Drying Acoustically Levitated Droplets as Signal-Amplifying Platforms for Ultrasensitive and Multimode Laser Sensing

Area of Science:

• Analytical Chemistry
• Materials Science
• Nanotechnology

Background:

• Ultrasensitive detection of trace analytes is crucial for industry and life.
• Current methods often rely on analyte enrichment onto substrates.
• The coffee ring effect causes nonuniform analyte distribution, limiting sensing sensitivity and stability.

Purpose of the Study:

• To develop a substrate-free strategy to overcome the coffee ring effect.
• To enrich trace analytes and self-assemble a signal-amplifying platform.
• To enable ultrasensitive multimode laser sensing.

Main Methods:

• Acoustic levitation of droplets containing analytes and core-shell Au@SiO2 nanoparticles.
• Controlled drying of levitated droplets to form a self-assembled signal-amplifying platform.
• Utilizing nanoparticle-enhanced laser-induced breakdown spectroscopy (LIBS) and surface-enhanced Raman scattering (SERS) for detection.

Main Results:

• The proposed strategy effectively suppresses the coffee ring effect.
• The self-assembled platform dramatically enriches analytes, amplifying spectroscopic signals.
• Achieved atomic detection limits of 10^-3 mg/L for cadmium and chromium (via LIBS).
• Achieved molecular detection limits of 10^-11 mol/L for rhodamine 6G (via SERS).

Conclusions:

• Acoustic levitation enables substrate-free self-assembly of a signal-amplifying platform.
• This platform overcomes coffee ring effects, enhancing analyte enrichment.
• The method provides a pathway for ultrasensitive multimode laser sensing of trace substances.