Carbon sphere influence on textural properties and bioactivity of mesoporous bioactive glass/hydroxyapatite nanocomposite

Mesoporous bioactive glass/hydroxyapatite nanocomposite (MBG-HA) synthesis was conducted through evaporation-induced self-assembly (EISA) method followed by in situ carbonization, with non-ionic block co-polymer as mesoporous template and glucose-derived carbon sphere as co-template. The mixture of different carbon sphere contents into a glass network in the CaO–SiO₂–P₂O₅ system tailored the structural, morphological, and textural properties of MBG–HAs. Based on the preliminary results, the carbon sphere content and textural and structural parameters of as synthesized MBG–HAs showed a negative trend. The MBG–HA 0.5 with additional low carbon sphere content, showed a high surface area and large pore volume. The inclusion of HA nanoparticles inside the channels strongly influenced the high carbon sphere content of the MBG–HA8 mesoporous structure. For in vitro bioactivity tests, MBG–HAs with higher textural parameters possessed a faster apatite phase formation kinetics following the sequence MBG–HA0.5>MBG–HA2>MBG–HA5>MBG–HA8.     

Influence of Chemical Composition on the Bioactivity of Spray Pyrolyzed Mesoporous Bioactive Glass

SiO₂‐CaO‐P₂O₅‐based mesoporous bioactive glass (MBG) is a potential material for bone implants due to its superior bioactivity. Sol‐gel is a common technique for preparing MBG. Early studies showed that for MBG, the composition and surface area have critical influences on the bioactivity of MBG. However, there is a counteractive effect if both factors are used to enhance the bioactivity of MBG: a higher Ca content (lower Si content) provides more nonbridging oxygen groups, which enhance the bioactivity, but a higher Ca content also allows a lower viscosity at high temperature. Low viscosity is not able to prevent the MBG liquid flowing into the mesopores and results in the reduction of the surface area, which deteriorates the bioactivity. Unlike sol‐gel, spray pyrolysis (SP) offers a rapid cooling rate, which can avoid the lower viscosity and resultant damage to the mesoporous structure, and the rapid cooling rate also preserves more metastable siloxane groups, which enhance the bioactivity. In this study, MBG particles with various Si:Ca ratios were synthesized using SP, and the morphology and bioactivity were investigated. Two typical morphologies, spherical mesoporous and wrinkled mesoporous, were observed. Also, a faster hydroxyl apatite formation time was observed in MBG with lower silica concentration (70 mol% SiO₂).     

Anchoring mesoporous Fe3O4 nanospheres onto N-doped carbon nanotubes toward high-performance composite electrodes for supercapacitors

Fe-based oxide electrodes for practical applications in supercapacitors (SCs) suffer from low conductivity and poor structural stability. To settle these issues, we report on the design and synthesis of Fe₃O₄/carbon nanocomposites via firmly anchoring mesoporous Fe₃O₄ nanospheres onto N-doped carbon nanotubes (N-CNTs) via C–O–Fe bonds. Mesoporous Fe₃O₄ nanospheres are featured by rich electroactive sites and short ion diffusion pathways. The N-CNTs, on the other hand, serve as the scaffolds, which not only provide conductive networks but also suppress the accumulation between mesoporous Fe₃O₄ nanospheres as well as alleviate volume changes during charge/discharge cycles. Accordingly, the constructed Fe₃O₄/N-CNTs nanocomposite electrode demonstrates improved specific capacity values of up to 314 C g⁻¹ at 1 A g⁻¹, with 92% retention of the initial capacity after 5000 cycles at 10 A g⁻¹. In addition, the assembled Fe₃O₄/N-CNTs//active carbon (AC) asymmetric supercapacitor (ASC) device possesses an energy density of 25.3 Wh kg⁻¹, suggesting that the prepared Fe₃O₄/N-CNTs nanocomposites are promising electrode materials for use in SCs.     

Mesoporous electroactive silver doped calcium borosilicates: Structural,antibacterial and myogenic potential relationship of improved bio-ceramics

