N-CDs) derived from kiwi seeds, white sesame seeds, and black sesame seeds were prepared by a simple, feasible and green route. Then a novel nitrite electrochemical sensor was successfully constructed. The morphology and composition of N-CDs were characterized by Field emission transmission electron microscopy, Fourier transform infrared spectra, Raman spectra and electrochemical methods. The particle size of the as-prepared N-CDs from the three kinds of natural seeds were in the range of 1.4 ∼ 4.9 nm, 1.4 ∼ 4.6 nm, and 1.2 ∼ 4.7 nm, respectively. Moreover, these N-CDs nanomaterials exhibited excellent electrocatalytic performances for nitrite sensing with a detection limit of 0.23 μM (S/N = 3) by electrochemical methods. Additionally, the stability, anti-interference ability and real sample analysis of the sensors had been evaluated. Finally, the electrochemical sensor was successfully applied for nitrite determination in real samples (ham sausages). Based on the present study, more natural seeds could be expected as preferred candidates for N-CDs synthesis, and a general platform of novel electrochemical sensors for nitrite detection is provided.

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In this work, cobalt-nickel oxide nanorods decorated molybdenum disulfide nanosheets (NiCo 2 O 4 -MoS 2 ) nanocomposite material was synthesized by a simple ionothermal synthesis method in deep eutectic solvents, after which, a glucose sensor based on the (NiCo 2 O 4 -MoS 2 ) nanocomposites was constructed. The nanocomposite material was characterized by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). At the potential of +0.5823 V (vs. NHE), the electrochemical response of the sensor was linear with the glucose concentration ranging from 0.70 μM to 13.78 mM and the sensor exhibited excellent electrocatalytic performance toward the oxidation of glucose with a low detection limit of 0.23 μM (S/N = 3). In addition, it also has a good selectivity, stability, repeatability and reproducibility. Furthermore, the sensor was used to detect the glucose in honey and red wine. All of these suggested that the NiCo 2 O 4 -MoS 2 nanocomposites might be promising candidate nanomaterials for constructing electrochemical sensors to detect glucose.

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Patulin (PAT), a type of mycotoxin existing in foodstuffs, is harmful to food safety and human health. Thus, it is necessary to develop sensitive, selective and reliable analytical methods for PAT detection. In this study, a sensitive aptasensor based on a dual-signaling strategy was fabricated, in which a methylene-blue-labeled aptamer and ferrocene monocarboxylic acid in the electrolyte acted as a dual signal, for monitoring PAT. To improve the sensitivity of the aptasensor, an in-plane gold nanoparticles–black phosphorus heterostructure (AuNPs-BPNS) was synthesized for signal amplification. Due to the combination of AuNPs-BPNS nanocomposites and the dual-signaling strategy, the proposed aptasensor has a good analytical performance for PAT detection with the broad linear range of 0.1 nM–100.0 μM and the low detection limit of 0.043 nM. Moreover, the aptasensor was successfully employed for real sample detection, such as apple, pear and tomato. It is expected that BPNS-based nanomaterials hold great promise for developing novel aptasensors and may provide a sensing platform for food safety monitoring.

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