Efficient Light Harvesting in Dye-Endcapped Conjugated Polymers Probed by Single Molecule Spectroscopy

Becker, K. W.; Lupton, John M.

doi:10.1021/ja0609405

Cited by 82 publications

(115 citation statements)

References 91 publications

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“…A study of peryleneendcapped poly(indenofl uorene) revealed that while on average the energy transfer along the backbone is ineffi cient, individual molecules may exhibit extremely effi cient energy transfer along the conjugated polymer chain and to the perylene dyes even without spectral overlap between the energy donor and acceptor [42]. Th is effi cient energy transfer in some of the molecules is likely to be due to a specifi c conformation of the main chain resulting from the presence of kinks on the otherwise rigid-rod chain.…”

Section: Review Articlementioning

confidence: 99%

Conformation and physics of polymer chains: a single-molecule perspective

Vácha

Habuchi

2010

NPG Asia Mater

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N anotechnology has been one of the driving forces of science and technology over the past 20 years. Scaling down the size of an object to nanometer dimensions can result in dramatic changes to its physical properties. With recent progress in the nanoscience and nanotechnology of polymeric materials, new methods are now required for the characterization of polymer structures and properties. Despite the great success of electron microscopy and scanning probe microscope techniques, there remains a need for a non-invasive method that could provide information not only on the structure but also on the physical phenomena occurring on the nanoscale level. One method that has recently emerged as an excellent tool for nanoscale characterization is single-molecule optical detection and spectroscopy. Single-molecule spectroscopy relies on the detection and measurement of the fl uorescence signal and spectra from single isolated molecules or polymer chains (Figure 1). Th ese can either be immobilized in a solid matrix or be diff using in a solution or melt. In all cases, the concentration of the emitting molecules must be suffi ciently low to ensure that the spatial separation between individual molecules is larger than the optical resolution of the setup, typically on the order of micrometers. As the fl uorescence signal from a molecule is strongly infl uenced by the nanoscale environment, measuring many molecules one by one provides the distribution of physical properties of the respective nano-environments. Moreover, monitoring a molecule over a period of time reveals dynamic changes in its environment. Th ese static and dynamic heterogeneities of nanoscale properties are averaged and hidden in the usual ensemble experiments. Th e strength of fl uorescence detection is in its sensitivity and low background level -emissions of just a few hundred photons per second can be readily detected. Th e technique also off ers remarkable dynamic range, from sub-nanosecond timescales to seconds and longer, and is non-invasive, making it possible to detect emissions from molecules buried deep in a sample.Single-molecule spectroscopy has evolved since the beginning of the 1990s from low-temperature, high-resolution optical spectroscopic

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Section: Review Articlementioning

confidence: 99%

Conformation and physics of polymer chains: a single-molecule perspective

Vácha

Habuchi

2010

NPG Asia Mater

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“…However, in a number of interesting cases energy transfer can be very efficient even in the absence of significant spectral overlap [1][2][3][4] . This scenario can arise in cases where the surrounding media appears to participate in the energy transfer process by retaining memory of the donor state long after the transfer has occurred.…”

Section: Introductionmentioning

confidence: 99%

Isotopic effect and temperature dependent intramolecular excitation energy transfer in a model donor–acceptor dyad

Singh

Bittner

2010

Phys. Chem. Chem. Phys.

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We consider here the non-adiabatic energy transfer dynamics for a model bi-chromophore system consisting of a perylenediimide unit linked to a ladder-type poly-(para-phenylene) oligomer. Starting from a semi-empirical parameterization of a model electron/phonon Hamiltonian, we compute the golden-rule rate for energy transfer from the LPPP5 donor to the PDI acceptor. Our results indicate that the non-adiabatic transfer is promoted by the out-of-plane wagging modes of the C-H bonds even though theses modes give little or no contribution to the Franck Condon factors in this system. We also predict a kinetic isotope effect of k (H) /k (D) = 1.7 − 2.5 depending upon the temperature.

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“…However, emission from the blue narrow chromophores will only be observed if intramolecular excitation energy transfer can be switched off by working at sufficiently low temperatures. 36 Once thermally activated intramolecular excitation energy transfer occurs, 37 emission will arise from the lower energy broad emitting bent chromophores. In this context it is also rewarding to note that we recently succeeded in mapping the progression of narrow PL transition lines of a poly(para-phenylene) directly to the single-chain Raman scattering spectra, 38 demonstrating directly that it is indeed the narrowest transitions that correspond to the chemically purest species.…”

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confidence: 99%

How Chromophore Shape Determines the Spectroscopy of Phenylene−Vinylenes: Origin of Spectral Broadening in the Absence of Aggregation

et al. 2008

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Single oligo(phenylene-vinylene) molecules constitute model systems of chromophores in disordered conjugated polymers and can elucidate how the actual conformation of an individual chromophore, rather than that of an overall polymer chain, controls its photophysics. Single oligomers and polymer chains display the same range of spectral properties. Even heptamers support π-electron conjugation across ∼80°curvature, as revealed by the polarization anisotropy in excitation and supported by quantum chemical calculations. As the chain becomes more deformed, the spectral linewidth at low temperatures, often interpreted as a sign of aggregation, increases up to 30-fold due to a reduction in photophysical stability of the molecule and an increase in random spectral fluctuations. The conclusions aid the interpretation of results from single-chain Stark spectroscopy in which large static dipoles were only observed in the case of narrow transition lines. These narrow transitions originate from extended chromophores in which the dipoles induced by backbone substituents do not cancel out. Chromophores in conjugated polymers are often thought of as individual linear transition dipoles, the sum of which make up the polymer's optical properties. Our results demonstrate that, at least for phenylene-vinylenes, it is the actual shape of the individual chromophore rather than the overall chromophoric arrangement and form of the polymer chain that dominates the spectroscopic properties.Molecular-level engineering in plastic electronics requires a precise understanding of how a particular physical or chemical structure impacts on the physical properties of the material. Disorder effects on the ensemble level can often mask the subtle interplay between function and structure. Large macromolecules such as conjugated polymers are particularly prone to energetic disorder, which gives rise to substantial spectral broadening and is generally attributed to a "particle in a box"-like picture of varying chromophore lengths. 1 Disorder effects have commonly been investigated in matrix isolated materials, such as polyenes, where subtle interplays between molecular shape and electronic structure have been identified. 2-5 However, matrix isolation on its own is not sufficient to overcome disorder but merely helps to screen intermolecular effects. The intrinsic molecular properties themselves are accessible with single-molecule spectroscopy. Although this technique helps to overcome the ensemble limitations, a single polymer chain can still contain many chromophores. [6][7][8][9][10][11][12] Energy transfer between these chromophores can mask the true photophysics of the individual spectroscopic unit. Although polarization-resolved spectroscopy has yielded detailed insight into the conformation of the polymer chain, 7,8,11,[13][14][15] very little is known about the shape of the indiVidual chromophore. Because a physical bend can potentially interrupt the π-electron conjugation, the chromophore is generally thought to be linearly extended in space...

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Efficient Light Harvesting in Dye-Endcapped Conjugated Polymers Probed by Single Molecule Spectroscopy

Cited by 82 publications

References 91 publications

Conformation and physics of polymer chains: a single-molecule perspective

Conformation and physics of polymer chains: a single-molecule perspective

Isotopic effect and temperature dependent intramolecular excitation energy transfer in a model donor–acceptor dyad

How Chromophore Shape Determines the Spectroscopy of Phenylene−Vinylenes: Origin of Spectral Broadening in the Absence of Aggregation

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