Synthesis and ultrafast study of cysteine- and glutathione-capped Ag2S semiconductor colloidal nanoparticles
Synthesis and ultrafast study of cysteine- and glutathione-capped Ag2S semiconductor colloidal nanoparticles
复制标题
DOI：
10.1021/jp991999j
复制
发表时间：
1999-12-09
影响因子：
2.9
通讯作者：
Mehra, RK
中科院分区：
文献类型：
--
作者：
Brelle, MC;Zhang, JZ;Mehra, RK
发展了一种制备半胱氨酸或谷胱甘肽修饰的硫化银纳米粒子的新方法。使用透射电子显微镜测定平均粒径为约9 nm。Ag 2S纳米颗粒的基态电子吸收光谱显示出从红光（600-800 nm）开始向较短波长的吸收截面的连续增加。使用飞秒瞬时吸收/漂白光谱测量了这些纳米颗粒中光致电子的超快动力学。在大多数情况下，研究的早期时间瞬态轮廓具有脉冲宽度限制（1 ns）。一个样品（GSH-1）显示漂白剂恢复，其在快速4.5 ps上升之后以类似的时间常数（>1 ns）逐渐接近基线。一个有趣的功率依赖性，观察到所有的样品：瞬态吸收的贡献变得更占主导地位的漂白随着激发强度的增加。一个简单的四态动力学模型的发展，以占动力学的主要特点表明，初始光激发填充的导带和耗尽的价带内的激光脉冲（1纳秒。该模型表明，不同样品之间观察到的动力学差异是由于深陷阱态的吸收截面不同。所观察到的激发强度的动力学依赖性是由于浅陷阱态饱和在高强度。
A new synthetic method has been developed for preparing silver sulfide, Ag2S, nanoparticles capped with cysteine or glutathione. The average particle diameter has been determined to be around 9 nm using transmission electron microscopy. The ground-state electronic absorption spectra of the Ag2S nanoparticles show a continuous increase in absorption cross section toward shorter wavelengths starting from the red (600-800 nm). Ultrafast dynamics of photoinduced electrons in these nanoparticles have been measured using femtosecond transient absorption/bleach spectroscopy. In most cases studied, the early time transient profiles feature a pulse-width limited (1 ns. One sample (GSH-1) shows a bleach recovery that gradually approaches the baseline with a similar time constant (>1 ns) following the fast 4.5 ps rise. An interesting power dependence was observed for all the samples: the transient absorption contribution becomes more dominant over bleach with increasing excitation intensity. A simple four-state kinetic model developed to account for the main features of the dynamics suggests that initial photoexcitation populates the conduction band and depletes the valence band within the laser pulse (1 ns. This model suggests that the difference in dynamics observed between the different samples is due to different absorption cross sections of deep trap states. The observed excitation intensity dependence of the dynamics is attributed to shallow trap state saturation at high intensities.