Presence of Dispersant when dispersing multilayer carbon nanotubes CNTs
Researcher and author: Dr. ( Afshin Rashid)
Note: CNTs multilayer carbon nanotubes have large impurities in some samples, such as graphene polymer particles, amorphous carbon, and catalyst particles. The light absorption of these impurities is related to the spectrum and it is necessary to quantitatively evaluate the elimination of the field absorption field, which in this case is not possible and a little analysis will be associated with error . The third problem is due to the presence of dispersant, which is dispersed when the multilayer CNTs are dispersed, the presence of which leads to misdiagnosis in quantitative detection of SWCNT in the state.
When functional groups are covalently placed on multilayer CNTs, the absorption peaks are significantly attenuated or even disappear because the structure of the nanotube in some hexagonal SP2s changes to the structure of the parts of the SP3 structure . NIR-VIS-UV absorption spectroscopy has two important uses: the rate of covalent reactions and the selectivity of different nanotubes . Non-covalent doping or molecular adsorption produces valence-like electrons (dopingP ) or saturation of the conduction band (doping-n).
These non-covalent interactions can affect the intensity of absorption peaks . When doping, electron donors such as (Cs, K) or electron acceptors make very similar changes in the spectrum (-Br2 ) such as NIR-vis-UV, both of which attenuate electron transfer. Use absorption spectroscopy to estimate the abundance of metallic and semiconductor species by comparing the peaks intensity; Because the position of these resonant peaks depends on chirality and diameter. For qualitative analysis , absorption spectroscopy is excellent because it shows the overall appearance of the sample composition; However, quantitative evaluation depends on (m, n) the absorption of nanotubes for several possible reasons has it. It is reported that the ratio of extinction coefficients for metal to semiconductor SWCNTs is 0.352, which should be independent of the separation method - 0.009 or starting material. However, the values of the extinction coefficients of SWCNTs reported in scientific sources are not consistent and still better measurement methods are needed to determine the extinction coefficient of different nanotubes (m, n). Second, the strong absorption of π in the short wavelength region makes the resonant transitions not distinct. In addition, the complexity of courier overlap is problematic. As a result, the presence of a large number of SWCNTs with different (m, n) with unknown frequency along with various errors along with data analysis, makes it possible to quantitatively assess the concentration of specific species. (m, n) is difficult in the sample and only approximate data is obtained.
PhD in Nano-Microelectronics