Irreversible redshift of transmission spectrum of gold nanoparticles doped in liquid crystals

The absorption peak of gold (Au) nanoparticles doped in liquid crystal (ANDLC) is controllable by applying an external applied voltage before aggregation occurs. Au nanoparticles aggregate when the dielectrophoresis force, which is induced by the gradient of the square of the electric filed close to the sides of the host liquid crystal cell, overcomes the viscosity between Au nanoparticles and the LCs. This result leads to the irreversible redshift. A controllable filter with unpolarized light enables an ANDLC cell under the threshold voltage to prevent the aggregation effect.