Jump to main content
Jump to site search

Issue 14, 2012
Previous Article Next Article

Relaxation dynamics of Au25L18 nanoclusters studied by femtosecond time-resolved near infrared transient absorption spectroscopy

Author affiliations

Abstract

The relaxation dynamics of electronically excited [Au25(SR)18]q, where q = 0 or −1 and SR = S(CH2)2Ph, were studied using femtosecond time-resolved transient absorption spectroscopy. Nanoclusters excited by 400 nm light were probed using temporally delayed broad-bandwidth continuum probe pulses. Continuum pulses were generated in both the visible and near infrared (NIR) spectral regions, providing access to a wide range of transient spectral features. The use of NIR probe pulses allowed the relaxation dynamics of the excited states located near the HOMO–LUMO energy gap to be monitored in the probe step via the sp ← LUMO and sp ← LUMO+1 transitions. These NIR measurements yielded excited state absorption (ESA) data that were much less congested than the typical visible transient spectrum. For the neutral nanocluster, the time-domain data were composed of three components: (1) a few-picosecond decay, (2) a slower decay taking a few hundred picoseconds and (3) a non-decaying plateau function. Component 1 reflected energy relaxation to semi-ring ligand states; component 2 was attributed to relaxation via a manifold of states located near the HOMO–LUMO energy gap. Component 3 arose from slow radiative recombination. The dynamics of the anion depended upon the identity of the excited state from which the particle was relaxing. The LUMO+1 state of the anion exhibited relaxation dynamics that were similar to those observed for the neutral nanocluster. By comparison, the time-domain data observed for the LUMO state contained only two components: (1) a 3.3 ± 0.2 ps decay and (2) a 5 ± 1 ns decay. The amplitude coefficients of each component were also analyzed. Taken together, the amplitude coefficients and lifetimes were indicative of an activation barrier located approximately 100 meV above the HOMO–LUMO energy gap, which mediated a previously unobserved excited state decay process for [Au25(SR)18]0. These data suggested that NIR ESA measurements will be instrumental in describing the relaxation processes of quantum-confined nanoclusters.

Graphical abstract: Relaxation dynamics of Au25L18 nanoclusters studied by femtosecond time-resolved near infrared transient absorption spectroscopy

Back to tab navigation

Article information


Submitted
02 May 2012
Accepted
08 Jun 2012
First published
13 Jun 2012

Nanoscale, 2012,4, 4111-4118
Article type
Paper

Relaxation dynamics of Au25L18 nanoclusters studied by femtosecond time-resolved near infrared transient absorption spectroscopy

T. D. Green and K. L. Knappenberger, Nanoscale, 2012, 4, 4111 DOI: 10.1039/C2NR31080E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.


Social activity

Search articles by author

Spotlight

Advertisements