Good Structural Order Research Articles

Catalytic evaluation of Ni–3%Sr-/MCM-41 in dry and steam reforming of methane

A nickel catalyst on mesoporoussilica created through a direct synthesis and modified with a strontium promoter. After conducting dry and steam reforming tests, the prepared samples characterized using the XRD, XRF, BET, TPR and HR-TEM, and then considered to study the catalyst stability and activity. And, the CH4 and CO2 conversion and ratio of H2/CO with using the Sr–Ni/MCM-41 catalyst in the DRM and SRM processes at 700 °C, were determined about (73.3% and 80.6%), (55.81% and 60.25%), and (0.88 and 3.1), respectively. Furthermore, SEM, TPR, and TPD analysis were used to characterize the utilized catalyst. The finding demonstrated a good structural order and the specific surface area (SSA) of 889.5 m2/g. The presence of a strontium enhanced nickel oxide's reducibility and strengthened its interaction with the base. Furthermore, strontium enhanced the catalytic activity.

Cage-Based Covalent Organic Framework for the Effective and Efficient Removal of Malachite Green from Wastewater.

A cage-covalent organic framework (COF)-TP {T = bis(tetraoxacalix[2]arene[2]triazine); P = piperazine}, a novel two-dimensional covalent organic skeleton substituted with a nucleophilic cyanuric chloride analogue, was synthesized by a simple polymerization process. Cage-COF-TP is advantageous owing to its good structural order, permanent porosity, and low preparation cost. This skeleton was employed as a cost-effective adsorbent for the intermittent adsorption of an organic dye from aqueous solutions. Adsorption experiments were carried out at different initial dye concentrations, contact times, and solution pH. The adsorption kinetics followed the pseudo-second order model, and the results of thermodynamic studies were consistent with the Langmuir isotherm model. The high degree of matching between the size and shape of malachite green (MG) and the shrunken channels present in Cage-COF-TP were responsible for the enhanced adsorption ability of this material. Furthermore, theoretical calculations indicated that the high adsorption of the studied adsorbent can be attributed to the presence of nitrogen-rich triazine units in the Cage-COF-TP, which are expected to strengthen its affinity to guest molecules. The obtained results showed that the developed adsorbent is an efficient adsorbent that is theoretically capable of stimulating the removal of ∼2000 mg/g MG from wastewater at ambient temperature. This study will therefore be expected to promote the development of new functional materials based on COFs.

Defining Swelling Kinetics in Block Copolymer Thin Films: The Critical Role of Temperature and Vapour Pressure Ramp.

We studied the kinetics of swelling in high-χ lamellar-forming poly(styrene)-block- poly(lactic acid) (PS-b-PLA) block copolymer (BCP) by varying the heating rate and monitoring the solvent vapour pressure and the substrate temperature in situ during solvo-thermal vapour annealing (STVA) in an oven, and analysing the resulting morphology. Our results demonstrate that there is not only a solvent vapour pressure threshold (120 kPa), but also that the rate of reaching this pressure threshold has a significant effect on the microphase separation and the resulting morphologies. To study the heating rate effect, identical films were annealed in a tetrahydrofuran (THF) vapour environment under three different ramp regimes, low ), medium and high , for 60, 90 and 120 min, respectively, while the solvent vapour pressure and the substrate temperature were measured in real time. The translational order improved significantly with increasing the heating rate. The solvent mass uptake calculated for the different ramp regimes during annealing is linearly proportional to time, indicating that the swelling kinetics followed Case II diffusion. Two stages of the swelling behaviour were observed: (i) diffusion at the initial stages of swelling and (ii) stress relaxation, controlled at later stages. Films with a faster rate of increase in vapour pressure ) reached the pressure threshold value at an early stage of the swelling and attained a good phase separation. According to our results, highly ordered patterns are only obtained when the volume fraction of the solvent exceeds the polymer volume fraction, i.e., , during the swelling process, and below this threshold value , the films did not obtain a good structural order, even at longer annealing times.

