Enhanced Toxic Trace Element Detection in Water Using LIBS Combined with a Femtosecond Laser-engineered Hydrophobic-hydrophilic Structured Substrate

Abstract

Laser-induced breakdown spectroscopy (LIBS) offers significant advantages in the rapid, sensitive, and environmentally friendly detection of toxic elements in water. However, its sensitivity for liquid samples remains a critical limitation, hindering broader practical applications. This work introduces a novel method combining femtosecond laser selective irradiation and chemical modification to construct a hybrid superhydrophobic and hydrophilic surface structure on an aluminum substrate, effectively forming a hydrophobic-hydrophilic enclosure. This structure facilitates the stable accumulation and uniform deposition of droplets within the hydrophilic area, significantly suppressing the "coffee ring" effect and enhancing both the concentration efficiency and detection sensitivity. Compared to traditional LIBS, the proposed method achieves limits of detection for Cr, Pb, and As at the ppb level (<3 μg/L), with determination coefficients (R²) exceeding 0.98. Furthermore, by incorporating the Partial Least Squares Regression (PLSR) model, this method further enhances the accuracy and reliability of the quantitative analysis, maintaining low root mean square errors (RMSE) in both the training and test datasets. Overall, this innovative method holds considerable potential for water quality monitoring and trace element analysis, offering a novel strategy for high-sensitivity, simultaneous multi-element detection.