Ultrasound-electrochemistry assisted liquid-phase co-exfoliation of phosphorene decorated by Au-Ag bimetallic nanoparticles as nanozyme for smartphone-based portable sensing of 4-nitrophenol.

The stability of black phosphorene (BP) and its preparation and modification for developing and applying devices have become a hot topic in the interdisciplinary field. We propose ultrasound-electrochemistry co-assisted liquid-phase exfoliation as an eco-friendly one-step method to prepare gold-silver bimetallic nanoparticles (Au-AgNPs)-decorated BP nanozyme for smartphone-based portable sensing of 4-nitrophenol (4-NP) in different water sources. The structure, morphology, composition, and properties of Au-AgNPs-BP nanozyme are characterized by multiple instrumental analyses. Bimetallic salts are induced to efficiently occupy oxidative sites of BP to form highly stable Au-AgNPs-BP nanozyme and guarantee the integrity of the lamellar BP. The electrochemistry shortens the exfoliation time of the BP nanosheet and contributes to the loading efficiency of bimetallic nanoparticles on the BP nanosheet. Au-AgNPs-BP-modified screen-printed carbon electrode coupled with palm-sized smartphone-controlled wireless electrochemical analyzer as a portable wireless intelligent sensing platform was applied to the determination of 4-NP in a linear range of 0.6-10 µM with a limit of detection of 63 nM. It enables on-site determination of 4-NP content in lake water, river water, and irrigation ditch water. This work will provide a reference for an eco-friendly one-step preparation of bimetallic nanoparticle-decorated graphene-like materials as nanozymes and their smartphone-based portable sensing application outdoors.

Recent advances in metal-organic framework (MOF)-based agricultural sensors for metal ions: a review.

Metal ions have great significance for agricultural development, food safety, and human health. In turn, there exists an imperative need for the development of novel, sensitive, and reliable sensing techniques for various metal ions. Agricultural sensors for the diagnosis of both agricultural safety and nutritional health can establish quality and safety traceability systems of both agro-products and food to guarantee human health, even life safety. Metal-organic frameworks (MOFs) are utilized widely for the design of diversified sensors due to their distinctive structural characteristics and extraordinary optical and electrical properties. To serve agricultural sensors better, this review is dedicated to providing a brief overview of the synthesis of MOFs, the modification of MOFs, the fabrication of MOF-based film electrodes, the applications of MOF-based agricultural sensors for metal ions, which are centered on electrochemical sensors and optical sensors, and current challenges of MOF-based agricultural sensors. In addition, this review also provides potential future opportunities for the development and practical application of agricultural sensors.

Magnetic Fe3O4 nanoparticles decorated phosphorus-doped biochar-attapulgite/bismuth film electrode for smartphone-operated wireless portable sensing of ultra-trace multiple heavy metal ions.

Pollution caused by both forestry wastes and heavy metals has increasingly drawn attention owing to environmental safety concerns. After essential oil is extracted from Cinnamomum camphoras (L.), the branches are used as forestry wastes to prepare a phosphorus-doped biochar-attapulgite/bismuth film electrode decorated with magnetic Fe3O4 nanoparticles (MBA-BiFE). The smartphone-operated wireless portable sensor is employed for the simultaneous ultratrace voltammetric detection of multiple heavy metal ions (Cd2+, Pb2+, and Hg2+). Cd2+, Pb2+, and Hg2+ exhibit excellent electrochemical responses in linear ranges of 0.1 nM-5 µM, 0.01 nM-7 µM, and 0.1 nM-3 µM with limits of detection equal to 0.036, 0.003, and 0.011 nM, respectively. The recoveries of MBA-BiFE for Cd2+, Pb2+, and Hg2+ are 93.6-109.9%, 86.0-107.5%, and 94.8-104.6%, respectively, and the RSD values for repeated measurements of Cd2+, Pb2+, and Hg2+ are 4.2%, 2.8%, and 3.3%, respectively. A machine learning model based on an artificial neural network algorithm is constructed to enable a smart determination of ultratrace hazardous multiple metal ions. The portable sensor based on the screen-printed integrated three-electrode sensor modified using MBA-BiFE demonstrates advantages and practicability in outdoor detection, compared with conventional sensors based on MBA-BiFE. This study provides a smartphone-operated wireless portable sensing technique for high-potential applications in environmetallomics or agrometallomics using forestry waste-derived biochar as substrate for electrode preparation. HIGHLIGHTS: • Fe3O4 decorated phosphorus-doped biochar-attapulgite/bismuth film electrode. • A smartphone-operated sensor for analysis of multiple heavy metal ions. • An Artificial neural network model for smart analysis of Cd2+, Pb2+, and Hg2+.

