Model‐Free Estimation of Energy‐Transfer Timescales in a Closely Emitting CdSe/ZnS Quantum Dot and Rhodamine 6G FRET Couple

Bharadwaj, Kiran; Koley, Somnath; Jana, Subhra; Ghosh, Subhadip

doi:10.1002/asia.201801272

Cited by 14 publications

(19 citation statements)

References 52 publications

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“…Tachiya's stochastic model has been used in several occasions where QD emission is quenched by PET and FRET processes. [68][69][70][71][72][73][74] By assuming the presence of trap sites at QD surface this model has nicely explained the nonexponential nature of QD's fluorescence lifetime profile. Undoubtedly the incorporation of this assumption during PET analysis of QD-NMA system will provide us an accurate estimation of PET kinetics.…”

Section: Resultsmentioning

confidence: 99%

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Study of Interfacial Charge Transfer from an Electron Rich Organic Molecule to CdTe Quantum Dot by using Stern‐Volmer and Stochastic Kinetic Models

et al. 2020

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Photoinduced electron transfer (PET) from N‐methylaniline (NMA) to a photoexcited CdTe quantum dot (QD*) is studied in toluene. The PET mechanism at low to moderate quencher (NMA) concentrations (<0.08 M) remains mostly collisional with some contributions from QD‐NMA complex formation. However, at high quencher concentrations (>0.10 M), QDs form larger numbers of static complexes with NMA molecules leading to a steep positive deviation in the steady‐state Stern–Volmer curves. An isothermal titration calorimetry (ITC) study confirms the formation of QD‐NMA complexes (K∼150 M−1) at high quencher concentrations. Fitting our experimental data using a stochastic kinetic model indicates that the number of NMA molecules attached per QD at highest NMA concentration (∼0.16 M) used in this study decreases from ∼0.76 to ∼0.47 with reducing the QD size from ∼5.2 nm to ∼3.2 nm. However, the PET rate increases with decreasing QD size, which is commensurate with the observation that the chemical driving force (ΔG) increases with decreasing the QD particle size. We have analyzed the PET kinetics mainly by using Stern‐Volmer fittings. However, in some cases Tachiya's stochastic kinetic model is used for stoichiometric analysis, which seems to be useful only at high quencher concentrations. The measured PET rate coefficients in all the cases are found to be at least an order of magnitude lower when compared to the diffusion‐controlled rate of the reaction medium.

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Section: Resultsmentioning

confidence: 99%

“…A survival probability function [S q (t,m)] was derived by normalizing Equation (1) by Equation (2), yielding: [49][50][73][74]…”

Section: Pet Analysis At High Nma Concentration Using Stochastic Kinementioning

confidence: 99%

Study of Interfacial Charge Transfer from an Electron Rich Organic Molecule to CdTe Quantum Dot by using Stern‐Volmer and Stochastic Kinetic Models

et al. 2020

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“…We can generate fitting equation [Eq. ] for an ensemble averaged decay profile of QD* of an emissive complex where one QD is attached to an average m number of DNT molecules considering all probable values of n (0 to ∞)

true I (t, m) = I_{0} \int_{n = 0}^{n = \infty} Θ ((), n) \exp [- (k_{0} + n k_{q}) t]

true I (t, m) = I_{0} \exp ([] - k_{0} t - m \{1 - \exp (- k_{q} t)\})

…”

Section: Resultsmentioning

confidence: 99%

“…This is because the steady state quenching is controlled by the formation of both, dark and emissive complexes, while the lifetime quenching is controlled by only the emissive complex formations. The steady‐state intensity quenching can be expressed by the following equations if the same stochastic kinetic model is used

true or, \frac{I}{I_{0}} = \frac{\{\sum_{n = 0}^{\infty} \sum_{n^{'} = 0}^{\infty} (() m^{n} e^{- m} / n!) (m_{t}^{n^{'}} e^{- m_{t}} / n^{'}!) / [1 + n k_{normalq} / k_{0} + n^{'} k_{q t} / k_{0}]\}}{\sum_{n^{'} = 0}^{\infty} (m_{t}^{n^{'}} e^{- m_{t}} / n^{'}!) / [1 + n^{'} k_{q t} / k_{0}]}

true or, \frac{I}{I_{0}} = {normale}^{- m} + \{\sum_{n > 0}^{\infty} \sum_{n^{'} = 0}^{\infty} (() m^{n} e^{- m} / n!) (m_{t}^{n^{'}} e^{- m_{t}} / n^{'}!) / [1 + n k_{normalq}\}