In this work improved electroactive mesoporous Ag-doped bio-ceramics for medical usages are developed, examining their structural, electrical, in-vitro bioactivity, cell cultures and antibacterial properties against various classical pathogenic bacteria. Ag-containing mesoporous bio-ceramics (MBCs): xmol%Ag₂O - (100-x)[45.8CaO-8.4B₂O₃-45.8SiO₂] where x = 2, 5, 7.5 and 10 were synthesized through a sol-gel method. The small angle X-ray scattering and electron microscopy studies reveal the embedment of silver nanoparticles in the samples. Existence of silver as Ag⁺/Ag⁰ forms in the samples is confirmed by X-ray photoelectron spectroscopy. The N₂ adsorption-desorption analysis evidence the mesoporous structure of the samples. The electrical conductivity of samples increases from 5.4 x 10^?8 S cm^?1 for x = 2 to 1.9 x 10^?6 S cm^?1 for x = 7.5 and then decreases to 0.9 x 10^?6 S cm^?1 for x = 10 at 110 °C. In vitro bioactivity studies revealed that Ag-containing MBCs hold the bone-like hydroxyapatite formation after immersion in human blood plasma like-solution such as Dulbecco's Modi?ed Eagle's Medium. The antibacterial effect of samples against pathogenic bacteria (S. aureus, E. coli, P. monas aeruginosa, and B. cereus) increases with Ag concentration (x = 7.5) and then decreases with Ag content (x = 10). Antibacterial effect is greater for the sample with high electrical conductivity. The cell culture studies evidence not considerable cytotoxic effects for Ag-containing MBCs. Finally, the C2C12 myoblast cell culture studies reveal the significant cell growths and differentiation (myogenesis) for high electrical conducting Ag-containing MBCs.     

Facile synthesis of water-soluble luminescent mesoporous Tb(OH)3@SiO2 core-shell nanospheres

Luminescent mesoporous Tb(OH)₃@SiO₂ core-shell nanospheres were synthesized through W/O microemulsion process at ambient temperature. The negatively charged silica favors a coating of the positively charged Tb³⁺ composite. Thus, silicon layer was adsorbed on the surface of Tb(OH)₃ groups to form Tb-O-Si through electrostatic interaction. X-ray diffraction, field emission transmission electron microscopy (FE-TEM), energy-dispersive X-ray spectrometry, and Fourier transform infrared, UV/Visible, and photoluminescence spectroscopies were applied to examine the phase purity, crystallinity, surface morphology, and optical properties of the core-shell nanospheres. The FE-TEM results have revealed typically ordered mesoporous characteristics of the material with monodisperse spherical morphology in a narrow size distribution. The luminescent mesoporous core-shell nanospheres exposed remarkable splitting with broadening in the emission transition ⁵D₄ → ⁷F₅ (543 nm). In addition, the luminescent mesoporous core-shell nanospheres emit strong green fluorescence (from Tb³⁺) in the middle of the visible region under 325 nm (3.8) excitation. The luminescent mesoporous Tb(OH)₃@SiO₂ core-shell nanospheres can therefore be exploited as fluorescent probes in biomarkers or biolabeling, optical sensing, and drug delivery system. Further, these nanospheres could have potential use as scattering layers in dye-sensitized solar cells.     

Thermal stability of mesoporous boron nitride templated with a cationic surfactant

The preparation of mesoporous boron nitride by using tris(monomethylamino)borazine (MAB) as boron nitride source and cetyl-trimethylammonium bromide (CTAB) as structurating agent is reported. The X-ray diffraction, TEM and pore size analysis show that highly porous boron nitride (specific surface area of 800 m²/g and mesoporous volume of 0.5 cm³/g) is synthesized with mesopores of 6 nm in diameter. Moreover, the mesoporosity is conserved up to 1600 °C under an inert atmosphere.     

Spectral properties of spherical boron nitride prepared using carbon spheres as template

Spherical boron nitride nanoparticles have been successfully fabricated by temperature-controlled pyrolysis procedure in a N₂ atmosphere, using boron acid and urea as the precursors. The carbon spheres were prepared from glucose (C₆H₁₂O₆) by a hydrothermal method as a template to be used. Comprehensive scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier infrared spectrum (IR) characterizations all confirm that the obtained products are spherical boron nitride. The amount of C₆H₁₂O₆ and reaction time were found to affect the morphology and structure of the as-prepared products. The average diameter of the spherical boron nitride nanoparticles synthesized with the addition of C₆H₁₂O₆ is about 0.3–1 µm. The spherical boron nitride has a high surface area of 176.78 m²g⁻¹ and ~3.5 nm pore size. The as-synthesized nanospheres also exhibit strong photoluminescence (PL) bands at 436, 454, 486, and 616 nm under 312 nm excitation, indicating that they could have potential application in novel optical devices.     

