Small-angle X-ray Powder Diffraction Research Articles

Light-Triggered Reversible Supracolloidal Self-Assembly of Precision Gold Nanoclusters.

Monolayer thiol-protected noble metal nanoclusters are attractive nanoscale building blocks for well-defined colloidal superstructures. However, achieving facile reversible self-assembly of nanoclusters using external stimuli is still in its infancy. Herein, we report the synthesis and photon-assisted reversible self-assembly of thiolated azobenzene-stapled Au25 nanoclusters. Photoactivation of functionalized nanoclusters in dichloromethane by irradiating ultraviolet light at 345 nm results in a visual change and formation of disc-like colloidal superstructures (d ∼ 100-1000 nm). The superstructures readily disassemble into individual nanoclusters upon irradiating with visible light at 435 nm. Systematic changes in both the electronic absorption bands and nuclear magnetic resonance spectra of chromophores in solution suggest that the photoisomerization of surface ligands drives the self-assembly. High-resolution transmission electron microscopy, electron tomographic reconstruction, dynamic light scattering, and small-angle X-ray powder diffraction show that the disc-like superstructures contain densely packed nanoclusters. Long-range self-assembly and disassembly under ultraviolet and visible light, respectively, demonstrate reversible photoswitching in nanoclusters.

Synthesis of SBA-15 assembled with silicon nanoparticles with different morphologies for oxygen sensing

Abstract In this paper, our effort is focused on preparation and oxygen sensing of fluorescent silicon nanoparticles (Si NPs) assembled in three kinds of mesoporous SBA-15 with different morphologies, including spherical mesoporous SBA-15 (SPSBA-15), long rod-like mesoporous SBA-15 (LRSBA-15) and hexagonal prism-like mesoporous SBA-15 (HPSBA-15). The relationship of structure and sensing properties in mesoporous materials is studied. Small angle powder X-ray diffraction (SAXRD), Fourier transform infrared spectrometer (FT-IR), Brunauer-Emmett-Teller (BET), Discrete-Fourier-Transform (DFT) analyses and X-ray photoelectron spectroscopy (XPS) are used to characterize their structural properties. The obtained mesoporous SPSBA-15, LRSBA-15 and HPSBA-15 possess abundant Si–O–Si bands of the inorganic framework and high surface-volume ratios. Particularly, mesoporous HPSBA-15 materials exhibit the largest surface areas than other two mesoporous materials. Accordingly, the adding volume of Si NPs was 8 ml in mesoporous HPSBA-15. At the same time, the hybrid materials show the shortest response time of 2.2 s and recovery time of 11.2 s. This result can be attributed to the uniform and nearly parallel porous structure of the HPSBA-15 materials supporting with large surface areas and narrow pore size distributions. Therefore, the properties in oxygen sensing can be improved by using mesoporous SBA-15 materials with larger BET surface area.

Small-angle X-ray powder diffraction analyses, microstructure and morphology of some synthesized template silica samples related to the 2-methoxyethanol content

Small-angle X-ray powder diffraction analyses, microstructure and morphology of some synthesized template silica samples related to the 2-methoxyethanol content

Pd-KIT-6: synthesis of a novel three-dimensional mesoporous catalyst and studies on its enhanced catalytic applications

