Novel Olefin-Linked Covalent Organic Framework with Multifunctional Group Modification for the Fluorescence/Smartphone Detection of Uranyl Ion.

Monitoring and purification of uranium contamination are of great importance for the rational utilization of uranium resources and maintaining the environment. In this work, an olefin-linked covalent organic framework (GC-TFPB) and its amidoxime-modified product (GC-TFPB-AO) are synthesized with 3-cyano-4,6-dimethyl-2-hydroxypyridine (GC) and 1,3,5-tris(4-formylphenyl) benzene (TFPB) by Knoevenagel condensation. GC-TFPB-AO results in specificity for rapid fluorescent/smartphone uranyl ion (UO22+) detection based on the synergistic effect of multifunctional groups (amidoxime, pyridine, and hydroxyl groups). GC-TFPB-AO features a rapid and highly sensitive detection and adsorption of UO22+ with a detection limit of 21.25 nM. In addition, it has a good recovery (100-111%) for fluorescence detection in real samples, demonstrating an excellent potential of predesigned olefin-linked fluorescent COFs in nuclear contaminated wastewater detection and removal.

Microwave synthesized novel biomass carbon dots applied in the fluorescent detection of crystal violet.

To establish a new method for detecting crystal violet (CV), a harmful dye, herein, a genre of novel biomass carbon dots (CDs) was synthesized via a microwave method and employed as a fluorescent probe, in which water spinach and polyethylene glycol (PEG) performed as raw materials. Based on the inner filter effect (IFE) between the luminescent CDs and CV, the blue emission of this probe at 430 nm could be quenched by CV. Hence, a new strategy was proposed to selectively determine CV in aquaculture ambient. Moreover, under the optimal experiment conditions, this method showed a good linearity between the concentration of CV (c) and fluorescence quenching rate (ΔF/F0) in the concentration range of 4-200 µmol/L with the corresponding correlation coefficient (r) and the detection limit of 0.997 and 710 nmol/L, respectively. With advantages of environmental protectivity, sensitivity, affordability, and user-friendliness, the facilely fabricated CDs could be successfully applied in detecting CV in aquaculture samples, providing a technical foundation for monitoring the pollution of CV and ensuring the quality and safety of aquatic products.

A Dual-Signal Sensing for the Visual and Luminescent Detection of p-Phenylenediamine Based on Cerium-Nitrogen-Co-Doped Carbon Dots.

Herein, a visual and luminescent dual-mode (colorimetric and fluorometric) method for the detection of P-phenylenediamine (PPD) in hair dye was successfully established based on cerium-nitrogen co-doped carbon dots (Ce, N-CDs) that displayed remarkable luminescence and peroxidase activity. Ce, N-CDs catalyzed H2O2 to produce superoxide anion, which then oxidized the colorless 3,3,5,5-tetramethylbenzidine (TMB) into blue oxidized TMB (oxTMB), capable of quenching the fluorescence through fluorescence resonance energy transfer (FRET) between Ce, N-CDs and oxTMB. The reducing properties of PPD could reduce oxTMB back to TMB, leading to a decrease in the absorption intensity of oxTMB and a fluorescence recovery of Ce, N-CDs. As a result, the quantitative detection of PPD could be achieved by measuring the absorption values of oxTMB and the fluorescence signal of Ce, N-CDs. The detection limits for PPD were calculated as 0.36 µM and 0.10 µM for colorimetry and fluorimetry, respectively. Furthermore, smartphone application (ColorPicker) capable of measuring the RGB value of the color was utilized in the detection system, facilitating on-site quantitative detection. This approach effectively shortens the detection time and simplifies the operation, offering a powerful and convenient tool for real-time monitoring of PPD.

Dual-signal detection of tannic acid in red wines based on the peroxidase activity of carbon dots.

