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Tunable Emission from Fluorescent Organic Nanoparticles in Water: Insight into the Nature of Self‐Assembly and Photoswitching
Author(s) -
Gulyani Akash,
Dey Nilanjan,
Bhattacharya Santanu
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201704607
Subject(s) - fluorescence , chromophore , nanoparticle , self assembly , photochemistry , luminescence , moiety , excimer , molecule , chemical physics , chemistry , absorption (acoustics) , benzothiazole , materials science , nanotechnology , optoelectronics , stereochemistry , organic chemistry , optics , physics , composite material
Excitation‐dependent tuning of the emission behavior of fluorescent organic nanoparticles (FONs) with two simple luminescent pyrenyl–pyridyl conjugates as model systems is demonstrated. In the case of the compound with a flexible bis‐picolyl moiety, the simultaneous presence of multiple ground‐state species with distinct absorption and emission characteristics can be observed. The relative ratios of these species can easily be modulated, and it is possible to selectively stimulate any one of them individually by choosing an appropriate excitation channel. Moreover, at high concentration, a drastic change in the nature of the self‐assembly is observed, which shifts from donor–acceptor‐type self‐assembly to exciplex‐type self‐agglomeration. On the contrary, the compound containing a rigid terpyridine unit has only a single ground state and shows no such tunable emission. However, it can exhibit multiple emission bands in water, whereby the positions of their emission maxima depend on the extent of aggregation‐induced planarization of the probe molecules. Overall, this work demonstrates multimodal modulation of FON emission and a gives insight into how molecular order can translate into complete switching of nanoparticle self‐assembly and photophysics.