A novel molecular imprinted QCM sensor based on MoS(2)NPs-MWCNT nanocomposite for zearalenone determination

Zearalenone (ZEN) is a mycotoxin that has a carcinogenic effect and is often found at a high rate in frequently consumed foods. In this study, a characteristic molecular imprinted quartz crystal microbalance (QCM) sensor based on molybdenum disulfide nanoparticle (MoS(2)NPs)-multiwalled carbon nanotube (MWCNT) nanocomposite (MoS(2)NPs-MWCNTs) is presented for selective determination of ZEA in rice samples. Firstly, molybdenum disulfide nanoparticle (MoS2NP)-multiwalled carbon nanotube nanocomposites were characterized by using microscopic, spectroscopic, and electrochemical techniques. Then, ZEA-imprinted QCM chip was prepared in the presence of methacryloylamidoglutamicacid (MAGA) as monomer, N,N'-azobisisobutyronitrile (AIBN) as initiator, and ZEA as target molecule by using UV polymerization. The sensor revealed a linearity toward ZEA in the range 1.0-10.0 ng L-1 with a detection limit (LOD) of 0.30 ng L-1. The high repeatability, reusability, selectivity, and stability of the developed sensor enable reliable ZEA detection in rice samples

A molecularly imprinted electrochemical biosensor based on hierarchical Ti2Nb10O29 (TNO) for glucose detection

A novel molecularly imprinted electrochemical biosensor for glucose detection is reported based on a hierarchical N-rich carbon conductive-coated TNO structure (TNO@NC ). Firstly, TNO@NC was fabricated by a novel polypyrrole-chemical vapor deposition (PPy-CVD) method with minimal waste generation. Afterward, the electrode modification with TNO@ NC was performed by dropping TNO@NC particles on glassy carbon electrode surfaces by infrared heat lamp. Finally, the glucose-imprinted electrochemical biosensor was developed in presence of 75.0 mM pyrrole and 25.0 mM glucose in a potential range from+ 0.20 to +1.20 V versus Ag/AgCl via cyclic voltammetry (CV). The physicochemical and electrochemical characterizations of the fabricated molecularly imprinted biosensor was conducted by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) method, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and CV techniques. The findings demonstrated that selective, sensitive, and stable electrochemical signals were proportional to different glucose concentrations, and the sensitivity of molecularly imprinted electrochemical biosensor for glucose detection was estimated to be 18.93 RA mu M-1 cm(-2) ( R-2 = 0.99) = 0.99) at + 0.30 V with the limit of detection (LOD) of 1.0 x10(-6) M. Hence, it can be speculated that the fabricated glucose-imprinted biosensor may be used in a multitude of areas, including public health and food quality

Electrochemical immunosensor development based on core-shell high-crystalline graphitic carbon nitride@carbon dots and Cd0.5Zn0.5S/d-Ti3C2Tx MXene composite for heart-type fatty acid-binding protein detection

Acute myocardial infarction (AMI) is a significant health problem owing to its high mortality rate. Heart-type fatty acid-binding protein (h-FABP) is an important biomarker in the diagnosis of AMI. In this work, an electrochemical h-FABP immunosensor was developed based on Cd0.5Zn0.5S/d-Ti3C2Tx MXene (MXene: Transition metal carbide or nitride) composite as signal amplificator and core-shell high-crystalline graphitic carbon nitride@carbon dots (hc-g-C3N4@CDs) as electrochemical sensor platform. Firstly, a facile calcination technique was applied to the preparation of hc-g-C3N4@CDs and immobilization of primary antibody was performed on he-g-C3N4@CDs surface. Then, the conjugation of the second antibody to Cd0.5Zn0.5S/d-Ti3C2Tx MXene was carried out by strong pi-pi and electrostatic interactions. The prepared electrochemical h-FABP immunosensor was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD) method, Fourier-transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The prepared electrochemical h-FABP immunosensor indicated a good sensitivity with detection limit (LOD) of 3.30 fg mL(-1) in the potential range +0.1 to +0.5 V. Lastly, low-cost, satisfactory stable, and environmentally friendly immunosensor was presented for the diagnosis of acute myocardial infarction

Sensitive sandwich-type electrochemical SARS-CoV-2 nucleocapsid protein immunosensor

A sensitive and fast sandwich-type electrochemical SARS-CoV-2 (COVID-19) nucleocapsid protein immunosensor was prepared based on bismuth tungstate/bismuth sulfide composite (Bi2WO6/Bi2S3) as electrode platform and graphitic carbon nitride sheet decorated with gold nanoparticles (Au NPs) and tungsten trioxide sphere composite (g-C3N(4)/Au/WO3) as signal amplification. The electrostatic interactions between capture antibody and Bi2WO6/Bi2S3 led to immobilization of the capture nucleocapsid antibody. The detection antibody was then conjugated to g-C3N(4)/Au/WO3 via the affinity of amino-gold. After physicochemically characterization via transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) analysis were implemented to evaluate the electrochemical performance of the prepared immunosensor. The detection of SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 NP) in a small saliva sample (100.0 mu L) took just 30 min and yielded a detection limit (LOD) of 3.00 fg m(-1), making it an effective tool for point-of-care COVID-19 testing

