Synthesis of conjugated silver nanoparticles of 18β-glycyrrhetinic acid peptide conjugate (GAP) as a colorimetric probe for barium ions

Abstract

In this study, we present a direct colorimetric technique for the sensitive and specific detection of Ba²⁺ ions in laboratory tap and river water utilizing functionalized 18β-glycyrrhetinic acid peptide silver nanoparticles (GAP-AgNPs). Sodium hydroxide solution was used to carry out chemical reduction during the synthesis of GAP-AgNPs. Several spectroscopic methods, including UV-visible, zetasizer, FTIR, SEM, AFM, and XRD, were used to characterize the GAP-AgNPs. The GAP-AgNPs were found to be extremely stable at high temperatures, and a variety of electrolyte concentrations and pH values. The GAP-AgNPs were selective for Ba²⁺ compared to other metal ions (Na⁺, Mg²⁺, Al³⁺, Ca²⁺, Co²⁺, Hg²⁺, Mn²⁺, Ni²⁺, Fe²⁺, Cr³⁺, Cu²⁺, Fe³⁺, Zn²⁺, and Ba²⁺) leading to a noticeable color change. The addition of barium significantly decreases the absorption intensity and shifts the wavelength toward a red shift of the nanoparticles along with the color change to red from yellow. When competing metal ions were present, it was discovered that they were extremely selective for the Ba²⁺ ion. The nanoparticles showed sensitivity towards Ba²⁺ over a wide range of concentrations with a limit of detection of 0.42 μM. The findings of this study reveal the GAP-AgNPs as a selective, sensitive, and easy sensing probe for Ba²⁺ in human blood plasma, river water, and laboratory tap water.