Emergence of 2MPA as an Effective Coating for Highly Stable and Luminescent Quantum Dots

Acar H. Y., Kas R., Yurtsever E., ÖZEN C., Lieberwirth I.

JOURNAL OF PHYSICAL CHEMISTRY C, vol.113, no.23, pp.10005-10012, 2009 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 113 Issue: 23
  • Publication Date: 2009
  • Doi Number: 10.1021/jp811104s
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.10005-10012
  • Middle East Technical University Affiliated: Yes


3-Mercaptopropionic acid (3MPA) is a popular coating material for the preparation of aqueous quantum dots, yet its isomer 2-mercaptopropionic acid (2MPA) has not been much studied. Here, we present a detailed study on the aqueous synthesis of CdS quantum dots with a 2MPA coating. Reaction variables Such as the Cd/S ratio, 2MPA/Cd ratio, pH, and temperature were individually studied to evaluate the influence of these variables on particle size and luminescence. At the optimum ratios and reaction conditions, a quantum yield (QY) as high as 54% was achieved. These quantum dots (QDs) have exhibited excellent colloidal and photostability over eight months of study. The color of the emission can be tuned by the reaction temperature and/or Cd/S ratio. 3MPA-coated US nanoparticles were prepared at various 3MPA/Cd ratios for comparison. The highest QY achieved for CdS-3MPA was 15%, and the luminescence decreased dramatically overtime. Ab initio calculations and spectroscopic characterization did not reveal a significant difference in the structure or particle-coating interaction between 2MPA- and 3MPA-coated QDs. Luminesence lifetime measurements indicated longer lifetimes and a larger contribution of the surface-related emission, indicating better removal of quenching defects froth the surface in 2MPA-coated particles compared to that of CdS-3MPA. On the basis of the provided evidence, we report 2MPA as a new and better alternative to the widely used 3MPA for superior luminescence and long-term photo and colloidal stability.