Mesoporous indium oxide synthesized via a nanocasting route

The synthesis of crystalline mesoporous indium oxide by using a mesoporous carbon (CMK-3) as hard template is described. Transmission electron microscopy (TEM) exhibits the presence of mesoporous structure in our sample and the corresponding wide-angle X-ray diffraction (XRD) pattern confirmed the crystalline wall of sample. N₂ adsorption measurement exhibits the synthesized crystalline mesoporous indium oxide possesses a specific surface area of 39 m²/g and the total pore volume of 0.17 cm³/g, and the corresponding pore size distribution curve reveals the presence of a mesopore of 7.0 nm in maximum. Our work demonstrates that the maintenance of the ordered structure of carbon template is very significant for obtaining high quality replicas via the nanocasting route.     

Synthesis of mesoporous silica materials (MCM-41) from iron ore tailings

Highly ordered mesoporous materials were successfully synthesized by using the iron ore tailings as the silica source and n-hexadecyltrimethyl ammonium bromide as the template. The samples were detail characterized by powder X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscopy and N₂ physisorption. The as-synthesized materials had high surface area of 527 m² g⁻¹ and the mean pore diameter of 2.65 nm with a well-ordered two-dimensional hexagonal structure. It is feasible to prepare mesoporous MCM-41 materials using the iron ore tailings as precursor.     

PE6400 templated monolithic mesoporous silica with orientated block structure

Novel monolithic mesoporous silica was synthesized with a new SDA (Structure-Directing Agent) of PE6400 (EO₁₃PO₃₀EO₁₃). The monolithic silica was found possessing special “oriented block” structure at nano-scale where pore channels' orientations were the same in a single block but not always the same in different blocks. Pore channels of a single oriented block were well ordered hexagonally oriented. Moreover, the average pore diameter, the average wall thickness, the specific surface area and the pore volume of the obtained monolithic silica were 3.5 nm, 3.3 nm, 777.5 m²/g and 0.44 m³/g, respectively.     

Preparation and characterization of high surface area nanosheet titania with mesoporous structure

High surface area nanosheet TiO₂ with mesoporous structure were synthesized by hydrothermal method at 130 °C for 12 h. The samples were characterized by XRD, SEM, TEM, SAED, and BET surface area. The nanosheet structure was slightly curved and approximately 50–100 nm in width and several nanometers in thickness. The as-synthesized nanosheet TiO₂ had an average pore diameter about 3–4 nm. The BET surface area and pore volume of the sample are about 642 m²/g and 0.774 cm³/g, respectively.     

The size modulation of hollow mesoporous carbon spheres synthesized by a simplified hard template route

Hollow mesoporous carbon spheres (HMCSs) have been prepared by a simplified replication route from a solid silica core/mesoporous silica shell aluminosilicate (SCMS-Al) template, which was synthesized by directly incorporating aluminum species into the mesoporous framework during template synthesis. The size of HMCSs can be tuned between 80 and 470 nm by simply changing the diameters of SCMS-Al. The HMCSs have uniform mesopores with a narrow pore size distribution (3.4-4.1 nm), and high surface area, (890-1150 m²/g) and total pore volumes (0.75-1.15 cm³/g). The techniques of N₂ sorption isotherms, TEM, EDX and SEM were used to characterize the as-synthesized spheres.     

Synthesis of mesoporous SiO2 glass by a novel chemical method

A novel five-step method for fabricating mesoporous SiO₂ glass was described in this paper, which consists of: (1) formation of colloidal suspension of Zn(OH)₂, (2) synthesis of silica sol, (3) mixture of Zn(OH)₂ colloidal suspension and silica sol to form nano-ZnO embedded precursor glass, (4) annealing of the precursor glass, and (5) treating nano-ZnO embedded glass with HCl to obtain the mesoporous glass. The mesostructure of the glass was investigated by X-ray diffraction (XRD), field emission scanning electron microscope (SEM), and BET surface area analysis. The average pore size distribution is in the range of 3.7 nm, and the surface area is as high as 496.5 m²/g.     

