Macropore Diameter Research Articles

A validated stability indicating HPLC method for determination of sitagliptin

A comparative and stability-indicating reversed phase high performance liquid chromatographic study have been developed and validated for sitagliptin phosphate. The liquid chromatographic determination was achieved isocratically on Poroshell 120 EC-C18 (100 × 4.6 mm, i.d.; particle size, 2.7 µm), Pursuit 5PFP (150 × 4.6 mm, i.d.; particle size, 5 µm) and Chromolith performance RP-18e (100 × 4.6 mm, i.d.; macropore diameter, 2 µm) columns using a mobile phase consisting of methanol:water:triethylamine:acetic acid (60:40:0.1:0.1; v : v : v : v ), at a flow rate 0.5 mL/min and UV detection at 268 nm. The method was linear over the concentration range of 100-1000 µg/mL ( r = 0.9998) with a limit of detection and quantitation of 10 and 30 µg/mL, respectively. All the validation parameters and stability indicating study were studied on Poroshell 120 EC-C18 column, which achieved the best separation. The proposed method has been found to have the required accuracy, selectivity, sensitivity, and precision to assay sitagliptin phosphate in bulk form and in a pharmaceutical dosage form. Degradation products resulting from the stress studies did not interfere with the detection of sitagliptin phosphate that indicates that the assay are stability-indicating assay.

Preparation of 3DON Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub> and Behavior of Li<sup>+</sup> Ion Exchange

The three-dimensionally ordered nanopores 3DON lithium ionic sieve precursors Li4Ti5O12 were synthesized by homemade polymethyl methacrylate (PMMA) colloidal crystal templates filled with lithium acetate, tetrabutyl titanate, oxalic acid and critric acid mixed solution after melt crystallization. The corresponding LiTi-H as a new lithium ion-sieve was obtained after the dilute hydrochloric acid treatment. The morphology and structure of the material were analyzed with SEM and X-ray diffraction (XRD), and saturated exchange capacity, adsorptive selectivity and reusability characterized the ion exchange properties. It turns out that PMMA colloidal crystal templates and 3DON precursors Li4Ti5O12 arranged orderly and macro pore diameter was approximately 80nm. What’s more, Li4Ti5O12 were spinel phase and lithium ionic sieve LiTi-H had a high selectivity for Li+, saturated exchange capacity for Li, 56.81mg (Li+).g-1 and good acid stability.

An Interface-Directed Coassembly Approach To Synthesize Uniform Large-Pore Mesoporous Silica Spheres

A facile and controllable interface-directed coassembly (IDCA) approach is developed for the first time to synthesize uniform discrete mesoporous silica particles with a large pore size (ca. 8 nm) by using 3-dimensional macroporous carbon (3DOMC) as the nanoreactor for the confined coassembly of template molecules and silica source. By controlling the amount of the precursor solution and using Pluronic templates with different compositions, we can synthesize mesoporous silica particles with diverse morphologies (spheres, hollow spheres, and hemispheres) and different mesostructure (e.g., 2-D hexagonal and 3D face centered cubic symmetry), high surface area of about 790 m(2)/g, and large pore volume (0.98 cm(3)/g). The particle size can be tunable from submicrometer to micrometer regimes by changing the macropore diameter of 3DOMC. Importantly, this synthesis concept can be extended to fabricate multifunctional mesoporous composite spheres with a magnetic core and a mesoporous silica shell, large saturated magnetization (23.5 emu/g), and high surface area (280 m(2)/g). With the use of the magnetic mesoporous silica spheres as a magnetically recyclable absorbent, a fast and efficient removal of microcystin from water is achieved, and they can be recycled for 10 times without a significant decrease of removal efficiency for microcystin.

Mathematical model relating uniaxial compressive behavior of manufactured sand mortar to MIP-derived pore structure parameters.

The uniaxial compression response of manufactured sand mortars proportioned using different water-cement ratio and sand-cement ratio is examined. Pore structure parameters such as porosity, threshold diameter, mean diameter, and total amounts of macropores, as well as shape and size of micropores are quantified by using mercury intrusion porosimetry (MIP) technique. Test results indicate that strains at peak stress and compressive strength decreased with the increasing sand-cement ratio due to insufficient binders to wrap up entire sand. A compression stress-strain model of normal concrete extending to predict the stress-strain relationships of manufactured sand mortar is verified and agreed well with experimental data. Furthermore, the stress-strain model constant is found to be influenced by threshold diameter, mean diameter, shape, and size of micropores. A mathematical model relating stress-strain model constants to the relevant pore structure parameters of manufactured sand mortar is developed.

