Preparation and photocatalytic properties of SnO 2 nanomicrospheres

Abstract

SnO₂ nanomicropheres were prepared via hydro-thermal method, then the structure and micromorphology were characterized by XRD and SEM. The photocatalytic degradation ability of microspheres was studied by ultraviolet absorption. The material was pure SnO₂ nanomicrospheres with good crystallinity, uniform size, good dispersion, and strong photocatalytic degradation.

Keywords

Tin oxide nanomicrosphere photocatalysis

1 Introduction

Tin oxide (SnO₂), with tetragonal rutile structure is an important wide band gap metal oxide semiconductor material. Because of the unique gas sensing, photoelectric properties and special microstructure [1], it has been applied in many fields, such as gas sensing element, photo catalyst, optoelectronic device, gas sensors, electrode material for Li ion battery, solar cells, glass coating and so on [2]. So, it has caused the interest of many researchers, and the research on it is also more and more deeply, from traditional nanoparticles to nanowires, nanobelts, nanotubes, nanorods, nanocones, nanocube structure research. For example, Yang, et al. synthesized tin dioxide nanowires using a direct gas reaction route [3]. Ye, et al. successfully synthesized SnO₂ nanotubes with controllable morphologies by using a variety of one-dimensional (1D) silica mesostructures as effective sacrificial templates [4]. Chen, et al. fabricated solid tin oxide (SnO₂) nanospheres were via one-step hydrothermal treatment of tin foil in aqueous alkaline solutions at 180°C [5], Yang, et al. successfully synthesized flower-shaped SnO₂ nanoplates via a simple hydrothermal treatment of a mixture of tin(II) dichloride dihydrate (SnCl₂·2H₂O) and sodium citrate (Na₃C₆H₅O₇·2H₂O) in alkali solution [6]. Qin, et al. successfully synthesized the SnO₂ cubes with the rutile structure based on aggration of nanorods [7]. Among all developed synthetic methods, the hydrothermal method based on a water system has attracted more and more attention because of its outstanding advantages, such as simple manipulation, easy control, uniform products, high yield, lower air pollution, low energy consumption, reaction in closed environment to avoid component evaporation, and this method could be conveniently scaled up for volume production [8 –10], thus, it has played a great role in the synthesis and structure control of SnO₂ nanoparticles [11 –13].

In this paper, Ph₃SnCl was used as resource of tin, which was affected by the temperature and pressure in hydrothermal process, Sn⁴⁺ would be free from the resource of tin, and react with OH^-, the intermediate product Sn(OH)₆^2– firstly formed in the alkaline solution, then, it would decompose to crystal nucleus SnO₂. With the reaction carrying out, the crystal nucleus grew continually, finally, formed the structure of the nanomicrospheres. Then, the products were obtained and characterized by X-ray diffraction analysis (XRD) and scanning electron microscope (SEM), which would observe microstructure and morphology of the products. Finally, the photocatalytic degradation ability of the products was studied.

2 Experimental section

2.1 Reagents and instruments

Triphenyltin chloride (Ph₃SnCl), ethanol, sodium hydroxide and oleinic acid were all of analytical reagent grade, which purchased from Beijing Chemical Factory (Beijing, China). Ultrapure water produced by ourselves. The used instruments included in magnetic stirring apparatus (S22-2, Shanghai Si Le Instrument Co., Ltd., China), vacuum drying oven (DZF-6090, Shanghai Jing Hong Laoratory Instrument Co., Ltd., China), centrifuge (TGL-15B, Shanghai An Ting Scientific Instrument Factory, China), and so on.

2.2 Characterization

Phase identification and crystal structure of products were performed via X-ray diffraction (D8 FOCUS, Bruker, Germany), and a scanning speed of 2θ = 8° per min, the working voltage and current were 40 KV and 30 mA, respectively. Microstructure and morphology of the products were observed by scanning electron microscope (S-4800, Hitachi, Japan) with 10 KV working voltage.

2.3 Synthesis

SnO₂ nanomicrospheres were synthesized by hydrothermal method using triphenyltin chloride as resource of tin under the optimum conditions as follows, 0.077 g Ph₃SnCl dissolved in 10 ml anhydrous ethanol, 0.1 mmol sodium hydroxide dissolved in 10 ml deionized water, then, the former solution was slowly added to the sodium hydroxide solution and stirred 10 min, subsequently, 4 ml oleic acid surface active agent was added and stirred well. After that, the above solution was added to 50 ml reaction kettle and heated to 180°C in the oven keeping 12 h. When the samples were cooled to room temperature, the samples were extracted with distilled water and ethanol, and then dried in the oven for 3 h under the temperature of 60°C, finally, white solid powder samples were obtained. Then, the powder samples were characterized by SEM and XRD.

3 Results and discussion

3.1 Analysis of XRD

Figure 1 showed the XRD of obtained products, comparing this pattern with the standard XRD cards of SnO₂ (JCPDS card, No. 41-1445), this spectrum could be in good agreement with that of standard SnO₂, and showed many standard diffraction peaks, without any other obvious peaks, which revealed that the products were pure phase SnO₂. Anymore, it could be seen from pattern that the half peak width was narrow, which meant the crystallinity of the products were high, and the grain size were large.

3.2 Analysis of SEM

Figure 2 showed the SEM with different magnification of SnO₂ products, from which we could see the obtained SnO₂ products were all nanospheres with rule shape, the surface of the spheres was smooth without any grain attached to that, the products particles were well dispersed and had even size.

3.3 Analysis of photocatalytic property

Experiment for degradation of organic dye rhodamine B was made by obtained SnO₂ nanosphere samples under the irradiation of ultraviolet light (500 W), the absorption spectra as shown in Fig. 3. As can be seen, the characteristic peak of rhodamine B was 554 nm, the characteristic peak intensity of rhodamine B decreased gradually with the increase of illumination time (from 0 min to 200 min), which indicated that the rhodamine B molecules were degraded. When the irradiation time reached 200 min, the degradation rate reached 97.1%, which indicated that the prepared SnO₂ nanomicrospheres had good photocatalytic effect under the irradiation of ultraviolet light.

4 Conclusions

In this paper, SnO₂ nanomicropheres were prepared via hydro-thermal method, then the structure and micromorphology were characterized, finally, the photocatalytic property of prepared products was tested. The experimental results showed the prepared samples were typical crystal of SnO₂ with tetragonal rutile structure, and the products were typical nanomicrosphere with good crystallinity, uniform size, good dispersion, and had good effect of photocatalytic degradation to organic dye rhodamine B, which provide a theoretical basis for further widening the application field.

Footnotes

Acknowledgments

Financial support from Jilin Provincial Development and Reform Commission Plan Project (2015Y058) is gratefully acknowledged.

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