Continuous Distribution of Emission States from Single CdSe/ZnS Quantum Dots

Zhang, Kai; Chang, Huibin; Fu, Aihua; Alivisatos, A. Paul; Yang, Haw

doi:10.1021/nl060483q

Cited by 234 publications

(335 citation statements)

References 23 publications

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“…Multiple traps are likely to exist on the surface of a QD, each with a different efficiency of quenching QD luminescence. Hopping of carriers into and out of these states will lead to switching between several different levels of luminescence, with different corresponding recombination rates; such a distribution of emissive states has recently been inferred for single-dot luminescence data (40). Incorporating multiple surface traps into the diffusion-based models will require the consideration of additional system states, beyond the bright and dark states currently considered.…”

Section: [11]mentioning

confidence: 99%

Evidence for a diffusion-controlled mechanism for fluorescence blinking of colloidal quantum dots

Pelton

Smith²,

Scherer

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

159

219

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Fluorescence blinking in nanocrystal quantum dots is known to exhibit power-law dynamics, and several different mechanisms have been proposed to explain this behavior. We have extended the measurement of quantum-dot blinking by characterizing fluctuations in the fluorescence of single dots over time scales from microseconds to seconds. The power spectral density of these fluctuations indicates a change in the power-law statistics that occurs at a time scale of several milliseconds, providing an important constraint on possible mechanisms for the blinking. In particular, the observations are consistent with the predictions of models wherein blinking is controlled by diffusion of the energies of electron or hole trap states.fluorescence intermittency ͉ power spectrum ͉ nanocrystals H igh-quality, monodisperse semiconductor nanocrystals can be produced in large quantities by colloidal-synthesis techniques (1). These nanocrystals, known as quantum dots (QDs), can exhibit bright luminescence, whose wavelength is controlled by the size of the nanocrystals (2). This property makes colloidal QDs attractive candidates for several applications, including light-emitting diodes (3), solid-state lasers (4), and biological labeling (5, 6). Such applications, however, may be compromised by fluctuations in the QD luminescence. In particular, individual QDs emit light intermittently, switching irregularly between bright (''on'') and dark (''off'') states (7). Widespread interest in this blinking phenomenon was stimulated by the surprising observation that the durations of bright and dark periods follow power-law statistics (8, 9). Specifically, the blinking periods are described by probability densities of the formwith a value of between 0.4 and 1.0. The power-law behavior holds regardless of sample temperature (9), QD size or composition (10), nanoparticle shape (11), or excitation intensity (12). So far, though, experimental studies of QD blinking have been limited in their temporal resolution. A resolution of 200 s was achieved in one of the earliest measurements (8), and a small number of later experimental studies have included analysis of submicrosecond blinking dynamics (14,16,17,41). The remainder of the quantitative characterizations have been restricted to time scales of several milliseconds or longer. In this paper, we report measurements of fluctuations in QD fluorescence on time scales from microseconds to tens of seconds. We observe a change in the fluctuation dynamics for time scales less than several milliseconds.This observation is consistent with the predictions of a class of models where blinking is controlled by slow diffusion of the energies of electron or hole trap states. In these models, the fluorescence of a QD is quenched through the trapping of a carrier, which occurs when the energy of the trap state fulfills a resonance condition. The duration of the blinking periods is determined by the diffusion of the energy of the QD-trap system about this resonance condition. This diffusion-controlled mechanism ...

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Section: [11]mentioning

confidence: 99%

Evidence for a diffusion-controlled mechanism for fluorescence blinking of colloidal quantum dots

Pelton

Smith²,

Scherer

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

159

219

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“…Quantum dots 20 , single molecules 21 , silicon nanocrystals in a porous silicon matrix 22 and others 23 are well-known systems that show blinking. The validity of the two-state on/off model is intensely debated 24 , especially in the context of quantum-dot studies, where, for example, three states 25 and a continuous distribution of states 26 have been reported. In our case, the validity of the two-state model was underpinned by the photon distribution in 'on' and 'off' states based on the Gaussian distribution and expressed as…”

