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Towards direct monitoring of discrete events in a catalytic cycle at the single molecule level
Ameloot, Rob,Roeffaers, Maarten,Baruah, Mukulesh,De Cremer, Gert,Sels, Bert,De Vos, Dirk,Hofkens, Johan Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.4
The binding state dependent quenching behaviour of functionalized dyes opens perspectives on directly monitoring binding and dissociation events in a catalytic cycle at the single molecule level.
Goossens, Karel,Prior, Mira,Pacheco, Victor,Willbold, Dieter,Mü,llen, Klaus,Enderlein, Jö,rg,Hofkens, Johan,Gregor, Ingo American Chemical Society 2015 ACS NANO Vol.9 No.7
<P>Dual-focus fluorescence correlation spectroscopy (2fFCS) is a versatile method to determine accurate diffusion coefficients of fluorescent species in an absolute, reference-free manner. Whereas (either classical or dual-focus) FCS has been employed primarily in the life sciences and thus in aqueous environments, it is increasingly being used in materials chemistry, as well. These measurements are often performed in nonaqueous media such as organic solvents. However, the diffusion coefficients of reference dyes in organic solvents are not readily available. For this reason we determined the translational diffusion coefficients of several commercially available organosoluble fluorescent dyes by means of 2fFCS. The selected dyes and organic solvents span the visible spectrum and a broad range of refractive indices, respectively. The diffusion coefficients can be used as absolute reference values for the calibration of experimental FCS setups, allowing quantitative measurements to be performed. We show that reliable information about the hydrodynamic dimensions of the fluorescent species (including noncommercial compounds) within organic media can be extracted from the 2fFCS data.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2015/ancac3.2015.9.issue-7/acsnano.5b02371/production/images/medium/nn-2015-02371p_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5b02371'>ACS Electronic Supporting Info</A></P>
Giant Electron-Phonon Coupling and Deep Conduction Band Resonance in Metal Halide Double Perovskite
Steele, Julian A.,Puech, Pascal,Keshavarz, Masoumeh,Yang, Ruoxi,Banerjee, Subhasree,Debroye, Elke,Kim, Cheol Woong,Yuan, Haifeng,Heo, Nam Ho,Vanacken, Johan,Walsh, Aron,Hofkens, Johan,Roeffaers, Maart American Chemical Society 2018 ACS NANO Vol.12 No.8
<P>The room-temperature charge carrier mobility and excitation-emission properties of metal halide perovskites are governed by their electronic band structures and intrinsic lattice phonon scattering mechanisms. Establishing how charge carriers interact within this scenario will have far-reaching consequences for developing high-efficiency materials for optoelectronic applications. Herein we evaluate the charge carrier scattering properties and conduction band environment of the double perovskite Cs<SUB>2</SUB>AgBiBr<SUB>6</SUB><I>via</I> a combinatorial approach; single crystal X-ray diffraction, optical excitation and temperature-dependent emission spectroscopy, resonant and nonresonant Raman scattering, further supported by first-principles calculations. We identify deep conduction band energy levels and that scattering from longitudinal optical phonons-<I>via</I> the Fröhlich interaction-dominates electron scattering at room temperature, manifesting within the nominally nonresonant Raman spectrum as multiphonon processes up to the fourth order. A Fröhlich coupling constant nearing 230 meV is inferred from a temperature-dependent emission line width analysis and is found to be extremely large compared to popular lead halide perovskites (between 40 and 60 meV), highlighting the fundamentally different nature of the two “single” and “double” perovskite materials branches.</P> [FIG OMISSION]</BR>