Novel Signal Enhancement Strategy in Laser-induced Breakdown Spectroscopy for Marine Aerosols via Standing-Wave Acoustic Trap

Abstract Direct aerosol laser-induced breakdown spectroscopy (aerosol-LIBS) is attractive for elemental analysis because of its rapid and in situ detection capability. However, its analytical performance is often limited by the inherently low probability that airborne particles overlap with the laser-induced plasma during each laser pulse. To address this limitation of the aerosol-LIBS, an acoustic tweezer-assisted signal-enhancement strategy was introduced for marine aerosol analysis. Simulated marine aerosols were generated from a KCl aqueous solution and interrogated under identical LIBS excitation and spectral acquisition conditions with and without ultrasonic standing-wave assistance. The results showed that the acoustic field led to an overall enhancement of aerosol-LIBS emission, including both continuum background and analyte-related characteristic lines. In particular, the emission intensities of the K I atomic lines at 766.49 and 769.90 nm increased by approximately 3.64-fold under the standing-wave-assisted conditions. Meanwhile, statistical analysis demonstrated that the breakdown probability increased from 0.544 to 0.762, the particle hit probability increased from 0.314 to 0.966, and the joint probability of breakdown and real hit increased from 0.171 to 0.736. Furthermore, the intensity distributions over 1000 lasing events further confirmed this enhancement, showing that the ultrasonic standing-wave assistance shifted both the total emission intensity and K I characteristic-line intensity toward higher values, with their mean values increasing from 4.14×10 6 to 5.96×10 6 and from 4.03×10 2 to 1.47×10 3 , respectively. These results indicate that ultrasonic standing-wave assistance enhances aerosol-LIBS by enriching particulate analytes within the laser focal volume and strengthening laser-particle interactions, thereby improving the breakdown ignition, plasma formation, and analyte detection efficiency. The proposed strategy provides a simple and effective route for improving aerosol-LIBS and shows strong potential for practical online monitoring and elemental analysis of marine aerosols.