Bisphenol a imprinted electrochemical sensor based on graphene quantum dots with boron functionalized g-c3n4 in food samples

A molecular imprinted electrochemical sensor based on boron-functionalized graphitic carbon nitride (B-g-C3N4) and graphene quantum dots (GQDs) was presented for selective determination of bisphenol A (BPA). In particular, by combining the selectivity and high stability properties, which are the most important advantages of molecular imprinted polymers, and the highly sensitive properties of GQDs/B-g-C3N4 nanocomposite, a highly selective and sensitive analytical method was developed for BPA analysis. Firstly, GQDs/B-g-C3N4 nanocomposite was characterized by using microscopic, spectroscopic, and electrochemical techniques. This novel molecular imprinted electrochemical sensor for BPA detection demonstrated a linearity of 1.0 x 10(-11)-1.0 x 10(-9) M and a low detection limit (LOD, 3.0 x 10(-12) M). BPA-imprinted polymer on GQDs/B-g-C3N4 nanocomposite also showed good stability, repeatability and selectivity in food samples

Chemical, Electrochemical, and Surface Morphological Studies of the Corrosion Behavior of the AZ31 Alloy in Simulated Body Fluid: Effect of NaOH and H2O2Surface Pretreatments on the Corrosion Resistance Property

Magnesium and its alloys have attracted attention for biomedical implant materials in dental and orthopedic applications because of their biodegradability and similar properties to human bones. The very high rate of degradation in the physiological systems is, however, a major setback to their utilization. Chemical modification is one of the approaches adopted to enhance the corrosion resistance property of Mg and its alloys. In this work, NaOH and H2O2were used as a pretreatment procedure to improve the corrosion resistance of the AZ31 Mg alloy in simulated body fluid (SBF). Advanced techniques such as dynamic electrochemical impedance spectroscopy (dynamic-EIS), atomic force microscopy, and optical profilometry were used in addition to the classical mass loss, hydrogen evolution, EIS, and polarization techniques to study the corrosion resistance property of the alloy in SBF for 30 h. Results obtained show that the surface treatment significantly enhanced the corrosion resistance property of the alloy. From dynamic-EIS at 30 h, the charge transfer resistance of the untreated AZ31 Mg alloy is 432.6 ω cm2, whereas 822.7 and 2617.3 ω cm2are recorded for NaOH- and H2O2-treated surfaces, respectively. H2O2is a better treatment reagent than NaOH. The mechanism of corrosion of both untreated and treated samples in the studied corrosive medium has been discussed. © 2022 American Chemical Society. All rights reserved

Determination of rhodamine b in cosmetics, candy, water, and plastic by a novel multiwalled carbon nanotube (mwcnt)@zinc oxide@magnetite nanocomposite for magnetic solid-phase extraction (mspe) with spectrophotometric detection

A new magnetic solid phase microextraction method (MSPE) was developed for the preconcentration of rhodamine B from plastics, cosmetics, and environmental samples before spectrophotometric analysis. A nanocomposite adsorbent containing ZnO nanoparticles (NPs), multi-walled carbon nanotubes (MWCNTs) and Fe3O4 nanoparticles was synthesized by a hydrothermal procedure. The new magnetic nanocomposite (MWCNTs@ZnO@Fe3O4) was characterized by Fourier-transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD), and scanning electron microscopy (SEM). The pH, sample volume, eluent type, adsorbent mass, influence of foreign species, and analyte-adsorbent and eluent contact times were optimized. The optimum pH was 3; adsorbent mass, 20 mg; sample volume, 50 mL; and eluent, 0.7 mL of ethanol. Recovery values exceeding 95% were obtained. The developed vortex assisted magnetic solid phase extraction method (VA-MSPE) was applied to practical analysis. The limits of detection (LOD) and quantification (LOQ) were 0.83 & mu;g L-1 and 2.77 & mu;g L-1, respectively. The addition/recovery experiments were carried on several water samples to demonstrate acceptable recoveries

Defect assisted optical limiting performance of hexagonal boron nitride nanosheets in aqueous suspension and PMMA nanocomposite films

Defect-assisted nonlinear absorption (NLA) and optical limiting (OL) performance of hexagonal boron nitride nanosheets (h-BNNS) in aqueous suspension and in polymethyl methacrylate matrix (PMMA) as nanocomposite films were studied using open-aperture Z-scan method. To evaluate the transmission in open-aperture Z-scan data, a theoretical model accounting one photon absorption (OPA), two photon absorption (TPA), free carrier absorption (FCA) and saturation of each process was considered. Defect-assisted NLA coefficients and saturation intensity thresholds were extracted from the fitting of the experimental results for 532 and 1064 nm pulse wavelengths. Strong defect-assisted NLA response of h-BNNS was observed while NLA at 532 nm was considerably stronger. This is attributed to the excitation of a greater number of defect states over a wider energy range. Our findings showed that h-BNNS/PMMA nanocomposite films feature highly required properties in OL applications and can function in OL applications in a wide spectral range (-200-1064 nm)