Tracking polystyrene particles

<p>Polystyrene particles of a given diameter are 1000 less bright than gold particles of the same size. This is due to the refractive index being closer to that of water. </p> <p>However, it is possible to image 19nm PS particles inside a <a class="wikilink" href="/hollow_optical_fiber/">hollow optical fiber</a> coupling ~10mW laser power to the fiber. </p> <p>In [<a class="litnote tooltip" href="/literature/@Faez2015">@Faez2015<span class="tooltiptext">Fast, Label-Free Tracking of Single Viruses and Weakly Scattering Nanoparticles in a Nanofluidic Optical Fiber</span></a>], two different measurements are done: calculating the size from the <a class="wikilink" href="/diffusion_coefficient/">diffusion coefficient</a> and grouping particles based on <a class="wikilink" href="/scattering_intensity/">scattering intensity</a>. </p> <p>Results based on diffusion coefficient are the same as <a class="wikilink" href="/nanoparticle_tracking_analysis/">nanoparticle tracking analysis</a>. However, the <a class="wikilink" href="/limitations_of_nanoparticle_tracking_analysis/">limitations of nanoparticle tracking analysis</a> are linked to poor localization accuracy, and those are inherent to the optical microscope. </p> <p>On the other hand, the intensity distribution of each particle in the channel is narrow. This is due to a relatively homogenous illumination profile. That may be the biggest advantage of <a class="wikilink" href="/nanoparticle_tracking_in_hollow_optical_fibers/">nanoparticle tracking in hollow optical fibers</a>, also of <a class="wikilink" href="/nanoparticle_tracking_in_nano_channels/">nanoparticle tracking in nano channels</a>. </p> <p>The crucial parameter to decide whether the method is worth pursuing, is that the intensity fluctuations of a single particle are narrower than the overall sample distribution. That may not be the case for the diffusion-based method, in which the uncertainty in size determination for a single particle is as broad (or more) than the overall sample.</p>