Proton Transfer and Photoluminescence Intermittency of Single Emitters in Dyed Crystals

Abstract

The role of proton transfer in the photoluminescence intermittency (PI) of single molecules of violamine R (VR) overgrown in potassium acid phthalate (KAP) crystals is evaluated in comparisons of protonated (KAP) and deuterated (DKAP) mixed crystals between 23 and 60 °C. The PI is analyzed by the construction of cumulative distribution functions that are statistically compared. We find that the on- and off-interval duration distributions change with isotopic substitution consistent with proton transfer contributing to the PI of VR. The on- and off-interval duration distributions have distinct temperature dependencies consistent with different mechanisms for dark state production and decay. Additional evidence for proton-transfer is provided by distributions of single molecule emission-energy maxima that reflect emission from protonated and deprotonated VR. A mechanism for the PI of KAP is presented, where the dark state is assigned to formation of the colorless, leuco form of VR, formed by proton transfer from VR to the KAP lattice, and decay of the dark state involves ring-opening promoted by proton transfer from KAP to VR. The distributed kinetics for dark-state production and decay are modeled using a log-normal distribution for the PI data in preference to a power-law previously assumed. A discussion of the log-normal distribution with regards to PI and proton transfer is presented.

Tunneling in the Delayed Luminescence of Colloidal CdSe, Cu+-Doped CdSe, and CuInS2 Semiconductor Nanocrystals and Relationship to Blinking

“…Although power-law behavior is often reported in blinking studies 8,9,26 and has been reported for delayed luminescence as well, 1,4,5 deviations from power-law have been emphasized in recent blinking literature. [27][28][29] Deviations from power-law kinetics are clearly evident in the delayed luminescence kinetics reported here. For both delayed luminescence (this study) and some blinking data, [27][28][29] log-normal distributions reproduce the dynamics better than power-law distributions.…”

“…[27][28][29] Deviations from power-law kinetics are clearly evident in the delayed luminescence kinetics reported here. For both delayed luminescence (this study) and some blinking data, [27][28][29] log-normal distributions reproduce the dynamics better than power-law distributions. Even more compelling is the observation in blinking measurements on CdSe NCs that the "off" statistics (which reflect detrapping dynamics analogous to the delayed luminescence decay dynamics described here) are also temperature independent, 8,9,26,30,31 implying a tunneling process for detrapping.…”

Photoluminescence Intermittency from Single Quantum Dots to Organic Molecules: Emerging Themes

“…In this study, the PI exhibited by VR in KAP and DKAP was analyzed using new statistical methods [ 56 ] to determine if the underling probability distribution functions describing the on - and off -durations were modified with isotopic substitution. This analysis involved the statistical comparison of complimentary cumulative distribution functions (CDFs) derived from the PI data obtained for VR in KAP and DKAP at three temperatures (23 °C, 45 °C, and 60 °C) [ 116 ]. The results of this analysis are presented in Figure 10 .…”

“… Complimentary CDF’s of on -( a ) and off -( b ) event durations for VR in KAP and DKAP at all three temperatures [ 116 ]. Dashed lines are DKAP and solid lines are KAP at room temperature (blue), 45 °C (green), and 60 °C (red).…”

Recent Advances in Understanding Delayed Photoluminescence in Colloidal Semiconductor Nanocrystals

“…periods at the single particle level under continuous excitation. This phenomenon is not specific to nanocrystals, and has also been observed in molecular [11] and biological systems. [12] As a result, PL intermittency is characterized by dark 'off' states and bright 'on' states.…”