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A designed aggregation-induced emission enhancement (AIEE) active fluorescence probe 2,3-Bis-[(2-hydroxy-napthalen-1-ylmethylene)-amino]-but-2-enedinitrile (L) was synthesized via one step condensation method. The probe shows swift sensitivity and selectivity toward Al3+over other relevant metal ions and also exhibits significant AIEE phenomena in methanol/water mixture. Significant enhancement of fluorescence intensity is triggered via chelation-enhanced fluorescence through complex (Al3+-L) formation. A 2:1 metal to ligand ratio is observed from Job's plot based on UV − Vis absorption titration and detection limit (LOD) is found as low as 31.14 nM. Moreover, 1H NMR titrations and fluorescence reversibility by adding Al3+ and EDTA sequentially had been performed to establish the binding site of sensor complex (Al3+-L). Time-resolved photoluminescence, dynamic light scattering, optical microscopy, and on-site visualization studies have been performed to understand the AIEE mechanism of L in different volume percentage of water and methanol mixture. An INHIBIT molecular logic gate has been constructed utilizing the fluorescence behavior of the probe, L in presence of Al3+ and strong chelating ligand EDTA. [ABSTRACT FROM AUTHOR]

Fluorescent chemosensor, 3-(Anthracen-2-yliminomethyl)-benzene-1,2-diol (ANB) has been synthesized by one-step condensation of 2-aminoanthracene and 2,3-dihydroxybenzaldehyde and characterized using 1H-NMR, FT-IR and Mass spectroscopic techniques. The probe ANB was found to be an efficient 'turn-on' fluorescence chemosensor for the selective detection of Al3+ ion over other metal ions in an aqueous solution. The chemosensor exhibits ~ 27-fold enhancement of emission intensity in presence of Al3+ ion. Fluorescence quantum values for ANB and (Al3+-ANB)-complex are 0.004 and 0.097, respectively. In addition, the binding constant and the limit of detection were found to be 1.22 × 104 M−1 and 0.391 µM, respectively. The chemosensor ANB binds to Al3+ ions in 2:1 stoichiometric ratio which was supported by Job's plot, 1H-NMR titration and florescence titration. Fluorescence reversibility of the sensor complex was well established by adding EDTA in the same condition and a molecular INHIBIT logic gate was fabricated using this reversible nature of the sensor complex. Additionally, the chemosensor ANB shows a novel aggregation-induced enhanced emission phenomenon, where the aggregate hydrosol of ANB shows enhance emission intensity. [ABSTRACT FROM AUTHOR]

A multi responsive fluorescent probe, N',2-bis(E-4-(diethylamino)-2-hydroxybenzylidene)hydrazine-1-carbothiohydrazideV(H2L) has been synthesized through one step condensation method. Probe, H2L shows 'turn-on' dual sensing properties towards Cd2+ and H2AsO4− at two distinct wavelength. The probe (H2L) is spectroscopically characterized and the chemo-sensing mechanism has been demonstrated through 1H NMR, absorption, steady state and time resolved emission study. The most promising advantage of the probe is its application in the one-pot detection of Cd2+ (λem = 462 nm) and H2AsO4−(λem = 492 nm) where intense emission appears at two different wavelengths and the observed limit of detection (LOD) of H2L towards Cd2+ and H2AsO4− are 2.67 × 10–8 M and 5.14 × 10–6 M respectively. Further the 'turn-on' emission property of H2L towards Cd2+ is applied to construct INHIBIT logic gate. [ABSTRACT FROM AUTHOR]

A Fluorescent chemosensor based on pyrene scaffold, 5-diethylamino-2-(pyren-1-yliminomethyl)-phenol (PDS) is synthesized using condensation method. It displays novel aggregation-induced emission (AIE) phenomena in its aggregated/solid state. The AIE characteristic of PDS is studied in CH3CN/H2O mixtures at different volume percentage of water and morphology of the aggregated particles are investigated by DLS and optical fluorescence microscopic study. The probe is aggregated into ordered one-dimensional (1-D) rod like microcrystals and exhibit high efficiency of solid-state emission with green colour. By taking advantage of its interesting AIE feature, the aggregated hydrosol has been utilized as 'off–on' type fluorescence switching chemosensor with superb selectivity and sensitivity towards Cu2+ions and the limit of detection (LOD) was calculated as low as 6.3 µM. A high Stern–Volmer quenching constant was estimated to be 2.88 × 105 M−1. The proposed chemosensor with AIE feature reveals a prospective view for the on-site visual recognition of Cu2+ ions in fluorescent paper strips and the synthesized probe is also exploited to find out the concentration of Cu2+ions in real water samples. [ABSTRACT FROM AUTHOR]

1-(Pyridin-2-yl-hydrazonomethyl)-naphthalen-2-ol (PNOH) is a naphthalene-based fluorescence dual chemo-sensor for Al3+ and Zn2+. The probe (PNOH) is spectroscopically characterised and the chemo-sensing mechanism has been demonstrated through 1H NMR, absorption and both steady state and time resolved fluorescence study. The 'turn-on' luminescence property of PNOH is used for the selective detection of trace amount of Al3+and Zn2+via chelation enhanced fluorescence (CHEF) through complex formation. The 1:1 stoichiometry of each sensor-metal complex is observed from Job's plot based on UV-Vis titration. Most promising advantage of the probe (PNOH) is its application in the one-pot detection of Al3+ (λem- 460 nm) and Zn2+ (λem- 510 nm) exciting at same wavelength (λex- 420 nm) while high intense emission appears at two different wavelengths. Limit of detection (LOD) of PNOH towards Al3+ & Zn2+ are found to be 60 nM & 365 nM respectively. Real water sample analysis has also been demonstrated by using the probe PNOH. [ABSTRACT FROM AUTHOR]

