Lou Zhidong

Electrical bistable devices using composites of zinc sulfide nanoparticles and poly-(N-vinylcarbazole)*

N-dodecanethiol capped zinc sulfide (ZnS) nanocrystals were synthesized by the one-pot approach and blended with poly (N-vinylcarbazole) (PVK) to fabricate electrical bistable devices. The corresponding devices did exhibit electrical bistability and negative differential resistance (NDR) effects. A large ON/OFF current ratio of 104 at negative voltages was obtained by applying different amplitudes of sweeping voltage. The observed conductance switching and the negative differential resistance are attributed to the electric-field-induced charge transfer between the nanocrystals and the polymer, and the charge trapping/detrapping in the nanocrystals.

Estimation of luminescence lifetime in frequency domain

Absorption is the origin of luminescence. But it must be noticed that the lifetime of luminescence might reversely influence the rate of absorption. In this paper, it is reported that the luminescence intensity of copper and manganese changes with the driving frequency at constant voltage. The variation of luminescent intensity depends only on the lifetime of luminescence but not on the type of quenching or other factors. Generally the rate of absorption is dominantly determined by the material property and the lifetime of luminescence centres, the absorption of shorter lifetime centre will be larger than that of the longer lifetime centre at the same excited condition.