Fluorescence behavior of cysteine-mediated Ag@CdS nanocolloids

Langmuir. 2009 Jun 2;25(11):6377-84. doi: 10.1021/la8042507.

Abstract

Ag@CdS quantum dots were synthesized by a colloidal method. CdS nanoparticles stabilized by L-cysteine were doped with varying silver concentrations. Ag@CdS nanoparticles were characterized by UV-visible spectroscopy, steady-state and time-resolved fluorescence, X-ray diffraction, Fourier transform infrared resonance (FTIR), and transmission electron microscopy. The effect of dopant concentration and effect of aging of Ag@CdS colloids were studied. At low silver content, emission was found to enhance, while at high silver content, emission quenching was observed after aging. Ag-CdS nanocolloids exhibited multiexponential decay with tau2 being a long-lived component. X-ray diffraction spectra of as prepared samples indicated that silver occupies an interstitial position, while for annealed samples, Ag+ ions get oxidized to Ag2+ and substituted for Cd2+ in the CdS lattice. FTIR studies have shown that cysteine acts as a monodentate ligand for cadmium and silver for as-prepared sample, whereas it acts as a tridentate ligand for annealed samples toward silver. Transmission electron microscopy of as-prepared samples showed spherical-shaped composites with a uniform layer of capping molecules.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cadmium Compounds / chemistry*
  • Colloids / chemistry*
  • Cysteine / chemistry*
  • Fluorescence
  • Microscopy, Electron, Transmission
  • Molecular Structure
  • Nanoparticles / chemistry*
  • Quantum Theory*
  • Silver / chemistry*
  • Spectroscopy, Fourier Transform Infrared
  • Sulfides / chemistry*

Substances

  • Cadmium Compounds
  • Colloids
  • Sulfides
  • cadmium sulfide
  • Silver
  • Cysteine