We report on the preparation and structural characterization of CdSe nanocrystals, which are covered by a multishell structure from CdS ZnS. By using newly developed successive ion layer adhesion reaction (SILAR) technique, we could gradually change shell composition to ZnS in radial direction. Because stepwise adjustment lattice parameters direction, resulting nanocrystals show high crystallinity almost perfectly spherical, as was investigated X-ray diffraction electron microscopy. Also,...

Heterosupramolecular structures from CdSe or CdSe/ZnS core/shell nanocrystals and a specially designed organic fluorophore (diazaperylene) have been prepared to investigate the electronic interactions at nanoscopic semiconductor surfaces. To determine average number of dye molecules per nanocrystal, we monitored size-dependent molar extinction coefficient particles. The NC/dye ratio is depending on particle size varies between 3 20 nanocrystal. We demonstrate that fluorescence completely...

In this review, we discuss investigations of electronic excitation energy transfer in conjugated organic materials at the bulk and single molecule level applications fluorescent phosphorescent light emitting devices. A brief overview common descriptions mechanisms is given followed by a discussion some basic photophysics including generation excited states their subsequent decay through various channels. particular, examples bimolecular state annihilation processes are presented. Energy...

Abstract Optical spectroscopy of a single impurity molecule provides the first truly local probe host–guest interactions in doped solids. In conventional optical high‐resolution experiments with many molecules only ensemble averages microscopic parameters can be obtained. single‐molecule regime, exquisite sensitivity an individual dopant to both environment and external perturbations has been exploited recent reveal wealth fascinating novel phenomena such as spectral diffusion crystals...

Type-II core/shell quantum dots are characterized by a staggered alignment of conduction and valence bands (see Figure), giving rise to broad tunability absorption emission wavelengths. Colloidal ZnTe/CdE (E = S, Se, Te) have been prepared with yields up 30 %. The synthesis route presented should be applicable other type-II dots.

Ultrafast ET with a characteristic time constant of approximately 70 fs between CdSe QDs (mean radii 1.4 nm) photoexcited in the lowest 1S electron state (lambda(exc) = 539 nm), and molecular acceptor MV(2+) adsorbed on QD surface was observed. The photophysics such system investigated by time-resolved transient absorbance spectroscopy UV-visible spectral region. Our studies for coupled as function excitation intensity at lambda(exc) 387 nm show that processes compete efficiently Auger...

A terrylenedicarboximide-anthraquinone dyad,

Organic near-infrared (NIR) photoblinking fluorophores are highly desirable for live-cell super-resolution imaging based on single-molecule localization microscopy (SMLM). Herein we introduce a novel small chromophore, PMIP, through the fusion of perylenecarboximide with 2,2-dimetheylpyrimidine. PMIP exhibits an emission maximum at 732 nm high fluorescence quantum yield 60% in wavelength range 700–1000 and excellent without any additives. With resorcinol-functionalized (PMIP-OH), NIR SMLM...

High-quality (uniform in size and morphology (σ = 3−5%), high crystallinity, QY (40−85%), sharp narrow absorption onsets PL peaks (fwhm 27−33 nm)) violet- to red-emitting ZnSe/CdSe core/shell nanocrystals have been prepared by the deposition of Cd/Se precursors (CdO elemental Se, respectively) into a diluted crude ZnSe reaction solution.

Electro- and photoluminescence spectra of the CdSe∕ZnS core-shell quantum dots (QDs) covered by various organic ligands incorporated into multilayered light-emitting diodes (LEDs) were recorded a confocal optical microscope. The QDs dispersed in hole transporting material, N,N’-Diphenyl-N,N’-bis(3-methylphenyl)-1,1’-biphenyl-4,4’-diamine (TPD), to investigate LED performance at different QD concentrations effect surface modifications on isolated QDs. No wavelength shift was observed...

In this letter, we describe the preparation of a versatile polymer ligand, which can be attached to CdSe/ZnS semiconductor nanocrystals via phase transfer reaction. The ligand is based on chain reactive esters, can, in principle, substituted by any compound containing amino-functionalities. polymer/nanocrystal complexes are characterized terms structure and photostability.

In the growing field of nanotechnology, there is an urgent need to sensitively determine toxicity nanoparticles since many technical and medical applications are based on controlled exposure particles, that is, as contrast agents or for drug delivery. Before in vivo implementation, vitro cell experiments required achieve a detailed knowledge biodegradation function nanoparticles' physical chemical properties. this study, we show micromotility animal cells monitored by electrical...