Superior transport behavior of gold nanoparticles/P3HT blends by tuning optical and structural properties

Organic materials and blends have received a great deal of interests for application in large area, flexible, and low-cost organic/hybrid electronics. In this work the optical, structural and the electrical behaviors of a new active layer system composed by functionalized gold nanoparticles (AuNPs) and conjugated polymers, were investigated. For this purpose, gold nanoparticles with diameter of about 5 nm were chosen, coated with the bifunctional π-conjugated ligand (9,9-didodecyl-2,7-bis(acetylthio)fluorene, FL) for their high stability and easy dispersibility in organic solvents. The blends based on AuNPs and regioregular poly-3-hexylthiophene (P3HT) were prepared by adding an increasing percentage by weight of nanoparticles, i.e. from 10% to 90 wt%, in the P3HT polymeric matrix. The presence of nanoparticles was confirmed by UV-Vis spectroscopy, electron microscopy and X-ray diffraction techniques. The optical characterization of the composites demonstrated the possibility to tune the optical behavior of the P3HT by adding increasing percentages of AuNPs into the polymer matrix. Their inclusion results in a loss of P3HT crystallinity and in a simultaneous increase of the π-π interaction between the polythiophene chain and fluorene ligand. To better investigate the films, Grazing Incident X-ray Diffraction (GIXD) measurements were carried out and the blend containing 30 wt% of AuNPs in P3HT reveals an optimal condition, combining good structural order and interconnectivity in the polymer matrix. The electrical characterization of the AuNPs/P3HT blends reveals an improvement of the electrical conductivity in all the prepared blends, that show higher conductivity values compared to the pristine AuNPs and P3HT materials. The best performance is achieved adding 30 wt% of AuNPs to P3HT resulting in an enhancement of conductivity by about 350% compared to that of the pure polymer. This result could be of great interest for the realization of new conductive film composites to use in opto-electronic devices.

Facile preparation of ordered mesoporous Nb,Ta-MCM-41 by hydrothermal direct synthesis using columbite ore as metal source

– The current study aims to prepare an Nb,Ta-containing ordered mesoporous catalyst MCM-41, using hydrated mixed oxide of niobium and tantalum, extracted from the columbite ore processing, as an alternative source of these metals. Direct hydrothermal synthesis was employed to incorporate the metals into the molecular sieve structure using the TEOS + sodium silicate mixture as silica source and varying Nb and Ta content in terms of Si/Me (Me = Nb and Ta) molar ratios of 60, 30 and 15 to evaluate the influence of the charge of these metals on both structural formation and properties of the material. The material was characterized by XRD, SEM, TEM, N2 adsorption, UV–Vis-DRS, and FTIR investigations to the incorporation of the metal into the MCM-41 framework. The techniques employed proved the successful replacement of Si atoms by metallic cations of Nb and Ta. The catalyst showed good structural order preservation and surface area (>600 m2 g-1) with mesoporous behavior with capillary condensation even at a higher metal load. This research signifies a successful procedure of a novel bimetallic mesoporous material with promising properties for several applications using an abundant ore as a metal source.

Oxidación de trans-2-hexen-1-ol empleando materiales mesoporosos

En este trabajo se estudió la reacción de oxidación del alcohol trans-2-hexen-1-ol utilizando catalizadores del tipo MCM-41. Para ello, se sintetizaron sólidos mesoporosos modificados con titanio que fueron caracterizados por área específica, DRX, UV-Vis RD, FTIR e ICP. Los sólidos mostraron buen ordenamiento estructural y elevada área específica. En el Ti-MCM-41 no se observaron óxidos metálicos, lo que sugiere una buena dispersión del Ti en la estructura. Los materiales sintetizados fueron evaluados catalíticamente en la reacción de oxidación de trans-2-hexen-1-ol en fase líquida, a 70 °C, utilizando H2O2 como oxidante y acetonitrilo como solvente. Los productos de reacción fueron identificados mediante CG-Masa y cuantificados empleando factores de respuesta. Los resultados mostraron que la incorporación de Ti en la matriz mesoporosa incrementó la conversión del sustrato de 1.69% mol a 4.29% mol. Luego, se evaluó el efecto producido al variar la relación molar sustrato/oxidante empleando Ti-MCM-41. Con una relación igual a 1, se logró una conversión máxima de 8.26% mol, con un rendimiento de 7.64% mol y una selectividad de 85.22% mol al 2-hexenal.

Na-Ce-modified-SBA-15 as an effective and reusable bimetallic mesoporous catalyst for the sustainable production of biodiesel

With the purpose to compete with the homogeneous catalytic biodiesel production, a highly efficient bimetallic solid catalyst with high exposed surface, high basicity, and reusable throughout several reaction cycles, was developed by doping SBA-15 with sodium and cerium in different concentrations. The catalyst with 5 wt% of Na and 20 wt% of Ce showed good structural ordering and had the highest basicity due to the presence of a large amount of medium and strong sites compared to the other materials. It was effectively used as a solid base catalyst for biodiesel production from sunflower oil and absolute methanol. The highest FAME content (98.9 wt%) was achieved under optimum conditions of 40:1 methanol/oil molar ratio, 10 wt% catalyst loading, 60 °C, stirring speed of 600−700 rpm and 180 min. Further, this material was reused for five consecutive runs, obtaining FAME contents greater than 90 % in each one of them.

