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A new electrochemical impedimetric sensor for direct detection of urea was designed and fabricated using nanostructured screen-printed electrodes (SPEs) modified with CuO/Co3O4 @MWCNTs. A facile and simple hydrothermal method was achieved for the chemical synthesis of the CuO/Co3O4 nanocomposite followed by the integration of MWCNTs to be the final platform of the urea sensor. A full physical and chemical characterization for the prepared nanomaterials were performed including Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact angle, scanning electron microscope (SEM) and transmission electron microscopy (TEM). Additionally, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to study the electrochemical properties the modified electrodes with the nanomaterials at different composition ratios of the CuO/Co3O4 or MWCNTs. The impedimetric measurements were optimized to reach a picomolar sensitivity and high selectivity for urea detection. From the calibration curve, the linear concentration range of 10−12–10−2 M was obtained with the regression coefficient (R2) of 0.9961 and lower detection limit of 0.223 pM (S/N = 5). The proposed sensor has been used for urea analysis in real samples. Thus, the newly developed non-enzymatic sensor represents a considerable advancement in the field for urea detection, owing to the simplicity, portability, and low cost-sensor fabrication. [ABSTRACT FROM AUTHOR]

A hydrogen peroxide (H2O2) sensor was developed based on core–shell gold@titanium dioxide nanoparticles and multi-walled carbon nanotubes modified glassy carbon electrode (Au@TiO2/MWCNTs/GCE). Core–shell Au@TiO2 material was prepared and characterized using a scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy, X-ray diffraction (XRD) and Zeta-potential analyzer. The proposed sensor (Au@TiO2/MWCNTs/GCE) was investigated electrochemically using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The analytical performance of the sensor was evaluated towards H2O2 using differential pulse voltammetry (DPV). The proposed sensor exhibited excellent stability and sensitivity with a linear concentration range from 5 to 200 µM (R2 = 0.9973) and 200 to 6000 µM (R2 = 0.9994), and a limit of detection (LOD) of 1.4 µM achieved under physiological pH conditions. The practicality of the proposed sensor was further tested by measuring H2O2 in human serum and saliva samples. The observed response and recovery results demonstrate its potential for real-world H2O2 monitoring. Additionally, the proposed sensor and detection strategy can offer potential prospects in electrochemical sensors development, indicative oxidative stress monitoring, clinical diagnostics, general cancer biomarker measurements, paper bleaching, etc. [ABSTRACT FROM AUTHOR]

Abstract: We report in this work the development of a novel capacitance electrochemical sensors based on silicon nitride substrate (Si3N4) chemically modified with a structure of Cobalt phthalocyanine, C,C,C,C‐tetracarboxylic acid‐Polyacrylamide (Co(II)Pc‐PAA). This sensitive layer was tested with and without magnetic nanoparticles (MNP) for perchlorate ( ClO 4 - ) detection. The developed chemical sensor with Si3N4/APTES‐MNP/Co(II)Pc‐PAA structure has shown a better performance when compared to the other structure based on Si3N4/Co(II)Pc‐PAA. Contact angle measurements (CAM) and atomic force microscopy (AFM) characterizations have been performed to characterize the functionalization of the chemical sensors surface. Under the optimized structure of the chemical sensor, electrochemical measurements were carried out using Mott‐Schottky analysis for ClO 4 - detection within the large range of 10−10 to 10−4 M with a very low detection limit of 2×10−10 M. The chemical sensor has demonstrated a high selectivity toward ClO 4 - when compared to other interfering anions such as Cl−, SO42−, and CO32−. The present capacitive chemical sensor is very promising for sensitive and rapid detection of ClO 4 - for environmental applications. [ABSTRACT FROM AUTHOR]

A novel electrochemical impedimetric sensor based on new copper phthalocyanine derivative-functionalized gold substrates has been developed. The modified transducers have been characterized using Fourier transform infrared spectroscopy and contact angle measurements. Under the optimized conditions in terms of polarization and frequency range, the developed sensor provided a large linear range from 1 × 10−10to 1 × 10−3 M with a detection limit of 9.48 × 10−11 M. To minimize the impedimetric sensor’s size, a microsensor based on modified gold microelectrodes was developed. Good sensitivity in the range from 1 × 10−8to 1 × 10−3 M with a limit of detection of 8.32 × 10−9 M was achieved. [ABSTRACT FROM PUBLISHER]

[Display omitted] • A label-free and disposable impedimetric immunosensor chips were manufactured. • Anti- Staphylococcus aureus antibody was chemically conjugated onto the AuNPs@Fe 3 O 4 nanocomposite. • Selective and sensitive detection and quantification of S. aureus in real food samples were achieved. Rapid analysis and early detection of food poisoning has become an important factor for the recognition and prevention of problems associated with food safety and public health. Accordingly, a number of different methods have been developed and applied for the detection and identification of S. aureus. However, these methods are not suitable for on-site applications as they are time-consuming and laborious. Thus, a label-free impedimetric immunosensor was constructed using the self-assembling monolayer formation of the lipoic at the AuNPs@Fe 3 O 4 -screen printed electrode. The formed layer of the lipoic acid supported the covalent immobilization of anti- S. aureus antibody as the selective bio-recognition element. As a result, a specific immune reaction between the whole pathogen cells and the immobilized antibody was monitored under optimized conditions. Electrochemical impedance spectroscopy along with other chemical assessments were used to verify the stepwise assembly of the immunosensor fabrication. Accordingly, the newly developed impedimetric immunosensor showed high sensitivity and selectivity towards the targeting bacterial strain with the limit of detection and limit of quantification of 0.10, and 0.34 CFU/mL, respectively. Eventually, the designed immunosensor was successfully implemented to analyze the S. aureus contamination in milk and meat samples, whereas the obtained results were validated. [ABSTRACT FROM AUTHOR]