[en] The authors describe the synthesis of a nanocomposite consisting of Fe₃O₄ nanoparticles, polypyrrole and graphene oxide (Fe₃O₄/PPy/GO), and its application to voltammetric sensing of hydrazine. The nanocomposite can be synthesized by combining chemical oxidative polymerization and co-precipitation. Fe(III) ion is employed as both the oxidant for pyrrole and as a precursor of Fe₃O₄. The nanocomposite was characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). TEM observations revealed that large numbers of Fe₃O₄ are homogeneously and densely distributed. The Fe₃O₄/PPy/GO composite was placed in a glassy carbon electrode, and the resulting sensor, best operated at around 0.2 V (vs. SCE) exhibited excellent response to dissolved hydrazine over the 5.0 μM to 1.3 mM concentration range, a sensitivity of 449.7 μA mM⁻¹ cm⁻² and a low detection limit of 1.4 μM (at an S/N ratio of 3). < Image>.

[en] Inspired by water-soluble sacrificial template strategies, we have synthesized crystals of silver chloride (AgCl) consisting of a well-defined cubic exterior and a hollow interior. In a next step, silver nanoparticles (Ag-NPs) were attached to the hollow AgCl crystals via a photo-reduction process. The growth mechanism of the resulting Ag-AgCl nanoboxes is discussed, and their morphology and composition characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The electrochemical investigation of the nanoboxes deposited on a glassy carbon electrode revealed its excellent property in terms of electrocatalytic reduction H₂O₂ at a potential as low as −0.1 V and with fast response (∼1 s). The modified GCE responds to of H₂O₂ in the concentration range from 5.0 μM to 15.0 mM, the sensitivity is 88.8 μA mM⁻¹ cm⁻², and the detection limit is 1.7 μM at a signal-to-noise ratio of 3. The sensor also displays excellent selectivity and stability. (author)

[en] The authors describe a method to anchor gold nanoparticles (AuNPs) on carboxy-functionalized multi-walled carbon nanotubes (c-MWCNTs) utilizing chitosan as dispersing and protective agent. A sensor for the simultaneous determination of hydroquinone and catechol was then fabricated by placing this nanocomposite on a glassy carbon electrode (GCE). The morphology and composition of the nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction. The electrochemical behavior of the modified GCE was studied by electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. The modified GCE exhibits good electrooxidative activity towards hydroquinone and catechol and therefore was used for simultaneous determination of both, with typical voltages of 30 and 130 mV (vs. SCE). A linear reponse is found for the 0.5 μM to 1.5 mM hydroquinone concentration range, and for the 5.0 μM to 0.9 mM catechol concentration range. The respective lower detection limits are 0.17 and 0.89 μM (at an S/N ratio of 3). The sensitivity is 644.44 μA mM⁻¹ cm⁻² for hydroquinone and 770.98 μA mM⁻¹ cm⁻² for catechol. .

[en] A sandwich structured nanocomposite consisting of mildly reduced graphene oxide modified with silver nanoparticles supported on Co_3O_4 was synthesized and used for fabricating a nonenzymatic sensor for H_2O_2. The morphology and composition of the nanocomposite was characterized by transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction and FTIR. The composite was placed on a glassy carbon electrode which then displayed excellent performance in terms of electroreduction of H_2O_2. The H_2O_2 sensor, if operated at pH 7.4 at a working potential of 0.4 V (vs. SCE) has the following features: (a) linearity in the 0.1 μM to 7.5 mM concentration range; (b) a sensitivity of 146.5 μA∙mM"-"1∙cm"-"2; (c) a 35 nM detection limit at a signal-to-noise ratio of 3, and (d) a response time of 2 s. The sensor is long-term stable, well reproducible and selective. (author)

[en] A composite material obtained by ultrasonication of graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) was loaded with manganese dioxide (MnO₂), poly(diallyldimethylammonium chloride) and gold nanoparticles (AuNPs), and the resulting multilayer hybrid films were deposited on a glassy carbon electrode (GCE). The microstructure, composition and electrochemical behavior of the composite and the modified GCE were characterized by transmission electron microscopy, Raman spectra, energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The electrode induces efficient electrocatalytic oxidation of dopamine at a rather low working voltage of 0.22 V (vs. SCE) at neutral pH values. The response is linear in the 0.5 μM to 2.5 mM concentration range, the sensitivity is 233.4 μA·mM^-1·cm^-2, and the detection limit is 0.17 μM at an SNR of 3. The sensor is well reproducible and stable. It displays high selectivity over ascorbic acid, uric acid and glucose even if these are present in comparable concentrations. (author)

