Our dye assay method was similar to that of previous reports [43, 44]. Glassy carbon was incubated in 0.2-mM toluidine blue O (TBO, Sigma-Aldrich) solution at pH 10 and at room temperature for 1 h to adsorb positively charged dye onto the anionic carboxylate or sulfonate group. The glassy carbon was then rinsed with NaOH (pH 10) solution and

further incubated in 0.1-mM NaOH (pH 10) solution for 5 min to remove physisorbed TBO dye. The adsorbed TBO on anionic buy Givinostat glassy carbon was removed from the HCl solution (pH 1). The concentration of desorbed TBO in the HCl solution was determined by the absorbance at 632 nm using Ocean Optics (Dunedin, FL, USA) USB 4000 UV–vis spectrometer. The calculation of carboxyl or sulfonate density was based on the assumption that positively charged TBO binds with carboxylate or sulfonate groups at 1:1 ratio on glassy carbon. Results and discussion The PFT�� fabrication of DWCNT membranes using microtome cutting method was described in the ‘Methods’ section. TEM image of DWCNTs and SEM image of the as-made DWCNT membrane in cross-sectional view are shown in Figure 1A,B, respectively. Figure 1C shows the schematic structure of functionalized DWCNT membranes with tethered

anionic dye. Carbon nanotube www.selleckchem.com/products/blasticidin-s-hcl.html membranes can imitate ion channels with the functionalized molecules acting as mimetic gatekeepers. In our previous studies, functionalization of the gatekeeper includes the two-step modification, [18, 45] as shown in Figure 2. CNT membranes were first modified by 4-carboxylphenyl diazonium grafting, and then the negatively charged dye molecules were linked with carboxyl sites using carbodiimide coupling chemistry. However, it is difficult to control the gatekeeper density since the oligomer is formed by diazonium grafting and the second coupling reaction may not have 100% yields. The functionalization chemistry at the CNT tip determines the applications for CNT membranes, with the ideal gatekeeper being a monolayer

grafted at the entrance of CNT cores that Methocarbamol can actively pump chemicals through the pores [13]. The mechanism of electrooxidation of amine includes radical generation and bonding formation on the surface (Figure 3A). The electrooxidation of amine first generates an amino radical cation. After deprotonation, the neutral aminyl radical can be covalently attached to the surface, but the yield is typically less than that of diazonium grafting [46–49]. By electrooxidation of the amine group of dye (as shown in Figure 3B), the charged dye molecules were simply covalently grafted in one-step functionalization. Figure 2 Schematic illustration of two-step functionalization. (A) Electrochemical grafting or chemical grafting of 4-carboxyl phenyl diazonium. (B) Carbodiimide coupling of Direct Blue 71 dye. Figure 3 Schematic mechanism and illustration.