Quantum Dots-Enhanced Laser-Induced Breakdown Spectroscopy for Ultrasensitive Quantification of Trace Metals in Oils

We developed a novel quantum dots-enhanced laser-induced breakdown spectroscopy (QDE-LIBS) technique for the ultrasensitive detection of trace metals in lubricating oils. By utilizing AgNC@AgAu_x core-shell quantum dots (QDs) as signal amplifiers, this strategy overcomes matrix interference and reproducibility limitations inherent in typical LIBS. Predeposition of QDs on aluminum substrates generates a strong localized electric field and charge separation via quantum confinement effects, achieving a 21.8-fold signal enhancement at Mg II 279.553 nm. The signal-to-background ratio (SBR) at Ca II 393.367 nm is 10.65-fold higher than that at typical LIBS, and the relative standard deviation (RSD) at Ca II 393.367 nm is reduced by 71.6%. Quantitative analysis demonstrates excellent linearity (R² > 0.97), with detection limits of 0.032 mg/L for Mg, 0.0656 mg/L for Ca, and 0.0882 mg/L for Ba. This method achieves exceptional sensitivity and reproducibility, with the potential for field deployment through automated sample preparation or precoated substrates, making it a promising candidate for wear metal monitoring in predictive maintenance systems.