Highly selective sub-micromolar level colorimetric sensor for lanthanum detection based on L-tyrosine functionalized silver nanoparticles

A simple, efficient and cost effective protocol was established for the synthesis of silver nanoparticles (AgNPs) using L-Tyrosine as capping agent in aqueous medium. Ultraviolet-visible (UV-vis) spectroscopy was used to observe the localized surface plasmon resonance (LSPR) band of L-Tyrosine derived silver nanoparticles (TYR-AgNPs) prepared under optimized conditions. Fourier-transform infrared (FTIR) spectroscopy was employed to obtain the interaction between L-tyrosine and AgNPs. The particle size and morphological features were affirmed through dynamic light scattering (DLS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Crystalline planes of TYR-AgNPs were verified through X-ray diffraction (XRD) technique. The TYR-AgNPs possessed spherical geometry with the size range of 14.5 - 18.2 nm and average size of 18 nm. These TYR-AgNPs were acknowledged as colorimetric sensor for trace level detection of lanthanum (La3+) by UV-vis spectroscopy for the first time. As-developed colorimetric La3+ nanosensor worked linearly in the range of 0.5-22.5 mu M with R2 value of 0.998 and limit of detection (LOD) equal to 0.06 mu M. Negligible interference was noticed in the presence of several monovalent, divalent, trivalent, tetravalent some lanthanides cations, and associated anions. The developed sensor was employed successfully for the determination of La3+ in geological (rock) and tap water samples.