Novel RNA genosensor based on highly stable gold nanoparticles decorated phosphorene nanohybrid with graphene for highly sensitive and low-cost electrochemical detection of coconut cadang-cadang viroid.

Coconut cadang-cadang viroid (CCCVd) is an infectious single-stranded RNA (ssRNA) pathogen, which leads directly to the death of a large number of coconut palm trees and heavy economic loss to coconut farmers. Herein, a novel electrochemical impedance RNA genosensor is presented based on highly stable gold nanoparticles (AuNPs) decorated phosphorene (BP) nanohybrid with graphene (Gr) for highly sensitive, low-cost, and label-free detection of CCCVd. BP-AuNPs are environmentally friendly prepared by ultrasonic-assisted liquid-phase exfoliation of black phosphorus, accompanying direct reduction of chloroauric acid. Gr/BP-AuNPs are facilely prepared by the in situ growth of AuNPs onto the BP surface and its nanohybrid with Gr to improve environmental stability of BP. Gr/BP-AuNP-based RNA genosensor is fabricated by immobilizing the thiol-functionalized single-stranded DNA (ssDNA) oligonucleotide probe onto the surface of Gr/BP-AuNP-modified glassy carbon electrode via gold-thiol interactions, which served as an electrochemical genosensing platform for the label-free impedance detection of CCCVd by hybridization between the functionalized ssDNA probe and the complementary CCCVd ssRNA sequence in a wide linear range from 1.0 × 10-11 to 1.0 × 10-7 M with a low limit of detection of 2.8 × 10-12 M. This work supplies an experimental support and theoretical direction for the fabrication of RNA biosensors based on graphene-like materials and potential application for a specific diagnosis of plant RNA viral disease in Arecaceae planting industry.

Synthesis and characterization of Ag-ion-exchanged zeolite/TiO2 nanocomposites for antibacterial applications and photocatalytic degradation of antibiotics.

This paper investigates the synthesis, antibacterial, and photocatalytic properties of silver ion-exchanged natural zeolite/TiO2 photocatalyst nanocomposite. Zeolite is known to have a porous surface structure, making it an ideal substrate and framework in different nanocomposites. Moreover, natural zeolite has a superior thermal and chemical stability, with hardly any reactivity with chemicals. Finding an effective and low-cost method to remove both antibiotics and bacteria from water resources has become a vital global issue due to the worldwide excessive use of chemicals and antibiotics. This research aims to propose a facile method to synthesize Ag-ion-exchanged zeolite/TiO2 catalyst for anti-bacterial purposes and photocatalytic removal of atibiotics from wastewaters. TiO2 particles were deposited on the surface of natural zeolite. Ag ion exchanging was performed via a liquid ion-exchange method using 0.1 M AgNO3 solution. X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR) were used to evaluate the structure of synthesized powders. Antibacterial activities of samples were assessed, using Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922 by disc diffusion method. It was shown that Ag-containing nanocomposite samples have an improved antibacterial performance in both cases. Results showed that the synthesized catalyst has promising potentials in wastewater treatment.

Nanobody-based electrochemical competitive immunosensor for the detection of AFB1 through AFB1-HCR as signal amplifier.