A 2,6-diformyl-p-cresol (DFC)-4-amino antipyrine (AP) based dual signaling fluorescent Schiff base ligand (DFCAP) is found to exhibit colorimetric and fluorescence turn on selective sensing towards metal ions, Zn2+ and Al3+. It also exhibits a significant aggregation induced emission (AIE) phenomenon by controlling the water–THF solvent ratio which provides robust green emissive fluorogenic aggregates with well-defined morphologies. Turn-on fluorescence enhancements as high as 195 fold and 168 fold in methanol for Al3+ and Zn2+ at 480 nm and 508 nm, respectively, were noticed. The binding constants and stoichiometry determined from the fluorescence titration data are K = 7.63 × 104 M−1 and 3.42 × 104 M−1 and 1 : 1 complexation for both Al3+ and Zn2+ respectively, supported by Job's method. DFCAP shows high sensitivity towards the detection of Zn2+ and Al3+ ions with very low detection limit values of ca. ∼21 nM and 30 nM respectively. Besides by applying its attractive AIE feature, the green emissive hydrosol functions as a good chemosensor with high sensitivity for a selected explosive TNP through ground state complexation with a LOD value of ca. ∼1.74 μM and especially a high Stern–Volmer quenching constant of ca. ∼4.14 × 105 M−1. For instant 'naked eye' response for the trace detection of TNP in the solution state, we fabricated a simple paper strip that could detect TNP on-site in a fast, inexpensive and simple way. [ABSTRACT FROM AUTHOR]

An Anthracene based fluorescent probe, 1-(Anthracen-2-yliminomethyl)-napthalen-2-ol (AIN), was synthesized via simple one-pot reaction from inexpensive reagents. Intriguingly, it exhibited novel AIE characteristics in H 2 O-THF mixtures at high water content. Size and growth process of particles in different volume percentage of water and THF mixtures were investigated using TRPL, DLS, SEM and optical microscope. The fluorescent aggregates exhibited distinct Hg 2+ -selective “on-off” type fluorescence switching upon binding. Additionally, the fluorescence quenching showed a linear correlation in the Hg 2+ concentration range from 0.3 to 3.6 μM and the limit of detection was estimated as low as ∼3 ppb. The drastic decrease in emission intensity of AIN aggregates was observed in the presence of mercury ions via a complex interplay through the ground state complexation between AIN and Hg 2+ ions and external heavy atom induced perturbation by Hg 2+ ions to the excited states of the AIN. A large Stern–Volmer quenching constant was estimated to be 2.54 × 10 5  M −1 . The proposed analytical system with clear AIE characteristics demonstrates a potential outlook for the on-site visual detection of Hg 2+ in paper strips. Finally, the sensory probe was also applied to determine the concentration of Hg 2+ in real water samples to demonstrate its practical applications. [ABSTRACT FROM AUTHOR]

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]

A novel material showing aggregation induced enhanced emission (AIEE) is developed by reprecipitation method using 2,2′ biquinoline (BQN) in aqueous medium. Morphologies of the particles are characterized using optical and scanning electron microscopic (SEM) study. The selective fluorescence and absorbance response of aggregated BQN towards Zn 2+ and H + have been explained due to ground state complexation and protonation of BQN with Zn 2+ and H + respectively. Protonated BQN exhibits charge transfer character in transoid form with yellowish green emission but in BQN-Zn 2+ complex, BQN changes to cis planer conformation and displays considerable intra ligand charge transfer (ILCT) character with sky blue color under UV excitation. A 2:1 BQN-Zn 2+ complex have been confirmed using Job’s plot. Our study revealed that BQN hydrosol act as selective turn-on fluorescence sensor for Zn 2+ ion both in acidic and alkaline medium. Further, the proton induced charge transfer character and the proposed binding modes of the receptor with Zn 2+ have been supported by DFT based computational study. [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]

α-Napthoflavone (ANF) microstructures of various morphologies were synthesized using reprecipitation method. Sodium Dodecyl Sulfate (SDS) was used as morphology directing agent. The morphologies of the particles were characterized using optical and scanning electron microscopy (SEM). Single crystal data of ANF suggests that the aromatic units of ANF are in parallel slipped conformation in its aggregated form. Photophysical properties of aggregated ANF hydrosol were studied using UV–Vis absorption, steady state and time resolved spectroscopy. Red shift and broadening of UV–Vis spectra of ANF hydrosol are explained due to strong π-π and H-π interactions among the neighboring ANF molecules within the aggregated microstructures. Though ANF is non-luminescent in good solvent, a strong emission is observed in its aggregated state. This aggregation induced emission (AIE) has been explained due to restriction of intramoleculer rotation and large amplitude vibrational modes of ANF in its aggregated state. Our Photophysical study also reveals that AIE effect decreases after an optimum concentration of ANF and this has been explained due to softening of crystal lattice. Cytotoxicity of ANF hydrosol was examined to get an idea of the toxic level of this hydrosol toward cultured normal human cells. It is observed that ANF hydrosol may draw beneficial effect in biological application as it has no higher toxic activity but has antioxidant property. [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]