Controlling wide-spectrum fluorescence on Au/ZnSe multi-heterojunction

Abstract

We present a wide-spectrum photoluminescence (PL) enhancement effect on the multi-heterojunction of ZnSe quantum dots and gold nanoparticles (NPs). The Au/ZnSe heterojunction is fabricated using Langmuir–Blodgett assembling method. The photoluminescence is measured using a 150 nm aperture ultraviolet laser beam spot of a scanning near-field optical microscope. The enhancement of band-gap emission and defect PL, the quenching of the fluorescence are, respectively, observed, which depend on the distance of gold NPs and ZnSe quantum dots. The enhancement of the band-gap emission is ascribed to the local field enhancement induced by the resonant coupling between the excitons of ZnSe and the surface plasmons of gold NPs. The enhancement of the defect PL is a result of the electron trapped by the defect states in the process of transporting electrons from ZnSe QDs to gold NPs due to the increase of the built-in electric field to hinder the electron transfer to gold nanoparticles. In addition, the quenching of the fluorescence is due to the electron transfer from ZnSe quantum dots to gold NPs. Our result opens the possibility of applications in forming uniform optoelectronic heterojunction and in controlling fluorescent efficiency of PL devices.