Energy and Charge Transfer in Nanoscale Hybrid Materials

Basché, Thomas; Bottin, Anne; Li, Chen; Müllen, Kläus; Kim, Jeong-Hee; Sohn, Byeong‐Hyeok; Prabhakaran, Prém; Lee, Kwang-Sup

doi:10.1002/marc.201400738

Cited by 19 publications

(14 citation statements)

References 104 publications

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“…Block copolymers (BCPs) have gained a lot of attention due to their ability to self‐assemble into nanostructures, which may serve as templates for nanolithography, organic photovoltaics, and nanoporous films . Imperative for use in these applications is a defect‐free, controllable structure with the feature size in the nanometer range .…”

Section: Introductionmentioning

confidence: 99%

In Situ Tracking of Composition and Morphology of a Diblock Copolymer Film with GISAXS during Exchange of Solvent Vapors at Elevated Temperatures

Berezkin

Jung

Posselt

et al. 2018

Adv Funct Materials

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Solvothermal vapor annealing at elevated temperature is applied to a thin film from a cylinder-forming polystyrene-block-poly(dimethyl siloxane) (PS-b-PDMS) diblock copolymer. At this, the film is swollen in the vapor of n-heptane (highly selective for PDMS). This vapor is stepwise replaced by the vapor of toluene (weakly selective for PS). The morphologies are investigated using in situ, real-time grazing-incidence small-angle X-ray scattering (GISAXS). The initial cylindrical morphology is transformed into, among others, the lamellar one. This novel type of experiments allows probing a trajectory in the state diagram of the PS-b-PDMS/n-heptane/toluene mixture. To corroborate the morphologies, they are generated by molecular simulations, and the 2D GISAXS maps are calculated using the distorted-wave Born approximation. To relate the morphologies to the solvent distribution in the two types of nanodomains, the latter is estimated from the intensities of the Bragg reflections in the 2D GISAXS maps along with the swelling ratio of the film. Comparison with the results from a similar experiment carried out at room temperature results in the same sequence of morphologies; however, at elevated temperature, more well-ordered structures are obtained. This new approach proves to be efficient to achieve a block copolymer thin film having a desired morphology and orientation.

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Section: Introductionmentioning

confidence: 99%

In Situ Tracking of Composition and Morphology of a Diblock Copolymer Film with GISAXS during Exchange of Solvent Vapors at Elevated Temperatures

Berezkin

Jung

Posselt

et al. 2018

Adv Funct Materials

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“…For multiexciton extraction following CM, the removal of charges must come after the hot exciton fission but before multiexciton recombination, and in some of the materials seen to date this can be extended into the few ns regime, which is a less difficult prospect than for hot carrier extraction. Whilst we have not covered the extraction or transfer of charge to adjacent acceptors in this review, it is a very active field of research and there are many reviews [ 132 ], and recent research papers [ 133 ] on this subject. Of course, the efficient transport of the carriers through the QD or QD/host matrix film once they have been carefully harvested is an equally, if not arguably a more, important subject which also continues to be investigated [ 134 , 135 , 136 , 137 ].…”

Section: Discussionmentioning

confidence: 99%

Carrier Multiplication Mechanisms and Competing Processes in Colloidal Semiconductor Nanostructures

Kershaw

Rogach

2017

Materials

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Quantum confined semiconductor nanoparticles, such as colloidal quantum dots, nanorods and nanoplatelets have broad extended absorption spectra at energies above their bandgaps. This means that they can absorb light at high photon energies leading to the formation of hot excitons with finite excited state lifetimes. During their existence, the hot electron and hole that comprise the exciton may start to cool as they relax to the band edge by phonon mediated or Auger cooling processes or a combination of these. Alongside these cooling processes, there is the possibility that the hot exciton may split into two or more lower energy excitons in what is termed carrier multiplication (CM). The fission of the hot exciton to form lower energy multiexcitons is in direct competition with the cooling processes, with the timescales for multiplication and cooling often overlapping strongly in many materials. Once CM has been achieved, the next challenge is to preserve the multiexcitons long enough to make use of the bonus carriers in the face of another competing process, non-radiative Auger recombination. However, it has been found that Auger recombination and the several possible cooling processes can be manipulated and usefully suppressed or retarded by engineering the nanoparticle shape, size or composition and by the use of heterostructures, along with different choices of surface treatments. This review surveys some of the work that has led to an understanding of the rich carrier dynamics in semiconductor nanoparticles, and that has started to guide materials researchers to nanostructures that can tilt the balance in favour of efficient CM with sustained multiexciton lifetimes.

