Insight into the Photo-induced melting of AuNR and Length Effect in AuNR-silica core-shell nanosystem
| Autor: | Wu, JUNG-HSIEN, 吳榮憲 |
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| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 This study focused on the relationship between the photoinduced melting and the isotropic heat release in the core-shell particle (AuNR-nu-SiO2) system in which the gold nanoparticles were coated in an non-uniform silicon dioxide shell. Furthermore, the relationship between the aspect ratio and the split-melting ratio is further discussed in this nanoscale system. In our previous study, it is known that the photoinduced melting of gold nanorods in this system can affect the heat release rate of different directions due to the conditions of the shell and the types of interfaces. However, the numerical value of the heat release rate cannot be directly quantified, so the validity of this phenomenon is limited. We use Fourier heat conduction formula to quantify the heat transfer rate along the two different directions of the gold nanorods with the known heat transfer coefficient. The results show that the ratio of the split product can be clearly presented through the change of two parameters: total heat release rate (qtotal) and isotropic heat release ratio (Qanisotropic). The temperature difference between the center of the gold nanorods and the two ends is the main factor to determine the yield of the split-melting. The larger temperature difference, the higher ratio of split-melting will be, and the difference is directly proportional to Qanisotropic. And the other key factor that determines whether the spilt phenomenon occurs is the qtotal value, If the value of qtotal is too large, the overall temperature of the gold nanorods will decrease and the temperature in the center of the gold nanorods is not enough to produce the melting phenomenon. In addition to that, it is mainly to change the shell layer condition and the interface type in the previous nanosystem, therefore, we specially designed a new system, fixed the shell layer and the interface parameters and adjusted the aspect ratio of gold nanorod to explore the effect of photoinduced melting phenomena. the results showed that when the aspect ratio was 5 ~ 6, the proportion of spilt- melting was about 35 %, and the aspect ratio was less than 3.8, the melting did not occur with the spilt. We believe that the temperature difference between the center and the two end needs to be greater than a threshold, so that the gold rods can form a spilt product. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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