Glass - Back to the Future!

Presenting Author:
Balazs Kobzi

article posted 6 April 2016

Balazs Kobzi graduated at Eötvös Loránd University (Hungary) studying materials science, focusing on sol-gel method and preparing ceramics and glasses. After that he started his PhD studies concerning the synthesis of highly porous alumina systems. In 2015 he was accepted as a MEXT scholarship student and is now a PhD candidate at Tokyo Metropolitan University under the supervision of Prof. Shiro Kubuki. The main field is preparing visible light activated photocatalytic glasses, and determining the structure focusing on Mössbauer spectroscopy.

Preparation and structural analysis of SnOx.SiO2 visible light activated photocatalytic glasses by 119mSn-Mössbauer spectroscopy

Shiro Kubuki1, Balazs Kobzi1, Ernö Kuzmann2, Homonnay Zoltán2,Sinko Katalin2, Tetsuaki Nishida3

In the recent development of visible light activated photocatalysts a few reports concerning tin(II) containing materials show promising results [1,2]. Our main aim is to successfully prepare a glass containing tin(II) component with a high efficiency photocatalytic activity.

Figure 1. 119mSn-Mössbauer spectra of the glass made with SnCl2 measured at different T

The photocatalytic properties of the tin containing silicate glasses were tested by methylene blue (MB) degradation with UV-visible light absorption spectroscopy (UV-VIS) using visible light exposure. The structural analysis of these glasses was made by X-ray diffractometry (XRD) and 119mSn-Mössbauer spectroscopy at room temperature and 78 K. Through the preparation SnCl2, SnF2, Sn(COO)2 and SnO were used separately by a simple sol-gel method. The 119Sn-Mössbauer spectrum of the glasses heat treated at 300°C show only Sn(IV) at room temperature, which means most of the Sn(II) in the starting materials were oxidized through the synthesis most likely at the annealing. Only one glass, that is made from SnCl2, contains a larger amount of Sn(II) specimen (Figure 1). Due to the differences of the f-factor of Sn(IV) and Sn(II) in the function of the temperature, the doublets assigned to Sn(II) can be clearly seen at low temperature. XRD spectra indicates that the glasses stayed amorphous despite the 300°C heat treatment. The Tauc's plot yielded a band gap energy (Eg) of 2–3 eV for the glass prepared from SnCl2, others with only Sn(IV) content had the band gap energy close to SnO2 (3·88 eV). This means that the glass made by SnCl2 could be activated by visible light, others only by UV. The methylene blue (MB) degradation measurements proved this matter right. Adsorption of MB could be observed on the glass surface in most cases. Only the glass made from SnCl2 showed difference in between the light irradiated sample and the sample which was kept in dark. A 13·8×10-3 min-1 first order rate shows that this glass has a remarkable visible light photocatalytic activity.

Figure 2. First order rate of SnOx.SiO2 glasses prepared from SnCl2 (a); SnF2 (b); Sn(COO)2 (c); SnO (d)

This work is financially funded by TÉT_12_JP-1-2014-0025 and Grant-in Aid in Japan No. 26630321.

[1] W.Xia et al., Cryst. Eng. Comm., 16, 6841-6847 (2014).
[2] Y.He et al., RSC Adv., 4, 1266-1269 (2014).

1 Graduate School of Science and Engineering, Tokyo Metropolitan University. Minami-Osawa 1-1, Hachi-Oji, 192-0397, JAPAN
2 Faculty of Science, Eötvös Loránd University. Pázmány P. s. 1/A, 1117 Budapest, HUNGARY
3 Faculty of Humanity-Oriented Science and Engineering, Kinki University. Kayanomory 11-6, Iizuka, Tokyo 820-8555, JAPAN