Simultaneous SERS detection using hexagonal hollow Au-Ag nanoparticles with near infrared plasmon

Hexagonal hollow Au-Ag nanostructures were synthesized using galvanic replacement mechanism with silver nanoparticles as sacrificial templates. The cavity dimension in the hollow structures was found to be dependent on the amount of HAuCl4 used. X-ray photoelectron spectroscopy was used to understand the replacement mechanism took place between Ag and Au and Ag: Au ratio was found to be 88.80:11.20 in the optimum case. The surface enhanced Raman scattering (SERS) activity of these hollow nanostructures has been investigated using three probe molecules viz., crystal violet (CV), malachite green (MG) and nile blue chloride (NBC) under two laser excitation sources viz., visible (514.4 nm) and near infrared (784.8 nm). The multivariate analysis of the SERS spectra obtained with different probe molecules was done using principal component analysis (PCA). The SERS spectral data collected were transformed orthogonally to a lower dimension and the spectral information containing maximum variance of the original data was represented as principal components in the new dimension. It was found that the first two principal components represented significant spectral information, and the percentages of variance obtained were 63.43 and 32.22 %, respectively. Segregations of the probe molecules were evident in the score plots drawn in the transformed dimension. The correlation between Raman shifts in the SERS spectra and the principal components was obtained from loading plots. The results suggest that Au-Ag hollow nanostructures can be used as a reliable substrate for multiplexed SERS detection in various applications.

Automated summary

Hexagonal hollow Au-Ag nanostructures were synthesized using galvanic replacement mechanism with silver nanoparticles as sacrificial templates. The cavity dimension in the hollow structures was found to be dependent on the amount of HAuCl4 used, and the optimal Ag: Au ratio was determined. The SERS activity of these hollow nanostructures was investigated using PCA, revealing them as reliable substrates for multiplexed SERS detection.