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

Area of Science:

• Analytical Chemistry
• Materials Science
• Spectroscopy

Background:

• Laser-induced breakdown spectroscopy (LIBS) faces challenges with matrix interference and reproducibility in lubricating oil analysis.
• Ultrasensitive detection of trace metals is crucial for effective wear metal monitoring in predictive maintenance.

Purpose of the Study:

• To develop a novel quantum dots-enhanced laser-induced breakdown spectroscopy (QDE-LIBS) technique for ultrasensitive trace metal detection in lubricating oils.
• To overcome the limitations of traditional LIBS methods in terms of signal enhancement and reproducibility.

Main Methods:

• Utilized AgNC@AgAux core-shell quantum dots (QDs) as signal amplifiers on aluminum substrates.
• Leveraged quantum confinement effects to generate localized electric fields and charge separation.
• Employed QDE-LIBS for the analysis of trace metals (Mg, Ca, Ba) in lubricating oil samples.

Main Results:

• Achieved a 21.8-fold signal enhancement for Mg II 279.553 nm due to QD predeposition.
• Demonstrated a 10.65-fold higher signal-to-background ratio (SBR) for Ca II 393.367 nm compared to typical LIBS.
• Reduced the relative standard deviation (RSD) by 71.6% for Ca II 393.367 nm, indicating improved reproducibility.
• Obtained excellent linearity (R² > 0.97) with low detection limits (0.032 mg/L for Mg, 0.0656 mg/L for Ca, 0.0882 mg/L for Ba).

Conclusions:

• The QDE-LIBS technique offers exceptional sensitivity and reproducibility for trace metal analysis in lubricating oils.
• This method holds significant potential for real-time wear metal monitoring in predictive maintenance systems.
• The use of precoated substrates or automated sample preparation could facilitate field deployment.