標題: Remarkable Photothermal Effect of Interband Excitation on Nanosecond Laser-Induced Reshaping and Size Reduction of Pseudospherical Gold Nanoparticles in Aqueous Solution
作者: Werner, Daniel
Hashimoto, Shuichi
Uwada, Takayuki
應用化學系
應用化學系分子科學碩博班
Department of Applied Chemistry
Institute of Molecular science
公開日期: 15-Jun-2010
摘要: An in situ spectroscopic study of the nanosecond laser-induced melting and size reduction of pseudospherical gold nanoparticles with 54 +/- 7 nm diameter allowed the observation of a heating efficiency that was very dependent on the excitation wavelength. A remarkably greater efficiency was observed for the photothermal effect of interband excitation than that of intraband excitation. This noteworthy observation is ascribed to an altered electron heat capacity, c(e), during photoexcitation depending on the excitation energy, which is a phenomenon that has not been realized previously. As a result, a 60% reduction of the specific heat capacity, c(p), compared to that of bulk gold was obtained for interband excitation at 266 nm whereas the c(p) value for the excitation of the intraband transition at 532 nm was unaltered. A semiquantitative explanation was given for this striking phenomenon induced by interband excitation in which excitation relaxation cycles of electrons upon excitation of 5d electrons to the 6sp band lead to a reduced number of electrons contributing to the electron temperature rise in the vicinity of the Fermi level during the nanosecond laser pulse duration. By contrast, electronic-excitation within the 6sp band results in no net reduction in the number of electrons near the Fermi level, giving rise to a value of c(p) similar to that of bulk gold. Our finding that the heat capacity of gold nanoparticles can be changed upon UV laser excitation is important for understanding the fundamental nature of noble metal nanoparticles. Furthermore, this finding might be useful for preparing new metal alloy particles as well as for manipulating the thermodynamic properties of the nanoparticles.
URI: http://dx.doi.org/10.1021/la100015t
http://hdl.handle.net/11536/5260
ISSN: 0743-7463
DOI: 10.1021/la100015t
期刊: LANGMUIR
Volume: 26
Issue: 12
起始頁: 9956
結束頁: 9963
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