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 Novel Molecularly Imprinted Quartz Crystal Microbalance Sensor Based on Erbium Molybdate Incorporating Sulfur-Doped Graphitic Carbon Nitride for Dimethoate Determination in Apple Juice Samples

Dimethoate (DIM) as an organophosphorus pesticide is widely utilized especially in the cultivation of vegetables and fruits due to its killing effect on harmful insects. However, unconscious use of DIM in large amounts can also cause serious health problems. For these reasons, rapid and reliable detection of DIM from food samples is significant. In this study, a novel quartz crystal microbalance (QCM) sensor based on erbium molybdate incorporating sulfur-doped graphitic carbon nitride (EM/S-g-C3N4) and a molecularly imprinting polymer (MIP) was designed for DIM detection in apple juice samples. Firstly, an EM/S-g-C3N4 nanocomposite with high purity was prepared under hydrothermal conditions at high temperatures over a long period of time. After the modification of the EM/S-g-C3N4 nanocomposite on a QCM chip, the polymerization solution including N,N'-azobisisobutyronitrile (AIBN) as an initiator, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, methacryloylamidoglutamic acid (MAGA) as a monomer, and DIM as an analyte was prepared. Then, the polymerization solution was dropped on an EM/S-g-C3N4 nanocomposite modified QCM chip and an ultraviolet polymerization process was applied for the formation of the DIM-imprinted polymers on the EM/S-g-C3N4 nanocomposite modified QCM chip. After the polymerization treatment, some characterization studies, including electrochemical, microscopic, and spectroscopic methods, were performed to illuminate the surface properties of the nanocomposite and the prepared QCM sensor. The values of the limit of quantification (LOQ) and the detection limit (LOD) of the prepared QCM sensor were as 1.0 × 10-9 M and 3.3 × 10-10 M, respectively. In addition, high selectivity, stability, reproducibility, and repeatability of the developed sensor was observed, providing highly reliable analysis results. Finally, thanks to the prepared sensor, it may be possible to detect pesticides from different food and environmental samples in the future.

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.

Fenpicoxamid-Imprinted Surface Plasmon Resonance (SPR) Sensor Based on Sulfur-Doped Graphitic Carbon Nitride and Its Application to Rice Samples

This research attempt involved the development and utilization of a newly designed surface plasmon resonance (SPR) sensor which incorporated sulfur-doped graphitic carbon nitride (S-g-C3N4) as the molecular imprinting material. The primary objective was to employ this sensor for the quantitative analysis of Fenpicoxamid (FEN) in rice samples. The synthesis of S-g-C3N4 with excellent purity was achieved using the thermal poly-condensation approach, which adheres to the principles of green chemistry. Afterwards, UV polymerization was utilized to fabricate a surface plasmon resonance (SPR) chip imprinted with FEN, employing S-g-C3N4 as the substrate material. This process involved the inclusion of N,N'-azobisisobutyronitrile (AIBN) as the initiator, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, methacryloylamidoglutamic acid (MAGA) as the monomer, and FEN as the analyte. After successful structural analysis investigations on a surface plasmon resonance (SPR) chip utilizing S-g-C3N4, which was imprinted with FEN, a comprehensive investigation was conducted using spectroscopic, microscopic, and electrochemical techniques. Subsequently, the kinetic analysis applications, namely the determination of the limit of quantification (LOQ) and the limit of detection (LOD), were carried out. For analytical results, the linearity of the FEN-imprinted SPR chip based on S-g-C3N4 was determined as 1.0-10.0 ng L-1 FEN, and LOQ and LOD values were obtained as 1.0 ng L-1 and 0.30 ng L-1, respectively. Finally, the prepared SPR sensor's high selectivity, repeatability, reproducibility, and stability will ensure safe food consumption worldwide.

The Electrochemical Detection of Ochratoxin A in Apple Juice via MnCO3 Nanostructures Incorporated into Carbon Fibers Containing a Molecularly Imprinting Polymer

A novel electrochemical sensor based on MnCO3 nanostructures incorporated into carbon fibers (MnCO3NS/CF), including a molecularly imprinting polymer (MIP), was developed for the determination of Ochratoxin A (OTA). In this study, a sensitive and selective sensor design for OTA detection was successfully performed by utilizing the selectivity and catalysis properties of MIP and the synthesized MnCO3NS/CF material at the same time. MnCO3 nanostructures incorporated into carbon fibers were first characterized by using various analytical techniques. The sensor revealed a linearity towards OTA in the range of 1.0 × 10-11-1.0 × 10-9 mol L-1 with a detection limit (LOD) of 2.0 × 10-12 mol L-1. The improved electrochemical signal strategy was achieved by high electrical conductivity on the electrode surface, providing fast electron transportation. In particular, the analysis process could be finished in less than 5.0 min without complex and expensive equipment. Lastly, the molecular imprinted electrochemical sensor also revealed superior stability, repeatability and reproducibility.