Synthesis of a novel three-dimensional mesoporous Pd-KIT-6 is carried out by a room temperature sol–gel method. The synthesised material is well crystalline observed from the Small angle powder X-ray diffraction. Calcination at 550 °C for 8 h retains the structure. The particle sizes are in the micron range. Si/Pd ratio of the as-synthesized material is found to be 45 against the input ratio 100. Transmission electron micrograph reveals the presence of the porous hexagonal structure. Thermogravimetric studies reveal that the KIT-6 (Korea Advanced Institute of Science and Technology number 6) undergo less weight-loss compared to Pd-KIT-6, which indicates the material is more crystalline than its metal-free counterpart due to the enhanced crystallisation rate. These results also supported by BET-surface area and Transmission electron microscopic picture. The 960 cm−1 band at Fourier transform Infrared spectroscopic analysis shows that the incorporation of Pd in the framework. These FT-IR results also supported by Raman Spectroscopic analysis. Electron spin resonance spectroscopic analysis shows that the Palladium is present in the +2 oxidation state in as-synthesized samples. Diffused reflectance Ultraviolet–Visible spectroscopic results show that Palladium is in tetrahedral coordination. Microwave irradiated Suzuki–Miyaura (SM) cross-coupling reactions studied by using the Pd-KIT-6 catalyst in detail without any organic solvent at 100 °C for 10 min. The reaction carried out in the presence of phenyl iodide, phenylboronic (PhB(OH)2), and K2CO3 produce biphenyl, with 98% yield. Change of halide to Phenyl bromide gave similar results, but Phenyl chloride gave lesser conversion (20%). It is due to the electronegativity difference between the halides. A plausible reaction mechanism is also proposed.

Combining Small-Angle X-ray Scattering and X-ray Powder Diffraction to Investigate Size, Shape and Crystallinity of Silver, Gold and Alloyed Silver-Gold Nanoparticles

The combination of simultaneous measurements of small and wide angle X-ray scattering (SAXS/WAXS–SWAXS) to investigate the overall size, shape, and crystallinity of silver nanoparticles and alloyed silver-gold nanoparticles in the size range of 8 to 80 nm is shown. The obtained results for overall size are in agreement with the particle size obtained by differential centrifugal sedimentation (DCS) and transmission electron microscopy (TEM). In addition to the overall size, SWAXS provided precise information about the crystallographic internal structure of the particles, providing a powerful multi-scale tool for structural characterization of the studied systems.

Synthesis of a high-surface area V2O5/TiO2-SiO2 catalyst and its application in the visible light photocatalytic degradation of methylene blue.

In the present study, we synthesized several high-surface area V2O5/TiO2–SiO2 catalysts (vanado titanium silicate, VTS). The synthesized materials were characterized by PXRD, FE-SEM/EDAX, TEM, FTIR, UV-Vis, XPS, fluorescence and photocatalytic activity studies. The small-angle powder X-ray diffraction pattern shows that the 110 and 200 planes are merged to become a single broad peak. Field-emission scanning electron microscopy shows that the titanosilicate is spherical in shape and V2O5 has a hexagonal rod-shaped morphology. The presence of various metal ions, such as V, Ti, Si and O, was observed by energy dispersive X-ray analysis and X-ray photoelectron spectroscopy. The transmission electron microscopy image shows clear hexagonal mesoporous fringes with V2O5 distribution. The BET surface area analysis shows that the VTS catalysts have higher surface areas than pure V2O5. Fourier transform infrared spectroscopic analysis shows the presence of Ti4+ ions connected to the silanol groups. The bandwidths of pure titanosilicate, V2O5 and their composites were calculated from their diffuse reflectance ultraviolet-visible spectra. The bandwidth was tuned by heterojunctions in the studied catalysts. The photoluminescence spectra of the VTS catalysts show a distinct behaviour as compared to those of the pure components. The photocatalytic activity of methylene blue degradation was determined with pure constituents and catalysts. VTS-1 (TS and VO weight ratio 2 : 1) shows higher conversion than other catalysts, pure titanosilicate and V2O5. This is probably due to the heterojunctions and higher surface area in VTS-1. Kinetic studies reveal that direct sunlight shows higher activity than pure visible light. A plausible physical and chemical mechanism for the photocatalytic activity is proposed.

