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 generating 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.

Romanian Wild-Growing Chelidonium majus—An Emerging Approach to a Potential Antimicrobial Engineering Carrier System Based on AuNPs: In Vitro Investigation and Evaluation

“…The Raman spectrum displayed in Figure 3 indicates the presence of two peak shifts identified at 886 cm −1 and 1560 cm −1 , respectively. When gold nanoparticles are subjected to Raman analysis, certain specific shifts are expected to appear in the spectrum in the ranges of 200–400 cm −1 and 500–580 cm −1 [ 80 ]. In the present case, no spectral information could be identified in the previously mentioned intervals, but the presence in the spectrum of the two Raman shifts of significantly high intensity at 886 cm −1 and 1560 cm −1 , respectively, can most probably be attributed to the vibrational modes specific to the interactions and the strong bonds between the surfaces of the AuNPs and the phytochemicals from the greater celandine sample [ 7 ].…”