Silver effect on the structure of SiO2-CaO-P2O5 ternary system

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 ≤ 10 mol%. 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.     

Synthesis and characterization of ZnO/SiO2 core/shell nanocomposites and hollow SiO2 nanostructures

In this paper, we prepared the ZnO nanoparticles by a simple hydrothermal method and fabricated the ZnO/SiO₂ core/shell nanostructures through a sol-gel chemistry process successfully. The hollow SiO₂ nanostructures were obtained by selective removal of the ZnO cores. The structure, morphology and composition of the products were determined by the techniques of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The results indicated that the ZnO nanoparticles were sphere-like shape with the average size of 60 nm and belonged to hexagonal wurtzite crystal structure. With the coating of SiO₂, the vibration modes of Si-O-Si and Si-OH were found. Furthermore, the measurement results of optical properties showed that spectra of bare ZnO nanoparticles and ZnO/SiO₂ core/shell nanocomposites exhibited similar emission features, including a blue emission peak and an orange emission band.     

Synthesis and characterization of ZrO2 hollow spheres

ZrO₂ hollow microspheres with the average diameter of about 500 nm and the shell thickness of about 50 nm were synthesized by a facile technique using carbon spheres as templates. The corresponding ZrO₂ hollow microspheres were obtained by calcining the precursors of C-Zr(OH)₄ core-shell heterostructures, which were synthesized with the precipitation of ZrCl₄ solution with aqueous ammonia on the surface of colloid carbons. SEM, XRD, TGA and BET were used to characterize the composition, morphology, size and crystal structure of synthesized products. The effects of ultrasonic dispersion and separation process on the hollow spheres were studied, and the surfactant PEG-1000 was added to tune the shell structure of synthesized ZrO₂ hollow spheres.     

Novel MoO3 and WO3 hollow nanospheres assembled with polymeric micelles

Novel β-MoO₃ and WO₃ hollow nanospheres were synthesized using a soft template of polymeric micelle with core-shell-corona architecture. Poly(styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) micelles (PS-PMAPTAC-PEO) with cationic shell block effectively produce core/shell composite particles through electrostatic interaction with anionic precursors WO₄²⁻ and MoO₄²⁻. Transmission electron microscope (TEM) images of β-MoO₃ and WO₃ have confirmed the hollow structure with average outer diameter of 42 ± 2 and 46 ± 2 nm, respectively; the hollow cavity diameters were found to be 16  ± 1 nm and 14 ± 1 nm for β-MoO₃ and WO₃, respectively. The combination of nitrogen adsorption/desorption analyses and TEM observation confirmed the presence of disordered mesopores in the shell domain of β-MoO₃ and WO₃ hollow particles.     

Solvothermal synthesis of the special shape (deformable) hollow g-C3N4 nanospheres

Special shaped (deformable) hollow g-C₃N₄ nanospheres were synthesized by the solvothermal technique using silica spheres as template. The X-ray diffraction (XRD) peaks of the product were indexed to g-C₃N₄ materials. Field-Emission Scanning Electron Microscopy and Transmission Electron Microscopy confirmed that the external diameter of the hollow nanospheres is about 130-150 nm and thickness of the wall is about 20-30 nm. The FTIR spectrum showed absorption peak at 810 cm^-1 can be attributed to the s-triazine (C₃N₃) breathing mode. Raman spectrum exhibited two broad peaks approximately at 1360 cm^-1 (D band) and 1580 cm^-1 (G band). The deformed pie shape or mortars like hollow spheres were first reported. The flexility of the deformable hollow g-C₃N₄ nanospheres may be used in special field such as drug delivery carriers adjusting the delivery ratio by the external pressure, and a good material for studying the mechanical properties of the sp² hybrid g-C₃N₄. The photoluminescence spectrum of the product indicates that the deformable hollow g-C₃N₄ nanospheres may have potential applications in nano-optical device fields.     