Lanthanide complexes-functionalized ordered mesoporous TiO2: Multicolor emission (visible and near-infrared luminescence) based on visible-light sensitization

Recently, much attention has been paid to the lanthanide luminescent materials based on the visible-light sensitization for their potential applications in the fields of bio-imaging and optical devices. In this work, the lanthanide complexes have been covalently bonded to the ordered mesoporous titania (OMT) matrix, and the resulting titania-based hybrid ordered mesoporous materials (named as LnDB-OMT, Ln = Eu, Sm, Yb, Nd) were characterized by using Fourier-transform infrared (FT-IR) spectroscopy, small-angle X-ray powder diffraction (SAXD), N2 adsorption–desorption isotherms, transmission electron microscopy (TEM), fluorescence spectroscopy, and thermogravimetric analysis. Generally, exciting with visible light is advantageous over UV excitation. Of importance here is that, under excitation with visible light, the LnDB-OMT all show characteristic visible (Eu3+, Sm3+) as well as near-infrared (Sm3+, Yb3+, Nd3+) luminescence of the corresponding Ln3+ ions (multicolor emission covered from 500 to 1400 nm spectral region), which is attributed to the energy transfer from the ligands to the Ln3+ ions via an antenna effect.

Mesoporous silica nanoparticles in an efficient solvent-free transamidation of carboxamides with amines: an exhibition of a green recyclable nanocatalyst

A protocol is described for an efficient transamidation of amides with amines in the presence of mesoporous silica nanoparticles (MSNs). The latter is used as a green, heterogeneous, and recyclable nanocatalyst, under solvent-free conditions. Following this protocol, a wide range of aromatic, aliphatic, and cyclic/acyclic primary or secondary amines are used in synthesis of a series of amides with good to excellent yields (65–96%). MSNs is characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), small-angle powder X-ray diffraction (XRD), nitrogen adsorption-desorption analysis, and FT-IR spectroscopy. The metal/solvent-free condition, easy work up, high purity of the products, recyclability, and environmentally-friendly nature of the catalyst are the attractive features of this methodology.

Preparation of 1D Hierarchical Material Mesosilica/Pal Composite and Its Performance in the Adsorption of Methyl Orange

This paper highlights the synthesis of a one-dimensional (1D) hierarchical material mesosilica/palygorskite (Pal) composite and evaluates its adsorption performance for anionic dye methyl orange (MO) in comparison with Pal and Mobile crystalline material-41 (MCM-41). The Mesosilica/Pal composite is consisted of mesosilica coated Pal nanorods and prepared through a dual template approach using cetyltrimethyl ammonium bromide (CTAB) and Pal as soft and hard templates, respectively. The composition and structure of the resultant material was characterized by a scanning electron microscope (SEM), transmissionelectron microscopy (TEM), N2 adsorption-desorption analysis, small-angle X-Ray powder diffraction (XRD), and zeta potential measurement. Adsorption experiments were carried out with different absorbents at different contact times and pH levels. Compared with Pal and MCM-41, the mesosilica/Pal composite exhibited the best efficiency for MO adsorption. Its adsorption ratio is as high as 70.4%. Its adsorption equilibrium time is as short as 30 min. Results testify that the MO retention is promoted for the micro-mesoporous hierarchical structure and positive surface charge electrostatic interactions of the mesosilica/Pal composite. The regenerability of the mesosilica/Pal composite absorbent was also assessed. 1D morphology makes it facile to separate from aqueous solutions. It can be effortlessly recovered and reused for up to nine cycles.

Mesoporous CdS via Network of Self-Assembled Nanocrystals: Synthesis, Characterization and Enhanced Photoconducting Property.

Semiconduction nanoparticles are intensively studied due to their huge potential in optoelctronic applications. Here we report an efficient chemical route for hydrothermal synthesis of aggregated mesoporous cadmium sulfide (CdS) nanoparticles using supramolecular-assembly of ionic and water soluble sodium salicylate as the capping agent. The nanostructure, mesophase, optical property and photoconductivity of these mesoporous CdS materials have been characterized by using small and wide angle powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2-sorption, Raman analysis, Fourier transformed infrared (FT-IR), UV-Visible DSR spectroscopy, and photoconductivity measurement. Wide angle XRD pattern and high resolution TEM image analysis suggested that the particle size of the materials is within 10 nm and the nanoparticles are in well-crystallized cubic phase. Mesoporous CdS nanoparticles showed drastically enhanced photoelectrochemical response under visible light irradiation on entrapping a photosensitizer (dye) molecule in the interparticle spaces. Efficient synthesis strategy and the enhanced photo response in the mesoporous CdS material could facilitate the designing of other porous semiconductor oxide/sulfide and their applications in photon-to-electron conversion processes.

