Smartphone-assisted measurement of trace monuron using a fluorescent sensor of polypyrrole-decorated magnetite and...

A nanocomposite probe was developed and utilized for the quantitative analysis of the carcinogenic herbicide monuron in food products. The probe consisted of nitrogen-doped graphene quantum dots (N-GQDs) and polypyrrole-decorated magnetite nanoparticles (Fe₃O₄@PPy) embedded in a molecularly imprinted polymer (Fe₃O₄@PPy/N-GQD/MIP). The properties of the fabricated nanoprobe were investigated and the analysis condition was optimized by measuring fluorescence quenching when monuron rebound with the specific cavities on the probe. The fluorescence intensity of the nanoprobe exhibited a linear response from 0.40 to 25.0 μg L^-1 with a coefficient of determination of 0.9917. The nanoprobe was used to determine monuron in tea, vegetables and fruit juice, achieving recoveries between 93.8 % and 103.6 % with RSDs <5 %. Additionally, the nanocomposite probe was coupled with a smartphone in a portable system for on-site application. The smartphone-assisted method exhibited linearity from 1.0 to 20.0 μg L^-1. The determination of spiked samples using fluorescence spectrophotometry and the smartphone-assisted method exhibited good agreement with the HPLC-UV method. The developed nanoprobe exhibited excellent sensitivity, selectivity and rapidity. Moreover, the developed nanoprobe has the advantages of economy, environmental friendliness, simplicity and convenience.