Solid substrate assisted enhanced laser induced breakdown spectroscopy for metal element analysis in aqueous...

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Materials Science

Background:

• Direct underwater laser-induced breakdown spectroscopy (LIBS) suffers from plasma quenching in dense water media, leading to signal interference.
• Challenges include strong background radiation and weak, broadened spectral lines for metal element detection in liquids.
• Existing methods often require complex sample pre-treatment, limiting in situ applications.

Purpose of the Study:

• To introduce a simple, substrate-assisted method for improving underwater LIBS signal detection.
• To investigate the breakdown characteristics and spectral enhancement mechanisms of various solid substrates.
• To assess the potential for in situ marine applications with enhanced sensitivity and low power consumption.

Main Methods:

• Employed a solid substrate-assisted approach for underwater LIBS, requiring no sample pre-treatment.
• Utilized four submerged solid substrates (Zn, Cu, Ni, Si) with a CaCl2 solution to study LIBS breakdown.
• Investigated spectral enhancement effects on Ca ionic and atomic lines, and other elements in seawater.

Main Results:

• Demonstrated significant improvement in Ca detection sensitivity using all tested substrates, even at low laser energy (10 mJ).
• The semiconductor Si substrate yielded the highest enhancement factors: >75 for Ca ionic lines and 29 for the Ca atomic line.
• Observed enhanced plasma excitation temperature and electron density due to decreased breakdown threshold, leading to higher signal intensity.

Conclusions:

• The solid substrate-assisted method effectively enhances underwater LIBS signals, overcoming plasma quenching limitations.
• Semiconductor substrates, particularly Si, offer superior performance for improving spectral line intensity and detection sensitivity.
• This approach enables the development of compact, low-power underwater in situ LIBS sensors for diverse marine applications.