Synthesis of amorphous supermicroporous zirconium phosphate materials by nonionic surfactant templating

Supermicroporous zirconium phosphate materials possessing wormhole-like pores in the size range 1.3-1.8 nm were synthesized by using nonionic poly(ethylene oxide) surfactant (e.g., C₁₆H₃₃(EO)₁₀, C₁₈H₃₅(EO)₁₀) as a structure directing agent. The textural and structural properties were characterized by powder X-ray diffraction, N₂ adsorption analysis, differential thermal analysis, scanning and transmission electron microscopy, ³¹P MAS NMR and infrared spectroscopy. The synthesized materials are amorphous, exhibiting high surface areas, narrow pore size distributions, excellent thermal stabilities (over 800 °C) and acidic properties. The supermicropore size of the synthesized zirconium phosphate may be tunable by the variation of alkyl chain length of the surfactant.     

Synthesis of heteropoly oxometalate/amphiphilic block copolymer composite thin films with self-ordered mesostructures

A simple, reproducible, and versatile procedure for synthesizing mesostructured 12-phosphotungstic acid thin films with large spaced mesostructures (< 17 nm) using amphiphilic block copolymers as structure-directing agents is reported. The morphology of the mesostructure can be controlled by adjusting the m/n ratio of poly (ethylene oxide)_1/2/poly (propylene oxide) (EO_1/2/PO) in the tri-block copolymer (EO)_m(PO)_n(EO)_m. This synthetic approach was adapted to prepare mesoscopically ordered heteropoly oxometalates (HPOMs) films, including 12-phosphomolybdic acid and 12-tungsto (IV) silicic acid. The electrochemical properties of the calcined HPOMs films as electrodes in Li-ion batteries were also investigated.     

Synthesis of spheroidal ordered mesoporous carbon materials from silica/P123/butanol composites

Spheroidal ordered mesoporous carbon materials with diameter of 2–10 μm were synthesized by direct carbonization of silica/triblock copolymer P123/butanol composites using P123 and butanol as the structure-directing agents and carbon precursors. The morphologies, structures and pore characteristics of the carbon materials were investigated by scanning and transmission electron microscopes, X-ray diffraction, and nitrogen sorption. It was found that the material possesses a cubic ordered mesoporous structure with Ia3d symmetry. The butanol addition directly affects the carbon morphology and pore structure. When the mass ratio of butanol to P123 is 0.5:1, the product exhibits a perfectly spheroidal morphology with a specific surface area of 1236 m² g⁻¹ and a total pore volume of 1.26 cm³ g⁻¹. The formation mechanism of the spheroidal ordered mesoporous carbon materials is discussed briefly.     

Synthesis and electrochemical behavior of nanosized LiNi1−xCaxO2 cathode materials for high voltage secondary lithium-ion cells

A new class of LiNi_1−xCa_xO₂ (x = 0.0, 0.1, 0.2, 0.3 and 0.5) layered oxide materials has been synthesized by a simple low temperature solid-state route with mixed nitrates/urea with glycerol as the starting materials. First we have taken TG/DTA for observing the phase transformations of LiNi_0.9Ca_0.1O₂. The structure of the synthesized oxides was analyzed using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) to identify the crystal structure and cation environment, respectively. The synthesized ceramic oxide battery materials were examined by using transmission electron microscope (TEM), scanning electron microscope (SEM) analysis to determine the particle size, nature and morphological structure. SEM with energy dispersive X-ray spectroscopic analysis (EDAX) analysis was carried out to explore the composition of the prepared materials. The electrochemical performance of LiNi_1−xCa_xO₂ electrodes was analyzed using cyclic voltammetry (CV) and galvanostatic charge-discharge cycling studies in the voltage range 3.0-4.5 V. Electrode made with cathode active material, acetylene black and poly(vinylidene difluoride) yield a discharge capacity of 178.1 mAh g⁻¹ (x = 0.2) with good specific capacity over several charge-discharge cycles. These results have been also supported by cyclic voltammograms.     

