A novel method for measuring nanoparticle size could have applications in industry and basic materials science research.
Nanoparticles are present in everything from paints to pharmaceutical products. While nanoparticles have many important characteristics, such as molecular composition and shape, it is their size that determines many chemical and physical properties. A new technique relying on an optical vortex—a laser beam whose wave fronts twist around a dark central region—allows researchers to characterize nanoparticle size rapidly and continuously [1]. This light-based size probe might one day find applications in numerous industrial settings and aid fundamental materials science research.
It is difficult to precisely synthesize nanoparticles with the desired dimensions, so manufacturers must often validate that their nanoparticles have the right size to comply with regulations and to ensure product quality. There are many ways of determining nanoparticle size, but one popular approach, dynamic light scattering (DLS), is based on measurements of Brownian motion, the random particle movement caused by jostling from the surrounding liquid medium. In DLS, the Brownian motion is determined by measuring fluctuations in laser light scattering from the nanoparticles. In general, the faster the Brownian motion, the smaller the particles. But current techniques are generally not capable of characterizing the largest particles and measuring them continuously.
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