Current Automatic Control Technology for n-Type Macroporous Silicon Photo-Electrochemical Etching

The relationship between the etching current density and the macropore diameter was studied in the macroporous silicon (MPS) photo-electrochemical (PEC) etching. By measuring the depth of the channel with different etching time, the variation of critical current density with time was calculated. The importance to real-time adjust the etching current was discussed in the etching process. Based on the PSoC chip, an automatic control system for etching current was designed. The MPS growth was realized with the pore diameter constant using the automatic control system for etching current with a pre-set curve of etching current versus time.

Providnist' ta fotoprovidnist' dvovymirnykh struktur makroporystoho kremniyu

The effective conductivity and the photoconductivity in two-dimensional macroporous silicon structures have been measured, and their dependences on the macropore concentration and diameter have been calculated. The effective conductivity of macroporous silicon structures is found to decrease as the concentration and the volume fraction of pores grow. A size effect was revealed, a significant reduction in the thickness of the space charge region at small macropore diameters (the surface charge) is observed. The effective relative photoconductivity is found to be governed by the charge recombination and accumulation on the pore surface. Theoretical dependences of the relative photoconductivity in the examined structures are found to correspond to a surface recombination rate of 90 cm/s.

Investigation of Pore Diameter Modulation in Depth in p-type Silicon

The possibility of local modulation of the macropore diameter has been investigated for macropores at different pore depths on pre-patterned low-doped p-type silicon (p-Si) substrates. Using electrolytes based on HF/organic solvents, it is relatively easier to vary the diameter of deep pores compared to shallow pores. Adding polyethylene glycol to the electrolyte helps to achieve pore diameter modulation even at shallow depths. Using Fast Fourier Transformation impedance spectroscopy (FFT-IS), the pore growth was analyzed in situ. A simple model was used to fit all the measured data, and some electrochemical parameters could be quantified. Comparing these parameters with the pore morphologies, it was observed that diffusion limitation is essential for achieving pore diameter modulation in p-Si by changing the applied current density.

The Role of Polyethylene Glycol in Pore Diameter Modulation in Depth in p-Type Silicon

The possibility of local modulation of the macropore diameter has been investigated for macropores at different pore depths on pre-patterned low-doped p-type silicon (p-Si) substrates. Using electrolytes based on HF/organic solvents, it is relatively easier to vary the diameter of deep pores compared to shallow pores. Adding polyethylene glycol to the electrolyte helps to achieve pore diameter modulation even at shallow depths. Using fast Fourier transform impedance spectroscopy (FFT IS), the pore growth was analyzed in-situ. A simple model was used to fit all the measured data, and some electrochemical parameters could be quantified. Comparing these parameters with the pore morphologies, it was observed that diffusion limitation is essential for achieving pore diameter modulation in p-Si by changing the applied current density.

Macroporous sol–gel bioglasses scaffold with high compressive strength, porosity and specific surface area

Bioactive glasses are known to have the ability to regenerate bone, but their use has been restricted mainly to powder, granules, or small monoliths. In this work, a series of macroporous bioglasses were produced by adding dried steamed bread particles into the sol as pore former. The porosity and macroporous diameter can be controlled by altering the particle size and volume of pore former. The macroporous structure can provide the potential room for tissue ingrowth. Simultaneously the samples exhibit mesoporous texture and high specific surface which can enhance bioactivity and release of ionic products. The most important is that these samples show satisfactory mechanical strength. These materials can fulfill the demands of scaffolds for bone tissue engineering and have great potential in applications to repair and reconstruct damaged tissue.

Metathesis of 1-butene and 2-butene to propene over Re2O7 supported on macro-mesoporous γ-alumina prepared via a dual template method

Macro-mesoporous γ-alumina support (MMA) was prepared by a sol-gel route in aqueous medium using pseudo-boehmite as aluminum source and polystyrene microspheres and Pluronic P123 as hard and soft dual templates, respectively. MMA had a BET specific surface area of about 259 m2·g−1, total pore volume of about 1.61 cm3·g−1, macropore diameter of about 102 nm, and mesopore diameter of about 14 nm. Re2O7/MMA and conventional Re2O7/Al2O3 were prepared by a incipient-wetness impregnation method, and their catalytic performances in the metathesis of 1-butene and 2-butene were tested in a fixed-bed tubular reactor. The result showed that Re2O7/MMA possessed higher activity and far longer working life-span than conventional Re2O7/Al2O3.

Macroporous Silicon Fabricated by HF Electrochemical Etching for Antireflective Application in Solar Cells

Macroporous silicon was fabricated by electrochemical etching in hydrogen fluoride (HF) electrolyte on P-type silicon wafers. By optimizing the etching condition, the obtained macroporous silicon presented pore diameter of about 2 μm and pore density of ~107/cm2. Such macroporous silicon gave out an excellent antireflective performance with the reflectance lower than 4% in a wide spectral range of 400-1000 nm. An a-Si:H/c-Si heterojunction solar cell was fabricated on such macroporous silicon to show its application potential.

