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This work presents an electrochemical device based on a composite modification of amine functionalized Zr(IV) metal–organic framework (UiO-66-NH2) and multi-walled carbon nanotubes (MWCNTs) for voltammetry determination of cadmium ions (Cd2+). The UiO-66-NH2@MWCNTs composites were prepared by one-pot hydrothermal reaction. The prepared sensor performs excellent performance, which was attributed to the synergism between UiO-66-NH2 with a special octahedral structure and enlarged surface area and MWCNTs with outstanding conductivity. Under optimal experiment condition, the fabricated sensor showed good linear relationship from 0.5 to 170 μg/L, with a detection limit of 0.2 μg/L. Finally, the sensor was successfully applied to detect Cd2+ in meat samples (N = 21) with relative standard deviation (RSD) lower than 4.5% and recovery of 95.1–107.5%, and the results were compared with certified method, there was no statistical significance difference between the developed sensor and certified method at a 95% confidence level.

A novel aptamer-modified Copper @ Gold nanoclusters (apt-Cu@Au NCs) based ratiometric fluorescent probe was developed for mercury ions (Hg2+) determination in Porphyra. The apt-Cu@Au NCs were well dispersed in solution without Hg2+ but combined together for the formation of thymidine–Hg–thymidine structure with the addition of Hg2+, which further caused the changes in their fluorescence intensities owing to fluorescence resonance energy transfer. Along with that, the changes in fluorescent colors are visible to the naked eye. Accordingly, Hg2+ were determined ranging from 0.1 to 9.0 μM by fluorescence analysis with the detection limit of 4.92 nM. Moreover, a homemade device utilizing smartphone and microfluidic chip was designed for colorimetric determination of Hg2+ ranging from 0.5 to 7.0 μM with good portability and usefulness. The proposed methods were used for Hg2+ detection in Porphyra with the recoveries of 101.83–114.00%, suggesting the considerable potential for evaluating Hg2+ levels in aquatic products.

A dual-mode fluorescence/colorimetric sensor based on carbon quantum dots (CQDs) and gold nanoparticles (GNPs) was developed for visual detection of malathion in cabbage. The CQDs-GNPs nanocomposite exhibited emission wavelength at 527 nm and absorption wavelength at 524 nm. The fluorescence intensity increased and absorption decreased with addition of malathion. Fluorescence and colorimetric calibration curves were established based on fluorescence intensity (R2 = 0.9914) and absorbance (R2 = 0.9608) in the range of 1 × 10−9–1 × 10−2 M, respectively. Furthermore, fluorescence and colorimetric standard arrays were prepared for visual detection of malathion according to the change of fluorescence brightness and color. Finally, the approximate concentrations of malathion in cabbage samples were estimated by the standard arrays and naked eyes. The calibration curves were used for accurate detection in cabbage samples with recoveries of 89.9%–103.4% (fluorescence) and 88.7%–107.6% (colorimetric). The established sensor for visual malathion detection in cabbage was accurate with strong application potential, especially for rapid screening.

A ratiometric fluorescence sensor system is proposed for detecting bis(2-ethylhexyl) phthalate (DEHP) in pork, which is based on aptamer recognition with molybdenum disulfide quantum dots and cadmium telluride quantum dots (MoS2 QDs/CdTe-Apta). Two signals exist in the system, among which the response signal is transmitted by CdTe-Apta. The amide condensation between aptamers and CdTe QDs shortens the distance between CdTe QDs and DEHP, thus quenching the fluorescence of CdTe QDs, possibly through a photoinduced electron transfer mechanism. The MoS2 QDs deliver the self-calibration signal, and the fluorescence of MoS2 QDs remains almost constant when co-existing with DEHP. Linearity (R2 = 0.9536) was established for the DEHP concentration range 0.005–3.0 mg·L−1, with a limit of detection of 0.21 μg·L−1. The system was successfully applied in the determination of DEHP in pork. The system has potential for the quantitative determination of DEHP in practical applications.

A novel ratiometric fluorescence probe was proposed for detecting lead (II) ions (Pb2+) in porphyra, the approach was based on copper nanoclusters and nitrogen-doped carbon quantum dots (CuNCs-CNQDs). In this probe, the CuNCs delivered the response signal, the fluorescence of which was enhanced by Pb2+ due to the aggregation-induced emission enhancement (AIEE) between Pb2+ and CuNCs. The CNQDs provided the self-calibration signal, whose fluorescence remained almost unchanged in coexistence with Pb2+. According to the change of fluorescence intensity ratio between the fluorophores, CuNCs–CNQDs nanohybrid was used as ratiometric probes for the sensitive detection of Pb2+ in the range of 0.010–2.5 mg L−1, with a detection limit of 0.0031 mg L−1. Finally, the probe was successfully applied to detect Pb2+ in porphyra with relative standard deviations (RSDs) lower than 5%. This study provides a straightforward, stable, and sensitive approach for detecting Pb2+ in porphyra.

A simple, rapid, and effective method based on salting-out extraction and LC-MS/MS techniques was developed for the determination of 39 plant growth regulator (PGR) residues in two of the most common root and rhizome Chinese herbs, Codonopsis Radix (Dangshen) and Notoginseng Radix et Rhizoma (Sanqi). The extraction process was performed with acetonitrile-water (5:1) and citrate buffer extraction salt. The performance of the method was validated in accordance with the analytical quality control criteria of SANTE/11813/2017 guidelines. Analyte recoveries of 79.49–109.41% (Dangshen) and 80.17–102.81% (Sanqi) were achieved. The limit of quantifications (LOQs) were determined with the consideration of accuracy and precision. LOQs were lower than the lowest residue limits in EU pesticide regulation (10 µg/kg) for most PGRs. Moreover, the method was successfully applied in the analysis of 35 batches of Dangshen, and 60 batches of Sanqi products. The concentration of eleven PGRs were determined in analyzed samples.