Self-assembly of Mesoporous Ni–P Nanosphere Catalyst with Uniform Size and Enhanced Catalytic Activity in Nitrobenzene Hydrogenation

Mesoporous Ni?CP amorphous alloy nanospheres with controllable sizes and compositions were synthesized by chemical reduction of Ni(OH)₂ colloidal particles co-assembling with surfactant hexadecyl-trimethyl-ammonium bromide in liquid crystal mesophase using hypophosphite as reductant. The effects of the synthesis conditions on the particle size, composition and mesostructure of the mesoporous Ni?CP nanospheres were systematically studied. It was found that the size of the mesoporous Ni?CP nanospheres could be tuned from 35 to 90?nm by changing the reduction temperature, and the phosphorus content of the Ni?CP products could be adjusted in the range of 20.1 to 27.6?% by changing the molar ratio of H₂PO₂ ^?/Ni²⁺. The active surface area and the thermal stability of the mesoporous Ni?CP nanosphere catalyst are much higher than those for the conventional nonporous Ni?CP amorphous alloy. In the liquid phase hydrogenation of nitrobenzene, the typical mesoporous Ni?CP nanosphere catalyst exhibits much higher activity and better selectivity than the conventional nonporous Ni?CP. The correlation between the catalytic performance and the structural properties is discussed based on the results of detailed characterization.     

Fabrication and microstructure of boron-doped isotropic pyrolytic carbon

Boron-doped isotropic pyrolytic carbon (pyrocarbon) was prepared by CVD using CH₄ + BCl₃ + H₂ as gaseous precursors. Microstructure of the deposited pyrocarbon on a graphite substrate was investigated using X-ray diffraction, X-ray photoelectron spectroscopy, polarized light microscopy, and scanning and transmission electron microscopy. It was found that the boron-containing pyrocarbon prepared exhibits a multi-scale structure, different from the pure isotropic pyrocarbon deposited under nearly the same experimental conditions. The multi-scale structure consists of carbon agglomerates of fine wrinkled graphitic sheets which contain substitutional boron and some micrometer-sized boron carbide particles uniformly distributed in the carbon agglomerates. Influence and mechanism of boron co-deposition during CVD process are also discussed.     

Reducing the reaction between boron-containing sealing glass-ceramics and lanthanum-containing cathode: Effect of Bi2O3

The volatile boron from boron-containing sealing materials often reacts with lanthanum-containing cathode, leading to the formation of LaBO₃ and consequently significant degradation of cathode. The reaction between boron-containing sealing glass-ceramics and lanthanum-containing cathode thus presents a challenge for the development of solid oxide fuel cell (SOFC). Here we report for the first time that such a reaction can be significantly reduced by Bi₂O₃ dopant in sealing glass-ceramics. In particular, the formation of LaBO₃ can be prohibited in reaction couple between glass containing 9 mol.% Bi₂O₃ and lanthanum strontium cobalt ferrite (LSCF) cathode. The addition of Bi₂O₃ enhances the [BO₃] → [BO₄] transition in glass structure and therefore improves the thermal stability of boron species in glass matrix. In addition, Bi₂O₃ dopant also favors the formation of BiBO₃, which dramatically reduces boron volatility from sealing glass-ceramics. The reported results provide an effective approach for solving the sealing challenge.     

Structural behavior and in vitro bioactivity evaluation of hydroxyapatite-like bioactive glass based on the SiO2-CaO-P2O5 system

Silicate bioglass is of great importance in bone engineering because of its excellent bioactivity and osteogenic effects. In this study, hydroxyapatite-like bioactive glass based on the xSiO₂-CaO-P₂O₅ (x = 30, 45, 60 and 90 mol.%, Ca/P = 1.67) system was synthesized by the sol-gel method, and the corresponding structural evolution, apatite-forming ability and cytotoxicity were systematically investigated. The results suggest that both a higher heat treatment temperature and a lower SiO₂ content increase the crystallinity tendency of the bioglass, and the samples become obviously compact as the SiO₂ amount increases from 30 to 90 mol.%. Compared with the samples with higher SiO₂ content, the 30Si sample shows more remarkable internal connected mesoporous structures, with a higher specific surface area up to 129.12 m²/g, exhibiting excellent hydroxyapatite formation in simulated body fluid. Moreover, no obvious inhibitory effect was presented on human periodontal ligament cells (hPDLCs) for any of the silicate glass samples.     

Properties of graphite prepared from boron-doped pitch as an anode for a rechargeable Li ion battery

Boron-doped graphites were derived from a naphthalene-based pitch mixed with para-xylene glycol (PXG) or dimethyl para-xylene glycol (DMPXG) as a cross-linking agent and three types of boron-containing compounds as a graphitization catalyst, and their anode performances were investigated. The structural analysis of the obtained graphites revealed that PXG functioned mainly as a two-dimensional cross-linking agent during the heat treatment process and DMPXG functioned partially as a three-dimensional. The average interlayer spacing decreased and lattice constant, a₀, and graphitizability increased with increasing the amount of boron atoms added. The result indicated that the carbon atoms were replaced by boron atoms. The anode performance was improved by the enhancement of graphitizability. The structural parameters and anode performance of boron-doped graphites did not depend on the kind of boron-containing compounds but the amount of boron atoms added in pitch and the kind of cross-linking agent.     