Herein, a novel type of phosphorus and iron-doped carbon dot (P,Fe-CD) with outstanding peroxidase activity and excellent fluorescence performance was hydrothermally synthesized to colorimetrically and fluorimetrically detect tannic acid (TA). In the presence of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2, the P,Fe-CDs could oxidize colorless TMB to a blue oxidation product (oxTMB) resulting in an increased value of absorbance. Simultaneously, the fluorescence intensity of P,Fe-CDs at 430 nm could be quenched owing to the fluorescence resonance energy transfer (FRET) between P,Fe-CDs and the generated oxTMB. Meanwhile, after adding the TA to the system containing TMB, H2O2 and P,Fe-CDs, the value of absorbance could be decreased and the fluorescence could be recovered because of the reduction reaction between TA and oxTMB. Therefore, fluorescence intensity and value of absorbance could be applied to quantitatively detect TA with good linearities between the concentration of TA and the fluorescence intensity/value of absorbance (0.997 and 0.997 for the colorimetric signal and fluorimetric one, respectively) and low limits of detection (0.093 µmol L-1 and 0.053 µmol L-1 for the colorimetry and the fluorimetry, respectively), which was successfully applied to the detection of TA in red wines. Moreover, we applied a smartphone-assisted method to the point-of-care detection of TA with accurate results, providing a new technique for TA detection and food quality monitoring.

Sodium alginate hydrogelation mediated paper-based POCT sensor for visual distance reading and smartphone-assisted colorimetric dual-signal determination of L-lactate.

Herein, we present a paper-based POCT sensor based on lactate dehydrogenase-mediated alginate gelation combined with visual distance reading and smartphone-assisted colorimetric dual-signal analysis to determine the concentration of L-lactate in yogurt samples. In this research, L-lactate was transformed into pyruvate by lactate dehydrogenase. Pyruvate then triggered the gelation of a sol mixture, increasing the viscosity (ηs) of the mixture, which was shown as a decrease in the diffusion diameter on the paper-based sensor. In addition, protons from pyruvate accelerated the degradation of Rhodamine B, causing color fading of the mixture, which was analyzed using RGB analysis application software. Under optimal experimental conditions, the linear ranges of visual distance reading and smartphone-assisted colorimetric analysis were 0.1-15 µM and 0.3-15 µM and the detection limits were 0.03 µM and 0.07 µM, respectively. As a proof-of-concept application, we exploited the paper-based sensor to determine the concentration of L-lactate in yogurt samples. The results from the dual-signal paper-based sensor were consistent with the ones from HPLC analysis. In short, this study developed a simple, convenient, cost-effective, and feasible method for the quantitative detection of L-lactate in real samples.

Orbital Magneto-Nonlinear Anomalous Hall Effect in Kagome Magnet Fe_{3}Sn_{2}.

It has been theoretically predicted that perturbation of the Berry curvature by electromagnetic fields gives rise to intrinsic nonlinear anomalous Hall effects that are independent of scattering. Two types of nonlinear anomalous Hall effects are expected. The electric nonlinear Hall effect has recently begun to receive attention, while very few studies are concerned with the magneto-nonlinear Hall effect. Here, we combine experiment and first-principles calculations to show that the kagome ferromagnet Fe_{3}Sn_{2} displays such a magneto-nonlinear Hall effect. By systematic field angular and temperature-dependent transport measurements, we unambiguously identify a large anomalous Hall current that is linear in both applied in-plane electric and magnetic fields, utilizing a unique in-plane configuration. We clarify its dominant orbital origin and connect it to the magneto-nonlinear Hall effect. The effect is governed by the intrinsic quantum geometric properties of Bloch electrons. Our results demonstrate the significance of the quantum geometry of electron wave functions from the orbital degree of freedom and open up a new direction in Hall transport effects.

Electrospun organic/inorganic hybrid nanofibers for accelerating wound healing: a review.

Electrospun nanofiber membranes hold great promise as scaffolds for tissue reconstruction, mirroring the natural extracellular matrix (ECM) in their structure. However, their limited bioactive functions have hindered their effectiveness in fostering wound healing. Inorganic nanoparticles possess commendable biocompatibility, which can expedite wound healing; nevertheless, deploying them in the particle form presents challenges associated with removal or collection. To capitalize on the strengths of both components, electrospun organic/inorganic hybrid nanofibers (HNFs) have emerged as a groundbreaking solution for accelerating wound healing and maintaining stability throughout the healing process. In this review, we provide an overview of recent advancements in the utilization of HNFs for wound treatment. The review begins by elucidating various fabrication methods for hybrid nanofibers, encompassing direct electrospinning, coaxial electrospinning, and electrospinning with subsequent loading. These techniques facilitate the construction of micro-nano structures and the controlled release of inorganic ions. Subsequently, we delve into the manifold applications of HNFs in promoting the wound regeneration process. These applications encompass hemostasis, antibacterial properties, anti-inflammatory effects, stimulation of cell proliferation, and facilitation of angiogenesis. Finally, we offer insights into the prospective trends in the utilization of hybrid nanofiber-based wound dressings, charting the path forward in this dynamic field of research.

