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Pendant chain engineering to fine-tune nanomorphology and solid state luminescence in naphthalimide AIEEgens: Application to phenolic nitro-explosive detection in water

Abstract

Strategically, a series of five angular ‘‘V’’ shaped naphthalimide AIEEgens with varying pendant chains (butyl, hexyl, octyl, cyclohexyl and methylcyclohexyl) have been synthesized to fine-tune their nanomorphological and photophysical properties. With similar aromatic core and electronic state, for the first time, unexpected tuning in condensed state emission color and nanomorphology (reproducible on any kind of surface) has been achieved just by varying the side chain. Conclusive analysis of various spectroscopic techniques (SC-XRD, powder-XRD, DLS, FESEM) and DFT computational studies confirmed the full control of pendant chain (in terms of bulkiness around the naphthalimide core which restricts the ease of intermolecular π—π interactions) over the nanoaggregate morphology and solid state emissive properties that can be rationalized to all aggregation prone system. The comprehensive studies establish a conceptually unique yet simple and effective method to precisely tune the nanomorphology and the emission color in aggregation-prone small organic molecules by judicious choice of the non-conjugated pendant chain. Thus, considering the prime role of active layer nanomorphology in all types of organic optoelectronic devices, this methodology could emerge as a promising tool to improve the device performances. Among all the congeners, hexyl chain containing congener (HNQ) forms well defined nanoribbons with smaller diameter (as confirmed from DLS; 166 nm and FESEM; 150 nm) and provides larger surface area. Consequently, the HNQ-nanoribbons were employed as a fluorescent sensor for the discriminative detection of trinitrophenol (TNP) in pure aqueous media. FE-SEM images revealed that, upon gradual addition of TNP (10 nM to 100 µM), these nanoribbons endure an aggregation/disaggregation process forming non-fluorescent co-aggregate with TNP and provide highly enhanced sensitivity from the existing state of art. The fluorescence titration studies confirmed that HNQ can detect the presence of TNP as low as 16.8 ppb and can serve as a cost-effective portable device incorporated with UV-light for on-site visual detection of TNP even in the presence of potentially competing other nitroaromatic compounds.

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Publication details

The article was received on 27 Mar 2017, accepted on 07 May 2017 and first published on 10 May 2017


Article type: Paper
DOI: 10.1039/C7NR02174G
Citation: Nanoscale, 2017, Accepted Manuscript
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    Pendant chain engineering to fine-tune nanomorphology and solid state luminescence in naphthalimide AIEEgens: Application to phenolic nitro-explosive detection in water

    N. Meher and P. K. Iyer, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR02174G

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