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| The Optical Stability of SiNWs:Tb3+ and the Effects of Si Nanowires on Its Luminescent Properties |
| YANG Rui-chen1, GENG Xiao-pei1, FAN Zhi-dong1*, LI Xu2, MA Lei3, GAO Yong-hui1, FU Ying1, WANG Xin-xin4 |
1. Department of Mathematics and Physics, Chengde Petroleum College, Chengde 067000, China
2. College of Physics Science & Technology, Hebei University, Baoding 071002, China
3. College of Electronic and Informationl Engineering, Hebei University, Baoding 071002, China
4. Department of Computer Information and Engineering, Chengde Petroleum College, Chengde 067000, China |
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Abstract Fluorescent nanomaterials not only have the advantages of nanomaterials, but also have excellent optical properties. They are widely used in fluorescent labels, ion recognition, fluorescence immunoassays, optical imaging and medical diagnostics. Therefore, researches on the preparation, structure analysis and fluorescence characteristics of fluorescent nanomaterials have received much attention. In order to obtain Si-based fluorescent nanomaterial with high luminous intensity, high fluorescent quantum efficiency and better controlling of preparation process, the effects of Si nanowires on the luminescence properties and the optical stabilities of the samples were investigated. First, based on the solid-liquid-solid growth mechanism, Si nanowires were grown under the conditions of reaction temperature of 1 100 ℃, N2 gas flow rate of 1 500 sccm and growth time of 15～60 min. The Si nanowires with different lengths and distributions were grown on single-crystal Si(100) substrates with “polishing” and “pyramid” texture surfaces respectively. And the Si nanowires with density of about 108 and 1010 cm-2 were grown with Au or Au-Al alloy film as metal catalyst. Then, a series of fluorescent nanometers SiNWs:Tb3+ samples were prepared using L4514 automatic temperature control tube heating furnace based on high-temperature solid-state method under the temperature 1 100 ℃, doping time 60 min, N2 gas flow rate 1 000 sccm, different Si nanowire substrates and high-purity Tb4O7 (99.99%) powder as doping agent. Next, at room temperature, the photoluminescence characteristics of different samples were measured by the Hitachi F-4600 fluorescence spectrophotometer with the fixed excitation light wavelength of 243 nm, the excitation light slit of 2.5 nm, the emission light slit of 2.5 nm, the scanning wavelength range of 450～650 nm and the PMT voltage of 600 V. Finally, the optical stabilities of the fluorescent nanomaterial was experimentally tested, such as time stability (0～30 d), temperature stability (300～500 K), acid and alkali stability (pH 1 and pH 11), anti-photobleaching stability (0～120 min), etc. Besides the water solubility and the dispersibility were tested. The results showed that SiNWs:Tb3+ produced strong green light emission with Si nanowires substrate which was prepared with the growth time 30 min, the “pyramid” texture surface and Au as the metal catalyst. The peak of green emission was 554 nm，which belongs to energy level transition 5D4→7F5. At the same time, three bands appeared at wavelengths of 494, 593 and 628 nm, which belong to the energy levels transitions 5D4→7F6, 5D4→7F4 and 5D4→7F3, respectively. In addition, the sample was shown to have excellent optical stabilities such as time, temperature, acid-base, anti-photobleaching, good water solubility and dispersibility. When the temperature is increased to 500 K, the light emission intensity is reduced by only about 8.9%. The green light luminescence intensity of the sample is not attenuated when irradiated with an UV light source with a wavelength of 365 nm and a power of 450 W for 120 min. In the strong acid solution of pH=1, no attenuation was found in 120 min and the attenuation was less in 15 min in the strong alkaline solution of pH 11. Subsequently, the luminous intensity showed a slow decline, but the luminous intensity of the sample became extremely weak after 60 min. The analysis showed that there is a layer of SiO2 coating on the surface of SiNWs:Tb3+, and NaOH solution easily reacts with SiO2. As time increases, the SiO2 layer is destroyed, so the luminescence intensity of the sample decreases. There was no deposit found when the sample dissolved in water for 30 days. At the same time, the luminance of solution was uniform. After studying the process conditions such as preparation temperature, gas flow rate and doping time, the influence of Si nanowires on Tb3+ green light emission was studied in depth. The material showed good optical stabilities, water solubility and dispersibility. It has a certain application value as a fluorescent marker.
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Received: 2018-01-19
Accepted: 2018-05-02
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Corresponding Authors:
FAN Zhi-dong
E-mail: fanzhidong@126.com
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