Elucidation of interactive effects of synthesis conditions on the characteristics of mesoporous silicas templated using polyoxide surfactant

A series of mesoporous silicas (MS-1-MS-9) were synthesized at different gel compositions using a triblock copolymer (TCP), poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), as the surfactant. The interactive effects of acidity, the contents of tetraethyl orthosilicate (TEOS) and the surfactant, and the gelling temperature on the characteristics of the final material were simultaneously characterized. Increasing acidity favored mesopore formation. A material with a surface area of 760 m²/g, mostly in the mesoporous range, was obtained at 1.0(TEOS):0.017(TCP):7.3HCl:115.7H₂O. Mesopore formation was predominantly determined by the TEOS:TCP ratio and was promoted with its increase from 1.56:1 to 2.09:1. A further increase to 2.61:1 was detrimental. Whereas increasing the TCP content to 3.5% w/w improved micellization, a further increase to 4.6% should be avoided. Mesoporous silicas showed low crystallinity but a high degree of hexagonal mesoscopic organization. The weak surface acidity was attributed to surface silanols, the number of which was proportional to mesoporosity.     

Preparation of floral mesoporous SAPO-34 with the aid of fluoride ion

A novel floral mesoporous SAPO-34 was synthesized via conventional hydrothermal method in the presence of NaF with F/Si = 0.02-0.2. X-ray diffraction (XRD) analysis shows that the crystallinity of SAPO-34 increases with the increasing F/Si ratio and reaches to the best at F/Si = 0.1. Further increasing of F/Si ratio leads to the decrease of the crystallinity and the ultimate phase transformation to SAPO-5. Scanning electron microscopy (SEM) analysis shows that the addition of NaF leads to the formation of floral SAPO-34 while the addition of other salts including NH₄F, NH₄Cl and NaCl leads to the formation of traditional cubic SAPO-34. N₂ sorption isotherm and NH₃ temperature programmed desorption (NH₃-TPD) analyses indicate that floral SAPO-34 has the largest pore volume but lowest strong acidity compared with other samples with traditional cubic morphology. When applied to methanol to olefin (MTO) reactions, floral SAPO-34 shows the comparable yields of propylene and butylenes to other samples but lowest overall olefin yield, which is attributed to the synergistic effect of the largest pore volume and lowest strong acidity.     

Synthesis of indium oxide cubic crystals by modified hydrothermal route for application in room temperature flexible ethanol sensors

Indium oxide cubic crystals were prepared by using hexamethylenetetramine and indium chloride without the addition of any structure directing agents. The chemical route followed in the present work was a modified hydrothermal synthesis. The average crystallite size of the prepared cubes was found to be 40 nm. A blue emission at 418 nm was observed at room temperature when the sample was excited with a 380 nm Xenon lamp. This emission due to oxygen vacancies made the material suitable for gas sensing applications. The synthesized material was made as a composite film with polyvinyl alcohol which was more flexible than the films prepared on glass substrates. This flexible film was used as a sensing element and tested with ethanol vapours at room temperature. The film showed fast response as well as recovery to ethanol vapours with a sensor response of about 1.4 for 100 ppm of the gas.     

Synthesis and conductivity of cerium oxide nanoparticles

Cerium oxide (CeO₂) nanoparticles have been synthesized through composite-hydroxide-mediated approach. The X-ray powder diffraction (XRD) measurement proved that the pure cubic CeO₂ could be obtained at a low temperature region (170-220 °C). The particle size, micrograph morphology and microstructure were investigated by transmission electron microscope (TEM) and environmental scanning electron microscope (ESEM). The conductivity of as-synthesized CeO₂ was measured by a standard four-probe method. The conductivity of CeO₂ increases slightly with the increase of temperature. And the conductivity increases rapidly to 0.02418 s cm^− 1 at 830 °C. The product is a potential material for intermediate temperature solid oxide fuel cells (ITSOFC).     

Synthesis and characterization of CdO nanocrystalline structure by mechanochemical method

Cadmium oxide nanostructure was synthesized by calcining the obtained precursor of a mechanochemical reaction. The milling was carried out with cadmium nitrate tetrahydrate and acetamide reactants without any additives at room temperature. Resulting precursor was calcined at 450 °C for 2 h in a furnace. As a result of heating, the organic section of precursor was removed and cadmium oxide nanostructure was produced. The obtained compound from the mechanical milling (MM) technique possesses a cubic crystalline structure at nanoscale. XRD studies indicate that the obtained CdO has a cubic phase. Also, SEM and TEM images showed that the resulting material is composed of nanoparticles with the average diameter of 41 nm. The average size and standard deviation were calculated using a Microstructure Measurement program and a Minitab statistical software.     