Study on magnetite nanoparticles embedded in mesoporous silica obtained by a straightforward and biocompatible method

Magnetic nanoparticles have been synthesized on mesoporous silica by a simple method without the need for either an alkali or an organic solvent, nor for rigorous pH control, making it a safe procedure for the nanomedicine field. The systems have been exhaustively characterized through different instrumental techniques, including the analysis of physicochemical properties by N2 adsorption, TEM, HAADF/STEM, SAED, EDS, XRD, XPS, and UV/Vis DRS. Magnetic properties have been tested by means of magnetization curves at room temperature and 5 K, ZFC-FC curves, and Mössbauer spectroscopy. The nanocomposite obtained by heating in N2 atmosphere showed good specific surface area and structural order, as well as high magnetization and negligible magnetic hysteresis and remanence, arising from the presence of finely dispersed magnetite nanospecies. These features are very relevant for future application as carriers for drug delivery systems, among other uses.

Effect of Polymer Chemistry on Chain Conformations in Hairy Nanoparticle Assemblies.

Matrix-free, polymer-grafted nanoparticles, called hairy nanoparticle assemblies (aHNPs), have proven advantageous over traditional nanocomposites, as good dispersion and structural order can be achieved. Recent studies have shown that conformational changes in the polymer structure can lead to significant enhancements in the mechanical properties of aHNPs. To quantify how polymer chemistry affects the chain conformations in aHNPs, here we present a comparative analysis based on coarse-grained molecular dynamics simulations. Specifically, we compare the chain conformations in an anisotropic cellulose nanoparticle grafted to four common polymers with distinct chemical groups, fragility, and segmental structures, that is, poly(methyl methacrylate) (PMMA), polystyrene (PS), polycarbonate (PC), and polybutadiene (PB). We observe that semiflexible glassy polymers such as PMMA and PS have a higher critical chain length (Ncr), the transition point where the polymer conformation changes from concentrated to semidilute brush regime. Flexible rubbery polymers (PB) can overcome the Ncr barrier at relatively lower molecular weights. We have used theoretical scaling laws based on Daoud-Cotton theory to uncover a direct correlation between empirical constants and physical parameters, such as persistence length and monomer excluded volume. Furthermore, we carried out a systematic study to understand the role of backbone rigidity and side-group size of polymer, and it revealed that the backbone rigidity significantly affects Ncr but the side-group size doesn't seem to have an appreciable effect on Ncr. We find that normalization of the monomer radial distribution curves using Ncr and other key molecular parameters collapses the curves for 110 distinct model aHNP systems studied. Our work paves the way for systematic quantification of these molecular design parameters to accelerate the design of polymer-grafted nanoparticle assemblies in combination with universal scaling relationships.

Fabrication of 1,2-dichlorobenzene sensor based on mesoporous MCM-41 material

Recently, mesoporous silicas with uniform pore diameters and ordered pore systems showed promising performances in sensing applications. The present paper was performed to develop a novel 1,2-dichlorobenzene chemical sensor based on mesoporous MCM-41 material, which exhibited a good performance at room temperature. The prepared MCM-41 was characterized using XRD, FT-IR, FE-SEM, TEM, EDX and XPS techniques. The obtained results revealed the spherical nature of the prepared MCM-41 with a good structural order and high specific area. A thin layer of synthesized MCM-41 was deposited on glassy carbon electrode (GCE). By using the fabricated working electrode for the chemical sensor, it was practically applied to detect 1,2-dichlorobenzene (1,2-DCB) successively by an electrochemical approach in phosphate buffer phase. The proposed 1,2-DCB chemical sensor has been exhibited good sensitivity (0.7468 μAμM−1 cm−2), wide linear dynamic range (0.089 nM–8.9 mM), low detect limit (13.0 ± 0.65 pM), and short response time (14.0 s). This novel 1,2-DCB chemical sensor based on MCM-41might be reliable and promisingly approach for the detection of 1,2-DCB for the safety of environment and healthcare fields in a broad scales.

