As a new nanostructure, a graphene is a compound of carbon atoms with a two-dimensional structure that has attracted the attention of many nanoscale researchers due to its novel physical and chemical properties. The presence of all graphene atoms in the surface and its unique electrical properties, as well as the ability to functionalize and combine with another nanomaterial, has introduced graphene as a new and suitable candidate material for gas sensing. Over the years, many researchers have turned their attention to carbon nanomaterial. The unique optical, mechanical, and electronic properties of these nanostructures have led them to use these nanomaterials to develop tiny devices, such as low-consumption sensors. Carbon nanomaterial poses a threat to another nanomaterial in terms of their use in gas sensors. This review article discusses the use of carbon nanoparticles and graphene in gas sensors, examines the nodes in the commercialization pathway of these compounds, and presents the latest achievements. Finally, the perspectives of the challenges and opportunities in the field of sensors based on carbon nanomaterial and graphene are examined.

nanopowders with anatase structure were firstly prepared by controlling the pH value of a precursor solution without any heat-treatment at room temperature. The prepared nanopowders were hydrothermally treated in 10M NaOH solution at . Then, the samples were washed in DI water or 0.1M HCl. The nanotubes were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The gas sensitivity of nanotubes for toluene gas was also investigated. The results show that nanotubes can be prepared by hydrothermal treatment. The morphology of nanotubes prepared by 0.1M HCl washing is destroyed to some extent. nanotubes with DI water washing show better sensitivity than that with 0.1M HCl washing.

Based on the database of 128 disk galaxies (66 SO, 62 S and Irr) mailnly compiled from Kent and Gunn (1982) and Doi et a1.(1995) which is complete down to m < 15.6 mag within a radius of 3°, the orientation of spin vectors of disk galaxies of the Coma cluster has been analyzed. The results confirm the morphological dependence of the orientation of disk galaxies found from the analsis of the Virgo cluster. Common features of orientation of disk galaxies of both clusters are outlined.