Triton X-100 directed synthesis of mesoporous γ-Al2O3 from coal-series kaolin

Mesoporous γ-Al₂O₃ has been successfully synthesized by using calcined coal-series kaolin as raw material and Triton X-100 (TX-100) as template. The effect of TX-100/Al^3 + ratio on the structural and textural properties of mesoporous γ-Al₂O₃ was investigated. Physical properties of obtained samples were characterized by X-ray diffraction (XRD), N₂ adsorption–desorption, transmission electron microscopy (TEM), thermogravimetric analysis (TG), scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDAX) and Fourier transform infrared spectroscopy (FTIR). The results indicated that the amount of TX-100 influenced the structure and porous properties of mesoporous γ-Al₂O₃ significantly. When TX-100/Al^3 + ratio was in the range of 0.03–0.15, all samples had mesoporous structures with BET surface area of 193.0–261.0 m²/g and pore size of 5.04–6.71 nm. In addition, the reaction mechanism involved in the process was proposed and discussed.     

MnCo2O4 nanospheres for improved lithium storage performance

Mesoporous MnCo₂O₄ nanospheres with an average diameter of approximately 480?nm have been synthesized by a polyvinyl pyrrolidone (PVP)-assisted solvothermal method followed by thermal annealing. MnCo₂O₄ nanospheres consist of many nanoparticles having sizes in range of 20–50?nm, the specific area of the sample being 24.4?m² g^?1. When used as the anode material for lithium ion batteries, the mesoporous MnCo₂O₄ nanospheres show not only an excellent cycling stability, but also an outstanding rate capability. More specially, the discharge capacities of 749.1 and 629.6?mA?h?g^?1 can be retained at current densities of 200 and 400?mA?g^?1 after 50 cycles, respectively. In addition, the average discharge capacities of 1013.8, 827.1, 770.6, 733.3, 697.3, 651.4 and 522.4?mA?h?g^?1 could be observed at current densities of 100, 200, 400, 600, 800, 1000 and 2000?mA?g^?1, respectively. The improved cycling stability and rate capability can be ascribed to two unique structural features of mesoporous MnCo₂O₄ nanospheres: namely, the mesoporous nature of electrode materials which can help to reduce the volume variation during repeated lithiation/delithiation processes, and the nanostructure which can provide a shortened Li⁺ transmission path. The current synthesis approach can be easily spread to prepare other binary metal oxides, including Co-free anode materials.     

Insights from ab initio molecular dynamics simulations for a multicomponent oxide glass

It remains a challenge to establish structural models of multicomponent oxide glass systems. In this study, we have investigated 68.3SiO₂–16.1B₂O₃–4.2Al₂O₃–11.4Na₂O glass and melt structures by ab initio molecular dynamics (AIMD) simulations. The atomic configurations obtained from AIMD simulations were validated against ¹⁷O solid‐state NMR spectrum under 24.0 T and neutron diffraction data, and excellent agreement was achieved. The bond lengths, angles, and coordination geometries were statistically analyzed for each atomic species. Here we particularly address the role of minor atomic species such as five‐coordinate Si (Si^V) and Al (Al^V). The Si^V–O bond lengths and O–Si^V–O angle distribution in the glass indicated 1.718 Å and three peaks at 90°, 120°, and 175°, which are assigned to a coordination geometry of the trigonal bipyramidal structure. Ring statistic analysis revealed that Si^V and Al^V were found to preferentially contribute to the formation of small ring sizes.     

Hollow Sodium Tungsten Bronze (Na0.15WO3) Nanospheres: Preparation, Characterization, and Their Adsorption Properties

Abstract  

We report herein a facile method for the preparation of sodium tungsten bronzes hollow nanospheres using hydrogen gas bubbles as reactant for chemical reduction of tungstate to tungsten and as template for the formation of hollow nanospheres at the same time. The chemical composition and the crystalline state of the as-prepared hollow Na_0.15WO₃ nanospheres were characterized complementarily, and the hollow structure formation mechanism was proposed. The hollow Na_0.15WO₃ nanospheres showed large Brunauer–Emment–Teller specific area (33.8 m² g⁻¹), strong resistance to acids, and excellent ability to remove organic molecules such as dye and proteins from aqueous solutions. These illustrate that the hollow nanospheres of Na_0.15WO₃ should be a useful adsorbent.     

