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Ion trapping, reduced rotational viscosity, and accelerated electro-optic response characteristics in gold
1Department of Physics, Soft Matter and Nanomaterials Laboratory, The United States Naval Academy, Annapolis, Maryland 21402, USA.
Abstract:
The free-ion concentration in a nematic liquid crystal (LC) is found to be significantly reduced when gold nano-urchins (AuNUs) of 50-nm diameter are dispersed in the LC in dilute concentrations. The nano-urchins on AuNUs trap a significant amount of mobile ions, reducing the free-ion concentration in the LC media. The reduction of free ions results in a decreased rotational viscosity and accelerated electro-optic response of the LC. The study is carried out with several AuNUs concentrations in the LC, and the experimental results consistently suggest that there exists an optimal concentration of AuNUs, above which they tend to aggregate. At the optimal concentration, the ion trapping is maximum, rotational viscosity is at its lowest, and the electro-optic response is the fastest. Above this optimal AuNUs concentration, the rotational viscosity is found to increase, and consequently, the LC no longer exhibits an accelerated electro-optic response.
