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Author: search.filters.author.Choengchan, NathawutSubject: search.filters.subject.Gold nanoparticles

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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
    ;
    Phunpruch, Saranya
    ;
    Prommajun, Munlika
    ;
    Srikritsadawong, Pongpichet
    ;
    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<sup>-1</sup> 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 Au<sup>0</sup> at 525 nm. The amount of 97.3 weight % of Au<sup>0</sup> was found. The spectrophotometric assay was carried out by dropping the aliquots of 100 µL of sample and 400 µL of 20 mmol L<sup>-1</sup> 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 Au<sup>o</sup> 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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    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
    ;
    Choengchan, Nathawut
    ;
    Khongkaew, Putthiporn
    ;
    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<sup>-1</sup>. The limit of detection (0.16 mg L<sup>-1</sup> 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.