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 × 10^-11-1.0 × 10^-9 M and a low detection limit (LOD, 3.0 × 10^-12 M). BPA-imprinted polymer on GQDs/B-g-C₃N₄ nanocomposite also showed good stability, repeatability and selectivity in food samples.

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.

Carbendazim imprinted electrochemical sensor based on CdMoO4/g-C3N4 nanocomposite: Application to fruit juice samples

Carbendazim (CAR) as a fungicide is utilized for fruits and vegetables to provide diseases' control and the degradation of carbendazim having benzimidazole ring is slow. Herein, a molecularly imprinted electrochemical sensor based on CdMoO₄/g-C₃N₄ nanocomposite was prepared for CAR determination in fruit juice samples. Firstly, CdMoO₄/g-C₃N₄ nanocomposite with high yield was fabricated via one-pot in-situ hydrothermal approach including environmentally friendly method. Formation of CAR imprinted polymers was performed on CdMoO₄/g-C₃N₄ nanocomposite modified glassy carbon electrode (GCE) in presence of CAR as template and pyrrole (Py) as a monomer by cyclic voltammetry (CV) technique. Following the morphological, structural, and optical characterization of as-synthesized nanocomposite, the electrochemical techniques were also implemented to evaluate the electrochemical features of fabricated electrodes. The limit of quantification (LOQ) and limit of detection (LOD) values were calculated as 0.1 × 10^-10 M, and 2.5 × 10^-12 M, respectively in addition to satisfactory selectivity, stability, reproducibility and reusability. The findings revealed that the proposed CAR imprinted electrochemical sensor can be successfully employed in food safety.

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.

Identification of heavy metal ions from aqueous environment through gold, Silver and Copper Nanoparticles: An excellent colorimetric approach

Heavy metal pollution has become a severe threat to human health and the environment for many years. Their extensive release can severely damage the environment and promote the generation of many harmful diseases of public health concerns. These toxic heavy metals can cause many health problems such as brain damage, kidney failure, immune system disorder, muscle weakness, paralysis of the limbs, cardio complaint, nervous system. For many years, researchers focus on developing specific reliable analytical methods for the determination of heavy metal ions and preventing their acute toxicity to a significant extent. The modern researchers intended to utilize efficient and discerning materials, e.g. nanomaterials, especially the metal nanoparticles to detect heavy metal ions from different real sources rapidly. The metal nanoparticles have been broadly utilized as a sensing material for the colorimetric detection of toxic metal ions. The metal nanoparticles such as Gold (Au), Silver (Ag), and Copper (Cu) exhibited localized plasmon surface resonance (LPSR) properties which adds an outstanding contribution to the colorimetric sensing field. Though, the stability of metal nanoparticles was major issue to be exploited colorimetric sensing of heavy emtal ions, but from last decade different capping and stabilizing agents such as amino acids, vitmains, acids and ploymers were used to functionalize the metal surface of metal nanoparticles. These capping agents prevent the agglomeration of nanoparticles and make them more active for prolong period of time. This review covers a comprehensive work carried out for colorimetric detection of heavy metals based on metal nanoparticles from the year 2014 to onwards.

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-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.

Recent advances in developing optical and electrochemical sensors for analysis of methamphetamine: A review

Recognition of misused stimulant drugs has always been a hot topic from a medical and judicial perspective. Methamphetamine (MAMP) is an addictive and illegal drug that profoundly affects the central nervous system. Like other illicit drugs, the detection of MAMP in biological and street samples is vital for several organizations such as forensic medicine, anti-drug headquarters and diagnostic clinics. By emerging nanotechnology and exploiting nanomaterials in sensing applications, a great deal of attention has been given to the design of analytical sensors in MAMP tracing. For the first time, this study has briefly reviewed all the optical and electrochemical sensors in MAMP detection from earlier so far. How various receptors with engineering nanomaterials allow developing novel approaches to measure MAMP have been studied. Fundamental concepts related to optical and electrochemical recognition assays in which nanomaterials have been used and relevant MAMP sensing applications have been comprehensively covered. Challenges, opportunities and future outlooks of this field have also been discussed at the end.