Pores Reconfiguration in Compacted Bernam Series Soil

Problem statement: The introduction of mechanization in oil palm (Elaeis guineensis) plantations resulted in soil compaction with increased bulk density and reduced porosity due to reconfiguration of soil pores. This could be a serious problem in the future as soil pores are important for aeration and water movement. Approach: This study was carried out to determine the effect of mechanization on the morphological characteristics of pores of Bernam series soil. The treated plots were compacted using a tractor with 4 tonnes trailer weight. Undisturbed soil samples were taken from the harvesting path and the frond pile path at 0-10 cm depth. Thin sections image analysis of impregnated undisturbed soil samples were examined using a Leica DFC 290 microscope and analyzed using the associated software. Results: After six years of soil compaction treatments, the results showed a significant decrease in the mean total porosity of the compacted harvesting path with significantly smaller mean diameter of mesopores and macropores. In contrast, the percentage of macropores was significantly higher in the frond pile path and the control plot. Conclusion: Soil thin sections micromorphological image analysis is a better approach for quantitative measurements of altered soil porosity and pores distribution. Compaction caused reduction not only in total porosity but also causes reconfiguration and redistribution of pore sizes within the soil system.

Investigating the structure of a monolithic capillary column by means of hydrodynamic and size-exclusion chromatography

The porosity of a monolithic capillary column having a structure optimized for gas chromatographic analysis was investigated by means of hydrodynamic and size-exclusion chromatography. It was found that the total porosity of the column exceeded 90%, and the column had a bimodal pore structure with a micropore diameter of about 1.5 nm and a macropore diameter of about 1.2 μm. The column separated with good selectivity high molecular mass polystyrene standards with molecular masses higher than 100 kDa and low molecular mass solutes of up to 500 Da. The structure of monolithic column has to be optimized for application in hydrodynamic chromatography with an aim to provide selectivity on separation of polymers with molecular mass from 1 to 100 kDa.

Fabrication of individual scaffolds based on a patient-specific alveolar bone defect model

Fabricating individualized tissue engineering scaffolds based on the three-dimensional shape of patient bone defects is required for the successful clinical application of bone tissue engineering. However, there are currently no reported studies of individualized bone tissue engineering scaffolds that truly reproduce a patient-specific bone defect. We fabricated individualized tissue engineering scaffolds based on alveolar bone defects. The individualized poly(lactide-co-glycolide) and tricalcium phosphate composite scaffolds were custom-made by acquiring the three-dimensional model through computed tomography, which was input into the computer-aided low-temperature deposition manufacturing system. The three-dimensional shape of the fabricated scaffold was identical to the patient-specific alveolar bone defects, with an average macropore diameter of 380 μm, micropore diameters ranging from 3 to 5 μm, and an average porosity of 87.4%. The mechanical properties of the scaffold were similar to adult cancellous bone. Scaffold biocompatibility was confirmed by attachment and proliferation of human bone marrow mesenchymal stem cells. Successful realization of individualized scaffold fabrication will enable clinical application of tissue-engineered bone at an early date.

One-Pot Preparation and Uranyl Adsorption Properties of Hierarchically Porous Zirconium Titanium Oxide Beads using Phase Separation Processes to Vary Macropore Morphology

A simple and engineering friendly one-step process has been used to prepare zirconium titanium mixed oxide beads with porosity on multiple length scales. In this facile synthesis, the bead diameter and the macroporosity can be conveniently controlled through minor alterations in the synthesis conditions. The precursor solution consisted of poly(acrylonitrile) dissolved in dimethyl sulfoxide to which was added block copolymer Pluronic F127 and metal alkoxides. The millimeter-sized spheres were fabricated with differing macropore dimensions and morphology through dropwise addition of the precursor solution into a gelation bath consisting of water (H(2)O beads) or liquid nitrogen (LN(2) beads). The inorganic beads obtained after calcination (550 °C in air) had surface areas of 140 and 128 m(2) g(-1), respectively, and had varied pore architectures. The H(2)O-derived beads had much larger macropores (5.7 μm) and smaller mesopores (6.3 nm) compared with the LN(2)-derived beads (0.8 μm and 24 nm, respectively). Pluronic F127 was an important addition to the precursor solution, as it resulted in increased surface area, pore volume, and compressive yield point. From nonambient XRD analysis, it was concluded that the zirconium and titanium were homogeneously mixed within the oxide. The beads were analyzed for surface accessibility and adsorption rate by monitoring the uptake of uranyl species from solution. The macropore diameter and morphology greatly impacted surface accessibility. Beads with larger macropores reached adsorption equilibrium much faster than the beads with a more tortuous macropore network.

