• Kim, Seong-Kyu (Department of Chemistry, Sung Kyun Kwan University, Suwon, 440-746, KOREA)
  • Published : 1997.03.01


We measured, using femtosecond pump-probe experiment, the time evolution of transient absorption in aqueous CdS colloids. The signal rises within the time resolution (= 0.5 ps) of the experiment and decays with two exponential time constants, 4.8 ps and 132 ps. The ultrafast rise of the transient absorption is considered to be for shallowly trapped conduction band electrons after photoexcitation. The amplitude ratio of the two decaying components varies with the pump intensity and the decay times increase in the presence of hole scavengers. Even though a biexponential function fits the decay well, we object hat two independent first order processes (geminate and nongeminate recombinations) are responsible for the decay. A function with an integrated rate equation for second order nongeminate recombination plus a long background fits the decay well. The long background is considered to be for deeply trapped charges at the CdS particle.



  1. Photocatalysis, Fundamentals and Applications Serpone, N.;E. Pelizzetti
  2. Energy Resources through Photochemistry and Catalysis Gratzel, M.
  3. Chem. Rev. v.93 Photochemistry on nonreactive and reactive (semiconductor) surface Kamat, P. V.
  4. Chem. Rev. v.93 Heterogeneous photocatalysis Fox, M. A.;M. T. Dulay
  5. Pure & Appl. Chem. v.56 Catalysis of photochemical reactions by colloidal semiconductors Henglein, A.
  6. J. Phys. Chem. v.89 Luminescence of colloidal CdS particles in acetonitrile and acetonitrile/water mixture Ramsden, J. J.;S. E. Webber;M. Gratzel
  7. J. Phys. Chem. v.92 Photochemistry of colloidal semiconductors. 26. Photoelectron emission from CdS particles and related chemical effects Hasse, M.;H. Weller;A. Henglein
  8. J. Phys. Chem. v.91 Photoelectrochemistry in particulate systems. 6. Electron-transfer reactions of small CdS colloids in acetonitrile Kamat, P.V.;N. M. Dimitrijevic;R. W. Fessenden
  9. J. Phys. Chem. v.90 Picosecond resonance raman scattering study of methylviologen reduction on the surface of photoexcited colloidal CdS crystallites Rossetti, R.;L. E. Brus
  10. J. Am. Chem. Soc. v.114 Semiconductor nanocrystals covalently bound to metal surfaces with self-assembled monolayers Colvin, V. L.;A. N. Goldstein;A. P. Alivisatos
  11. J. Phys. Chem. v.98 Femtosecond studies of photoinduced electron dynamics at the liquid-solid interface of aqueous CdS colloids Zhang, J. Z.;R. H. O'Neil;T. W. Roberti
  12. J. Chem. Phys. v.89 Electronic states of semiconductor clusters: Homogeneous and inhomogeneous broadening of the optical spectrum Alivisatos, A. P.;A. L. Harris;N. J. Levinos;M. L. Steigerwald;L. E. Brus
  13. J. Phys. Chem. v.89 Size quantization in small semiconductor particles Nozik, A. J.;F. Williams;M. T. Nenadovic;T. Rajh;O. I. Micic
  14. J. Phys. Chem. v.95 Local field effect in small semiconductor clusters and particles Wang, Y.
  15. Chem. Phys. Lett. v.208 A quantum dot quantum well: CdS/HgS/CdS Eychmuller, A.;A. Mews;H. Weller
  16. Chem. Phys. Lett. v.203 Detection of shallow electron traps in quantum sized CdS by fluorescence quenching experiments Hasselbarth, A.;A. Eychmuller;H. Weller
  17. Chem. Phys. Lett. v.132 Formation and decay of methylviologen radical cation dimers on the surface of colloidal CdS : Separation of two-and three-dimensional relaxation Ramsden, J. J.;M. Gratzel
  18. Chem. Phys. Lett. v.168 Ultrafast electron reaction and trapping in semiconductor colloids after multiple photon absorption Kaschke, M.;N. P. Ernsting;U. Muller;H. Weller
  19. J. Phy. Chem. v.99 Femtosecond investigation of electron trapping in semiconductor nanoclusters Skinner, D. E.;D. Colombo, Jr.;J. J. Cavaleri;R. M. Bowman
  20. J. Chem. Phys. v.101 Femtosecond studies of interparticle electron transfer in a coupled CdS-TiO₂colloidal system Evans, J. J.;K. W. Springer;J. Z. Zhang
  21. J. Opt. Soc. Am. v.B7 Quantum simulation of ultrafast spectroscopy Rossky, P. J.
  22. J. Opt. Soc. Am. v.B7 Colloidal zinc cadmium sulfide (Zn₁$_xCd_xS$): Optieal saturation of the exction band and primary photochemistry studied by subpicosecond laser flash photolysis Ernsting, N. P.;M. Kaschke;H. Weller;I, Katsikas
  23. J. Am. Chem. Soc. v.107 Charge carrier trapping and recombination dynamics in small semiconductor particles Rothenberger, G.;J. Moser;M. Gratzel;N. Serpone;D. K. Sharma