Rod-like Aggregates Research Articles

Ionomer Dispersions in Water/Alcohol Solutions by Coarse-Grained Molecular Dynamics

The polymer electrolyte membrane (PEM) is one of the principal components for polymer electrolyte fuel cells. As the phase separation is considered one of the primary factors affecting its performance, the morphological properties of PEM have been studied experimentally and theoretically. Under good solvent conditions for the polymer backbone, where solvents dissolve the backbone chains, ionomers exhibit polyelectrolyte-type behavior, forming loose ionic aggregates. In sufficiently polar solvents, ionomer backbones undergo aggregation and phase separation. This process results in the formation of a solid PEM at high ionomer concentration. Perfluorosulfonic acid (PFSA) ionomers such as Nafion (developed by DuPont) are currently the principal electrolyte and separator materials adopted for use as PEMs. Chemically, Nafion is a random copolymer that consists of hydrophilic sulfonate groups and a hydrophobic polytetrafluoroethylene backbone, which together form microphase-separated higher-order structures. Under sufficiently hydrated conditions, PEMs exhibit high mechanical robustness, warranted by hydrophobic backbone segments, as well as good water retention and high proton conductivity, conferred by the high volumetric ion density. The characterization of the ionomer structures has been extensively studied using experimental measurements such as small-angle neutron scattering (SANS), wide-angle neutron scattering (WANS), small-angle X-ray scattering (SAXS), and nuclear magnetic resonance (NMR). They observed that hydrophobic backbones of Nafion form the cylindrical-like core of self-assembled ionomer structures while ionic groups are located at the periphery of this aggregates. Based on a combination of scattering and microscopy, the rod-like aggregates in well-hydrated PEMs were observed. The proton conductivity and mechanical strength of solution-cast membranes are correlated with the properties of ionomer dispersions in solutions. Theoretically, while most of studies have primarily focused on the solid membrane state with water volume fraction significantly below 50%, ionomer aggregations in solutions can also be an important phenomenon to understand the self-assembly behaviors of ionomers as key structure-forming elements in ionomer films. In this study, ionomer aggregations in water/alcohol solutions have been investigated using coarse-grained (CG) molecular dynamics simulations to understand the dependence of aggregation behaviors on the water and alcohol fractions. The use of CG models is a valuable tool to prove the time and length scales of systems beyond what is feasible with traditional all atom models. Our model has been developed based on the MARTINI force fields, which is in close connection with more detailed atomistic models in terms of thermodynamic data, in particular hydration/partitioning free energies. The whole CG model of Nafion copolymer, as shown in Fig. 1, includes a part of the atomistic level configuration of a Nafion chain. A three-monomer unit of polytetrafluoroethylene (PTFE) (-(CF2)3-) are coarse-grained as a spherical bead of diameter 0.47 nm, and one side chain is coarse-grained as two spherical beads. This model is comparable to the inter-distance of ~2 nm between side chains and a side chain length of ~1 nm in the Nafion ionomer with EW = 1100. To include the effect of polarization in water model, which is significant at the interfaces between water and other phases and in the vicinity of charged particles. The initial configurations were generated by randomly placing 15 ionomer chains in a box with periodic boundary condition in all directions. Water and 1-propanol CG beads were then added based on the water/1-propanol molar fractions. All the solutions were fixed at an ionomer concentration of 5 wt%. The equilibration of the systems was first carried out with NPT MD simulations at T = 300 K and P = 1 atm for 100 ns. The additional NPT ensemble for 50 ns was then performed for the production. The dependence of NPA content on the ionomer structures was studied by systematically changing the NPA content in the system. It was found that ionomers form the bundle-like structures with cylindrical shape as shown in Fig. 2, which are in general agreement with cylindrical-like structures found in experimental scattering measurements of Nafion solutions. The ionomer aggregation size was found to tend to be larger and more dispersive at higher NPA contents, although the ionomers aggregated into one cluster at all NPA contents. Figure 1