A novel nanobody (Nb)-based voltammetric immunosensor coupled with horseradish peroxidase concatemer-modified hybridization chain reaction (HRP-HCR) signal amplifying system is described to realize the rapid and ultrasensitive detection of AFB1. To design such an immunoassay, anti-AFB1 Nbs with smaller molecular size were coated densely onto the surface of Au nanoparticle-tungsten disulfide-multi-walled carbon nanotubes (AuNPs/WS2/MWCNTs) functional nanocomposites as an effective molecular recognition element, whereas AFB1-streptavidin (AFB1-SA) conjugates were ingeniously bound with biotinylated HCR dsDNA nanostructures as the competitor, amplifier, and signal report element. In the presence of AFB1 targets, a competitive immunoreaction was performed between the analyte and AFB1-SA-labeled HCR (AFB1-HCR) platform. Upon the addition of SA-modified polyHRP (SA-polyHRP), AFB1-HCR nanostructures containing abundant biotins were allowed to cross-link to a quantity of HRP by streptavidin-biotin chemistry for signal amplification and signal conversion. Under optimal conditions, the immunosensor displayed a good linear correlation toward AFB1 ranging from 0.5 to 10 ng mL-1 with a sensitivity of 2.7 µA • (mL ng-1) and an ultralow limit of detection (LOD) of 68 fg mL-1. The specificity test showed that the AFB1 immunosensor had no obvious cross-reaction with OTA, DON, ZEN, and FB1. The signal of this sensor decreased by 10.18% in 4 weeks indicating satisfactory stability, and its intra- and inter-laboratory reproducibility was 3.42~10.35% and 4.03%~12.11%, respectively. This biosensing system will open up new opportunities for the detection of AFB1 in food safety and environmental analysis and extend a wide range of applications in the analysis of other small molecules. Graphical abstract.

Phosphorene nanocomposite with high environmental stability and antifouling capability for simultaneous sensing of clenbuterol and ractopamine.

A series of phosphorene (BP) nanocomposites was prepared to realize simultaneous electrochemical determination of clenbuterol (CLB) and ractopamine (RAC). CLB and RAC are the most commonly used ß-agonists in animal-derived food. The BP nanohybrid was obtained by co-decoration with both mono(6-mercapto-6-deoxy)-ß-cyclodextrin and poly(3,4-ethylenedioxythiophene) nanoparticles. It displays high stability, antifouling capability, a large electrochemical active surface and good electrochemical response. The electrochemical assisted antifouling strategy was selected by further eliminating the fouling of the electrode surface using continuous cyclic voltammetry. The electrode was employed for electrochemical sensing of CLB and RAC at typical peak voltages of 0.8 and 1.0 V (vs. SCE). Responses are linear in the 0.3-90 µM concentration range for CLB, and from 0.3 to 9.4 µM for RAC under optimal conditions. The limit of detection are 0.14 and 0.12 µM, respectively. The sensor was employed for simultaneous determination of CLB and RAC in (spiked) beef, feed and bovine serum samples with acceptable recoveries. Graphical abstractAn electrochemically assisted anti-fouling method for simultaneous voltammetric nanosensing of clenbuterol (CLB) and ractopamine (RAC) in edible cattle product samples using high-stable and anti-foul phosphorene (BP) co-decorated with mono(6-mercapto-6-deoxy)-ß-cyclodextrin (S-ß-CD) and poly(3,4-ethylenedioxythiophene) (PEDOTNPs).

Electrochemical detection combined with machine learning for intelligent sensing of maleic hydrazide by using carboxylated PEDOT modified with copper nanoparticles.

A method for intelligent data analysis was designed by combining electrochemical sensing with machine learning (ML). Specifically, a voltammetric sensor is described for determination of the phytoinhibitor maleic hydrazide in crop samples. Carboxyl-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT-C4-COOH) was electro-synthesized in aqueous micellar solution by direct anodic oxidation of its monomer. A nanosensor was then prepared by placing copper nanoparticles (CuNPs) on the PEDOT-C4-COOH film via electro-deposition of Cu (II) from aqueous micellar solutions. An artificial neural network (ANN) served as a powerful ML model to realize intelligent data analysis and smart transformation for digital output. Different established regression methods were selected for evaluating the ANN-based method that was found to be superior to known methods. The sensor has a wide working range (from 0.06-1000 µM), a low limit of detection (10 nM), good stability, selectivity and practicality. The method was applied to the determination of maleic hydrazide in (spiked) samples of onion, rice, potato and cotton leaf. Satisfactory results demonstrate that the feature of simultaneous data acquisition and analysis is highly attractive. Graphical abstract Schematic representation of an electrochemical sensor based on carboxyl-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT-C4-COOH) and copper nanoparticles (CuNPs) by differential pulse voltammetry (DPV) to detect maleic hydrazide (MH). PEDOT-C4-COOH was electro-synthesized in 0.1 M LiClO4 aqueous micellar solution with 0.1 M sodium dodecyl benzene sulfonate (SDBS) by amperometry (CA). CuNPs was prepared by cyclic voltammetry (CV).

