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The luminescent and dosimetric properties of the MgB4O7 phosphor co-doped with Tm and Dy ions (MgB4O7:Tm,Dy) obtained by the solution combustion technique were investigated. With the prepared material, sintered dosimeters in pellet form were made. The MgB4O7 dosimeters doped with Tm and Dy with 0.25 and 0.10 mol% respectively and sintered at 1223 K for 3 h showed a sensitivity almost 11 times greater than the sensitivity of the TLD-100 commercial dosimeter. The TL response as a function of the gamma dose showed linearity up to 50 Gy followed by a supralinearity region and, above 500 Gy, the saturation region of the electron traps is reached. The fading of the main TL peak was negligible in the first five days after irradiation reaching 13% after 60 days and the lower detection limit was 43 µGy. The kinetic parameters were determined using the deconvolution method revealing general and second order kinetics. The morphology, crystallography and photoluminescence of the prepared phosphor samples are also reported.
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The present work studies the effect of Mn doping on the crystalline structure of the Hap synthesized by the hydrothermal method at 200 °C for 24 h, from Ca(OH)2 and (NH4)2HPO4, incorporating MnCl2 to 0.1, 0.5, 1.0, 1.5 and 2.0 %wt of Mn concentrations. Samples were characterized by the X-Ray Diffraction technique, which revealed the diffraction peaks that corresponded to the hexagonal and monoclinic phase of the Hap; it was observed that the average size of crystallite decreased from 23.67 to 22.69 nm as the concentration of Mn increased. TEM shows that in all samples, there are two distributions of particle sizes; one corresponds to nanorods with several tens of nanometers in length, and the other in which the diameter and length are very close. FTIR analysis revealed absorption bands corresponding to the PO4-3 and OH- groups characteristic of the Hap. It was possible to establish a substitution mechanism between the Mn and the ions of Ca+2 of the Hap. From the Alamar blue test, a cell viability of 86.88% ± 5 corresponding to the sample of Hap at 1.5 %wt Mn was obtained, considered non-cytotoxic according to ISO 10993-5. It also evaluated and demonstrated the good osteoinductive properties of the materials, which were verified by histology and immunofluorescence expression of osteogenic markers. Adhesion, viability, biocompatibility and osteoinductive properties, make these materials candidates for future applications in bone tissue engineering with likely uses in regenerative medicine.
Assuntos
Durapatita , Nanotubos , Durapatita/química , OsteogêneseRESUMO
Silver nanowires were used as templates to synthesize silver-doped CeO(2) (Ag-CeO(2)) nanotubes by the precipitation method. The precipitated solid was dried at 100 °C for 24 h and calcined at 500 °C for 5 h. A TEM, HRTEM, LV-SEM and XRD study was carried out to determine the micro and nanostructural characteristics of the samples. LV-SEM analysis allowed us to observe microtubular empty structures constituted by Ce, O and Ag as indicated by EDS. These tubular structures, with an external diameter from 120 to 280 nm and an internal diameter from 40 to 80 nm, were mainly composed of 11 nm ceria nanoparticles. This kind of structures was obtained when CeO(2) nanoparticles covered the Ag nanowires during the synthesis. Due to the presence of ammonium hydroxide used during the synthesis, a fraction of the silver nanowire reacts and Ag atoms begin to migrate outside the ceria microtube. When the sintering process is applied, the Kirkendall effect can occur. So, out-diffusion of the remnant Ag through the interface is faster than the in-diffusion of the shell material (CeO(2)), which eventually results in a coaxial nanotube on completion of the non-equilibrium interdiffusion, leaving the central core completely empty, driving the formation of hollow tubular Ag-CeO(2) structures as a result.
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The goal of this work was to analyse ZrO(2) in the pure state and when doped with Ag nanoparticles, by electron microscopy, x-ray diffraction and thermoluminescence methods. According to the results obtained, Ag nanoparticles did not modify the morphology or the crystalline structure of the ZrO(2). The thermoluminescent (TL) response of pure ZrO(2) showed two peaks, one at 334 K and the other at 417 K, when it was exposed to ultraviolet (UV) radiation, and at 342 and 397 K when gamma radiation was used. For ZrO(2) impregnated with Ag nanoparticles a diminished TL intensity due to nanoparticle shielding was observed, but the glow curve shape was similar. However, when Ag nanoparticles were added during the ZrO(2) synthesis, a shift of the TL peaks towards higher temperature values with reference to pure ZrO(2) was observed. A linear dependence of the integrated TL signal as a function of the irradiation dose was observed in all analysed samples. It was possible to determine some kinetic parameters, such as activation energy, kinetic order and frequency factor, using the sequential quadratic programming glow curve deconvolution; it was found that these values are highly dependent on the type of radiation used. Ag nanoparticles present in ZrO(2) also modified the kinetic parameters, mainly when they were added during the synthesis of ZrO(2). Our results reinforce the possibilities of using pure and doped ZrO(2) as an appropriate dosimetric material in radiation physics.
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The results of transmission electron microscopy and thermoluminescence (TL) studies in silica samples containing Fe and Cu nanosized particles show an important enhancement of their TL response when compared with known reports for pure silica samples. The effect of surface electronic states in the nanoparticles, interacting with the matrix, may be responsible for this new size-dependent effect.