Colorimetric imaging of layer-by-layer molecular deposition on nanoplasmonic lycurgus cup array

Abstract

A quantitative label-free colorimetric imaging of biochemical molecular thin film deposition at a single molecule layer (2nm thickness) resolution was demonstrated on a nanoplasmonic sensor substrate known as nano Lycurgus Cup array (nanoLCA) and the penetration depth of the nanoplasmonic sensor was accordingly determined. Colorimetric nanoplasmonic imaging technique provides significant advantages in direct visualization and quick identification of surface deposited molecules. We implement layer by layer deposition of alternating polyelectrolyte layers with controlled thickness on the nanoLCA device to show surface color changes and determine the decay length of the device derived from the sensor spectral response to the molecular layer thickness. The calculated decay length of the nanoLCA device is 193 nanometers which corresponds well with the decay length of other known surface plasmon sensors. In addition micro contact molecular printing and transferring on the nanoLCA surface is used to selectively deposit poly-l-lysine and different alkanethiol molecules to demonstrate direct colorful visualization of surface patterned unlabeled molecules.