Lignin-mediated green synthesis of functionalized gold nanoparticles via pulsed laser technique for selective colorimetric detection of lead ions in aqueous media.

A versatile green synthesis technique of pulsed laser irradiation and the sonochemical process was used for the production of functionalized gold nanoparticles (Au NPs) in the presence of lignin matrixes. In this study, the futuristic advantages of the lignin biopolymer were explored for the preparation of zero-valent Au NPs in the absence of any other reducing agents. The resulting lignin functionalized Au NPs (L-Au NPs) were characterized via high-resolution transmission electron microscopy, X-ray diffraction, UV-vis spectroscopy, and Fourier-transform infrared spectroscopy. The optimum lignin concentration can generate uniformly dispersed crystalline L-Au NPs. The optimized L-Au (1-5) NPs permit the selective colorimetric detection of heavy metal ions; thus, the L-Au (1-5) NPs demonstrated a highly selective colorimetric sensing tendency toward Pb ions within a short time interval among the various metal ions (Pb, Fe, Cu, Cr, Co, Ag, Ca, Cd, Ba, and Hg). The prominent color change of L-Au NPs from red wine to purple indicates the detection of Pb ions. This robust characteristic nature of L-Au (1-5) NPs can also detect very low concentrations of 1.8 μM in the linear range of 0.1-1 mM. Hence, the outcome of this study coincides with existing studies and indicates that L-Au (1-5) NPs can also be used as effective sensors for the rapid and selective detection of Pb ions via the colorimetric analysis using the real environmental samples.