Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.

linking data were not interpreted using the power-law statistics, the kineticbehavior is consistent with our above description: The off times are independentof the oxygen molecules introduced; however, the on times show adramatic decrease in the maximum duration. The simulated time traces inFig. 11b, taking into account shorter termination points for the maximum ontime relative to the maximum off time, elucidates the difference in blinking atthe higher temperatures, higher excitation intensity, and poorer surfacepassivation. The change in the time traces is comparable between thesimulation in Fig. 11 and data in Fig. 2.Recent results on CdTe QDs, displayed in Fig. 12, show that the powerlawbehavior, its exponent, and the on-time phenomenology is reproduced,indicating that the effects observed are not unique to the particulars of CdSeQDs, but rather reflect more universal underlying physics of nanocrystal QDs.VI.CONCLUSIONSIn conclusion, extensive investigations into single-QD optical dynamics haveuncovered uniform properties in an inherently inhomogeneous system. First,the correlation between large spectral shifting events and blinking of singleQDs explains that spectral diffusion shifts, caused by electrostatic decorationspresent around every QD, is a direct consequence of the charging mechanismreported in the fluorescence intermittency process. Second, the probability ofeach QD turning on or off follows an unexpected, temperature-independentpower law. These power-law statistics observed for all the CdSe QDs studiedsuggest a complex, yet universal, tunneling mechanism for the blinking on andoff process. Third, the qualitative changes observed in the blinking behaviorare due to a secondary, thermally activated, and photoinduced process thatcauses the probability distribution of the on-time statistics to be truncated atthe ‘‘tail’’ of the power-law distribution. Although these dynamic effects areincoherent from QD to QD, these individual behaviors may encompass newtechnology unforeseen previously but applicable on an ensemble scale. Recently,charging devices have been fabricated showing the feasibility of controllingblinking on an ensemble film of QDs.ACKNOWLEDGMENTSThe authors would like to thank S.A. Empedocles and R.G. Neuhauser fortheir contributions in designing and implementing the single-quantum-dotmicroscope setup. Moreover, both were instrumental in developing andinterpreting key components of the previously published work in this review.The authors thank A1. L. Efros and E. Barkai for thoughtful discussions andCopyright 2004 by Marcel Dekker, Inc. All Rights Reserved.