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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
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Detsri, Ekarat
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Teerasong, Saowapak
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Chansai, Sarayute
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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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Picomolar Dopamine Detection using Colloidal Surface-Enhanced Raman Scattering Based on Benzene-Dithiol–Linked Gold Nanoparticles in Solution
(2026-04-01)
Sucharitakul, Waraporn
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Danvirutai, Pobporn
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Pinlaor, Somchai
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Piyawattanametha, Wibool
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Srichan, Chavis
Sensitive detection of dopamine at ultralow concentrations is essential for the development of advanced chemical and neurochemical sensing technologies. Surface-enhanced Raman scattering (SERS) offers molecular specificity and high sensitivity, but its analytical reliability is often limited by poor signal reproducibility arising from uncontrolled nanoparticle aggregation. In this work, we report a solvent-based colloidal SERS platform for picomolar dopamine detection using benzene-1,4-dithiol (BDT)–linked gold nanoparticles (AuNPs). BDT serves as a molecular linker that defines sub-nanometer plasmonic nanogaps and simultaneously acts as an intrinsic Raman reference. Dopamine molecules introduced in dilute solution are efficiently sampled within these nanogaps through noncovalent interactions, resulting in strong and reproducible SERS enhancement. The proposed platform demonstrates a detection limit in the picomolar range, a wide linear dynamic response, and excellent signal stability without the use of biological or artificial matrices. This study presents a solvent-based SERS strategy for quantitative liquid-phase dopamine detection in aqueous environments, offering a foundation for further development in sensor calibration and integration with biological matrices.
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Ultrasonic-driven chemical reduction synthesis of alizarin complexone-modified gold nanoparticles for dual-signal colorimetric and fluorometric sensing of histamine in seafood products
(2024-12-01)
Phoungsiri, Ampika
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Lerdpiriyaskulkij, Natee
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Mathaweesansurn, Arjnarong
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Detsri, Ekarat
Alizarin complexone-modified gold nanoparticles (Au0-NPs<inf>ALz</inf>) were synthesized using a proposed ultrasonic irradiation-assisted chemical reduction method. Ultrasonic irradiation powers, reaction time and alizarin complexone concentration had been proven to be the main parameters for controlling the nucleation and growth of Au0-NPs<inf>ALz</inf>. In the synthesized ultrasonic irradiation-assisted chemical reduction conditions, Au0-NPs<inf>ALz</inf> had a spherical oriented morphology with a uniform size of 17.84 ± 1.37 nm and are shiny red with a surface plasmon resonance (SPR) of 535 nm. A rapid colorimetric and fluorometric dual-mode detection strategy for selective detection of histamine in seafood was developed based on the self-assembly of Au0-NPs<inf>ALz</inf>-Ni (II) complexes. Ni (II) can capture the histamine molecules close to Au0-NPs<inf>ALz</inf> surfaces, making changes in the colorimetric and fluorometric responses of the solution. The quantitative analysis of histamine was realized through the variation of dual-signal colorimetric and fluorometric responses. Such Au0-NPs<inf>ALz</inf> sensor offered good detection sensitivity for histamine with a detection limit (LOD) of 59.32 μmol L−1 and 116.20 μmol L−1 and wide linear response within the range of 10–10000 μmol L−1 (R2 = 0.9952) and 100–5000 μmol L−1 (R2 = 0.9947) for colorimetric and fluorometric measurement, respectively. Recoveries ranging from 94.99 to 103.29 % and 97.67–106.88 % for colorimetric and fluorometric assay were obtained, showing low levels of matrix effects. Particularly, the results of the dual-mode sensor were also validated by comparing with the HPLC method for improving the assay accuracy and dependability. Ultimately, the developed Au0-NPs<inf>ALz</inf> colorimetric and fluorometric probe performs excellently in practical applications, with promising results for detecting histamine in seafood products.
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A new colorimetric method for determination of formaldehyde in sea food based on anti-aggregation of gold nanoparticles
(2022-12-01)
Mathaweesansurn, Arjnarong
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Detsri, Ekarat
A new colorimetric method based on anti-aggregation of gold nanoparticles (AuNPs) in the presence of melamine for sensitive and selective determination of formaldehyde was developed. The citrate capped AuNPs was synthesized by Turkevich method. A certain concentration of melamine is responsible for color change of AuNPs from red to purple. The surface plasmon resonance peak was shifted from 520 to 640 nm. In the presence of formaldehyde, the reaction between melamine and formaldehyde to form methylol melamine was occurred, which resulted in the decreasing of aggregation of AuNPs. Based on the anti-aggregation mechanism, formaldehyde can be detected by observing the color change of AuNPs solution containing melamine, which was monitored by UV–visible spectrophotometer. Calibration curve plotted between absorbance ratio (A640/A520) and formaldehyde concentration was made with linearity of 0 – 2000 µg L−1. The limit of detection and the limit of quantitation were found at 26.0 µg L−1 and 88.0 µg L−1, respectively. The method also provided high accuracy (%recovery in range 97.3 – 104%) and high precision (%RSD < 5.6).
