TiO 2 -SiO 2 composites containing 10 wt%, 20 wt%, 30% and 40 wt% of TiO 2 , obtained by using preformed mesoporous silica nanoparticles (MSNs) and titanium isopropoxide as titanium source, have been investigated in detail using a variety of techniques. All the samples were characterized by N 2 -physisorption, X-ray powder diffraction (XRPD), diffusive reflective UV-vis spectroscopy (DRUV-vis), X-ray photoelectron spectroscopy (XPS) and imaged using transmission electron microscopy (TEM). The TiO 2 -MSN composites, that exhibited a spherical morphology, high specific surface areas and titania in the anatase phase, owing to their specific chemical-physical properties were studied as catalysts in the photocatalytic degradation of methylene blue, methyl orange and paracetamol, as examples of polluted wastewaters. The well-defined porous structures of MSNs may offer a special environment for titania nanoparticles, increasing the specific surface area and the thermal stability of the composite, thus modifying the photocatalytic behavior of the materials. The TiO 2 loading, the particle size and the surface characteristics were related to the degree of UV absorption and the measured energy band gap of the nanocomposites. A cooperative effect between the two components (TiO 2 and SiO 2 ) could be the key factor at the basis of the good photocatalytic performances: nanostructured TiO 2 in intimate contact with MSN provides the sites for generation of OHc radicals by oxidation of water and the SiO 2 skeleton is able to adsorb the molecules of cationic dyes and prevent poisoning of the TiO 2 surface.
Colorectal cancer (CRC) shows highly ineffective therapeutic management. An urgent unmet need is the random assignment to adjuvant chemotherapy of high-risk stage II and stage III CRC patients without any predictive factor of efficacy. In the field of drug discovery, a critical step is the preclinical evaluation of drug cytotoxicity, efficacy, and efficiency. We proposed a patient-derived 3D preclinical model for drug evaluation that could mimic in vitro the patient’s disease. Surgically resected CRC tissue and adjacent healthy colon mucosa were decellularized by a detergent-enzymatic treatment. Scaffolds were recellularized with HT29 and HCT116 cells. Qualitative and quantitative characterization of matched recellularized samples were evaluated through histology, immunofluorescences, scanning electron microscopy, and DNA amount quantification. A chemosensitivity test was performed using an increasing concentration of 5-fluorouracil (5FU). In vivo studies were carried out using zebrafish (Danio rerio) animal model. Permeability test and drug absorption were also determined. The decellularization protocol allowed the preservation of the original structure and ultrastructure. Five days after recellularization with HT29 and HCT116 cell lines, the 3D CRC model exhibited reduced sensitivity to 5FU treatments compared with conventional 2D cultures. Calculated the half maximal inhibitory concentration (IC50) for HT29 treated with 5FU resulted in 11.5 µM in 3D and 1.3 µM in 2D, and for HCT116, 9.87 µM in 3D and 1.7 µM in 2D. In xenograft experiments, HT29 extravasation was detected after 4 days post-injection, and we obtained a 5FU IC50 fully comparable to that observed in the 3D CRC model. Using confocal microscopy, we demonstrated that the drug diffused through the repopulated 3D CRC scaffolds and co-localized with the cell nuclei. The bioengineered CRC 3D model could be a reliable preclinical patient-specific platform to bridge the gap between in vitro and in vivo drug testing assays and provide effective cancer treatment.
The application of nanosized inorganic UV filters in cosmetic field is limited by their high photocatalytic properties that could induce the degradation or dangerous transformation of the organic molecules in sunscreen formulations. To overcome this problem and simultaneously enlarge the window of filter's absorption, we propose the growth of bismuth titanates BiTiO into mesoporous silica nanoparticles (MSN). We investigated the chemical-physical properties by means of XRPD, TEM, UV-vis spectroscopy, N physisorption, XPS, and SF-ICP-MS analysis, while the influence on the environment was evaluated through photocatalytic tests. The growing process of this new nanosystem is discussed underlining the key role of the Bi ion that, acting as a low-melting point agent for the silica framework, led to a self-sealing mechanism. The excellent UV shielding properties combined with a radical suppression of the photocatalytic activity make the proposed nanosystem a perfect candidate for the development of the next generation nanomaterials for sunscreen formulations.