A highly stable black phosphorene nanocomposite for voltammetric detection of clenbuterol.

A nanocomposite was prepared from graphene-like two-dimensional black phosphorene (BP, an allotrope of phosphorus) and nafion (Nf) treated with isopropanol (IP). A glassy carbon electrode (GCE) modified with this nanocomposite was found to be a viable sensor for voltammetric determination of clenbuterol (CLB). Unlike previously reported pure BP, the BP nanocomposite was stable towards water and oxygen. Its morphology, structure, electrochemically active surface area and electrochemical stability were investigated. The BP-Nf (IP) modified GCE displayed good electrochemical stability and electrocatalytic capacity with a low working potential of 0.94 V (vs. SCE), excellent peak current response for CLB in a linear concentration range of 0.06-24 µM with a detection limit of 3.7 nM (3σ/m) and a sensitivity of 0.14 µA·µM-1·cm-2 under optimal conditions. A sensing mechanism for the electro-oxidation of CLB was suggested and verified by density functional theory calculations under imitation of aqueous solution conditions. The sensor was successfully applied to the determination of CLB in bovine meat and bovine serum samples. Graphical abstract Highly-stable black phosphorene (BP) nanocomposite based on Nafion (Nf) was used to modify a glassy carbon electrode (GCE). It is shonw to be a viable electrochemical platform for sensitive voltammetric determination of trace clenbuterol (CLB) in bovine beef and bovine serum.

Induction of defense responses against Magnaporthe oryzae in rice seedling by a new potential biocontrol agent Streptomyces JD211.

The induced resistance against plant pathogens via biocontrol agents is considered as an eco-friendly and promising strategy. In this study, the induced resistance against Magnaporthe oryzae (M. oryzae) in rice seedling by a new potential biocontrol agent Streptomyces JD211 (JD211) was evaluated. The effects of JD211 on defense-related enzymes activities and defense genes expression were investigated. The biocontrol efficacy of different JD211 concentrations was different, and the treatment of 10 g kg-1 JD211 achieved the highest biocontrol efficacy. Activities of catalase, phenylalanine ammonia-lyase (PAL) and ß-1,3-glucanase significantly increased in the presence of JD211. The gene expression level of both PAL and pathogenesis related protein 1 increased when rice seedlings were inoculated with JD211 alone or co-inoculated with M. oryzae, and the expression level of chitinase gene was enhanced by JD211 in the later stage. All results suggested that JD211 could increase the rice resistance by stimulating a series of defense responses, which was the result of induced systemic resistance by JD211. This work will provide a new biocontrol agent against Magnaporthe oryzae in rice seedling.

A Fast Strategy for Determination of Vitamin B9 in Food and Pharmaceutical Samples Using an Ionic Liquid-Modified Nanostructure Voltammetric Sensor.

Vitamin B9 or folic acid is an important food supplement with wide clinical applications. Due to its importance and its side effects in pregnant women, fast determination of this vitamin is very important. In this study we present a new fast and sensitive voltammetric sensor for the analysis of trace levels of vitamin B9 using a carbon paste electrode (CPE) modified with 1,3-dipropylimidazolium bromide (1,3-DIBr) as a binder and ZnO/CNTs nanocomposite as a mediator. The electro-oxidation signal of vitamin B9 at the surface of the 1,3-DIBr/ZnO/CNTs/CPE electrode appeared at 800 mV, which was about 95 mV less positive compared to the corresponding unmodified CPE. The oxidation current of vitamin B9 by square wave voltammetry (SWV) increased linearly with its concentration in the range of 0.08-650 µM. The detection limit for vitamin B9 was 0.05 µM. Finally, the utility of the new 1,3-DIBr/ZnO/CNTs/CPE electrode was tested in the determination of vitamin B9 in food and pharmaceutical samples.