Gelation behaviours and gel properties of a dihydrazide derivative

The gelation behaviour and gel properties of the organogels based on a twin-tapered dihydrazide derivative gelator, oxalyl acid N′,N′-di (3,4,5-tripentyloxybenzoyl) hydrazide (FH-T5) in mixtures of ethanol and ethylene glycol were investigated. It was demonstrated that the xerogels in the mixtures of ethanol and ethylene glycol showed the co-existence of sphere-like particles or short rod-like aggregates and fibers, which showed Colh phase. The more ethylene glycol in the mixtures, the shorter the gelation time of FH-T5 when the volume contents of ethylene glycol increased from 0% to 30%, and the kinetics of gelation of FH-T5 showed that Df value of the fibers increased from 1.302 in ethanol to 1.426 in the mixture with 30% ethylene glycol. Gels from the mixture of ethanol and ethylene glycol showed reduced storage modulus, higher Tg and the xerogels obtained from the mixtures exhibited higher wetting angle compared to that from ethanol.

Effects of multifunctional cross-linkers on rheology and adhesion of soft nanostructured materials.

We investigate the nanostructure, the rheology and the adhesion of soft supramolecular materials elaborated by blending monofunctional and multifunctional poly(isobutene) (PIB) chains. Monofunctional PIB chains (PIBUT) are linear and unentangled polymer chains (Mn ≈ 3 kg mol-1) functionalized in the middle by a bis-urea interacting moiety, able to self-associate by four hydrogen bonds. Covalent coupling of monofunctional PIB allows us to synthesize longer chains bearing two or three interacting moieties. These chains are then added to monofunctional PIB to prepare blends containing up to 10% of multifunctional PIB (M-PIBUT). The influence of M-PIBUT on the supramolecular nanostructure, which results from the self-assembly of stickers, is studied by Atomic Force Microscopy and Small Angle X-ray Scattering at room temperature. Multifunctional and monofunctional chains are shown to interact with each other to form bundles of rod-like aggregates. The consequences of these interactions on the rheology of the blends were studied by shear tests in the linear and non linear regimes, below and above the order-disorder transition temperature. A pronounced strengthening effect of M-PIBUT is observed at room temperature: the supramolecular blends become more elastic and are more resistant to creep with increasing concentration of M-PIBUT. The effects of M-PIBUT on the nanostructure and the rheology suggest that M-PIBUT, which can link with more than one supramolecular aggregate, plays the role of a physical cross-linker. The impact of these supramolecular cross-linkers on the adhesion of the blends is studied by probe-tack tests and discussed by analyzing the in situ deformation through the debonding images.

Observation of ionomer in catalyst ink of polymer electrolyte fuel cell using cryogenic transmission electron microscopy

Optimizing the catalyst layer structure is one of the key issues for improving performance despite lower platinum loading. The catalyst ink, consisting of platinum-loaded carbon particles and ionomer dispersed in an aqueous solvent, is a key factor for controlling the structure of the catalyst layer because the catalyst layer is prepared in a wet coating process. For that purpose, we visualized the nanostructure of the ionomer in the catalyst ink by cryogenic electron microscopy, especially cryogenic transmission electron microscopy (cryo-TEM). By cryo-TEM, it was revealed that ionomer molecules formed rod-like aggregates macro-homogeneously in the solvent, and a similar morphology was observed in a carbon-particle-containing solvent. In contrast, ionomer aggregates in the catalyst ink containing platinum nanoparticles loaded on carbon particles were denser in the vicinity of the platinum-loaded carbon particles. That can be attributed to strong interaction between platinum nanoparticles and sulfonic acid groups in the ionomer. It also implies that a good understanding of ionomer morphology in the catalyst ink can play an important role in controlling the catalyst layer microstructure for reducing platinum loading.

Mesoscale Simulation of Asphaltene Aggregation.

