I  U  P  A  C

News & Notices

Organizations & People

Standing Committees




..Macro. Symp.

..Solubility Data



Links of Interest

Search the Site

Home Page


Pure Appl. Chem. Vol. 72, Nos. 1-2, pp. 165-177, 2000

Special Topic Issue on the Theme of
Nanostructured Systems


High-density femtosecond transient absorption spectroscopy of semiconductor nanoparticles. A tool to investigate surface quality

C. Burda* and M. A. El-Sayed

*Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400 USA

Abstract: At the high laser excitation intensities used in our experiments, more than 50 electron-hole pairs are formed in colloidal semiconductor nanoparticles used in our studies. At this density of charge carriers, new transient absorptions are observed in the femtosecond transient spectra in the 450 to 700 nm region with unresolved fast rise (<100 fs) and two decay components of 660 fs and >150 ps. The absorption at 510 nm could be quenched with the adsorption of electron acceptors (e.g., benzoquinone, 1,2-naphthoquinone), whereas the low-energy transient absorption was not affected. For CdS NPs, we found that passivation eliminated most of the transient absorption. The transient absorptions are thus proposed to result from either trap-state absorption, trapped dimers (or complexes) and/or Stark-shifted exciton absorption resulting from surface electric field of the uncompensated trapped electron-hole pairs. All these possibilities require effective surface trapping at these high levels of excitation.

Back to Contents for access to full text

Page last modified 5 May 2000.
Copyright ©2000 International Union of Pure and Applied Chemistry.
Questions or comments about IUPAC, please contact, the Secretariat.
Questions regarding the website, please contact web manager.