[show abstract][hide abstract] ABSTRACT: The “build-up” methodology of a composite photocatalyst is a critical issue regarding the showed photocatalytic performance, including the formation of intermediates. To investigate this issue P25/WO3/Au composites were obtained by impregnation (WO3) and subsequent photoreduction (Au) with UV or visible light. The obtained composites’ photocatalytic activity and intermediate formation profiles were evaluated using phenol as a model pollutant. XPS/UPS and DRS methods were used to uncover local coordination, surface chemistry (of the different types of atoms (Ti, W, O and Au) and the band-structure (band-gap, possible electron transitions) of the obtained nanomaterials. The intermediates’ evolution profile and structural peculiarities were successfully correlated and it was shown that each minor structural (bulk or surface) change has a significant impact on the photocatalytic activity and intermediate formation dynamics.
Applied Catalysis B Environmental 01/2014; 147:508-517. · 5.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: The study is focused on synthesis, investigation of the structural and morphological changes induced by MoO3 addition and thermal treatment, as well as in vitro characterization of a new sol-gel derived SiO2 -CaO-P2 O5 bioactive materials. The obtained systems are composite materials consisting of nanocrystalline apatite, bioactive glass and CaMoO4 nanoparticles, which are of interest for both regenerative medicine and specific medical applications of the releasable molybdenum ions. The changes induced by the thermal treatments and MoO3 addition with respect to the structure and morphology were completed using DTA\TGA, XRD, SEM, EDX, XPS, FTIR, EPR and BET. The biological performance of these materials was evaluated in vitro by performing bioactivity and biocompatibility tests. The bioactive properties in terms of HAp layer formation on the biomaterial surface after SBF immersion were studied by XRD and SEM. In order to establish their biocompatibility, the biomaterials surface was functionalized with protein and the resulted sample was investigated using SEM, FTIR and XPS. The obtained results suggest that the addition of molybdenum oxide in proper concentration improves the biocompatibility in terms of enhancement of protein adherence on Si-Ca-P surface due to CaMoO4 crystalline phase development and does not inhibit bioactivity.
Journal of Biomedical Materials Research Part A 10/2013; · 2.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: The biocompatibility of nanostructured titanosilicate microspheres with different Ti/Si
ratios was evaluated by probing the affinity of horse haemoglobin (Hgb) towards the
samples surface, in terms of quantitative and conformational changes analysis. The samples
morphology before and after protein adsorption was evaluated by Scanning Electron
Microscopy (SEM). X-ray Photoelectron Spectroscopy (XPS), Electron Paramagnetic
Resonance (EPR) on spin labeled protein and Fourier Transform Infrared (FTIR)
spectroscopies were further used to achieve information concerning both the amount of
attached haemoglobin and its secondary structure modifications upon adsorption. The
obtained results suggest that nanostructured titanosilicate microspheres present a friendly
surface for protein adsorption and an enhanced protein adherence with increase of silica
Journal of Molecular Structure 07/2013; 1044. · 1.40 Impact Factor
[show abstract][hide abstract] ABSTRACT: The effects of gamma radiation on the local structure of PVA membranes containing TiO2 were investigated
by ESR and XRD methods. An intense ESR signal is observed after irradiation at 16 KGy dose. This signal
appears only for irradiated samples and it is associated with the breaking of the polymeric chain, followed
by local reorganization of the polymeric segments and the apparition of the unpaired electrons and free
radicals. The intensity of the signal decreases with the concentration of TiO2, indicating a shielding effect of
the dopand. That the modification of local order of the polymeric chains has been modified after irradiation
is confirmed by XRD method.