Surfactant/co-polymer template hydrothermal synthesis of thermally stable, mesoporous TiO2 from TiOSO4

Industrial TiOSO₄ solution was used as inorganic precursor to prepare mesoporous titania via composite template route, using cetyl-trimethylammonium bromide (CTAB) and tri-block copolymer EO₂₀PO₇₀EO₂₀ (P-123) as structure-directing agents (SDA) under high acidic conditions. Mesoporous TiO₂ with high thermal stability was obtained via controlling the hydrolysis and condensation rate of industrial TiOSO₄ solution by adjusting the pH value and post hydrothermal treating. The as-prepared materials were characterized by XRD, nitrogen adsorption-desorption, SEM and HRTEM. The powder calcined at 723 K for 2 h showed higher thermal stability, with BET specific surface area of 218.7 m²/g and an average pore diameter of 3.63 nm.     

Gelatin-assisted porous expansion of mesoporous silica

In this study, we report the pore expansion effect of gelatin, a common amphoteric biological protein, on the hexagonal mesoporous silica materials. Tetraethyl orthosilicate (TEOS) was used as silica source and the nonionic surfactant P123 (EO₂₀PO₇₀EO₂₀) as template. The microstructure characters of products were investigated by low-angle X-ray diffraction (LAXRD), transmission electron microscope (TEM), and N₂ adsorption–desorption measurements. The results show that the products prepared with gelatin have the mild expansion ratios of 29–39% and 5–22% in pore diameter and pore volume, respectively. The specific surface area of products ranges from 445 to 590 m² g⁻¹. Moreover, it is revealed that the presence of gelatin did not change the intact 2D-hexagonal mesoporous structure of materials. The ultraviolet–visible absorption spectroscopy (UV–Vis) analysis indicates that there is an interaction between the oxygen atoms of P123 and gelatin molecules. The pore expansion may be because the gelatin can interact with the hydrophilic sides of P123 micelles via hydrogen bonds interaction, which is different from the reported pore expansion mechanisms for other systems.     

Large-scale synthesis and characterization of fan-shaped rutile TiO2 nanostructures

Large-scale fan-shaped rutile TiO₂ nanostructures have been synthesized by means of a simple hydrothermal method using only TiCl₄ as titanium source and chloroform/water as solvents. The physicochemical features of the fan-shaped TiO₂ nanostructures are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), nitrogen absorption-desorption, diffuse reflectance ultraviolet-visible spectroscopy (UV-vis) and Fourier transform infrared spectroscopy (FTIR). Structural characterization indicates that the fan-shaped TiO₂ nanostructures are composed of several TiO₂ nanorods with diameters of about 5 nm and lengths of 300-350 nm. The average pore size and BET surface area of the fan-shaped TiO₂ nanostructures are 6.2 nm and 59 m²/g, respectively. Optical adsorption investigation shows that the fan-shaped TiO₂ nanostructures possess optical band gap energy of 3.11 eV.     

Recovery of high surface area mesoporous silica from waste hexafluorosilicic acid (H2SiF6) of fertilizer industry

In this article we report recovery of mesoporous silica from the waste material (hexafluorosilicic acid) of phosphate fertilizer industry. The process involves the reaction of hexafluorosilicic acid (50 ml, 24 wt% H₂SiF₆) and 100 ml, 0.297 M Na₂CO₃ to generate the alkaline aqueous slurry. Silica was separated from the slurry by filtration and the sodium fluoride was extracted from the aqueous solution by evaporation method. The obtained mesoporous silica was characterized by N₂ absorption/desorption (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM), and EDS. The results confirm that the separation of silica and NaF was successful and the final products have high purity. The silica product was found to have an average pore diameter of 4.14 nm and a high surface area (up to 800 m²/g). The process reported in this study may significantly reduce the release of hazardous materials into the environment and it might confer economic benefits to the responsible industries.     

