Raman Spectroscopy Analysis of the Morphology of Gold Nanoparticles Produced by Laser Ablation in Aqueous Proteinogenic Amino Acid for the Detection of Mercury in Water

Abstract

The objective of the research was to analyze by Raman spectroscopy the morphology of gold nanoparticles generated by laser ablation in L-Cysteine of purity ≥ 97% dissolved in ultrapure water for the detection by color change of mercury dissolved in water. Three samples of 10 ml of ultrapure water were prepared with aggregation of 10 ul of L-Cysteine with concentrations of 1, 10 and 20 mM; the generation of the gold nanoparticles was by laser ablation with a wavelength λ = 1064 nm, energy of 60.28 mJ/p located at 30 cm from the convex lens generat - ing ablation at 10 cm on a gold plate of dimensions 10×15 mm with thickness of 1 mm, for 30 min. The gold nanoparticles generated in these aqueous environments were characterized by Raman spectroscopy using a laser with a sensitivity of 785 nm with Raman Shift analysis range 860–3200 cm -1 and controlled power at 499 mW. The nanoparticles presented maximum peak resonance around Raman Shift 1164.96 cm -1 and 1288.06 cm -1 . With the AuNPs + L-Cysteine sample with concentration of 10 mM, the author proceeded to the detection of Hg 2+ prepared in 20 μl of ultrapure water at concentrations of 0.1, 5 and 10 µM; when adding 100 μl of AuNPs + L-Cysteine two peak absorbance spectra were obtained with different amplitudes observed by UV–Vis spectroscopy, indicating that Hg 2+ decreased the repulsion of the negatively charged AuNPs, generating the visible color change for the three concentrations of Hg 2+ with 25 minutes of agitation, turning intense purple for 10 µM of Hg 2+ ; enabling the detection of mercury in water.