Facile preparation of Ag/ZnO nanoparticles via photoreduction

Ag/ZnO nanoparticles can be obtained via photocatalytic reduction of silver nitrate at ZnO nanorods when a solution of AgNO₃ and nanorods ZnO suspended in ethyleneglycol is exposed to daylight. The mean size of the deposited sphere like Ag particles is about 5 nm. However, some of the particles can be as large as 20 nm. The ZnO nanorods were pre-prepared by basic precipitation from zinc acetate di-hydrate in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide. They are about 50–300 nm in length and 10–50 nm in width. Transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDS), X-ray powder diffraction (XRD), UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) were used to characterize the resulting Ag/ZnO nanocomposites.     

Synthesis and characterization of pure anatase TiO<Subscript>2</Subscript> nanoparticles

Pure anatase TiO₂ nanoparticles were synthesized by microwave assisted sol–gel method and further characterized by powder X-ray diffraction (XRD), energy dispersive x-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Visible spectrophotometer, SEM images showed that TiO₂ nanoparticles were porous structure. The XRD patterns indicated that TiO₂ after annealed at 300 °C for 3 h was mainly pure anatase phase. The crystallite size was in the range of 20–25 nm, which is consistent with the results obtained from TEM images. Microwave heating offers several potential advantages over conventional heating for inducing or enhancing chemical reactions.     

Preparation,surface properties,and MC3T3-E1 cell response of mesoporous hydroxyapatite thin films

Mesoporous hydroxyapatite (meso-HA) thin films were fabricated by a sol–gel method using cetyltrimethyl ammonium bromide as the template. The phase, surface morphology, and mesoporous structure of the meso-HA films were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The uniform thin films consisted of meso-HA spherical particles with different pore size (2.0 or 3.1 nm) were prepared on the glass substrate at different pH value (pH 3.0 or 7.0). The introduction of mesopores would enhance the surface area of HA. Water contact angle was also measured on the non-mesoporous and meso-HA thin films, revealing the promotion of surface wettability in the mesoporous ones. In vitro cytocompatibility of HA films were evaluated by cell adhesion and proliferation tests using MC3T3-E1 cells. After 3 days of culture on the samples, the cells spread in an elongated shape and were well adhered to the surface of the meso-HA films. Moreover, the cells proliferation on the meso-HA films was higher than that on the non-mesoporous films. There are significant differences in the cell density between the control group and the meso-HA films with the pores sized in 2.0 nm after being cultured for 2 and 3 days (P < 0.05). The results suggested that the presence of mesopores could influence the surface and biological properties of HA films, and the mesoporous structure would enhance the cell response of HA.     

Structural study of Li<Subscript>2</Subscript>MnO<Subscript>3</Subscript> by electron microscopy

Detailed crystallographic data on high-quality Li₂MnO₃ material has been obtained using a combination of X-ray diffraction (XRD), selected-area electron diffraction (SAED), high-resolution electron microscopy (HREM), and 0.1 nm probe high-angle annular dark-field imaging (HAADF) in a scanning transmission electron microscope. A high-purity Li₂MnO₃ powder was annealed at 950 °C for 3 days to obtain predominantly defect-free grains which average size was 3.0 ± 1.5 μm. Rietveld refinement indicated that the C2/m spacegroup provided the best fit for the XRD data. Electron diffraction patterns obtained along various zone axes, on defect-free oxide particles, could be uniquely indexed to the monoclinic structure. HREM and HAADF images of defect-free grains were consistent with a Li–Mn–Mn– arrangement, i.e., lithium ordering in the transition metal planes. Low-magnification TEM images occasionally revealed stacking defects within oxide particles. HREM images of sample areas containing defects revealed a low density of stacking faults within the monoclinic sequence, resulting in a trigonal P3 ₁ 12 local arrangement.     

Biomineralizing synthesis of mesoporous hydroxyapatite–calcium pyrophosphate polycrystal using ovalbumin as biosurfactant

Mesoporous polycrystals of hydroxyapatite–calcium pyrophosphate (HA–CPP) are synthesized via a biomineralizing route using ovalbumin as natural biosurfactant. The mesoporous structure of HA–CPP is characterized by means of X-ray diffraction (XRD), N₂ adsorption–desorption isotherms (NADI), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), atom force microscopy (AFM), polarization microscopy (PLM) and stereomicroscopy. The results show that the crystalline grains with an average diameter of 13.2 nm are uniformly distributed along the protein molecule chains, and this results in microsphere-like particles with diameters of 200–300 nm. The highly ordered pores involved in microspheres are found to be approximately 6.6 nm by small-angle XRD. The formation of lyotropic calcium liquid crystal (CLC) plays a key role in the formation and stabilization of the mesoporous structure. A schematic illustration is used to reveal the mechanism of protein-medicated HA–CPP biomineralization, which employs the protein tertiary structure to explain the formation of the porous particles.     

