scholarly journals Fabrication of Graphene/Zinc Oxide Nano-Heterostructure for Hydrogen Sensing

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6943
Author(s):  
Yang-Ming Lu ◽  
Chi-Feng Tseng ◽  
Bing-Yi Lan ◽  
Chia-Fen Hsieh
Keyword(s):  
Zinc Oxide ◽  
Seed Layer ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Raman Spectrometer ◽  
Hydrogen Sensing ◽  
Layer Graphene ◽  
Nano Zinc Oxide ◽  
Nano Zinc ◽  
Zinc Oxide Nanostructure

In this study, hydrogen (H2) and methane (CH4) were used as reactive gases, and chemical vapor deposition (CVD) was used to grow single-layer graphene on a copper foil substrate. The single-layer graphene obtained was transferred to a single-crystal silicon substrate by PMMA transfer technology for the subsequent growth of nano zinc oxide. The characteristics of CVD-deposited graphene were analyzed by a Raman spectrometer, an optical microscope, a four-point probe, and an ultraviolet/visible spectrometer. The sol–gel method was applied to prepare the zinc oxide seed layer film with the spin-coating method, with methanol, zinc acetate, and sodium hydroxide as the precursors for growing ZnO nanostructures. On top of the ZnO seed layer, a one-dimensional zinc oxide nanostructure was grown by a hydrothermal method at 95 °C, using a zinc nitrate and hexamethylenetetramine mixture solution. The characteristics of the nano zinc oxide were analyzed by scanning electron microscope(SEM),x-ray diffractometer(XRD), and Raman spectrometer. The obtained graphene/zinc oxide nano-heterostructure sensor has a sensitivity of 1.06 at a sensing temperature of 205 °C and a concentration of hydrogen as low as 5 ppm, with excellent sensing repeatability. The main reason for this is that the zinc oxide nanostructure has a large specific surface area, and many oxygen vacancy defects exist on its surface. In addition, the P–N heterojunction formed between the n-type zinc oxide and the p-type graphene also contributes to hydrogen sensing.

Comparative study of electron transfer on various graphene-metallic contacts

2019 ◽  
Vol 33 (31) ◽  
pp. 1950384
Author(s):  
Di Lu ◽  
Yu-E Yang ◽  
Weichun Zhang ◽  
Caixia Wang ◽  
Jining Fang ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Single Layer ◽  
Annealing Treatment ◽  
Single Layer Graphene ◽  
Strain Effect ◽  
Graphene Surface ◽  
Layer Graphene ◽  
Metallic Contacts ◽  
Nonuniform Strain ◽  
Main Factor

We have investigated Raman spectra of the G and 2D lines of a single-layer graphene (SLG) with metallic contacts. The shift of the G and 2D lines is correlated to two different factors. Before performing annealing treatment or annealing under low temperature, the electron transfer on graphene surface is dominated by nonuniform strain effect. As the annealing treatment is enhanced, however, a suitable annealing treatment can eliminate the nonuniform strain effect where the relative work function (WF) between graphene and metal becomes a main factor to determine electronic transfer. Moreover, it is confirmed that the optimized annealing treatment can also decrease effectively the structural defect and induced disorder in graphene due to metallic contacts.

scholarly journals Millisecond lattice gasification for high-density CO2- and O2-sieving nanopores in single-layer graphene

2021 ◽  
Vol 7 (9) ◽  
pp. eabf0116
Author(s):  
Shiqi Huang ◽  
Shaoxian Li ◽  
Luis Francisco Villalobos ◽  
Mostapha Dakhchoune ◽  
Marina Micari ◽  
...  
Keyword(s):  
Single Layer ◽  
High Density ◽  
Single Layer Graphene ◽  
Pore Density ◽  
Vacancy Defects ◽  
Carbon Gasification ◽  
Layer Graphene ◽  
Gas Molecules ◽  
Good Agreement

Etching single-layer graphene to incorporate a high pore density with sub-angstrom precision in molecular differentiation is critical to realize the promising high-flux separation of similar-sized gas molecules, e.g., CO2 from N2. However, rapid etching kinetics needed to achieve the high pore density is challenging to control for such precision. Here, we report a millisecond carbon gasification chemistry incorporating high density (>1012 cm−2) of functional oxygen clusters that then evolve in CO2-sieving vacancy defects under controlled and predictable gasification conditions. A statistical distribution of nanopore lattice isomers is observed, in good agreement with the theoretical solution to the isomer cataloging problem. The gasification technique is scalable, and a centimeter-scale membrane is demonstrated. Last, molecular cutoff could be adjusted by 0.1 Å by in situ expansion of the vacancy defects in an O2 atmosphere. Large CO2 and O2 permeances (>10,000 and 1000 GPU, respectively) are demonstrated accompanying attractive CO2/N2 and O2/N2 selectivities.

Effect of Calcination on the Basic Strength of Surface Modified Nano-Zinc Oxide Characterised by FTIR and Back Titration Methods

2015 ◽  
Vol 1107 ◽  
pp. 326-332
Author(s):  
Abdul Rahim Yacob ◽  
Kamaluddeen Suleiman Kabo
Keyword(s):  
Zinc Oxide ◽  
Metal Oxides ◽  
Base Catalysis ◽  
Nano Zinc Oxide ◽  
Back Titration ◽  
And Performance ◽  
Nano Zinc ◽  
Surface Modified ◽  
Heterogeneous Base ◽  
Basic Strength

The use of metal oxides in heterogeneous base catalysis has gained a large interest due to their application in many chemical and industrial processes and is environmental friendly. Basic metal oxides are commonly used and their structures, morphology and performance can be modified by method of preparation and thermal activation. In this study, surface modified amphoteric zinc oxide was prepared via hydration-dehydration method and characterised by TGA and FTIR. The basic strength at various temperatures is characterised by FTIR and back titration analyses. The results shows that surface modified zinc oxide has the highest basic strength of 1.453mmolg-1at 400°C making it a relatively good and suitable compound for use in heterogeneous basic catalysis. This result is also supported by FTIR spectra which show possible relationship between the Lewis O2-and increasing basic strength.

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