On the basis of known equations for calculating X‐ray diffraction intensities from a given number of unit cells of a crystal phase in polycrystalline material, as due to: (i) Bragg reflections; (ii) average diffuse scattering caused by thermal plus first‐kind disorder; and (iii) incoherent scattering, a relationship has been found that ties, in the Rietveld analysis, the Bragg scale factor to a scale factor for `disorder' as well as incoherent scattering. Instead of fitting the background with a polynomial function, it becomes possible to describe the background by physically based equations. Air scattering is included in the background simulation. By this means, the refinement can be carried out with fewer parameters (six fewer than when a fifth‐order polynomial is used). The DBWS‐9006PC computer program written by Sakthivel & Young [(1990), Georgia Institute of Technology, Atlanta, GA, USA] has been modified to follow this approach and it has been used to refine the crystal structures of the cubic form of Y2O3 and of α‐Al2O3. Peak asymmetry has been described by a function based on an exponential approximation. The results from refinements using polynomial physically based background function are, in terms of final structural parameters and reliability indices, very close to each other and in agreement with results reported in the literature. The reconstruction and optimization of the background scattering by means of physically based equations helps the implementation in the Rietveld code of other possible specific diffuse scattering contributions, such as that due to an amorphous phase.
Bismuth-based (nano)materials have been attracting increasing interest due to appealing properties such as high refractive indexes, intrinsic opacity, and structural distortions due to the stereochemistry of 6s2 lone pair electrons of Bi3+. However, the control over specific phases and strategies able to stabilize uniform bismuth-based (nano)materials is still a challenge. In this study, we employed the ability of bismuth to lower the melting point of silica to introduce a new synthetic approach able to confine the growth of bismuth-oxide-based materials into nanostructures. Combining in situ temperature-dependent synchrotron radiation X-ray powder diffraction (XRPD) with high-resolution transmission electron microscopy (HR-TEM) analyses, we demonstrate the evolution of a confined Bi2O3–SiO2 nanosystem from Bi2SiO5 to Bi4Si3O12 through a melting process. The silica shell acts as both a nanoreactor and a silicon source for the stabilization of bismuth silicate glass-ceramic nanocrystals keeping the original spherical shape. The exciton peak of Bi2SiO5 is measured for the first time allowing the estimation of its real energy gap. Moreover, based on a detailed spectroscopic investigation, we discuss the potential and the limitations of Nd3+-activated bismuth silicate systems as ratiometric thermometers. The synthetic strategy introduced here could be further explored to stabilize other bismuth-oxide-based materials, opening the way toward the growth of well-defined glass-ceramic nanoparticles.
The correlation functions of samples made up of three homogeneous phases, with a fixed geometrical configuration and different scattering densities, are linearly related among themselves. The same is true of the corresponding scattering intensities. The property holds approximately true if the phase boundaries of some of the previous samples are slightly modified. The analytical expressions of the coefficients involved in the relevant linear combinations are derived and applied to obtain the volume fractions and the scattering densities of the three phases of a coal from its small-angle scattering intensities collected during an extraction process
Complete sets of correction factors for absorption and air scattering effects in X-ray powder diffraction are reported. Both symmetrical reflection and transmission techniques are considered and boundary conditions to be tested for any given value of scattering angles are listed. This may prove particularly useful on coding computer programs for correction of raw intensity data files. Effects of interstitial volume on correction for absorption and subtraction of air scattering were investigated. For samples of high interstitial volume, like loosely packed powders or aerogels, the contribution from air trapped inside the specimen is significant and leads to expressions of the air scattering correction factors different from those commonly reported in the literature.
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