Effects of silver nanoparticles added into polyurea coating on sulfate-reducing bacteria activity and electrochemical properties; an environmental nano-biotechnology investigation

In the present work, Ag nanoparticles were added to polyurea coating in order to improve its antibacterial and electrochemical properties in sulfide-reducing bacteria-containing media. To this end, Ag nano-powder was mixed with two component polyuria, and then the antibacterial behavior of the nanocomposite coating was studied in sulfate-reducing bacteria (SRB)-containing medium. The results revealed the inhibitory effects of nanocomposite coating on the formation of SRB biofilms on the samples. Moreover, the SRB population decreased in contact with the Ag nanoparticles-mixed coating over 7 days. Investigation of the growth and activity of the bacteria represented the effective antibacterial properties of Ag nanoparticles in the polyurea matrix. Furthermore, EIS (electrochemical impedance spectroscopy) measurements indicated that the corrosion properties of the nanocomposite coating improved considerably over 7 days. The coating resistance increased 2 times by adding Ag nanoparticles after 1 day and 3.3 times after 7 days. In accordance with the same results, the charge transfer resistance increased 1.5 times and 1.1 times by adding Ag nanoparticles after 1 day and 7 days, respectively. The improvement in the protective properties of the nanocomposite coating are reflected in the increase in both film and charge transfer resistance.

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 Cd_0.5Zn_0.5S/d-Ti₃C₂T_x 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 hc-g-C₃N₄@CDs surface. Then, the conjugation of the second antibody to Cd_0.5Zn_0.5S/d-Ti₃C₂T_x MXene was carried out by strong π-π 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 and selective electrochemical detection of bisphenol A based on SBA-15 like Cu-PMO modified glassy carbon electrode

This work reports the electrochemical detection of bisphenol A (BPA) using a novel and sensitive electrochemical sensor based on the Cu functionalized SBA-15 like periodic mesoporous organosilica-ionic liquid composite modified glassy carbon electrode (Cu@TU-PMO/IL/GCE). The structural morphology of Cu@TU-PMO is characterized by X-ray powder diffraction (XRD), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), Field emission scanning electron microscopy (FE-SEM), and Brunauer-Emmett-Teller (BET). The catalytic activity of the modified electrode toward oxidation of BPA was interrogated with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in phosphate buffer solution (pH 7.0) using the fabricated sensor. The electrochemical detection of the analyte was carried out at a neutral pH and the scan rate studies revealed that the sensor was stable. Under the optimal conditions, a linear range from 5.0 nM to 2.0 µM and 4.0 to 500 µM for detecting BPA was observed with a detection limit of 1.5 nM (S/N = 3). The sensor was applied to detect BPA in tap and seawater samples, and the accuracy of the results was validated by high-performance liquid chromatography (HPLC). The proposed method provides a powerful tool for the rapid and sensitive detection of BPA in environmental samples.

A novel electrochemical lung cancer biomarker cytokeratin 19 fragment antigen 21-1 immunosensor based on Si3N4/MoS2 incorporated MWCNTs and core-shell type magnetic nanoparticles

Lung cancer is one of deadliest and most life threatening cancer types. Cytokeratin 19 fragment antigen 21-1 (CYFRA 21-1) is a significant biomarker for the diagnosis of non-small cell lung cancer (NSCLC). Due to these reasons, a novel electrochemical immunosensor based on a silicon nitride (Si3N4)-molybdenum disulfide (MoS2) composite on multi-walled carbon nanotubes (Si3N4/MoS2-MWCNTs) as an electrochemical sensor platform and core-shell type magnetic mesoporous silica nanoparticles@gold nanoparticles (MMSNs@AuNPs) as a signal amplifier was presented for CYFRA21-1 detection in this study. Capture antibody (Ab1) immobilization on a Si3N4/MoS2-MWCNT modified glassy carbon electrode (Si3N4/MoS2-MWCNTs/GCE) was firstly successfully performed by stable electrostatic/ionic interactions between the -NH2 groups of the capture antibody and the polar groups of Si3N4/MoS2. Then, specific antibody-antigen interactions between the electrochemical sensor platform and the signal amplifier formed a novel voltammetric CYFRA21-1 immunosensor. The prepared composite materials and electrochemical sensor surfaces were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A linearity range of 0.01-1.0 pg mL-1 and a low detection limit (LOD) of 2.00 fg mL-1 were also obtained for analytical applications. Thus, the proposed immunosensor based on Si3N4/MoS2-MWCNTs and MMSNs@AuNPs has great potential for medical diagnosis of lung cancer.

