Terbium-doped gadolinium oxysulfide (Gd<sub>2</sub>O<sub>2</sub>S:Tb) nanoparticles were synthesized by hydrothermal precipitation of urea. On the reaction, were analyzed variables as the temperature of solutions, the reaction time and the stirring velocities as main factors in the crystal growth. WAXD TEM and FTIR analysis were used to characterize the Crystallographic phase, morphology and chemical vibrations of the materials. Moreover, the photoluminescent properties were evaluated as response at the UV light, obtaining the main emission at 544 nm produced by <sup>5</sup>D<sub>4</sub> → <sup>7</sup>F<sub>5</sub> transition of the Tb<sup>3+</sup> ions. Besides, we found that the host lattice and doped-ions concentration is essential to obtain a strong visible photoluminescence evaluated experimentally.
In this research, hybrid hydrogels of poly (vinyl alcohol)/ porous silicon (PSi)/theophylline were synthesized by the
freezing and thawing method. We evaluated the influence of the synthesis parameters of the poly (vinyl alcohol) (PVA)
hydrogels in relation to their ability to swell and drug released. The parameters studied (using an experimental design
developed in Minitab 16) were the polymer concentration, the freezing temperature and the number of freezing/thawing
(f/t) cycles. Nanostructured porous silicon particles (NsPSi) and theophylline were added within the polymer matrix to
increase the drug charge and the polymer mechanical strength. The hybrid hydrogels were characterized by Infrared
Spectroscopy Fourier Transform (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy
(TEM) and Differential Scanning Calorimetry (DSC), drug delivery kinetics were engineered according to the desired
drug release schedule.
PSi microcavity (PSiMc) is characterized by a narrow resonance peak in the optical spectrum that is very sensitive to
small changes in the refractive index. We report that the resonant optical cavities of PSi structures can be used to
enhance the detection of labeled fluorescent biomolecules. Various PSi configurations were tested in order to compare
the optical response of the PSi devices to the capture of organic molecules. Morphological and topographical analyses
were performed on PSiMc using Atomic Force (AFM) and Scanning Electron (SEM) microscopies. The heterogeneity in
pores lengths resulting from etching process assures a better penetration of larger molecules into the pores and sensor
sensitivity depends on the pore size. Molecular detection is monitored by the successive red shifts in the reflectance
spectra after the stabilization of PSiMc with
3-aminopropyltriethoxysilane (APTES). The glucose oxidase was cross linked into the PSiMc structures following a silane-glutaraldehyde (GTA) chemistry.
Porous silicon (PSi) nanostructures have remarkable optical properties that can be used for biosensing applications. In
this paper we report first on the fabrication of heavily doped p-type PSi with pore diameters in the range of 400-4000
nm. The nonspecific and specific binding of the Glucose Oxidase protein (GOX) was then studied onto the PSi mirrorlike
substrate. Adsorption of GOX was tuned by the pH of the protein solution (pI = 4.2) depending of the surface
charge. PSi matrixes were first stabilized by thermal oxidation and GOX adsorption was performed once directly on the
oxidized PSi surface, and also on previously functionalized PSi surfaces. In the latter case the GOX was coupled to the
PSi via the S-H group of the 3-(mercaptopropyl)trimethoxysilane (MPTS). The silane-GOX and GOX interactions on
the PSi surface were monitored by the Fourier Transformed Infrared spectra that display characteristic bands of the
linked molecules. The interference spectrum shows a large blue shift in the Fabry-Perot interference pattern caused by
the change in the refractive index of the medium implying a decrease in the effective optical thickness. Quantitative
analysis shows that chemically modified PSi samples admit approximately 24% of GOX. Activity assay proved that the
protein preserves its catalyst properties under these adsorption conditions.