Central European Journal of Physics 06/2013; · 0.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: Fourier transform infrared (FTIR) and electron paramagnetic resonance (EPR) spectroscopic data obtained for iron doped silica-bismuthate glasses were used to investigate the changes induced in the local structure of samples as the ratio between Bi2O3 and SiO2 content changes from 3 to 0.66. The environment of constituent cations was investigated both in vitreous and partially crystallized samples of same composition. Progressive substitution of Bi2O3 by SiO2 contributes to the structural relaxation of vitreous network and enhances glass stability. By crystallization heat treatment the structural units appear to be more uniform as it results from the narrowing of corresponding IR bands and EPR lines. FTIR data show that more affected by composition and heat treatment is the environment of bismuth than that of silicon. EPR data indicate an ordering tendency with SiO2 content in glasses, while in vitroceramics the iron environment is much uniform in samples with less SiO2 content, where Bi12SiO20 phase is developed.
Journal of Non-Crystalline Solids 04/2013; Journal of Non-Crystalline Solids:2947-2951. · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: Aluminosilicate microspheres obtained by spray drying were investigated in prospect of their potential biomedical applications. The as-prepared microspheres are amorphous. TEM and AFM were used to examine the morphology of the samples before and after immersion in simulated body fluid (SBF). The local structure changes as a function of microspheres composition and due to their immersion in SBF were investigated by 29Si and 27Al MAS–NMR. After SBF immersion, the silica network partially depolymerised by hydration/hydroxylation and the completely changed aluminium environment suggest a phylosilicate-like structure. 31P MAS–NMR analysis evidenced phosphorus ions incorporated in a new crystalline phase developed during SBF immersion.Highlights► Aluminosilicate microspheres less than 20 μm were prepared by spray drying. ► Microspheres structure is modified after immersion in simulated body fluid (SBF). ► Silica network is partially depolymerized by hydration/hydroxylation in SBF. ► After SBF immersion the aluminum environment is completely changed. ► Apatite type nanocrystals grown on microspheres in SBF mark their bioactivity.
[show abstract][hide abstract] ABSTRACT: Titania/tungsten (VI) oxide/noble metal (gold and platinum) composites were obtained by the means of
selective noble metal photodeposition on the desired oxide’s surface (either on TiO2 or on WO3). The
noble metal particles’ localization was proved by SEM-EDX, while their size with DRS and TEM. The
influence of the noble metal nanoparticles’ position was investigated successfully on the light absorption
properties, photocatalytic activity toward oxalic acid and photocatalytic hydrogen production. Major
differences were observed in the photocatalytic performance of the catalysts in which only the position
of the noble metal was changed. Consequently, highly active composites were obtained, that surpassed
the reference catalysts’ (TiO2(Au), TiO2(Pt), WO3(Au), WO3(Pt)) oxalic acid degradation yield and were
also quite active for photocatalytic hydrogen production
[show abstract][hide abstract] ABSTRACT: The study aims to characterize surface properties of aluminosilicate
microspheres incorporating yttrium, with potential biomedical
applications. Micrometric particles of spherical shape were obtained by
spray drying method. The behavior of aluminosilicate microspheres
without yttrium and with yttrium was investigated under in vitro
conditions, by seven days incubation in simulated body fluid (SBF). The
surface elemental composition and the atomic environments on outermost
layer of the microspheres, prior to and after incubation in SBF were
evaluated by X-ray photoelectron spectroscopy (XPS) in order to
investigate their bioactivity. The results were analyzed to underline
the effect of yttrium addition on surface properties of the
aluminosilicate microspheres and implicitly on the behavior of the
samples in simulated body environments.
[show abstract][hide abstract] ABSTRACT: The aim of the present study was to synthesize by spray drying titanosilicate microspheres of less than 5 μm in diameter and to induce by thermal treatment the growth of nanocrystalline phases in amorphous matrices. The microspheres obtained by this process belong to the xTiO2:ySiO2 system, with x:y ratios of 1:2, 1:1 and 2:1, doped with 1% Gd2O3. Anatase and rutile nanocrystals were developed by increasing the calcination temperature from 700 to 1100 °C, and both are desired phases concerning their applications. Structural and surface characterization before interaction with biological and/or environmental media are an important issue for the expected behaviour in such milieus. The changes induced by the thermal treatments with respect to structure, morphology and Ti/Si ratio on the surface of the samples were investigated using thermogravimetrical (TGA), differential thermal analyses (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Surprisingly, for as-prepared microspheres the surface atomic composition relative to Ti and Si is quite similar for all three systems, while for the heat treated samples the Si content increases, that reflects that the developed titania nanocrystals are covered by a thin layer of amorphous silica.
