Electrochemical determination of fenitrothion pesticide based on ultrathin manganese oxide nanowires/molybdenum titanium carbide MXene ionic nanocomposite and molecularly imprinting polymer.

A novel molecularly imprinted electrochemical sensor is presented based on one-dimensional ultrathin manganese oxide nanowires/two-dimensional molybdenum titanium carbide MXene (MnO2NWs@Mo2TiC2 MXene) for fenitrothion (FEN) determination. After the synthesis of MnO2NWs@Mo2TiC2 MXene ionic nanocomposite was successfully completed with a facile hydrothermal and the pillaring methods, a new type molecular imprinted electrochemical sensor based on MnO2NWs@Mo2TiC2 MXene was constructed with cyclic voltammetry (CV) polymerization including pyrrole monomer and FEN target molecule. After the characterization studies including spectroscopic, electrochemical and microscopic methods, the analytical applications of the prepared sensor were performed. A linearity of 1.0×10-9-2.0×10-8 mol L-1 was obtained and the values of the quantification limit (LOQ) and the detection limit (LOD) were 1.0×10-9 mol L-1 and 3.0×10-10 mol L-1, respectively. The studies of selectivity, stability and reproducibility of the constructed sensor based on MnO2NWs@Mo2TiC2 nanocomposite and molecularly imprinting polymer (MIP) were carried out in detail. Finally, the developed sensor was applied to white flour samples with the values close to 100%.

A nivalenol imprinted quartz crystal microbalance sensor based on sulphur-incorporating cobalt ferrite and its application to rice samples.

Nivalenol as a mycotoxin pesticide is toxic to humans and animals and causes major health problems including hemorrhage, anemia, and vomiting. Thus, the need for fast and reliable analytical systems in terms of the management of health risks resulting from nivalenol exposure has increased in recent years. The aim of this study involved a novel molecularly imprinted quartz crystal microbalance sensor preparation based on sulphur-incorporating cobalt ferrite for nivalenol detection in rice samples. For this aim, cobalt ferrite and sulfur incorporated cobalt ferrite were successfully synthesized by sol-gel and calcination methods, respectively. Then, nivalenol imprinted quartz crystal microbalance chips based on cobalt ferrite and sulfur incorporated cobalt ferrite were prepared by an ultraviolet polymerization technique including N,N'-azobisisobutyronitrile as the initiator, ethylene glycol dimethacrylate as the cross-linker, methacryloylamidoglutamic acid as the monomer, and nivalenol as the analyte. After some spectroscopic, electrochemical and microscopic characterization studies, the developed sensor was applied to rice grain samples for the determination of nivalenol. The linearity of the prepared sensor was observed to be 1.0-10.0 ng L-1 and the limit of quantification and detection limit were found to be 1.0 and 0.33 ng L-1, respectively. Finally, the high selectivity, repeatability, and stability of the prepared sensor based on sulphur-incorporating cobalt ferrite and a molecularly imprinted polymer can ensure safe food consumption worldwide.

A novel electrochemical detection method for butylated hydroxyanisole (BHA) as an antioxidant: a BHA imprinted polymer based on a nickel ferrite@graphene nanocomposite and its application.

A novel electrochemical detection method based on a nickel ferrite@graphene (NiFe2O4@Gr) nanocomposite-containing molecularly imprinted polymer (MIP) was developed for the sensitive determination of butylated hydroxyanisole (BHA). After successful completion of the nanocomposite production under hydrothermal conditions, the NiFe2O4@Gr nanocomposite and a novel molecularly imprinted sensor based on the NiFe2O4@Gr nanocomposite were characterized using microscopic, spectroscopic and electrochemical techniques. According to the characterization results, the synthesis of the core-shell type NiFe2O4@Gr nanocomposite with high purity and efficiency has been proved to be successful. After successful modification of a cleaned glassy carbon electrode (GCE) with the NiFe2O4@Gr nanocomposite, analytical applications were started with the prepared BHA printed GCE. This novel molecularly imprinted electrochemical sensor for BPA detection demonstrated a linearity of 1.0 × 10-11-1.0 × 10-9 M and a low detection limit (LOD, 3.0 × 10-12 M). In addition, the BHA imprinted polymer based on the NiFe2O4@Gr nanocomposite also exhibited excellent selectivity, stability, reproducibility and reusability performances in flour analysis.

A novel molecular imprinted QCM sensor based on MoS2NPs-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 (MoS2NPs)-multiwalled carbon nanotube (MWCNT) nanocomposite (MoS2NPs-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.

Graphene quantum dots incorporated NiAl2O4 nanocomposite based molecularly imprinted electrochemical sensor for 5-hydroxymethyl furfural detection in coffee samples.