Nanocrystalline TiO2 thin films for NH3 monitoring: microstructural and physical characterization

Nanocrystalline titanium oxide thin films have been deposited by spin coating technique and then have been analyzed to test their application in NH₃ gas-sensing technology. In particular, spectrophotometric and conductivity measurements have been performed in order to determine the optical and electrical properties of titanium oxide thin films. The structure and the morphology of such material have been investigated by X ray diffraction, Scanning microscopy, high resolution electron microscopy and selected area electron diffraction. The X-ray diffraction measurements confirmed that the films grown by this technique have good crystalline tetragonal mixed anatase and rutile phase structure. The HRTEM image of TiO₂ thin film showed grains of about 50–60 nm in size with aggregation of 10–15 nm crystallites. Selected area electron diffraction pattern shows that the TiO₂ films exhibited tetragonal structure. The surface morphology (SEM) of the TiO₂ film showed that the nanoparticles are fine with an average grain size of about 50–60 nm. The optical band gap of TiO₂ film is 3.26 eV. Gas sensing properties showed that TiO₂ films were sensitive as well as fast in responding to NH₃. A high sensitivity for ammonia indicates that the TiO₂ films are selective for this gas.     

Synthesis and characterization of ordered and cubic mesoporous silica crystals under a moderately acidic condition

Ordered and cubic mesoporous silica materials were synthesized by using poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer as template under a moderately acidic condition of 0.5 mol/l HCl solution. These mesoporous materials were characterized by Fourier transform (FT) IR spectroscopy, thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption measurements. The three-dimensional cage-like microporosity of the prepared mesoporous silica having ordered hexagonal mesoporous structure was evidenced by the well-defined XRD patterns combined with TEM photographs. SEM observation shows a highly regular cubic crystal structure for the prepared mesoporous silica. The size of these crystallites was maintained within the range between 4 and 6 μm, which is fairly important for the application to the stationary phase for separation. The nitrogen adsorption–desorption analysis reveals that the prepared mesoporous silica possesses a small pore diameter of 3.68 nm, a total surface area of 363.648 m²/g, a total pore volume of 0.379 cm³/g, and a pore-wall thickness of 6.63 nm. These features may lead to higher thermal and hydrothermal stability, excellent microporosity, and good connectivity. The mesoporous silica prepared in this study exhibits potential applications to catalysis, sensoring, and separation.     

Synthesis, characterization, and evaluation of lubrication properties of composites of ordered mesoporous carbons and luminescent CePO4:Tb nanocrystals

Having new potential applications in forging processes in mind, composites of an ordered mesoporous carbon and luminescent metal phosphate nanocrystals were synthesized for the first time. Three kinds of CMK-3/CePO₄:Tb nanocomposites were prepared by treating a mesoporous CMK-3 host with different lanthanide phosphate precursor solutions. Characterization of the obtained nanocomposites by small-angle X-ray scattering, wide-angle X-ray diffraction, transmission electron microscopy, thermogravimetry, and nitrogen physisorption analysis showed that in two cases, the nanocrystals (ca. 2–3 nm in size) were located inside the mesopores, whereas in the third case the nanocystals (ca. 6 nm in size) merely adhered to the outer surfaces of the carbon particles. The CMK-3 and the two nanocomposites had ordered hexagonal structures (space group p6mm); all the materials possessed amorphous carbon walls. After combustion of the nanocomposites, the residues upon excitation with UV light exhibited the typical green luminescence of Tb³⁺. A preliminary evaluation of the lubrication properties of the CMK-3 and one nanocomposite material was performed. The friction factors determined by means of ring upsetting tests revealed that the carbon materials were able to lower frictional forces although they were 3–4 times less efficient than a commercial graphite-based reference lubricant.     

Effect of ceramic filler content on the mechanical and thermal behaviour of poly-<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid and poly-<Emphasis Type="SmallCaps">l</Emphasis>-lactic-co-glycolic acid composites for medical applications

One main application of resorbable poly-l-lactic acid (PLLA) and poly-l-lactic-co-glycolic acid (PLGA) based materials is in medical implants. In this study composites were made from PLLA and PLGA with hydroxyapatite (HAp) respective β-tricalcium phosphate (β-TCP) fillers. The filler content and particle size were varied, and the thermal properties as well as the mechanical strength of the composites were investigated. The composites were made by an extrusion compounding process giving 2–2.5 mm diameter sized profiles. The results verified that the thermal stability of the composites was reasonable during the optimized compounding conditions. Scanning electron microscopy revealed that the fillers were well dispersed in the polymer matrices. The mechanical properties were improved by the addition of the fillers. The optimum mechanical properties for the extruded profiles were obtained with the HAp fillers. The E-modulus was increased from 3.3 to 4.6 GPa by addition of filler particles (30 wt%) whereas the flexural strength was reduced from 133 to 106 MPa.     

Analysis of growth parameters for hydrothermal synthesis of ZnO nanoparticles through a statistical experimental design method

Nanocrystalline ZnO particles were synthesized from an aqueous solution composed of zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O) and urea (H₂NCONH₂). A precipitating precursor, basic zinc carbonate (Zn₅(CO₃)₂(OH)₆), was first formed by hydrothermally treating the solution at 120 °C for 2–4 h. Nanocrystalline ZnO particles were then obtained by calcining the precursors at 350–650 °C for 0.5–2 h. The synthesis products were characterized using thermogravimetry–differential scanning calorimetry–mass spectrometry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and photoluminescence techniques. Based on the experimental results, a possible reaction mechanism for the ZnO formation was proposed. The effects of experimental parameters (namely, the hydrothermal treatment time, the calcination time, and the calcination temperature) on the characteristics of the resulting ZnO products (i.e., the crystalline size and the photoluminescence properties) were analyzed by the Taguchi method to attain the optimum synthesis conditions. By using the appropriate parameters derived from this method, we verified that the optimized synthesis provided a yield of ~70% and that the resulting ZnO particles possessed the characteristics of a ~25 nm crystalline size and a satisfactory photoluminescence property.     

Photocatalytic activities of LaFe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>3</Subscript> nanocrystals prepared by sol–gel auto-combustion method

Nanophotocatalysts LaFe_1−x Zn _x O₃ (x = 0, 0.05, 0.1, 0.3, 0.5) were successfully prepared by sol–gel auto-combustion method. The samples were characterized by X-ray diffraction (XRD), ultraviolet/visible absorption spectra (UV–vis), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The photocatalytic activities of the prepared samples were investigated for the photodegradation of methylene blue (MB). The results show that the lattice constant of LaFe_1−x Zn _x O₃ nanocrystals increases due to the substitution of Zn for Fe, which leads to the lattice distortion. The absorption edges of Zn-doped LaFeO₃ display a red shift with a significant absorption between 400 and 500 nm. Doping with the Zn ions enhances the photodegradation rate of LaFeO₃ for MB. The LaFe_0.7Zn_0.3O₃ particles are spherical with mean grain size of about 20–30 nm, which exhibits the highest degradation rate of 75% under irradiation time of 150 min.     

A cellular level biocompatibility and biosafety evaluation of mesoporous SiO<Subscript>2</Subscript>-based nanocomposite with lanthanum species

The risk assessment of SiO₂ nanoparticles has attracted extensive attention due to their great potential for various commercial purposes. However, the toxicity of mesoporous SiO₂-based nanocomposite is still unclear. Herein SiO₂-based hexagonal mesoporous nanosphere doping La³⁺ ions with diameter of 40–50 nm (SLa-HMS) and micronsized SiO₂-based hexagonal mesoporous solid inlaid with nanowires, 80–250 nm in length and 4–5 nm in diameter, of La species (WLa-HMS) were synthesized via self-assembly method. The specimens were characterized by small angle XRD, TEM, EDS, FT-IR, and N₂ ad–desorption. HeLa, fibroblast, and HBMSC cells were exposed to 0.1–100 μg/mL of SLa-HMS and WLa-HMS colloids for 12, 24, 48, and 72 h. Our data demonstrated that exposure of SLa-HMS in the dose range tested had no hazardous effect on all three cell lines, which was greatly different from previous reports. However, the WLa-HMS with average particle size of 10–19 μm was proven to be very toxic to the growth of all three cell lines. These interesting findings strongly suggest that doping heteroatom could be a way to improve the cytotoxicity of nanomaterials, as well as to oncotherapy on the basis of the hazardous effect of nanomaterials.     

Synthesis and characterization of bimodal rod-like mesoporous carbons from raffinose by SBA-15 templates

Mesoporous carbons with bimodal rod-like pore structures and tunable pore sizes from 3.66 to 5.42 nm were for the first time obtained by employing SBA-15 as templates and raffinose as carbon precursors. Small angle X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N₂ sorption analysis, and Raman spectroscopy were used to determine the textural properties of the resulting materials. Bimodal frameworks with mesopores (4–5 nm) as well as macropores (125–130 nm) were achieved. The mesoporous carbons lost its ordered structure from the templates due to mesostructural shrinkage and collapse of mesopores, which resulted in partial duplicate of the template and pore-widening effect (meso to macropores). With the increasing of carbonization temperature from 500, 700 to 900 °C, the textural parameters such as specific surface areas, pore volumes, and mean pore diameters all increased significantly. In the temperature range studied, higher carbonization temperature would generate much more abundant porosity. The ratio of I _D to I _G (I _D/I _G) indicated a rather low crystallinity with the varying of aging temperature and the carbonization temperatures. The advantage of the procedure was that no acid or other chemical catalysts were involved during the infiltration and carbon formation process.     

Low temperature synthesis of hydroxyapatite nano-rods by a modified sol–gel technique

Hydroxyapatite (HAp) nano-rods were successfully synthesized by a modified sol–gel method using a solution of CaCl₂·2H₂O in water, along with a solution of H₃PO₄ in triethylamine and NH₄OH as starting materials. The Ca/P molar ratio was maintained at 1.67. The sol obtained was dried in an oven for 2 days at 100 °C after being dialyzed for 12 h. Pellets were made from the crystalline powders and immersed in simulated body fluid (SBF) to check its biocompatibility after 15, 45 and 180 days of immersion. The HAp powders and pellets were characterized by X-Ray Diffraction crystallography (XRD), Fourier transform Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Transmission electron microscopy (TEM). The HAp nano-rods had an average diameter of 25 nm and length 110–120 nm. Immersion of the HAp pellets in SBF led to the formation of a highly porous interconnecting HAp layer on the surface. The porosity increased with increase in immersion time.     

A novel method for the fabrication of homogeneous hydroxyapatite/collagen nanocomposite and nanocomposite scaffold with hierarchical porosity

Homogeneous nanocomposites composed of hydroxyapatite (HAp) and collagen were synthesized using a novel in situ precipitation method through dual template-driven. The morphological and componential properties of nanocomposites were investigated. The HAp particulates, in sizes of about 50–100 nm, were distributed homogeneously in the organic collagen hydrogel. Highly magnified TEM observation showed that HAp inorganic particles were composed of fine sub-particles (2–5 nm) without regular crystallographic orientation. Based on these homogeneous nanocomposites, a novel HAp/collagen nanocomposite scaffold with hierarchical porosity was prepared by multilevel freeze-drying technique. Compared to other conventional scaffolds for tissue engineering, this novel in situ method endows synthesized composite scaffolds with unique morphology—ultrafine HAp particles dispersed homogenously in collagen at nano level and the foam scaffold with hierarchical pore structures. The mechanical performance increased obviously compared with neat collagen. These results provided an efficient approach toward new biomimetic tissue scaffold for the biomedical applications with enhanced intensity/bioactivity and controlled resorption rates. This novel method, we expect, will lead to a wide application in many other hydrogel systems and may be useful for fabrication of various homogeneous inorganic/organic nanocomposites.     

Infrared spectroscopic study of water in mesoporous silica under supercritical conditions

The structure of water under high temperature–pressure conditions in mesospace was investigated by measuring the infrared spectra of water in mesoporous silica. Absorption peaks attributed to OH-stretching vibration of water in mesoporous silica were detected at lower wavenumbers as compared with bulk water, and the absorption peak positions were dependent on pore diameter. For small pore diameters (3–20 nm), absorption peak positions of water were detected at lower wavenumbers (ca. 3,300 cm⁻¹) at 400 °C, while for larger pore diameters (30–50 nm) the peaks were detected at higher wavenumbers (ca. 3,500 cm⁻¹). We attribute these features to the effects of mesoporous silica surface structure on the structural and vibrational modes of water. Furthermore, absorption peak positions changed significantly at different pore sizes (20 and 30 nm), indicating that the structure of water in small pores approaches a more ice-like structure. Based on our experimental results, the structured water layer in mesoporous silica is estimated to be at least 10 nm thick, which is thicker than that previously documented in molecular dynamic simulation studies where the thickness of structured water was found to be two or three layers from the surface.     

