高等学校化学学报

高等学校化学学报 ›› 2000, Vol. 21 ›› Issue (S1): 210.

• Chemistry in Materials Sciences • 上一篇    下一篇

Radiative and Nonradiative Lifetimes of Band Edge States and Deep Trap States of CdS Nanoparticles Determined by Time-correlated Single Photon Counting

WU F.1, J. ZHANG Z.1, KHO Richard2, MEHRA R. K.2, BECHTEL H.3, LOUNIS B.3, MOERNER W. E.3   

  1. 1. Department of Chemistry, University of California, Santa Cruz, CA 95064, USA;
    2. Department of Neuroscience, University of California, Riverside, CA 92521, USA;
    3. Department of Chemistry, Stanford University, Stanford, CA 95064, USA
  • 出版日期:2000-12-31 发布日期:2000-12-31

Radiative and Nonradiative Lifetimes of Band Edge States and Deep Trap States of CdS Nanoparticles Determined by Time-correlated Single Photon Counting

WU F.1, J. ZHANG Z.1, KHO Richard2, MEHRA R. K.2, BECHTEL H.3, LOUNIS B.3, MOERNER W. E.3   

  1. 1. Department of Chemistry, University of California, Santa Cruz, CA 95064, USA;
    2. Department of Neuroscience, University of California, Riverside, CA 92521, USA;
    3. Department of Chemistry, Stanford University, Stanford, CA 95064, USA
  • Online:2000-12-31 Published:2000-12-31

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摘要：

Emission lifetimes of band edge and deep trap states of CdS nanoparticles with different surface capping were measured using time-resolved single-photon-counting[1]. For unpassivated nanoparticles with low fluorescence yield, the emission is dominated by deep trap states and the decay can be fit to a single exponential with a time constant of 5 ns that is independent of excitation intensity. For surface passivated nanoparticles with strong luminescence, the emission is dominated by band edge states and the decay is fit to a double exponential with time constants of a few ns and 50 ns. While the 50 ns decay is independent of excitation intensity, the fast component is strongly dependent on intensity. For the fast decay component, the amplitude decreases non-linearly and the time constant becomes longer (from 2.5 to 7.9 ns) as the intensity decrease. The results support the model of exciton-exciton annihilation[2] upon trap state saturation at high excitation intensities.

Abstract:

Emission lifetimes of band edge and deep trap states of CdS nanoparticles with different surface capping were measured using time-resolved single-photon-counting[1]. For unpassivated nanoparticles with low fluorescence yield, the emission is dominated by deep trap states and the decay can be fit to a single exponential with a time constant of 5 ns that is independent of excitation intensity. For surface passivated nanoparticles with strong luminescence, the emission is dominated by band edge states and the decay is fit to a double exponential with time constants of a few ns and 50 ns. While the 50 ns decay is independent of excitation intensity, the fast component is strongly dependent on intensity. For the fast decay component, the amplitude decreases non-linearly and the time constant becomes longer (from 2.5 to 7.9 ns) as the intensity decrease. The results support the model of exciton-exciton annihilation[2] upon trap state saturation at high excitation intensities.

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