Synthesis and characterization of NiAl2O4 nanoparticles obtained through gelatin

Nanoparticles of NiAl₂O₄ were synthesized by heating (500-1000 °C) the dried resin resultant of a mixture in aqueous solution of gelatin, NiCl₂·6H₂O and AlCl₃·6H₂O. The particle size and microstrain were calculated from the line broadening of X-ray powder diffraction peaks through the Rietveld method refinement: these are 3.9-16 nm and − 0.743-0.139%, respectively. The NiAl₂O₄ nanoparticles were characterized by X-ray powder diffraction (XRPD), thermo gravimetric analysis (TG), BET and TEM techniques.     

Preparation and application of magnetic cobalt/SiO2 core/shell nanospheres

Homogeneous SiO₂-coated cobalt nanospheres with tunable silica shell thickness from 21.7 nm to 4.5 nm were synthesized by using modified Stöber method. These nanocomposites were used as source materials to prepare SiO₂ semi-hollow and hollow nanospheres by partially and completely etching cobalt cores, respectively. A proposed formation mechanism of these Co/SiO₂ nanospheres with a core/shell structure was presented in this paper, which is also important for the rational design and synthesis of other monodisperse core/shell nanoarchitectures with uniform size and shape. Furthermore, these Co/SiO₂ nanospheres were also used as a substrate for the deposition of CdS nanocrystals to prepare magnetic luminescent Co/SiO₂/CdS nanocomposites.     

Synthesis and characterization of hollow glass microspheres coated by SnO2 nanoparticles

The composite of hollow glass microspheres coated by SnO₂ nanoparticles has been successfully fabricated via sol-gel method. The phase structures, morphologies, particle size, shell thickness, chemical compositions of the composite have been characterized by XRD, FESEM, and EDX. The results show that SnO₂ coating on hollow glass microspheres can be achieved, and the coating layers are constituted by SnO₂ nanoparticles of mean size ca. 15 nm. The SnO₂ coating layers grow thicker with the increased concentration of SnCl₄. The effects of parameters (reaction temperature, concentration of NaOH and SnCl₄, and time) were investigated to yield SnO₂ coating on hollow glass microspheres, and the UV-vis absorption spectra of the composites were studied.     

Preparation and characterization of sol-gel derived Er-Yb codoped SiO2/TiO2 core-shell nanoparticles

The Er³⁺-Yb³⁺ codoped silica/titania core-shell nanoparticles were prepared by hydrolysis of titanium alkoxide precursors in the presence of lanthanide ions via sol-gel method. The structure of the particles was characterized by field emission scanning electron microscopy and transmission electron microscopy. The diameter of the silica core is about 50 nm. The thickness of the titania shell is about 4 nm. A typical doping density of Er³⁺ in the titania shell is 4.51 at.%, and the one of Yb³⁺ is 12.20 at.%. The UV-vis-NIR absorption spectra and the photoluminescence spectra were also investigated.     

Structural and morphological characterization of Pr and Er-containing SiO2-P2O5 sol-gel thin films

Present work is focused on obtaining and characterization of sol-gel thin films belonging to SiO₂-P₂O₅-Er₂O₃ (I) and SiO₂-P₂O₅-Pr₂O₃ (II) systems. The films have been obtained by spin coating technique for three rotation speeds: 2000, 3500 and 5000 rpm. The deposition of the films was performed at different periods of time, i.e. 24 h, 96 h, 120 h, 144 h and 168 h after instant preparation of the precursor sols. FTIR (Fourier transform infrared spectroscopy) and Raman characterization aimed at investigating the structural changes that occurred in silicophosphate network in dependence on the spin rate of the substrate as well as on the time period elapsed since the sol preparation till the deposition day. FTIR spectra recorded in the 400-4000 cm⁻¹ range revealed Si-O-Si, P-O-P and Si-O-P vibration modes and optical phonons specific for OH units. Raman spectra collected in the 100-4000 cm⁻¹ range put in evidence stretching, bending and mixed vibration modes specific for silicophosphate network as well as rare-earth ion peaks specific to certain electronic transitions. Morphological investigation made by AFM (atomic force microscopy) on Er and Pr-doped silicophosphate sol-gel films evidenced specific features depending on the parameters mentioned above and SEM (scanning electron microscopy) analysis revealed micron sphere structural units, exfoliation of the films and micro cracks.     

