Authors: S. Tsuruoka, K. Takeuchi, K. Koyama, M. Endo, K. Fujisawa, H. Matsumoto, N. Saito, Y. Usui, D.W. Porter, V. Castranova
Affilation: Shinshu University, Japan
Pages: 449 - 452
Keywords: ROS, morphology, CNTs, ESR
Carbon nanotubes (CNTs) are becoming important materials in industry. It is a concern that CNTs may induce carcinogenic responses through pulmonary exposure. It has been recently reported1-6 that CNTs scavenge ROS depending on their morphology. ROS production has been utilized for toxicological evaluations. Although the electron charge transfer seems the noticeable phenomena of toxicological chemical reactions, a comprehensive evaluation of ROS scavenging capabilities using a variety of CNTs has not been demonstrated well. The present work specifically investigates ROS scavenging capabilities using the series of CNTs and their derivatives with surface modifications. Those ROS scavenging properties were measured by ESR with DMPO. Highly crystallized, mechanically chopped, mechanically de-bulked, and metal doped CNTs were evaluated. Furthermore, their surface modification by nitric acid and ozone was compared with untreated CNTs. Interestingly, the ROS scavenging rate was not significantly influenced by mechanical treatments, but depended on crystallization at high temperature. The results suggest that the electron transfer on the CNT surface is the fundamental mechanism of ROS scavenging. Dangling bonds are not a key factor for scavenging, though. ROS measurement is affected by surfactant concentration and the CNT/hydrogen peroxide ratio. The surface modification may lead to safety by design for CNTs.