Authors: S C Ramos A O Lobo G de Vasconcelos E F Antunes V J TravaAiroldi E J Corat
Publish Date: 2011/07/15
Volume: 130, Issue: 4-6, Pages: 1061-1069
Abstract
In this work we have studied superhydrophilic and superhydrophobic transitions on the vertically aligned multiwalled carbon nanotube VACNT surfaces Asgrown the VACNT surfaces were superhydrophobic Pure oxygen plasma etching modified the VACNT surfaces to generate superhydrophilic behavior Irradiating the superhydrophilic VACNT surfaces with a CO2 laser up to 50 kW cm−2 restored the superhydrophobicity to a level that depended on the laser intensity Contact angle and surface energy measurements by the sessile drop method were used to examine the VACNT surface wetting Xray photoelectron spectroscopy XPS showed heavy grafting of the oxygen groups onto the VACNT surfaces after oxygen plasma etching and their gradual removal which also depended on the CO2 laser intensity These results show the great influence of polar groups on the wetting behavior with a strong correlation between the polar part of the surface energy and the oxygen content on the VACNT surfaces In addition the CO2 laser treatment created an interesting cagelike structure that may be responsible for the permanent superhydrophobic behavior observed on these samples
Keywords: