Synthesis and characterization of a lamellar hydroxyapatite/DNA nanohybrid

Two-dimensional layered materials exhibit desired functionalities when being used as gene delivery materials. In this study, a novel gene delivering vector, lamellar hydroxyapatite (HAp)/DNA nanohybrid was prepared. The structure of HAp/DNA nanohybrid was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fourier transform infrared (FT-IR) spectroscopy analysis revealed that ion-exchange occurred during the process. Gel electrophoresis analysis confirmed that the lamellar HAp could protect DNA from degradation of DNase I and the protected DNA could be recovered readily under acid conditions. Furthermore, the integrity of released DNA was confirmed by UV–vis spectra.     

Graphene/MnO2 hybrid nanosheets as high performance electrode materials for supercapacitors

Graphene/MnO₂ hybrid nanosheets were prepared by incorporating graphene and MnO₂ nanosheets in ethylene glycol. Scanning electron microscopy and transmission electron microscopy analyses confirmed nanosheet morphology of the hybrid materials. Graphene/MnO₂ hybrid nanosheets with different ratios were investigated as electrode materials for supercapacitors by cyclic voltammetry (CV) and galvanostatic charge–discharge in 1 M Na₂SO₄ electrolyte. We found that the graphene/MnO₂ hybrid nanosheets with a weight ratio of 1:4 (graphene:MnO₂) delivered the highest specific capacitance of 320 F g⁻¹. Graphene/MnO₂ hybrid nanosheets also exhibited good capacitance retention on 2000 cycles.     

Investigation into hybrid configuration in electrospun nafion/silica nanofiber

Organic–inorganic composites with nanostructure could exhibit a diverse range of multi-functional properties. In this study, nafion/silica composite nanofibers were successfully fabricated by using electrospinning technique with nafion coated surface. The tunable wettability of composite nanofiber was controlled by addition of nafion or flame-treatment. The thermal stability of nafion has been improved as it hybridized with silica nanofiber. Interestingly, the hydrophobic behavior still existed after heat-treatment with 500 °C for 2 h. The fire resistant property of composite nanofiber has been characterized. The effect of nafion polymer and post treatment on the morphology and wettability of composite nanofiber was evaluated. The mechanism of formation of nafion/silica composite nanofiber during electrospinning process has been proposed. The results of this study improve the understanding of the structure rearrange in organic–inorganic sols during high voltage field.     

Composite Ag/C:H:N films prepared by planar magnetron deposition

Composite Ag/C:H:N films were deposited by means of an unbalanced magnetron operated in a gas mixture of nitrogen and n-hexane. Composition of the films was controlled by electric power delivered to the magnetron and by ratio of nitrogen and n-hexane in the working gas mixture. The films were characterized using transmission electron microscopy, by the absorption spectra in visible and near infrared regions and by Fourier transform infrared spectroscopy. Immediately after film deposition and without breaking vacuum (in situ) corresponding vibration infrared spectra were scanned and their evolution during ageing of the films was monitored. Wettability as determined from water contact angle was improved with raising nitrogen contents, i.e. with increasing the electric power and the ratio of nitrogen/n-hexane in the working gas mixture. The increased wettability is likely caused by presence of NH_x groups in Ag/C:H:N films. The incorporation of nitrogen effectively prevents the formation of carboxylate groups on the silver inclusions surfaces during the aging in the open air. In addition, the oxidation mechanism of the polymer matrix is modified.     

Alginate hydrogel microbeads incorporated with Ag nanoparticles obtained by electrochemical method