AuNPs-BP-MWCNTs-COOH-based electrochemical immunosensor for the determination of deoxynivalenol in wheat flour.

Deoxynivalenol (DON) has drawn considerable attention for its obvious pathogenicity and wide use in agro-products, which cause a potential threat to human health. In this work, an electrochemical immunosensor is developed for the highly sensitive and selective detection of DON in wheat flour using AuNPs-BP-MWCNTs-COOH and antibodies. The AuNPs-BP-MWCNTs-COOH nanocomposite was prepared via an in situ reduction reaction and ultrasonic-assisted liquid-phase exfoliation. The nanocomposite exhibits a larger surface area, decent stability, excellent electron transfer capability, good protein binding capability and prominent specificity. The plentiful carboxyl group on the nanocomposite can bind to the amino group of the antibody, and AuNPs have an affinity for the sulfhydryl group of the antibody, which makes it feasible for the nanocomposite to load the antibody. The peak currents are plotted against the logarithm of DON concentration from 0.002 to 80 ng mL-1 with a limit of detection (LOD) of 0.5 pg mL-1. This approach establishes an effective label-free immunosensor platform for the detection of DON with high sensitivity and selectivity in various food and agricultural products.

Efficient fluorescent recognition of carboxylates in aqueous media using facilely electrosynthesized poly(9-aminofluorene).

A variety of carboxylates were recognized using poly(9-aminofluorene) (P9AF) in the HEPES buffer (pH 7.4), and a proposed possible mechanism was proposed as following. The intermolecular hydrogen bonding interactions resulted in electron transfer between P9AF and carboxylates. P9AF was facilely electrosynthesized in boron trifluoride diethyl etherate and could be used as an efficient fluorescent sensing material for the detection of AcO(-). On binding to AcO(-), fluorescence quenching of P9AF was demonstrated by a maximum 80% reduction in the fluorescence intensity, while no obvious fluorescence change could be observed in the presence of some other common anions. Some different carboxylates could be recognized at different levels by P9AF. Substituent groups in carboxylates could affect the intermolecular interaction between carboxylates and P9AF. These could be explained by a possible mechanism that hydrogen bonding was the main way of intermolecular interactions between P9AF and carboxylates, which was further confirmed by absorption spectra monitoring and density functional calculations. The significant advantage of this strategy is that it does not require a prequenching procedure and the polymer can be used directly for analyte detection.

Halloysite nanotube/black phosphorene nanohybrid modified screen-printed carbon electrode as an ultra-portable electrochemical sensing platform for smartphone-capable detection of maleic hydrazide with machine learning assistance.

With the assistance of machine learning (ML), black phosphorene (BP) stabilized by silver nanoparticles (AgNPs) is used to modify halloysite nanotube (HNT) to obtain highly conductive nanomaterials, HNT/BP-AgNPs, which are morphologically characterized and elementally analyzed. Artificial neural network (ANN) and least squares support vector machine (LS-SVM) are adopted for the intelligent and rapid analysis of maleic hydrazide (MH). An ultra-portable electrochemical sensor bases on HNT/BP-AgNPs modifying screen-printed carbon electrode (SPCE), smartphone and mini-palm potentiostat for detection of MH in the linear range 0.7-55 µM with limit of detection (LOD) of 0.3 µM. For comparison, a traditional electrochemical sensor is fabricated by glass carbon electrode (GCE), desktop computer and large electrochemical potentiostat, and the linear range is 0.3-600 µM with low LOD of 0.1 µM. The ultra-portable electrochemical sensor combined with ML for the detection of MH in sweat potato and carrot gain satisfactory recoveries.

