Poly(p-phenylenediamine) fluorescent nanosphere: A ultra-sensitive fluorescent probe for caffeine

•PpPD nanosphere is prepared by a simple process and can be used as a fluorescent probe for caffeine.•The detective limit (2 × 10−11 M) of this detection system is far below the documents reported.•This fluorescent probe shows excellent selectivity, specificity, anti-interference ability.•The mechanism of fluorescence synergistic effect is explained by theoretical calculations.

A ultra-sensitive fluorescent detection system (ppb level) for caffeine is formed by easily prepared poly(p-phenylenediamine) (PpPD) conducting polymer nanospheres. As a fluorescent sensing platform, the PpPD showed excellent selectivity, specificity and anti-interference ability. The dramatic quenching behavior in PL intensity of PpPD nanospheres when caffeine is added can be attributed to the fluorescence resonance energy transfer (FRET) procedure between PpPD and caffeine. This detection system has good stability and the probe can be applied in gentle condition. What's more, the working mechanism is also investigated by generalized gradient approximation (GGA) of density functional theory (DFT).

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