The development of MnO2-graphene (MnO2-GR) composite by microwave irradiation method and its application as an electrode material for the selective determination of serotonin (SE), popularly known as ...“happy chemical”, is reported. Anchoring MnO2 nanoparticles on graphene, yielded MnO2-GR composite with a large surface area, improved electron transport, high conductivity and numerous channels for rapid diffusion of electrolyte ions. The composite was characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning electron microscopy (SEM) for assessing the actual composition, structure and morphology. The MnO2-GR composite modified glassy carbon electrode (GCE) exhibited an excellent electrochemical activity towards the detection of SE in phosphate buffer saline (PBS) at physiological pH of 7.0. Under optimum conditions, the modified electrode could be applied to the quantification of serotonin by square wave voltammetry over a wide linear range of 0.1 to 800 µM with the lowest detection limit of 10 nM (S/N = 3). The newly fabricated sensor also exhibited attractive features such as good anti-interference ability, high reproducibility and long-term stability.
Ag@α-Fe₂O₃ nanocomposite having a core-shell structure was synthesized by a two-step reduction-sol gel approach, including Ag nanoparticles synthesis by sodium borohydride as the reducing agent in a ...first step and the subsequent mixing with a Fe
sol for α-Fe₂O₃ coating. The synthesized Ag@α-Fe₂O₃ nanocomposite has been characterized by various techniques, such as SEM, TEM and UV-Vis spectroscopy. The electrical and gas sensing properties of the synthesized composite towards low concentrations of ethanol have been evaluated. The Ag@α-Fe₂O₃ nanocomposite showed better sensing characteristics than the pure α-Fe₂O₃. The peculiar hierarchical nano-architecture and the chemical and electronic sensitization effect of Ag nanoparticles in Ag@α-Fe₂O₃ sensors were postulated to play a key role in modulating gas-sensing properties in comparison to pristine α-Fe₂O₃ sensors.
In this work, ?-Fe2O3 nanoparticles (NPs) have been synthesized by using a
simple Pechini sol-gel method from iron nitrate, citric acid as complexing
agent and ethylene glycol as polymerization ...agent. The calcined ?-Fe2O3 NPs
were fully characterized by different techniques. It was confirmed that
ultrafine and highly crystalline ?-Fe2O3 NPs with high purity and mesoporous
nature can be obtained after calcination at 550?C for 3 h. In addition, the
results of electrical resistance measurements of the fabricated Fe2O3 thick
films showed that ?-Fe2O3 thick films have stable electrical properties which
are beneficial for electrical applications such as gas sensing and field
effect transistors.
nema
The development and application of a hydrogen dual sensor (HDS) for the application in the fuel cell (FC) field, is reported. The dual sensing device is based on a ceramic platform head with a ...semiconducting metal oxide layer (MOx) printed on Pt interdigitated contacts on one side and a Pt serpentine resistance on the back side. MOx layer acts as a conductometric (resistive) gas sensor, allowing to detect low H2 concentrations in air with high sensitivity and fast response, making it suitable as a leak hydrogen sensor. The proposed Co-doped SnO2 layer shows high sensitivity to hydrogen (R0/R = 90, for 2000 ppm of H2) at 250 °C in air, and with fast response (<3 s). Pt resistance serves as a thermal conductivity sensor, and can used to monitor the whole range of hydrogen concentration (0–100%) in the fuel cell feed line with short response-recovery times, lower than 13 s and 14 s, respectively. The effect of the main functional parameters on the sensor response have been evaluated by bench tests. The results demonstrate that the dual sensor, in spite of its simplicity and cheapness, is promising for application in safety and efficiency control systems for FC power source.
•A hydrogen dual sensor (HDS) for the application in the fuel cell (FC) field was developed.•The main functional parameters on the sensor response have been evaluated by bench tests.•HDS shows high sensitivity to H2 (R0/R = 90, for 2000 ppm of H2) and fast response (<3 s).•HDS monitor whole range of H2 conc. (0–100%) in FC feed line with fast response (<13 s).•HDS is simple, cheaper and is promising for application in safety and efficiency control systems for FC.
In this work, Fe2O3 nanoparticles (NPs) were successfully synthesized by
Pechini sol-gel method. Scanning electron microscopy, transmission electron
microscopy and X-ray diffraction characterizations ...were used to study the
morphology and crystal structure of the synthesized products. The electrical
and gas sensing behaviour of the synthesized and commercial Fe2O3 samples,
prepared in the form of thick films, were studied. Though the commercial
Fe2O3 powders had lower resistance but it was found that the synthesized
Fe2O3 NPs had better gas sensing properties. The underlying mechanisms are
discussed in details. The present findings show advantages of Fe2O3 NPs over
micro-size particles for gas sensing applications.
nema
2D-SnS2 flakes were synthesized via a wet chemical route and deposited as a thin film onto the Pt-interdigitated contacts of a ceramic substrate with aim to fabricate a conductometric sensor. The ...2D-SnS2 sensing film was then annealed “in situ” under controlled conditions at different temperatures up to 400 °C. The morphological, microstructural and electrical properties of the sensing film, before and after the thermal treatment, were characterized by “in situ” techniques. SEM analysis has shown that the 2D flake morphology was maintained after thermal treatments, whereas Raman and EDX analysis have highlighted the partial/total modification of the SnS2 phase towards the SnO2. As a consequence of the formation of 2D-SnS2/SnO2-x mixed phases, a dramatic change of the electrical properties of the sensing film has been also observed.
