Development of a highly selective and sensitive colorimetric detection of Mn(II) ion in environmental water using TRPIDA_V- AuNPs: A CIELAB colour space study Sindisiwe Shange , Nontuthuko Zulu, Penuel Kubheka, Talent Makhanya, Nirmala Deenadayalu, Phumlani Mdluli Department of Chemistry, Durban University of Technology, South Africa Manganese (Mn) is well known to exist in water steadily compared to other valence states of Mn. This study was based on the study reported by He and Zhang where they developed a facile, selective and sensitive colorimetric assay for Mn(II) ions based on the anti-aggregation of unmodified silver nanoparticles. Hence, this study proposes a rapid and efficient colorimetric method for the detection of manganese ion (Mn(II)) with high selectivity and sensitivity using 3-(4-hydroxy-3-methoxyphenyl)-2,3-dihydropyrazolo [3, 4-b] indole-1(4H)-carbothioamide (TRPIDA_V) modified gold nanoparticles (TRPIDA_V-AuNPs). The TRPIDA_V-AuNPs aggregated upon introduction of 2 mg/L of Mn(II), which led to a change in colour of the dispersed TRPIDA_V-AuNPs from red to blue and a decrease of the surface plasmon absorption intensity at 520 nm. The TRPIDA_V-AuNPs aggregated between 2-10 mg/L resulting in the formation of a second peak at 655 nm. The colorimetric detection showed high selectivity to Mn(II) and was not selective to other investigated metal ions as there was no aggregation induced upon addition of 2 mg/L of other metal ions. Furthermore, only Mn(II) resulted in colour change from wine red to blue and forming a second absorption peak at 655 nm. Additionally, the colorimetric detection system yielded a detection limit of 0.00691 mg/L showing excellent sensitivity towards Mn(II). The More fills colour pattern obtained from the RGB colour coordinates presented corresponding colour patterns as the captured photographic image. The obtained XYZ values displayed similar trends as the RGB values where a rapid decrease in the X values was observed from 1-2 mg/L. The Y values increased from 0-1 mg/L and decreased significantly at 2 mg/L followed by an increase from 3-10 mg/L. The Z values increased rapidly from 0-4 mg/L then a decrease at 5 mg/L was observed followed by a rapid increase from 6-10 mg/L. It was observed that the colour difference values increased with increasing Mn(II) standard concentration. Hue decreased as the Mn(II) concentration increased and the chroma decrease significantly from 1-2 mg/L indicating the TRPIDA_V-AuNPs in the presence of Mn(II) standards solutions changed from vivid to dull as the Mn(II) increases. TRPIDA_V-AuNPs spiked with 0.5, 2, 4, 6, and 10 mg/L river and tap water Mn(II) standard solutions yielded a %Recovery between 90.42-102.45% and % RSD between 0.02-0.58% of river water. Finally, the %Recovery and %RSD for tap water samples was between 98.06-104.87% and 0.01-0.34%, respectively. These results proved the developed colorimetric sensor to be highly robust and efficient for both river and tap water samples.
P23
© The Author(s), 2023
Made with FlippingBook Learn more on our blog