Study of the performance of amino-functionalized ordered mesoporous carbon in the transesterification of soybean oil

In this study, the synthesis of the amino-functionalized mesoporous carbon resulted from organic–inorganic self-assembly reaction of triblock copolymer P123, sucrose and silica was carried out. The mesoporous carbons with desirable textural properties such as BET surface area of 956 m2/g, average pore diameter of 4.7 nm and pore volume of 1.07 cm3/g were obtained. Their surface was modified and functionalized with amine groups. Also, small angle powder X-ray diffraction (XRD) confirmed the hexagonal order of porous structure and Fourier transform infrared (FT-IR) analysis of catalyst indicated presence of amine functional groups onto the surface. FESEM and TEM imaging for the purpose of morphological and structural order analysis have been carried out. The performance of the prepared catalysts was evaluated in the production of biodiesel through transesterification of soybean oil with methanol. Gas chromatography (GC) analysis of biodiesel samples demonstrated that at the temperature of 64 °C, methanol to oil molar ratio of 24:1 and 2 wt% of catalyst loading (based on oil used), about 91% of triglycerides were converted to methyl esters (biodiesel) after 6 h.

Effect of framework structure, pore size and surface modification on the adsorption performance of methylene blue and Cu2+ in mesoporous silica

A series of silica with diverse channel structures or pore diameters were synthesized via the hydrothermal method. Corresponding amine/nitro-modified materials were obtained by grafting, nitrating reaction, respectively. Textural and chemical properties were analyzed by Scanning electron micrograph (SEM), Small angle powder X-ray diffraction (SAXRD), Nitrogen adsorption-desorption measurement, Fourier transform infrared spectroscopy (FTIR), Thermogravimetric (TG) analysis and Zeta potential. Batch adsorption results revealed that distinct uptake capacities of Cu2+ and methylene blue occurred at the solid-liquid interface of prepared adsorbents. Especially, pure SBA-12-OH displayed the highest removal behavior toward methylene blue, mainly owing to its larger pore diameter. Amine-grafted SBA-12 (SBA-12-NH2) presented higher affinity to Cu2+ than others, originating from the complexation function of amine groups and its superior framework structure. Moreover, their adsorption isotherms and kinetics were further investigated to explore the application in industrial operation system.

NASICON type ordered mesoporous lithium-aluminum-titanium-phosphate as electrode materials for lithium-ion batteries

An ordered 2D-hexagonal mesoporous Lithium-Aluminum-Titanium-Phosphate (LATP-1) material has been synthesized by using cetyltrimethylammonium bromide (CTAB) as the structure directing agent (SDA) thorough hydrothermal route. After acid-ethanol extraction of the as-synthesized LATP-1 material, the extracted white solid product has been characterized thoroughly using small and wide angle powder X-ray diffraction (XRD), nitrogen adsorption/desorption analysis, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FE-SEM), Ultra-high resolution transmission electron microscopy (UHR-TEM) and thermogravimetric analysis (TGA). Elemental analysis revealed 2.53% Li, 2.02% Al, 4.84% Ti, 28.16% P, 62.44% O in the mesoporous LATP-1 material. The template-extracted LATP-1 material has been employed as anode and cathode materials for lithium ion batteries: as an anode material, the LATP-1 electrode exhibits stable discharge-charge performances with delivered capacity of 121 mAh.g−1 and 117 mAh.g−1, respectively and a high coulombic efficiency.

