Literature/202212091127 iscat for refractive index of evs

<ul> <li>Source: [<a class="litnote tooltip" href="/literature/@kashkanova2022">@kashkanova2022<span class="tooltiptext">Precision size and refractive index analysis of weakly scattering nanoparticles in polydispersions</span></a>]</li> <li>Tags: <a href="/tags/iSCAT">#iSCAT</a> <a href="/tags/Refractive-Index">#Refractive-Index</a> <a href="/tags/EV">#EV</a> <a href="/tags/microscopy">#microscopy</a> </li> </ul> <p>To overcome some of the <a class="wikilink" href="/limitations_of_nanoparticle_tracking_analysis/">limitations of nanoparticle tracking analysis</a>, this paper leverages the use of <a class="wikilink" href="/iscat/">iSCAT</a> to measure the refractive index of particles, and to measure the size of smaller objects. The biggest advantage of using iSCAT over <a class="wikilink" href="/light_sheet/">light sheet</a> for a <a class="wikilink" href="/nanoparticle_tracking_analysis/">nanoparticle tracking analysis</a> measurement is the superior signal to noise ratio for smaller particles. Interferometric measurements scale like $d^3$ instead of $d^6$. </p> <p>Moreover, a smaller response to diameter allows to extend the dynamic range of the instrument. The setup is the traditional iScat setup using a $\lambda/4$ waveplate in combination with a polarising beamsplitter.: </p> <p><img alt="iScat Setup for nanoparticle tracking" src="/images/iScat_iNTA_setup.png" /></p> <div class="admonition note"> <p class="admonition-title">Note</p> <p>The objective is placed $1\mu m$ above the substrate and is stabilized with an active focus-lock. </p> </div> <h3>Comparison with other methods</h3> <p><img alt="images/Pasted image 20221228140849.png" class="wikiimage" src="/images/pasted image 20221228140849.png" /> The image above is the result of measuring size of 30nm <strong>gold particles</strong> with 4 commercially available instruments (<a class="wikilink" href="/dls/">DLS</a>, <a class="wikilink" href="/tem/">TEM</a>, <a class="wikilink" href="/sem/">SEM</a>, and <a class="wikilink" href="/nta/">NTA</a>) plus the custom iNTA setup. It is surprising that iNTA has a resolution similar to that of TEM, considering they are only exploiting the diffusion coefficient measurement to calculate diameter. </p> <p>In the text, the authors claim that they use traces with at least 25 localization points and use a track-length weighted distribution. Sadly they don't fully comment on how they manage to to get a $3X$ improvement on the data generated by NTA, since the root of the measurement is the same. Can it be simply a better localization accuracy given by a larger frame rate? <img alt="images/Pasted image 20221228140744.png" class="wikiimage" src="/images/pasted image 20221228140744.png" /></p>