Asphaltenes constitute a heavy aromatic crude oil fraction with a propensity to aggregate and precipitate out of solution during petroleum processing. Aggregation is thought to proceed according to the Yen-Mullins hierarchy, but the molecular mechanisms underlying mesoscopic assembly remain poorly understood. By combining coarse-grained molecular models parametrized using all-atom data with high-performance GPU hardware, we have performed molecular dynamics simulations of the aggregation of hundreds of asphaltenes over microsecond time scales. Our simulations reveal a hierarchical self-assembly mechanism consistent with the Yen-Mullins model, but the details are sensitive and depend on asphaltene chemistry and environment. At low concentrations asphaltenes exist predominantly as dispersed monomers. Upon increasing concentration, we first observe parallel stacking into 1D rod-like nanoaggregates, followed by the formation of clusters of nanoaggregates associated by offset, T-shaped, and edge-edge stacking. Asphaltenes possessing long aliphatic side chains cannot form nanoaggregate clusters due to steric repulsions between their aliphatic coronae. At very high concentrations, we observe a porous percolating network of rod-like nanoaggregates suspended in a sea of interpenetrating aliphatic side chains with a fractal dimension of ∼2. The lifetime of the rod-like aggregates is described by an exponential distribution reflecting a dynamic equilibrium between coagulation and fragmentation.

The collagen type I segment long spacing (SLS) and fibrillar forms: Formation by ATP and sulphonated diazo dyes

The collagen type I segment long spacing (SLS) crystallite is a well-ordered rod-like molecular aggregate, ∼300nm in length, which is produced in vitro under mildly acidic conditions (pH 2.5–3.5) in the presence of 1mM ATP. The formation of the SLS crystallite amplifies the inherent linear structural features of individual collagen heterotrimers, due to the punctate linear distribution and summation of the bulkier amino acid side chains along the length of individual collagen heterotrimers. This can be correlated structurally with the 67nm D-banded collagen fibril that is found in vivo, and formed in vitro. Although first described many years ago, the range of conditions required for ATP-induced SLS crystallite formation from acid-soluble collagen have not been explored extensively. Consequently, we have addressed biochemical parameters such as the ATP concentration, pH, speed of formation and stability so as to provide a more complete structural understanding of the SLS crystallite. Treatment of collagen type I with 1mM ATP at neutral and higher pH (6.0–9.0) also induced the formation of D-banded fibrils. Contrary to previous studies, we have shown that the polysulphonated diazo dyes Direct red (Sirius red) and Evans blue, but not Congo red and Methyl blue, can also induce the formation of SLS-like aggregates of collagen, but under markedly different ionic conditions to those employed in the presence of ATP. Specifically, pre-formed D-banded collagen fibrils, prepared in a higher than the usual physiological NaCl concentration (e.g. 500mM NaCl, 20mM Tris-HCl pH7.4 or x3 PBS), readily form SLS aggregates when treated with 0.1mM Direct red and Evans blue, but this did not occur at lower NaCl concentrations. These new data are discussed in relation to the anion (Cl−) and polyanion (phosphate and sulphonate) binding by the collagen heterotrimer and their likely role in collagen fibrillogenesis and SLS formation.

Super organogelator based on tetrathiafulvalene with four amide derivatives and its F4TCNQ charge-transfer complex

A new series of tetrathiafulvalene-based organogelators endowed with four hydrophobic chains incorporating amide groups was synthesised and characterised. The resulting transparent organogels were obtained with organic solvents such as cyclohexane, carbon tetrachloride and chlorobenzene. Additionally, the length of the alkyl chain influenced the gelation ability of organogels. Considering the results, we concluded that compounds were ‘super gelators’. Interestingly, the gelators reacted with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane to form charge-transfer (CT) complexes and binary organogels. 1HNMR and FT-IR revealed that cooperation of hydrogen bonding, π–π and CT interactions was the main driving force for formation of the native and CT gels. The scanning electron microscopy images of native xerogels revealed characteristic gelation morphologies of three-dimensional cross-linking networks, whereas the morphologies of CT complex xerogels showed amorphous rod-like aggregates. X-ray powder diffraction studies suggested that both gelator and CT complex maintained lamellar molecular packing mode in organogel phase.

Synthesis of Cationic Amphiphilic Block Copolymers Poly(4-vinylbenzyltriethylammonium chloride)-b-Poly(styrene) and Their Self-Assembly in Aqueous Solution.