Materials Chemistry and Physics. 08/2012; 135(2-3):863–869.
[show abstract][hide abstract] ABSTRACT: A comprehensive analysis of heterogeneous nanostructures based on TiO2 aerogels and Ag nanoparticles (NPs) is reported herein. The experimental techniques engaged along this study enable a multi-scale approach for the characterization of this composite system. The results clearly indicate that an increase of the Ag amount within the porous structure of TiO2 nanograins leads to a lower dispersion of Ag on the support. For a higher Ag global amount, the proportion of encapsulated NPs increases considerably, reducing in this manner the amount of accessible Ag. The effect of the thermal treatment on such nanostructures has been evaluated as well. The specimen annealing appears to induce a considerable diminution of the microporosity, finding that is in good agreement with the results obtained by measurement of the specific surface area of the TiO2 grains. The annealing also changes the microstructural characteristics of these nanostructures, as expected. More specific, it leads to an enhanced degree of encapsulation of Ag NPs, which as consequence become considerably less accessible. Being focused on the analysis of porous nanocomposites with specific properties, the current investigation aims as well at emphasizing the remarkable potential of electron tomography, a technique that can be successfully employed for precise analysis of three dimensional nanostructures.
[show abstract][hide abstract] ABSTRACT: Noncrystalline and nanocomposite materials of (1-x)SiO2�xGeO2 system, with Si:Ge ratio from 8:1 to 2:1(x = 0.111; 0.142; 0.2; 0.333), initially obtained by sol–gel method, were characterized by thermal analyses, X-ray
diffraction, nuclear magnetic resonance and Raman spectroscopy. According to DTA and XRD results, the noncrystalline state of the as-prepared samples is stable up to 1,000 �C and only after 30 min heat treatment at 1,200 �C the samples become partial crystalline, due to development of cristobalite and quartz nanocrystals. Solid-state 29Si MAS-NMR was employed in order to characterize the local structure around silicon as a function of composition and thermal history of the samples. The NMR data indicate the presence of Q2, Q3 and Q4 units in all samples. The fraction of the highly interconnected SiO4 tetrahedra
increases both with germanium content and with annealing temperature. The Raman spectroscopy results evidence structural changes related to silicon- and germanium-oxygen units but also to their interconnection, that depend on Si:Ge ratio and annealing temperature.
Journal of Sol-Gel Science and Technology 05/2012; 63:425-434. · 1.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Functional protein adsorption at liquid–solid interfaces has been intensively studied in the last years, however it is difficult to evidence directly conformational changes of the protein which are likely to appear upon adsorption. Spin labeling in combination with Electron Paramagnetic Resonance (EPR) spectroscopy was applied in this study to investigate adsorption of horse methemoglobin to bioactive glass (BG) similar in composition with 45S5 Bioglass®. X-band cw-EPR spectra of spin labeled methemoglobin in solution were compared to those obtained after adsorption on bioactive glass surface (functionalized and non-functionalized with glutaraldehyde), to extract information of the structure and dynamics in the vicinity of position β-93. The concentration of methemoglobin adsorbed on BG substrate was determined from the intensity of cw-EPR spectra and correlated with images obtained by Scanning Electron Microscopy (SEM). Line shape analysis of the EPR spectra revealed that ionic strength does not induce significant conformational changes in the protein structure upon adsorption, however, the chemical treatment applied to the bioactive glass surface positively influences protein adsorption.
