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Latent fingerprints (LFPs) identification is of paramount importance for national security and criminal investigations. We designed and synthesized fluorescent organic molecule HPBI for the rapid fluorescence imaging of latent fingerprints on various surfaces such as aluminium foil, currency paper, brick, and glass, which did not require any post treatment. The HPBI exhibits a combination of ESIPT and AIE properties and forms green fluorescent nano-aggregates in CH3CN–H2O (1 : 1) mixture, as evaluated by DFT, SEM, TEM, and fluorescent microscopic studies. Spraying the solution of spherical HPBI nanoaggregates (50–100 nm size) on various surfaces resulted in fluorescence display of LFPs in <2 minutes. LFPs clearly revealed level-2 (ridge ending, islands, bifurcation) and level-3 (ridges path deviation, edge contours, sweat pores) details with high contrast and no background interference. The relocation of fluorescent fingerprints on cello tape provides an efficient and clean method for carrying fingerprints to the forensic laboratory. [ABSTRACT FROM AUTHOR]

The nitroaromatic compounds (NACs) show absorption maxima below 400 nm and their determination using absorption and colour change requires probes with absorption beyond this region. Herein, we report a stilbazolium-based probe DMAS-DP, which undergoes aggregation in HEPES buffer with an absorption maximum at 475 nm (red colour) and these aggregates demonstrate a highly selective and sensitive change in their colour from red to light yellow with 2,4,6-trinitrophenol (TNP). The LOD for the determination of TNP is 100 pM, the lowest in the literature by using visible spectroscopy. Moreover, the aggregates of DMAS-DP emit fluorescence in the red region with a maximum at 615 nm (red under 365 nm light), which is quenched selectively by TNP. 2,4,6-Trinitrotoluene (TNT) and other NACs show insignificant changes in the visible spectrum of the aggregates of DMAS-DP, even when present in excess. Density functional theory (DFT)-based structure optimization studies reveal that the DMAS-DP attains the Z-conformation and its dimethylamino moieties form strong interaction with the protons of TNP and are responsible for the reduced force constant (color). This constitutes the first probe where a stilbazolium dye has been used for constructing a TNP-selective chromogenic and red-fluorescent probe. [ABSTRACT FROM AUTHOR]

We report the synthesis of probe 2 for the fluorescence “turn-on” detection of Al3+ ions in CH3OH. Probe 2 has been designed via utilizing the aggregation-induced emission properties of the tetraphenylethylene unit, with further enhancement from Schiff base units for the ESIPT phenomenon. Probe 2 exhibits emission at 548 nm (λex = 360 nm), with a large Stokes shift of 188 nm, indicating the ESIPT phenomenon. Probe 2 also exhibits emission enhancement via increasing the H2O ratio up to 70–90% H2O/THF (v/v) and altering the spherical morphology to needle shapes. Probe 2 has been found to be highly selective and sensitive towards Al3+ ions over other metal ions in pure CH3OH using absorption and emission spectroscopy. FESEM analysis revealed that the size of probe 2 increases upon the addition of Al3+ ions. Thus, the fluorescence “turn-on” behaviour of probe 2·Al3+ is due to metal-induced aggregation. [ABSTRACT FROM AUTHOR]

A donor–π–acceptor (D–π–A) dyad 1 has been successfully synthesized by linking phenanthrenequinone as an electron donor unit and anthraquinone as an electron acceptor unit through a phenyl ring. Dyad 1 exhibits intramolecular charge transfer and this is a key factor for the detection of Hg2+ and of the pyrophosphate ion (P2O74−, PPi) in a semi-aqueous medium. Dyad 1 exhibits absorption peaks at 430, 370, and 337 nm and an emission peak at 530 nm (λex = 430 nm). Dyad 1 exhibits a new absorption peak at 390 nm ratiometrically along with emission quenching in the presence of Hg2+ ions while the presence of PPi results in drastic ratiometric changes in the absorption and emission spectra with new peaks at 495 nm and 620 nm, respectively. The quantum yield of dyad 1 on complexation with PPi was also increased from 0.1 (free dyad) to 0.69 (dyad 1·PPi). The lowest detection limits for Hg2+ and PPi were found to be 31 nM and 46.5 nM, respectively. DFT calculations have been performed to develop a mechanism for PPi and Hg2+ ion binding with dyad 1. [ABSTRACT FROM AUTHOR]

A BINOL (1,1′-bi-2-naphthol)-based probe 1 with a diamide group has been synthesized and investigated for its photophysical behavior towards various cations and anions. Probe 1 has been used for the estimation of Al3+ and Cu2+ ions in the presence of other metal ions, signaling the binding event through the formation of new absorption bands at 415 and 430 nm. Differential emission bands are formed in the presence of Al3+ at 515 nm and Zn2+ at 485 nm, while quenching is observed in case of Cu2+ ion. Probe 1 shows selective estimation for CN− ion among all other anions by forming a new absorption band at 395 nm and new emission band at 495 nm, with the lowest detection limit of 2 μM. Based on these results, the anion/cation as well as cation/cation 2-to-1 encoder and 1-to-2 decoder have been formed. Moreover, a 4-to-2 encoder has also been established by using various cations as inputs. [ABSTRACT FROM AUTHOR]

An efficient strategy has been developed for the deformylative halogenation of carbaldehyde imidazo-fused heterocycles in the presence of TBHP controlled by temperature. A convenient and sequential functionalization (C8 to C3) portrays the synthetic utility of the current method. N-Heterocycle benzamide products were also observed via the ring opening of imidazopyridines through the cleavage of C–C bond at high temperatures. Features of this method include temperature-controlled excellent regioselectivity, mild conditions and functional group tolerance. [ABSTRACT FROM AUTHOR]

A 2-(2-hydroxyphenyl)benzothiazole based probe BTNN undergoes a drastic upsurge (∼146-fold, Φ = 69%) in fluorescence intensity (bright green, λem 530 nm) on going from pH 7 to 2. MG-63 cells and E. coli bacteria internalize BTNN without toxicity and its fluorescence intensity is directly correlated to the pH in the cells/bacteria. This response to pH is instantaneous, reversible and stable for over a week. The protonation of the diethylamino nitrogen followed by efficient normal and excited state intramolecular proton transfer (ESIPT) processes of protonated BTNN are responsible for remarkable increase in fluorescence intensity and quantum yield under acidic conditions. Furthermore, polystyrene-BTNN thin films can be used for efficient detection of HCl vapour (2 ppm). This is first example where 2-(2-hydroxyphenyl)benzothiazole derivative can image strong acidic conditions. [ABSTRACT FROM AUTHOR]