Well defined two kinds of cationic amphiphilic block copolymers Poly(4-vinylbenzyltriethylammonium chloride)-b-Poly(styrene) are synthesized by combining reversible addition fragmentation chain transfer polymerizations and post-polymerization quaternization. Block copolymers are characterized by GPC and IHNMR. The self-assembly behaviors of the block copolymers are studied, which are characterized by TEM. For Poly(4-vinylbenzyltriethylammoniurn chloride)13-b-Poly(styrene)136, crew-cut spherical micelles are obtained by using DMF as the initial common solvent, and the majority of the pearl series aggregates and a small-amount of rod-like aggregates are all observed by using the mixture of DMF and THF as the initial common solvent. The formation process of rod-like aggregates is proposed in three steps: the micellization of copolymer chains, the formation of pearl series aggregates from the collision and fusion of individual initial spherical micelles, and the transformation from pearl series aggregates to rod-like aggregates. For Poly(4- vinylbenzyltriethylammonium chloride)18-b-Poly(styrene)370, large compound micelles and complicated spherical aggregates and small vesicles are all,obtained. The formation process of small vesicles is also proposed in three steps: the formation of initial spherical micelles with some hydrophilic block Poly(4-vinylbenzyltriethylammonium chloride) embedded in the core, the removing of the outer layer common solvent, and solvent nucleation in the center. It should be noted that solvent nucleation is critical, because of the hydrophilic block Poly(4-vinylbenzyltriethylammonium chloride) and the common solvent and water embedded in the core of the initial spherical micelles.

Dispersion stability of non-refined turnip rapeseed (Brassica rapa) protein concentrate: Impact of thermal, mechanical and enzymatic treatments

Aqueous dispersion properties of a protein concentrate obtained from turnip rapeseed (Brassica rapa) press cake were investigated. Protein content of the press cake was enriched from 35.9% to 45.8% by sequential supercritical-CO2 extraction, milling and air classification. The protein denaturation degree and the solubility in the prepared protein concentrate were compared with a commercial canola protein isolate. Partial loss of the protein native structure was observed in the protein concentrate. The ζ-potential in the soluble fraction of the protein concentrate dispersion was ca. 20mV lower (more negative) compared with the commercial isolate at pHs 4–10, which was attributed to the presence of charged carbohydrates such as pectin in the protein concentrate. To improve the dispersion stability of the protein concentrate, enzymatic crosslinking with transglutaminase and microfluidization at 1850 bars were applied. Microfluidization resulted in the formation of rod-like aggregates formed mainly of the insoluble cell wall polysaccharides glued together with proteins as imaged by confocal laser scanning microscopy. Improvement in colloidal stability was observed in all samples upon microfluidization. Pre-treatment with transglutaminase resulted in different distributions of the components in the rods and further improved dispersion stability against sedimentation. Heat treatment caused compaction of the structures.

Particle-directed assembly of semiflexible polymer chains.

We use Langevin dynamics simulations to study aggregation of semiflexible polymers driven by attractions between polymers and spherical particles. We consider a simple model with purely repulsive polymer/polymer and particle/particle interactions but attractive polymer/particle interactions. We find a rich "phase diagram" that contains several different types of globular and rod-like aggregates with either liquid-like or crystalline structure for the particle positions. Systems that exhibit rod-like aggregates with crystalline internal order exhibit a discontinuous rod-globule transition, while systems with liquid-like internal order exhibit a smooth crossover between isotropic and elongated aggregates with increasing chain stiffness. Polymers in elongated liquid-like aggregates often adopt helical configurations that wind around the axis of the aggregate.

A hypothetical hierarchical mechanism of the self-assembly of the Escherichia coli RNA polymerase σ(70) subunit.

Diverse morphology of aggregates of amyloidogenic proteins has been attracting much attention in the last few years, and there is still no complete understanding of the relationships between various types of aggregates. In this work, we propose the model, which universally explains the formation of morphologically different (wormlike and rodlike) aggregates on the example of a σ(70) subunit of RNA polymerase, which has been recently shown to form amyloid fibrils. Aggregates were studied using AFM in solution and depolarized dynamic light scattering. The obtained results demonstrate comparably low Young's moduli of the wormlike structures (7.8-12.3 MPa) indicating less structured aggregation of monomeric proteins than that typical for β-sheet formation. To shed light on the molecular interaction of the protein during the aggregation, early stages of fibrillization of the σ(70) subunit were modeled using all-atom molecular dynamics. Simulations have shown that the σ(70) subunit is able to form quasi-symmetric extended dimers, which may further interact with each other and grow linearly. The proposed general model explains different pathways of σ(70) subunit aggregation and may be valid for other amyloid proteins.