Synthesis and photocatalytic oxidation properties of titania hollow spheres

The hollow spheres of anatase TiO₂ with higher photocatalytic activity have been fabricated by spherical CaCO₃ nanoparticles as a template, and titanium sulfate (Ti(SO₄)₂) as a precursor, and the CaCO₃ templates were dissolved subsequently in dilute HNO₃ solution. The TiO₂ hollow spheres samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N₂ adsorption-desorption isotherms. The characterization results indicate that as prepared TiO₂ hollow spheres sample was transformed to anatase phase in calcined at 400 °C, and the anatase TiO₂ hollow spheres have a higher specific surface area and show much better photocatalytic activity than commercial P25 in the photodegradation of Rhodamine B under the UV irradiation.     

Synthesis of mordenite zeolite in absence of organic template

Mordenite is a zeolite that has been used as a selective adsorbent and as a catalyst. Mordenite zeolite with crystal diameter 65 nm and crystal length 7 μm was successively synthesized in the absence of organic template by hydrothermal method at 180 °C for 5 days after stirring at high speed and aging in the synthesis mixture with the molar composition of 12Na₂O:100SiO₂:2Al₂O₃:500H₂O. The produced samples were investigated using XRD, SEM, FT-IR, EDS, DTA/TG and BET surface area. The prepared sample, crystallized in needle shape crystals. Total (BET) surface area was 52.14 m²/g whereas, total pore volume was 0.2 cm³/g. Average pore diameter was 24.16 Å. Thermogravimetry analysis (DTA/TG) showed that, at room temperature to 800 °C, mordenite mass loss is 6%.     

Synthesis of mesoporous Zn–Al spinel oxide nanorods with membrane like morphology

A well-aligned ZnAl₂O₄ spinel oxide nanorods with hierarchical pore structure was synthesized by a simple route using polycarbonate membrane as the sacrificial template. Spinel formation and the template removal occurred in one-step by calcination at 550 °C. SEM analysis of the calcined sample showed a membrane morphology made up of aligned rods with micron sized pores in between them. TEM analysis revealed that individual rods are 130 ± 30 nm in diameter and are nanoporous in nature. These rods are made up of nanoparticles of the sizes ranging from 5 to 12 nm. HRTEM analysis further showed that these nanoparticles are crystalline with the lattice spacing in commensurate with the ZnAl₂O₄ spinel oxide. Adsorption–desorption study shows Type IV isotherm with the pore size around 3.4 nm and high specific surface area of about 140 m²/g.     

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.     

Transparent glass ceramic containing Er:CaF2 nano-crystals prepared by sol-gel method

Er³⁺ doped SiO₂-CaF₂ transparent glass ceramic was prepared by sol-gel method. The microstructural evolution of the samples was studied with X-ray diffraction (XRD), transmission electron microscopy (TEM), and infrared spectra (IR). After heat-treatment at 900 °C, the Si-OH bonds and other organic groups were basically eliminated. The CaF₂ crystallites in the sample heat-treated at 900 °C are 10-20 nm in size, distributed homogeneously among the amorphous silica matrix. The efficient upconversion emission for Er^3+.4F_9/2 → ⁴I_15/2 transition was recorded under 980 nm excitation, which could be ascribed to the incorporation of Er³⁺ ions into the CaF₂ nano-crystals with low phonon energy.     

Structure, growth and magnetic property of hard magnetic CoPtP nanowires synthesized by electrochemical deposition

This paper reports the electrochemical synthesis and characterization of one dimensional hard magnetic CoPtP nanowires. Three electrode potentiostatic electrochemical technique was used to deposit nanowires into a nanoporous track-etched polycarbonate membrane with a nominal pore diameter 50 nm and thickness around 6-9 μm. The room temperature electrolyte used for the deposition of nanowires consists of 60 g/lt CoSO₄7H₂O, 4.1 g/lt H₂PtCl₆, 4.5 g/lt NaHPO₂ and 25 g/lt B(OH)₃. The structural morphology was observed by scanning electron microscope and transmission electron microscope. The magnetic property of the nanowires was measured by vibrating sample magnetometer before removing the template. The coercive fields were measured to be 143 kA m^− 1 and 103 kA m^− 1 for parallel (H_║) and perpendicular to the nanowire axis, respectively. The higher coercivity value for H_║ indicating nanowires' easy magnetization direction lies along the nanowires' axis. The average composition of the CoPtP nanowires was determined by electron dispersive spectroscopy and the crystallinity was measured by X-ray diffractometer.     

