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Aggregate/solid-state fluorescence switching organic material, 4-((pyren-1-yl)methyleneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (PAP) was synthesized via simple one-step synthetic process. It exhibited novel aggregation induced emission (AIE) phenomenon by controlling water ratio in solutions which provide sturdy cyan emissive fluorogenic aggregates with diverse well-defined morphologies, especially tuning the morphologies from 0-D to 1-D microcrystals that show obvious optical waveguide effect. Dynamic light scattering, time-resolved photoluminescence, optical fluorescence microscope and scanning electron microscope were exploited to gain insight into the AIE mechanism and discrimination of the different aggregated morphologies such as 0-D hollow spheres, 1-D hexagonal, hexagonal 1-D growth, rods and wires with distinct emissions tuning in solid state. Intriguingly, triple excitation induced triple emissions of green, yellow and red lights were emanated from microstructures in solid state for the first time which completely covered visible spectral region. By taking the advantage of its attractive AIE feature, the fluorescent hydrosol employed itself as a fluorescent chemosensor with superb selectivity and sensitivity toward explosive TNP through ground state complexation with a detection limit as low as 16 nM and very high Stern–Volmer quenching constant of 4.7 × 10 5 M −1 . An instant ‘naked eye’ response for trace detection of TNP in solid state, we prepared the fluorescent paper strips which make the protocol simple, fast, inexpensive and practical for on-site visualization. [ABSTRACT FROM AUTHOR]

Morphologically interesting microstructures of 1-aminopyrene (1-PyNH 2 ) are synthesized using re-precipitation method. Two and three dimensional microparticles are obtained in presence of cetyl trimethyl ammonium bromide (CTAB) as morphology directing agent. One dimensional wire shaped microparticles are obtained in the absence of CTAB. Morphologies of the particles change from square to cuboids with increasing concentration of 1-PyNH 2 for a fixed concentration of CTAB (0.5 mM). Morphologies of the microparticles have been characterized using optical and scanning electron microscope. Photophysical properties of the particles are studied using UV-Vis, steady state fluorescence and time resolved fluorescence techniques. Computation of Fukui parameter as local reactivity descriptors suggests that the neighboring 1-PyNH 2 molecules are present in face to face slipped conformation in the aggregated structures. The fluorescence properties of aggregated 1-aminopyrene have been utilized for the selective detection of picric acid (PA) by turn off fluorescence intensity and this emission quenching is explained due to ground state complexation with a high quenching constant value, 5.04 × 10 8 M − 1 . [ABSTRACT FROM AUTHOR]

Morphologically interesting microstructures of benzo[a]pyrene (BaP) have been synthesized using sodium dodecyl sulfate (SDS) as morphology directing agent. Here we have presented a reprecipitation method to synthesize cube, rectangular bar, square rod and rectangular plate shaped microstructures of benzo[a]pyrene. Morphology of the materials has been characterized using optical microscopy and SEM measurements. UV–Vis absorption, fluorescence emission and computational study revealed that the neighboring BaP molecules are arranged in slipped head to head arrangement in its aggregated structures. Computation of second order Fukui parameter as local reactivity descriptor on each atomic center of the titled compound also substantiate that neighboring BaP molecules are arranged in parallel face to face slipped conformation in its aggregated structures and this is in conformity with the crystal structure of BaP. [ABSTRACT FROM AUTHOR]

• A novel fluorescent aggregates of 9,10-dihydrobenzo[a]pyrene-7(8H)-one is synthesized. • It produces distinct fluorescent crystalline microstructures from 0-D to 1-D. • The aggregates displayed excellent selectivity toward nitro-explosive 4-NP. • The fluorescent aggregates coated TLC strips detect 4-NP for an instant 'naked eye' response. • It is also applied to determine the concentration of 4-NP in real solid samples. A noteworthy fluorescence swelling was realized by designing a fluorescent polyaromatic molecule 9,10-dihydrobenzo[a]pyrene-7(8 H)-one (9,10-DHBaP) through aggregation-induced emission enhancement (AIEE) effect. The nano/microparticles can be engineered through molecular self-aggregation by steadily increasing the water volume percentages in mixed aqueous media. A significant fluorescence enhancement with a red shifted broad band both in absorption and emission spectrum of the aggregates has indicated the formation of J-aggregates. The aggregation characteristics have been investigated by spectroscopic and microscopic techniques. Morphology of the aggregated particles changes from rhombus to hexagonal type. The brilliant cyan emissive fluorescent hydrosol has been utilized as a sensor with superb selectivity and sensitivity toward water soluble nitro-explosive 4-nitro phenol (4-NP) compared to other nitro-aromatics. The limit of detection (LOD) is calculated to be 7.14 nM. The fluorescent paper strips are employed for instant 'naked eye' recognition of 4-NP in solid state that expose the technique fast, inexpensive, simple and practical for on-site finding of such pollutant. [ABSTRACT FROM AUTHOR]