Three-dimensional carbazole-based dendrimers: model structures for studying charge transport in organic semiconductor films

Mutkins, Karyn; Chen, Simon S. Y.; Pivrikas, Almantas; Aljada, Muhsen; Burn, Paul L.; Meredith, Paul; Powell, B. J.

doi:10.1039/c2py20670f

Cited by 22 publications

(12 citation statements)

References 56 publications

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“…The activation energy found from the diffusion coefficient was in good agreement with the results of precise ab initio quantum chemistry calculations [45,47]. The diameter of the dendrimers was calculated as 2.1 nm from its density and molecular mass, which is consistent with the average hydrodynamic diameter (2.2 nm) in solution calculated from the M v determined by gel permeation chromatography [48]. Room temperature corresponds to an energy of 2.4 kJ/mol and it can be seen that the determined activation energy for the sorption process is significantly higher.…”

Section: Neutron Measurements and Distribution Of Pnt In Filmsupporting

confidence: 72%

Diffusion of nitroaromatic vapours into fluorescent dendrimer films for explosives detection

Ali¹,

Chen²,

Cavaye³

et al. 2015

Sensors and Actuators B: Chemical

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Abstract:Fluorescence-based sensing with organic semiconductors is a powerful method for the detection of a broad range of analytes including explosives, chemical weapons and drugs.Diffusion of an analyte into an organic semiconductor thin film, and its subsequent interaction with the chromophore are key factors that govern the sensing performance of a chemosensor.In this study the diffusion behaviour of an explosive analyte analogue into a sensing film of a conjugated dendrimer was investigated using a quartz crystal microbalance (QCM) and correlated with neutron reflectivity measurements. The mechanistic insights of paranitrotoluene (pNT) sorption in the films of different thicknesses of a first generation dendrimer with fluorenyl surface groups, carbazole dendrons and a spirobifluorene core were studied and interpreted in terms of the underlying kinetics and thermodynamics. Sorption measurements suggest that the process of diffusion of pNT vapour into the dendrimer films is Super Case II, which involves swelling of the film. Swelling of the film was confirmed by neutron reflectometry measurements, which also showed uniform distribution of the pNT molecules throughout the entire film thickness. The activation energy barrier and change in Gibbs free energy in the sorption process were calculated from the QCM responses. The sorption process was found to be thermodynamically (not kinetically) controlled and independent of film thickness. This work sheds insight into the structure-property relationships that govern the performance of organic semiconductor fluorescence-based chemosensors.

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Section: Neutron Measurements and Distribution Of Pnt In Filmsupporting

confidence: 72%

Diffusion of nitroaromatic vapours into fluorescent dendrimer films for explosives detection

Ali¹,

Chen²,

Cavaye³

et al. 2015

Sensors and Actuators B: Chemical

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“…The structures of the dendrons and dendrimers investigated in this paper are illustrated in Figure . Although the steady-state absorption and photoluminescence (PL) spectra have been previously reported for the fluorene- and spirobifluorene-cored dendrimers , we have included a brief summary of them in this paper to set the scene for the transient and coherent two-dimensional spectroscopic measurements. The solution steady-state absorption and PL spectra of the dendrons and fluorene-cored dendrimers in THF are shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…In this paper, we study the photoinduced dynamics in a series of carbazole-based dendrons and dendrimers with fluorenyl surface groups with the structures shown in Figure . The synthesis of the compounds is reported elsewhere. , The number of levels of branching defines the generation, and we accordingly label them the first (G1), second (G2), and third (G3) generation. The dendrimers differ in their cores and hence the number of dendrons with the fluorene and spirobifluorene-cored dendrimers illustrated in the middle and the lower panels of Figure , respectively.…”

Section: Introductionmentioning

confidence: 99%

Photophysics of Delocalized Excitons in Carbazole Dendrimers

et al. 2013

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The photophysical properties in solution of three generations of carbazole-based dendrons and dendrimers with fluorenyl surface groups were studied using steady-state, time-resolved femtosecond transient absorption and anisotropy, and coherent two-dimensional ultraviolet spectroscopy. It was found that increasing the generation caused a switch in the nature of the emissive state between the first-generation compounds and the second- and third-generation dendrimers. Time-resolved anisotropy measurements revealed low initial anisotropies that decreased with increasing dendrimer generation consistent with increasing intradendrimer interchromophore coupling. Two-dimensional UV spectroscopy showed that the signal from the second- and third-generation dendrimers is the product of multiple chromophores interacting. The maximum number of interacting chromophores is reached by the second generation.

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“…19 While there is no formal delocalization through the central spiro carbon, it is clear that the chromophores within the two halves of the dendrimer are interacting, which is at least consistent with molecular orbital calculations showing that the highest occupied molecular orbital (HOMO) of SBF(G1) 4 is delocalized over the two halves of the dendrimer. 14 The time-resolved measurements of the PL decay show that the emission from the G1 dendron, which has a biexponential decay, is much longer lived than that from the dendrimers. Of the first-generation dendrimers, Fl(G1) 2 has the longest lifetime of 2.4 ns while SBF(G1) 4 has a lifetime of 1.6 ns.…”

Section: Methodsmentioning

confidence: 98%

“…The synthesis of the SBF-cored dendrimers have been previously reported. 14 Gel permeation chromatography against poly(styrene) standards showed that the dendrimers formed this way were all monodisperse; that is, they were discrete macromolecules. Thermal gravimetric analysis (TGA) showed that the dendrimers were stable to temperatures greater than 300 °C, and differential scanning calorimetry (DSC) showed that the dendrimers did not have a glass transition temperature within the experimental limits (0−280 °C).…”

Section: Methodsmentioning

confidence: 99%

High-Generation Dendrimers with Excimer-like Photoluminescence for the Detection of Explosives

et al. 2013

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We report three generations of dendrimers incorporating either a fluorene or spirobifluorene core with carbazole dendrons and fluorene surface groups that are effective sensing materials for the detection of nitrated explosives by fluorescence quenching. The photophysical properties of the dendrimers were investigated with a combination of steady-state absorption and photoluminescence and time-resolved photoluminescence. We show that the first-generation dendrimers behave as single chromophores while the higher-generation dendrimers contain multiple chromophores that interact to give excimer-like emissive states. Stern−Volmer measurements with nitrated analytes show that the quenching efficiency decreases with generation for the planar fluorene-cored dendrimers and increases with generation for the more three-dimensional spirobifluorene-cored dendrimers. These contrasting trends are shown to be caused primarily by changes in the quenching efficiency of static interactions with the nitrated analytes, which is a consequence of the choice of core. Our results highlight the potential for exploiting such excimer-like states for chemical sensing, particularly in the case of nitrated explosives.

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Three-dimensional carbazole-based dendrimers: model structures for studying charge transport in organic semiconductor films

Cited by 22 publications

References 56 publications

Diffusion of nitroaromatic vapours into fluorescent dendrimer films for explosives detection

Diffusion of nitroaromatic vapours into fluorescent dendrimer films for explosives detection

Photophysics of Delocalized Excitons in Carbazole Dendrimers

High-Generation Dendrimers with Excimer-like Photoluminescence for the Detection of Explosives

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