Exciton separation dynamics in the electron transfer system containing highly photostable CdSe/CdS core/shell nanocrystal quantum dots and adsorbed methylviologen was investigated by means of femtosecond absorption spectroscopy. The experiments revealed that extraction from photoexcited core is possible, rate ET reaction strongly depends on CdS shell thickness. A associated exponential decay constant β 0.33 Å−1 obtained reflecting electronic barrier effect shell. These findings show...

Internal conversion (IC) often is the dominating relaxation pathway in NIR emitters, lowering their fluorescence quantum yield. Here, we investigate dibenzoterrylene (DBT) by bulk and single molecule spectroscopy. With increasing solvent polarity, S1-S0 energy gap decreases leading to a decrease of yield an increase IC rate full accordance with law. Making use unexpectedly strong solvatochromism this aromatic hydrocarbon, validity law could also be demonstrated at level. The not only...

Single-dot microscopy has been employed to unravel the electronic interactions between nanoscopic surfaces and adsorbed molecules. It is illustrated that blinking effect of single nanocrystals changes in presence oxygen. The influence surrounding atmosphere as well illumination on fluorescence particle ensembles clearly visible Figure.

We investigate the origin of Breit-Wigner-Fano line in Raman spectra individual single-walled carbon nanotubes and their bundles. Using confocal microscopy atomic-force we found that intensity increases strongly with bundle thickness. confirmed this result by investigations partially decomposed bundles, which were additionally investigated transmission electron microscopy. Our random-phase approximation based theory, identifies as an excited band plasmon-phonon modes, is fully consistent...

We have investigated electronic excitation transfer in individual molecular dimers by time and spectrally resolved confocal fluorescence microscopy. The single molecule measurements allow for directly probing the distribution of coupling strengths due to static disorder polymer host. find where is delocalized (superradiant emission) while others emission originates from a localized state. Transitions between states as observed given dimer are attributed structural fluctuations guest-host system.

Unidirectional electronic excitation energy transfer from a photoexcited donor chromophore to ground state acceptor chromophore---both linked by rigid bridge---has been investigated low temperature high-resolution single molecule spectroscopy. Our approach allows for accurately accessing static disorder in the and transitions calculate spectral overlap each couple. By plotting experimentally determined rates against overlap, we can distinguish quantify F\"orster- non-F\"orster-type...

Electronic excitation energy transfer (EET) rates in rylene diimide dyads are calculated using second-order approximate coupled-cluster theory and time-dependent density functional theory. We investigate the dependence of EET on interchromophoric distance relative orientation show that Forster works quantitatively only for donor-acceptor separations larger than roughly 5 nm. For smaller distances over- or underestimated by depending respective transition dipole moments chromophores. In...

We report on the successful encapsulation of hydrophobic substrates into shell poly(butadiene)-b-poly(ethylene oxide) vesicles in water and straightforward characterization methods. The fluorescent dye Nile Red was embedded unilamellar PB130-b-PEO66 prepared via different methods leading to average hydrodynamic radii distributions but a common thickness ∼16 nm as determined by transmission electron microscopy (TEM). combination cryogenic TEM fluorescence studies shows that self-assembled...

Dibenzo[hi,st]ovalene (DBOV), as a new nanographene, has demonstrated promising optical properties, such red emission with high fluorescence quantum yield of 79% and stimulated emission, well thermal stability photostability, which indicated its promise light-emitting gain material. However, the previous synthetic routes required at least 12 steps. This obstructed access to different derivatives, e.g., obtain crystals suitable for X-ray diffraction analysis tune optoelectronic properties....

The differences in the fluorescence behavior of a polyphenylene dendrimer with eight peryleneimides chromophores (1) and single hexaphenylperyleneimide chromophore have been investigated at single-molecule level through combination ultrasensitive detection microscopy.

The photooxidation of single dye molecules (see scheme) can be followed by confocal fluorescence microscopy. self-sensitized reaction with singlet oxygen leads to a suite products, which may differentiated spectrally. Tentative structures for certain photoproducts have been obtained from quantum-chemical calculations.

The fluorescence of individual pairs perylenemonoimide chromophores coupled via a short rigid linker is investigated. Photon antibunching reported, indicating collective effects in the fluorescence, which are further substantiated by observation triplet off times and lifetime shortening. experimental findings analyzed terms singlet-singlet singlet-triplet annihilation based on Förster type energy transfer. results reported here demonstrate that statistical properties emission light isolated...

Something to fret about: Luminescent semiconductor nanocrystals are covered with polymeric ligands which form many bonds the nanocrystal (NC) and increase their solubility. The decorated an organic dye molecule (see picture) so that electronic interaction in individual nanocrystal–dye complexes can be investigated by fluorescence resonance energy transfer (FRET) experiments. results show factors influence FRET results.