A novel electrochemical aflatoxin B1 immunosensor based on gold nanoparticle-decorated porous graphene nanoribbon and Ag nanocube-incorporated MoS2 nanosheets

The accurate and precisive monitoring of aflatoxin B1 (AFB1), which is one of the most hazardous mycotoxins, especially in agricultural products, is significant for human and environmental health.

Sustainable electrode material for high-energy supercapacitor: biomass-derived graphene-like porous carbon with three-dimensional hierarchically ordered ion highways

Biomass-derived carbonaceous materials have been deemed to be one of the up-and-coming electrode materials for high-performance energy storage systems due to their cost-neutral abundant resources, sustainable nature, easy synthesis methods, and environmentally benign features. In this work, various graphene-like porous carbon networks (GPCs) with three-dimensional (3D) hierarchically ordered "ion highways" have been synthesized by the carbonization/activation of orange-peel wastes for use as an electrode material in high-energy supercapacitors. The porous structures and surface morphologies of the GPCs were rationally fine-tuned as a function of the activation agent ratio. The prepared GPCs offered superior specific surface area in addition to a 3D porous structure with a fine-tuned pore size distribution. The electrochemical behaviors of all the GPCs were evaluated in 6.0 M KOH aqueous electrolyte via a three-electrode electrochemical setup. Owing to their synergistic characteristics, including superior specific surface area (1150 m2 g-1), large pore volume, and fine-tuned 3D porous architecture, GPC-3.0 (synthesized with a KOH : GPC ratio of 3.0, by wt.) exhibited the best capacitive behavior amongst the studied GPCs. The 3D hierarchically ordered architecture acts like well-designed ion highways that boost electron transportation, thereby enhancing electrochemical energy storage. A coin-cell-type symmetrical supercapacitor based on GPC-3.0 was tested in both 1.0 M Na2SO4 (salt-in-water) and 12.0 m NaNO3 (water-in-salt) electrolytes. The supercapacitor cell based on the water-in-salt electrolyte offered a wide operating voltage of 2.3 V. The obtained energy density and power density values were comparable to those of commercial high-performance electrical double-layer capacitors. Such notable findings will shed light on next-generation high-rate electrochemical energy storage systems based on biomass-derived carbonaceous materials.

Amperometric galectin-3 immunosensor-based gold nanoparticle-functionalized graphitic carbon nitride nanosheets and core-shell Ti-MOF@COFs composites

Antigen galectin-3 (GL-3), a member of β-galactoside proteins indicates cardiac fibrosis and is a significant biomarker for monitoring heart failure risk and death risk. In this study, a novel sensitive amperometric method for antigen GL-3 detection is developed based on gold nanoparticle-functionalized graphitic carbon nitride nanosheets (g-C₃N₄@Au NPs) as the sensor platform and Ti-based metal organic framework (Ti-MOF, NH₂-MIL-125)@covalent organic frameworks (COFs) composite for the signal amplification. The Ti-MOF@COF composite not only facilitates the penetration of antibody proteins into pore channels, but also the highly stable antigen-antibody interactions. The prepared sensor platform and signal amplification material are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) method, X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The amperometric technique is utilized to achieve antigen GL-3 detection in plasma samples. The immunosensor demonstrates a wide linearity range (0.0001-20.0 ng mL^-1) and a low detection limit (0.025 pg mL^-1). Finally, the prepared immunosensor shows high stability and selectivity under optimum conditions.

A novel sandwich-type SERS immunosensor for selective and sensitive carcinoembryonic antigen (CEA) detection

Monitoring the malignant tumors via cancer biomarkers is very significant process. Nonetheless, the practical clinical applications need selective and sensitive analytical methods/techniques. In this study, a novel sandwich type immunosensor based on surface-enhanced raman scattering (SERS) was presented including 4-mercaptobenzoic acid labeled MoS₂ nanoflowers@Au nanoparticles (MoS₂ NFs@Au NPs/ MBA) as CEASERS tag and Fe₃O₄@Au nanoparticles functionalized delaminated Ti₃C₂T_x MXene (Fe₃O₄ NPs@Au NPs/d-Ti₃C₂T_X MXene) as SERS magnetic supporting substrate for carcinoembryonic antigen (CEA) detection. Especially, the determination of single molecule by using SERS method enables early diagnosis of major diseases. In addition, this technique can be utilized for multiplex analyzes owing to narrow well-resolved peaks. The prepared CEASERS tag and SERS magnetic supporting substrate were characterized by scanning electron microscope (SEM), x-ray diffraction (XRD) method, x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FTIR). A linearity of 0.0001-100.0 ng mL^-1 was observed with high sensitivity. Finally, sandwich type immunosensor demonstrated good selectivity and stability for target CEA recognition in plasma sample.

