C.N. Mihailescu

Biocompatibility and bioactivity enhancement of Ce stabilized ZrO2 doped HA coatings by controlled porosity change of Al2O3 substrates

Al(2) O(3) substrates with controlled porosity were manufactured from nanosized powders obtained by plasma processing. It was observed that when increasing the sintering temperature the overall porosity was decreasing, but the pores got larger. In a second step, Ce stabilized ZrO(2) doped hydroxyapatite coatings were pulsed laser deposited onto the Al(2) O(3) substrates. It was shown that the surface morphology, consisting of aggregates and particulates in micrometric range, was altered by the substrate porosity and interface properties, respectively. TEM studies evidenced that Ce stabilized ZrO(2) doped HA particulates ranged from 10 to 50 nm, strongly depending on the Al(2) O(3) porosity. The coatings consisted of HA nanocrystals embedded in an amorphous matrix quite similar to the bone structure. These findings were congruent with the increased biocompatibility and bioactivity of these layers confirmed by enhanced growing and proliferation of human mesenchymal stem cells.

Nanostructured Thin Optical Sensors for Trace Gas Detection

We report on new features of nanostructured coatings used in trace gas detection applications based on the modification of optical parameters. We review the general physical principles underlying the operation of optical detectors and introduce the basic systems used in trace gas recognition. Pd-doped SnO2 thin films were pulsed laser deposited on Si (100) and quartz substrates in 10 Pa O2 at different substrate temperatures. Coatings on Si were investigated by scanning electron microscopy and atomic force microscopy to determine their surface morphology and by grazing incidence X-ray diffraction for films structure. Twin films deposited on quartz were investigated using the m-line technique to monitor the variation of optical properties when exposed to butane diluted in N2 down to 100 ppm concentration. The acquired expertise was used to design a miniaturized system which was tried in real conditions.

Metamaterials for Antimicrobial Biofilm Applications: Photonic Crystals of Microspheres and Optical Fibers for Decontamination of Liquids and Gases

New decontamination methods are proposed. We examine the use of photonic crystals consisting of microspheres and/or optical fibers with various topological symmetries. The application of evanescent zone around metamaterials opens a new perspective to the decontamination procedure. Different methods of packing of microspheres and fibers to obtain an efficient contact zone of radiation (as UV radiation or laser pulses) with contaminated materials are considered. This can be boosted by the trapping manipulation of viruses and bacteria around fibers and microspheres. The special trapping zones may be designed under low frequency radiation after which one can apply the active UV coherent radiation through metamaterials. Then, the effective destroying of viruses and bacteria becomes possible. The progress of nonlinear models of the vibration modes excitation of viruses and bacteria biomolecules are reviewed.