Machine learning-guided the fabrication of nanozyme based on highly-stable violet phosphorene decorated with phosphorus-doped hierarchically porous carbon microsphere for portable intelligent sensing of mycophenolic acid in silage.

Violet phosphorene (VP) have been proved to be more stable than black phosphorene, but few reports for its application in electrochemical sensors. In this study, a highly-stable VP decorated with phosphorus-doped hierarchically porous carbon microsphere (PCM) with multiple enzyme-like activities as a nanozyme sensing platform for portable intelligent analysis of mycophenolic acid (MPA) in silage with machine learning (ML) assistance is successfully fabricated. The pore size distribution on the PCM surface is discussed using N2 adsorption tests, and morphological characterization indicates that the PCM is embedded in the layers of lamellar VP. The affinity of the VP-PCM nanozyme obtained under the guidance of the ML model reaches Km = 12.4 µmol/L for MPA. The VP-PCM/SPCE for the efficient detection of MPA exhibits high sensitivity, a wide detection range of 2.49 µmol/L - 71.14 µmol/L with a low limit of detection of 18.7 nmol/L. The proposed ML model with high prediction accuracy (R2 = 0.9999, MAPEP = 0.0081) assists the nanozyme sensor for intelligent and rapid quantification of MPA residues in corn silage and wheat silage with satisfactory recoveries of 93.33%-102.33%. The excellent biomimetic sensing properties of the VP-PCM nanozyme are driving the development of a novel MPA analysis strategy assisted by ML in the context of production requirements of livestock safety.

Intelligent analysis of carbendazim in agricultural products based on a ZSHPC/MWCNT/SPE portable nanosensor combined with machine learning methods.

A nano-ZnS-decorated hierarchically porous carbon (ZSHPC) was mixed with MWCNTs to obtain ZSHPC/MWCNT nanocomposites. Then, ZSHPC/MWCNTs were used to modify a screen-printed electrode, and a portable electrochemical detection system combined with machine learning methods was used to investigate carbendazim (CBZ) residues in rice and tea. The electrochemical performance of the constructed electrode showed that the electrode had good electrocatalytic ability, large effective surface area, strong stability and anti-interference ability. Support Vector Machine (SVM), Least Square Support Vector Machine (LS-SVM) and Back Propagation-Artificial Neural Network (BP-ANN) were used to establish the prediction model for CBZ residues in rice and tea, and the traditional linear regression was developed. The investigated results showed that the LS-SVM model had the best prediction performance and the lowest prediction error compared with the traditional linear regression, BP-ANN and SVM models. The R2, RMSE, and MAE for the training set samples were 0.9969, 0.3605 and 0.2968, respectively. The R2, RMSE, MAE and RPD for the prediction set samples were 0.9924, 0.6190, 0.5360 and 10.3097, respectively. The average recovery range of CBZ in tea and rice was 98.77-109.32% and that of RSD was 0.47-2.58%, indicating that the rapid analysis of CBZ pesticide residues in agricultural products based on a portable electrochemical detection system combined with machine learning was feasible.

Lotus seedpods biochar decorated molybdenum disulfide for portable, flexible, outdoor and inexpensive sensing of hyperin.

Biomass waste, a good candidate for advanced carbon materials for sustainable electrodes, is receiving more and more attention for high value-added materials because of its promising contribution to economic growth and sustainable development. We proposed a green co-hydrothermal approach to prepare lotus seedpods biochar (BC) decorated molybdenum disulfide (MoS2) from waste lotus seedpods and precursors of MoS2, and a portable, flexible, outdoor and inexpensive sensing platform for hyperin on the integrated flexible three-electrode using U-disk potentiostat with smartphone was successfully developed. Structure and properties of MoS2-BC were characterized, it was proved that BC improves microstructure and morphology, electronic conductivity, electrode stability and electrocatalytic properties of MoS2. Attributing to these impressive features, the detection signal of hyperin was significantly amplified by the MoS2-BC modified glass carbon electrode (GCE) in detection range of 0.01-21 µΜ with detection limit (LOD) of 5 nM. It was worth mentioning that the MoS2-BC modified screen-printed electrode (SPE) performs hyperin detection in range of 100 nM - 3 µM with LOD 50 nM (S/N = 3). The practicability of the proposed method confirmed that the portable, on-site, low-cost, and outdoor detection of hyperin was feasible and practical in comparison with traditional both electrochemical sensing and HPLC methods.

