Abstract
A new method is proposed in this paper to detect airborne nanoparticles, detecting the light scattering caused by both the particle and the surrounding molecules, which can surpass the limitations of conventional laser optical methods while maintaining simplicity and cost-effectiveness. This method is derived from a mathematical analysis that describes the particle light scattering phenomenon more exactly by including the influence of light scattered from surrounding gas molecules. The analysis shows that it is often too much of a simplification to consider only light scattering from the detected nanoparticle, because light scattering from the surrounding gas molecules, whether visible or invisible to the sensor, is important for nanoparticle detection. An image detection approach utilizing the light scattering from surrounding air molecules is described for the detection of airborne nanoparticles. Tests using monodisperse nanoparticles confirm that airborne particles of around 50 nm in size can even be detected using a low-cost testing device. This shows further that even when using a simple image processing code, captured particle light scattering images can be converted digitally into instantaneous particle counts or concentrations. The factors limiting conventional pulse detection are further discussed. This new method utilizes a simple static light scattering (SLS) approach to enable the development of new devices with better detection capabilities, paving the way for the further development of nanoparticle detection technology.
Highlights
Airborne nanoparticles are of great importance due to their impact on a range of issues, from air pollution to disease transmission [1]
The air molecules surrounding suspended particles respond to changes in the electric field of the illuminating light wave, emitting light waves as light scattering in the same way as the suspended particles
As shown by the mathematical analysis described the light scattering from air molecules surrounding particles can be utilized for detecting nanoparticles, especially when using a light scattering image detection
Summary
Airborne nanoparticles are of great importance due to their impact on a range of issues, from air pollution to disease transmission [1]. Particles in a suspending media can be detected by measuring fluctuations in the intensity of light scattered from moving particles, as in dynamic light scattering (DLS) measurement [5]. This paper presents a new strategy for detecting nanoparticles beyond the detection limit of conventional laser particle detectors It first introduces an aerosol light scattering equation that includes light scattered from a suspended nanoparticle and from air molecules surrounding the nanoparticle. The equation reveals the effect of light scattered from air molecules, indicating a different path to enhance nanoparticle detection It shows the evaluation of a low-cost testing device, which is built for the particle light scattering image detection suggested by the mathematical analysis, using two types of monodisperse particles. It further demonstrates that the light scattering images of airborne nanoparticles captured in particle detection videos can be further converted to the particle concentration using a simple image processing code, showing that the results of the light scattering image detection method can be presented in the same way as those of the conventional light scattering pulse detection method
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