Fenton reaction-triggered colorimetric detection of phenols in water samples using unmodified gold nanoparticles

This work demonstrates a rapid and sensitive colorimetric detection of phenols by using single-stranded DNA (ssDNA)-regulated gold nanoparticles (AuNPs) as indicators. AuNPs can be stabilized in the presence of ssDNA through electrostatic repulsion, which prevents the salt-induced aggregation of AuNPs in solution. However, hydroxyl radicals (OH) generated by the Fenton reaction can cleave the ssDNA on the nanoparticle surface into mono- or oligonucleotide fragments, disrupting AuNPs stability. Phenolic compounds are known to be capable of being degraded or oxidized by OH produced by Fenton reaction. Thus, phenols can effectively scavenge OH to avoid ssDNA cleavage, protecting AuNPs from salt-induced aggregation. The ability of phenols to scavenge OH provides a quantitative basis for phenol sensing. In this study, catechol and hydroquinone were selected as analytes and detected using the proposed ssDNA–AuNPs colorimetric probe. The detection sensitivities of the colorimetric sensor are 0.2–7.0 μM for catechol and 2.7–19 μM for hydroquinone. The proposed bioassay eliminates tedious sample pretreatment and offers favorable sensitivity and selectivity for targets in the presence of other investigated metal ions and organic molecules. The detection limits are 0.11 μM for catechol and 1.6 μM for hydroquinone, with relative standard deviations of 3.7% for catechol and 4.8% for hydroquinone. The recovery rate of catechol in real water samples ranges from 95% to 116%, confirming the application potential of the method to measure phenols in real samples.