Nonvolatile memory effects in an orthoconic smectic liquid crystal mixture doped with polymer-capped gold nanoparticles

Promising applications of liquid crystal nanocomposites have driven extensive efforts to achieve nonvolatilememory effects for the realization of electronic storage devices. In this context, non-volatilememory effects in an orthoconic smectic liquid crystal mixture, with and without polymer capped goldnanoparticles, were investigated. The dielectric spectroscopy technique was performed by applying ad.c. bias during the measurement or a d.c. potential before the start of the measurement in order toobtain pre-conditioning of the sample. Both techniques showed the presence of non-volatile memoryeffects in the pure orthoconic smectic liquid crystal mixture similar to the doped one. The resultsdemonstrate that the addition of gold nanoparticles enhances the memory effect making it permanent.Our experimental evidence underlines the importance of the structure of the host liquid crystal andclearly suggests that the prolonged time memory effect, observed in the doped liquid crystal, is due tothe electric field inducing charge transfer from the liquid crystal molecules to the gold nanoparticles,thanks to the polymer-capping which acts as an ionic charge trapper. Such an ionic trap effect is alsoresponsible for strong reduction of total conductivity of the doped system.