Scattering Electron Microscopy Research Articles

Structural characterization of Chloride Salt of conducting polyaniline obtained by XRD, SAXD, SAXS and SEM

Emeraldine-salt polyaniline form (ES-PANI) was chemically synthesized using hydrochloric acid at time synthesis ranging from 0.5 to 48h and characterized by X-ray diffraction (XRD), LeBail fit, Small-angle X-ray diffraction (SAXD), Small-angle X-ray Scattering (SAXS) and Scanning Electron Microscopy (SEM). Crystallinity and crystal data (a=5.7122, b=17.8393, c=22.8027, α=83.1575, β=84.6971 and γ=88.4419) were obtained by XRD and showed that the crystallinity did not vary with the time synthesis. LeBail fit revealed that the crystallites were very small lamellae with global average size around 39Å. By SAXS it was obtained the particle Radius of Giration (Rg) of 320Å. The maximum particle size (Dmax) of 650Å was obtained from the pair-distance distribution function (p(r)). SEM images showed a fiber morphology formed by interconnected non homogeneous nanospheres. Electrical conductivity of the samples was in ∼1.84×10−4S/cm.

Aggregation Behavior of Bovine κ- and β-Casein Studied with Small Angle Neutron Scattering, Light Scattering, and Cryogenic Transmission Electron Microscopy

In the native bovine casein micelle the calcium sensitive caseins (α(S1)-, α(S2)- and β-casein) sequester amorphous calcium phosphate in nanometer-sized clusters, whereas the calcium-insensitive κ-casein limits the growth of the micelle. In this paper, we further investigate the self-association of κ- and β-casein, which are two of the key proteins that control the substructure of the milk casein micelle, using neutron and light scattering techniques and cryogenic transmission electron microscopy. Results demonstrate that κ-casein can, apart from the known self-assembly, form amyloid-like fibrils already at temperatures of 25 °C when subject to agitation. This extended aggregation behavior of κ-casein is inhibited by β-casein, as reported by others. These findings have implications for the structure and stability of casein micelles. The neutron scattering data was used to gain information on the self-assembly structure of κ-casein. β-Casein shows similar self-association behavior as κ-casein, but unlike κ-casein, the self-association exhibits temperature dependence within the studied temperatures (6 and 25 °C). Here, we will discuss our extended study of the known self-assembly of casein in the context of the fibrillation of κ-casein.

Synthesis of Stable Magnetic Nanofluids of Different Particle Sizes

Highly stable suspensions of Fe3O4 nanoparticles are produced by simple co-precipitation approach, combined with dynamic coating of surfactant where the particle size is controlled by varying reaction temperature. The size, distribution and morphology of magnetite nanoparticles are measured by using the X-ray diffraction (XRD), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). The XRD patterns of particles prepared at incubation temperatures 30, 50, 60 and 70 C show the cubic crystal structure of magnetite. The particles size and saturation magnetization values are found to increase with increase in incubation temperature due to a decrease in supersaturation at elevated temperature. The average size of the particles obtained by light scattering are higher than the values obtained by XRD due to the adsorbed surfactant layer. The Mossbauer data shows an intensified central doublet due to the superparamagnetic nature of particles and two sextets due to the two structurally different iron sites in the material. The narrow size distribution of the particles and the long term stability of the dispersions are attributed to the presence of a monolayer of surfactant on individual particles, as confirmed by thermogravimetric analysis.

Preparation and self-assembly of two-length-scale A-b-(B-b-A)n-b-B multiblock copolymers

A-b-(B-b-A)n-b-B multiblock copolymers composed of short middle diblock units (B-b-A)n and two long A- and B-outer blocks were successfully prepared. The multiblock copolymers consist of polystyrene (S) and poly(p-hydroxystyrene) (pHS) and were prepared through sequential anionic polymerization of styrene and 4-tert-butoxystyrene, followed by hydrolysis of the tert-butoxy group. A hexablock and an octablock copolymer with a low overall polydispersity were synthesized. The self-assembled structures were investigated using Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM). Due to the smaller number of inner blocks and their relatively small molar mass, a single periodic lamellar morphology was observed for the hexablock copolymer while a lamellar-in-lamellar morphology with two thin layers within successive thick layers was observed for the octablock copolymer with larger middle diblock units. These observations are in excellent agreement with existing theories.