5-Hydroxymethyl furfural (HMF) is an intermediate produced by dehydrating sugars, such as fructose, sucrose, and glucose, in an acidic medium or during the Maillard reaction. It also occurs due to the storage of sugary foods at inappropriate temperatures. In addition, HMF is seen as a quality criterion in products. In this study, a novel molecularly imprinted electrochemical sensor based on graphene quantum dots incorporated NiAl2O4 (GQDs-NiAl2O4) nanocomposite was presented for the selective determination of HMF in coffee samples. Various microscopic, spectroscopic, and electrochemical methods were carried out for the structural characterizations of GQDs-NiAl2O4 nanocomposite. The molecularly imprinted sensor was prepared by multi-scanning using cyclic voltammetry (CV) in the presence of 100.0 mM pyrrole monomer and 25.0 mM HMF. After method optimization, the sensor revealed linearity towards HMF in the range of 1.0-10.0 ng L-1 with a detection limit (LOD) of 0.30 ng L-1. The developed MIP sensor's high repeatability, selectivity, stability, and fast response ability can provide reliable HMF detection in beverages, such as coffee, which is heavily consumed.

Electrochemical α-fetoprotein immunosensor based on Fe3O4NPs@covalent organic framework decorated gold nanoparticles and magnetic nanoparticles including SiO2@TiO2.

The early diagnosis of major diseases such as cancer is typically a major issue for humanity. Human α-fetoprotein (AFP) as a sialylated glycoprotein is of approximately 68 kD molecular weight and is considered to be a key biomarker, and an increase in its level indicates the presence of liver, testicular, or gastric cancer. In this study, an electrochemical AFP immunosensor based on Fe3O4NPs@covalent organic framework decorated gold nanoparticles (Fe3O4 NPs@COF/AuNPs) for the electrode platform and double-coated magnetic nanoparticles (MNPs) based on SiO2@TiO2 (MNPs@SiO2@TiO2) nanocomposites for the signal amplification was fabricated. The immobilization of anti-AFP capture antibody was successfully performed on Fe3O4 NPs@COF/AuNPs modified electrode surface by amino-gold affinity, while the conjugation of anti-AFP secondary antibody on MNPs@SiO2@TiO2 was achieved by the electrostatic/ionic interactions. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) analysis, cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS) techniques were used to characterize the nanostructures in terms of physical and electrochemical features. The limit of detection (LOD) was 3.30 fg mL-1. The findings revealed that the proposed electrochemical AFP immunosensor can be effectively used to diagnose cancer.

A novel paraoxon imprinted electrochemical sensor based on MoS2NPs@MWCNTs and its application to tap water samples.

Organophosphorus pesticides are widely utilized in agricultural fertility. However, their long-term accumulations result in serious damage to human health and ecological balance. Paraoxon (PAR) can block acetylcholinesterase in the human body, resulting in death. Thus, in this study, a molecularly imprinted electrochemical PAR sensor based on multiwalled carbon nanotubes (MWCNTs)/molybdenum disulfide nanoparticles (MoS2NPs) nanocomposite (MoS2NPs@MWCNTs) was proposed for selective tap water determination. A hydrothermal fabrication approach was firstly implemented to prepare MoS2NPs@MWCNTs nanocomposite. Afterwards, the formation of PAR imprinted electrochemical electrode was performed on nanocomposite modified glassy carbon electrode (GCE) in presence of PAR as template and pyrrole (Py) as a monomer by cyclic voltammetry (CV) technique. Just after determining the physicochemical features of as-fabricated nanostructures by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), Raman spectroscopy, and atomic force microscopy (AFM), the electrochemical behavior of the fabricated sensors was determined through CV, differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The suggested imprinted electrode provided the acceptable limit of quantification (LOQ) and limit of detection (LOD) values of 1.0 × 10-11 M, and 2.0 × 10-12 M, respectively. As a consequence, the proposed PAR imprinted electrochemical sensor can be offered for the determining safe tap water and its utility.

Electrochemical neuron-specific enolase (NSE) immunosensor based on CoFe2O4@Ag nanocomposite and AuNPs@MoS2/rGO.

Small cell lung cancer (SCLC) is highly associated with the risk of early metastasis. Neuron-specific enolase (NSE), a biomarker of SCLC, is directly related to tumor burden and early diagnosis. This biomarker exists in nerve tissue and neuroendocrine tissue. In this study, an electrochemical NSE immunosensor based on gold nanoparticles modified molybdenum disulfide and reduced graphene oxide (AuNPs@MoS2/rGO) as the electrode platform and CoFe2O4@Ag nanocomposite as the signal amplification was developed. The immobilization of anti-NSE capture antibody was successfully performed on AuNPs@MoS2/rGO modified electrode surface by amino-gold affinity and the conjugation of anti-NSE secondary antibody on CoFe2O4@Ag nanocomposite was successfully completed by the strong esterification reaction. The final immunosensor was designed by the specific interactions of electrode platform and signal amplification. The fabricated nanocomposites and electrochemical immunosensor were characterized by both physicochemical characterization techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), and electrochemical methods such as cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS). The quantification limit (LOQ) and the determination limit (LOD) were computed to be 0.01 pg mL-1 and 3.00 fg mL-1, respectively. In brief, it can be speculated that the constructed electrochemical NSE immunosensor can be successfully utilized in the early diagnosis for lung cancer.

Sensitive sandwich-type electrochemical SARS-CoV­2 nucleocapsid protein immunosensor.

A sensitive and fast sandwich-type electrochemical SARS-CoV­2 (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-C3N4/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-C3N4/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 µL) took just 30 min and yielded a detection limit (LOD) of 3.00 fg mL-1, making it an effective tool for point-of-care COVID-19 testing.