An innovative method was developed for production of alginate hydrogel microbeads incorporated with silver nanoparticles (AgNPs) based on electrochemical synthesis followed by electrostatic extrusion. AgNPs were synthesized galvanostatically at different values of AgNO₃ concentration in the initial solution (0.5–3.9 mM), current density (5–50 mA cm⁻²), and implementation time (0.5–10 min). Increase in all of these parameters increased the concentration of AgNPs in alginate solution and was confirmed by TEM analysis and UV–vis spectroscopy. Cyclic voltammetry studies and Fourier transform infrared spectroscopy proved the alginate to be a good capping agent for the electrochemical synthesis of silver nanoparticles, due to coordination bonding between hydroxyl and ether groups, as well as ring oxygen atoms in uronic acid residues of alginate molecules, and Ag nanoparticles. Ag/alginate colloid solution was used for production of uniform hydrogel microbeads (with diameter of 487.75 ± 16.5 μm) by electrostatic extrusion technique. UV–vis spectroscopy confirmed retention and entrapment of AgNPs in microbeads during the production process. Alginate microbeads incorporated with AgNPs are attractive as biocompatible carriers and/or efficient donors of AgNPs as active components especially for potential biomedical applications, which was demonstrated by the antibacterial activity against Staphylococcus aureus.     

Study of pure and l-tartaric acid doped ammonium dihydrogen phosphate single crystals: A novel nonlinear optical non-centrosymmetric crystal

Single crystals of pure and l-tartaric acid (LTA) C₄H₆O₆ doped ammonium dihydrogen phosphate (ADP) (NH₄) H₂PO₄ were grown by slow evaporation solution technique (SEST) at ambient conditions. Powder X-ray diffraction (PXRD) analysis was carried out to confirm the crystal structure and no additional phase was observed due to doping except a systematic variation in peak intensities. Fourier transform infrared spectral analysis was done to examine the presence of various functional groups in the grown crystals. UV–VIS–NIR spectroscopic analysis was carried out to see the change in optical transparency of pure ADP and crystals due to LTA with different doping concentrations. Second harmonic generation (SHG) efficiency measurement was done to examine the enhancement in the nonlinear optical characteristics of the grown crystals. The effect of LTA dopant on crystal morphology, thermal and mechanical properties of ADP have also been presented in this paper. The above studies reveal the effect of incorporation of LTA into the lattice of ADP crystals.     

Nanoparticles assembly of boehmite nanofibers without a surfactant

Self-assembly of aluminum hydrate particles into larger boehmite (γ-AlOOH) nanofibers was illustrated by a facile hydrothermal method without using any surfactants. The size and morphology of boehmite nanofibers could be controlled by adjusting the pH value of the reaction mixture. The resulting products were characterized by XRD (X-ray diffraction), FTIR (Fourier transform infrared spectra), SEM (scanning electron microscopy), and TEM (transmission electron microscopy). The specific surface area and pore-size distribution of the obtained product as determined by gas-sorption measurements show that the boehmite nanofibers possess high-surface area and porosity properties. A possible formation mechanism of nanofibers via a nanoparticle assembly procedure is proposed based on the experiments under the different conditions.     

Investigation of microstructures and ultraviolet aging properties of organo-montmorillonite/SBS modified bitumen

Organo-montmorillonite(OMMT)/Styrene-butadiene-styrene(SBS) modified bitumen nanocomposites were prepared by melt blending. The microstructures of OMMT/SBS modified bitumen were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM), respectively. The effect of OMMT on ultraviolet (UV) aging properties of SBS modified bitumen was investigated. FTIR and XRD analyses indicate that the OMMT/SBS modified bitumen forms an intercalated structure. It is observed that the phase contrast between the dispersed domains and the matrix is inverted in SBS modified bitumen, which is decreased with the introduction of OMMT according to AFM analysis. As a result of UV aging, both viscosity aging index and softening point increment of OMMT/SBS modified bitumen decrease significantly. There is a single phase trend in the morphology of the bitumen after aging, which is accelerated by the existence of SBS. However, these changes can be effectively prevented under the influence of OMMT, indicating the good UV aging resistance of OMMT/SBS modified bitumen.     

Ferroelectric and magnetic studies on unpoled Poly (vinylidine Fluoride)/Fe3O4 magnetoelectric nanocomposite structures

The fabrication of flexible Poly (vinylidine Fluoride)/Fe₃O₄ magnetoelectric nanocomposite films with different weight fractions of Fe₃O₄ nanoparticles is explained in this paper. The effects of nano Fe₃O₄ content on the structural, chemical, thermal, and magnetoelectric properties of PVDF matrix are discussed. XRD and FTIR results reveal the interaction between the filler and the matrix and also they suggest that the β phase contribution can be significantly controlled by the inclusion of nano Fe₃O₄. Thermal stability and melting point behavior of the composite films are investigated through TG/DTA. The existence of ferrimagnetism and ferroelectric properties in the films are proved through the magnetization and polarization studies. The hysteresis loops show the largest polarization and magnetization values at 0.14 wt% of Fe₃O₄. Also, the dependence of ferroelectric polarization on temperature is investigated and reported.     

