Synthesis and optical properties of polythiophene-capped ZnS/Mn quantum dots

摘要

Polythiophene-capped Mn-doped ZnS (ZnS/Mn) quantum dots have been pre-pared through chemical precipitation method. The characterizations of synthe-sized quantum dots have been performed using X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), fourier transform infrared (FT-IR) spectroscopy, UV-visible spectroscopy and photoluminescence (PL) spectroscopy. Particle sizes were nearly 2 nm for both ZnS/Mn and polythiophene (PTh 15%) capped ZnS/Mn samples as estimated using XRD analysis. The estimated particle sizes, after PTh capping on ZnS/Mn, were nearly stable showing that there has been no dilution occurs in the ZnS/Mn quantum dots during the synthesis process. The capped ZnS/Mn quantum dots show weak agglomeration among them as observed from TEM images, which may be originated due to the electrostatic interaction between the particles as confirmed from the electrostatic potential surface analysis. The particle sizes calculated from the optical absorption spectra were remain consistent with size obtained from TEM images and XRD analysis. It was found that optical absorption bandgap of ZnS nanostructures varies with different concentration of capping agents. This was attributed to the quantum confinement effect. Strong electronic interaction between ZnS and polythiophene was observed from FTIR and electrostatic surface potential analysis which confirms the structural stability of the composite by creating large dipole moment of ~ 10.2675 Debye and lagre Mulliken charge - 0.437486e~-. The prepared polythiophene-capped samples reveals that the effective PL emission is in the range of 300 nm -700 nm. PL emission spectra show red shift with increasing capping concentration of PTh in ZnS/Mn quantum dots. These properties maintained the optical behavior of quantum dots and the addition of polymer with ZnS quantum dots may improve the flexibility of the nanostructure material, which will be highly preferable for foldable optical devices.