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confidence: 99%

Observation and control of blinking nitrogen-vacancy centres in discrete nanodiamonds

et al. 2010

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Nitrogen-vacancy colour centres in diamond can undergo strong, spin-sensitive optical transitions under ambient conditions, which makes them attractive for applications in quantum optics 1 , nanoscale magnetometry 2,3 and biolabelling 4 . Although nitrogen-vacancy centres have been observed in aggregated detonation nanodiamonds 5 and milled nanodiamonds 6 , they have not been observed in very small isolated nanodiamonds 7 . Here, we report the first direct observation of nitrogen-vacancy centres in discrete 5-nm nanodiamonds at room temperature, including evidence for intermittency in the luminescence (blinking) from the nanodiamonds. We also show that it is possible to control this blinking by modifying the surface of the nanodiamonds.Detonation nanodiamond is routinely produced on an industrial scale, and the raw material can be disintegrated into a stable 5-nm monodisperse colloid 8 . The combination of inert core and chemically reactive surface, which can host a variety of moieties, is appealing for chemists, biologists and material scientists 9,10 . Quantum magnetometry 2,3 is an example of an emerging technology that will directly benefit from the availability of nanocrystals with welldefined sizes in the 5-nm range, because the sensitivity to single spins is inversely proportional to the cube of the distance between the sensor (that is, the nitrogen-vacancy (NV) centre) and the spin being detected.Producing and detecting NV colour centres in isolated 5-nm detonation nanodiamond has been controversial, and there has been some scepticism regarding their stability as a useful emitter in a discrete crystal. For example, theoretical calculations of the crystal energy budget favour the location of nitrogen on the surface rather than in the core, which seems to explain the limited observation of NV centres in chemical vapour deposition and high-pressure high-temperature grains of less than 40 nm in size 11,12 , and favours the prediction that nanodiamonds smaller than 10 nm in size do not contain NV centres 7,13 . Although sub-10-nm nanodiamonds with NV centres have been produced using a top-down approach (milling luminescent high-pressure hightemperature microdiamonds into 7-nm particles 6,14 ), the question of NV stability in isolated detonation nanodiamonds persists.In aggregated detonation nanodiamonds (agglomerates and agglutinates 8 ), high-sensitivity, time-gated luminescence and electronic paramagnetic resonance spectroscopy have been used to extract a weak NV signal from a strong luminescence background 5 . The experiments highlight the eclipsing nature of the graphitic surface layers in nanodiamond aggregates-NV centres were simply not visible through the broadband luminescence from the surface and grain boundary material. To distinguish the NV spectral signature from the large grain boundary luminescence overhead, diamond synthesis yielding discrete sub-10-nm detonation nanodiamonds is vital. Here, we use a robust deaggregation and dispersion method, which diminishes the crystal-crystal interaction to...

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“…The synthesis of semiconductor quantum dots and their different applications as various electronic and optoelectronic devices including different kinds of sensors, devices are among the top research areas at present [1][2][3][4][5][6]. Recently, many techniques [1][2][3][4] like molecular beam epitaxy (MBE), radio frequency sputtering (RF), liquid phase epitaxy (LPE), quenching etc.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, many techniques [1][2][3][4] like molecular beam epitaxy (MBE), radio frequency sputtering (RF), liquid phase epitaxy (LPE), quenching etc. have been adopted to synthesize semiconductor quantum dots.…”

Section: Introductionmentioning

confidence: 99%

SnO2 quantum dots for nano light emitting devices

Nath¹,

Ganguly²,

Gope³

et al. 2017

Nanosystems: Phys. Chem. Math.

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We prepared SnO 2 quantum dots embedded in polyvinylpyrrolidone (PVP) matrix and report its operation as a Nano Light emitting device. The samples have been prepared via quenching technique where bulk ZnO powder is sintered at a very high temperature of 1000 • C and then quenched into ice cold polyvinylpyrrolidone solution. The specimen was then characterized using UV/VIS spectroscopy, X-ray diffraction study and high resolution transmission electron microscopy (HRTEM). These studies indicate the sizes of quantum dots to be within 9 nm. The prepared quantum dot samples have been evaluated as nano light emitting devices by exploring the variation of electroluminescence (light emission phenomenon) with supply voltage at room temperature.

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Continuous Distribution of Emission States from Single CdSe/ZnS Quantum Dots

Cited by 234 publications

References 23 publications

Evidence for a diffusion-controlled mechanism for fluorescence blinking of colloidal quantum dots

Evidence for a diffusion-controlled mechanism for fluorescence blinking of colloidal quantum dots

Observation and control of blinking nitrogen-vacancy centres in discrete nanodiamonds

SnO2 quantum dots for nano light emitting devices

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