Adhesion and non-linear rheology of adhesives with supramolecular crosslinking points.

Soft supramolecular materials are promising for the design of innovative and highly tunable adhesives. These materials are composed of polymer chains functionalized by strongly interacting moieties, sometimes called "stickers". In order to systematically investigate the effect of the presence of associative groups on the debonding properties of a supramolecular adhesive, a series of supramolecular model systems has been characterized by probe-tack tests. These model materials, composed of linear and low dispersity poly(butylacrylate) chains functionalized in the middle by a single tri-urea sticker, are able to self-associate by six hydrogen bonds and range in molecular weight (Mn) between 5 and 85 kg mol(-1). The linear rheology and the nanostructure of the same materials (called "PnBA3U") were the object of a previous study. At room temperature, the association of polymers via hydrogen bonds induces the formation of rod-like aggregates structured into bundles for Mn < 40 kg mol(-1) and the behavior of a soft elastic material was observed (G'≪G'' and G'∼ω(0)). For higher Mn materials, the filaments were randomly oriented and the polymers displayed a crossover towards viscous behavior although terminal relaxation was not reached in the experimental frequency window. All these materials show, however, similar adhesive properties characterized by a cohesive mode of failure and low debonding energies (Wadh < 40 J m(-2) for a debonding speed of 100 μm s(-1)). The debonding mechanisms observed during the adhesion tests have been investigated in detail with an Image tools analysis developed by our group. The measure of the projected area covered by cavities growing in the adhesive layer during debonding can be used to estimate the true stress in the walls of the cavities and thus to characterize the in situ large strain deformation of the thin layer during the adhesion test itself. This analysis revealed in particular that the PnBA3U materials with Mn < 40 kg mol(-1) soften very markedly at large deformation like yield stress fluids, explaining the low adhesion energies measured for these viscoelastic gels.

Self-assembled vesicle and rod-like aggregates of functionalized perylene diimide: reaction-based near-IR intracellular fluorescent probe for selective detection of palladium.

Herein, we report design, synthesis, and self-assembly of perylene diimide (PDI) based near-IR intracellular probe (PS-PDI). PS-PDI molecules undergo aggregation to form self-assembled nanospheres and nanorods morphology in THF : H2O (1 : 1) and DMSO : H2O (1 : 9), respectively. The nanospheres have an open hole on surface reminiscent of vesicle structure (with a diameter of internal void in the range of 20-25 nm) whereas lengths of the nanorods extended up to few μm range. The Pd0 based depropargylation leads to de-aggregation of these PS-PDI aggregates into smaller spherical aggregates as evidenced by DLS, SEM, and TEM studies. Interestingly, these aggregates of PS-PDI in solution show highly sensitive behavior in the presence of Pd0 showing absorbance changes in NIR region (λmax = 710 nm) and quenching of emission at λem 630 nm (DMSO : H2O, 1 : 9) with a limit of detection = 6.6 × 10-9 M or at λem 564 nm (THF : H2O, 1 : 1) with limit of detection = 2.1 × 10-8 M. Time and concentration dependent kinetics profiles of PS-PDI aggregates revealed an impressive rate constant value of 0.4 s-1 and 0.21 s-1 (DMSO : H2O, 1 : 9), respectively in fluorescence and UV-Vis spectroscopy using 2 × 10-5 M concentration of Pd0. PS-PDI undergoes rapid internalization into HeLa cells with low cytotoxicity and was successfully used as an intracellular imaging reagent for Pd0 in live HeLa cells. For practical applications, we exploited these nano-aggregates of PS-PDI for estimation of Pd2+ in the presence of a NaBH4-PPh3 mixture, Pd0 in drug and environmental samples, and Pd2+ in urine samples with excellent selectivity and sensitivity.

