Charge and energy transfer in the context of colloidal nanocrystals

Irgen-Gioro, Shawn; Yang, Muwen; Padgaonkar, Suyog; Chang, Woo Je; Zhang, Zhengyi; Jiang, Yishu; Weiss, Emily A.

doi:10.1063/5.0033263

Cited by 19 publications

(31 citation statements)

References 113 publications

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“…QDs with suitable surface ligands are expected to be useful for various applications related to electron and energy transfer , sensing, − photocatalysis, and tagging. Among these, designing and development of sensors that have been miniaturized to the nanoscale level can be used for detecting specific target analytes under proper physiological conditions and is an important direction in sensor development research. − While several molecule-based sensor systems are developed to detect specific target analytes, − only very recently, systems based on QDs are exploited for such a purpose.…”

Section: Introductionmentioning

confidence: 99%

Probing How Various Metal Ions Interact with the Surface of QDs: Implication of the Interaction Event on the Photophysics of QDs

Preeyanka

Sarkar

2021

Langmuir

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With an aim to understand the mechanism of interaction between quantum dots (QDs) and various metal ions, fluorescence response of less-toxic and water-soluble glutathione-capped Zn−Ag− In−S (GSH@ZAIS) QDs in the presence of different metal ions has been investigated at both ensemble and single-molecule level. Fourier transform infrared (FT-IR) spectroscopy has also been performed to obtain a molecular level understanding of the interaction event. The steady-state data reveal no significant change in QD emission for alkali and alkaline earth metal ions, while there is a decrease in fluorescence intensity for transition metal (TM) and some heavy transition metal (HTM) ions. Interestingly, a significant fluorescent enhancement (FE) (19−96%) of QDs is found for Cd 2+ ions. Time-resolved fluorescence studies reveal that all the three decay components of QDs decrease in the presence of first-row TM ions. However, in the case of Cd 2+ , the shorter component is found to increase while the longer one decreases. The analysis of data reveals that photoinduced electron transfer is responsible for fluorescence quenching of QDs in the presence of first-row TM ions and destruction/removal of trap/ defect states in the case of Cd 2+ causes the FE. In FT-IR experiments, a prominent peak at 670 cm −1 , corresponding to Cd−S stretching vibrations, indicates strong ground-state interactions between the −SH of GSH and Cd 2+ ions. Moreover, a decrease in the diffusion coefficient of QDs in the presence of Cd 2+ ions during fluorescence correlation spectroscopy (FCS) studies further substantiates the removal of GSH by Cd 2+ from the surface of QDs. The optical output of this study demonstrates that ZAIS can be used for fluorescence signaling of various metal ions and in particular selective detection of Cd 2+ . More importantly, these results also suggest that Cd 2+ can effectively be used for enhancing the fluorescence quantum yield of thiol-capped QDs such as GSH@ZAIS.

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Section: Introductionmentioning

confidence: 99%

Probing How Various Metal Ions Interact with the Surface of QDs: Implication of the Interaction Event on the Photophysics of QDs

Preeyanka

Sarkar

2021

Langmuir

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“…Prior work in nanocrystal photocatalysis has shown that long excited state lifetimes are desired because they indicate that photoinduced electron transfer (PET) processes can occur over extended periods of time before the excited states relax to the ground state. − A variety of nanocrystal architectures have been explored in an effort to increase the lifetime of charge-separated states. These include core shell architectures ,− as well as shape and composition-controlled nanocrystals such as nanorods, dot-in-rods, tetrapods, nanobarbells, and nanoplatelets. ,− These architectures combined with materials having appropriate band alignments have enabled charge carriers to be isolated to specific domains of the nanocrystals , and extended the lifetimes of photoexcited states into the microsecond regime .…”

Section: Introductionmentioning

confidence: 99%

Electron Transfer Going the Distance: Mn-Doped ZnSe as a Model Photocatalytic System

