Optimized Colorimetric Detection of Chromium Ions (Cr3+) Using Black Garlic-Ag Nanoparticles

Abstract

In this study, AgNPs were synthesized using black garlic (BG) extract and used for precise and sensitive colorimetric detection of chromium (Cr3+) ions in solution. The nanoparticles (BG-AgNPs) was characterised by UV-Visible septroscopy, FTIR, SEM, TEM and XPS analysis. The UV-visible absorbance peak showed at 411 nm. The pattern of X-ray diffraction (XRD) confirmed a face-centered cubic (FCC) structure of the nanoparticles. The SEM images displayed a fusiform (spindle-shaped) morphology of the AgNPs. Transmission electron micrograph (TEM) presents the sphere-shaped nature of the nanoparticles having a mean diameter of 16.02 ± 1.75 nm. The addition of Cr3+ ions turned the brownish BG-AgNPs solution colourless. The sensor displayed a linear response to Cr3+ concentrations between 2 nM - 20 nM with a limit of detection (LoD) observed 0.07 nM. Optimal sensor performance was achieved at pH 7 and a temperature of 45°C. Selectivity tests confirmed minimal interference from other metal ions. These indicate that the developed nanosensor is exceptionally efficient and ultrasentive at precisely detecting low concentrations of Cr3+ ions in environmental applications. A computational study with one of the most abundant compounds during the early stages of the aging process of black garlic formation, the γ-glutamyl-S-allylmercaptocysteine (GSAMC), showed a binding energy of -6.67 kcal/mol for the formation of GSAMC-AgNPs and -8.82 kcal/mol for the formation of GSAMC-AgNPs-Cr complex.