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A new turn on fluorescence probe based on 3′,6′-dihydroxy-6-methyl-2-((pyridin-2-ylmethylene)amino)-4-(p-tolyl)spiro[benzo[f]isoindole-1,9′-xanthen]-3(2H)-one (BFFPH) derived from benzo[f]fluorescein was prepared. Full characterization of the prepared probe using spectroscopic analysis was described such as IR, NMR and MS spectra. The sensitivity of BFFPH for monitoring of pH change in alkaline medium was studied. BFFPH exhibited a high sensitivity to alkaline pH by two pKa values at 8.82 and 10.66 in UV/vis spectroscopy titration. The pH monitoring was studied in broad range of pH values (2.5–12.2) at two pKa values at 8.72 and 10.73 by recording the effect of pH on the fluorescence intensity of BFFPH. The acid-base reversibility character of the probe was investigated as well as the effect of the pH change on the fluorescence quantum yield. The application of the prepared BFFPH probe for detection of living Escherichia coli (E. coli) bacteria using confocal fluorescence microscope was investigated. [ABSTRACT FROM AUTHOR]

A new, dual function colorimetric chemosensor and turn-off fluorescent probe based on pyrrolinone esters hydrazone dye bearing a terminal thiophene moiety (TPESHD) was designed, synthesized and investigated. The sensor exhibited highly selective and sensitive detection toward Cu2+ in ethanol aqueous solution with detection limit up to 0.63 μM of copper ion. The distinct color change and fluorescence quenching was visible to the naked eye from yellow to purple in case of copper over other metal cations tested (Na+, Mg2+, Mn2+, Fe3+, Co2+, Ni2+, Zn2+, Cd2+, Ag+, ....etc.). Also, the sensor showed high sensitivity to pH changes in the 7.25–12.5 range and the color of dye was changed from yellow to bluish color. The structure of the synthesized probe was confirmed by elemental analysis, nuclear magnetic resonance spectroscopy, and mass spectra. The dual chemosensor formed a 1:1 complex with Cu2+ and displayed fluorescent quenching. The binding mechanism with copper ions was confirmed by 1HNMR titration, mass spectra and IR spectra. Cellulose acetate/ TPESHD based strips for ammonia detection application was fabricated and studied. Image 1 • New derivatives of pure hydrazone dye (TPESHD) was successfully prepared. • The prepared compound showing high selectivity and sensitivity in to Cu+2. • The TPESHD considered as a duel functional chemosensor to heavy metal and pH. • The binding mechanism was proved by 1HNMR titration and mass spectrometry. • The application of TPESHD for monitoring of ammonia gas solution was studied. [ABSTRACT FROM AUTHOR]