Abstract
Considerable achievements on multiple emission capabilities and tunable wavelengths have been obtained in inorganic luminescent materials. However, the development of organic counterparts remains a grand challenge. Herein we report a series of 2-/2,6-aryl substituted boron-dipyrromethene dyes with wide-range and multi-fluorescence emissions across red and near infrared in their aggregation states. Experimental data of X-ray diffraction, UV–vis absorption, and room temperature fluorescence spectra have proved the multiple excitation and easy-adjustable emission features in aggregated boron-dipyrromethene dyes. Temperature-dependent and time-resolved fluorescence studies have indicated a successive energy transfer from high to step-wisely lower-located energy levels that correspond to different excitation states of aggregates. Consistent quantum chemical calculation results have proposed possible aggregation modes of boron-dipyrromethene dyes to further support the above-described scenario. Thus, this study greatly enriches the fundamental recognition of conventional boron-dipyrromethene dyes by illustrating the relationships between multiple emission behaviors and the aggregation states of boron-dipyrromethene molecules.
Highlights
Considerable achievements on multiple emission capabilities and tunable wavelengths have been obtained in inorganic luminescent materials
The emission wavelengths of rare earth luminophors is very difficult to manipulate due to the shielding effect from exterior orbitals and the fixed energy levels of the rare earth ions while quantum dots suffer from both high toxicity of the heavy metals and environmentally sensitive emissions in the near infra-red (NIR) region, which have prevented them from even wider applications
Since most BODIPYs suffer from aggregation-caused emission quenching (ACQ), further manipulations such as decorating the classical BODIPY core (BDP) with bulky groups[19], asymmetrization of BDP20,21, and aggregation-induced emission (AIE) are usually involved to achieve solid-state emissions and satisfy various requirements[22,23,24] while less attention has been paid on the fluorescence properties of BODIPYs in their aggregated state
Summary
Considerable achievements on multiple emission capabilities and tunable wavelengths have been obtained in inorganic luminescent materials. 4 State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, 210046 Nanjing, China These authors contributed : Due to the urgently increased demand in the areas of optoelectronic devices, energy conversion, luminescence sensors, bioimaging, disease diagnosis, and photodynamic therapy, luminescent materials with multiple emission capabilities across a wide wavelength range, e.g., from visible to near infra-red (NIR), as well as with tunable excitation/emission wavelengths have drawn rapidly increased attentions from researchers working in the subjects including but not limited to chemistry, physics, materials, and biology[1,2,3,4]. Temperature-dependent and timeresolved fluorescence spectral results have suggested that J-aggregates with successively distributed and step-wisely lowerlocated energy levels are formed in the solid-state BDP1 to a
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