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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 (Au0–NPs<inf>CHL</inf>) and creatinine was developed for mercury (II) detection in aquatic environments using smartphone–based RGB analysis. Au0–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 Au0–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 Au0-NPs<inf>CHL</inf> (0.103 ± 0.03 nmol L−1) and 25 µL of creatinine solution (40 mg L−1) 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 Hg2+–contaminated samples for 3 min, allowing Hg2+ adsorption. Breaking the swab generated pressure differential, which, along with gravity, drove the Au0–NPs<inf>CHL</inf> to mix with creatinine. The resulting mixture migrated toward the swab tip by capillary action and reacted with adsorbed Hg2+ through metallophilic 5d10–5d10 interactions. Creatinine acted as a bridging ligand, inducing Au0–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−1 with a low LOD of 0.82 µg L−1. 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 Hg2+ contamination in environmental samples.
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Highly sensitive and selective colorimetric sensor of mercury (II) based on layer–by–layer deposition of gold/silver bimetallic nanoparticles
(2020-10-01)
Mathaweesansurn, Arjnarong
;
Vittayakorn, Naratip
;
Detsri, Ekarat
A new colorimetric sensor based on gold/silver bimetallic nanoparticles (Au–Ag BNPs) for the sensitive and selective detection of mercury (II) was developed. Gold nanoparticles (AuNPs) were synthesized by Turkevich method. The surface modification of AuNPs was modified by the layer–by–layer technique using poly(diallyl dimethylammonium chloride) which provided positively charged of AuNPs. Negatively charged silver nanoparticles (AgNPs) were synthesized by chemical reduction using poly(4–styrenesulfonic acid–co–maleic acid) as the stabilizing agent. The layer–by–layer assembly deposition technique was used to prepare Au–Ag BNPs of positively and negatively charged of AuNPs and AgNPs, respectively. The synthesized Au–Ag BNPs were characterized by a UV-visible spectrophotometer, zeta potential analyzer, FT–IR, TEM, XRD, and EDX. The Au–Ag BNPs sensor was able to detect mercury (II) in aqueous solution, visibly changing from brownish–orange to purple. The linear relationships of the UV-visible spectrometry demonstrate that the Au–Ag BNPs-based colorimetric sensor can be used for the quantitative analysis of mercury (II) in the range of 0.5–80 mg L−1, with the correlation coefficient, r2 = 0.9818. The limit of detection (LOD) of mercury (II) was found to be 0.526 + 0.001 mg L−1. The BNPs is also verified to have a good practical applicability for mercury (II) detection in the real samples.
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Novel colorimetric sensor for mercury (II) based on layer-by-layer assembly of unmodified silver triangular nanoplates
(2016-10-01)
Detsri, Ekarat
A simple layer-by-layer deposition technique was used to fabricate the multilayer thin films of unmodified silver triangular nanoplates (AgTNPs). The multilayer of AgTNPs thin films were fabricated by alternate deposition of each anionic sodium citrate stabilized AgTNPs and cationic poly(diallyldimethylammonium chloride). All prepared AgTNPs multilayer thin films were exhibited a strong plasmon band at the wavelength of 667 nm, which confirmed the formation of AgTNPs onto the substrate. The characteristics of the multilayer thin films were investigated using contact angle measurement, UV–visible spectroscopy, X-ray diffraction analysis (XRD), atomic force microscope (AFM) and field emission scanning electron microscope (FESEM). As these films are to be used as a mercury (II) colorimetric sensor, the changes in optical properties of the films were evaluated for various mercury (II) concentrations. AgTNPs assembled into thin films showed a strong color shift from blue to mauve and colorless when exposed to mercury (II). The constructed multilayer thin films exhibited excellent color changes of mercury (II) with a linear range between 0.5 and 20 ppm. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.45 ± 0.002 and 1.52 ± 0.002 ppm, respectively. The recovery values of AgTNPs multilayer thin films are satisfactory in the range of 100.1%–106.4% when applied to determining mercury (II) in water samples.

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