Preparation and Characterization of Tetracomponent ZnO/SiO₂/SnO₂/TiO₂ Composite Nanofibers by Electrospinning

[Zn(CH ₃COO) ₂ + PVP]/[C ₂H ₅O) ₄Si + PVP]/[SnCl ₄ + PVP]/[Ti(OC ₄H ₉) ₄ + CH ₃COOH + PVP] precursor composite fibers have been fabricated through self-made electrospinning equipment via electrospinning tech-nique. ZnO/SiO ₂/SnO ₂/TiO ₂ composite nanofibers were obtained by calcination of the relevant precursor composite fibers. The samples were characterized by thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and Scanning electron microscopy (SEM). TG-DTA analysis reveals that solvents, organic compounds and inorganic in the precursor composite fibers are decomposed and volatilized totally, and the mass of the samples kept constant when sintering temperature was above 900?C, and the total mass loss percentage is 88%. XRD results show that the precursor composite fibers are amorphous in structure, and pure phase ZnO/SiO ₂/SnO ₂/TiO ₂ com-posite nanofibers are obtained by calcination of the relevant precursor composite fibers. FTIR analysis manifests that pure inorganic oxides are formed. SEM analysis indicates that the width of the precursor composite fibers is ca. 1.485 ± 0.043 μm. The width of the ZnO/SiO ₂/SnO ₂/TiO ₂ composite nanofibers is ca. 1145.098 ± 68.093 nm.

• ZnO/SiO₂/SnO₂/TiO₂
• Tetracomponent
• Composite Nanofibers
• Electrospinning

1. Introduction

One-dimensional nanomaterials, such as nanofibers, nanowires, nanobelts, nanoribbons, and nanorods, are a new class of nanomaterials that have been attracting a great research interest in the last few years. These materials have been demonstrated to exhibit superior optical, acoustic, electrical, magnetic, thermal, and mechanical properties, and thus, can be used as both interconnects and functional components in the fabrication of nanoscale electronic and optoelectronic devices. Electrospinning technique as a simple, convenient, and versatile method has been utilized in the preparation of many one-dimensional nanostructural materials such as long fibers with diameters ranging from tens of nanometers up to micrometers [1]. It has been used to produce variety of materials, such as rare earth oxyfluoride [2], GGG: Eu³⁺ nanobelts [3], TiO₂ nanobelts [4], PANI nanobelts [5], three mixed oxides(Co₃O₄,CuO, and MnO₂) nanobelts [6] and TiO₂@SiO₂ nanocables [7] through electrospinning technique. Recently, this technique was used as an approach to fabricate composite nanofibers. For example, Zhang, et al. [8] synthesized SnO₂/TiO₂ composite nanofibers through electrospinning technique. However, to the best of our knowledge, there have been no reports on the preparation of ZnO/SiO₂/SnO₂/TiO₂ composite nanofibers by electrospinning technique. Synthesis of composite nanofibers materials with unique optical, electronic, magnetic, and catalytic properties, which are fundamentally important and technologically useful. In this paper, ZnO/SiO₂/SnO₂/TiO₂ composite nanofibers were fabricated by calcination of the electrospun [Zn(CH₃COO)₂ + PVP]/[C₂H₅O)₄Si + PVP]/[SnCl₄ + PVP]/[Ti(OC₄H₉)₄ + CH₃COOH + PVP] precursor composite fibers, and some new results were obtained and this preparation technique can be applied to prepare other composite nanofibers.

2. Experimental Section

2.1. Chemicals

Polyvinyl pyrrolidone (PVP) (Mw = 1,300,000, AR), ethanol (CH₃CH₂OH), butyl titanate (Ti(OC₄H₉)₄), zinc acetate (Zn(CH₃COO)₂·2H₂O), stannic chloride (SnCl₄·5H₂O), tetraethyl orthosilicate ((C₂H₅O)₄Si), acetic acid (CH₃COOH) and N,N-dimethylformamide (DMF, AR) were bought from Tiantai Chemical Co. Ltd., All chemicals were analytically pure and directly used as received without further purification.