Orbital Origin of the Intrinsic Planar Hall Effect.

Recent experiments reported an antisymmetric planar Hall effect, where the Hall current is odd in the in plane magnetic field and scales linearly with both electric and magnetic fields applied. Existing theories rely exclusively on a spin origin, which requires spin-orbit coupling to take effect. Here, we develop a general theory for the intrinsic planar Hall effect (IPHE), highlighting a previously unknown orbital mechanism and connecting it to a band geometric quantity-the anomalous orbital polarizability (AOP). Importantly, the orbital mechanism does not request spin-orbit coupling, so sizable IPHE can occur and is dominated by an orbital contribution in systems with weak spin-orbit coupling. Combined with first-principles calculations, we demonstrate our theory with quantitative evaluation for bulk materials TaSb_{2}, NbAs_{2}, and SrAs_{3}. We further show that AOP and its associated orbital IPHE can be greatly enhanced at topological band crossings, offering a new way to probe topological materials.

Heavy-to-light electron transition enabling real-time spectra detection of charged particles by a biocompatible semiconductor.

The current challenge of wearable/implantable personal dosimeters for medical diagnosis and radiotherapy applications is lack of suitable detector materials possessing both excellent detection performance and biocompatibility. Here, we report a solution-grown biocompatible organic single crystalline semiconductor (OSCS), 4-Hydroxyphenylacetic acid (4HPA), achieving real-time spectral detection of charged particles with single-particle sensitivity. Along in-plane direction, two-dimensional anisotropic 4HPA exhibits a large electron drift velocity of 5 × 105 cm s-1 at "radiation-mode" while maintaining a high resistivity of (1.28 ± 0.003) × 1012 Ω·cm at "dark-mode" due to influence of dense π-π overlaps and high-energy L1 level. Therefore, 4HPA detectors exhibit the record spectra detection of charged particles among their organic counterparts, with energy resolution of 36%, (µt)e of (4.91 ± 0.07) × 10-5 cm2 V-1, and detection time down to 3 ms. These detectors also show high X-ray detection sensitivity of 16,612 µC Gyabs-1 cm-3, detection of limit of 20 nGyair s-1, and long-term stability after 690 Gyair irradiation.

Interfacial magnetic spin Hall effect in van der Waals Fe3GeTe2/MoTe2 heterostructure.

The spin Hall effect (SHE) allows efficient generation of spin polarization or spin current through charge current and plays a crucial role in the development of spintronics. While SHE typically occurs in non-magnetic materials and is time-reversal even, exploring time-reversal-odd (T-odd) SHE, which couples SHE to magnetization in ferromagnetic materials, offers a new charge-spin conversion mechanism with new functionalities. Here, we report the observation of giant T-odd SHE in Fe3GeTe2/MoTe2 van der Waals heterostructure, representing a previously unidentified interfacial magnetic spin Hall effect (interfacial-MSHE). Through rigorous symmetry analysis and theoretical calculations, we attribute the interfacial-MSHE to a symmetry-breaking induced spin current dipole at the vdW interface. Furthermore, we show that this linear effect can be used for implementing multiply-accumulate operations and binary convolutional neural networks with cascaded multi-terminal devices. Our findings uncover an interfacial T-odd charge-spin conversion mechanism with promising potential for energy-efficient in-memory computing.

Symmetry-selective quasiparticle scattering and electric field tunability of the ZrSiS surface electronic structure.

