Abstract
We report on the vacuum thermal deposition of bilayer thin films of the luminescent complex Ir(ppy)3, tris[2-phenylpyridinato-C2,N]iridium(III), and the spin crossover complex [Fe(HB(tz)3)2], bis[hydrotris(1,2,4-triazol-1-yl)borate]iron(II). Switching the spin state of iron ions from the low spin to the high spin state around 337 K leads to a reversible jump of the luminescence intensity, while the spectrum shape and the luminescence lifetime remain unchanged. The luminescence modulation occurs due to the different UV light absorption properties of the iron complex in the two spin states and its magnitude can therefore be precisely adjusted by varying the film thickness. These multilayer luminescence switches hold potential for micro- and nanoscale thermal sensing and imaging applications.
Highlights
Fluorescence switches are systems, which contain a light-emitting fragment whose emission can be quenched reversibly through an external parameter [1]
We have shown that the intrinsic properties of the two layers were not affected by the presence of the other
The luminescence intensity reversibly increased when the spin crossover molecules were switched from the low spin (LS) to the high spin (HS) state in the uppermost layer
Summary
Fluorescence switches are systems, which contain a light-emitting fragment whose emission can be quenched reversibly through an external parameter [1]. To obtain a modification of the luminescence activity, an external stimulus (chemical, thermal, mechanical, etc.) is applied to the system [6,7,8,9] In this context of luminescence switching, an attractive strategy consists of fabricating a hybrid material, which combines a luminophore species with a spin crossover (SCO) molecule. This will lead to a modulation of the luminescence intensity and, in certain cases, to spectral shifts, but the excited state lifetime of the luminophore will remain obviously unaffected This ‘emission—reabsorption’ mechanism has been proposed to be dominant in refs [20,21]. We show that by an appropriate combination of materials their properties can be preserved by this straightforward approach and it becomes possible to modulate, in a fully reversible and predictable manner, the emission intensity of a luminescent film using a thin, transparent SCO top-coating
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