Facile route to synthesize mesoporous SBA-15 rods with different sizes for lysozyme immobilization

Lysozyme has been successfully immobilized in the mesoporous channels of SBA-15 rods with different sizes. In order to clarify how SBA-15 rods sizes affected the immobilization behavior of lysozyme, small-angle X-ray powder diffraction, Fourier-transformed infrared spectra and nitrogen adsorption/desorption were employed to characterize the SBA-15 rods before and after immobilization. The results clearly showed that lysozyme was immobilized into the channels of SBA-15 rods and the well ordered mesoporous structure of SBA-15 after adsorption of lysozyme was retained. The rate and amount of immobilization were strongly dependent on rods sizes. It was found that the rate and amount of lysozyme immobilization increased with decreasing the sizes of SBA-15 rods. The SBA-15 rods with small size exhibited rapid (<20 min to reach equilibrium) and high-capacity (up to 835 mg g−1) lysozyme immobilization. The effect of SBA-15 rods sizes on lysozyme immobilization rate and amount was discussed in detail. Furthermore, a mechanism for the effect of the rods sizes on the immobilization behavior was suggested.

Influence of functionalization type on controlled release of emodin from mesoporous silica

Emodin drug was introduced into the porous mesochannels of (γ-chloropropyl)triethoxysilicane (CPTES) and (3-aminopropyl)triethoxysilane (APTES) functionalized SBA-15 via a hydrothermal process. The pure, functionalized and drug loaded mesoporous materials were characterized by small angle X-ray powder diffraction, field scanning electron microscopy, high resolution transmission electron microscopy, nitrogen adsorption–desorption, Fourier transformed infrared spectra, and UV–visible spectrophotometry. The functionalization of mesoporous silica reduced the degree of crystallinity of the resulting material. High resolution transmission electron microscope images of the functionalized materials demonstrated the reservation of the hexagonal mesoporous structure of SBA-15. Pure, CPTES and APTES-functionalized mesoporous silica were employed as base materials for the controlled release of emodin drug. Drug loading results revealed that the loading capabilities largely depend on the specific surface area, and pore volume and pore diameter of the carrier matrix. Emodin drug release profiles were studied in phosphate buffered saline with pH 7.4, and outcomes specified that the drug release rate could be controlled by the surface CPTES and APTES-functionalized carrier matrices. Emodin loaded functionalized materials presented a lower release rate compared to that of the pure SBA-15. Emodin loaded APTES-functionalized SBA-15 presented the lowest release amount of 74.5 % even up to 60 h. These results propose that the functionalized mesoporous silica is a favorable drug carrier for accomplishing prolonged release time.

Optimization of the synthesis of SBA-3 mesoporous materials by experimental design

SBA-3 mesoporous materials are characterized by hexagonal regular arrangements of channels with diameters >2 nm, high specific surface areas and high specific pore volumes. In the work reported herein, experimental design-response surface methodology (RSM) is used to model and optimize the synthesis conditions for SBA-3 mesoporous materials. In this study, we evaluate the influences of surfactant/silica source molar ratios, aging times, temperature and pH on the synthesis of SBA-3 mesoporous materials by analyzing the XRD intensities pertaining to the [100] signal. Response surfaces were obtained using the Box–Behnken design, and the combination of reaction parameters was optimized. By applying statistical methodology, higher levels of the objective function (XRD intensities pertaining to the [100] signal) were obtained using cetyltrimethylammonium bromide (CTAB)/tetraethyl orthosilicate (TEOS) molar ratios of 0.07 and 0.16, HCl/TEOS molar ratios of 8 and 11, reaction temperatures of 35 and 45 °C and aging times of 12–24 h. The mesoporous SBA-3 samples obtained were characterized using small-angle X-ray powder diffraction (XRD), BET, FTIR and 29Si NMR-MAS, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

In-vitro drug release kinetics studies of mesoporous SBA-15-azathioprine composite

The mesoporous silica (or SBA-15) was loaded with azathioprine drug. Azathioprine drug was incorporated into mesoporous silica by post impregnation method to reduce its toxic effects by controlling the drug release property. The synthesized pure SBA-15 and SBA-15-azathioprine composite were characterized by UV–visible spectrophotometry, thermo-gravimetric analysis, small and large angle powder X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption–desorption analysis. The successful inclusion of azathioprine drug in host material SBA-15 was confirmed by the reduced surface area (114 m2/g) and pore diameter (6.5 nm) of the organic–inorganic composite material. The drug entrapment efficiency of 90.67 % and loading efficiency of 72.67 % was achieved. The azathioprine drug release process from the mesoporous silica to simulated gastric, intestinal and body fluid were examined and the controlled release effect of the azathioprine drug in all fluids were studied. The Korsmeyer–Peppas model fits well the drug release data with the non-Fickian diffusion model and zero order kinetics for produced mesoporous silica. The controlled drug release enhanced the bioavailability and reduces its repeated administration. Hence, the composite drug can reduce the toxicity and side effects of the azathioprine.

