Mesoscopic and Condensed Matter Physics

Biography

Biography: Anshul Kumar Sharma

Abstract

Carbon nanotubes (CNTs) possessing unique structure and properties are attractive building blocks for novel materials and devices of important practical interest. Particularly, Multi wall carbon nanotubes (MWCNTs) have attracted extensive attention in sensing application owing to their unique one-dimensional carbon nanostructure and electrical properties. However, the insolubility or poor dispersibility of pristine CNTs in common solvents poses a serious obstacle to their further development. Various attempts have been made to obtain homogeneous CNT dispersions in both aqueous and organic media. Among those approaches, chemical modification of side walls, defect sites, and open ends are often found to result in changes of the structural, mechanical, and electronic properties of CNTs. Generally, carbon nanotubes are very sensitive to many types of target molecules showing an apparent lack of selectivity. This drawback of carbon nanotube sensors can be overcome through functionalization of nanotube surface in order to provide molecular specificity or unbalanced promoted sensitivity to a class of chemical species. Introduction of functional groups, such as carboxyl and amino groups, not only can improve CNTs solubility in various solvents, but also are useful for the further chemical link with other compounds. Recently, in order to improve the sensing performance of these MWCNTs based sensors, many sensing materials such as conducting polymers  metals and metal oxides  have been anchored on the surface of MWCNTs and play important roles in the improvement of the sensitivity and selectivity of the resultant gas sensors.  Phthalocyanine (Pc), as an excellent sensing material, has been extensively studied based on its high sensitivities, excellent thermal and chemical stability. Substituting functional groups on phthalocyanine molecules make them soluble in various organic solvents and thus enable them for low cost solution processing techniques such as spin coating and self-assembly etc Therefore, we expect that combining the nanoscale CNTs with gas sensing active Pc would feature not only the intrinsic properties of CNTs and Pc arising from the mutual interaction between CNTs and Pc but also enhance the gas sensing behaviour of CNTs. In this work, we have prepared a hybrid material of MWCNTs-COOH and Hexa-fluorinated copper phthalocyanine (F₁₆CuPc). The formation of F₁₆CuPc/MWCNTs-COOH hybrid was confirmed by UV-Visible, Raman and FT-IR spectroscopy.  SEM, TEM and AFM studies revealed that F16CuPc₈ molecules were successfully anchored on the surface of MWCNTs-COOH through π-π stacking interaction. Subsequently, a chemi-resistive sensor have been fabricated by drop casting F₁₆CuPc/MWCNTs-COOH hybrid onto alumina substrate. The gas sensing potential of the fabricated hybrid materials has been tested upon exposure to different hazardous gases like NO₂, NO, Cl₂ and NH₃ at different operating temperatures. It has been demonstrated that F₁₆CuPc/MWCNTs-COOH hybrid is highly selective towards Cl₂ with minimum detection limit of 100 ppb. The response of sensor increases linearly with increase in Cl₂ concentration. The results obtained emphasize on the application of F₁₆CuPc/MWCNTs-COOH hybrid material in Cl₂ sensing applications.