Electronic circular dichroism imaging (CD<i>i</i>) maps local aggregation modes in thin films of chiral oligothiophenes

Albano, Gianluigi; Górecki, Marcin; Bari, Lorenzo Di; Jávorfí, Tamás; Hussain, Rohanah; Siligardi, Giuliano

doi:10.1039/c9nj02746g

Cited by 51 publications

(68 citation statements)

References 38 publications

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“…1). High resolution (50-100 μm) spatially resolved CD imaging confirms that this chiroptical response is remarkably uniform over large areas ( Supplementary Fig 2) 36,37 . As has been reported elsewhere, the cross-coupling of linear birefringence (LB) and linear dichroism (LD) and CP-selective reflection from structurally-chiral cholesteric stacks can result in apparent optical activity 18,38 .…”

Section: Resultsmentioning

confidence: 61%

Natural optical activity as the origin of the large chiroptical properties in π-conjugated polymer thin films

et al. 2020

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Polymer thin films that emit and absorb circularly polarised light have been demonstrated with the promise of achieving important technological advances; from efficient, high-performance displays, to 3D imaging and all-organic spintronic devices. However, the origin of the large chiroptical effects in such films has, until now, remained elusive. We investigate the emergence of such phenomena in achiral polymers blended with a chiral small-molecule additive (1-aza[6]helicene) and intrinsically chiral-sidechain polymers using a combination of spectroscopic methods and structural probes. We show that – under conditions relevant for device fabrication – the large chiroptical effects are caused by magneto-electric coupling (natural optical activity), not structural chirality as previously assumed, and may occur because of local order in a cylinder blue phase-type organisation. This disruptive mechanistic insight into chiral polymer thin films will offer new approaches towards chiroptical materials development after almost three decades of research in this area.

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Section: Resultsmentioning

confidence: 61%

Natural optical activity as the origin of the large chiroptical properties in π-conjugated polymer thin films

et al. 2020

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“…High resolution (50 -100 µm) spatially resolved circular dichroism imaging confirms that this chiroptical response is remarkably uniform over large areas ( Figure S2). 36,37 As has been reported elsewhere, the cross-coupling of linear birefringence (LB) and linear dichroism (LD) and CP-selective reflection from structurally-chiral cholesteric stacks can result in apparent optical activity. 18,38 For example, in liquid-crystalline materials that are configured in a nematic chiral helicoidal structure, the pitch can be tuned such that the modulation of refractive index through a given thickness produces an apparent CD due to circular birefringence.…”

Section: Resultsmentioning

confidence: 77%

“…gas. Details of the experimentally set up can be found in references 36,37 . For the in situ heating/cooling measurements, the heating rate was 10 °C/minute and the samples were held at a given temperature for 1 minute before spectra were acquired.…”

Section: Photophysical and Morphological Characterizationmentioning

confidence: 99%

A Unified Model to Explain the Large Chiroptical Effects in Polymer Systems Through Natural Optical Activity

Wade¹,

Hilfiker²,

Brandt³

et al. 2020

Preprint

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<div><div><div><p>Polymer thin films that emit and absorb circularly polarised light have been demonstrated with the promise of achieving important technological advances; from efficient, high-performance displays, to 3D imaging and all-organic spintronic devices. However, the origin of the large chiroptical effects in such films has, until now, remained elusive. We investigate the emergence of such phenomena in achiral polymers blended with a chiral small-molecule additive (1-aza[6]helicene) and intrinsically chiral-sidechain polymers using a combination of spectroscopic methods and structural probes. We show that – under conditions relevant for device fabrication – the large chiroptical effects are caused by coupling of electric and magnetic transition dipole moments (natural optical activity), not structural chirality as previously assumed, and may occur because of local order in a cylinder blue phase-type organisation. This disruptive mechanistic insight into chiral polymer thin films will offer new approaches towards chiroptical materials development after almost three decades of research in this area.</p></div></div></div>

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“…Respect to the two first classes of compounds, organic dyes are usually less toxic and their optical properties (Stokes shift, quantum yield, thermal-and photo-stability) can be optimized by modifying the structure of organic molecules. Many of them possess one or more heterocyclic nuclei such as thiazoles, imidazoles, benzothiazoles, benzodithiophenes, oxazines, lactones, pyrans, pyrroles, thiophenes, pyridines, pyrimidines, and dithienosiloles [21][22][23][24][25][26][27][28][29][30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Photophysical properties of new p-phenylene- and benzodithiophene-based fluorophores for luminescent solar concentrators (LSCs)

et al. 2020

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In this study, we report on the synthesis of new organic fluorophores containing either the pphenylene or the benzodithiophene cyclic nucleus connected to thiophene units via triple bonds and carbonyl group, and on their application for the fabrication of luminescent solar concentrators (LSCs). Their optical properties were evaluated. Independent of the core, dyes containing the COthiophene residues seem to be the most promising for LSCs applications. In fact, carbonyl groups only slightly lower quantum yield but significantly increase the red-shift so that the superimposition between the absorbance spectrum and the emission one is diminished. In the case of the benzodithiophene centre, light emission in the yellow-red portion of the spectrum is achieved. The latter dye is then selected for tests in a poly(methyl methacrylate) (PMMA) matrix. It showed good compatibility and homogenous distribution, no auto-absorption phenomena, and optical efficiencies of about 8% at 1 wt. %, i.e. comparable with those PMMA/Lumogen Red films in the same range of concentration.

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Electronic circular dichroism imaging (CDi) maps local aggregation modes in thin films of chiral oligothiophenes

Abstract: A detailed investigation of the circular dichroism imaging (CDi) technique on thin films of a chiral 1,4-dialkoxyphenylene-based oligothiophene with outstanding chiroptical features revealed the primary role of local supramolecular structures.

Cited by 51 publications

References 38 publications

Natural optical activity as the origin of the large chiroptical properties in π-conjugated polymer thin films

Natural optical activity as the origin of the large chiroptical properties in π-conjugated polymer thin films

A Unified Model to Explain the Large Chiroptical Effects in Polymer Systems Through Natural Optical Activity

Photophysical properties of new p-phenylene- and benzodithiophene-based fluorophores for luminescent solar concentrators (LSCs)

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