Networked Gold-Nanoparticle Coatings on Polyethylene: Charge Transport and Strain Sensitivity

Networked films, comprising gold nanoparticles (ca. 4 nm core diameter) and 1,9-nonanedithiol, are deposited onto oxidized low-density polyethylene (LDPE) substrates via layer-by-layer self-assembly. Scanning electron microscopy and transmission electron microscopy images reveal a compact coating with a granular, nanoscale morphology. Conductance measurements at variable temperature are consistent with an Arrhenius-type activation of charge transport (activation energy: 52 meV). The excellent mechanical robustness of the coatings allows for studying their potential application as strain gauges. Expanding the films by up to 3% is accompanied by a reversible and approximately linear increase in resistance of up to approximately 50% (gauge factor ca. 17). Analyzing the results with an activated tunneling model suggests that the average increase in interparticle distances is significantly smaller than the geometric expansion at the substrate surface.