[en] The formation of neodymium (III) hexacyanoferrate (II) (NdHCF) nanoparticles (NPs) on the surface of carbon-paste electrode induced by enzymatic reaction was described and characterized. The conditions for biosensing of glucose were optimized through various experiments. Results showed that the optimized condition of the glucose oxidase (GOx)-induced NdHCF NPs for the biosensing of glucose were 2.0 mM Nd³⁺, 40.0 mM Fe(CN)₆^3- and 20 μg/mL GOx. The biocatalyzed generation of NdHCF NPs in the presence of O₂/glucose and GOx enabled the development of an electrochemical biosensor for glucose. Furthermore, this system avoids the interferences from other species for the biosensing of glucose

[en] In present work, typical nanocomposites were synthesized, composed of polypyrrole nanotubes and palladium nanocubes. The morphology and composition of the nanocomposites were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The obtained data indicated that the polypyrrole nanotubes and palladium nanocubes were well dispersed with the uniform size about 180 nm and 12.5 nm, respectively. Then the nanocomposites were modified on a glassy carbon electrode to build an electrochemical sensor of dopamine. The data of electrochemical experiments showed that the sensor has an excellent catalytic ability to detect dopamine in a linear range from 1.0 µM to 3.0 mM with a detection limit of 0.33 µM at a signal-to-noise ratio of 3, a sensitivity of 228.56 µA mM⁻¹ cm⁻² and a response time of 3 s. The process might provide a special idea to construct a sensor or for application in other fields.

[en] Thulium hexacyanoferrate (TmHCF) nanoparticles (NPs) were in situ synthesized within the chitosan film on the electrode surface by a biocatalyzed reaction. The properties of the obtained nanoparticles are characterized with scanning electron microscope (SEM) and energy-dispersive X-ray (EDX). The optimized conditions for the formation of TmHCF NPs were 16 mM Fe(CN)₆^3- and 1.5 mM Tm³⁺ with an accumulation time of 20 min. Based on process of in situ synthesis of TmHCF NPs, a novel biosensor for glucose was designed, and there is a linear relationship between the current response of TmHCF NPs and glucose concentration. The linear range for glucose detection was 0.02-0.4 mM (r = 0.9975, n = 5) and 0.4-13.6 mM (r = 0.9935, n = 10) and the detection limit was 6 μM at a signal-to-noise ratio of 3.

[en] When free diffusing ammonia begins to dissolve into a reaction precursor solution, a gas/liquid interface formed. Three-dimensional (3D) network iron oxide (i-Fe₃O₄) was synthesized at the interface without the protection of any inert gas at room temperature. This is the first time ammonia vapor method be used to prepare nano iron oxide at a gas/liquid interface. Scanning electron microscope results of it indicated that 3D network i-Fe₃O₄ is an assembly of nanowires and its properties are quite similar to spherical Fe₃O₄ nanoparticle. Energy dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectra were used to confirm the presence of Fe₃O₄. Electrochemical methods were employed to investigate the sensing properties for the electrocatalytic oxidation of hydrazine hydrate at the i-Fe₃O₄/glassy carbon electrode (GCE). The sensor displayed a response time less than 2 s, a sensitivity of 152 μA mM⁻¹ cm⁻² and the linearity of 0.1 to 600 μM with a detection limit of 0.05 μM (S/N = 3).

[en] Graphical abstract: Cyclic voltammograms of Ni–MWNTs/GCE at different concentrations of glucose. Highlights: ► Ni –MWNT nanohybrid film was successfully synthesized and characterized by SEM and EDS. ► The mechanism of glucose at Ni –MWNT nanohybrid film was evaluated and the upper glucose concentration limit produced a linear response of 17.5 mM. ► Simple of preparation and good analytical response made nanohybrid films a promising sensor material for non-enzymatic glucose sensing in routine analysis. - Abstract: In this paper, nickel was combined with multi-walled carbon nanotubes (Ni–MWNTs) to fabricate nanohybrid films on a conventional glassy carbon electrode using simultaneous electrodeposition of NiCl₂ and the MWNTs in ionic liquids (ILs). The morphologies and elemental compositions of the nanohybrid films were investigated with scanning electron microscopy and energy dispersive spectroscopy. A novel non-enzymatic glucose sensor based on the Ni–MWNT nanohybrid film-modified glassy carbon electrode was described, and its electrochemical behaviors were investigated. The proposed sensor exhibited high electrocatalytic activity and good response to glucose. Under optimal conditions, the sensor showed high sensitivity (67.2 μA mM⁻¹ cm⁻²), rapid response time (<2 s) and a low detection limit (0.89 μM; signal/noise ratio of 3). In particular, the upper glucose concentration limit produced a linear response of 17.5 mM. Thus, the Ni–MWNT nanohybrid films represent promising sensor materials for non-enzymatic glucose sensing in routine analyses.