Tube Formation in Nanoscale Materials

Abstract

The formation of tubular nanostructures normally requires layered, anisotropic, or pseudo-layered crystal structures, while inorganic compounds typically do not possess such structures, inorganic nanotubes thus have been a hot topic in the past decade. In this article, we review recent research activities on nanotubes fabrication and focus on three novel synthetic strategies for generating nanotubes from inorganic materials that do not have a layered structure. Specifically, thermal oxidation method based on gas-solid reaction to porous CuO nanotubes has been successfully established, semiconductor ZnS and Nb 2 O 5 nanotubes have been prepared by employing sacrificial template strategy based on liquid-solid reaction, and an in situ template method has been developed for the preparation of ZnO taper tubes through a chemical etching reaction. We have described the nanotube formation processes and illustrated the detailed key factors during their growth. The proposed mechanisms are presented for nanotube fabrication and the important pioneering studies are discussed on the rational design and fabrication of functional materials with tubular structures. It is the intention of this contribution to provide a brief account of these research activities.

Síntese de nanotubos de oxido de vanádio pelo método hidrotérmico livre de templates

“…Entre as nanoestruturas os nanotubos têm atraído grande interesse desde a identificação de Iijima, (1991) de nanotubos de carbono, já pela particularidade de sua forma tubular, que permite acesso a três diferentes regiões de contato, superfície interna, externa e suas extremidades (YAN et al, 2008).…”

“…Yan et al, (2008) mostrou a utilização de um nanofio de ZnO como template para síntese de nanotubos de GaN, utilizando a Deposição de Vapor Químico metalorganicos (DVQ). No qual o nanofio de ZnO é facilmente extraído através de soluções acidas ou por tratamento de redução de alta temperatura.…”

“…Esta rota requer o uso de uma base, ou de um ácido ou de alta temperatura para removê-los, o que aumenta bastante o custo e o risco de fabricação em ampla escala (YAN et al, 2008), Além disso, estes moldes de estruturas constituídos de materiais orgânicos podem originar múltiplos problemas quando utilizados, como manejo de produtos tóxicos e corrosivos, contaminação de recursos hídricos e terrestres, poluição atmosférica (calcinação) e obstrução de poros do catalisador com a formação de coque em virtude da combustão incompleta durante o processo de calcinação (CALDEIRA, 2011).…”

Control parameters on the fabrication of ZnO hollow nanocolumns

“…ZnO nanostructured materials in different morphologies (thin films, nanocolumns, whiskers) have been obtained by many different deposition techniques but it was not until recently that hollow nanocolumn have been produced by means of combined electrochemical and chemical techniques [4][5][6][7]. In general, the importance of obtaining hollow nanostructures is twofold as they can increase the surface area on the one hand, and the hollow part can be functionalised, for instance, by filling with a psemiconductor to obtain a n-p junctions on the other hand.…”

Mild solution synthesis of plate-like and rod-like ZnO crystals

“…In recent years, much attention has been paid to nanostructure ZnO materials, and ZnO with different morphology, for example nanowire, nanorods, nanotubes, nanobelts, nanorings, nanoneedles, and hollow structures, etc., have been developed [1][2][3][4][5][6][7][8][9][10]. Many methods have been used for control of the morphology of ZnO crystals, for example pulsed laser deposition [11], chemical vapor deposition [12], spray pyrolysis [13,14], thermal evaporation [15], wet-chemical routes [16][17][18][19], etc., in which the mild solution process has become a favored method because of the mild reaction conditions and simplicity of the synthetic process.…”