Zachary Fink*, Xuefei Wu, Paul Y. Kim, Alex McGlasson*, Maged Abdelsamie, Todd Emrick*, Carolin M. Sutter-Fella, Paul D. Ashby, Brett A. Helms, Thomas P. Russell*. This work studies the in-situ in-plane packing of nanoparticle mixtures containing spherical Au and non-plasmonic nanoparticles using UV-vis reflection spectroscopy.