Metal Oxide/TiO₂ Hybrid Nanotubes Fabricated through the Organogel Route.

Masahiro Suzuki,Keita Tanaka,Yukie Kato,Kenji Hanabusa

doi:10.3390/gels3030024

Abstract

Titanium dioxide (TiO2) nanotube and its hybrid nanotubes (with various metal oxides such as Ta2O5, Nb2O5, ZrO2, and SiO2) were fabricated by the sol-gel polymerization in the ethanol gels formed by simple l-lysine-based organogelator. The self-assembled nanofibers (gel fibers) formed by the gelator functioned as a template. The different calcination temperatures gave TiO2 nanotubes with various crystalline structures; e.g., anatase TiO2 nanotube was obtained by calcination at 600 °C, and rutile TiO2 nanotube was fabricated at a calcination temperature of 750 °C. In the metal oxide/TiO2 hybrid nanotubes, the metal oxide species were uniformly dispersed in the TiO2 nanotube, and the percent content of metal oxide species was found to correspond closely to the feed ratio of the raw materials. This result indicated that the composition ratio of hybrid nanotubes was controllable by the feed ratio of the raw materials. It was found that the metal oxide species inhibited the crystalline phase transition of TiO2 from anatase to rutile. Furthermore, the success of the hybridization of other metal oxides (except for TiO2) indicated the usefulness of the organogel route as one of the fabrication methods of metal oxide nanotubes.

Highlights

Low-molecular-weight gelators and their supramolecular gels have been actively investigated, and many gelators have been reported [1,2,3,4,5,6,7,8,9,10,11]
The nanostructures of self-assembled nanofibers created in the supramolecular gels have a high utilization value as a template because the gelators can construct various nanostructures such as twisted nanoribbons, coiled nanorods, and helical nanofibers and nanotubes [10]
Shinkai and co-workers are a pioneer in the template-synthesis of metal oxides using low-molecular-weight gelators [30,31]

Summary

Introduction

Low-molecular-weight gelators and their supramolecular gels have been actively investigated, and many gelators have been reported [1,2,3,4,5,6,7,8,9,10,11]. Most of low-molecularweight gelators create three-dimensional networks by the entangling of self-assembled nanofibers through non-covalent interactions [1,2,3,4,5,6,7,8,9,10,11]. The nanostructures of self-assembled nanofibers created in the supramolecular gels have a high utilization value as a template because the gelators can construct various nanostructures such as twisted nanoribbons, coiled nanorods, and helical nanofibers and nanotubes [10]. Shinkai and co-workers are a pioneer in the template-synthesis of metal oxides using low-molecular-weight gelators [30,31]. The nanotubes and nanofibers of SiO2 , TiO2 , ZrO2 , Ta2 O5 , Nb2 O5 , and vanadium oxide have been successfully fabricated using gelators [11,32,33,34,35,36,37,38,39,40]

Methods

Results

Conclusion