Synthesis of Quercetin Functionalized Silver Nanoparticles and Their Application for the Colorimetric Detection of L‐Cysteine in Biologically Complex Fluids

Abstract In the present manuscript authors report an eco‐friendly, simple, and cost‐effective one‐pot synthesis of quercetin functionalized silver nanoparticles (Q‐AgNPs). The synthesized Q‐AgNPs exhibited surface plasmonic resonance absorption band at 418 nm which confirmed the synthesis. The synthesized Q‐AgNPs were further characterized by X‐ray diffraction which confirmed the crystalline structure of Q‐AgNPs. FTIR analysis of Q‐AgNPs was performed to find out the functional groups present on Q‐AgNPs. The distribution, size, and morphology of Q‐AgNPs were determined through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS) analysis. SEM, TEM, and DLS analysis revealed that synthesised nanoparticles were spherical in morphology with an average size of 40 nm. Furthermore, the synthesised Q‐AgNPs were observed to selectively sense cysteine in water, urine, and foetal bovine serum with detection limit of 21.1 nM, 86 nM, and 230 nM respectively. The SEM, TEM, and DLS analysis clearly indicated the aggregation of Q‐AgNPs in the presence of l‐cysteine particles as compared to the control Q‐AgNPs (without l‐cysteine). The findings revealed that synthesized Q‐AgNPs can be utilized to detect low concentration of cysteine in water and biological complex fluids without any requirement of sophisticated instrumentation.