Metal ion induced assembly of dipeptide attached perylenediimide for fluorometric "turn on" detection of biologically important small molecule.

A dipeptide appended perylenediimide (PDI-CFF) fluorescent molecule was designed, synthesized and characterized. Though the molecule does not dissolve in any individual solvent, it dissolves well in an organic/water mixed solvent system such as tetrahydrofuran (THF)/water. This new fluorescent molecule was self-assembled in a THF/water mixture to form both nanofibrous network structures and a nano ring structure. It has shown nanofibril morphology by the interactions with ferric ions (PDI-CFF/Fe system) with diminishing fluorescent property. Interestingly, L-ascorbic acid (LAA) interacts with the PDI-CFF/Fe system, showing turn-on fluorescence. Another interesting feature is that the minimum detection limits for Fe ions and LAA are at the sub-micromolar level of 6.2 × 10 M and 3 × 10 M, respectively. Moreover, the fluorescent (10 μM) signals can be monitored by the naked eye under hand-held UV lamp irradiation at 365 nm, and this is very convenient for the real application. In this study, the molecule offers the opportunity for processing these sequential fluorescence responses in order to fabricate a combinatorial molecular logic gate that includes NOT, AND and OR simple logic gates using chemical stimuli (ferric ions and LAA) as inputs and fluorescence emission at 536 nm as output. The detailed mechanism of interactions of Fe with PDI-CFF and LAA with the PDI-CFF/Fe system is vividly studied by using FT-IR analysis and fluorescence. Moreover, this new molecule was reusable for several times without significant loss of its activity. The construction of logic gates using biologically important molecules/ions holds future promise for the design and development of new bio-logic gates.