A geometrically controlled rigidity transition in a model for confluent 3D tissues

The origin of rigidity in disordered materials is an outstanding open problem in statistical physics. Previously, a class of 2D cellular models has been shown to undergo a rigidity transition controlled by a mechanical parameter that specifies cell shapes. Here, we generalize this model to 3D and find a rigidity transition that is similarly controlled by the preferred surface area S0: the model is solid-like below a dimensionless surface area of with being the average cell volume, and fluid-like above this value. We demonstrate that, unlike jamming in soft spheres, residual stresses are necessary to create rigidity. These stresses occur precisely when cells are unable to obtain their desired geometry, and we conjecture that there is a well-defined minimal surface area possible for disordered cellular structures. We show that the behavior of this minimal surface induces a linear scaling of the shear modulus with the control parameter at the transition point, which is different from the scaling observed in particulate matter. The existence of such a minimal surface may be relevant for biological tissues and foams, and helps explain why cell shapes are a good structural order parameter for rigidity transitions in biological tissues.

Selective oxidation of benzyl alcohol through eco-friendly processes using mesoporous V-MCM-41, Fe-MCM-41 and Co-MCM-41 materials

MCM-41 nanostructured materials modified with Vanadium, Iron and Cobalt were synthesized by a hydrothermal method. The catalysts were characterized by XRD, UV–Vis-DR, ICP-OES and N2 adsorption. All the catalysts showed good structural order and high specific areas; however the lowest value in these parameters, corresponding to the Co-M(60) sample, could be due to the higher presence of oxide species determined by UV–Vis-DR. These mesoporous metalosilicates were evaluated in the liquid phase oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using H2O2 as oxidant. Results showed that V-M(60) had better catalytic performance than Fe-M(60) and Co-M(60) exhibiting high TON (1100mol/molV), selectivity to BzH (95%) and 31.7% yield at 7h under optimized reaction conditions. The main reason for the enhanced catalytic performance was attributed to the well dispersion of vanadium species in the framework which could be considered as the active sites for the benzyl alcohol oxidation reaction. At the same time, the catalyst could be recovered and effectively reused during three cycles without a significant loss in its activity and selectivity.

Tunable synthesis of hierarchical mesoporous silica via porogen-carrying organosilicates

We describe the synthesis and characterization of hierarchically porous organic-inorganic hybrid silica with periodic 2-D hexagonal order and tunable location of secondary nanopores through co-condensation of tetraethylorthosilicate (TEOS) and a new type of amphiphilic organosilicate precursors. Our amphiphilic organosilicates offer unique tunability of secondary micropores by carefully controlled bond molecular structure and number of bonds between hydrophobic adamantylphenols pore-generating moieties and siloxane precursors. Small angle X-ray scattering (SAXS) and microscopy results show a good structural order of the organic-inorganic hybrid silica. In addition, 29Si CP-MAS NMR spectra confirm the successful incorporation of organosilicate precursors into a silica framework. The primary cylindrical mesopores (∼6.4 nm) were originated from the cooperative self-assembly of Pluronic P123 triblock copolymer templates while smaller meso-/micropores were derived from adamantylphenols groups. We have previously demonstrated that adam-graft SQ had an affinity for hydrophobic PO core blocks to be located close to PO segment, which resulted in small pores next to primary mesopores and the resultant increment of mesopore size as well as wrinkled silica walls. On the contrary, the secondary small pores were mainly generated within a silica network while the size of the primary mesopores unaffected with the addition of adam-bridge SQ due to its selective incorporation into a silica framework. Moreover, the organic-inorganic hybrid silica prepared with adam-bridge SQ showed higher thermal stability than that of adam-graft SQ and SBA-15 type mesoporous silica. It is attributed to more SiOSi bonds formed from the bridged structure as well as enhanced hydrogen-bonding interaction between adam-bridge SQ hybrid silica and P123 templates.

High Conductivity in Molecularly p-Doped Diketopyrrolopyrrole-Based Polymer: The Impact of a High Dopant Strength and Good Structural Order.

[3]-Radialene-based dopant CN6-CP studied herein, with its reduction potential of +0.8 versus Fc/Fc+ and the lowest unoccupied molecular orbital level of -5.87 eV, is the strongest molecular p-dopant reported in the open literature, so far. The efficient p-doping of the donor-acceptor dithienyl-diketopyrrolopyrrole-based copolymer having the highest unoccupied molecular orbital level of -5.49 eV is achieved. The doped films exhibit electrical conductivities up to 70 S cm(-1) .

Weak itinerant ferromagnetism and clean superconductivity in Y9Co7

We present low-temperature magnetic properties for a high-quality polycrystalline sample of the first ferromagnetic superconductor Y9Co7. The results of susceptibility and magnetization measurements show the coexistence of a weak itinerant ferromagnetic order with a Curie temperature of TC ≅ 4.5 K and superconductivity below TS = 3 K. Several electronic quantities and parameters characterizing the superconducting and normal state are calculated within the Ginzburg–Landau–Abrikosov–Gorkov theory. The data reveal clean limit superconductivity in Y9Co7 due to the good chemical purity and structural order of the specimen.

