Nanoporous anodic aluminum oxide (AAO) membranes are synthesized through the anodization of aluminum in acidic electrolytes and are made of parallel hollow nanochannels with diameters in the range 20-110 nm. These nanoporous systems are promising host systems for confinement of condensed matter. Characterizing their structure and composition is thus primordial to study the behavior of confined objects. Techniques able to analyze the entering of species and their interaction with the matrix are also necessary. During this talk, I’ll report on two studies involving neutron techniques coupled to Scanning Electron Microscopy (SEM) imaging.
In the first approach, Small-Angle Neutron Scattering (SANS) has been used to characterize the structure and composition of well-defined AAO membranes1. In particular, a detailed strategy is developed to insure a complete description of the SANS data: conditions for optimal SANS measurements, channel arrangement and fitting method. We pointed out that the probed length in the fitting model is a critical parameter related to the longitudinal pore ordering. Applied to several AAOs, this approach indicates the existence of a contaminated shell in the AAOs and the specific use of deuterated electrolytes allows us to confirm the origin of such contamination (i.e. anions coming from the electrolytes).
In the second approach, neutron reflectivity (NR) is used in combination with SEM to analyze the entering of polyelectrolyte in duplex AAO2. Duplex AAO are composed of two connected layers having similar pore density but different pore diameters. Such organization induces a geometrical constriction, i.e. a reduction of pore diameter along the pore channel, that plays an important role and are promising systems to study the influence of geometrical constriction on the confinement of condensed matters. Here, duplex AAOs are characterized by NR and quantitative information about the entering and adsorption of polyelectrolytes (PEs) in nanopores are extracted.
1. Christoulaki, A.; Chenneviere, A.; Grillo, I.; Porcar, L.; Dubois, E.; Jouault, N. A novel methodology to study nanoporous alumina by small-angle neutron scattering. Journal of Applied Crystallography 2019, 52 (4), 745-754 DOI: doi:10.1107/S160057671900726X.
2. Christoulaki, A.; Chennevière, A.; Dubois, E.; Jouault, N. Duplex nanoporous alumina and polyelectrolyte adsorption: more insights from a combined neutron reflectivity and electron microscopy study. Nanoscale 2019, 11 (5), 2148-2152 DOI: 10.1039/C8NR09018A.
Dr. Christian Franz