Two types of luminescence blinking revealed by spectroelectrochemistry of single quantum dots

Galland, Christophe; Ghosh, Yagnaseni; Steinbrück, Andrea; Sýkora, Milan; Hollingsworth, Jennifer A.; Klimov, Victor I.; Htoon, Han

doi:10.1038/nature10569

Cited by 684 publications

(1,135 citation statements)

References 34 publications

(37 reference statements)

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“…This suggests that for the untreated samples not every absorbed photon results in an electron at the CBM, i.e., some of the hot electrons created immediately after absorption are cooling directly into a trap state, and thus reducing the CBM state filling responsible for the bleach signal. The surface trapping of hot carriers in CQDs has been discussed at length by Kambhampati34 and is also used to explain one form of PL intermittency, also known as “blinking.”8, 35 This additional cooling pathway for hot electrons in the CQDs before passivation also explains the decreased rise time of the bleach signal, as the population of hot electrons is depleted more rapidly.…”

Section: Resultsmentioning

confidence: 98%

Ultrafast Charge Dynamics in Trap‐Free and Surface‐Trapping Colloidal Quantum Dots

et al. 2015

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Ultrafast transient absorption spectroscopy is used to study subnanosecond charge dynamics in CdTe colloidal quantum dots. After treatment with chloride ions, these can become free of surface traps that produce nonradiative recombination. A comparison between these dots and the same dots before treatment enables new insights into the effect of surface trapping on ultrafast charge dynamics. The surface traps typically increase the rate of electron cooling by 70% and introduce a recombination pathway that depopulates the conduction band minimum of single excitons on a subnanosecond timescale, regardless of whether the sample is stirred or flowed. It is also shown that surface trapping significantly reduces the peak bleach obtained for a particular pump fluence, which has important implications for the interpretation of transient absorption data, including the estimation of absorption cross‐sections and multiple exciton generation yields.

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Section: Resultsmentioning

confidence: 98%

Ultrafast Charge Dynamics in Trap‐Free and Surface‐Trapping Colloidal Quantum Dots

et al. 2015

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“…Further increases in d′ might also be attained using novel coatings that optimally target nanoparticles, reduce blinking, or interact strongly with the qdot core to enhance voltage sensitivity. [42][43][44] Optical measurements of voltage also would also benefit substantially from use of microscopy modalities with enhanced sectioning capabilities 39,45 or collection efficiencies. 46 A growing number of biocompatible surface chemistries target qdots to the exterior of cells.…”

Section: Resultsmentioning

confidence: 99%

Optical Strategies for Sensing Neuronal Voltage Using Quantum Dots and Other Semiconductor Nanocrystals

Marshall

Schnitzer

2013

ACS Nano

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Biophysicists have long sought optical methods capable of reporting the electrophysiological dynamics of large-scale neural networks with millisecond-scale temporal resolution. Existing fluorescent sensors of cell membrane voltage can report action potentials in individual cultured neurons, but limitations in brightness and dynamic range of both synthetic organic and genetically encoded voltage sensors have prevented concurrent monitoring of spiking activity across large populations of individual neurons. Here we propose a novel, inorganic class of fluorescent voltage sensors: semiconductor nanoparticles, such as ultrabright quantum dots (qdots). Our calculations revealed that transmembrane electric fields characteristic of neuronal spiking (~10 mV/nm) modulate a qdot's electronic structure and can induce ~5% changes in its fluorescence intensity and ~1 nm shifts in its emission wavelength, depending on the qdot's size, composition, and dielectric environment. Moreover, tailored qdot sensors composed of two different materials can exhibit substantial (~30%) changes in fluorescence intensity during neuronal spiking. Using signal detection theory, we show that conventional qdots should be capable of reporting voltage dynamics with millisecond precision across several tens or more individual neurons over a range of optical and neurophysiological conditions. These results unveil promising avenues for imaging spiking dynamics in neural networks and merit in-depth experimental investigation. Toward addressing these challenges, we studied whether tools from nanotechnology, specifically, bright, multifunctional semiconductor quantum dots (qdots), 22,23 might be useful for imaging neuronal membrane potentials. Qdots are known to possess voltagesensitive optical properties, including a red-shifting of the qdot's fluorescence emission peak, spectral broadening, and a decrease in the intensity of fluorescence emission ( Figure 1C,D). [24][25][26][27] Qdots also are highly resistant to photobleaching and exhibit large quantum yields and absorption cross sections for one-(σ 1 ) and two-photon (σ 2 ) excitation. For example, CdSe qdots with radius R ~ 3 nm exhibit cross sections of σ 1 > 1 nm 2 and σ 2 > 3 × 10 4 GM, as compared to σ 1 ~ 10 −2 nm 2 and σ 2 ~ 3 × 10 2 GM for green fluorescent protein. 28,29 Marshall and Schnitzer Page 2 ACS Nano. Author manuscript; available in PMC 2017 December 15. Graphical Abstract HHMI Author Manuscript HHMI Author Manuscript HHMI Author ManuscriptTo evaluate the spike detection capabilities of qdot indicators quantitatively, we applied a theoretical approach that incorporates the physical, biophysical, and statistical components of the problem. We calculated the effect of applied electric fields on the qdot's electronic structure and examined how this modulates a qdot's fluorescence intensity and emission spectra. We also studied nonspherical, nonhomogenous qdots, which we refer to more generally as semiconductor nanocrystals, and found that these nanoparticles can demonstrate muc...

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“…Curiously, almost every nanoscale fluorescent object is known to exhibit fluorescence blinking. For semiconductor quantum dots and solubilised chromophores, the dominant underlying molecular mechanism was shown to involve ionisation, in the former due to a photoassisted Auger process [27,28] and in the latter, longliving, dark radical states were populated via triplet states [29]. For LHC2, containing 54 chromophores, one might similarly expect radical states to be responsible for fluorescence blinking.…”

Section: Photoactive Control Over the Intrinsic Protein Disordermentioning

confidence: 99%

Design principles of natural light-harvesting as revealed by single molecule spectroscopy

Krüger

Grondelle

2016

Physica B: Condensed Matter

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Biology offers a boundless source of adaptation, innovation, and inspiration. A wide range of photosynthetic organisms exist that are capable of harvesting solar light in an exceptionally efficient way, using abundant and low-cost materials. These natural light-harvesting complexes consist of proteins that strongly bind a high density of chromophores to capture solar photons and rapidly transfer the excitation energy to the photochemical reaction centre. The amount of harvested light is also delicately tuned to the level of solar radiation to maintain a constant energy throughput at the reaction centre and avoid the accumulation of the products of charge separation. In this Review, recent developments in the understanding of light harvesting by plants will be discussed, based on results obtained from single molecule spectroscopy studies. Three design principles of the main light-harvesting antenna of plants will be highlighted: (a) fine, photoactive control over the intrinsic protein disorder to efficiently use intrinsically available thermal energy dissipation mechanisms; (b) the design of the protein microenvironment of a low-energy chromophore dimer to control the amount of shade absorption; (c) the design of the exciton manifold to ensure efficient funneling of the harvested light to the terminal emitter cluster.

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Two types of luminescence blinking revealed by spectroelectrochemistry of single quantum dots

Cited by 684 publications

References 34 publications

Ultrafast Charge Dynamics in Trap‐Free and Surface‐Trapping Colloidal Quantum Dots

Ultrafast Charge Dynamics in Trap‐Free and Surface‐Trapping Colloidal Quantum Dots

Optical Strategies for Sensing Neuronal Voltage Using Quantum Dots and Other Semiconductor Nanocrystals

Design principles of natural light-harvesting as revealed by single molecule spectroscopy

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