Functionalization of Mesoporous SBA-15 with APTES by Co-Condensation and its Effect on Immobilization of &lt;i&gt;Candida&lt;/i&gt; &lt;i&gt;rugosa&lt;/i&gt; Lipase

Functionalized SBA-15 with mesoscopic pore channels was synthesized by co-condensation of tetraethoxysilane and (3-aminopropyl) triethoxysilane (APTES) via hydrothermal process. Small-angle X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy were used to monitor the effect of surface functionalization on the structural and textural features of the SBA-15. The results suggested that the structural ordering of functionalized SBA-15, as well as pore diameters, pore volumes and surface areas, were decreased with increasing the APTES molar ratio. Candida rugosa lipase (CRL) was used as a model enzyme for studying the effect of amino-functionalized on loading amount and enzymatic activity. The effects of pH and temperature on catalytic hydrolysis of tributyrin by immobilized CRL were investigated. The results showed that immobilized CRL had a well adaptability in a wide pH and temperature region, and CRL immobilized on functionalized SBA-15 exhibited much higher enzymatic activity than free CRL, especially, 5 mol% APTES functionalized SBA-15 immobilized CRL displayed the highest activity.

Excellent adsorption of ultraviolet filters using silylated MCM-41 mesoporous materials as adsorbent

Silylated MCM-41 materials were examined to adsorb of ultraviolet (UV) filters from aqueous solution at 303K. Compared to UV filters adsorbed on unsilylated MCM-41, a much higher adsorption capacity was achieved by silylated MCM-41 materials. Surface modification offers a greater opportunity to adjust both the pore size and surface properties of organic functionalized MCM-41 type materials. In the present study, MCM-41, methyl functionalized MCM-41 (M-MCM-41) and chlorotrimethylsilane end-capped (TMS-M-MCM-41) mesoporous materials were successfully synthesized using sol–gel technology. The structures and properties before and after surface modification were systematically investigated through N2-adsorption desorption isotherms, scanning electron microscope (SEM) and transmission electron microscopy (TEM), small angle X-ray powder diffraction analysis (SXRD), and infrared spectroscopy (FT-IR). They together confirm that the methyl and trimethyl silyl (TMS) group is chemically bonded to the internal surface of the mesopores. The sorption of UV filters obeys Langmuir and Freundlich sorption isotherms, showing the suitability of silylated MCM-41 as adsorbent for enrichment of UV filters from water.

APTES grafted ordered mesoporous silica KIT-6 for CO2 adsorption

Pure KIT-6 was synthesized using pluronic P123 (PEO20PPO70PEO20, mw∼5800Da) surfactant in mild acidic condition. It was functionalized with (3-aminopropyl) triethoxysilane (APTES) by grafting in dry and aqueous solvent at 80°C. Cubic (Ia3d) structure and uniformity of the adsorbents were analyzed by small angle powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Physical properties of the adsorbents were characterized by nitrogen adsorption/desorption behavior, infrared spectroscopy (IR) and thermo gravimetric (TG) analysis. CO2 adsorption/desorption behavior of the adsorbents was studied in a gravimetric analyzer. Optimum amine loading was substantially increased from 1.74mmolNg−1 in dry grafting to 2.75mmolNg−1 in aqueous grafting. The adsorption capacity was also remarkably increased from 0.90mmolCO2g−1 (An_K_9.0A) to 1.56mmolCO2g−1 (Aq_K_0.20W_9.0A) at 30°C. The heat of adsorption of the process was in the range of 20–32kJmol−1. The adsorbent showed its stability with the adsorption capacity remaining constant over 10 adsorption/desorption cycles.