Synthesis and Ultrafast Study of Cysteine- and Glutathione-Capped Ag2S Semiconductor Colloidal Nanoparticles
Citations Over TimeTop 10% of 1999 papers
Abstract
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.
Related Papers
- → Deep-Level Defect Effects on the Low-Temperature Photoexcitation Process in CdZnTe Crystals(2019)4 cited
- → Carrier photoexcitation from levels in quantum dots to states of the continuum in lasing(2001)6 cited
- → Potential Modulation of Semiconductor Dot Array System due to Photoexcitation(1999)3 cited
- → Femtosecond photoexcitation dynamics in polydiacetylene 4BCMU film(1997)
- → The application of femtosecond time-resolved CARS-spectroscopy for the characterization of vibrational modes upon photoexcitation(2004)