Three-dimensional Dirac semimetals with square-net non-symmorphic symmetry, such as ternary ZrXY (X = Si, Ge; Y = S, Se, Te) compounds, have attracted significant attention owing to the presence of topological nodal lines, loops, or networks in their bulk. Orbital symmetry plays a profound role in such materials as the different branches of the nodal dispersion can be distinguished by their distinct orbital symmetry eigenvalues. The presence of different eigenvalues suggests that scattering between states of different orbital symmetry may be strongly suppressed. Indeed, in ZrSiS, there has been no clear experimental evidence of quasiparticle scattering reported between states of different symmetry eigenvalues at small wave vectorq⃗.Here we show, using quasiparticle interference, that atomic step-edges in the ZrSiS surface facilitate quasiparticle scattering between states of different symmetry eigenvalues. This symmetry eigenvalue mixing quasiparticle scattering is the first to be reported for ZrSiS and contrasts quasiparticle scattering with no mixing of symmetry eigenvalues, where the latter occurs with scatterers preserving the glide mirror symmetry of the crystal lattice, e.g. native point defects in ZrSiS. Finally, we show that the electronic structure of the ZrSiS surface, including its unique floating band surface state, can be tuned by a vertical electric field locally applied by the tip of a scanning tunneling microscope (STM), enabling control of a spin-orbit induced avoided crossing near the Fermi level by as much as 300%.

Exploring the hormetic effects of radiation on the life table parameters of Spodoptera frugiperda.

BACKGROUND: Spodoptera frugiperda, a global agricultural pest, can be effectively controlled through the sterile insect technique. However, exposure to low-dose radiation below the sterilization threshold may induce hormetic effects. Here, the biphasic aspects of the fertile progeny population of S. frugiperda were analyzed using an age-stage, two-sex life table after dosing male and female pupae with 10-350 Gy gamma radiation. RESULTS: The parental sterilizing dose for 6-day-old female and male pupae was 200 and 350 Gy, respectively. The total longevity, pre-adult survival rate, net reproduction rate, and intrinsic growth rate of the offspring population increased with decreasing radiation doses from 250 to 10 Gy. Offspring population of parents treated with low doses of 10-100 Gy showed better life table parameters compared to non-irradiated controls. Females and males fecundity irradiated with 10, 50, and 100 Gy and 10 Gy, respectively, exceeded controls, producing 2339.4, 2726.4, 2311, and 2369 eggs, as opposed to 1802.9 eggs produced by the controls. Males irradiated with 10 Gy displayed the highest intrinsic rates of increase and net reproduction rate, at 0.1709 and 682.3, respectively. Projections from the survival rate and fecundity indicated that female and male S. frugiperda populations after 10 Gy irradiation may grow considerably faster than the controls. CONCLUSION: This study explores the hormetic effects of low-dose radiation on S. frugiperda through life table analysis, while providing enhancements for utilizing substerilizing gamma dose in a modified F1 sterility technique. © 2023 Society of Chemical Industry.

The Coexistence of Superconductivity and Topological Order in Van der Waals InNbS2.

The research on systems with coexistence of superconductivity and nontrivial band topology has attracted widespread attention. However, the limited availability of material platforms severely hinders the research progress. Here, it reports the first experimental synthesis and measurement of high-quality single crystal van der Waals transition-metal dichalcogenide InNbS2 , revealing it as a topological nodal line semimetal with coexisting superconductivity. The temperature-dependent measurements of magnetization susceptibility and electrical transport show that InNbS2 is a type-II superconductor with a transition temperature Tc of 6 K. First-principles calculations predict multiple topological nodal ring states close to the Fermi level in the presence of spin-orbit coupling. Similar features are also observed in the as-synthesized BiNbS2 and PbNbS2 samples. This work provides new material platforms ANbS2 (A = In, Bi, and Pb) and uncovers their intriguing potential for exploring the interplay between superconductivity and band topology.

A novel electrochemical sensing method based on an amino-functionalized MXene for the rapid and selective detection of Hg2.

