A Highly Sensitive Room Temperature CO2 Gas Sensor Based on SnO2-rGO Hybrid Composite.

Concurrent synthesis of nitrogen-doped carbon dots for cell imaging and ZnO@nitrogen-doped carbon sheets for photocatalytic degradation of methylene blue

Nowadays, a lot of pesticides have been used in the agriculture field due to the global demand for food production. Carbofuran (CF) is the most commonly used carbamate compound that is responsible for the highest toxicity to humans compared to any other pesticide used in agricultural settings. Thus, rapid, portable, and low-cost sensors are needed for the detection of CF in the environment and food samples. Herein, we have successfully developed an electrochemical sensor using a glassy carbon electrode (GCE) modified with gadolinium sulfide (Gd2S3) and reduced graphene oxide (RGO) composite for the detection of carbofuran (CF). A novel Gd2S3/RGO composite was prepared by the facile hydrothermal route and confirmed by morphological and structural analyses such as field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX), powder X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), and also the formation mechanism of Gd2S3/RGO composite was discussed. The desired electrical conductivity of Gd2S3 was enhanced by the RGO, which was estimated from the electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Electrochemical studies demonstrated that the developed Gd2S3/RGO sensor was highly sensitive and selective to CF. In addition, the Gd2S3/RGO sensor exhibits a low detection limit (LOD) and the linear ranges were 0.0128 and 0.001-1381 μM, respectively, for CF detection under optimized experimental conditions. Moreover, we also investigated the practical applicability of the sensor for CF detection in the environment and food samples.

The Cobalt nanoparticles were deposited on reduced graphene oxide (RGO) by electroless plating procedure, in which the RGO was used as substrate precursor. The surface morphology of Co-Pd/Sn/RGO composite was studied by High resolution transmission electron microscopy (HRTEM) and Field emission scanning electron microscopy (FESEM). The Powdered x-ray Diffraction studies (PXRD) and also Raman Spectroscopy (RAMAN) have shown the Cobalt deposition on RGO. The extent of deposition of Cobalt nanoparticles on RGOs including the under coat elements such as Tin and Palladium was studied by Energy dispersive x-ray analysis (EDX) and x-ray Photoelectron Spectroscopy (XPES) techniques. The electrocatalytic activity of the deposited cobalt nanoparticles on RGO has been tested by Cyclic voltammetry (CV) and Impendence spectroscopy studies (EIS). The effective surface areas of Co-Pd/Sn/RGO and RGO were calculated using Randles-Sevecik equation and the values are 6.0785 × 10−6 cm2 and 1.588 × 10−6 cm2 respectively. The electrocatalytic property of Co-Pd/Sn/RGO has been tested for energy application by the oxidation of methanol and ethanol. A significant electrocatalytic activity of Co-Pd/Sn/RGO has been found for the oxidation of methanol and ethanol in acidic medium. These results suggest that the Co-Pd/Sn/RGO material could be harnessed as electrode/catalyst system for alcohol fuel cell application.

Miniaturized gas sensors or electronic noses to rapidly detect and differentiate trace amount of chemical agents are extremely attractive. In this paper, we report on the fabrication and characterization of a functional tin oxide nanoparticle gas sensor. Tin oxide nanoparticles are first synthesized using a convenient and low‐cost mini‐arc plasma source. The nanoparticle size distribution is measured online using a scanning electrical mobility spectrometer (SEMS). The product nanoparticles are analyzed ex‐situ by high resolution transmission electron microscopy (HRTEM) for morphology and defects, energy dispersive X‐ray (EDX) spectroscopy for elemental composition, electron diffraction for crystal structure, and X‐ray photoelectron spectroscopy (XPS) for surface composition. Nonagglomerated rutile tin oxide (SnO2) nanoparticles as small as a few nm have been produced. Larger particles bear a core‐shell structure with a metallic core and an oxide shell. The nanoparticles are then assembled onto an e‐beam lithographically patterned interdigitated electrode using electrostatic force to fabricate the gas sensor. The nanoparticle sensor exhibits a fast response and a good sensitivity when exposed to 100 ppm ethanol vapor in air.

A carbon monoxide (CO) thermoelectric (TE) gas sensor was fabricated by affixing a Au/Co3O4 catalyst tablet on a TE film layer. The Au/Co3O4 catalyst tablet was prepared by a co-precipitation and tablet compression method and its possible catalytic mechanism was discussed by means of x-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, x-ray photoelectron spectroscopy, temperature-programmed reduction of hydrogen, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analysis. The optimal catalyst, with a Au content of 10 wt%, was obtained at a calcination temperature between 200 and 300 °C. The small size of the Au nanoparticles, high specific surface, the existence of Co3+ and water-derived species contributed to high catalytic activity. Based on the optimal Au/Co3O4 catalyst tablet, the CO TE gas sensor worked at room temperature and showed a response voltage signal (ΔV) of 23 mV, high selectivity among hydrogen and methane, high stability, and a fast response time of 106 s for 30 000 ppm CO/air. In addition, a CO concentration in the range of 5000–30 000 ppm could obviously be detected and exhibited a linear relationship with ΔV. The CO TE gas sensor provides a promising option for the detection of CO gas at room temperature.

The low cost and profusion of sodium resources make sodium-ion batteries (SIBs) a potential alternative to lithium-ion batteries for grid-scale energy storage applications. However, the use of conv...

