Qingfeng Yang

One-pot synthesis of multifunctional magnetic ferrite–MoS2–carbon dot nanohybrid adsorbent for efficient Pb(II) removal

Herein, we demonstrate a one-pot solvothermal synthetic method for fabricating MFe2O4 (M = Mn, Co)–MoS2–carbon dot (CD) nanohybrid composites (MnFMC, CoFMC) with excellent Pb(II) removal ability. Detailed characterization through SEM, XRD, UV-vis spectra, fluorescence spectra and VSM confirmed the formation of the nanohybrid composites. The adsorption behavior of the as-prepared nanohybrids was systematically studied using kinetic and equilibrium experiments, and the adsorption mechanism was further revealed using XPS and FTIR. Taking advantage of the cation substitution of abundant functional groups on the surface of CDs and MFe2O4 nanoparticles, as well as the large surface of available MoS2 for enhancing the sequestration of target metal-pollutants, the as-prepared composites exhibit high adsorption performances (588.24 mg g−1 for MnFMC and 660.67 mg g−1 for CoFMC) and show preferential Pb(II) sorption behavior with a high level concentration of competing cations (Ca(II)/Mg(II)). Moreover, these nanohybrid adsorbents exhibit excellent reusability, lower the effluent Pb(II) contents down to the ppb level, which satisfies the drinking water standard recommended by the World Health Organization, and are promising candidates for water purification.

High effective adsorption/removal of illegal food dyes from contaminated aqueous solution by Zr-MOFs (UiO-67)

UiO-67, a bifunctional adsorbent, was successfully applied to remove illegal food dyes (Congo red and Malachite green) from aqueous solution. The relevant adsorption conditions were optimized: pH 6, 120 min for contact time, and 10.0 mg L-1 adsorbent dose for Congo red. Adsorption behavior of UiO-67 exhibits a better fitting to pseudo-second-order kinetic model and Langmuir model. Moreover, the maximum adsorption capacities of Congo red (1236.9 mg g-1) and Malachite green (357.3 mg g-1) are higher than that of the most reported adsorbents. Thermodynamic analysis reveals that adsorption processes are spontaneous and endothermic in nature. Powder X-ray diffraction patterns, Fourier-transform infrared spectra and the X-ray photoelectron spectroscopy analysis indicates Zr-OH groups have positive influence on binding of target molecules. Whats more, UiO-67 could be reused without significant loss of its capacity after seven cycles. These results prefigure the promising potentials of UiO-67 in food safety risk management.

The simultaneous detection and removal of organophosphorus pesticides by a novel Zr-MOF based smart adsorbent

Developing a smart adsorbent that can efficiently detect and remove toxic organophosphorus pesticides is important but still a great challenge. Here, a novel MOF-based smart adsorbent, Fe3O4@SiO2@UiO-67, was successfully fabricated via a versatile layer by layer assembly strategy and applied to the simultaneous selective recognition, detection and removal of glyphosate. The prepared smart adsorbent contains Zr–OH groups with high affinity for phosphate groups, endowing it with selective recognition and a higher adsorption capacity for glyphosate. Moreover, combining it with glyphosate leads to changes in the fluorescence intensity of the smart adsorbent, and incorporating silica impedes electron transfer between UiO-67 and the magnetic core, which can lead to the identification of the adsorbate and its concentration, and achieve a lower detection limit. Furthermore, using Fe3O4 as the magnetic core of the smart adsorbent facilitates the separation and removal process via an external magnetic field. Under optimized conditions, the obtained smart adsorbent exhibits excellent detection and adsorption performance with a high adsorption capacity (256.54 mg g−1), good reusability, and a low detection limit (0.093 mg L−1) for glyphosate, implying that the smart adsorbent has integrated the advantages of the individual components. All of this indicates that MOF-based smart adsorbents are promising for synchronous adsorption/detection and the removal of OPPs, presenting a viable option for monitoring water quality and treating wastewater.

A hybrid monolithic column based on layered double hydroxide-alginate hydrogel for selective solid phase extraction of lead ions in food and water samples

In order to develop an accurate and precise determination method based on solid phase extraction of Pb(II) in food and water samples, a hybrid monolithic column based on layered double hydroxides (LDHs) nanosheets-alginate hydrogel has been synthesized. Combining the advantages of porous 3D framework of hydrogel with selective adsorption of LDHs toward Pb(II), the hydrogel-based hybrid monolithic column shows enhanced enrichment selectivity and efficiency for target ions. Effects of hydrogel composition, pH, concentration and type of eluent, sample volume, and interfering ions on the recoveries of the analytes were also investigated. Under the optimal experiment conditions of method, the limit of detection, preconcentration factor and precision as RSD% are found to be 0.39 μg L-1, 53.7 and 2.65%, respectively. Trace Pb(II) can be quantitatively preconcentrated at pH 6.0 with recoveries >97%. Finally, the method was successfully verified by analyzing spiked Pb2+ in water and drinking samples.

