Nanoporous SnO₂ thin films were elaborated to serve as sensing electrodes for label-free DNA detection using electrochemical impedance spectroscopy (EIS). Films were deposited by an electrodeposition process (EDP). Then the non-Faradic EIS behaviour was thoroughly investigated during some different steps of functionalization up to DNA hybridization. The results have shown a systematic decrease of the impedance upon DNA hybridization. The impedance decrease is attributed to an enhanced penetration of ionic species within the film volume. Besides, the comparison of impedance variations upon DNA hybridization between the liquid and vapour phase processes for organosilane (APTES) grafting on the nanoporous SnO₂ films showed that vapour-phase method is more efficient. This is due to the fact that the vapour is more effective than the solution in penetrating the nanopores of the films. As a result, the DNA sensors built from vapour-treated silane layer exhibit a higher sensitivity than those produced from liquid-treated silane, in the range of tested target DNA concentration going to 10 nM. Finally, the impedance and fluorescence response signals strongly depend on the types of target DNA molecules, demonstrating a high selectivity of the process on nanoporous SnO₂ films.

In this study, hydroxyapatite (HAp) coated Mg matrix composites were fabricated for biodegradable implant applications. Spark plasma sintering was employed to fabricate the Mg-10 wt% ZnO composite substrates. HAp was coated on the surface of the sintered composites and pure Mg by a chemical solution treatment. SEM and optical micrographs of coated samples showed that HAp grew homogeneously and formed a layer on the entire surface of both pure sintered Mg and Mg composites. The immersion and polarization test results demonstrated that the HAp coating significantly improved the corrosion resistance of the sintered composites. While the HAp coating layer is not effective in the improvement of the pure Mg substrate, cell culture test results revealed that the HAp coating improved cell adhesion and proliferation on the composites effectively through 72 h, while no cell could survive on the uncoated composites after 72 h. In addition, the corrosion tests and cell culture test results indicated that the composite with longer sintering time has better corrosion resistance and cell viability than those of the composite with shorter sintering time. The findings suggested that the HAp-coated Mg-10 wt% ZnO-2.5 h + 10 min composite is a high-potential candidate for biodegradable implant applications.

In this work, MgAl2O4 transparent ceramics was fabricated from combustion-synthesized nanopowders by pulsed electric current sintering (PECS) combined with two-step sintering. Ceramic powder was densitified using two-step heating, namely the first-step temperature was 1100 oC with holding time of 60 min and the second-step temperatures in range from 1300 oC to 1450 oC with 20 min duration. The results showed that the transparent ceramic samples sintered at 1100 oC/60 min – 1400 oC/20 min had grain size of 177 ± 8 nm, relative density about 99 %, transmittance up to 80 %, and Vickers hardness of 18 GPa. These values were higher than that of samples obtained by one-step sintering at 1400 oC.