Multivariate calibration of nanoparticle-enhanced LIBS (NELIBS) for gold nanoparticle quantification

Accurate quantification of gold nanoparticles (AuNPs) is important for applications in nanotechnology, medicine, and materials research. This study investigates the quantification and plasma characterization of AuNPs using nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) combined with multivariate calibration. Ten different concentrations of 20 nm colloidal AuNPs were deposited on titanium (Ti) and aluminum (Al) substrates and analyzed using 532 nm and 1064 nm Nd:YAG laser excitation. Partial least squares regression (PLSR) was employed to establish calibration models for AuNP concentration prediction. The optimized PLSR model at 532 nm exhibited better predictive performance, with a coefficient of determination ( = 0.99) and a relative error (RE) of less than 5%, compared to approximately 13% at 1064 nm. The method achieved a limit of detection (LOD) of approximately 2.5 ppm for AuNP concentration, confirming its high analytical sensitivity and potential for precise nanoparticle quantification. Plasma parameters, including electron temperature ( ), electron density ( ), and emission intensity for the Ti substrate, were calculated and discussed to compare LIBS and NELIBS at various AuNP concentrations. The results revealed that, at the optimal AuNP concentration, 1064 nm excitation produced stronger spectral enhancement, which may be associated with collective optical effects and more efficient laser–sample coupling under NELIBS conditions. These findings demonstrate the potential of NELIBS coupled with multivariate analysis for accurate nanoparticle quantification and provide new insights into the influence of laser wavelength and substrate conductivity on plasma dynamics.