Abstract
Herein, we reported Tara gum (TG), mediated synthesis of stable and dispersed gold nanoparticles (AuNPs). TG was applied for the first time as the reducing/capping agent for AuNPs synthesis, through heating with gold salt, stirring at 80 °C for 1 h under NaOH support. Reddish color AuNPs solution, exhibiting absorption maximum at 521 nm, with an average particle size of 10.5 ± 1.8 nm, was obtained. The synthesized TG-AuNPs was characterized using various equipment, including TEM, FESEM, ATR-FTIR, Raman spectroscopy, XRD, TGA/DTG, DLS/zeta potential and XPS, which confirmed the dispersal of small-sized AuNPs in TG polymeric structure. TG-AuNPs was further modified with Quercetin (QT), a notable polyphenolic compound, to realize TG-AuNPs-QT nanoparticles which was applied as optical nanoprobe for Iodide ion (I(-)) detection. The addition of silver ion [Ag(+)], to the TG-AuNPs-QT probe results in color change, from red to yellow, followed with an absorption spectra blue shift from 521 nm to 420 nm, owing to QT mediated in-situ reduction of Ag(+) to its nanoparticles, which was deposited on pre-formed AuNPs, yielding Au@Ag nanostructure. However, when I(-) (various concentrations), were pre-mixed with an optimized Ag(+) concentration, reverse color and absorption spectra perturbations were observed, which is attributed to the high binding interaction between Ag(+) and I(-), forming AgI complex in solution. At the optimal I(-) detection conditions, the analytical response applied, (A(o)-A(i))@405 nm, was linear with I- concentrations from 1.0 to 65.0 μM, with a limit of detection/quantification (LOD/LOQ) of 250 nM and 0.82 μM, respectively. Practical applications of the probe was demonstrated on water and diverse food samples, with satisfactory accuracy.