Mercury is a highly toxic element that is widely present in all types of environmental media and can accumulate in living organisms. Prolonged exposure to high levels of mercury can lead to brain damage and death, so the detection of mercury is of great importance. In this study, a cost-effective and easy-to-operate electrochemical sensing method was successfully developed based on an amino-functionalized titanium-based MXene (NH2-Ti3C2Tx) for the rapid and selective detection of Hg2+ that could have a coordination effect with the -NH2 group of NH2-Ti3C2Tx to promote the efficient accumulation of Hg2+. In this strategy, the NH2-Ti3C2Tx was first modified on glassy carbon electrodes (GCE) to fabricate the electrochemical sensor. Benefiting from the excellent electrical conductivity, abundant active sites, and strong adsorption capacity performance of the NH2-Ti3C2Tx, the NH2-Ti3C2Tx modified GCE (NH2-Ti3C2Tx/GCE) exhibited satisfactory selectivity and enhanced square wave anodic stripping voltammetry (SWASV) measurement for the rapid detection of trace amounts of Hg2+ in aqueous solutions. The electrochemical sensor was found to be capable of detecting Hg2+ with a low detection limit of 8.27 nmol L-1 and a linear range of 0.5 µmol L-1 to 50 µmol L-1. The response time of the electrochemical sensing method was 308 s. In addition, the electrochemical sensing method has good selectivity, repeatability and stability, and multiple heavy metal ions have no effect on its detection, with repeatability and stability RSDs of 1.68% and 1.43%, respectively. Furthermore, the analysis of practical water samples demonstrated that the developed method was highly practical for the actual determination of Hg2+ with recoveries in the range of 99.22-101.90%.

Giant and Nonanalytic Negative Piezoelectric Response in Elemental Group-Va Ferroelectric Monolayers.

Materials with negative longitudinal piezoelectric response have been a focus of recent research. So far, reported examples are mostly three-dimensional bulk materials, either compounds with strong ionic bonds or layered materials with van der Waals interlayer gaps. Here, we report the first example in two-dimensional elemental materials-the class of group-Va monolayers. From first-principles calculations, we show that these materials possess giant negative longitudinal piezoelectric coefficient e_{11}. Importantly, its physical mechanism is also distinct from all previous proposals, connected with the special buckling driven polarization in these elemental systems. As a result, the usually positive internal strain contribution to piezoelectricity becomes negative and even dominates over the clamped ion contribution in Bi monolayers. Based on this new mechanism, we also find several 2D crystal structures that may support negative longitudinal piezoelectricity. As another consequence, piezoelectric response in Bi monolayers exhibits a significant nonanalytic behavior, namely, the e_{11} coefficient takes sizably different values (differed by ∼18%) under tensile and compressive strains, a phenomenon not known before and helpful for the development of novel electromechanical devices.

A Cascade Signal Amplification Strategy for the Ultrasensitive Fluorescence Detection of Cu2+ via λ-Exonuclease-Assisted Target Recycling with Mismatched Catalytic Hairpin Assembly.

Herein, an ultrasensitive DNAzyme-based fluorescence biosensor for detecting Cu2+ was designed using the cascade signal amplification strategy, coupling λ-exonuclease-assisted target recycling and mismatched catalytic hairpin assembly (MCHA). In the designed detection system, the target, Cu2+, can activate the Cu2+-dependent DNAzyme to cause a cleavage reaction, releasing ssDNA (tDNA). Then, tDNA binds to hairpin DNA (H0) with an overhanging 5'-phosphorylated terminus to form dsDNA with a blunt 5'-phosphorylated terminus, which activates the dsDNA to be digested by λ-Exo and releases tDNA along with another ssDNA (iDNA). Subsequently, the iDNA initiates MCHA, which can restore the fluorescence of carboxyfluorescein (FAM) previously quenched by tetramethylrhodamine (TAMRA), resulting in a strong fluorescent signal. Furthermore, MCHA efficiently improves the signal-to-noise ratio of the detection system. More importantly, tDNA recycling can be achieved with the λ-Exo digestion reaction to release more iDNA, efficiently amplifying the fluorescent signal and further improving the sensitivity to Cu2+ with a detection limit of 60 fM. The practical application of the developed biosensor was also demonstrated by detecting Cu2+ in real samples, proving it to be an excellent analytical strategy for the ultrasensitive quantification of heavy metal ions in environmental water sources.

