Synthesis of Antimony Nanotubes via Facile Template-Free Solvothermal Reactions
Uniform antimony (Sb) nanotubes were successfully synthesized via a facile solvothermal method without the need for any surfactants or templates. The Sb nanotubes are confirmed to be pure rhombohedral phase and have better crystallinity. These nanotubes show middle-hollow and open-ended structures, as well as multi-walled structures with the wall thickness of about 10 nm. Also, they have an average size of the diameter of about 50 nm and the length of about 350 nm. On the basis of the structural and morphological studies, a possible rolling mechanism is proposed to explain the formation of Sb nanotubes. It is expected that uniform Sb nanotubes can further be used in wide applications.
KeywordsSb nanotubes Solvothermal synthesis Rolling mechanism
Since the discovery of carbon nanotubes, one-dimensional nanotubes have attracted much attention due to their peculiar physical properties and promising applications as interconnect and functional units in fabricating electronic, optoelectronic, thermoelectric, and electromechanical nanodevices and so on [1, 2, 3, 4]. So far, a large number of reports have focused on the exploring whether other layered materials also can form tubular or similar nanostructures. Through constant efforts, various nanotubes have been successfully synthesized by means of their two-dimensional layer structure, such as boron nitride (BN), titanium dioxide (TiO2), tungsten disulfide (WS2), bismuth sulfide (Bi2S3), bismuth (Bi), and so on [5, 6, 7, 8, 9]. All the above mentioned reports indicate that substance possessing lamellar structures might be able to form nanotubes under favorable conditions. Similar to that of Bi, semimetallic antimony (Sb) has also a pseudolamellar structure and has interesting features such as low conduction band, effective mass, and high electron mobility [10, 11, 12, 13]. In particular, the effective mass components of the electron ellipsoids in Sb are much larger than those in Bi, while the effective mass components of the hole ellipsoids of Sb are of the same order of magnitude as those in Bi . Thus, the particular transport properties of the electron can be expected in one-dimensional nanostructures of Sb, which make it become an interesting system for studying quantum confinement effects . Among them, Sb nanowires have exhibited the interesting electronic properties, such as surface superconductivity, extremely large magnetoresistance, and high efficiency thermoelectricity generation [16, 17]. Recently, Sb nanowires have been synthesized by the pulsed electrodeposition and vapor phase deposition in anodic alumina templates [18, 19], self-assembly on graphite templates , and surfactant-assisted solvothermal synthesis [21, 22]. In addition, Sb nanotubes have been synthesized via the reduction acetylacetone-assisted antimony complexes process . To the best of our knowledge, the template-assisted or the surfactant-assisted methods are the most popular synthetic strategies for the synthesis of one-dimensional nanostructures of Sb, which can control the oriented growth or uniform dispersal of nanomaterials. Unfortunately, the removal of the templates will give rise to poorly defined nanostructures from complex procedure, or the existence of organic surfactant will affect the properties of the Sb nanomaterials, which consequently have limited their large-scale production and further potential applications. However, there have been very few literature reports on the syntheses of Sb nanotubes by using without template-assisted or surfactant-assisted method. Therefore, it is highly desirable and significant, as well as a big challenge, to develop a facile route to directly synthesize the relatively straight and uniformly dispersed nanotubes of Sb.
Herein, we have synthesized relatively straight and uniform Sb nanotubes via a facile solvothermal method without any surfactants or templates. The synthesized Sb nanotubes are confirmed to be pure rhombohedral phase and show better crystallinity. The Sb nanotubes have middle-hollow, open-ended structures, and an average size of the diameter of about 50 nm and the length of about 350 nm. Based on the morphologies and structures, the formation mechanism of Sb nanotubes is discussed.
Synthesis of Antimony Nanotubes
All the chemical reagents used in this experiment are analytical grade. In our synthetic system, antimony chloride (SbCl3) as the Sb source was reduced to form Sb nanotubes via a solvothermal reduction by Zn powder at 200 °C for 10 h. Toluene was selected as the solvent because it is stable and can dissolve SbCl3. In a typical process, SbCl3 (521 mg) was dispersed in toluene (40 ml) under vigorous stirring at 5000 rad/min for 30 min. Subsequently, the mixed solution was transferred into a Teflon-lined stainless steel autoclave (50 mL), followed closely by the addition of zinc powers (75 mg). The autoclave was filled with the mixed solution up to 80 % of its total capacity, then sealed and maintained at 200 °C for 10 h. When the reaction was finished, the resultants were filtered off and rinsed with absolute alcohol, dilute hydrochloric acid, and deionized water for three times, respectively, then dried at 50 °C under vacuum.
The XRD patterns of the products were collected on a Bruker (AXS D8) X-ray diffractometer with Cu Kα radiation (λ = 1.5406 Å). An accelerating voltage of 40 kV and emission current of 30 mA were adopted for the measurements. The morphologies of as-synthesized samples were characterized by field emission scanning electron microscope (FE-SEM, Hitachi-4800, Japan) and high-resolution transmission electron microscope (TEM, FEI Tecnai G2 F20, 200 kV). The local chemical compositions of the samples were examined by energy-dispersive X-ray spectroscopy (EDX) performed in the transmission electron microscope.
Results and Discussion
However, our understanding of the formation mechanism for Sb nanotubes is limited during the solvothermal process. Therefore, further investigations would be necessary to clarify in detail the mechanism.
Sb nanotubes were successfully synthesized via a facile solvothermal process without the need for any surfactants or templates. In the synthetic system, antimony chloride as the Sb source was reduced to form Sb nanotubes by using Zn powder in toluene solvent at 200 °C for 10 h. The XRD analysis confirms that the Sb nanotubes are pure rhombohedral phase. The images of SEM and TEM reveal that the samples are the coexisting structures of lamellar and tubular Sb, in which uniform Sb nanotubes have a middle-hollow, open-ended, and multi-walled structure. And the Sb nanotubes have an average size of about 50 × 350 nm and the wall thickness of about 10 nm. On the basis of the structural and morphological studies, a possible rolling formation mechanism is proposed to explain the formation of Sb nanotubes. It is expected that uniform Sb nanotubes can further be used in wide applications.
This work is supported by the National Natural Science Foundation of China (61307045, 61404009, 61474010, 61574022, 61504012, 61205038, 11404219, 11404161, 11574130, and 11274135), the Foundation of State Key Laboratory of High Power Semiconductor Lasers, the Developing Project of Science and Technology of Jilin Province (20130101026JC, 20160101255JC, 20160519007JH), the Project of Jilin Province Development and Reform (2014Y110), and the Project of Changchun Science and Technology (14KG018).
A task of the work was formulated by ZPW and XHW. RXL and XWW provided the idea and drafted the manuscript. JXP and HRZ carried out the synthesis of antimony nanotubes. XHM and YFL analyzed the X-ray diffraction patterns of the antimony nanotubes. JLT and DF participated in the SEM studies. BY and JF participated in the TEM studies. All authors read and approved the final manuscript.
Doctor RX L is a student of Changchun University of Science and Technology. His major research area is in nanomaterial science.
The authors declare that they have no competing interests.
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