This paper reports molecular diffusion behavior in two bolaamphiphile-based organic nanotubes having inner carboxyl groups with different inner dimeters (10 and 20 nm) and wall structures, COOH-ONT 10nm and COOH-ONT 20nm , using imaging fluorescence correlation spectroscopy (imaging FCS). The results were compared to those previously obtained in a similar nanotube with inner amine groups (NH 2 -ONT 10nm ). COOH-ONT 10nm , as with NH 2 -ONT 10nm , were formed from a rolled bolaamphiphile layer incorporating triglycine moieties, whereas COOH-ONT 20nm consisted of four stacks of triglycine-free bolaamphiphile layers. Imaging FCS measurements were carried out for anionic sulforhodamine B (SRB), zwitterionic/cationic rhodamine B (RB), and cationic rhodamine-123 (R123) diffusing within ONTs (1−9 μm long) at different pH (3.4−8.4) and ionic strengths (1.6−500 mM). Diffusion coefficients (D) of these dyes in the ONTs were very small (0.01−0.1 μm 2 /s), reflecting the significant contributions of molecule-nanotube interactions to diffusion. The D of SRB was larger at higher pH and ionic strength, indicating the essential role of electrostatic repulsion that was enhanced by the deprotonation of the inner carboxyl groups. Importantly, the D of SRB was virtually independent of nanotube inner diameter and wall structure, indicating the diffusion of the hydrophilic molecule was controlled by short time scale adsorption/desorption processes onto the inner surface. In contrast, pH effects on D were less clear for relatively hydrophobic R123 and RB, suggesting the significant contributions of non-Coulombic interactions. Interestingly, the diffusion of these molecules in COOH-ONT 20nm was slower than in COOH-ONT 10nm . Slower diffusion in COOH-ONT 20nm was attributable to relatively efficient partitioning of the hydrophobic dyes into the bolaamphiphile layers, which was reduced in COOH-ONT 10nm due to the stabilization of its layer by polyglycine-II-type hydrogen bonding networks. These results show that, by tuning the bolaamphiphile structures and their intermolecular interactions, unique environments can be created within the nanospaces for enhanced molecular separations and reactions.

This paper reports the applicability of a dimethyl sulfoxide (DMSO) solution of stannous acetate (Sn(OAc) 2 /DMSO) for sensitization in electroless deposition (ELD). Silver ELD was examined on nanostructured surfaces derived from polystyrene-blockpoly(methylmethacrylate) via sensitization with an aqueous or DMSO solution of Sn(OAc) 2 or SnCl 2 , activation with aqueous Ag[(NH 3 ) 2 ] + , followed by immersion in an aqueous solution containing [Ag(NH 3 ) 2 ] + and tartrate. Sensitization with 0.5 mM Sn(OAc) 2 /DMSO led to the preferential deposition of silver nanoparticles (Ag-NPs) on the nanoscale ridges of the polymer film upon 10-minute ELD. In contrast, Ag-NPs were negligibly deposited on the polymer film sensitized with 0.5 mM SnCl 2 /DMSO. Conventional sensitization solutions based on aqueous SnCl 2 (SnCl 2 /H 2 O) required a much higher Sn(II) concentration (≥5 mM) for sensitization of the polymer surface. X-ray photoelectron spectroscopy results supported the stoichiometric formation of Ag 0 from Sn(II) in the activation step on the polymer surface sensitized with Sn(OAc) 2 /DMSO as with 50 mM SnCl 2 /H 2 O. Sn(OAc) 2 /DMSObased sensitization was inefficient on thiolate self-assembled monolayers. The efficient sensitization of the polymer surface with Sn(OAc) 2 /DMSO was explained by the reduction of hydroxide formation by the use of the organic solution and efficient partitioning of Sn(OAc) 2 into the solvent-swollen surface region of the polymer film.