Raman spectroscopy and cathodoluminescence characteristics of order-disorder Ba(Zn1/3Ta2/3)O3 ceramics

The order-disorder transition in Ba(Zn_1/3Ta_2/3)O₃ (BZT) was characterized by using Raman spectroscopy, transmission electron microscopy (TEM), and cathodoluminescence (CL) microscopy. The 1:2 ordered structure of pure BZT ceramics was replaced by a 1:1 ordered structure at 1650 °C and the 1:1 ordered structure of BZT sintered at 1650 °C exhibited a 1:2 ordered structure when it was reannealed at 1500 °C for 12 h. The A_1g lines in the Raman spectrum of the sintered and reannealed samples were shifted to lower and higher wavenumbers, respectively. From the CL analysis, the 1:1 ordered BZT exhibited mainly three emission bands at around 533.2 (2.32 eV), 599.1 (2.07 eV), and 682.1 nm (1.81 eV), whereas the 1:2 ordered BZT exhibited mainly five bands at 346.4 (3.58 eV), 427.5 (2.90 eV), 520.9 (2.38 eV), 593.0 (2.09 eV), and 678.9 nm (1.82 eV). The strongest band originating from 2.32 to 2.38 eV was broadened, and the band center shifted towards a higher and lower wavelength in the 1:1 and 1:2 ordered BZT, respectively. Additional bands at around 346 and 427 nm in the grain interior of the annealed sample were strongly related to the 1:2 ordering of BZT.     

Deposition of hydroxyapatite thin films by Nd:YAG laser ablation: a microstructural study

Hydroxyapatite (HA) thin films has been successfully deposited by Nd:YAG laser ablation at λ = 532 nm. The morphology and microstructure of the deposited layers was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). Polycrystalline HA films were directly obtained with the substrate at 300 °C and without introducing water vapors in the deposition chamber. Electron paramagnetic resonance (EPR) measurements show that the oxygen stoichiometry in the HA films is also maintained. Depositions performed at λ = 335 nm laser wavelength and 300 °C substrate temperature resulted in polycrystalline layers of mixed composition of HA and tricalciumphosphate (TCP).     

Synthesis and characterization of microporous titanosilicate ETS-10 obtained with different Ti sources

Titanosilicate ETS-10 crystals were prepared by hydrothermal synthesis varying Ti source (TiCl₃ and commercial TiO₂-anatase), time in autoclave and seeding with previously prepared ETS-10 crystals. The crystalline powders were characterized by X-ray diffraction, N₂ adsorption, thermogravimetric analysis, and scanning and transmission electron microscopies. Control of the particle size of ETS-10 crystals ranging from 0.32 μm × 0.41 μm to 16.4 μm × 32.5 μm was successfully achieved varying the seeding and synthesis conditions. In particular, it was found that the use of TiO₂-anatase alone or together with TiCl₃ promotes heterogeneous primary nucleation. Transmission electron microscopy demonstrated that the largest crystals obtained here were twinned.     

