Simple colorimetric detection of Cu2+ in water and alcoholic beverages based on D-penicillamine-mediated laccase-like activity of PDA/MnOx nanoparticles.

Copper ion (Cu2+) is prevalent heavy metal ion pollutant in water and alcoholic beverages, excess intake would cause various diseases. Thus, accurate and sensitive detection of Cu2+ is essential for human health. This work presented a simple colorimetric assay for Cu2+ detection leveraging the laccase-like activity of PDA/MnOx nanoparticles. The excellent laccase-like activity of PDA/MnOx NPs derived from superoxide anion radical and oxygen vacancy. Since D-penicillamine (DPA) acted as etchant of MnOx NPs and chelator of Cu2+, colorimetric detection of Cu2+ was achieved based on DPA-mediated laccase-like activity of PDA/MnOx NPs. This assay exhibited wide detection range (0.5-100 μM), low detection limit (61 nM) and good selectivity, and was successfully applied for detecting Cu2+ in water and alcoholic beverages. Integrating with smartphone, instrument-free and on-site analysis can be achieved. The method provided a novel strategy for designing nanozyme-based colorimetric sensor for Cu2+, and showed substantial potential in beverage safety monitoring.