I. Preda

Surface Functionalization of Nanostructured Porous Silicon by APTS: Toward the Fabrication of Electrical Biosensors of Bacterium Escherichia coli

Nanostructured porous silicon (nanoPS) basically consists in a network of silicon nanocrystals with high specific surface. Its intrinsic high surface reactivity makes nanoPS a very suitable material for the development of biosensors. In this work, the surface of nanoPS was functionalized by the use of (3-aminopropyl)triethoxysilane solutions in toluene. Escherichia coli (E. coli) antibodies were subsequently immobilized on the functionalized surfaces. Finally, fragments of this bacterium, which are specifically recognized by the antibodies, were immobilized. Moreover, devices with a metal/nanoPS/semiconductor/metal structure were fabricated aiming at the electrical biosensing of E. Coli bacterium. The experimental results showed a strong variation of the current as a function of the presence/absence of bacterium E. Coli and surface concentration.

X-ray absorption study of the local structure at the NiO/oxide interfaces

This work reports an X-ray absorption near-edge structure (XANES) spectroscopy study at the Ni K-edge in the early stages of growth of NiO on non-ordered SiO2, Al2O3 and MgO thin films substrates. Two different coverages of NiO on the substrates have been studied. The analysis of the XANES region shows that for high coverages (80 Eq-ML) the spectra are similar to that of bulk NiO, being identical for all substrates. In contrast, for low coverages (1 Eq-ML) the spectra differ from that of large coverages indicating that the local order around Ni is limited to the first two coordination shells. In addition, the results also suggest the formation of cross-linking bonds Ni-O-M (M = Si, Al, Mg) at the interface.