Microstructure of the mechanically alloyed and electrochemically etched Ti–6Al–4V and Ti–15Zr–4Nb nanocrystalline alloys

Formation of the Ti–6Al–4V and the Ti–15Zr–4Nb porous nanocrystalline alloys was described. The alloys were prepared by mechanical alloying (MA) followed by pressing, sintering and subsequent anodic electrochemical etching in 1 M H 3PO 4 + 2% HF electrolyte at 10 V for 30 min. The microstructure was investigated by XRD, TEM and SEM. We found that the mechanically alloyed powders are composed from nanostructure grains, whose size increases during the high temperature sintering. The final ultrafine grains improve subsequent etching process. The electrolyte penetrates sinters through the grain boundaries, resulting in effective grains removing and pores formation. The porosity of the Ti–15Zr–4Nb alloy is larger than that of the Ti–6Al–4V alloy. The macropore diameter reaches up to 40 μm, while the average micropore size is in the range from 3.5 to 5.46 nm for the Ti–15Zr–4Nb and the Ti–6Al–4V electrochemically etched alloys, respectively. The prepared porous ultrafine alloys could be possible candidate for a hard tissue implant applications, where the pores in the surface improve bonding of the implant with bone.

Transition metal-doped titania inverse opals: Fabrication and characterization

Transition metal (Fe, Zn, and Cr)-doped titania inverse opals were prepared by infiltrating a mixed precursor composed of tetrabutyl titanate (TBOT) and metal nitrate in the voids of home-made monodispersed polystyrene sphere templates. All obtained products exhibited three-dimensionally ordered macroporous (3DOM) structure and homogeneous wall composition. Fe, Zn, and Cr with broad concentration domains ranging from 1% to 20% were dispersed into the titania inverse opal (TIO) framework while preserving their respective morphology feature. The macropore diameter and frame thickness of transition metal (TM)-doped TIOs are dependent on different metal species doped. The morphology, composition, and optical property of TM-doped TIOs were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometer, X-ray photoelectron spectroscopy, X-ray diffraction, and UV/vis absorption spectroscopy.

Ring‐Opening Metathesis Polymerization‐Based Synthesis of CaCO3 Nanoparticle‐Reinforced Polymeric Monoliths for Tissue Engineering

Porous monolithic materials have been prepared via ring-opening metathesis polymerization from norborn-2-ene and a 7-oxanorborn-2-ene-based cross-linker in the presence of porogenic solvents (i.e., 2-propanol and toluene) and norborn-2-enephosphonate surface-modified CaCO(3) nanoparticles, using the 3(rd) -generation Grubbs-initiator RuCl(2) (Py)(2) (IMesH(2) )(CHPh). The experimental setup and the conditions chosen allowed for the manufacturing of polymeric monoliths characterized by a homogeneous distribution of the inorganic nanoparticles throughout the polymeric monolith. Depending on the nanoparticle content, the macropore diameters could be varied in the 30-120 µm regime. Noteworthy, the addition of nanoparticles did not affect the phase separation-triggered formation of the monolithic matrix nor the meso- and microporosity as evidenced by N(2) -adsorption experiments.

Preparation of multilevel macroporous materials using natural plants as templates

A series of two-dimensionally (2D) ordered macroporous silica materials have been prepared by using eight natural plants as templates. The macroporous materials replicate the complicated morphologies of natural plants precisely, and retained the original pore shape of plants. Meanwhile, these macroporous materials showed roughly similar morphologies and pore structure by the same part of plants, while the distribution of macropore diameters is ca. 8–1,000 μm. It may provide a effective approach to prepare macroporous materials with different 2D pore and complicated morphologies. These 2D ordered macropore silica materials may have potentially application for tissue repairing and templates materials to produce other kinds of macropores or hierarchically porous materials.

Photoluminescence modification in upconversion rare-earth fluoride nanocrystal array constructed photonic crystals

In this work, we fabricated the upconversion inverse opals with hierarchical rare-earth fluoride arrays by inducing NaYF4:Yb3+/Er3+ nanocrystal self-assembly inside the voids of a self-organized PS template via the MIMIC method. We induced cubic phase α-NaYF4:Yb3+/Er3+ nanocrystals to assemble in polystyrene (PS) colloidal crystals. After removing the PS colloidal template, highly ordered 3D inverse opal photonic crystals (PCs) hierarchical arrays consisting of densely packed cubic or hexagonal NaYF4:Yb3+/Er3+ nanocrystals were obtained. The photonic band structure of the materials can be controlled in a way that modifies the upconversion (UC) photoluminescence by adjusting the macroporous diameter of the NaYF4 photonic crystals. It is found that the photonic stop band can modify the emission band in the spectral region where the overlap occurs, producing a depression in the emission band corresponding to the stop band position, while the photoluminescence lifetime of the Er3+ ions in the inverse opals is also increased.