ZnO nanoparticles (NPs), prepared by an improved alco-sol method at relatively low temperature using oleic acid (OA) as a stabilizing agent, were added to a liquid crystal matrix of 4'-pentyl-4-biphenylcarbonitrile (5CB). Addition of ZnO NPs not only decreased the threshold voltage but also had a dramatic effect (about 30% reduction) on the driving voltage (V-d) of 5CB. The decrease of V-d of liquid crystal can reduce power consumption, which may meet the demands of future power-saving liquid crystal displays.