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A nanocomposite consisting of multiwalled carbon nanotubes wrapped with hydroxyapatite (HA/MWCNTs) was used in the construction of a new composite paste electrode using an ionic liquid as the binder. The stable surface in aqueous solutions as well as the high sorptive behaviors towards heavy metal ions and the favorable charge transfer make the electrode highly efficient especially for stripping or adsorptive analysis. The analysis of Pb2+ as a model of heavy metal ions has been performed. Good sensitivity, detection limit, selectivity and reproducibility were obtained for the suggested sensor. The linear range of the electrode response covered four orders of magnitude (1 nM-10 µM), in two linear ranges. The obtained detection limit for Pb2+ was 2×10−11 M. [ABSTRACT FROM AUTHOR]

Abstract: A rapid and convenient method is described for carbon nanotube (CNT) wrapping by in-situ hydroxyapatite (HA) formation via microwave (MW) assisted solid state metathesis reaction (SSM). The straightforward, solventless process requires no polyelectrolyte modification of CNTs and provides a uniform structure. Electrochemical impedance spectroscopy (EIS) revealed the surprisingly better charge transfer for the synthesized composite in comparison with the pristine multiwalled carbon nanotube (MWCNT). The interactions with biomolecules as well as the high sorptivity of HA with improved electrical properties, make MWCNT wrapped HA nanohybrid a favorable electrochemical platform. The proposed composite is promising for sensor technology and bioelectronic devices. [Copyright &y& Elsevier]

Metal-oxide nano-porous microstructures have shown high electrocatalytic activity toward hydrogen peroxide oxidation. In this paper, we establish the copper oxide (CuO) porous hollow structures via the hydrothermal method using pluronic F-127 as a surfactant. The electrochemical performance involves the oxidation between Cu(I) and Cu(II) at room temperature. For verifying the formation of the desired morphology of CuO porous hollow structures, the scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction spectroscopy and H2-temperature-programmed reduction (TPR) were applied. The synthesized samples are hollow microstructures which are formed by CuO nanoparticles. The achieved CuO hollow structures exhibit excellent H2O2 detection properties such as a very low detection limit of 141.1 nM, an extremely wide dynamic detection range of 50 nM–70 mM, an outstanding sensitivity of 13.7 µA µM−1 cm−2 and satisfactory stability in alkaline solution. The good tolerance toward interfering species, the satisfactory behaviour in repeatability and reproducibility and favourable stability verified the promising performance of the proposed sensor. The results of the study on sensing low levels of H2O2 concentrations by using a modified glassy carbon electrode as an optimized electrochemical sensor have been reported. The proposed synthesized nanostructures (CuO porous hollow structures) can be used as sensitive H2O2 biosensors. Essential characterizations and measurements have been performed. The constructed sensor shows acceptable electrocatalytic activity for detecting H2O2. High sensitivity, very low LOD, wide dynamic range, excellent tolerance toward interfering agents, favorable stability and satisfactory reproducibility and repeatability of the sensor have made it suitable for practical applications. [ABSTRACT FROM AUTHOR]

A high-performance non-enzymatic glucose sensor based on hybrid metal-oxides is proposed. Dumbbell-shaped double-shelled hollow nanoporous CuO/ZnO microstructures (CuO/ZnO-DSDSHNM) were prepared via the hydrothermal method using pluronic F-127 as a surfactant. This structure is studied by various physicochemical characterizations such as scanning electron microscopy, X-ray diffraction spectroscopy, inductively coupled plasma atomic emission spectroscopy, elemental mapping techniques, X-ray photoelectron spectroscopy, and transmission electron microscopy. This unique CuO/ZnO-DSDSHNM provides both a large surface area and an easy penetrable structure facilitating improved electrochemical reactivity toward glucose oxidation. The prepared CuO/ZnO-DSDSHNM was used over the glassy carbon electrode (GCE) as the active material for glucose detection and then coated by Nafion to provide the proposed Nafion/CuO/ZnO-DSDSHNM/GCE. The fabricated glucose sensor exhibits an extremely wide dynamic range from 500 nM to 100 mM, a sensitivity of 1536.80 µA mM−1 cm−2, a low limit of detection of 357.5 nM, and a short response time of 1.60 s. The proposed sensor also showed long-term stability, good reproducibility, favorable repeatability, excellent selectivity, and satisfactory applicability for glucose detection in human serum samples. The achieved high-performance glucose sensing based on Nafion/CuO/ZnO-DSDSHNM/GCE shows that both the material synthesis and the sensor fabrication methods have been promising and they can be used in future researches. [ABSTRACT FROM AUTHOR]