Multi-index fuzzy comprehensive evaluation model with information entropy of alfalfa salt tolerance based on LiDAR data and hyperspectral image data.

Rapid, non-destructive and automated salt tolerance evaluation is particularly important for screening salt-tolerant germplasm of alfalfa. Traditional evaluation of salt tolerance is mostly based on phenotypic traits obtained by some broken ways, which is time-consuming and difficult to meet the needs of large-scale breeding screening. Therefore, this paper proposed a non-contact and non-destructive multi-index fuzzy comprehensive evaluation model for evaluating the salt tolerance of alfalfa from Light Detection and Ranging data (LiDAR) and HyperSpectral Image data (HSI). Firstly, the structural traits related to growth status were extracted from the LiDAR data of alfalfa, and the spectral traits representing the physical and chemical characteristics were extracted from HSI data. In this paper, these phenotypic traits obtained automatically by computation were called Computing Phenotypic Traits (CPT). Subsequently, the multi-index fuzzy evaluation system of alfalfa salt tolerance was constructed by CPT, and according to the fuzzy mathematics theory, a multi-index Fuzzy Comprehensive Evaluation model with information Entropy of alfalfa salt tolerance (FCE-E) was proposed, which comprehensively evaluated the salt tolerance of alfalfa from the aspects of growth structure, physiology and biochemistry. Finally, comparative experiments showed that: (1) The multi-index FCE-E model based on the CPT was proposed in this paper, which could find more salt-sensitive information than the evaluation method based on the measured Typical Phenotypic Traits (TPT) such as fresh weight, dry weight, water content and chlorophyll. The two evaluation results had 66.67% consistent results, indicating that the multi-index FCE-E model integrates more information about alfalfa and more comprehensive evaluation. (2) On the basis of the CPT, the results of the multi-index FCE-E method were basically consistent with those of Principal Component Analysis (PCA), indicating that the multi-index FCE-E model could accurately evaluate the salt tolerance of alfalfa. Three highly salt-tolerant alfalfa varieties and two highly salt-susceptible alfalfa varieties were screened by the multi-index FCE-E method. The multi-index FCE-E method provides a new method for non-contact non-destructive evaluation of salt tolerance of alfalfa.

Magnetic Real Chern Insulator in 2D Metal-Organic Frameworks.

Real Chern insulators have attracted great interest, but so far, their material realization is limited to nonmagnetic crystals and systems without spin-orbit coupling. Here, we reveal the magnetic real Chern insulator (MRCI) state in a recently synthesized metal-organic framework material Co3(HITP)2. Its ground state with in-plane ferromagnetic ordering hosts a nontrivial real Chern number, enabled by the C2zT symmetry and robustness against spin-orbit coupling. Distinct from previous nonmagnetic examples, the topological corner zero modes of MRCIs are spin-polarized. Furthermore, under small tensile strains, the material undergoes a topological phase transition from the MRCI to a magnetic double-Weyl semimetal phase, via a pseudospin-1 critical state. Similar physics can also be found in closely related materials Mn3(HITP)2 and Fe3(HITP)2, which also exist. Possible experimental detections and implications of an emerging magnetic flat band in the system are discussed.

[Rapid determination of five halobenzoquinones in aquatic products by QuEChERS-ultra performance liquid chromatography-tandem mass spectrometry].