Synthesis and luminescent properties of ZnNb2O6 nanocrystals for solar cell

The phase formation, morphology and luminescent properties of ZnNb₂O₆ nanocrystals by the sol-gel method were investigated at a lower temperature than that of the traditional solid-state reaction method. The products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), photoluminescence spectroscopy (PL) and absorption spectra. The activation energy of ZnNb₂O₆ grain growth is obtained about 18.4 kJ/mol. The diameters of the nanocrystals are in the range of 20-40 nm. The PL spectra excited at 276 nm have a broad and strong blue emission band maximum at 450 nm, corresponding to the self-activated luminescence of the niobate octahedra group [NbO₆]⁷⁻. The optical absorption spectrum of the sample at a calcination temperature of 800 °C has a band gap energy of 3.68 eV.     

Synthesis and characterization of Al2O3 hollow spheres

This paper presents a novel technique to create Al₂O₃ hollow spherical nanoparticles. It used Al(OH)₃ which was synthesized with Al₂(SO₄)₃ and NaOH, and the C-Al(OH)₃ core-shell nanoparticle as intermediate phases. The Al₂O₃ hollow spheres were achieved by the calcination of the carbon cores and the dehydration of Al(OH)₃. The chemical composition, morphology, size and superficial crystal structure of the nanoparticles were characterized with TEM, XRD, TGA, FTIR and BET. The result shows that the average diameter of the C-Al(OH)₃ core-shell nanoparticles is about 25 nm, the thickness of the Al₂O₃ shell is about 5 nm and the surface area is 215.2 m²/g. The procedure for the formation of Al₂O₃ hollow nanoparticles is discussed in details.     

Synthesis and characterization of Co3O4 hollow spheres

Co₃O₄ hollow spheres were hydrothermally prepared at 130 °C for 16 h in the presence of Poly-vinylpyrrolidone (PVP). The as-prepared products were characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), infrared spectrum (IR), X-ray photoelectron spectrum (XPS), and optical absorption spectrum. PVP surfactant plays important roles in the formation of Co₃O₄ hollow spheres. These Co₃O₄ hollow spheres have average diameters of ca. 350 nm, and the wall thickness around the shell is about 42 nm. The possible formation mechanism of hollow Co₃O₄ spherical structures has simply been proposed.     

Hierarchical electrospun SiO2 nanofibers containing SiO2 nanoparticles with controllable surface-roughness and/or porosity

Herein we report that hierarchical electrospun SiO₂ nanofibers incorporated with SiO₂ nanoparticles with fiber diameters being ∼ 500 nm and particle sizes being tens of nanometers were developed through the combination of sol-gel process and electrospinning technique followed by high-temperature pyrolysis; and their morphologies and BET surface areas were examined. The study revealed that the pre-gelation of tetraethyl orthosilicate (TEOS) in spin dopes was important to achieve the morphological consistence of the electrospun precursor nanofibers and the resulting final SiO₂ nanofibers; additionally, SiO₂ nanoparticles appeared to be enriched on the fiber surface, while the surface-roughness and/or porosity of the nanofibers could be controlled through adjusting the incorporation amount of SiO₂ nanoparticles. The developed hierarchical electrospun SiO₂ nanofibers are expected to have important applications in composites (particularly dental composites) as well as catalyst support and adsorption.     