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“…Typically, the above PL quenching for QD counterpart being observed in numerous QD-dye nanocomposites is commonly interpreted as being due to the photoinduced charge transfer (CT) (23,(119)(120)(121)(122)(123)(124) and/or to the dipole-dipole resonant energy transfer of Foerster type (FRET) QD→dye (18,19,22,45,68,72,74,92,100,101,112,(125)(126)(127)(128)(129)(130)(131). Usually in the FRET case, the direct verification of the energy transfer process as a real reason of PL quenching is the comparison of the experimental values of FRET efficiencies via the donor (QD) PL quenching and the sensitization of the acceptor (porphyrin) fluorescence.…”

Section: Spectral-kinetic Manifestation Of Qd-porphyrin Nanoassembliementioning

confidence: 99%

Surface Photochemistry of Quantum Dot-Porphyrin Nanoassemblies for Singlet Oxygen Generation

Zenkevich

Borczyskowski

2015

ACS Symposium Series

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This Chapter covers the basics of nanotechnology, focusing on hybrid organic-inorganic nanoassemblies based on self-assembly principles. Here, we are willing to discuss the formation principles and mechanisms of excitation energy relaxation being studied for nanoassemblies based on core/shell CdSe(ZnS) colloidal semiconductor quantum dots (QD) exhibiting size-dependent photophysical properties and surfacely activated by pyridyl-substituted porphyrins, H 2 P (bulk solutions) in liquid solvents at 295 K (steady-state, picosecond time-resolved luminescence spectroscopy and single molecule spectroscopy). Upon formation of QD-H 2 P nanoassemblies the QD photoluminescence (PL) is quenched as can be detected both via single particle detection and ensemble experiments in solution. PL quenching has been quantitatively assigned to FRET QD→ H 2 P (10-14%) and Non-FRET (86-90%) processes. Using near-IR photoluminescence measurements, we performed a quantitative comparative studying the efficiencies of the singlet oxygen generation by alone QDs and "QD-H 2 P" nanoassemblies upon variation of the laser pulse energy. It was found that for QD-H 2 P nanoassemblies the experimental efficiencies of singlet oxygen generation are essentially higher with respect to those obtained for alone QDs. In the case of QD-H 2 P nanoassemblies, it was proven also that the non-linear dependence of the efficiency of singlet oxygen generation on the laser pulse energy is caused by non-radiative intraband Auger processes, realized in QD counterpart. It has been found that values of FRET QD→ H 2 P efficiencies obtained via direct measurements of IR-emission of singlet oxygen at low laser excitation (Φ IR = 0.12 ± 0.03) are in a good agreement with the corresponding FRET efficiencies found from the direct sensitization data for porphyrin fluorescence (Φ FRET = 0.14 ± 0.02) in nanoassemblies. Such quantitative analysis was done for the first time and shows that namely FRET process QD→H 2 P is a main reason of singlet oxygen generation by QD→H 2 P nanoassemblies.

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Energy and Charge Transfer in Nanoscale Hybrid Materials

Cited by 19 publications

References 104 publications

In Situ Tracking of Composition and Morphology of a Diblock Copolymer Film with GISAXS during Exchange of Solvent Vapors at Elevated Temperatures

In Situ Tracking of Composition and Morphology of a Diblock Copolymer Film with GISAXS during Exchange of Solvent Vapors at Elevated Temperatures

Carrier Multiplication Mechanisms and Competing Processes in Colloidal Semiconductor Nanostructures

Surface Photochemistry of Quantum Dot-Porphyrin Nanoassemblies for Singlet Oxygen Generation

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