Selective Deposition of Metal Nanoparticles Inside or Outside Multiwalled Carbon Nanotubes

Abstract

A general method is described for the deposition of metal nanoparticles selectively either inside or outside of carbon nanotubes (CNTs). The method is based on the difference in the interface energies of organic and aqueous solutions with the CNT surface. Because of their lipophilic character, the organic solvent better wets the surface of the nanotubes compared to water and penetrates into the inner volume. The precise control of the volume of each phase allows filling the CNT with the organic phase and covering its outer surface with the aqueous one. Hence, metal nanoparticles can be put with high selectivity either inside or outside the CNT, just by choosing in which solvent the metal precursor is dissolved. SEM, TEM, and 3D-TEM investigations show that a selectivity in localization close to 75% can be reached by this technique. The nanoparticles are homogeneously dispersed and present a narrow size distribution, centered on 5 nm. In this way, one can decorate either the inner or the outer surface of open CNTs, without the need of discriminating the diameter of the opening and without any further step of functionalization than a treatment with nitric acid.

Carbon nanotubes prepared by anodic aluminum oxide template method

“…Structural parameters of CNTs such as inner diameter, wall thickness, length, crystallinity, and electronic structure have a great influence on the performance of the supported particles or loaded matters [12][13][14][15]. Especially, the size of the CNT hollow core and electron density plays an important role in determining the property of the filled matters owing to the confinement effect and the difference in electron density between the exterior and interior CNT surface due to their different graphene curvature [14,16]. Some new phenomena were reported for the materials confined in CNT nanochannels, which have never been observed for their bulk counterparts [17][18][19].…”

Hydrogenation of Phenol over Pt/CNTs: The Effects of Pt Loading and Reaction Solvents

“…On the basis of research by Tessonnier et al [25], here we prepared Pt/CNTs catalysts through selective deposition of Pt nanoparticles inside and outside CNTs (Pt-in/CNTs and Pt-out/CNTs). For comparison, CNTs-supported Pt was also prepared via incipient wetness impregnation (Pt-imp/CNTs).…”

Carbon nanostructures with different dimensionality – From synthesis to applications

“…By suspending nanoparticles in aqueous or organic solvents, nanoparticles can be selectively deposited on either the outer or inner surface, respectively [207]. Catalytic tests were also performed on such nanotubes.…”