The study of aerosolized droplets with nanometer absorbing structures using a contactless photoacoustic technique and the finite-difference time-domain method

Krishnan Sathiyamoorthy; Eric Strohm; Omar Nusrat; Taehoon Bok; Ahmet E. Karataş; Michael C. Kolios

doi:10.1117/12.2650522

17 March 2023 The study of aerosolized droplets with nanometer absorbing structures using a contactless photoacoustic technique and the finite-difference time-domain method

Krishnan Sathiyamoorthy, Eric Strohm, Omar Nusrat, Taehoon Bok, Ahmet E. Karataş, Michael C. Kolios

Author Affiliations +

Proceedings Volume 12397, Frontiers in Biological Detection: From Nanosensors to Systems XV; 1239708 (2023) https://doi.org/10.1117/12.2650522
Event: SPIE BiOS, 2023, San Francisco, California, United States

Abstract

This study explores a novel approach to detect virus-laden droplets in the ambient air. An air-coupled photoacoustic (PA) technique is considered for this purpose. The free space PA system is developed using an air-coupled transducer with a center frequency of 350 kHz and a nanosecond pulsed laser operating at wavelength 533 nm. Water droplets containing 80 nm gold (Au) nanoparticles were aerosolized using a custom-built spraying system. The size of the droplets generated was in the range of a few hundred nanometers to 100 μm. Au nanoparticles of four concentrations (0, 8x10^-12, 16x10^-12, and 32x10-12 mol/L) were sprayed into the investigation domain interrogated by a laser beam, where the average PA signal from the droplets was 3.11±2.35, 1.28±1.26, 0.99±0.97, and 0.92±1.11 mV/mJ, respectively. The study showed, surprisingly, that water droplets without Au nanoparticles had a higher PA signal than those containing Au nanoparticles. A numerical analysis using a finite difference time domain method was used to explore the reasons for this unexpected finding. Results suggested that the undoped droplets could potentially focus the light, significantly increasing the fluence at the focus. When Au nanoparticles were present, the fluence within the droplet decreased, resulting in a lower PA signal.

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Krishnan Sathiyamoorthy, Eric Strohm, Omar Nusrat, Taehoon Bok, Ahmet E. Karataş, and Michael C. Kolios "The study of aerosolized droplets with nanometer absorbing structures using a contactless photoacoustic technique and the finite-difference time-domain method", Proc. SPIE 12397, Frontiers in Biological Detection: From Nanosensors to Systems XV, 1239708 (17 March 2023); https://doi.org/10.1117/12.2650522

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KEYWORDS

Gold

Gold nanoparticles

Particles

Finite-difference time-domain method

Light absorption

Photoacoustic spectroscopy

Viruses

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