Rod-like architecture and cross-sectional structure of an amyloid protofilament-like peptide supermolecule in aqueous solution

A β-sheet-forming peptide conjugated with a water-soluble moiety (polyethylene glycol (PEG) or a transactivator of transcription (TAT) sequence) forms rod-like aggregates in aqueous solution. We explored the detailed structures of the aggregates using Synchrotron X-ray scattering. We found that the β-sheet-forming peptide indeed formed stacked β-sheets, in a manner similar to that observed in the case of amyloid protofilaments. We also found that the resultant rod-like objects could be completely dispersed in water, as a result of the hydrophilicity of PEG or TAT.

Early aggregation preceding the nucleation of insulin amyloid fibrils as monitored by small angle X-ray scattering.

The nucleation event of amyloid fibrils is one of the most crucial processes that dictate the timing and rate of the pathology of diseases; however, information regarding how protein molecules associate to produce fibril nuclei is currently limited. In order to explore this issue in more detail, we performed time-resolved small angle X-ray scattering (SAXS) measurements on insulin fibrillation, in combination with additional multidirectional analyses of thioflavin T fluorescence, FTIR spectroscopy, light scattering, and light transmittance, during the fibrillation process of bovine insulin. SAXS monitoring revealed that insulin molecules associated into rod-like prefibrillar aggregates in the very early stage of the reaction. After the formation of these early aggregates, they appeared to further coalesce mutually to form larger clusters, and the SAXS profiles subsequently showed the further time evolution of conformational development towards mature amyloid fibrils. Distinct types of structural units in terms of shape in a nano-scale order, cross-β content, and thioflavin T fluorescence intensity were observed in a manner that was dependent on the fibrillation pathways. These results suggest the presence of diverse substructures that characterize various fibrillation pathways, and eventually, manifest polymorphisms in mature amyloid fibrils.

Hexaphenylbenzene-Stabilized Luminescent Silver Nanoclusters: A Potential Catalytic System for the Cycloaddition of Terminal Alkynes with Isocyanides.

A hexaphenylbenzene (HPB)-based derivative bearing thiol groups has been designed and synthesized that undergoes aggregation-induced emission enhancement in mixed aqueous media to form rodlike fluorescent aggregates. These rodlike aggregates behave as a "not quenched" probe for the detection of silver ions and further act as reactors and stabilizers for reducing-agent-free preparation of blue luminescent silver nanoclusters at room temperature. The utilization of fluorescent supramolecular aggregates for the preparation of Ag NCs in mixed aqueous media is unprecedented in the literature. Moreover, the wet chemical method that we are reporting in the present paper for the preparation of luminescent silver nanoclusters is better than the other methods reported in the literature. Further, these in situ generated Ag NCs showed exceptional catalytic activity in the preparation of pyrroles involving cocyclization of isocyanides and terminal alkynes. Interestingly, the catalytic efficiency of in situ generated Ag NCs was found to be better than the other catalytic systems reported in the literature.

Formation of rod-like nanostructure by aggregation of TiO2 nanoparticles with improved performances

To improve the performance of titanium dioxide (TiO2)-based devices, many efforts have been made to prepare nanostructures with composite of TiO2 nanoparticles and nanorods. In this work, a novel rod-like TiO2 nanostructure was obtained via a controllable hydrolysis process. Morphology and structure analysis showed that the rod-like nanostructure was a well-aligned aggregate of nearly spherical TiO2 nanoparticles. Rod-like TiO2 nanoparticle aggregates were fabricated on a primary TiO2 nanoparticle-based layer without the use of template, and formed a hierarchical TiO2 composite film together. The photocatalytic activity of the TiO2 film with rod-like nanoparticle aggregates was evaluated by the degradation of methylene blue. The antibacterial activity of fabricated hierarchical TiO2 film was assessed against Staphylococcus aureus. The photoelectrochemical property of this film as the photoanode in assemble dye-sensitized solar cell was also tested. Compared with randomly distributed nanoparticle-based TiO2 film, the hierarchical TiO2 film exhibited improved performance of photocatalysis, antibacterial activity and photoelectric conversion.