Green synthesis of kudzu vine biochar decorated graphene-like MoSe2 with the oxidase-like activity as intelligent nanozyme sensing platform for hesperetin.

It is an urgent need to exploit a potentially green, cost efficient and eco-friendly strategy for the utilization of waste kudzu vine. We developed a one-step green preparation of kudzu vine biochar (BC) decorated graphene-like molybdenum selenide (MoSe2) with the oxidase-like activity as intelligent nanozyme sensing platform for voltametric detection of hesperetin (HP) in orange peel using the in-situ hydrothermal synthesis method. The structure and properties of MoSe2-BC was characterized, and found that BC significantly improved electrochemical cycle stability, electronic conductivity, electrochemical active area, and electrocatalytic activity of MoSe2. The oxidase-like activity of MoSe2-BC was confirmed by the oxidization of the colorless substrate 3,3',5,5'-tetramethylbenzidine (TMB) to form blue products and the change of absorbance intensity of UV-vis absorption spectra. The MoSe2-BC exhibited excellent electrochemical sensing performance for the detection of HP in wide linear ranges from 10 nM to 9.5 µM with a low limit of detection of 2 nM using differential pulse voltammetric method. An emerging machine learning technique is used to realize the intelligent sensing of HP, and the performance evaluation of regression analysis was selected to evaluate this technique. This work will provide a guidance for the preparation and application of biochar decorated graphene-like nanomaterials with the oxidase-like activity and the development of intelligent nanozyme sensing platform.

A portable wireless intelligent electrochemical sensor based on layer-by-layer sandwiched nanohybrid for terbutaline in meat products.

The aim of this study is to develop a portable wireless intelligent nanosensor (PWIN) for rapid cost-effective on-site determination of terbutaline (TRA) residue in meat products outdoors in comparison with traditional nanosensor and high-performance liquid chromatography (HPLC). The layer-by-layer sandwiched nanohybrid fabricated by platinum-palladium nanoparticles, carboxylated graphene and graphene-like molybdenum disulfide displayed a wide linear range of 0.55-14.9 µmol/L using the portable potentiostat with smartphone, and the result was almost close to the linear range (0.4-14 µmol/L) using the traditional potentiostat with desktop computer for TRA. The limit of detections were identified as 0.44 µmol/L and 0.18 µmol/L, respectively. PWIN displayed satisfactory recovery (91%-98.43%) of TRA in samples by the standard addition method and in comparison with both traditional sensor (93.79%-98%) and HPLC (93.4%-98.6%), revealing that PWIN for rapid cost-effective on-site analysis in the food safety field is feasible.

Detection and electrocatalytic mechanism of zearalenone using nanohybrid sensor based on copper-based metal-organic framework/magnetic Fe3O4-graphene oxide modified electrode.

A novel and simple strategy was proposed for the determination of ZEA in breakfast cereal, maize powder and rice flour using an electrochemical nanohybrid sensor based on copper-based metal-organic framework (Cu-MOF)/magnetic Fe3O4-graphene oxide (Fe3O4-GO) modified electrode fabricated by the layer-by-layer assembled technique. The synthesized Cu-MOF with high porosity favorably improved the effective surface area and the analytical performance of nanohybrid sensing electrode. The crafted sensor has large surface area, high electron transfer, and satisfactory efficiency. ZEA was electrochemically detected in a wide linear range from 159.2 to 2865.2 ng mL-1 with LOD of 23.14 ng mL-1 under the optimal conditions. Moreover, the electrocatalytic mechanism of ZEA oxidation was proposed by density functional theory (DFT). A favorable energetic interaction was presented when Cu-MOF adsorbed on Fe3O4-GO, and a small new band appeared on the Fermi level energy (Ef) that facilitated the electron transfer between bands.