Bottom-up/top-down synthesis of stable zirconium hydroxide nanophases

It is well known that the structure of ZrO2 powder synthesized by low temperature calcination of hydrous zirconia is strongly affected by the nature and properties of precursors. In the present paper, we combined a precipitation/restructuring approach (bottom-up/top-down methodology) to produce zirconium hydroxide nanoparticles that transform into stable nanophasic tetragonal zirconia by low temperature calcination. The dimension and structure of precursors could be modulated by adjusting pH. The synthetic route was investigated by Raman spectroscopy, X-Ray Diffraction, Small-Angle X-Ray Scattering and High-Resolution Transmission Electron Microscopy. The zirconium hydroxide nanoparticles represent the final product of the overall process, which starts as a bottom-up synthesis of the hydroxide gel, followed by a top-down reorganization stage. During this rearrangement, the evolving structure passes through a mass fractal that arises from the clustering of the primary zirconium hydroxide nano-units.

Morphology control of gold nanoparticles on glass surface realized by electric field assisted dissolution method

Noble metal nanoparticles have potential applications in photonics, catalysis, and bio-labeling, owing to their much unique optical properties and surface activities. Monodisperse spherical Au nanoparticles with sizes in a range of about 60-80 nm are formed on the glass surfaces via ion sputtering and follow-up heat treatment. At an appropriate temperature, the electric field assisted dissolution process of Au nanoparticles is realized by the strong direct current electric field in step-like feature. In the different color areas of glass surface, it can be found that the original spherical Au nanoparticles are dissolved into the particles with the shape of a lunar eclipse. From surface plasmon resonance absorption properties and scattering electron microscopy images of Au nanoparticles in the different color areas, the influence of experimental condition on property of gold nanoparticle is demonstrated. From the current-voltage characteristics in electric field assisted dissolution experimental process, the physical process of Au nanoparticle dissolution under strong direct current electric field is analysed: the tunneling process of ejected electrons from Au particles to the anode starts, then followed by transfer process of Au cations to the glass matrix and the combination process of electrons from cathode with a positive charge Au particles. The physical mechanism of morphology control of Au nanoparticles realized by electric field assisted dissolution method is discussed in detail.

Bicontinuous nanodisc and nanospherical titania materials prepared by sol-gel process in reverse microemulsion

AbstractTiO2 nanoparticles with different shapes and sizes were synthesised by the sol-gel route in Water/Brij78/Hexane reverse microemulsions. The aqueous cores of these microemulsions were used as nanoreactors to control sol-gel reactions. We studied the effect of water/surfactant mole ratio (W 0) on the morphology, and textural properties of the final products. The materials thus obtained were characterised by different techniques. Thermogravimetric and differential thermal analysis (TG-DTA) was used to study the thermal behaviour of the products and X-ray diffraction (XRD) to identify the crystalline phases. The morphological and textural properties of the products were determined by scattering electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) method, respectively. We also studied the influence of thermal treatment on the structure and size of the TiO2 particles. The effect of W 0 on the anatase-rutile phase transition temperature was investigated.

Multiscale characterization of filler dispersion and origins of mechanical reinforcement in model nanocomposites

We report on the influence of parameters controlling filler dispersion and mechanical reinforcement in model nanocomposites. We elaborate a series of nanocomposites and present a structural characterization of silica dispersion in polymer matrix for several particle sizes and polymer matrices, at all relevant scales, by coupling Small Angle X-ray Scattering and Transmission Electronic Microscopy. The mechanical properties are investigated in the linear regime by coupling Dynamical Mechanical Analysis and plate/plate rheology. The results show that: (i) for all filler sizes and matrices, a structural transition is observed from non-connected fractal aggregates at low silica concentration to connected network at high particle content. (ii) In the dilute regime, the reinforcement implies a polymer chain contribution with different possible origins: increase of entanglements density for PS and increase of friction coefficient for PMMA. (iii) In the concentrated regime, for a given polymer, the reinforcement amplitude can be tuned by the rigidity of the filler network, which directly depends on the particle–particle interaction.

PVC-silica hybrids: effect of sol–gel conditions on the morphology of silica particles and thermal mechanical properties of the hybrids

Hybrid materials from poly(vinyl chloride) (PVC) and silica have been prepared using different conditions by the sol–gel technique. In situ generation of silica network in the PVC matrix was carried out by hydrolysis/condensation of tetraethoxysilane (TEOS) in the matrix. Morphology of the silica particles produced in hybrid films was studied by scattering electron microscopy. The shape of silica particle produced in the matrix was modified by carrying out the sol–gel process under steam on the hybrid films using TEOS. The films were subjected to strain conditions during this process, which produced lamellar shaped particles in the matrix. It was possible to produce platelet type of structure with different aspect ratio by changing the composition and the stress conditions on the films during the steaming process. Addition of a very small amount of γ-glycidoxypropyltrimethoxysilane as compatibilizer drastically reduced the silica particles size in the matrix to nano-level. Thermal–mechanical properties of some of these hybrids were studied and related to the composition, structure and inter-phase interaction between the silica and the matrix.

