Infrared spectroscopy of ZnO nanoparticles containing CO2 impurities.

Impurities play a major role in determining the optical and electrical properties of semiconductor nanoparticles. In this work, the presence and source of CO₂ impurities in ZnO nanoparticles were studied by IR absorption spectroscopy. Isotopic substitution was used to verify the vibrational frequency assignment. Isochronal annealing experiments were performed to study the formation and stability of the molecular impurities. Our results indicate that the molecules are much more stable than CO₂ adsorbed on bulk ZnO surfaces. By comparing our observations with similar results from IR spectroscopy of CO₂ trapped in carbon nanotubes [C. Matranga, L. Chen, M. Smith, E. Bittner, J. K. Johnson, and B. Bockrath, J. Phys. Chem. B 107, 12930 (2003)], we conclude that the molecules are trapped in the ZnO nanoparticles. [ABSTRACT FROM AUTHOR]