A biomolecule assisted synthesis of bismuth sulfide (Bi2S3)/reduced graphene oxide (rGO) composite nanostructures by one-pot hydrothermal method. The structure, morphology and elemental analysis of the synthesized material were studied by X-ray diffractometer (XRD) and high resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy attest the reduction of graphene oxide and structural defects respectively. Absorbance and emission responses were studied by UV-vis-NIR and Photoluminescence spectroscopy. Electrochemical performances of the graphene oxide (GO), Bi2S3 and Bi2S3/rGO composite were investigated by Electrochemical workstation. The Bi2S3/rGO composite electrode attained five times higher specific capacitances of 817.6 F g−1 at scan rate of 5 mV s−1 and 680.6 F g−1 at a current density of 1 A g−1 compared to pure Bi2S3 (143.9 F g−1 at 5 mV s−1 and 152.23 F g−1 at 1 A g−1) respectively. Moreover, Bi2S3/rGO composite maintain better cyclic stability with the capacitance retention about 87% over 1000 cycles, and offer a high conductive connection for fast ion diffusion between electrode and electrolyte interface. The strong synergistic effect of the hierarchical flower structured/rGO composite suggest as a promising material for supercapacitor applications.

A comparative study on the electrocatalytic efficiency of coupled (CuO-Co3O4) vs. mixed (CuCo2O4) metal oxides: Probed by hydrazine oxidation and sensitive determination

Supramolecularly assembled isonicotinamide/reduced graphene oxide nanocomposite for room-temperature NO2 gas sensor

One-pot synthesis of efficient reduced graphene oxide supported binary Pt-Pd alloy nanoparticles as superior electro-catalyst and its electro-catalytic performance toward methanol electro-oxidation reaction in direct methanol fuel cell

Reduced graphene oxide/polymethyl methacrylate (rGO/PMMA) nanocomposite for real time gamma radiation detection

Utilization of green reductant Thuja Orientalis for reduction of GO to RGO

Power transformer is an important equipment to transport and deliver the electric energy in the power system. It will result in huge damage of national economy while the transformers break down. On-line monitoring the dissolved gases in oil is one of the effective methods to improve the security and reliability of the power system. CO is the one of main failure characteristic gases in the transformer oil. It's significant to monitor on-line and analyze CO gas for the power transformer's safe operation. The key of on-line monitoring is the gas sensor technology. One-dimensional (1D) semiconductor metal oxide nanostructures have attracted increasing attention in electrochemistry, optics, magnetic, and gas sensing fields for the good properties. N-type low dimensional semiconducting oxides such as SnO 2 and ZnO have been known for the detection of inflammable or toxic gases. In this paper, we fabricated the ZnO-SnO 2 and SnO 2 nanoparticles by hydrothermal synthesis. Microstructure characterization was performed using X-ray diffraction (XRD) and surface morphologies for both the pristine and doped samples were observed using field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Then we made thin film gas sensor to study the gas sensing properties of ZnO-SnO 2 and SnO 2 gas sensor to CO. A systematic comparison study reveals an enhanced gas sensing performance for the sensor made of SnO 2 and ZnO towards CO over that of the commonly applied undecorated SnO 2 nanoparticles. The improved gas sensing properties are attributed to the size of grains and pronounced electron transfer between the compound nanostructures and the absorbed oxygen species as well as to the heterojunctions of the ZnO nanoparticles to the SnO 2 nanoparticles, which provide additional reaction rooms. The results represent an advance of compound nanostructures in further enhancing the functionality of gas sensors, and this facile method could be applicable to many sensing materials, offering a new avenue and direction to detect gases of interest based on composite tin oxide nanoparticles.

Porous Ternary High Performance Supercapacitor Electrode Based on Reduced Graphene Oxide, NiMn2O4, and Polyaniline

Hematite (α-Fe2O3) and pseudobrookite (Fe2TiO5) suffer from poor charge transport and a high recombination effect under visible light irradiation. This study investigates the design and production of a 2D graphene-like r-GO/GO coupled α-Fe2O3/Fe2TiO5 heterojunction composite with better charge separation. It uses a simple sonochemical and hydrothermal approach followed by L-ascorbic acid chemical reduction pathway. The advantageous band offset of the α-Fe2O3/Fe2TiO5 (TF) nanocomposite between α-Fe2O3 and Fe2TiO5 forms a Type-II heterojunction at the Fe2O3/Fe2TiO5 interface, which efficiently promotes electron-hole separation. Importantly, very corrosive acid leachate resulting from the hydrochloric acid leaching of ilmenite sand, was successfully exploited to fabricate α-Fe2O3/Fe2TiO5 heterojunction. In this paper, a straightforward synthesis strategy was employed to create 2D graphene-like reduced graphene oxide (r-GO) from Ceylon graphite. The two-step process comprises oxidation of graphite to graphene oxide (GO) using the improved Hummer's method, followed by controlled reduction of GO to r-GO using L-ascorbic acid. Before the reduction of GO to the r-GO, the surface of TF heterojunction was coupled with GO and was allowed for the controlled L-ascorbic acid reduction to yield r-GO/GO/α-Fe2O3/Fe2TiO5 nanocomposite. Under visible light illumination, the photocatalytic performance of the 30% GO/TF loaded composite material greatly improved (1240 Wcm-2). Field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) examined the morphological characteristics of fabricated composites. X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), X-ray fluorescence (XRF), and diffuse reflectance spectroscopy (DRS) served to analyze the structural features of the produced composites.