CoFe/SBA-15 catalyst coupled with peroxymonosulfate for heterogeneous catalytic degradation of rhodamine B in water

CoFe/SBA-15 catalysts were prepared by simultaneous incipient wetness impregnation using Co(NO3)2·6H2O and Fe(NO3)3·9H2O as the precursors and SBA-15 as the support. The catalysts were used to activate generation of sulfate radicals from peroxymonosulfate (PMS) for rhodamine B (RhB) dye degradation in aqueous solutions. The catalyst was characterized using X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy and energy-dispersive X-ray spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. The effects of the Co and Fe loadings and calcination temperature on the catalytic performance, catalyst reusability, and kinetics and mechanism of catalytic oxidative degradation of RhB in the presence of CoFe/SBA-15 and PMS were investigated. The results show that the predominant Co-Fe oxide loaded on the support was the composite CoFe2O4, which provided the active catalytic sites, and was present in the SBA-15 matrix. The surface area, pore volume, and mean pore diameter of 10Co9.5Fe/SBA-15-700 were 506.1 m2/g, 0.669 cm3/g, and 7.4 nm, respectively, lower than those of SBA-15. 10Co9.5Fe/SBA-15-700 consisted of rod-like aggregates with diameters greater than 0.25 μm. It had a magnetic intensity of 8.3 emu/g; therefore, magnetic separation was feasible. 10Co9.5Fe/SBA-15-700 showed good catalytic activity and stability, with a RhB degradation rate higher than 96% and Co leaching lower than 32.4 μg/L. The catalytic oxidative degradation of RhB in the presence of FeCo/SBA-15 and PMS obeyed first-order kinetics, and the degradation rate increased with increasing CoFe/SBA-15 and PMS dosages and with decreasing initial reactant concentrations. Quenching tests showed that sulfate radicals played a dominant role in RhB catalysis. CoFe/SBA-15 maintained high catalytic activity and good stability during 10 recycling runs, with a RhB degradation rate greater than 84%, Co and Fe leaching for each run lower than 72.1 and 35 μg/L, respectively. CoFe/SBA-15 is an efficient catalyst for PMS oxidation, and has potential applications in the removal of refractory organics such as RhB in water.

Characteristics of PM10 and PM2.5 at Mount Wutai Buddhism Scenic Spot, Shanxi, China

A survey was conducted to effectively investigate the characteristics of airborne particulate pollutants PM10 and PM2.5 during the peak tourist season at Mount Wutai Buddhism scenic spot, Shanxi, China. Characteristics of the PM10 and PM2.5 in Wu Ye Temple (core incense burners), Manjusri Temple (a traffic hub), Yang Bai Lin Village (a residential district), and Nan Shan Temple (located in a primitive forest district), were determined. The results showed that the PM10 concentration was more than 1.01–1.14 times higher than the threshold (50 μg/m3) of World Health Organization Air Quality Guidelines (2005), and the PM2.5 concentration was 1.75–2.70 times higher than the above standard (25 μg/m3). Particle size analysis indicated that the distribution of fine particulate matter in Wu Ye Temple ranged from 0 to 3.30 μm. In other sampling points, the fine particulate was mainly distributed in the range of 0–5.90 μm. The particulates in Wu Ye Temple were mainly characterized by spherical, rod-like, and irregular soot aggregates (PM10) and spherical particles of dust (PM2.5). Manjusri Temple and Yang Bai Lin Village predominantly exhibited irregular soil mineral particulate matter (PM10), and amorphous ultrafine soot particulate matter (PM2.5).

Far-Red and Near-IR AIE-Active Fluorescent Organic Nanoprobes with Enhanced Tumor-Targeting Efficacy: Shape-Specific Effects.

The rational design of high-performance fluorescent materials for cancer targeting in vivo is still challenging. A unique molecular design strategy is presented that involves tailoring aggregation-induced emission (AIE)-active organic molecules to realize preferable far-red and NIR fluorescence, well-controlled morphology (from rod-like to spherical), and also tumor-targeted bioimaging. The shape-tailored organic quinoline-malononitrile (QM) nanoprobes are biocompatible and highly desirable for cell-tracking applications. Impressively, the spherical shape of QM-5 nanoaggregates exhibits excellent tumor-targeted bioimaging performance after intravenously injection into mice, but not the rod-like aggregates of QM-2.