Nanometric-scale rods, fibres or similar nanostructures of oxide materials, in particular TiO2, are usually prepared by means of chemical or electrochemical routes. These methods usually involve different steps of drying, heating or annealing at high temperature what might hamper their use when mild conditions are a requisite or when the synthesis has to be carried out in a single step. These shortcomings can be circumvented by plasma enhanced chemical vapour deposition (PECVD), a method that works at virtually any temperature and that permits the synthesis of the nanofibres in a single step. Carbon nanotubes (CNT) constitute a clear example of the use of electrical discharges or plasmas for the synthesis of nanostructures at low temperatures in a single step. In the present work, we report about the synthesis of supported Ag@TiO2 core-shell nanofibres by a new method based on the PECVD of titanium oxide on a silver substrate at t>130 °C.
Fibres of several microns length and a thickness varying between 30 and 400 nm were produced by our method. The obtainede fibres consist of one inner core made of a single crystalline silver thread of ca. 20 nm thickness and an external layer of either amorphous or crystalline anatase. The thickness of this external layer can be varied by just adjusting the TiO2 deposition time. Based on the morphology and other characterization results of these nano-fibres it has been proposed that the fibres grow according to a new "volcano" type mechanism.
The used methodology can be also used for the preparation of fibres of other oxides and selected examples are shown.
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