Organic/Inorganic Semiconductor Hybrid Nanoparticles from Controlled Polymerization

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CdSe/CdSConjugated Polymer Core–Shell Hybrid Nanoparticles by a Grafting-From Approach

Hybrid particles consisting of II–VI semiconductor quantum dots and conjugated polymers are increasingly relevant, but access is limited by the usual step-growth nature of polymer formation. We report on a grafting-from approach by controlled Pd­(II)-mediated polymerization to yield CdSe/CdS nanocrystals with a defined number of polyfluorene chains grown from their surface, as concluded from MALDI-TOF analysis and quantitative end-capping. Further studies underline the importance of matching the monomers’ and the surface-bound initiators’ reactivity

Self-assembled monolayer field-effect transistors based on oligo-9,9′-dioctylfluorene phosphonic acids

The use of functional oligomers of π-conjugated oligofluorenes led to a region-selective assembly of amorphous monolayers which exhibit robust lateral charge transport pathways in selfassembled monolayer field-effect transistors over long distances and even in mixed monolayers of semiconducting and insulating molecules. This oligomer concept might stimulate a new molecular design of self-assembling semiconducting materials.publishe

Nonlinear Photoluminescence Spectrum of Single Gold Nanostructures

We investigate the multiphoton photoluminescence characteristics of gold nanoantennas fabricated from single crystals and polycrystalline films. By exciting these nanostructures with ultrashort pulses tunable in the near-infrared range, we observe distinct features in the broadband photoluminescence spectrum. By comparing antennas of different crystallinity and shape, we demonstrate that the nanoscopic geometry of plasmonic devices determines the shape of the emission spectra. Our findings rule out the contribution of the gold band structure in shaping the photoluminescence

Coupling of Excitons and Discrete Acoustic Phonons in Vibrationally Isolated Quantum Emitters

The photoluminescence emission by mesoscopic condensed matter is ultimately dictated by the fine-structure splitting of the fundamental exciton into optically allowed and dipole-forbidden states. In epitaxially grown semiconductor quantum dots, nonradiative equilibration between the fine-structure levels is mediated by bulk acoustic phonons, resulting in asymmetric spectral broadening of the excitonic luminescence. In isolated colloidal quantum dots, spatial confinement of the vibrational motion is expected to give rise to an interplay between the quantized electronic and phononic degrees of freedom. In most cases, however, zero-dimensional colloidal nanocrystals are strongly coupled to the substrate such that the charge relaxation processes are still effectively governed by the bulk properties. Here we show that encapsulation of single colloidal CdSe/CdS nanocrystals into individual organic polymer shells allows for systematic vibrational decoupling of the semiconductor nanospheres from the surroundings. In contrast to epitaxially grown quantum dots, simultaneous quantization of both electronic and vibrational degrees of freedom results in a series of strong and narrow acoustic phonon sidebands observed in the photoluminescence. Furthermore, an individual analysis of more than 200 compound particles reveals that enhancement or suppression of the radiative properties of the fundamental exciton is controlled by the interaction between fine-structure states via the discrete vibrational modes. For the first time, pronounced resonances in the scattering rate between the fine-structure states are directly observed, in good agreement with a quantum mechanical model. The unambiguous assignment of mediating acoustic modes to the observed scattering resonances complements the experimental findings. Thus, our results form an attractive basis for future studies on subterahertz quantum opto-mechanics and efficient laser cooling at the nanoscale