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Author: search.filters.author.Lerdpiriyaskulkij, NateeSubject: search.filters.subject.Mercury (II)

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    Item type:Publication,
    Smartphone-based disposable cotton-swab sensor loaded with creatinine/Cu–chlorophyllin–stabilized AuNPs for ultrasensitive RGB colorimetric detection of mercury (II) ions in aquatic environments
    (2026-05-01)
    Lerdpiriyaskulkij, Natee
    ;
    Detsri, Ekarat
    ;
    Teerasong, Saowapak
    ;
    Chansai, Sarayute
    ;
    Mathaweesansurn, Arjnarong
    A simple, rapid, selective, and sensitive colorimetric sensor based on a disposable cotton swab loaded with Au nanoparticle–modified Cu-chlorophyllin (Au<sup>0</sup>–NPs<inf>CHL</inf>) and creatinine was developed for mercury (II) detection in aquatic environments using smartphone–based RGB analysis. Au<sup>0</sup>–NPs<inf>CHL</inf> were synthesized by ultrasonic-assisted chemical reduction, employing Cu-chlorophyllin as a stabilizing and NaBH<inf>4</inf> as a reducing agent. A vivid red Au<sup>0</sup>–NPs<inf>CHL</inf> colloidal (7.96 ± 0.29 nm) with a sharp SPR peak at 515 nm was successfully obtained. An aliquot of 75 µL of Au<sup>0</sup>-NPs<inf>CHL</inf> (0.103 ± 0.03 nmol L<sup>−1</sup>) and 25 µL of creatinine solution (40 mg L<sup>−1</sup>) were sequentially loaded into an 8.0 × 0.5 cm cotton swab, separated by a 0.5 cm air gap. Detection began by immersing the swab into Hg<sup>2+</sup>–contaminated samples for 3 min, allowing Hg<sup>2+</sup> adsorption. Breaking the swab generated pressure differential, which, along with gravity, drove the Au<sup>0</sup>–NPs<inf>CHL</inf> to mix with creatinine. The resulting mixture migrated toward the swab tip by capillary action and reacted with adsorbed Hg<sup>2+</sup> through metallophilic 5d<sup>10</sup>–5d<sup>10</sup> interactions. Creatinine acted as a bridging ligand, inducing Au<sup>0</sup>–NPs<inf>CHL</inf> aggregation and shifting the SPR to 620 nm, causing a visible red-to-blue transition. This sensor enables rapid and visual detection and quantitative evaluation via smartphone RGB analysis. The system demonstrated excellent linearity from 1 to 100 µg L<sup>−1</sup> with a low LOD of 0.82 µg L<sup>−1</sup>. Recoveries of 97.6–101.8 % confirmed high accuracy and minimal matrix interference. The disposable cotton swab RGB sensor provides a rapid, portable, and practical tool for on-site primary assessment of Hg<sup>2+</sup> contamination in environmental samples.