Synthesis of hollow mesoporous silica (HMS) nanoparticles as a candidate for sulfasalazine drug loading

Hollow mesoporous silica nanoparticles have emerged as attractive drug delivery carriers. In this work, we report successful synthesis of hollow mesoporous silica nanoparticles (HMSNs) using poly tert-butyl acrylate (PtBA) nanospheres as hard templates and CTAB as structure directing agent for loading sulfasalazine into its porous structure. The samples were synthesized using PtBA; sodium dodecyl sulfate (SDS) - in an aqueous solution of CTAB and tetraethylorthosilicate (TEOS) as the inorganic precursor. Two different methods were utilized to remove organic phases including calcination, and acidic/basic ethanolic solvent extraction approach. For the latter, microstructural studies using SEM and N₂ porosimetery revealed the formation of highly uniform mono-dispersed particles of sphere morphology (~ 130 nm) with the high specific surface area (1501 m²/g) and mean pore size of ~ 2.6 nm. However, rather deformed and aggregated sphere-like particles were obtained for the calcined samples. TEM examinations also confirmed the formation of 20–30 nm thick walls for the prepared HMSNs particles. Further, HMSN samples treated by solvent extraction method were functionalized by 3-aminopropyl triethoxysilane (APTS) compound for drug delivery. DTA/TG analysis showed that the total amount of loaded sulfasalazine drug was 5.1 wt%.     

Ordered mesoporous Ga2O3 and Ga2O3–Al2O3 prepared by nanocasting as effective catalysts for propane dehydrogenation in the presence of CO2

Thermally stable mesoporous gallium and gallium–aluminum (atomic ratio of Ga/Al = 4/1 and 1/4) oxides with controlled textural and structural properties were prepared by means of the nanocasting approach. All materials have uniform micron-sized particles, with a quite narrow pore-size distribution centered in the range of 6.2–6.5 nm and specific surface areas as high as 231–322 m²·g^− 1. Pure mesoporous gallium and gallium–aluminum (Ga/Al = 4:1) oxides exhibit a promising catalytic performance in the dehydrogenation of propane to propene in the presence of CO₂ (DHP-CO₂). Over the most active materials, during 4 h on stream at 823 K, propene was produced with the yield of 10–18% and high selectivity of 91–95%. Moreover, pure mesoporous gallium oxide exerted a higher resistance on deactivation during the DHP-CO₂ process in comparison with gallium oxide prepared without a hard template.     

Nb2O5 nanospheres/surface-modified graphene composites as superior anode materials in lithium ion batteries

Uniform Nb₂O₅ nanospheres/surface-modified graphene (SMG) composites for anode materials in lithium ion batteries were synthesized by hydrothermal method. The microstructure and morphology of composites were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscope techniques. The experimental results showed that Nb₂O₅ nanospheres were tightly and uniformly grown on the surface of SMG nanosheets. Nb₂O₅ nanospheres/SMG composites exhibited an impressive reversible capacity of 404.6 mA h g⁻¹ at the current density of 40 mA g⁻¹ after 100 cycles, and an excellent rate capacity of 345.5 mA h g⁻¹ at the current density of 400 mA g⁻¹.     

Mesoporous silica-based electrochemical sensor for simultaneous determination of honokiol and magnolol

A kind of mesoporous SiO₂ was synthesized using cationic surfactant as the structure-directing template. After that, the resulting mesoporous SiO₂ was used to modify the carbon paste electrode (CPE). The electrochemical behaviors of honokiol and magnolol were examined. In pH 6.5 phosphate buffer, two well-shaped oxidation peaks at 0.31 and 0.44 V were observed at the mesoporous SiO₂-modified CPE. Compared with the unmodified CPE, the mesoporous SiO₂-modified CPE remarkably enhances the oxidation peak currents of honokiol and magnolol. This suggests that mesoporous SiO₂ exhibits considerable surface enhancement effects to honokiol and magnolol. After optimizing the parameters such as pH value, amount of mesoporous SiO₂, and accumulation time, a sensitive and simple electrochemical method was proposed for the simultaneous determination of honokiol and magnolol. As to honokiol, the calibration curve is from 2.0 to 100.0 μg L⁻¹, and the limit of detection is 0.5 μg L⁻¹ (1.8 × 10⁻⁹ mol L⁻¹). For magnolol, the linear range is from 20.0 to 200.0 μg L⁻¹, and the limit of detection is 10.0 μg L⁻¹ (3.8 × 10⁻⁸ mol L⁻¹). Finally, the newly proposed method was successfully employed to determine honokiol and magnolol in Chinese traditional medicines.