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Electron transfer-based single molecule fluorescence as a probe for nano-environment dynamics.

Chen R, Wu R, Zhang G, Gao Y, Xiao L, Jia S - Sensors (Basel) (2014)

Bottom Line: Electron transfer (ET) is one of the most important elementary processes that takes place in fundamental aspects of biology, chemistry, and physics.We review some applications, including the dynamics of glass-forming systems, surface binding events, interfacial ET on semiconductors, and the external field-induced dynamics of polymers.All these examples show that the ET-induced changes of fluorescence trajectory and lifetime of single molecules can be used to sensitively probe the surrounding nano-environments.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China. chenry421@163.com.

ABSTRACT
Electron transfer (ET) is one of the most important elementary processes that takes place in fundamental aspects of biology, chemistry, and physics. In this review, we discuss recent research on single molecule probes based on ET. We review some applications, including the dynamics of glass-forming systems, surface binding events, interfacial ET on semiconductors, and the external field-induced dynamics of polymers. All these examples show that the ET-induced changes of fluorescence trajectory and lifetime of single molecules can be used to sensitively probe the surrounding nano-environments.

No MeSH data available.


(a) Scheme for interfacial ET; (b) and (c) Energy diagram for ET from perylene molecule to ITO; (d) Histogram and single-exponential fit for on and off duration times. Reprinted with permission from Ref. [62]. Copyright (2003) American Chemical Society.
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f8-sensors-14-02449: (a) Scheme for interfacial ET; (b) and (c) Energy diagram for ET from perylene molecule to ITO; (d) Histogram and single-exponential fit for on and off duration times. Reprinted with permission from Ref. [62]. Copyright (2003) American Chemical Society.

Mentions: Analysis of on/off duration time is another useful tool to investigate ET between single molecules and semiconductors. As said, ET is usually a nonradiative pathway for the excited chromophore which would efficiently quench the fluorescence. Mechanism of ET can be reflected from the direct change of the fluorescence trajectories. Holman et al. investigated the interfacial ET and back ET rates in prototypical chromophore-bridge-ITO systems [62], as shown in Figure 8a. They attributed the “blinks” found in the fluorescence trajectories to discrete ET events. The mechanism of blinking is shown in Figures 8b,c: an optically excited single perylene molecule near the ITO electrode can either relax radiatively from its excited state (P*) to the ground state (P) or undergo ET from the lowest unoccupied molecular orbital (LUMO) to the conduction band of ITO. When a single molecule loses the excited electron into the ITO semiconductor, the fluorescence stops and remains “off” until the electron returns back from the ITO conduction band to the molecule and back “on”. They proposed that each blinking off or on represents a single ET event. By analyzing the histogrammed “on” and “off” duration times (occurrences versus duration time), the ET rates can be determined by fitting the histogram with single-exponential curve, as shown in Figure 8d. The backward ET rate is the inverse of the “off” duration time:(2)1τoff=kbetwhile the forward ET rate depends on the “on” duration and the excitation rate:(3)1τon=kexcket(ket+kfluor+kisc+kic)where kexc is excitation rate, ket and kbet represent the forward ET rate and backward ET rate, kfluo means the emission rate of fluorescence, kisc means rate of intersystem crossing to the triplet state and kic is the rate of internal conversion decay.


Electron transfer-based single molecule fluorescence as a probe for nano-environment dynamics.

Chen R, Wu R, Zhang G, Gao Y, Xiao L, Jia S - Sensors (Basel) (2014)

(a) Scheme for interfacial ET; (b) and (c) Energy diagram for ET from perylene molecule to ITO; (d) Histogram and single-exponential fit for on and off duration times. Reprinted with permission from Ref. [62]. Copyright (2003) American Chemical Society.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3958234&req=5

f8-sensors-14-02449: (a) Scheme for interfacial ET; (b) and (c) Energy diagram for ET from perylene molecule to ITO; (d) Histogram and single-exponential fit for on and off duration times. Reprinted with permission from Ref. [62]. Copyright (2003) American Chemical Society.
Mentions: Analysis of on/off duration time is another useful tool to investigate ET between single molecules and semiconductors. As said, ET is usually a nonradiative pathway for the excited chromophore which would efficiently quench the fluorescence. Mechanism of ET can be reflected from the direct change of the fluorescence trajectories. Holman et al. investigated the interfacial ET and back ET rates in prototypical chromophore-bridge-ITO systems [62], as shown in Figure 8a. They attributed the “blinks” found in the fluorescence trajectories to discrete ET events. The mechanism of blinking is shown in Figures 8b,c: an optically excited single perylene molecule near the ITO electrode can either relax radiatively from its excited state (P*) to the ground state (P) or undergo ET from the lowest unoccupied molecular orbital (LUMO) to the conduction band of ITO. When a single molecule loses the excited electron into the ITO semiconductor, the fluorescence stops and remains “off” until the electron returns back from the ITO conduction band to the molecule and back “on”. They proposed that each blinking off or on represents a single ET event. By analyzing the histogrammed “on” and “off” duration times (occurrences versus duration time), the ET rates can be determined by fitting the histogram with single-exponential curve, as shown in Figure 8d. The backward ET rate is the inverse of the “off” duration time:(2)1τoff=kbetwhile the forward ET rate depends on the “on” duration and the excitation rate:(3)1τon=kexcket(ket+kfluor+kisc+kic)where kexc is excitation rate, ket and kbet represent the forward ET rate and backward ET rate, kfluo means the emission rate of fluorescence, kisc means rate of intersystem crossing to the triplet state and kic is the rate of internal conversion decay.

Bottom Line: Electron transfer (ET) is one of the most important elementary processes that takes place in fundamental aspects of biology, chemistry, and physics.We review some applications, including the dynamics of glass-forming systems, surface binding events, interfacial ET on semiconductors, and the external field-induced dynamics of polymers.All these examples show that the ET-induced changes of fluorescence trajectory and lifetime of single molecules can be used to sensitively probe the surrounding nano-environments.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China. chenry421@163.com.

ABSTRACT
Electron transfer (ET) is one of the most important elementary processes that takes place in fundamental aspects of biology, chemistry, and physics. In this review, we discuss recent research on single molecule probes based on ET. We review some applications, including the dynamics of glass-forming systems, surface binding events, interfacial ET on semiconductors, and the external field-induced dynamics of polymers. All these examples show that the ET-induced changes of fluorescence trajectory and lifetime of single molecules can be used to sensitively probe the surrounding nano-environments.

No MeSH data available.