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Keywords:

  • pearl-necklace morphology;
  • quantum dots;
  • surface-adsorbed dopant;
  • tunability

Abstract

We have studied the optical properties of size-tunable undoped and Mn2+-doped cadmium telluride (CdTe) quantum dots (QDs) of monodisperse suspensions with emission wavelength varying between 500 and 680 nm. The role of the surface is investigated for obtaining size-tunable, bright, and stable CdTe QDs. Differentially tunable optical properties of doped and undoped CdTe QDs has been reported. Unlike the continuous redshifting in the absorption spectra of pristine CdTe system, an unusual blueshift is observed for doped CdTe system after a certain time period of refluxion, followed by again a redshift and the disappearance of earlier peak with further refluxing. The available size range and optical properties are significantly controlled through Mn2+ doping. The surface adsorbed Mn promotes ripening of the doped system as well as disintegration into smaller fraction after saturation in growth occurs. An optimum size fraction is identified for both the systems based on their photoluminescence (PL) quantum yield. The photophysics of Mn2+-doped nanocrystals has been proposed.