The continuous functionalization of nanoparticles in the gas-phase directly after their generation, chemical vapor functionalization, is studied with ZnO and 1-hexanol as a model system using two reactors in series. In the first reactor ZnO nanoparticles are synthesized in the gas-phase from diethylzinc and oxygen at 1,073 K with grain sizes of 13 nm as determined by Rietveld refinement of X-ray diffractograms. The second reactor, connected at the exit of the first reactor and kept at lower temperatures (573, 673, and 773 K), is used as a functionalization chamber. At the connection point of the two reactors, the vapor of 1-hexanol is injected to react with the surface of ZnO nanoparticles in the gas phase. The process has been analyzed by quadrupole mass spectrometry to obtain information about optimal conditions for functionalization. Dynamic light scattering data show that the functionalized particles have substantially improved colloidal dispersibility with hydrodynamic diameters of 60 nm. Diffuse reflectance fourier transform infrared spectra and 1H nuclear magnetic resonance spectra are consistent with 1-hexanol adsorbed at the particle surface acting as a functionalizing agent. The agglomerate size is substantially reduced owing to chemical vapor functionalization.
Chemical vapor functionalization ZnO nanoparticles Colloids and 1-hexanol Nanoparticle agglomeration
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The financial support of the German Research Foundation (DFG) through the Research Training Group: Nanotronics (1240) is gratefully acknowledged. We thank Nina Friedenberger (Farle group) for TEM measurements (Solid State Physics, University of Duisburg-Essen) and Manfred Zähres (Physical Chemistry, University of Duisburg-Essen) for NMR measurements. We are grateful for chemical analysis performed in the Epple group (Inorganic Chemistry, University of Duisburg-Essen) and Fourier Transform Infrared Spectroscopy measured in the Lorke group (Solid State Physics, University of Duisburg-Essen).
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