Aspartic acid functionalized water-soluble perylene diimide as “Off–On” fluorescent sensor for selective detection Cu2+ and ATP

Aspartic functionalized water-soluble perylene diimide, N , N ′-di(2-succinic acid)-perylene-3,4,9,10-tetracarboxylic diimide (PASP) has two absorbance maximums at 527 and 498   nm ( ε   ≈   1.7   ×   10 4   L   cm −1   mol −1 ) and two emission peaks at 547 and 587   nm respectively. Emission intensities decrease with the increase of PASP concentrations in 20–100   μM ranges. Spectral titrations demonstrate that each PASP can coordinate to two Cu 2+ ions in the absence of HEPES buffer. Its stability constant is estimated to be about 1.0   ×   10 12   L 2   mol −2 at pH 7.20 and its coordinate stoichiometry increased to 7.5 in the same pH in the presence of HEPES buffer. The emission of PASP will be completely quenched upon formation of Cu 2+ complex. The lowest “turn-off” fluorescence detection limit was calculated to be 0.3   μM Cu 2+ . PASP–Cu solution was used as a “turn-on” fluorescence biosensor to detect ATP. The sensitivity towards ATP is 0.3   μM in 50   mM HEPES buffer at pH 7.20, which is one of the most sensitive fluorescence sensors.