Journal of Molecular Structure 05/2012; 1015:20. · 1.40 Impact Factor
[show abstract][hide abstract] ABSTRACT: Adsorption and structural changes that occur upon interaction between methemoglobin (MetHb) and 5-methyl-aminomethyl-uridine forming enzyme (MnmE) with the surface of a bioactive glass (BG) were investigated by Fourier Transform Infrared (FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The effect of glutaraldehyde (GA) as a coupling agent for protein adsorption on BG was also investigated. The comparative analysis of FTIR spectra recorded from lyophilized proteins and from bioactive glass surface after protein adsorption was considered in order to obtain information about the changes in the secondary structure of the proteins. XPS data were used to determine the surface coverage. The unfolding of adsorbed proteins due to interactions between the internal hydrophobic protein domains and the hydrophobic BG surface was evidenced. After adsorption, the amount of α-helix decreases and less ordered structures (turns, random coils and aggregates) are preponderant. These changes are less pronounced on the BG functionalized with GA, suggesting that the treatment with GA preserves significantly larger amounts of α-helices in the structure of both proteins after adsorption.
Biochimica et Biophysica Acta 05/2012; 1824(7):873-81. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: The study is focussed on synthesis and characterisation of a new sol-gel derived composite system consisting of nanocrystalline apatite, bioactive glass and gold nanoparticles, which are of interest both for regenerative medicine and for specific medical applications of the releasable gold nanoparticles. Samples dried at 110°C and then heat treated for 30 min at 300 and 500°C were investigated by thermal analysis (DTA/TG), X-ray diffraction (XRD), UV-VIS-NIR, Fourier Transform Infrared (FTIR) spectroscopy, X-ray Photoelectron(XPS) spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Gold nanoparticles and nanocrystalline apatite are developed already after heat treatment at 300°C. XPS analysis clearly revealed the presence of both metallic and ionic gold species. The development of gold nanoparticles was evidenced by UV-VIS-NIR and TEM analysis, and their size increased from few nanometers to 25 nm by increasing the treatment temperature from 300 to 500°C. The bioactivity of the samples immersed in simulated body fluid was demonstrated by XRD and SEM results.
Journal of Materials Science Materials in Medicine 03/2012; 23(5):1193-201. · 2.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this study are reported results obtained from the structural, morphological and textural investigations of 56SiO2∙(40-x)CaO·4P2O5·xAg2O system, where 0≤x≤10mol%. The samples obtained by sol–gel method were annealed and then characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), vibrational spectroscopy (Raman, FTIR), N2-adsorption measurements, and transmission electron microscopy (TEM). XRD patterns of the investigated samples exhibit tricalcium phosphate (TCP) nanostructured phase and show the existence of metallic silver as dispersed phase. The presence of apatite-like phase is underlined by the recorded Raman and especially FT-IR spectra. TEM pictures indicate the presence of silver nanoparticles of almost spherical shapes and various sizes inside the matrix, depending on the Ag2O content. Regarding the textural properties, it was observed both a decrease of the specific surface area as well as a progressive change of the mesoporous characteristics with the silver addition, the latter behavior recommending the potential use of these samples for applications, where the morphology control is required.
[show abstract][hide abstract] ABSTRACT: There is much interest in silver containing glasses for use in bone replacement owing to the demonstrated antibacterial effect. In this work, 2 and 8 mol % of silver was added during the sol-gel process to the composition of a bioactive glass belonging to CaO-SiO(2 -P(2)O(5) system. The samples were characterized by means of ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques to demonstrate that the silver is embedded into the glass matrix as nanoparticles. Bioactivity test in simulated body fluid proved that the presence of silver in the bioactive glass composition, even in high amount, preserve or even improve the bioactivity of the starting glass, and consequently, leads to the carbonated apatite formation, which is the prerequisite for bioactive materials to bond with living bones. Complementary information proving these findings were delivered by performing X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and XPS measurements. The presence of silver also improves protein binding capability to the bioactive glass surface as demonstrated by cw-electron paramagnetic resonance experiments and XPS measurements.
Journal of Biomedical Materials Research Part A 02/2012; 100(5):1179-86. · 2.83 Impact Factor