Conductometric gas sensors based on hybrid SnS2-SnO2-x nanoflakes were then obtained by simple self-annealing treatments of 2D-SnS2 film directly on the sensor substrate. The fabricated sensors were tested toward ammonia (NH3) as target gas. Results evidence that increasing the annealing temperature of the 2D-SnS2 sensitive film, the electrical resistance of the sensing layer decreases while the response towards ammonia increases, showing the maximum at an annealing treatment of 250 °C. This behaviour was explained on the basis of the morphological, microstructural and electrical modifications observed, highlighting the role of 2D-SnS2/SnO2-x mixed phases in determining the sensing properties towards ammonia.
•Synthesis of two-dimensional (2D) SnS2 flakes by a wet chemical route.•Formation of SnS2-SnO2-x heterostructures by self-annealing of SnS2 sensing layer on a sensor substrate.•Effect of annealing temperature on the electrical and NH3 sensing properties of the sensing layer.•SnS2-SnO2-x mixed phases show improved NH3 sensing properties than pure SnS2 or SnO2 phases.
A planar electrochemical sensor, based on flower-like CuO nanostructures growth “in situ” on a commercial screen printed carbon electrode, was fabricated by an easy and effective technique and ...employed for the non-enzymatic determination of glucose. The prepared CuO nanostructures were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The carbon electrode modification with CuO was optimized by investigating the effect of the number of deposition cycles of precursor and their concentration. The electrodes modified by in situ growth of CuO were compared to an electrode prepared by simple deposition of CuO powder previously synthesized by the same technique. Cyclic voltammetric and chronoamperometric tests demonstrated that the in situ growth of CuO leads to excellent electrochemical performance toward glucose oxidation in 0.1 M KOH solution. The best sensor, if operated at an applied potential of 0.6 V, has a sensitivity of 1460 μA·mM
−1
·cm
−2
and a 2.5 μM detection limit (at an S/N ratio of 3). Tests carried out within six months revealed an excellent long-term stability. This suggests that the method applied to modify the carbon electrode represents a useful tool for fabrication of an inexpensive and reliable non-enzymatic glucose sensor.
Graphical abstract
Schematic of a glucose sensor fabricated by growing flower-like CuO nanostructures in-situ on a screen printed carbon electrode (SPCE). The sensor showed excellent sensitivity and long-term stability.
In this study, an investigation about the oxygen sensing properties of lanthanum orthoferrite (LaFeO3) ceramics is reported. LaFeO3 nanoparticles were synthesized by using tartaric sol-gel route and ...annealed in air at different temperatures (500, 700 and 900°C). The samples have been characterized by using thermal analysis (TA), BET surface area and porosity, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Results of sensing tests indicate that LaFeO3 nanoparticles exhibit good response to oxygen at mild temperatures (300–450°C). The effect of annealing temperature on gas sensing performance was investigated, demonstrating that LaFeO3 ceramics obtained after annealing at 500°C display better characteristics with respect to others. The oxygen sensor developed shows also high stability in humid environment and excellent selectivity to oxygen over other interfering gases such as CO, NO2, CO2, H2 and ethanol.
Nickel/carbon composites (Ni−C) have been synthesized by a pyrolysis treatment carried out at the temperature of 675 °C, of NiO incorporated into a pyrogallol‐formaldehyde organic wet gel. Structural ...and morphological characterizations of the Ni−C samples were performed by XRD and SEM analysis, respectively. Electrochemical non‐enzymatic glucose sensors were fabricated modifying the working electrode surface of screen printed carbon electrodes. Cyclic voltammetry and amperometric tests were performed in order to investigate the electrocatalytic activity of differently Ni loaded carbon towards the oxidation of glucose in alkaline 0.1 M KOH solution. The sensor based on 30 % Ni/carbon showed the best sensing performance towards glucose monitoring with a sensitivity of 670 μA/mM cm−1 in the a liner range from 20 to 500 μM, and a detection limit lower than 8 μM at S/N=3.
The availability of low-cost, high-performing sensors for carbon dioxide detection in the environment may play a crucial role for reducing CO2 emissions and limiting global warming. In this study, ...calcium-doped zinc oxide nanofibres with different Ca to Zn loading ratios (1:40 or 1:20) are synthesised via electro-spinning, thoroughly characterised and, for the first time, tested as an active material for the detection of carbon dioxide. The results of their characterisation show that the highly porous fibres consist of interconnected grains of oxide with the hexagonal wurtzite structure of zincite. Depending on the Ca:Zn loading ratio, calcium fully or partly segregates to form calcite on the fibre surface. The high response of the sensor based on the fibres with the highest Ca-doping level can be attributed to the synergy between the fibre morphology and the basicity of Ca-ion sites, which favour the diffusion of the gas molecules within the sensing layer and the CO2 adsorption, respectively.
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