Preparation of TiO2 hollow microparticles by spraying water droplets into an organic solution of titanium tetraisopropoxide

Hollow, spherical TiO₂ microparticles several tens of micrometers in diameter were prepared by spraying water into an organic phase containing titanium tetraisopropoxide (TTIP) as a titanium source. The rapid hydrolysis of TTIP at the water-oil interface resulted in the formation of a TiO₂ shell covering the water droplet. Hexane and cyclohexane were better solvents than isopropanol for fabricating hollow spherical microparticles, suggesting the importance of immiscibility of the solvent with water in this synthesis method. The average particle size increased as the distance from the nozzle to the surface of the TTIP solution was increased. The shell thickness was reduced by the addition of ethanol to the sprayed water droplet. These results demonstrate the controllability of the structure of TiO₂ hollow microparticles, including the diameter and the shell thickness.     

Synthesis and in vitro bioactivity of novel mesoporous hollow bioactive glass microspheres

The remarkable tissue-repairing bioactivity and biocompatibility of bioactive glass make it suitable for a wide range of applications. Here, novel mesoporous hollow bioactive glass microspheres (MHBGMs) with a uniform diameter range of 2-5 µm were prepared by a sol-gel method. Structural characterization indicated that the shell of hollow sphere had a mesopore size range between 2 and 10 nm and a thickness about 500 nm. The in vitro bioactivity test indicated that the novel structure exhibited high in vitro bioactivity. The uniform microspherical morphology and mesoporous hollow structure of MHBGMs, together with their high bioactivity, turn them into a good candidate as an injectable and drug-loading biomaterial for in vivo tissue regeneration and drug control release.     

Synthesis of pure anatase TiO2 nanocrystals in SiO2 host and the determination of crystal planes by ImageJ

Anatase TiO₂ nanocrystals in the TiO₂- SiO₂ matrix were prepared by the ultra hydroylsis sol-gel route. The samples were heat treated at 350 °C and 500 °C. The structural analyses of the samples were carried out using X-ray diffraction technique, Raman spectroscopy and Transmission electron microscopy. The size of the nanocrystals from the XRD spectra (8.3 nm) and TEM (5-8 nm) is well in agreement. The spacing for the crystal planes was also determined using the ImageJ program. The Raman peaks further confirmed the formation of only the anatase phase within the matrix.     

Structural and optical properties of the SiO2-P2O5 films obtained by sol-gel method

A comparative study of the sol-gel films prepared in the SiO₂-P₂O₅ system starting with triethylphosphate, triethylphosphite and phosphoric acid as P precursors was performed. The work addresses basic aspects of physics, chemistry, and engineering of oxide films for applications in microelectronics, sensing, nano-photonics, and optoelectronics by establishing the influence of different precursors on the composition, structure and optical properties of the obtained films. The influence of the type of substrate (glass and indium tin oxide coated glass) and of the thermal treatment (200 and 500 °C) on their structure and properties was studied. By spectroscopic ellipsometry, X-Ray photoemission spectroscopy and atomic force microscopy measurements the high vaporization of the phosphorous during the densification of the films by thermal treatment was noticed when P-alkoxides were used. The phosphoric acid that forms chemical bond with silica network during the sol-gel process leads to better incorporation of P in the silica network as compared to the P-alkoxides.     

Preparation and characterization of Sr-hardystonite (Sr2ZnSi2O7) for bone repair applications

In this work, the potential of Sr-hardystonite (Sr₂ZnSi₂O₇) ceramics for biomedical use was first detected. First, pure Sr₂ZnSi₂O₇ powders were successfully synthesized by sol-gel method, and then Sr₂ZnSi₂O₇ ceramics were prepared by sintering the powder compacts. The mechanical test showed that the bending strength and Young's modulus of Sr₂ZnSi₂O₇ ceramics could reach 82 MPa and 44 GPa, respectively, which were close to the values for human cortical bone. Degradation test in Tris-HCl buffer solution showed that Sr₂ZnSi₂O₇ ceramics had a low degradation rate with less than 3% weight loss after soaking for 28 days. Furthermore, the in vitro biocompatibility of the ceramics was evaluated by rabbit bone marrow stem cells (rBMSCs) adhesion and proliferation assay. The results showed that the ceramics supported the cells adhesion and proliferation. Taken together, Sr₂ZnSi₂O₇ might be a potential candidate for preparation of bone implants.