Elemental analysis of liquid samples by nanoparticle-enhanced laser-induced breakdown spectroscopy: using ordered nano-arrays with a tunable nanoparticle size and inter-particle distance

Abstract

Determining elements in liquid samples through Laser-Induced Breakdown Spectroscopy (LIBS) holds great potential for various applications in fields like biomedicine and the environment. Despite this, achieving optimal performance for ultra-low concentration trace detection while keeping sample preparation fast and simple continues to be a challenge. Nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) can significantly enhance the signal intensity without additional devices, but its enhancement is affected by the size, inter-particle distance and distribution uniformity of nanoparticles (NPs). In this work, we present a large-area, highly homogeneous ordered nano-array substrate with a tunable nanoparticle size and inter-particle distance and use it for NELIBS analysis of Pb and Cr in liquid samples. Pb I 405.78 nm and Cr I 425.43 nm were selected as the analytical lines, the maximum NELIBS enhancement was achieved when the inter-particle distance was 25 nm, and the intensity of the Pb and Cr spectral lines was increased by 11.3 and 8.7 times, respectively. The relative standard deviations (RSDs) of the intensities of the Pb and Cr spectral lines obtained from repeated measurements using ordered nano-array substrates of the same and different manufacturing batches were in the range of 5.7–7.7%, and the determination coefficients (R²) of the calibration curves obtained were all above 0.99. We demonstrate a robust substrate with a reproducible fabrication process, well-controlled surface distribution of NPs, precisely tunable size and inter-particle distance of NPs, thereby generating an excellent and reproducible signal enhancement, and a long shelf lifetime.