Thermal behavior of the amorphous precursors of the ZrO2-SnO2 system

Thermal behavior of the amorphous precursors of the ZrO₂-SnO₂ system on the ZrO₂-rich side of the concentration range, prepared by co-precipitation from aqueous solutions of the corresponding salts, was monitored using differential thermal analysis, X-ray powder diffraction, Raman spectroscopy, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectrometry (EDS). The crystallization temperature of the amorphous precursors increased with an increase in the SnO₂ content, from 405 °C (0 mol% SnO₂) to 500 °C (40 mol% SnO₂). Maximum solubility of Sn⁴⁺ ions in the ZrO₂ lattice (∼25 mol%) occurred in the metastable products obtained upon crystallization of the amorphous precursors. A precise determination of unit-cell parameters, using both Rietveld and Le Bail refinements of the powder diffraction patterns, shows that the incorporation of Sn⁴⁺ ions causes an asymmetric distortion of the monoclinic ZrO₂ lattice. The results of phase analysis indicate that the incorporation of Sn⁴⁺ ions has no influence on the stabilization of cubic ZrO₂ and negligible influence on the stabilization of tetragonal ZrO₂. Partial stabilization of tetragonal ZrO₂ in products having a tin content above its solid-solubility limit was attributed to the influence of ZrO₂-SnO₂ surface interactions. In addition to phases closely structurally related to cassiterite, monoclinic ZrO₂ and tetragonal ZrO₂, a small amount of metastable ZrSnO₄ phase appeared in the crystallization products of samples with 40 and 50 mol% of SnO₂ calcined at 1000 °C. Further temperature treatments caused a decrease in and disappearance of metastable phases. The results of the micro-structural analysis show that the sinterability of the crystallization products significantly decreases with an increase in the SnO₂ content.     

The influence of sucrose on the crystallization behaviour in the system CaO-SiO2-C12H22O11-H2O under hydrothermal conditions

Hydrothermal synthesis in the presence of sucrose has been carried out at 200 °C and autogeneous pressure in the system CaO-SiO₂-C₁₂H₂₂O₁₁-H₂O to investigate the influence of C₁₂H₂₂O₁₁ on phase formation and the crystal habit of calcium silicate hydrates (CSH-phases). A sucrose/lime ratio of 0.5 was utilized in all experiments and the reactivity of the SiO₂ source was varied using educts of different grain size of ∼40 mesh and >230 mesh. CaO/SiO₂ concentration ratios of 0.5 and 0.8 have been selected, the latter with respect to the composition of the important CSH-phase 11 Å tobermorite. The results were compared with experiments under similar but sucrose-free conditions. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX-analysis) as well as Fourier transform infrared spectroscopy (FTIR-spectroscopy) have been applied for analyses.A retarding effect of sucrose on CSH-phase formation has been observed. Only minor amount of CSH without regular morphology was observed instead of typically fibrous 11 Å tobermorite formed in the sucrose-free system. Sucrose altered the reaction mechanism in the CSH-system and hydrothermal process started with rapid reaction of sucrose and lime. The further course of crystallization was dominated by an extended precipitation of calcium carbonate and small amounts of calcium oxalate hydrate. Formation of these stable hydrothermal decomposition products of saccharated lime is strongly suppressing the CSH-crystallization.     

Direct observation of the intergrown α-phase in β-TmAlB4 via high-resolution electron microscopy

A TmAlB₄ crystal with a ThMoB₄-type (β-type) structure phase related to a hexagonal AlB₂-type structure was studied by electron diffraction and high-resolution electron microscopy. A high-resolution image clearly exhibits an intergrown lamellar structure of a YCrB₄-type (α-type) phase in the matrix of the β-type phase in TmAlB₄ crystal. The lamellar structure can be characterized by a tiling of deformed hexagons, which are a common structure unit in the α-type and β-type structures. The intergrown nanostructure is considered to be attributed to the origin of low temperature anomalies in physical properties.     

Electrochemical fabrication of ordered Ag2S nanowire arrays

We have successfully fabricated ordered crystalline Ag₂S nanowire arrays by direct current electrodeposition into the nanochannels of porous anodic aluminum oxide templates from a dimethylsulfoxide solution containing AgNO₃ and elemental S. X-ray diffraction and the selected area electron diffraction investigations demonstrate that the Ag₂S nanowires are a uniform actanthite structure. Electromicroscopy results show that the nanowires are quite ordered with diameters of about 40 nm and lengths up to 5 μm. X-ray energy dispersion analysis indicates that the atomic composition of Ag and S is very close to a 2:1 stoichiometry. Furthermore, a possible mechanism for the formation of the Ag₂S nanowires is proposed.     

