Tabor, Christopher and Qian, Wei and El-Sayed, Mostafa A. (2007) Dependence of the threshold energy of femtosecond laser ejection of gold nanoprisms from quartz substrates on the nanoparticle environment. JOURNAL OF PHYSICAL CHEMISTRY C, 111 (25). pp. 8934-8941.
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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp070282q
Recently, it was reported that gold nanoprisms in a monolayer array on a quartz substrate were ejected in air when irradiated with femtosecond laser pulses near their surface plasmon absorption maximum. It was deduced from the measured reduction in particle thickness upon irradiation that the ejection mechanism involved ablation of surface atoms from the gold particle, which generates an intense pressure at the particle-substrate interface. The present study reports on this phenomenon when the substrate-bound nanoparticle is immersed in a liquid environment. In this system, it is found that the nanoparticle ejection requires less than one tenth the energy required if the system was irradiated in air. The ejected nanoparticle is also found to increase in thickness instead of the decrease observed in air. These results suggest another photoinitiated ejection mechanism, different from surface ablation, when the particles are surrounded by a liquid environment. From this and other spectroscopic and microscopic results on the ejected nanoprisms, we suggest a mechanism that involves energy transfer from the photoexcited nanoprism to the solvent within cavities and defects at the particle-substrate interface. The hot-solvent molecules result in an intense pressure at the particle-substrate interface, resulting in particle ejection. Ejection is proposed to consist of two processes, namely nanoparticle-substrate dissociation and nanoparticle solvation and diffusion away from the substrate. These two processes have independently been studied as a function of solvent property.
|Subjects:||Physical Science > Nanophysics|
Physical Science > Photonics
|Deposited By:||Farnush Anwar|
|Deposited On:||16 Jan 2009 15:39|
|Last Modified:||29 Jan 2009 11:33|
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