Spectroscopic study of laser-induced phase transition of gold nanoparticles on nanosecond time scales and longer
Spectroscopic study of laser-induced phase transition of gold nanoparticles on nanosecond time scales and longer
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DOI：
10.1021/jp057175l
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发表时间：
2006-02-23
影响因子：
3.3
通讯作者：
Yamaguchi, Y
中科院分区：
文献类型：
--
作者：
Inasawa, S;Sugiyama, M;Yamaguchi, Y
通过纳秒级和更长时间尺度的瞬态吸收，观察到了脉冲激光诱导金纳米粒子在水溶液中的相变。金纳米粒子用强烈的皮秒激光脉冲（355 nm，30 ps）激发，并且使用两个连续波激光波长（488和635 nm）监测随后的变化。在纳秒时间尺度上，低于6.3 mJ cm（-2），没有观察到变化;然而，在6.3和17 mJ cm（-2）之间的低能量密度区域，金纳米颗粒产生归因于金纳米颗粒熔化的漂白信号（488 nm），其随着激光能量密度的增加而线性降低。当激光能量密度超过17 mJ cm（-2）时，两种波长下的吸收都很强，这是由于金纳米粒子的蒸发，而不是溶剂化电子（从金纳米粒子中射出）或光散射。这两个信号的衰减比我们实验系统中使用的5 ns时间分辨率更快。在微秒时间尺度上，在635 nm处观察到吸光度增加，时间常数为1.0 μ s，而在488 nm处没有观察到变化。据认为，这种增加是由于形成较小的金纳米粒子，导致脉冲激光诱导的初始金纳米粒子的尺寸减小。
The pulsed laser induced phase transition of gold nanoparticles in aqueous solution was observed via a transient absorption on nanosecond time scales and longer. Gold nanoparticles were excited with an intense picosecond laser pulse (355 nm, 30 ps), and the subsequent changes were monitored using two continuous wave laser wavelengths (488 and 635 nm). On the nanosecond time scale, below 6.3 mJ cm(-2), no change was observed; however, in the low fluence region between 6.3 and 17 mJ cm(-2), gold nanoparticles produced a bleach signal (488 nm) attributed to the melting of the gold nanoparticles, which decreased linearly with increasing laser fluence. Laser fluences above 17 mJ cm(-2) resulted in a strong absorption at both wavelengths, which is ascribed to vaporization of gold nanoparticles rather than solvated electrons (ejected from gold nanoparticles) or light scattering. The decay of both signals was faster than the 5 ns time resolution used in our experimental system. On the microsecond time scale, increase in absorbance at 635 nm was observed with a time constant of 1.0 mu s, while no change was observed at 488 nm. It is considered that this increase is attributed to the formation of smaller gold nanoparticles resulting from pulsed laser induced size reduction of initial gold nanoparticles.