Control of growth orientation and shape for epitaxially grown In2O3 nanowires on a-plane sapphire

Vertically aligned indium oxide nanowires were grown on a-plane sapphire substrate by the method of catalyst-assisted carbothermal reduction. The morphology and crystal structure of the nanowires are determined by X-ray diffraction, transmission electron microscopy and field-emission scanning electron microscopy. Two types of In₂O₃ nanowires were found by controlling the growth conditions. The nanowires with a hexagonal cross-section were shown to grow in [1 1 1] direction, whereas those with a square cross-section grow in [0 0 1] direction. In addition to the temperature effects, the concept of supersaturation in Au catalyst is proposed to explain the formation of these two types of nanowires. Besides, tapering, which is explained with the interplay between the vapor-liquid-solid and vapor-solid growth mechanisms, is observed in the nanowires.     

Study of a new resin-based composites containing hydroxyapatite filler using Raman and infrared spectroscopy

The degree of conversion of polymeric matrix in hydroxyapatite-containing dental fillings by Raman and infrared spectroscopy has been determined. Resin-based dental composites are one of the most popular filling materials used in dentistry. These light-cured materials are characterized by the value of the degree of conversion, which depends on curing time and influences the quality of obtained dental filling. Distribution of the filler into polymeric matrix, which has a significant impact on the properties of the final product, has been determined by Raman mapping. The applied procedure also has allowed to present the changes of the degree of conversion on the examined surfaces. The results of the study demonstrate the versatility of the Raman spectroscopy as the analytical spectroscopic technique for determining chemical properties of dental fillings and providing insight into their organization at the microstructural level. The obtained degree of conversion values have been compared with data for the commercially available dental fillings characterized by other authors.     

Depth-profiling of phase composition and preferred orientation in a graded alumina/mullite/aluminium-titanate hybrid using X-ray and synchrotron radiation diffraction

X-ray diffraction (XRD), grazing-incidence synchrotron radiation diffraction (GISRD) and multi-wavelength synchrotron radiation diffraction (MWSRD) have been successfully used for near-surface depth profiling of phase composition and texture in a functionally-graded alumina/mullite/aluminium-titanate hybrid prepared by an infiltration process. Depth profiling of near-surface information both in the nanometer and micrometer scale has been done by (a) varying the X-ray wavelength, (b) varying the grazing-incidence angle, and (c) gradual polishing of the sample surface with diamond lap. Results show a distinct gradation in the phase abundance near the surface of the hybrid sample. The distribution of mullite near the surface is highly textured and shows a distinct depth-dependent gradation in preferred grain-orientation. The unique but powerful capability of XRD, GISRD and MWSRD as complementary tools for depth profiling the near-surface region of graded materials has been demonstrated in this work.     

GexNbSe2 and GexNbS2 intercalation compounds

The structures of two intercalation compounds, Ge_∼0.2NbSe₂ and Ge_∼0.3NbS₂ were investigated by single crystal X-ray diffraction and electron microscopy (selected area electron diffraction (SAED), high resolution electron microscopy (HRTEM) and X-ray microanalysis by energy dispersive spectroscopy (XEDS)). Crystal structure determinations of the average structure of the intercalation compounds 2H-Ge_0.217NbSe₂ and 4H-Ge_0.288NbS₂ are reported: the selenide compound crystallizes in the space group P6₃/mmc with a = 3.4560(9) Å and c = 12.966(3) Å and adopts the 2H-NbSe₂ structure-type, while the sulfide compound crystallizes in the P6₃mc space group, with a = 3.3392(9) Å and c = 25.404(7) Å with a structure-type 4H_c-NbS₂ which it is known for TaSe₂. In both structures the germanium atoms are located in the empty octahedral positions of the van der Waals gap between the NbX₂ (X = S, Se) layers. Electron diffraction patterns from several Ge_xNbSe₂ crystal flakes show different superstructures and exhibit diffracted diffuse intensity: weak satellites corresponding to and 2a₀ × 2a₀ superstructures were observed for x ∼ 0.15 (a₀ is the basal lattice parameter of the host structure). For x ∼ 0.25-0.33, the same type of satellite is observed with a stronger intensity. For x ∼ 0.5 only satellites corresponding to the superstructure were present. In the case of Ge_xNbS₂, with 0.10 < x < 0.25, the germanium atoms are ordered in domains with an superstructure. In some crystals disorder along the c-axis has been observed.