Synthesis of polymer/1T-TaS2 layered nanocomposites

Single-phase layered nanocomposites containing 1T-TaS₂ and poly(ethylene oxide) or poly(ethylenimine) have been first synthesized by using the exfoliation-adsorption method. They have been characterized by powder X-ray diffraction. As the products exhibited lattice expansions along the stacking direction, poly(ethylene oxide) and poly(ethylenimine) were intercalated into 1T-TaS₂ galleries. Despite high conductivity of the host material, the resistivities of the polymer/1T-TaS₂ nanocomposites were found to be high in the order of 5.9-13 Ω cm.     

One-pot synthesis of supported-nanoparticle materials in ionic liquid solvents

Highly porous supported-nanoparticle materials were synthesized by a rational method involving the encapsulation of poly(vinylpyrrolidone) (PVP)-stabilized Au nanoparticles into titania xerogels employing room temperature ionic liquids (1-butyl-3-methylimidazolium hexaflurophosphate, [BMIM]PF₆) as a medium followed by solvent extraction of the ionic liquid and calcination of the materials. The materials were thoroughly characterized by TEM, nitrogen adsorption-desorption isotherms, and XRD. After calcinations at 350 °C, the Au-titania system resulted in the formation of a highly mesoporous materials with BET surface areas of 200 m²/g and average pore sizes of 3-5 nm. These materials can find potential applications in catalysis and photocatalysis.     

Elaboration, by tape casting, and thermal characterization of a solid oxide fuel half-cell for low temperature applications

In the past years, a major interest has been devoted to decrease the working temperature of solid oxide fuel cell (SOFC) down to about 700 °C. In this respect, materials with a high ionic conduction at intermediate temperature have to be found and the processes to elaborate fuel cells, using these new materials, have to be developed.Apatite materials (La_10−xSr_x(SiO₄)₆O_2±δ) are attractive candidates for solid electrolyte working at intermediate temperature. The ceramic powder was produced by solid state reaction and was tape cast to obtain green sheets.Concerning the cathode, a perovskite oxide (La_1−xSr_xMn_1−yCo_yO_3−δ) has been chosen. The perovskite powder was also shaped by tape casting with the introduction of a pore forming agent (corn-starch) to obtain the required porosity in the sintered cathode.The co-firing of the electrolyte/cathode half-cell in air at 1400 °C-2 h gives a flat sample with a dense apatite (98.2%), a 42.7% porous cathode and neither delamination nor chemical reactivity between electrolyte and cathode materials.The dimensional behaviour of the electrolyte material is stable for an oxygen partial pressure ranging from 10⁻¹⁰ to 0.21 atmosphere, from room temperature to 700 °C. The thermal expansion coefficients of the electrolyte and cathode materials are rather close (Δα = 2.8 × 10⁻⁶ K⁻¹) under air.     

Direct synthesis of polyoxometalates-functionalized mesoporous hybrid silicas

Novel polyoxometalates (POMs)-functionalized mesoporous hybrid silicas (SiW11/MHS) were synthesized for the first time by the co-condensation of tetraethoxysilane (TEOS) with Keggin-type monovacant SiW11 in the presence of block copolymer EO20PO70EO20 (P123). The as-obtained SiW11/MHS samples were characterized by FT-IR, UV/DRS, XRD, ICP-AES, and N2 adsorption-desorption measurements. It is shown that not only a hexagonal packing of channels with homogeneous pore diameter is obtained, but also Keggin units remain perfectly in the hybrid materials, and Si species insert into the vacancies of lacunary SiW11 during the synthesis to form SiW11Si2 structure, which condenses with the framework of mesoporous silica thus grafting POM molecules onto the pore wall of mesoporous silica by covalent linkage. This linkage results in a firmer immobilization of POMs on the mesoporous material. The water-leaching percent of POMs in the hybrid material is much less than those in the impregnated samples. Therefore, the synthesis strategy for the hybrid material is significant for acquiring supported POM catalysts of high efficiency and practicability.     

