Shahir Hussain

Investigation of effects produced by chemical functionalization in single-walled and multi-walled carbon nanotubes using Raman spectroscopy

Single-wall carbon nanotubes (SWNTs) as well as multi-wall carbon nanotubes (MWNTs) were characterized by Raman spectroscopy to observe the changes in their physical and structural properties on functionalization. When SWNTs or MWNTs are chemically treated, the defects are created. The analysis of radial breathing mode (RBM) showed that the diameter of the single wall carbon nanotubes changed after functionalization. In the carboxylated sample, the intensity of the disordered band (D-mode) increased more than in the pristine samples. The increase in the D-band intensity in SWNTs after functionalization can be attributed to carbon atoms excited from sp2 to sp3 hybridization. A higher intensity ratio in D-and G-mode (ID/IG) was observed after functionalization with carboxylic group (COOH). The intensity ratio ID/IG increased on acid treatment which was evident from the Raman spectra and their analysis. In case of MWNTs, the intensity of D band became equal to the intensity of G band, which was due to the huge number of defects that had been introduced in the sidewalls. Moreover, it was found in this study that the MWNTs can be much easier chemically functionalized than SWNTs under the same physical conditions.

Optical investigations of microwave induced synthesis of zinc oxide thin-film

Abstract In this article, ZnO thin-film deposition on a glass substrate was done using microwave induced oxygen plasma based CVD system. The prepared thin-films were tested in terms of crystallinity and optical properties by varying the microwave power. The effect of power variation on the morphology and size of final products was carefully investigated. The crystal structure, chemical composition and morphology of the final products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, Raman spectroscopy and photoluminescence (PL). This technique confirmed the presence of hexagonal ZnO nanocrystals in all the thin-films. The minimum crystallite grain size as obtained from the XRD measurements was ~9.7 nm and the average diameter was ~18 nm.

Study the degree of purification of single wall carbon nanotubes (SWNTs)

Purification of single-walled carbon nanotubes (SWNTs) is still remaining a challenging task. The aim of this work is to show novel and fast concepts for the purification of CNTs by combination of different techniques. The carbonaceous particles were presumably etched away by the selective oxidation with faster etching rate than nanotubes. This gives rise to very high yield of about 35%. It was found from Raman scattering measurements that the ratio of the intensity of G-line peak to that of D-line peak increased drastically by this purification process. The D–G ratio of dynamically air oxidized SWNTs (0.06) is much smaller than that of as-received (0.09) or air–HCl purified (0.1) SWNTs, indicating higher purity (and lower level of structural defects) of the dynamically air oxidized sample.

Study of chemically functionalized carbon nanotubes

Multi wall carbon nanotubes (MWCNTs) were characterized by SEM and Raman spectroscopy to observe the effect of fimctionalization on the structural and the chemical properties. When MWCNTs are chemically treated, the defects are created. In the functionalized sample, the intensity of the disordered band (D-mode) increases than the pristine samples. A higher intensity ratio in D-and G-mode (ID/IG) is observed after fimctionalization with oxygenated functional groups. In case of MWCNTs, the D band becomes equal to the G band in intensity which is due to the huge number of defects that have been introduced in the sidewalls.

Ozone/UV-light oxidation of multiwall carbon nanotubes (MWCNTs)

We investigate the purification of as-prepared multi- wall carbon nanotubes (MWCNTs) by exposure to ultraviolet lamp (λ=185 nm). UV irradiation was conducted under ambient condition in a UV lamp chamber which had a layer of reflective aluminium foil inside to ensure the entire sample would have an even exposure to UV. Raman spectroscopy before and after UV exposure indicates the removal of non-nanotube material. The narrowing of D-band is consistent with highly purified nanotube which is seen in our results. Raman result shows that the ozone oxidation can remove the defect site of nanotubes. Intensity of G- and D*- band increases rapidly with increasing the oxidation time. Intensity ratio ID*/ID increases continually with increasing the ozone oxidation time which confirm the reduction of impurities from the MWCNTs.