Covalent Functionalization of Carbon Nano Tubes S.H. Pisala, N.S. Haraleb, H.P. Deshmukhc, J. H. Kimd, P. S. Patil*b aDepartment of Physics, S. M. Joshi College, Hadapsar, Pune-411028 bThin Film Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416004,India cDepartment of Physics, Y .M .college, Pune, India dDepartment of Materials Science, Chonnam National University, Gwangju 500 757, South Korea.   Abstract - It is well known that carbon nanotubes do not represent significant reinforcement for composite but once functionalized it shows interesting new properties. Multi walled carbon nanotubes (MWNTs) produced using the arc discharge method were initially chemically treated with mixture of 3:1 (v/v) of concentrated H2SO4/HNO3.This acid treatment introducing the carboxylic acid groups at defect sites and end of CNTs. Motivation For many applications uniform and stable dispersion of CNTs is required. But pristine CNTs are insoluble in most organic solvent and aqueous solution. They tend to aggregate as result of Van-der Waals interactions. Functionalization over comes such problems. It increase solubility of CNTs, improve the chemical reactivity and enhance the interaction with other compound in hybrid material. MWCNT + H2SO4: HNO3→ MWCNT-COOH + H2O +SO2 +2NO2 Methodology XRD FT-IR FT-Raman TEM SEM TEM Conclusions FT-IR spectra confirm the presence of –COOH, functional group. The Raman analysis confirms transformation of sp2 to sp3 sites as ratio ID/IG increases. SEM image shows acid-treatments shorten the length of MWCNTs. TEM observations indicated average diameter of MWCNTs increases.