Intrinsically fluorescent polymer nanoparticles for sensing Cu2+ in aqueous media and constructing an IMPLICATION logic gate

- Fluorescent polymer nanoparticles (PNPs) were formed by polyethyleneimine and HCHO.
- The fluorescence of PNPs was selectively and sensitively quenched by Cu2+.
- The intrinsically fluorescent PNPs were used as a probe for sensing Cu2+.
- Cysteine restored the fluorescence because it removed Cu2+ from the surface of PNPs.
- An IMPLICATION molecular logic gate was designed based on the PNPs/Cu2+/Cys system.

We have demonstrated a fluorescence approach for rapid, environment-friendly, and selective detection of Cu2+ in aqueous media using a kind of easily prepared and autofluorescent polymer nanoparticles (PNPs) as a sensor. The PNPs were synthesized by crosslinking hyperbranched polyethyleneimine (hPEI) with formaldehyde in water solution, and they emitted strong intrinsic fluorescence without the conjugation to any external fluorescent agent. The Cu2+ assay was on the basis of the principle that Cu2+ can be adsorbed on the surface of the PNPs, resulting in the fast and remarkable fluorescence quenching through electron transfer. The developed sensor was applied to the analysis of copper ions in environmental water samples with satisfactory results. Furthermore, the fluorescence of the PNPs-Cu2+ system can restore upon addition of cysteine (Cys) because of its ability to remove Cu2+ from the surface of PNPs. Based on the fluorescence “on-off-on” conversion, a reversible IMPLICATION logic gate was designed by using Cu2+ and Cys as the two inputs, and fluorescence intensity of the PNPs as the output signal.

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