Synthesis of nano-MoS<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> composite and its catalytic degradation effect on methyl orange

A nano-MoS₂/TiO₂ composite was synthesized in H₂ atmosphere by calcining a MoS₃/TiO₂ precursor, which was obtained via a quick deposition of MoS₃ on anatase nano-TiO₂ under a strong acidic condition. The obtained nano-MoS₂/TiO₂ composite was characterized by X-ray diffraction spectroscopy, Brunauer–Emmett–Teller (BET) surface area, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive spectrometry, ultraviolet–visible spectroscopy, and Fourier transform infrared spectroscopy. The results show that the composite had a high BET surface area because of its small size and irregularly layered structure. MoS₂ in the composite was composed of typical layered structures with thicknesses of 2–8 nm and lengths of 10–40 nm. The composite contained a wide and intensive absorption at 400–700 nm, which is in the visible light region, and presented a positive catalytic effect on removing methyl orange from the aqueous solution. The catalytic activity of the composite was influenced by the initial concentration of methyl orange, the amount of the catalyst, the pH value, and the degradation temperature. In addition, the composite catalyst could be regenerated and repeatedly used via filtration three times. The deactivating catalyst could be reactivated after catalytic reaction by heating at 450 °C for 30 min in H₂.     

Nanocrystalline nickel dispersed with nano-size WO3 particles synthesized by electrodeposition

A new class of bulk nanocrystalline nickel dispersed with nano-scale WO₃ particles has been synthesized by conventional electrodeposition to clarify the effect of the presence of nano-size dispersions on the strength and thermal stability of nanocrystalline structures. It was found that WO₃ particles of an initial size of 0.1 μm, when suspended in an electrolyte, fragmented into smaller nano-size particles, and were embedded into nanocrystalline nickel matrix of an average grain size of 45 nm during deposition. X-ray diffraction and transmission electron microscopy analyses revealed that phase transition of WO₃ particles occurred from an initial monoclinic to a tetragonal structure. The cause-and-effect relation between the fragmentation and the phase transition of WO₃ particles was discussed. Further hardening was confirmed in comparison with nanocrystalline pure nickel, but its increment was less than that predicted by the classical Orowan-type hardening of the particle–dislocation interaction. The discrepancy may be associated with a different dominant deformation mode which operates in a nanocrystalline regime.     

Synthesis and characterization of gold–polypyrrole film composite

Polypyrrole (PPy) coatings have potential applications in batteries, fuel cells, sensors, anti-corrosion coatings, and drug delivery systems. In this article, PPy film coating on the electrode of quartz crystal microbalance (QCM) was exposed to acidic aqueous HAuCl₄ solution. The reduction for gold ions took place and gold particles were produced at the film surface. The gold content at the PPy film was monitored by using QCM. The concentration of gold uptake increases as the original concentration of HAuCl₄ solution increases. The morphology of the film before and after the deposition of the gold particles was studied by the scanning electron microscopy coupled with energy dispersive X-ray spectrometry. The gold particles are of undefined shape and have diameters around 200–600 nm. However, the image of the composite powder shows that gold particles of sizes 100–120 nm are distributed over the surface of the polymer particles with some aggregation. Infrared spectroscopy and X-ray diffraction were used to characterize the composite.     

One-pot synthesis of ordered mesoporous carbon–silica nanocomposites templated by mixed amphiphilic block copolymers

Mixed amphiphilic block copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO–PPO–PEO) and polydimethylsiloxane-poly(ethylene oxide) (PDMS–PEO) have been successfully used as co-templates to prepare ordered mesoporous polymer–silica and carbon–silica nanocomposites by using phenolic resol polymer as a carbon precursor via the strategy of evaporation-induced self-assembly (EISA). The ordered mesoporous materials of 2-D hexagonal (p6m) mesostructures have been achieved, as confirmed by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and nitrogen-sorption measurements. Experiments show that using PDMS–PEO as co-template can enlarge the pore sizes and reduce the framework shrinkage of the materials without evident effect on the specific surface areas. Ordered mesoporous carbons can then be obtained with large pore sizes of 6.7 nm, pore volumes of 0.52 cm³/g, and high surface areas of 578 m²/g. The mixed micelles formed between the hydrophobic PDMS groups and the PPO chains of the F127 molecules should be responsible for the variation of the pore sizes of the resulting mesoporous materials. Through the study of characteristics of mesoporous carbon and mesoporous silica derived from mother carbon–silica nanocomposites, we think mesoporous carbon–silica nanocomposites with the silica-coating mesostructure can be formed after the pyrolysis of the PDMS–PEO diblock copolymer during surfactant removal process. Such method can be thought as the combination of surfactant removal and silica incorporation into one-step. This simple one-pot route provides a pathway for large-scale convenient synthesis of ordered mesostructured nanocomposite materials.