Hydrothermal synthesis, characterization, photocatalytic activity and dye-sensitized solar cell performance of mesoporous anatase TiO2 nanopowders

Mesoporous anatase TiO₂ nanopowder was synthesized by hydrothermal method at 130 °C for 12 h. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), HRTEM, and Brunauer-Emmett-Teller (BET) surface area. The as-synthesized sample with narrow pore size distribution had average pore diameter about 3-4 nm. The specific BET surface area of the as-synthesized sample was about 193 m²/g. Mesoporous anatase TiO₂ nanopowders (prepared by this study) showed higher photocatalytic activity than the nanorods TiO₂, nanofibers TiO₂ mesoporous TiO₂, and commercial TiO₂ nanoparticles (P-25, JRC-01, and JRC-03). The solar energy conversion efficiency (η) of the cell using the mesoporous anatase TiO₂ was about 6.30% with the short-circuit current density (Jsc) of 13.28 mA/cm², the open-circuit voltage (Voc) of 0.702 V and the fill factor (ff) of 0.676; while η of the cell using P-25 reached 5.82% with Jsc of 12.74 mA/cm², Voc of 0.704 V and ff of 0.649.     

Effect of solution pH on the surface morphology of sol–gel derived silica gel

We have examined the effect of solution acidity on the textural characteristics of silica gels prepared by sol–gel synthesis using tetraethyl orthosilicate (TEOS) as a silica precursor and cetyltrimethylammonium bromide (CTAB) as a template. Using IR spectroscopy, we have studied micellar TEOS solutions and the synthesized silica gel samples. The results demonstrate that, in an alkaline medium in a water–ethanol solution, SiO₂ experiences short-range ordering on the surface of micelles formed by CTAB molecules, whereas in an acid medium the process is not influenced by the presence of CTAB. Nitrogen porosimetry and electron microscopy data indicate that the silica gel obtained at pH 2 is microporous, with an average pore size of 2 nm. In an alkaline medium at pH 10, we obtained mesoporous SiO₂ (18 nm) with a narrow pore size distribution and a specific surface area of 110 m²/g.     

Adsorption of methanol on mesoporous SBA-15

The adsorption of methanol on mesoporous SBA-15 has been studied by using Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The BET surface area analysis shows decreases of the surface area from 387 to 383 m²/g, pore volume from 0.88 to 0.81 cm³/g and pore diameter from 9.07 to 8.4 nm after methanol adsorption. The appearance of strong IR bands at 2862 and 2964 cm^− 1 due to methyl (-CH₃) symmetric and asymmetric stretching demonstrate the presence of methanol and evidence of successful methanol adsorption. XPS results show increase of carbon and oxygen content on the surface of SBA-15. Thermogravimetric analysis shows that the methanol adsorbed on SBA-15 is stable up to a temperature of 265 °C and that the methanol adlayers decompose between 265 and 588 °C.     

A novel nanotube of composite of calcium carbonate and calcium sulfate

Nanotube-shaped precursor which is composed of layered structured sodium dodecylsulfate (SDS) calcium carbonate were obtained by titration of an aqueous solution of Na₂CO₃ into an aqueous solution containing CaCl₂ and SDS at 333-335 K. A unit of the repetition of the precursor was about 4 nm. Nanotube-shaped composite which is composed of CaCO₃ and CaSO₄ of 100-200 nm in diameter and 0.5-2 µm in length was obtained from nanotube-shaped precursor composed of layers of CaCO₃ and SDS by calcinations at 673 K in air. The precursor sheet composed of CaCO₃ layers on which SDS molecules attached to both side seemed to curl up and form a pipe.