How to Characterize 4-90 nm Size Gold Nanospheres with Experimental and Simulated UV-Vis and a Single SEM Image

JOSEFINA VENTRE; AGUSTINA RENNA; FRANCISCO J. IBAÑEZ

JOURNAL OF CHEMICAL EDUCATION

AMER CHEMICAL SOC

Lugar: Washington; Año: 2023 p. 1589 - 1596

0021-9584

It is crucial nowadays to predict in a fast and simple manner physical-chemical behaviors like, for instance, the size-dependent optical properties of Au nanospheres (Au NSs). The idea behind this experiment is trying to replace (as much as possible) robust and expensive microscopy techniques with UV-vis spectrophotometry and friendly simulations. Students chemically synthesized ~ 4 and ~15 nm diam. and grew larger NSs to ~32, ~50, and ~70 nm diam. using the previously obtained ~15 nm seeds. They characterize them via UV-vis spectroscopy to ultimately compare the spectra with friendly software including MiePlot, NanoHUB.org, and Amendola (Wolfram Mathematica). For Au NSs ≤ 25 nm diam., the experimental UV-vis spectra fitted very well with the Amendola algorithm to determine the size. For Au NSs > 25 nm diam., the experiment exhibited larger Au NSs than expected as noticed by the systematic red shift of the plasmon band with respect to the simulated one. A SEM image confirmed larger size Au NSs; therefore students were challenged to determine the source of discrepancy between experimental and simulated UV-vis spectra which was later attributed to the age of the Au NSs seeds. This experiment demonstrates an easy way to accurately determine the nanoparticles size while exploring and solving potential issues that students may face during the chemical synthesis and simulations.