Determination of dissolved organic matter based on UV-light induced reduction of ionic silver to metallic nanoparticles by humic and fulvic acids

• Photo-reduced formation of AgNPs mediated by DOM.
• Visual assay of DOM without instrumental detectors.
• DOM is determined in the visible region irrespectively of structure and origin.

We describe a novel solution-based method for the determination of dissolved organic matter (DOM) relying on the formation of silver nanoparticles (AgNPs) via photo-stimulated reduction of silver ions by humic and fulvic acids. The method is based on natural driven formation of nanoscale materials yielding a direct relationship between DOM concentration and AgNPs formation. The aqueous dispersion of the formed AgNPs show strong and uniform UV–Vis absorption bands between 450 and 550 nm irrespectively of DOM nature and properties (i.e. humic or fulvic acids). The ensuing chromatic shift accompanying the appearance of the new absorption bands is easily conceivable by a simple spectrophotometer and the bare eye, holding great promise for the on-site, instrumental-free screening of DOM levels. Under the optimum experimental conditions the determination of DOM was successfully demonstrated to various water samples with high sensitivity (<1.0 mg L−1), satisfactory recoveries (87.5–123.5%) and reproducibility (5.87–6.73%).

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