Green synthesis of perylene diimide-based nanodots for carbon dioxide sensing, antibacterial activity prediction and bacterial discrimination

Abstract Perylene diimides (PDIs) derivative was prepared by hydrothermal treatment of perylene dianhydride (PTCDA) and ethylenediamine branched polyethylenimine (PEI) in the absence of toxic solvent and catalyst. The resulting PDI-PEI nanodots emit weak fluorescence due to the photoinduced electron transfer (PET) process from alkylamine units to PDI fluorophore. In acidic pH environment or in the presence of dissolved CO2, the PET effect can be eliminated to trigger the fluorescent “turn-on” response of the PDI-PEI nanodots. This chemosensor exhibits CO2 concentration-dependent fluorescence response and can be utilized to detect the dissolved CO2. This chemosensor also exhibits fluorescence reversibility for the dissolved CO2 by purging the system with CO2 and degassing with N2 alternatively. Upon incubation with different bacteria and centrifugation of the co-cultured bacterial suspensions, the PDI-PEI nanodots can be used to predict their antibacterial properties by observing the color changes of the collected bacterial cakes via naked eye. In addition, the co-cultured bacterial suspensions containing Gram-positive bacteria aggregate and form purple precipitates. The PDI-PEI nanodots can also be used to distinguish Gram-positive bacteria by observing the aggregation and sedimentation phenomenon on the co-cultured bacterial suspensions via naked eye.