Solvo- or hydrothermal fabrication and excellent carbon dioxide adsorption behaviors of magnesium oxides with multiple morphologies and porous structures

MgO nano/microparticles with multiple morphologies and porous structures have been fabricated via the surfactant (poly(N-vinyl-2-pyrrolidone, poly(ethylene glycol) (PEG), cetyltrimethylammonium bromide, oleylamine or triblock copolymer P123 or F127) assisted solvo- or hydrothermal route in a dodecylamine or oleic acid solvent. The as-fabricated MgO samples were characterized by means of numerous techniques. It is shown that the obtained MgO samples were single-phase and of cubic in crystal structure; the particle morphology and pore architecture mainly depended upon the surfactant, solvent, and solvo- or hydrothermal temperature adopted. The solvothermal process resulted in polycrystalline MgO, whereas the hydrothermal one gave rise to single-crystalline MgO. Surface areas (8–169 m² g⁻¹) of the MgO samples derived solvothermally were lower than those (181–204 m² g⁻¹) of the MgO counterparts derived hydrothermally, with the mesoporous MgO generated after the PEG-assisted hydrothermal treatment at 240 °C for 72 h possessing the highest surface area. CO₂ adsorption capacities of the MgO samples were in good agreement with their surface areas, and the mesoporous MgO derived hydrothermally with PEG at 240 °C for 72 h exhibited the largest CO₂ uptake (368 μmol g⁻¹) below 350 °C. We believe that such a high low-temperature adsorption capacity renders the mesoporous magnesia material useful in the utilization of acidic gas adsorption.     

Synthesis and luminescence properties for europium oxide nanotubes

A novel high temperature sensitive fluorescent nanocomposite has been successfully synthesized by an economic hydrothermal method using carbon nanotubes (CNTs), europium oxide, and sodium dodecyl benzene sulfonate (SDBS). To our great interest, the nanocomposites show high temperature sensitivity after calcinations at various temperatures, suggesting a synergetic effect of CNTs and europium oxide which leads to ultrahigh fluorescence intensity of europium oxide nanotubes. When the novel high temperature sensitive fluorescent nanocomposites were calcined beyond 620 °C for 4 h, the obtained nanocomposites have a strong emission peak at around 540 and 580 nm, due to the ⁵D₀ → ⁷F_j (j = 0, 1) forced electric dipole transition of Eu³⁺ ions. In turn, the emission spectra showed a slight blue shift. The intensity of this photoluminescence (PL) band is remarkably temperature-dependent and promotes strongly beyond 620 °C. This novel feature is attributed to the thermally activated carrier transfer process from nanocrystals and charged intrinsic defects states to Eu³⁺ energy levels. The novel high temperature sensitive fluorescent nanocomposite has potential applications in high temperature warning materials, sensors and field emission displays. It is also interesting to discover that CNTs have the effect of fluorescence quenching.     

Utilizing NaCl to increase the porosity of electrospun materials

Electrospinning has emerged as a popular method for creating scaffolding materials used in tissue engineering applications to repair or replace damaged tissues. To become a viable scaffold material, however, pore sizes in electrospun materials must be increased to improve cell infiltration. Deposition of NaCl crystals during electrospinning was utilized to help overcome this obstacle. The NaCl crystals are released above the rotating collection mandrel and become incorporated into the poly(l-lactide) electrospun material. The NaCl then leaches out of the electrospun material creating larger pores: average pore diameter of 48.7 µm for PLLA-NaCl electrospinning versus 5.5 µm for PLLA alone electrospinning. Electrospun PLLA scaffolds with NaCl pores have a lower elastic modulus (8.05 MPa) and yield stress (349 kPa) and a higher yield strain (0.04) compared to their traditional counterparts (40.36 MPa, 676 kPa, and 0.0188). Decreased elastic modulus and yield stress would be beneficial to tissue engineering of elastic tissues including skin. The presence of NaCl pores did not significantly affect the cellular proliferation of MC3T3 cells but did allow for cell infiltration into the electrospun material. Therefore, the creation of large pores through NaCl leaching can significantly improve the performance of electrospun materials for tissue engineering applications by improving cellular infiltration.     

Synthesis of titania-silica xerogels by co-solvent induced gelation at ambient temperature

A series of binary titania-silica mixed oxides was prepared by sol-gel synthesis at room temperature. The hydrolysis of titanium isopropoxide (Ti(ⁱOPr)₄) and tetraethylorthosilicate (TEOS) was facilitated by co-solvent induced gelation in acidic media. The resulting gels were dried, calcined, and then characterized by powder X-ray diffraction analysis, nitrogen sorption studies (at 77 K), diffuse reflectance spectroscopy, Raman microscopy, and transmission electron microscopy. The nitrogen sorption studies indicate that the porosities could be tuned when simple aromatic solvents such as toluene, p-xylene, or mesitylene were added as a co-solvent to the synthesis gel. The binary mixed metal oxide materials obtained in this study showed high activity towards the degradation of phenol, and possessed high surface areas, and large pore volumes with narrow pore size distribution without the need for additional hydrothermal synthesis or supercritical drying.     