Watson

Asbury

2021

J. Phys. Chem. C

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Time-resolved photoluminescence and transient absorption spectroscopy are used to examine the influence that long excited state lifetimes of Mn-doped nanocrystals have on the mechanisms of photoinduced electron transfer (PET) in photocatalytic systems. Mn-doped ZnSe nanocrystals can undergo PET over their nearly millisecond excited state lifetime, which enables electron transfer to viologens in solution over large encounter distances in comparison to molecular length scales. The long excited state lifetimes also enable diffusion of the excited nanocrystals over hundreds of nanometers in solution, allowing them to react with molecular species at nanomolar concentrations. The ability to capture and sustain optical energy in spin-forbidden transitions among crystal field states of the Mn ions opens opportunities to explore the influence that long excited state lifetimes have on photocatalytic reaction mechanisms involving molecular species such as CO2 that can be difficult to concentrate or attach to nanocrystal surfaces.

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“…Optimization of these materials for photocatalysis will benefit from an understanding of the interfacial charge-transfer process, with structures consisting of semiconductor nanocrystals that have charge-accepting molecules on their surfaces providing a particularly convenient and rich model system to study. 5 The kinetics of charge transfer from nanocrystals to adsorbed molecules is commonly measured by using time-resolved spectroscopy, particularly time-resolved fluorescence decay and transient absorption. 5 However, the different hybrid nanostructures within an ensemble will, in general, have different charge-transfer rates, and ensemble measurements will result in a signal that is a weighted average of the distribution of these rates.…”

Section: ■ Introductionmentioning

confidence: 99%

“…5 The kinetics of charge transfer from nanocrystals to adsorbed molecules is commonly measured by using time-resolved spectroscopy, particularly time-resolved fluorescence decay and transient absorption. 5 However, the different hybrid nanostructures within an ensemble will, in general, have different charge-transfer rates, and ensemble measurements will result in a signal that is a weighted average of the distribution of these rates. 6 For quasi-spherical nanoparticles, the chargetransfer rate from a state in the particle to a molecule on the surface is largely independent of the position of the molecule, so the distribution of charge-transfer rates is determined primarily by the Poisson distribution of the number of molecules adsorbed on each nanocrystal; ensemble kinetics can thus be modeled to extract charge-transfer rates.…”

Section: ■ Introductionmentioning

confidence: 99%

Single-Molecule Measurements Spatially Probe States Involved in Electron Transfer from CdSe/CdS Core/Shell Nanorods

et al. 2021

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Semiconductor nanorods with charge-accepting molecules adsorbed on their surfaces serve as model systems for solar energy conversion. An electron photoexcited from the valence band of the nanorod to a high-energy state in the conduction band will relax and transfer to a state in the molecule, producing a long-lived charge-separated state that facilitates charge extraction and thereby enables photochemical reactions. Characterizing the dynamics of the charge-separation process and the electronic states involved is essential for a microscopic understanding of photocatalysis involving these materials, but this information is obscured in ensemble measurements due to the random placement of molecules on the nanorod surfaces. Here, we show that measurements on individual CdSe/CdS core/shell nanorods functionalized by single methyl viologen molecules provide information about the distribution of electron-transfer rates from confined states in the nanorods to states in the molecules. By comparing this transfer-rate distribution to the predictions of a tight-binding model, we find that charge transfer most likely involves hot electrons in an excited conduction-band state, rather than electrons that have fully thermalized to the conduction-band edge. The ability to extract hot electrons from semiconductor nanocrystals may help enable energy-efficient photocatalysis, and the single-particle charge-transfer method may serve as a widely applicable tool to probe the spatial distribution of electronic states in nanocrystals.

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Charge and energy transfer in the context of colloidal nanocrystals

Cited by 19 publications

References 113 publications

Probing How Various Metal Ions Interact with the Surface of QDs: Implication of the Interaction Event on the Photophysics of QDs

Probing How Various Metal Ions Interact with the Surface of QDs: Implication of the Interaction Event on the Photophysics of QDs

Electron Transfer Going the Distance: Mn-Doped ZnSe as a Model Photocatalytic System

Single-Molecule Measurements Spatially Probe States Involved in Electron Transfer from CdSe/CdS Core/Shell Nanorods

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