In the present study, an electrochemical glucose biosensor has been developed based on nano-copper oxide micro hollow spheres. The nano-copper oxide micro hollow spheres were synthesized via hydrothermal method using pluronic F-127 as a surfactant. For structural characterization of CuO hollow sphere structures, the scanning electron microscopy and X-ray diffraction spectroscopy were applied. The performance parameters of the sensor were improved by optimizing the modification process. The electrochemical characteristics of the proposed glucose biosensor were investigated by using cyclic voltammetry and chronoamperometry techniques in both 0.1 M and 1 M NaOH solutions. The results revealed that the proposed electrode has a wide dynamic range from 1 µM to 11.50 mM for glucose detection at 0.1 M NaOH solution which covers two linear ranges from 1 µM to 3 mM and from 3 mM to 11.50 mM. The sensitivities of the two linear ranges were obtained as 25.0 ± 0.8 µA·mM−1·cm−2 and 13.6 ±0.3 µA·mM−1·cm−2, respectively. An extremely wide linear range from 1 µM to 16 mM with a sensitivity of 35.2 ± 0.4 µA·mM−1 cm−2 was achieved for the 1 M NaOH solution. The sensor achieved a 1 µM practical lowest limit of detection which is an excellent low limit of detection at both NaOH concentrations compared to some important previously reported works. In addition, the good tolerance toward the interfering species and the satisfactory behavior in real sample analysis verified the promising performance of the proposed sensor. [ABSTRACT FROM AUTHOR]

Construction of a composite electrode based on a mixture of graphite and carbon nanotubes as a conductive phase and molecular wire as the binder has been proposed. Various components of the electrode as well as the conditions for preparation and pasting of the proposed electrode were optimized. The electrochemical characteristics of the electrode were evaluated using the redox behavior of various electrochemical probes via some electrochemical tests such as cyclic voltammetry and electrochemical impedance spectroscopy. To investigate the performance of the electrode, determination of dopamine was examined using the proposed electrode. The linear range for dopamine determination was determined as 1.0 × 10 − 8 to 4.5 × 10 − 5 M. The electrode was successfully applied in the analysis of dopamine in human blood serum as a real sample. [ABSTRACT FROM AUTHOR]

Electrospun carbon nanofibers (ECNFs) have many qualities that make them attractive for applications in various fields of technology. For many applications, it is necessary to modify the surface of CNFs by chemical functionalization. Here, a systematic functionalization of polyacrylonitrile (PAN)-based ECNFs by oxidation in concentrated nitric acid was examined. The effects of oxidation on the microstructural, electrical, and mechanical characteristics have been studied. The Fourier transform infrared spectroscopy results revealed the time-dependent functionalization of ECNFs. However, according to the scanning electron microscopy, there was no considerable change in the surface morphology of CNFs due to functionalization. The microstructures as well as electrical and mechanical properties were severely dependent on oxidation duration according to X-ray diffraction and Raman spectroscopies as well as conductivity and mechanical strength measurements, respectively. Increase in oxidation duration led to more structural disorders and noticeable decrease in electrical conductivity and mechanical strength. [ABSTRACT FROM AUTHOR]

A new electrocatalyst is introduced by loading palladium nanoparticles on the unique structured composite of hydroxyapatite and multiwalled carbon nanotubes. The structure and morphology of the designed electrocatalyst are characterized by X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The efficiency of the resulted nanostructure is explored toward the electrooxidation of some common alcohols in alkaline media. The electrooxidation of ethylene glycol (EG) is explored more extensively which provides a large peak current density (more than 1810 mA mg −1 Pd ). Surprisingly, the efficiency of oxidation is maintained even for relatively high concentrations of EG. In terms of the current density and the onset potential, significant improvements are observed for the proposed structure versus hydroxyapatite free catalyst. The high efficiency of the proposed electrocatalyst is explained via the presence of hydroxyl rich surface of hydroxyapatite which causes a more effective oxidation of alcohols over the loaded Pd nanoparticles. [ABSTRACT FROM AUTHOR]

Here, a novel nanostructured catalyst based on CuO included hallow mesoporous silica spheres (CuO-HMSS) was prepared for synthesis of 1,2,3-triazole compounds. The hallow silica spheres were synthesized via the hydrothermal procedure. The characterization of prepared catalyst was also performed applying several analysis techniques such as TEM and SEM, EDX, XRD, and ICP.Graphical Abstract: CuO active sites in a hollow mesoporous silica shell are stably and efficiently attainable for conversion of precursors to triazole compounds. [ABSTRACT FROM AUTHOR]

Abstract: Direct electrochemistry of hemoglobin (Hb) has been achieved by its direct immobilization on carbon ionic liquid electrode (CILE). CILE was immersed in a solution containing Hb and ionic liquid, octylpyridinium chloride ([OcPy][Cl]), to directly immobilize Hb on CILE. Cyclic voltammetry of modified electrode exhibited quasi-reversible peaks corresponding to Hb. The oxidation and reduction peak potentials of immobilized Hb in acetate buffer solution, pH 5.0 and at a scan rate of 0.1Vs−1 were obtained at about –150mV and –290mV, respectively. The average surface coverage of the electroactive Hb adsorbed on the electrode surface was calculated as 8.4×10−11 molcm−2. Hb retained its bioactivity on modified electrode and showed excellent electrocatalytic activity towards oxygen, hydrogen peroxide and nitrite. Hydrogen peroxide can be determined in the range of 1.0×10−4–5.0×10−3 M. [Copyright &y& Elsevier]