ChemInform Abstract: Studies on Icosahedral Ag—In—Yb: A Prototype for Tsai‐Type Quasicrystals

AbstractReview: 81 refs.

Studies on icosahedral Ag–In–Yb: a prototype for Tsai-type quasicrystals

Tsai-type icosahedral quasicrystals (i-QCs) are present in numerous alloy systems. Among them, the icosahedral Ag–In–Yb quasicrystal (i-Ag–In–Yb) is regarded as a prototype for studying various features of QCs, such as crystalline structure and physical properties, due to its good average structural order, good stability both in air and in ultra-high vacuum, amenability to growth of large single grains, and lack of elements with high vapor pressure or toxicity. Here we present a review on recent studies of i-Ag–In–Yb, including studies on bulk structure, crystal growth, physical properties, surface structure and thin film growth on quasicrystalline surface. We believe the results will encourage studies on other QCs.

Quinacridone on Ag(111): Hydrogen Bonding versus Chirality

Quinacridone (QA) has recently gained attention as an organic semiconductor with unexpectedly high performance in organic devices. The strong intermolecular connection via hydrogen bonds is expected to promote good structural order. When deposited on a substrate, another relevant factor comes into play, namely the 2D-chirality of the quinacridone molecules adsorbed on a surface. Scanning tunneling microscopy (STM) images of monolayer quinacridone on Ag(111) deposited at room temperature reveal the formation of quasi-one-dimensional rows of parallel quinacridone molecules. These rows are segmented into short stacks of a few molecules in which adjacent, flat-lying molecules of a single handedness are linked via hydrogen bonds. After annealing to a temperature of T = 550–570 K, which is close to the sublimation temperature of bulk quinacridone, the structure changes into a stacking of heterochiral quinacridone dimers with a markedly different intermolecular arrangement. Electron diffraction (LEED) and photoelectron emission microscopy (PEEM) data corroborate the STM findings. These results illustrate how the effects of hydrogen bonding and chirality can compete and give rise to very different (meta)stable structures of quinacridone on surfaces.

Synthesis of Helical and Supplementary Chirally Doped PMO Materials. Suitable Catalysts for Asymmetric Synthesis

Exciting helical mesoporous organosilicas including supplementary chirally doped moieties into their spiral walls were one-pot successfully synthesized with good structural order for, to the best of our knowledge, the first time. This one-step direct synthesis of helical chirally doped periodic mesoporous organosilica (PMO) materials was carried out by combination of a tartrate-based bis-organosilicon precursor with tetraethyl orthosilicate (TEOS) and two surfactants, cetyltrimethylammonium bromide and perfluoroctanoic acid (CTAB and PFOA). For comparison purposes, a conventional two-step postsynthetic grafting methodology was carried out. In this method, the chiral tartrate-based moieties were grafted onto the helical silica mesoporous materials previously prepared by the dual-templating approach (CTAB and PFOA). The chirally doped materials prepared by both methodologies exhibited helical structure and high BET surface area, pore size distributions, and total pore volume in the range of mesopores. Solid-state (13)C and (29)Si MAS NMR experiments confirmed the presence of the chiral organic precursor in the silica wall covalently bonded to silicon atoms. Nevertheless, one-pot direct synthesis led to a greater control of surface properties and presented larger incorporation of organic species compared with the two-step postsynthetic methodology. To further prove the potential feasibility of these materials in enantiomeric applications, Mannich diastereoselective asymmetric synthesis was chosen as catalytic test. In the case of the one-pot PMO material, the rigidity of the chiral ligand backbone provided by its integration into the inorganic helical wall in combination with the steric impediments supplied by the twisted geometry led to the reagents to adopt specific orientations. These geometrical constrictions resulted in an outstanding diastereomeric induction toward the preferred enantiomer.

A high molecular weight triisopropylsilylethynyl (TIPS)-benzodithiophene and diketopyrrolopyrrole-based copolymer for high performance organic photovoltaic cells

A high-molecular-weight conjugated polymer consisting of alternating TIPS-substituted benzo[1,2-b:4,5-b′]dithiophene (BDT) and diketopyrrolo[3,4-c]pyrrole (DPP) was synthesized by Suzuki cross-coupling and characterized for use in high performance OPVs. Good structural order, self-assembly in spun-cast films, and carrier mobility were observed. PTIPSBDT–DPP showed an OFET hole mobility of up to 0.12 cm2 V−1 s−1. Power conversion efficiencies of up to 8.0% were demonstrated for OPV devices.