…”

Section: Resultsmentioning

confidence: 99%

“…We synthesized three different CdTe QDs varying in their sizes, with an intention of tuning the energy band gaps of the QD particles . We assumed a Poisson distribution of DNT molecules at QD surface (within surface capping layer) . A comprehensive fitting to the experimental data approves the acceptability of our stochastic fitting model, originally proposed by Tachiya in his seminal papers .…”

Section: Introductionmentioning

confidence: 99%

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Role of Emissive and Non‐Emissive Complex Formations in Photoinduced Electron Transfer Reaction of CdTe Quantum Dots

Bharadwaj

Choudhary

Hazra

et al. 2019

Chemistry An Asian Journal

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Bimolecular photoinduced electron transfer (PET) from excited state CdTe quantum dot (QD*) to an electron deficient molecule 2,4‐dinitrotoluene (DNT) is studied in toluene. We observed two types of QD‐DNT complex formations; (i) non‐emissive complex, in which DNT is embedded deep inside the surface polymer layer of QD and (ii) emissive complex, in which DNT molecules are attached to QDs but approach to the QD core is shielded by polymer layer. Because of its non‐emissive nature, the lifetime of QD is not affected by dark complex formation, though the steady‐state emission is greatly quenched. However, emissive complex formation causes both, lifetime and steady‐state emission quenching. In our fitting model, consideration of Poisson distribution of the attached quencher (DNT) molecules at QD surface enables a comprehensive fitting to our time resolved data. QD‐DNT complex formation was confirmed by an isothermal titration calorimetry (ITC) study. Fitting to the time resolved data using a stochastic kinetic model shows moderate increase (0.05 ns−1 to 0.072 ns−1) of intrinsic quenching rate with increasing the QD particle size (from ≈3.2 nm to ≈5.2 nm). Our fitting also reveals that the number of DNT molecules attached to a single QD increases from ≈0.1–0.2 to ≈1.2–1.7, as the DNT concentration is increased from ≈1 mm to 17.5 mm. Complex formation at higher quencher concentration assures that the observed PET kinetics is a thermodynamically controlled process where solvent diffusion has no role on it.

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Impact of FRET between Molecular Aggregates and Quantum Dots

Gayathri

Singh

Ghosh

2019

Chemistry An Asian Journal

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Energy transfer has been employed in third‐generation solar cells for the conversion of light into electrical energy. Long‐range nonradiative energy transfer from semiconductor quantum dots (QDs) to fluorophores has been demonstrated by using CdS QDs and thiophene−BODIPY (boron dipyrromethene, abbreviated as TG2). TG2 shows a broad photoluminescence (PL) spectrum, which varies with concentration. At very low concentrations, monomeric units are present; then, upon increasing the concentration, these monomers form a mixed (J‐/H‐)aggregated state. Energy transfer between the CdS QDs and TG2 was confirmed by separately investigating the interactions between CdS and the monomer of TG2 and between CdS and the aggregated states of TG2. Size‐dependent PL quenching confirmed that nonradiative Förster resonance energy transfer (FRET) from photoexcited CdS QDs to the J‐aggregate state of TG2 was the major energy‐relaxation channel, which occurred on the timescale of hundreds of fs. These results have broad applications in the field of light harvesting based on the assembly of molecular aggregates.

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Model‐Free Estimation of Energy‐Transfer Timescales in a Closely Emitting CdSe/ZnS Quantum Dot and Rhodamine 6G FRET Couple

Cited by 14 publications

References 52 publications

Study of Interfacial Charge Transfer from an Electron Rich Organic Molecule to CdTe Quantum Dot by using Stern‐Volmer and Stochastic Kinetic Models

Study of Interfacial Charge Transfer from an Electron Rich Organic Molecule to CdTe Quantum Dot by using Stern‐Volmer and Stochastic Kinetic Models

Role of Emissive and Non‐Emissive Complex Formations in Photoinduced Electron Transfer Reaction of CdTe Quantum Dots

Impact of FRET between Molecular Aggregates and Quantum Dots

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