Synthesis and Characterization of Zinc Oxide-Reduced Graphene Oxide Hybrid Materials and their Application for Nitrogen Dioxide Detection

Herein, we report a facile synthesis of zinc oxide-reduced graphene oxide (ZnO-rGO) hybrid materials by two-step method. Firstly, rGO was synthesized by using graphite powder mixed with sodium nitrate, sulfuric acid and potassium permanganate via Hummers method. Synthesized rGO were dispersed in ethanol by ultra-sonication for a designated time period. Then, zinc oxide (ZnO) powder was added into rGO-ethanol solution and transferred into Teflon-lined stainless steel autoclave. The ZnO-rGO was produced by hydrothermal method at 180 °C for 120 and 180 min (here after referred to as ZnO(120)-rGO and ZnO(180)-rGO, respectively). The morphological and crystalline structures of synthesized rGO and ZnO-rGO were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Synthesized ZnO-rGO was exposed to 100 parts per million (ppm) nitrogen dioxide (NO2) gas at room temperature, 50 °C and 75 °C for testing its sensing performance. The results show that ZnO(180)-rGO hybrid materials exhibit high response to NO2 gas at 50 °C and 75 °C. The electrical resistance of ZnO-rGO sensors decreased when the sensors responded to NO2 gas, indicating a p-type behavior. Moreover, the ZnO-rGO hybrid materials can detect 100 ppm NO2 gas with an operating temperature limit at 50 °C. The results imply that synthesized ZnO-rGO hybrid materials could be used as gas sensing device for ppm-level NO2 detection at low temperature and consume low power.

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Reduced graphene oxide supported C3N4 nanoflakes and quantum dots as metal-free catalysts for visible light assisted CO2 reduction

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.10.44 ◽

2019 ◽

Vol 10 ◽

pp. 448-458 ◽

Cited By ~ 5

Author(s):

Md Rakibuddin ◽

Haekyoung Kim

Keyword(s):

Electron Microscopy ◽

Graphene Oxide ◽

Visible Light ◽

Reduced Graphene Oxide ◽

Hybrid Materials ◽

Photoelectron Spectroscopy ◽

X Ray ◽

Metal Free ◽

Reduced Graphene ◽

Vis Spectroscopy

The visible light photocatalytic reduction of CO2 to fuel is crucial for the sustainable development of energy resources. In our present work, we report the synthesis of novel reduced graphene oxide (rGO)-supported C3N4 nanoflake (NF) and quantum dot (QD) hybrid materials (GCN) for visible light induced reduction of CO2. The C3N4 NFs and QDs are prepared by acid treatment of C3N4 nanosheets followed by ultrasonication and hydrothermal heating at 130–190 °C for 5−20 h. It is observed that hydrothermal exposure of acid-treated graphitic carbon nitride (g-C3N4) nanosheets at low temperature generated larger NFs, whereas QDs are formed at higher temperatures. The formation of GCN hybrid materials was confirmed by powder X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy (TEM), and UV–vis spectroscopy. High-resolution TEM images clearly show that C3N4 QDs (average diameter of 2–3 nm) and NFs (≈20–45 nm) are distributed on the rGO surface within the GCN hybrid material. Among the as-prepared GCN hybrid materials, GCN-5 QDs exhibit excellent CO2 reductive activity for the generation of formaldehyde, HCHO (10.3 mmol h−1 g−1). Therefore, utilization of metal-free carbon-based GCN hybrid materials could be very promising for CO2 photoreduction because of their excellent activity and environmental sustainability.

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Co2TiO4/Reduced Graphene Oxide Nanohybrids for Electrochemical Sensing Applications

Nanomaterials ◽

10.3390/nano9111611 ◽

2019 ◽

Vol 9 (11) ◽

pp. 1611

Author(s):

Constanza J. Venegas ◽

Fabiana A. Gutierrez ◽

Marcos Eguílaz ◽

José F. Marco ◽

Nik Reeves-McLaren ◽

...

Keyword(s):

Electron Microscopy ◽

Hydrogen Peroxide ◽

Scanning Electron Microscopy ◽

Graphene Oxide ◽

Reduced Graphene Oxide ◽

Hybrid Materials ◽

X Ray ◽

Reduced Graphene ◽

Scanning Electron

For the first time, the synthesis, characterization, and analytical application for hydrogen peroxide quantification of the hybrid materials of Co2TiO4 (CTO) and reduced graphene oxide (RGO) is reported, using in situ (CTO/RGO) and ex situ (CTO+RGO) preparations. This synthesis for obtaining nanostructured CTO is based on a one-step hydrothermal synthesis, with new precursors and low temperatures. The morphology, structure, and composition of the synthesized materials were examined using scanning electron microscopy, X-ray diffraction (XRD), neutron powder diffraction (NPD), and X-ray photoelectron spectroscopy (XPS). Rietveld refinements using neutron diffraction data were conducted to determine the cation distributions in CTO. Hybrid materials were also characterized by Brunauer–Emmett–Teller adsorption isotherms, Scanning Electron microscopy, and scanning electrochemical microscopy. From an analytical point of view, we evaluated the electrochemical reduction of hydrogen peroxide on glassy carbon electrodes modified with hybrid materials. The analytical detection of hydrogen peroxide using CTO/RGO showed 11 and 5 times greater sensitivity in the detection of hydrogen peroxide compared with that of pristine CTO and RGO, respectively, and a two-fold increase compared with that of the RGO+CTO modified electrode. These results demonstrate that there is a synergistic effect between CTO and RGO that is more significant when the hybrid is synthetized through in situ methodology.

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