2.2. Preparation of Precursor Composite Sol

2.4 g of PVP powders and 1.8 g of Zn(CH₃COO)₂·2H₂O were dissolved in 16 g of DMF, and stirred at room temperature for 10 h. The above sol was placed in an airtight container for about 5 h, and then, transparent viscous sol of [Zn(CH₃COO)₂ + DMF + PVP] was obtained; 2.5 g of PVP powders and 5 ml of (C₂H₅O)₄Si were dissolved in10 ml of CH₃CH₂OH, and stirred at room temperature for 10 h. The above sol was placed in an airtight container for about 5 h, and then, transparent viscous sol of [(C₂H₅O)₄Si + CH₃CH₂OH + PVP] was obtained; 2.5 g of PVP powders and 1.8 g of SnCl₄·5H₂O were dissolved in 20 ml of DMF, and stirred at room temperature for 10 h. The above sol was placed in an airtight container for about 5 h, and then, transparent viscous sol of [SnCl₄ + DMF + PVP] was obtained; 2.0405 g of PVP powders and 17 ml of CH₃CH₂OH and 3 ml of CH₃COOH were dissolved in 5 ml of Ti(OC₄H₉)₄, and stirred at room temperature for 10 h. The above sol was placed in an airtight container for about 5 h, and then, transparent viscous sol of [Ti(OC₄H₉)₄ + CH₃CH₂OH + CH₃COOH + PVP] was obtained.

2.3. Characterization Methods

XRD analysis was performed on a Holland Philip Analytical PW1710 BASED X-ray diffractometer using Cu Kα₁ radiation, with the working current and voltage at 30 mA and 40 kV, respectively. Scans were made from 10˚ to 90˚ at the speed of 4 (˚)/min, and the step was 0.02˚. The morphology and size of the samples were observed with an S-4200 scanning electron microscope made by Japanese Hitachi Company. TG-DTA analysis was carried out on an SDT-2960 thermal analyzer made by American TA instrument company in atmosphere, and the temperature rising rate was 10˚C/min. FTIR spectra of the samples were recorded on BRUKER Vertex 70 Fourier transform infrared spectrophotometer made by Germany Bruker company, and the specimen for the measurement was prepared by mixing the samples with KBr powders and then the mixture was pressed into pellets, the spectrum was acquired in a wave number range from 4000 cm^–1 to 400 cm^–1 with a resolution of 4 cm^–1.

2.4. Preparation of ZnO/SiO 2 /SnO 2 /TiO 2 Composite Nanofibers

Schematic diagram of electrospinning setup was shown in Figure 1. The above precursor sol were placed in four focusing syringes and delivered at a constant flow rate using plastic capillaries. The anodes were placed in the sol, and a grounded aluminum foil served as counter electrode and collector. When a high voltage (26 kV in this work) was applied, and the distance between the capillary tip and the collector was fixed to 18 cm, a dense web of [Zn(CH₃COO)₂ + PVP]/[C₂H₅O)₄Si + PVP]/[SnCl₄ + PVP]/[Ti(OC₄H₉)₄ + CH₃COOH + PVP] precursor composite fibers were collected on the aluminum foil. These fibers were calcinated at a rate of 1˚C/min and remained for 8 h at 900˚C, respectively. Thus, ZnO/SiO₂/ SnO₂/TiO₂ composite nanofibers were obtained.

3. Results and Discussion

3.1. TG-DTA Analysis

Figure 2 shows the thermal behavior of precursor composite fibers. The weight loss was involved in four stages in TG curve. The first weight loss is 19% in the range of 40˚C to 277˚C accompanied by a small endothermic peak near 83˚C in the DTA curve, which is caused by the loss of the surface absorbed water or the residual water molecules in the precursor composite fibers. The second weight loss step (27%) is between 277˚C and 340˚C accompanied by an exothermic peak near 330˚C in the DTA curve because of the decomposition of the Ti(OC₄H₉)₄, CH₃COOH and side-chain of PVP. The third weight loss (36%) in the TG curve (340˚C - 503˚C) was possibly corresponded to the decomposition of SnCl₄·5H₂O, Zn (CH₃COO)₂·2H₂O [9], (C₂H₅O)₄Si [10] and main-chain of PVP. In the DTA curve, an exothermic peak was located at 470˚C. The last weight loss is 6% in the temperature change from 503˚C to 900˚C. In the DTA curve a sharp exothermic peak is located at 574˚C. This is likely to be the totally oxidation combustion of the inorganic salts. And above 900˚C, the TG and DTA curves were all unvaried, indicating that water, organic compounds and inorganic salts in the precursor composite fibers were completely volatilized and pure ZnO/SiO₂/ SnO₂/TiO₂ composite nanofibers could be obtained above

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