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. 2013:4:1969.
doi: 10.1038/ncomms2969.

Nonvolatile liquid anthracenes for facile full-colour luminescence tuning at single blue-light excitation

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Free PMC article

Nonvolatile liquid anthracenes for facile full-colour luminescence tuning at single blue-light excitation

Sukumaran Santhosh Babu et al. Nat Commun. 2013.
Free PMC article

Abstract

Nonvolatile room-temperature luminescent molecular liquids are a new generation of organic soft materials. They possess high stability, versatile optical properties, solvent-free fluid behaviour and can effectively accommodate dopant dye molecules. Here we introduce an approach to optimize anthracene-based liquid materials, focussing on enhanced stability, fluorescence quantum yield, colour tunability and processability, with a view to flexible electronic applications. Enveloping the anthracene core in low-viscosity branched aliphatic chains results in stable, nonvolatile, emissive liquid materials. Up to 96% efficient energy-transfer-assisted tunable emission is achieved by doping a minute amount of acceptor dye in the solvent-free state. Furthermore, we use a thermoresponsive dopant to impart thermally controllable luminescence colours. The introduced strategy leading to diverse luminescence colours at a single blue-light excitation can be an innovative replacement for currently used luminescent materials, providing useful continuous emissive layers in developing foldable devices.

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Figures

Figure 1
Figure 1. Molecular structure of anthracenes and dopants.
The figure shows the chemical structure of anthracenes (1–4) and dopants (D1 and D2) used in this study.
Figure 2
Figure 2. Characterization of solvent-free room-temperature liquid anthracenes.
(a) DSC thermograms in the cooling trace showing the glass-transition temperatures (Tg). (b) XRD diagrams with small-angle X-ray scattering profiles as insets, variation of (c) storage modulus (G′)(circles) and loss modulus (G″) (squares), as well as (d) complex viscosity (η*), (diamonds) versus angular frequency on double logarithmic scale, of 1 (blue markers) and 2 (red markers).
Figure 3
Figure 3. Photostability studies.
Comparison of the variation of (a) fluorescence intensity at 430 nm in solvent-free states of 1 and 4 (Solvent-free, Film) supported on a quartz plate and in dichloromethane solution (Solution) (c=1 × 10−4 M, l=1 mm, λex=375 nm) of 1 and 4. (b) Variation of the 1H NMR peak area of aromatic protons of 1 (7.7 p.p.m.) and 4 (7.5 p.p.m.) in dichloromethane-d2.
Figure 4
Figure 4. Optical features of liquid anthracenes.
Comparison of the normalized (a) absorption and (b) fluorescence spectra of 1 and 2 in a solvent-free bulk liquid state (solvent-free) supported on a quartz plate at room temperature and in dichloromethane solution (Solution) (c=5 × 10−5 M, l=1 mm, λex=375 nm). Photographs of 2 under (c) visible and (d) ultraviolet light (365 nm).
Figure 5
Figure 5. Energy-transfer-assisted tunable emission.
(a) Normalized emission spectral changes of 1 upon increasing the concentration of D1 (λex=350 nm). (b) Emission lifetime decay profile of 1 (blue squares) (λex=377 nm) in the presence of 0.3 (orange squares) and 0.5 mol% (pink squares) of D1 monitored at 430 nm supported on quartz plate, and inset shows the decay profiles of D1 (0.3 mol%) in the matrix of 1 (red squares) and D1 alone (blue squares), monitored at 475 nm (λex=377 nm). IRF corresponds to Instrument Response Function. (c) Photographs of the luminescent thin films of 1 (i) and 1 doped with D1 (ii–v), which are correlated to the emission spectra of (a).
Figure 6
Figure 6. Tunable emission colours from liquid composites.
(a) Photographs of the luminescence colour tunability and thermoresponsive feature of the composites of 1, D1 (0.5 mol%) and D2 (5 mol%). (b) Thermoreversible luminescence spectral changes of the composite of 1, D1 and D2, supported on a quartz plate (λex=375 nm) upon heating; inset shows the corresponding emission changes from 600 to 640 nm. (c) Commission internationale de l′éclairage coordinate values of the overall colour tunability achieved by doping of 1 with D1 and/or D2, as well as with temperature. The Commission internationale de l′éclairage coordinate also includes 2. The indications of ii–v are from the composites of 1 and D1 (Fig. 5), vi–x are from the composites of 1 and D2 (Supplementary Fig. S14a) and xi–xv are from composites of 1, D1 and D2 (b).

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