Tungsten disulfide (WS2)/fluorescein ratiometric fluorescent probe for detection of cefixime residues in milk

In this research work, it has been reported a ratiometric fluorescent sensor based on tungsten disulfide quantum dots (WS₂ QDs) and fluorescein for the determination of Cefixime (CEF). When excited by radiation of 400 nm wavelength the probe illustrates dual emissions centered at 460 nm and 510 nm. CEF quenches the fluorescence (FL) intensity of fluorescein (510 nm), while it doesn't affect the FL emission of WS₂ QDs at 460 nm. The change in the ratio of the two peaks (F₄₆₀/F₅₁₀₎ of the prepared sensor (WS₂ QDs/fluorescein) is linearly proportional to the CEF concentration in the range of 200-2.500 ng/mL with a limit of detection (LOD) of 45 ng/mL. Hence, the proposed probe can be successfully used for CEF quantification in the milk samples.

A Green, Economic "Switch-On" Sensor for Cefixime Analysis Based on Black Soya Bean Carbon Quantum Dots

BACKGROUND

Cefixime is a third-generation oral cephalosporin antibiotic widely used to treat bacterial infections. Typical methods for cefixime analysis use expensive instruments or sophisticated experimental procedures, and thus a sensitive and practical method is urgently needed for cefixime detection and analysis.

OBJECTIVE

To develop a sensitive and robust cefixime "switch-on" sensor based on carbon quantum dots (CQDs).

METHODS

In this study, black soya beans were used as an inexpensive carbon source for a "green" synthesis of fluorescent black soya bean (BS)-carbon quantum dots (CQDs). The fluorescence of these particles could be efficiently quenched by Ce(IV)due to the ground state recombination and electron transfer (ET) between Ce(IV)and BS-CQDs. In the presence of cefixime, the ET was interrupted and the fluorescent signal was recovered.

RESULTS/CONCLUSIONS

This method showed high sensitivity and an impressively low detection limit of 169 nM.

HIGHLIGHTS

This low-cost, simple strategy for cefixime detection exhibits excellent stability, selectivity, and sensitivity. Moreover, it was successfully applied for the detection of cefixime in tablets and in a complex biological environment, confirming its great potential utility for drug analysis, biological process research, and clinical research.

A review of the incorporation of QDs and imprinting technology in optical sensors – imprinting methods and sensing responses

This review aims to cover the simultaneous method of using molecularly imprinted technology and quantum dots (QDs) as well as its application in the field of optical sensors.

Recent Advances and Perspectives of Molecularly Imprinted Polymer-Based Fluorescent Sensors in Food and Environment Analysis

Molecular imprinting technology (MIT), also known as molecular template technology, is a new technology involving material chemistry, polymer chemistry, biochemistry, and other multi-disciplinary approaches. This technology is used to realize the unique recognition ability of three-dimensional crosslinked polymers, called the molecularly imprinted polymers (MIPs). MIPs demonstrate a wide range of applicability, good plasticity, stability, and high selectivity, and their internal recognition sites can be selectively combined with template molecules to achieve selective recognition. A molecularly imprinted fluorescence sensor (MIFs) incorporates fluorescent materials (fluorescein or fluorescent nanoparticles) into a molecularly imprinted polymer synthesis system and transforms the binding sites between target molecules and molecularly imprinted materials into readable fluorescence signals. This sensor demonstrates the advantages of high sensitivity and selectivity of fluorescence detection. Molecularly imprinted materials demonstrate considerable research significance and broad application prospects. They are a research hotspot in the field of food and environment safety sensing analysis. In this study, the progress in the construction and application of MIFs was reviewed with emphasis on the preparation principle, detection methods, and molecular recognition mechanism. The applications of MIFs in food and environment safety detection in recent years were summarized, and the research trends and development prospects of MIFs were discussed.

Sensitive biosensing of organophosphate pesticides using enzyme mimics of magnetic ZIF-8

Development of a sensitive detection method for the reliable screening of widely used organophosphorus (OP) toxins is a crucial request to control their side-effects. Herein, a novel fluorometric assay based on the acetylcholinesterase (AChE) inhibited enzymatic activity and the new peroxidase-like Fe₃O₄ nanoparticles@ZIF-8 composite (Fe₃O₄ NPs@ZIF-8) was developed for the determination of OPs. Magnetic Fe₃O₄ NPs were encapsulated into ZIF-8 and the high mimetic activity of produced composite was assessed on the oxidation of substrates. This observation was applied to the rapid detection of diazinon as a model OP compound. The sensing tool contains AChE and choline oxidase (CHO) enzymes, peroxidase colorimetric or fluorometric substrate, and Fe₃O₄ NPs@ZIF-8 as the catalyst. In the presence of mimic Fe₃O₄ NPs@ZIF-8, the generated H₂O₂ from the enzymatic reactions of acetylcholine is decomposed to hydroxyl radicals. The radicals oxidize the peroxidase substrates to generate a detectable signal. However, due to the inhibition effect of OPs on the enzymatic activity of AChE, lower H₂O₂ amounts are produced in the presence of diazinon. Using the fluorometric detection system, the generated signal is decreased proportionally by increasing diazinon concentration in the range of 0.5-500 nM. The limit of detection was obtained 0.2 nM. Consequently, the usage of high performance peroxidase-mimic Fe₃O₄ NPs@ZIF-8 provided a sensitive bio-assay with a potential to be applied as screening tool for toxic OP compounds. The developed assay was successfully applied for the determination of diazinon in water and fruit juices.

Detection of trace leucomalachite green with a nanoprobe of CdTe quantum dots coated with molecularly imprinted silica via synchronous fluorescence quenching

A novel fluorescence nanoprobe using CdTe quantum dots as signal sources coated with a molecularly imprinted polymer was synthesized by a reverse microemulsion method.

Rapid synthesis of CdS nanowire mesh via a simplistic wet chemical route and its NO2 gas sensing properties

In this report, 1-D interconnected CdS nanowires were prepared rapidly via a wet chemical route at relatively low temperature, using cadmium sulphate, thiourea and ammonia as raw materials.

Chemiluminescence determination of furazolidone in poultry tissues and water samples after selective solid phase microextraction using magnetic molecularly imprinted polymers

For the first time, a selective extraction method combined with chemiluminescence was developed for the determination of FZD in various samples.