Regulating the Fluorescence Emission of CdSe Quantum Dots Based on the Surface Ligand Exchange with MAA

Abstract

Cadmium selenide (CdSe) quantum dots (QDs) is a promising semiconductor and fluorescence nanocrystal with quantum size effect. To address the problem of fluorescence emission during the process of the ligand transformation of colloidal cluster CdSe QDs from nonpolar organic solvents to polar inorganic aqueous solutions, the surface ligand exchange with mercapto acetic acid (MAA) was proposed. It was attributed to the Cd‐O bond breaking and the Cd‐S bond formation. The intensity and wavelength of fluorescence emission spectra could be adjusted by controlling the concentration of MAA. The photoluminescence (PL) spectra and UV‐Vis absorption spectra of colloidal cluster CdSe QDs indicated that the electronic properties of the interface varied with the exchange of the surface ligands. Moreover, the band‐edge emission quenching occurred and the maximum redshift of the PL spectrum could reach 28 nm. The enhancement of the deep trap emission peaks of CdSe QDs appeared in 600‐900 nm region, and the maximum blue shift of the defect peak in PL spectrum could reach 80 nm with the increase concentration of MAA. The absorption spectra and PL spectra on the surface of porous alumina thin film were used to further analyze the charge separation and capture of charge carriers. This novel organic‐inorganic ligand exchange method provides an effective strategy for regulating fluorescence and electron transfer, which could be used on biological, solar cells or other practical applications.