| Hydrogen peroxide can be harmful to biological systems and appears to be involved in the neuropathology of central nervous system diseases. Hydrogen peroxide is an important trace gas that plays a significant role in the troposphere. In addition, H2O2 has an indirect impact on the acid rain procedure that is harmful to the atmosphere. So determine H2O2 is also very important.For the determination of H2O2, methods such as titrimetric,spectrophotometric, fluorescence, electrochemical, and chromatographic are usually used. To the best of our knowledge, a H2O2sensor based on room-temperature phosphorescence is seldom reported. We has prepared nanometer TiO2/SiO2 composite oxide by sol– gel. It produces highly emissive broadband phosphorescence from 450 to 650 nm at an excitation wavelength of 403 nm. The material could be used for the determination of trace hydrogen peroxide. We found that the intensity was reduced gradually as H2O2 concentration increased. The curve exhibits an excellent linear relationship when H2O2 concentration changed from 1×10-6 to 1×10-2 mol/L. Its linear equation could be represented as y=0.5924x-2.3841. The linear relative coefficient is R= 0.9955 and the detection limit is 5.6×10-7 mol/L. TiO2/SiO2 nanometer material is good response to H2O2.Furthermore, when added different concentration of H2O2 in the TiO2/SiO2 compound, it changed its color immediately. Redistilled water (1 drop) was added to the TiO2/SiO2 compound and it kept its original color; a light yellow developed immediately when the concentration of H2O2 solution was 1.0×10-3 mol/L, a deeper yellow color with 1.0×10-2 mol/L, and orange to 1.0 mol/L. Therefore, we can determine the concentration of H2O2 solution with the naked eye. The color change can be used as a colorimetric sensor for determining the presence of H2O2 in solution.The species in the scheme were confirmed with IR, XPS, ESR, and EXAFS.IR spectra suggest that the Ti-O-Si bond be present in TiO2/SiO2 composite oxide. According to the literature, the phosphorescence of TiO2/SiO2 is related to the Ti-O-Si stretching mode. However, after interaction with H2O2, anionic triangular Ti (O2-) was formed in the TiO2/SiO2 composite oxide, as supported by the XPS, ESR, and EXAFS. The oxidation state of Ti was confirmed by XPS. XPS showed increase of in binding energy of the Ti 2P3/2 electrons after adding H2O2 compared with that in the pure TiO2/SiO2, which indicates the formation of Ti-O-O-Si peroxo moieties in the TiO2/SiO2. To complement the XPS, the TiO2/SiO2 sample was further probedby ESR. The data reveal that, with the addition of H2O2 in the TiO2/SiO2 composite oxide, the Ti sites are highly reactive to H2O2 and form superoxide ion (O2-) with a characteristic average g value. These are also combined with EXAFS to supplement ESR result. Analysis of EXAFS gives valuable information regarding the environment of Ti center in TiO2/SiO2 oxides. EXAFS reports that the addition of H2O2 to TiO2/SiO2 composite oxide can affect the Ti environment by causing the cleavage of the silica network.Therefore, the formation of this triangular Ti(O2-) blocks the Ti-O-Si vibration, which results in the quenching of phosphorescence of TiO2/SiO2.In addition, the paper has prepared TiO2,SiO2 and nanometer TiO2/SiO2 composite oxide by sol– gel. The TiO2/SiO2 composite oxide has a higher surface area. After these products were dipped in 4×10-4 mol/L ethanolic solution of [Ru(bpy)3]Cl2 for 16h ,red fluorescence was observed under UV light. They can be excited by 468nm and has the maximal emission peak at600nm,the response to gaseous oxygen show that comparing with pure TiO2 and pure SiO2, TiO2/SiO2 composite oxide was sensitive to oxygen. |
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