From lamellar to hierarchical: overcoming the diffusion barriers of sulfide-intercalated layered double hydroxides for highly efficient water treatment

Herein, we focus on the design and geometry diversities of two dimensional LDHs nanosheet building blocks from lamellar to hierarchical structures to understand mass transfer mechanisms and highlight the importance of geometry-induced effects to overcome the diffusion constraints in solid–liquid interfaces.

Highly Specific and Sensitive Determination of Propyl Gallate in Food by a Novel Fluorescence Sensor

Propyl gallate (PG), one of the most widely used synthetic phenolic antioxidants in edible oil, cookies and fried food, has received extensive concern due to its possible toxic effects on human health. Herein, a novel fluorescence analytical method is firstly proposed to sensitively and selectively determine propyl gallate (PG) by utilizing the unique fluorescence quenching property of organic molybdate complex (OMC) formed by the specific reaction between MoO42- and PG to g-C3N4 nanosheets. Under the optimum conditions, the developed fluorescence sensor allows highly sensitive detection of PG in a wide range from 0.5 to 200 μg mL-1 with a detection limit of 0.11 μg mL-1, and possesses excellent specificity and good recoveries. All the analytical results indicate the present method provides an effective approach for rapid detection of PG in common products, which is beneficial for monitoring and reducing the risk of overuse of PG.

Highly sensitive furazolidone monitoring in milk by a signal amplified lateral flow assay based on magnetite nanoparticles labeled dual-probe

We presented a signal amplified lateral flow assay (LFA) based on magnetite nanoparticles (MNPs) labeled dual-probe and applied it in the high sensitive and rapid on-site detection of furazolidone metabolite of 3-amino-2-oxazolidinone (AOZ). The amplified signal benefited from high affinity between two probes of MNPs labeled murine monoclonal antibody (MNPs-MAb) and goat anti-mouse antibody (MNPs-GAMA) and was achieved by the generation of dual-probe network complex. This developed method could realize high sensitive detection of AOZ with a threshold value of 0.88 ng mL-1 and a detection limit of 0.044 ng mL-1, the sensitivity was at least 10-fold improved than that of the traditional gold nanoparticle based LFA. This facile developed assay was successfully applied for rapid detection of AOZ in milk samples. The proposed method paves a new way for on-site screening of other hazardous substances in food and can be referred in all lateral flow assays.

An improved clenbuterol detection by immunochromatographic assay with bacteria@Au composite as signal amplifier

Immunochromatographic assays (ICAs) are most frequently used for on-site rapid screening of clenbuterol. To improve sensitivity, a novel probe with bacteria as signal carriers was developed. Bacteria can load a great deal of gold nanoparticles (AuNPs) on their surface, meaning much fewer antibodies are needed to produce clearly visible results, although low concentrations of antibody could also trigger fierce competition between free analyte and the immobilized antigen. Thus, a limited number of antibodies was key to significantly improved sensitivity. Analytical conditions, including bacterial species, coupling method, and concentration, were optimized. The visual detection limit (VDL) for clenbuterol was 0.1 ng/mL, a 20-fold improvement in sensitivity compared with traditional strips. This work has opened up a new route for signal amplification and improved performance of ICAs. Furthermore, inactivated bacteria could also be environment-friendly and robust signal carriers for other biosensors.

Patulin removal from apple juice using a novel cysteine-functionalized metal-organic framework adsorbent

Patulin (PAT) is one of the most common toxic contaminants of apple juice, which causes severe food safety issues throughout the apple industry. In order to remove PAT efficiently, a metal-organic framework-based adsorbent (UiO-66(NH2)@Au-Cys) was successfully synthesized and used for PAT removal from juice-pH simulation solution and real apple juice. Batch adsorption experiments were systematically performed to study the adsorption behavior for PAT. The results showed that adsorption process could be well described by the Pseudo-second order model and Freundlich isotherm model. The maximum adsorption capacity (4.38 µg/mg) was 10 times higher than the microbe-based biosorbents. Thermodynamic investigation demonstrated that adsorption process was spontaneous and endothermic. Furthermore, no marked cytotoxicity on NIH 3T3 cell lines was observed when the concentration of the adsorbent was lower than 10 μg/mL. Therefore, UiO-66(NH2)@Au-Cys is a potential adsorbent for PAT removal from apple juice with little quality changes.

Applicability of biological dye tracer in strip biosensor for ultrasensitive detection of pathogenic bacteria

Here, a facile, label-free and sensitive lateral flow strip (LFS) biosensor for foodborne pathogens was established relying on the innovative introduction of Gram staining and the direct immunoreaction. Target bacteria can be directly marked with crystal violet (CV) by one-step staining which is superior to traditional signal marking techniques in LFS assay, and the methods selectivity can be guaranteed by high-specificity monoclonal antibody. With Salmonella Enteritidis (S. Enteritidis) as a model target, this protocol can selectively detect 80 CFU mL-1S. Enteritidis within 11 min in the optimized conditions. Moreover, with Listeria monocytogenes as another model target, the biosensor shows a high universality for detections of both gram-negative and gram-positive bacteria. The unexpected applicability of biological dye tracer in strip biosensor reveals that the biological dye can be a potential tool serving as a universal signal tracer for pathogenic microorganisms in food safety monitoring and early clinical diagnosis.