In this paper, the effects of acid oxidation parameters to the structural and electrochemical behavior of multi-walled carbon nanotubes (MWCNTs) were investigated. The parameters studied were acid concentration, oxidation temperature and oxidation time. The measurement of effects was calculated by how much amount of carboxylic groups (-COOH) introduced and how much structural defects occurred, measured by Fourier Transform Infra-Red Spectroscopy (FTIR) and Raman spectroscopy, respectively. Morphological study was carried out by using SEM. Meanwhile, cyclic voltammetry test (CV) was used in purpose to study the effect of COOH amounts and structural defect to the electrochemical behavior of the COOH-MWCNTs by measuring the oxidation current peaks of DNA immobilization (immobilization current, Iimmo). At the end of this study, we had found that the structural defect of COOH-MWCNTs was directly proportional to the amount of COOH produced. By increasing the acid concentration, oxidation temperature and oxidation time, the amounts of COOH will continuously increase, and so on with the structural defect. Meanwhile, from the cyclic voltammetry test, the results had shown that the immobilization current (Iimmo) was directly proportional to the increasing number of COOH. However, the current will started to reduce once the structural defect had occurred too much.
