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A new fluorescence sensing strategy has been developed. Four bimetallic nanoclusters, gold/silver, gold/copper, gold/molybdenum and gold/cobalt, were prepared using bovine serum albumin (BSA) as a reducing and stabilizing agent. The fluorescence properties of four nanoclusters were explored by solid-state UV and XPS. The gold/silver nanoclusters (BSA-Au/Ag NCs) with the best ratiometric fluorescence properties for gallic acid (GA) in plants were selected to realize the sensitive detection of GA. GA affected the conformation of BSA, thereby disrupting the luminescent environment of the nanoclusters, resulting in a pronounced fluorescence quenching at 566 nm. The ratiometric fluorescence signal (I566/I453) was used for trace detection of GA in plants. It has a wide response range of 1.25–40.0 μM and a low detection limit of 45.27 nM. GA was detected at 19.49 μM in the plant extract, and the spiked recoveries ranged from 96.09 to 104.6%. In addition, due to the non-toxic and biocompatible properties of BSA, BSA-Au/Ag NCs have also been validated for fluorescence imaging of plant tissues. It realized the comparison of GA content in different parts of plants and the difference of GA content in plants after abiotic stress. Therefore, the developed strategy offers potential application for the analytical study of active substances in plants. [ABSTRACT FROM AUTHOR]

A synthesis route of using cellulose as the precursor to prepare porous carbon (PC) had been established in this study. The as-prepared PC was introduced as carriers in the synthesis process of porous carbon-molecularly imprinted polymers (PC-MIPs), which greatly improved the absorption capacity of MIPs. Triazine pesticides in corn were extracted with matrix solid-phase dispersion (MSPD) using the PC-MIPs as dispersants and determined by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Under the optimal MSPD condition for extracting six kinds of triazines (simazine, terbutryn, simetryne, prometryne, ametryn, and atrazine), the detection limits were 0.005–0.02 ng g−1, while the precisions were 1.2–5.9%, and the recoveries were 92.6–104.7%. The method has been extensively applied to analyze various corn samples. Atrazine residue (1.2 μg kg−1) was detected in one corn sample, which was lower than the maximum residual limit indicated by the Chinese stated standards (50 μg kg−1). [ABSTRACT FROM AUTHOR]

A fast and economical method has been developed for the preconcentration of the carbamates propoxur, pirimicarb and promecarb by using magnetic molecularly imprinted polymers (m-MIPs). Propoxur was applied as the template for the analytes, and carbon nanotubes as a supporting template. The effects of the amount of magnetic sorbent, shaking time and rate, eluting solution on the extraction efficiency were studied. The processes of adsorption and desorption occur within 25 min, and the m-MIPs can be collected by applying an external magnetic field within 15 s. The m-MIPs were characterized by using FTIR, transmission electron microscopy, and with a vibrating sample magnetometer. The pesticides were quantified by HPLC with UV detection. Recoveries of spiked samples range from 90.5 to 98.6 %, and the lower detection limits range from 9.7 to 12.0 μg kg. The method is selective and convenient. The m-MIPs were successfully applied to enrich and determine the carbamates in spiked homogenates of apples, oranges and pears. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We show that Mn(II)-doped ZnS quantum dots coated with an acrylamide-based molecularly imprinted polymer (MIP-coated QDs) can act as a fluorescent probe for the selective and sensitive detection of the insecticide chlorpyrifos (CPF). The fluorescence of the coated QDs is quenched on loading the MIP with CPF, and the effect is much stronger for the MIP than for the non-imprinted polymer. The MIP-coated QDs were characterized by fluorescence spectrophotometry, X-ray powder diffraction, and scanning electron microscopy. Under optimal conditions, the relative fluorescence intensity of the MIP-coated QDs decreases linearly with the increasing concentration of CPF in the 0.3-60 μmol L concentration range, and the detection limit is 17 nmol L. The method has been used for the determination of CPF in spiked water samples and gave recoveries in the range from 87.1 to 94.5 % with relative standard deviations in the 2.9 to 6.5 % range. The method is simple, safe and inexpensive. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A new dual-emission ratiometric fluorescent probe was synthesized and successfully used for the determination of Malachite Green (MG) in fish farming water. The ratiometric fluorescent probe was successfully composited by sol-gel method using C3N4 and CdTe quantum dots as fluorescent materials combined with mesoporous molecularly imprinted polymers. MG quenches the red fluorescence of the CdTe QDs (with excitation/emission wavelengths at 350/680 nm) while the blue fluorescence of C3N4 (with excitation/emission wavelengths at 350/458 nm) remains unchanged. The change of fluorescence color and fluorescence intensity ratio can be successfully used for quantification of malachite green. In addition, the mesoporous structure has a large surface and good adsorption capacity for malachite green. The normalized intensity of fluorescence increases linearly in the 50–1000 ng·mL−1 MG concentration range, and the detection limit is 10 ng·mL−1. The imprinting factor is 3.2. The nanoprobe was applied to the determination of MG in fish farming water samples. Recoveries and relative standard deviations were 92.5–97.8% and 2.5–6.2%, respectively. [ABSTRACT FROM AUTHOR]