Halobenzoquinones (HBQs), which are emerging chlorinated disinfection byproducts (DBPs), have attracted increasing attention because they are frequently detected in treated tap water, entrainment water, etc. These compounds are mainly generated during the water treatment process using chlorine, chloramine, and chlorine dioxide as disinfectants, and display more toxic effects than regulated DBPs, such as trihalomethane and haloacetic acid. HBQs have been recognized as potential bladder carcinogens and are harmful to the nervous system. Additionally, they can exert genotoxic effects and cause oxidative damage to DNA and proteins. The risk of HBQs in aquatic products is expected to rise because the disinfection of public facilities has significantly increased in recent years. Therefore, developing a sensitive and accurate analytical method to detect HBQs in aquatic products is of great importance. Several analytical methods, including gas chromatography, gas chromatography-mass spectrometry, electrochemical methods, liquid chromatography, and liquid chromatography-tandem mass spectrometry, can be used to identify and quantify HBQs in water. However, to the best of our knowledge, no reports on the determination of HBQ levels in aquatic products are yet available. Further, pretreatment is essential for HBQ determination because of the complex matrix effects of aquatic products. Herein, a sensitive and accurate method based on the QuEChERS technique coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of five HBQs in aquatic products. For the QuEChERS procedure, the pretreatment conditions, such as the extraction solvent and adsorbent species, were systematically optimized. The sample was extracted with 10 mL of 10% methanol acetonitrile solution (containing 0.1% formic acid), dehydrated, and centrifuged with sodium chloride and anhydrous magnesium sulfate. The supernatant was purified using a QuEChERS packing material consisting of 50 mg N-propylethylenediamine (PSA), 30 mg of graphitized carbon black (GCB), and 30 mg of neutral alumina (Al2O3), dried with nitrogen, and concentrated. The five HBQs were separated on a Waters ACQUITY UPLC BEH C18 column (100 mm×2.1 mm, 1.7 µm) using 0.25% acetonitrile formate solution and 0.25% formic acid aqueous solution as the mobile phase under a gradient elution program and then detected using UPLC-MS/MS with negative electrospray ionization (ESI-) under multiple reaction monitoring (MRM) mode. Quantitative analysis was performed using a matrix-matched external standard method. The five HBQs achieved rapid separation within 6 min, indicating that the proposed method has a much shorter separation time compared with previous studies. The matrix effect was evaluated by establishing a matrix-matched calibration curve. The results showed that 2,5-dichloro-1,4-benzoquinone (2,5-DCBQ) presented a matrix-enhancing effect, whereas the other HBQs displayed matrix-inhibiting effects. In particular, tetrachlorobenzoquinone (TCBQ) exhibited strong inhibitory effects. Under the optimized experimental conditions, the five HBQs demonstrated good linear relationships in the range of 1.0-50.0 µg/L, with correlation coefficients (r)≥0.9992. The detection limits of the method were 0.15-0.8 µg/kg, and the recoveries of the target compounds were 85.9%-116.5%. The relative standard deviations were 1.4%-8.2%, which indicates good reproducibility. The proposed method was successfully applied to actual sample detection, and 2,6-dichloro-3-methyl-1,4-benzoquinone (2,6-DCMBQ) was detected in grass carp. The proposed method is convenient, sensitive, accurate, and suitable for the simultaneous determination of five HBQs in aquatic products. Moreover, the developed method provides a reliable reference for the routine monitoring of trace HBQs in food samples.

A self-cascade system based on Ag nanoparticle/single-walled carbon nanotube nanocomposites as an enzyme mimic for ultrasensitive detection of L-cysteine.

L-Cysteine, widely used in medicine and the food industry, is of great essentiality to organisms and the food quality. Given that current detection approaches require exacting lab conditions and tedious sample treatment, there is a pressing demand for developing a method that possesses advantages of user friendliness, prominent performance, and cost-effectiveness. Herein, a self-cascade system was developed for the fluorescence detection of L-cysteine based on the ingenious performance of Ag nanoparticle/single-walled carbon nanotube nanocomposites (AgNP/SWCNTs) and DNA-templated Ag nanoclusters (DNA-AgNCs). The fluorescence of DNA-AgNCs could be quenched on account of the adsorption of DNA-AgNCs on AgNP/SWCNTs by π-π stacking. With the cooperation of Fe2+, AgNP/SWCNTs with oxidase and peroxidase-like activities could catalyze the oxidation of L-cysteine to produce cystine and hydrogen peroxide (H2O2) and then break the O-O bond of H2O2 to generate a hydroxyl radical (·OH), which could cleave the DNA strand into different sequence fragments which subsequently peeled off from the AgNP/SWCNTs, resulting in a "turn-on" fluorescence response. In this paper, AgNP/SWCNTs with multi-enzyme activities was synthesized enabling the reaction to proceed in just one step. The successful preliminary applications for the L-cysteine detection in pharmaceutical, juice beverage, and serum samples indicated that the developed method exhibited great potential in medical diagnosis, food monitoring, and the biochemical field, which also broadened the horizon for follow-up research.