Fabrication and characterization of ordered macroporous semiconductors CdS by colloidal crystal template

The synthesis and characterization of a highly ordered macroporous CdS with regular arrays of spherical pores comparable to optical wavelengths are discussed. The sample has been successfully fabricated using colloidal crystal of poly (styrene-acrylic) (PSA) spheres as templates. The pore size is tunable in the range of 100-400 nm based on the size of PSA spheres. Transmission electron microscope (TEM) and scanning electron microscope (SEM) show that the exactly three-dimensional structure of the template has been imprinted in the final materials. XRD pattern indicates that the walls of the macroporous material are composed of 4 nm CdS nanoparticles making the absorption spectrum shift blue. The sample was also characterized by Raman spectroscopy and photo luminescent spectra (PL).     

Quick high-temperature hydrothermal synthesis of mesoporous materials with 3D cubic structure for the adsorption of lysozyme

Three-dimensional cage-like mesoporous FDU-12 materials with large tuneable pore sizes ranging from 9.9 to 15.6 nm were prepared by varying the synthesis temperature from 100 to 200 °C for the aging time of just 2 h using a tri-block copolymer F-127(EO₁₀₆PO₇₀EO₁₀₆) as the surfactant and 1,3,5-trimethyl benzene as the swelling agent in an acidic condition. The mesoporous structure and textural features of FDU-12-HX (where H denotes the hydrothermal method and X denotes the synthesis temperature) samples were elucidated and probed using x-ray diffraction, N₂ adsorption, ²⁹Si magic angle spinning nuclear magnetic resonance, scanning electron microscopy and transmission electron microscopy. It has been demonstrated that the aging time can be significantly reduced from 72 to 2 h without affecting the structural order of the FDU-12 materials with a simple adjustment of the synthesis temperature from 100 to 200 °C. Among the materials prepared, the samples prepared at 200 °C had the highest pore volume and the largest pore diameter. Lysozyme adsorption experiments were conducted over FDU-12 samples prepared at different temperatures in order to understand their biomolecule adsorption capacity, where the FDU-12-HX samples displayed high adsorption performance of 29 μmol g⁻¹ in spite of shortening the actual synthesis time from 72 to 2 h. Further, the influence of surface area, pore volume and pore diameter on the adsorption capacity of FDU-12-HX samples has been investigated and results are discussed in correlation with the textural parameters of the FDU-12-HX and other mesoporous adsorbents including SBA-15, MCM-41, KIT-5, KIT-6 and CMK-3.     

Synthesis of nano-sized hydroxyapatite powders through solution combustion route under different reaction conditions

Calcium hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂ (HAp) was synthesized by combustion in the aqueous system containing calcium nitrate-diammonium hydrogen orthophosphate with urea and glycine as fuels. These ceramics are important materials for biomedical applications. Thermo-gravimetric and differential thermal analysis were employed to understand the nature of synthesis process during combustion. Effects of different process parameters namely, nature of fuel (urea and glycine), fuel to oxidizer ratio (0.6-4.0) and initial furnace temperature (300-700 °C) on the combustion behavior as well as physical properties of as-formed powders were investigated. A series of combustion reactions were carried out to optimize the reaction parameters for synthesis of nano-sized HAp powders. The combustion temperature (T_f) for the oxidant and fuels were calculated to be 896 °C and 1035 °C for the stoichiometric system of urea and glycine respectively. The stoichiometric glycine-calcium nitrate produced higher flame temperature (both calculated and measured) and powder with lower specific surface area (8.75 m²/g) compared to the stoichiometric urea-calcium nitrate system (10.50 m²/g). Fuel excess combustion in both glycine and urea produced powders with higher surface area. Nanocrystalline HAp powder could be synthesized in situ with a large span of fuel to oxidizer ratio (φ) in case of urea system (0.8 < φ < 4) and (0.6 < φ < 1.5) for the glycine system. Calcium hydroxyapatite particles having diameters ranging between 20 nm and 120 nm could be successfully synthesized through optimized process variable.