Molecularly imprinted QCM sensor based on delaminated MXene for chlorpyrifos detection and QCM sensor validation

Chlorpyrifos (CHL) is one of the most frequently used broad-spectrum organophosphate insecticides.

Development of Novel Nanocomposites Based on Graphene/Graphene Oxide and Electrochemical Sensor Applications

Background:

Until now, several methods such as spectroscopic methods and chromatographic techniques have been developed for the determination of biomolecules, drug or heavy metals. Nevertheless, the crucial interference problems are present in these methods. Due to these reasons, more sensitive, favorable portability, low-cost, simple and selective sensors based on nanocomposites are needed in terms of health safety. In the development of electrochemical nanosensor, the nanomaterials such as graphene/graphene oxide, carbon and carbon nitride nanotubes are utilized to improve the sensitivity.

Objective:

The nanomaterials such as graphene/graphene oxide, carbon and carbon nitride nanotubes have important advantages such as high surface area, electrical conductivity, thermal and mechanical stability. Hence, we presented the highly selective methods for sensitive sensor applications by molecular imprinting technology in literature. This technology is a polymerization method around target molecule. This method provides the specific cavities to analyte molecule on the polymer surface. Hence, the selective sensor is easily created for biomedical and other applications. Novel electrochemical sensors based on nanocomposite whose surface is coated with Molecular Imprinting Polymer (MIP) are developed and then applied to the selective and sensitive detection in this study. Until now, we have presented several reports about nanocomposite based sensor with MIP.

Simultaneous determination of β-agonists on hexagonal boron nitride nanosheets/multi-walled carbon nanotubes nanocomposite modified glassy carbon electrode

β-Agonists are illegally consumed in various products such as food and animal and effect the nutrition distribution owing to change of body fat. In addition, they result in acute poisoning and several symptoms such as muscular tremors and nervousness. A new electrochemical approach based on two-dimensional hexagonal boron nitride (2D-hBN) nanosheets decorated functionalized multi-walled carbon nanotubes (f-MWCNTs) was presented for simultaneous determination of β-agonists such as phenylethanolamine A (PEA), clenbuterol (CLE), ractopamine (RAC) and salbutamol (SAL) in urine samples. X-ray diffraction (XRD) method, Raman spectroscopy, scanning electron microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used characterizations of nanomaterials. After that, 2D-hBN/f-MWCNTs nanocomposite modified glassy carbon electrode (GCE) was prepared for simultaneous determination of β-agonists. 1.0 × 10^-12-1.0 × 10^-8 M and 1.0 × 10^-13 M were founded as the linearity range and the detection limit (LOD) for PEA, CLE, RAC and SAL. Finally, the prepared electrochemical sensor was used for urine sample analysis in presence of ascorbic acid (AA) and uric acid (UA).

Development of cardiac troponin-I biosensor based on boron nitride quantum dots including molecularly imprinted polymer

The cardiac Troponin-I (cTnI) is one of the subunits of cardiac troponin complexes and a pivotal biochemical marker of acute myocardial infarction (AMI). Due to its myocardial specificity, cTnI is widely used for the diagnosis of AMI diseases. In this study, a novel imprinted biosensor approach based on boron nitride quantum dots (BNQDs) was presented for cTnI detection in plasma samples. Various characterization methods such as scanning electron microscope (SEM), transmission electron microscope (TEM), x-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for all characterizations of nanomaterials. After the characterization analysis, cTnI imprinted electrode was developed in the presence of 100.0 mM pyrrole containing 25.0 mM cTnI. After that, the analytical studies of cTnI in plasma samples were performed by using cTnI imprinted biosensor. The results of the study have revealed that 0.01-5.00 ng mL^-1 and 0.0005 ng mL^-1 were found as the linearity range and the detection limit (LOD). Moreover, the selectivity of cTnI imprinted glassy carbon electrode (GCE) was investigated for plasma sample analysis in the presence of other nonspecific and specific proteins including cardiac myoglobin (MYG), bovine serum albumin (BSA) and cardiac troponin T (cTnT), respectively. Furthermore, the prepared biosensor was examined in terms of stability, repeatability, reproducibility and reusability. Finally, the imprinted biosensor was applied to the plasma samples having high recovery.