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Preparation of gold nanoparticles-bacterial cellulose nanopaper and its application as 2D-microcuvette for spectrophotometric determination of hydrogen peroxide
(2021-01-01)
Lert-Itthiporn, Aurachat
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Phunpruch, Saranya
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Prommajun, Munlika
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Srikritsadawong, Pongpichet
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Choengchan, Nathawut
This work presents a new method development using the gold nanoparticles (AuNPs)-bacterial cellulose (BC) nanopaper for the spectrophotometric determination of hydrogen peroxide (H<inf>2</inf>O<inf>2</inf>). The AuNPs were embedded in the BC nanopaper, where the nanopaper played two roles as both the reducing agent and the template for the as-prepared AuNPs. The preparation process was started by putting the wet bare BC nanopaper (Ø 30 mm and 3 mm thickness) into 0.75 mmol L-1 HAuCl<inf>4</inf> (25.0 mL). This solution was vigorously and continuously stirred for 60 min at 90ºC. After the embedding process, color of the nanopaper was changed from milky-white to wine-red. The AuNPs-BC nanopaper was characterized by UV-visible spectrophotometer, FE-SEM and EDS. Absorption spectrum of the nanopaper showed the characteristic peak of Au0 at 525 nm. The amount of 97.3 weight % of Au0 was found. The spectrophotometric assay was carried out by dropping the aliquots of 100 µL of sample and 400 µL of 20 mmol L-1 citrate buffer (pH 6.0) onto the AuNPs-BC nanopaper. The nanopaper was then kept in a plastic back for 10 min. In the presence of H<inf>2</inf>O<inf>2</inf>, the wine-red color of the AuNPs-BC nanopaper was turned to pale red accordingly to reduction of Auo to Au(III) by H<inf>2</inf>O<inf>2</inf>. Decreasing in the absorbance of the nanopaper at 525 nm was monitored using UV-visible spectrophotometer. Detection limit (y<inf>B</inf> + 3S<inf>B</inf>) of 0.79 % (v/v) was observed and this value was enough sensitive for the determination of H<inf>2</inf>O<inf>2</inf> in wound cleaner and hair dye samples. The H<inf>2</inf>O<inf>2</inf> contents in all samples were agreed well with the label values. Good analytical recovery (88.8 to 97.2 %) with high precision (RSD: 3.3 %) were obtained. These results confirmed that the as-prepared nanopaper was successfully synthesized and was effectively applied as the two dimensional (2D)-microcuvette for the spectrophotometric determination of H<inf>2</inf>O<inf>2</inf> in real samples.
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Controlled reversible assembly of gold nanoparticles as a new colorimetric and sensitive detection of glucose-6-phosphate dehydrogenase deficiency
(2020-07-25)
Boonyuen, Usa
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Praoparotai, Aun
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Chamchoy, Kamonwan
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Swangsri, Thitiluck
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Warakulwit, Chompunuch
Recently, several studies have examined possible applications of nanoparticles for the development of electronic and optical sensors. The plasmon absorbance of gold nanoparticles has been used extensively to study biomolecular processes, including nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate-dependent enzymatic reactions. In this report, we describe the development of gold nanoparticles as a new colorimetric and sensitive detection method of glucose-6-phosphate dehydrogenase deficiency by means of controlled reversible assembly of gold nanoparticles. 3-nm polyvinylpyrrolidone/N,N′-dimethylaminopyridine-stabilized gold nanoparticles were synthesized, characterized and applied for an in vitro activity assay of 11 recombinant human glucose-6-phosphate dehydrogenase variants. Differences in the activity of the glucose-6-phosphate dehydrogenase variants from different deficiency classes were readily detected using the synthesized gold nanoparticles. The developed method can be easily distinguished with color change by naked eye for the detection of glucose-6-phosphate dehydrogenase deficiency. Moreover, we are the first to propose the segregation mechanism of polyvinylpyrrolidone/N,N′-dimethylaminopyridine-stabilized gold nanoparticles by reduced nicotinamide adenine dinucleotide phosphate. The method enables visual detection of glucose-6-phosphate dehydrogenase deficiency, which could be further developed for diagnostic testing of glucose-6-phosphate dehydrogenase deficiency.
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Low-cost synthesis of gold nanoparticles from reused traditional gold leaf and its application for sensitive and selective colorimetric sensing of creatinine in urine
(2020-01-01)
Mathaweesansurn, Arjnarong
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Choengchan, Nathawut
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Khongkaew, Putthiporn
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Phechkrajang, Chutima M.
Background: Gold nanoparticles (Au NPs) are normally prepared using standard gold (III) trichloride which is much expensive and irritant. This work is aimed at demonstrating simple and low-cost synthesis of Au NPs from the reused traditional gold leaf which is cost-free and less toxic. Methods: The reused gold leaf was donated by the local temple. It was digested and used as the precursor for the preparation of the Au NPs by Turkevich method. Poly (vinyl alcohol) (PVA) was em-ployed as a stabilizer. The as-prepared Au NPs were applied for the colorimetric determination of creatinine in urine without any sample pretreatment. Results: Long-term stability of the gold colloids was achieved for at least 3 months. Morphology and purity of the as-prepared Au NPs were the same as the ones prepared from standard gold (III) salt and standard gold foil. Colorimetric response of the Au NPs was linear to the standard creatinine up to 200 mg L-1. The limit of detection (0.16 mg L-1 or 1.41 µM) was enough sensitive for urinary cre-atinine detection in patients with kidney disease. Good recoveries (97-108%) and fast analysis time (3 min) were achieved. The developed method was successfully validated against the HPLC method. Conclusion: Facile and cost-effective synthesis of the Au NPs from the reused traditional gold leaf, was accomplished. The as-prepared Au NPs were successfully applied for the determination of urinary creatinine with high sensitivity and selectivity.

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