Aggregation of oxide nanocrystals

02.05.2007 - 30.04.2010
Research funding project
Controlling the interface properties of nanoparticles is critical to their successful application in sensors, fuel cells, electronic and solar energy conversion devices and in catalysis in general. The proposed project aims at the characterization of particle interface effects in semiconducting oxides such as titanium dioxide or tin dioxide. In the course of particle aggregation the formation of interfaces will be explored and their effect on the overall properties of a particle ensemble will be studied. For this purpose, isolated oxide nanocrystals will be synthesized in the gasphase using the chemical vapour deposition technique. Their size, structure and morphology as well as their spectroscopic properties will be characterized. In the following step, sample dispersion in a solvent and subsequent solvent removal will be employed in order to reach the controlled aggregation of particles and the formation of a porous particle network. Its structural and spectroscopic properties will be compared with those of non aggregated materials in order to infer the consequences of particle interface formation. The particle networks will be subjected to thermal annealing under vacuum conditions to induce oxygen deficiency and thus electronic conductivity. For the investigation of charge carrier localization effects, conduction band electrons will be employed as probes for electron paramagnetic resonance and infrared spectroscopy. With regard to sensor applications, the reversible adsorption of selected probe molecules will be explored. Adsorption isotherms will be related to the adsorbate-induced localization of free charge carriers as monitored by molecular spectroscopy. Complementary temperature-programmed desorption experiments will shed light on the relative stability of adsorbates within the porous structure of the particle network. The second important motivation for this research project is that solvent-mediated aggregation of oxide particles can represent a reliable and inexpensive approach for the generation of macroscopic objects which are made of nanocrystals. Choice of the solvent, temperature and pressure during the aggregation process will be evaluated concerning their impact on the design and fabrication of monolithic particle networks with modified electronic, optical and structural properties. The formation of particle interfaces provides means for the intentional generation of so far unexplored electronic states which are expected to be relevant in conductivity-based applications such as sensing or dye-sensitized solar cells. Again, the question how particle interfaces affect the integral ensemble properties needs to be addressed because corresponding insights will allow for a more efficient exploitation of nanoparticle networks in future technologies.

People

Project leader

Project personnel

Institute

Grant funds

  • FWF - Österr. Wissenschaftsfonds (National) Austrian Science Fund (FWF)

Research focus

  • Composite Materials: 15%
  • Special and Engineering Materials: 10%
  • Structure-Property Relationsship: 25%
  • Surfaces and Interfaces: 25%
  • Materials Characterization: 25%

Keywords

GermanEnglish
oxidische Halbleiteroxide semiconductors
Partikel Aggregationparticle aggregation
Partikelgrenzflächenparticle interfaces
Adsorptionadsorption
Porositärporosity

External partner

  • Service-Einrichtung fur Transmissions-Elektronenmikroskopie (USTEM)

Publications