Synthesis and characterization of cellulose whiskers/polymer nanocomposite dispersion by mini-emulsion polymerization

Stable film-forming nanocomposite particles with diameters ranging from 120 to 300 nm, based on polybutylmethacrylate (PBMA) and cellulose whiskers in water dispersions, were successfully synthesized in one step through mini-emulsion polymerization. The nanocomposite dispersion with a solid content of 25 wt.% and up to 5 wt.% of nanofiller loading was prepared by in situ polymerization, in the presence of the whiskers using dodecylpyridinium chloride (DPC), as a cationic surfactant, and 2,2-azobis(isobutyronitrile) (AIBN), as initiator. The electrostatic interaction between the positively charged droplets and negatively charged whiskers ensured the anchoring of the nanofiller around the polymer particles. The ensuing dispersions were characterized by Dynamic Light Scattering (DLS), ζ-Potential Measurements, and Field-Emission Scanning Electron Microscopy (FE-SEM). After the film formation process, the nanocomposite film exhibits a high transparency, denoting the good dispersion of the whiskers throughout the matrix.

DODAB:monoolein-based lipoplexes as non-viral vectors for transfection of mammalian cells

DNA/Cationic liposome complexes (lipoplexes) have been widely used as non-viral vectors for transfection. Neutral lipids in liposomal formulation are determinant for transfection efficiency using these vectors. In this work, we studied the potential of monoolein (MO) as helper lipid for cellular transfection. Lipoplexes composed of pDNA and dioctadecyldimethylammonium bromide (DODAB)/1-monooleoyl-rac-glycerol (MO) at different molar ratios (4:1, 2:1 and 1:1) and at different cationic lipid/DNA ratios were investigated. The physicochemical properties of the lipoplexes (size, charge and structure), were studied by Dynamic Light Scattering (DLS), Zeta Potential (ζ) and cryo-transmission electron microscopy (cryo-TEM). The effect of MO on pDNA condensation and the effect of heparin and heparan sulphate on the percentage of pDNA release from the lipoplexes were also studied by Ethidium Bromide (EtBr) exclusion assays and electrophoresis. Cytotoxicity and transfection efficiency of these lipoplexes were evaluated using 293T cells and compared with the golden standard helper lipids 1,2-dioleoyl-sn-glycero-3-hosphoethanolamine (DOPE) and cholesterol (Chol) as well as with a commercial transfection agent (Lipofectamine™ LTX). The internalization of transfected fluorescently-labeled pDNA was also visualized using the same cell line. The results demonstrate that the presence of MO not only increases pDNA compactation efficiency, but also affects the physicochemical properties of the lipoplexes, which can interfere with lipoplex-cell interactions. The DODAB:MO formulations tested showed little toxicity and successfully mediated in vitro cell transfection. These results were supported by fluorescence microscopy studies, which illustrated that lipoplexes were able to access the cytosol and deliver pDNA to the nucleus. DODAB:MO-based lipoplexes were thus validated as non-toxic, efficient lipofection vectors for genetic modification of mammalian cells. Understanding the relation between structure and activity of MO-based lipoplexes will further strengthen the development of these novel delivery systems.

Understanding of the Relaxor Behaviors : Comprehensive Investigations from Polarization, Raman Scattering and Transmission Electron Microscopy Observations(Current Topics)

Understanding of the Relaxor Behaviors : Comprehensive Investigations from Polarization, Raman Scattering and Transmission Electron Microscopy Observations(Current Topics)

Complex morphologies of self-assembled block copolymer micelles in binary solvent mixtures: the role of solvent–solvent correlations

The morphologies and sizes of micellar aggregates, composed of the tri-block copolymer P123 (EO20PO70EO20) in a mixture of the aprotic solvent N,N-dimethylformamide (DMF) and water, were investigated by combining Dynamic Light Scattering (DLS) and Cryogenic Transmission Electron Microscopy (cryo-TEM) experiments. At water concentrations between about 27 and 35 wt% bicontinuous micelles with distinct patterns were formed, in coexistence with very long, non-branched, worm-like micelles. Water concentration affects both the size and the morphology of the micellar aggregates. A careful study of the pure binary solvent mixture revealed the presence of dynamic solvent domains of nanometric size, even in the absence of copolymer. Strikingly, the size of these solvent nano-domains closely matched the size of the bicontinuous micelles in a polymer solution for the same water/DMF ratios. We discuss these findings in terms of spinodal decomposition of the polymer solution, in which two-solvent domains contain solvent quality fluctuations that could determine the decomposition. In addition, we suggest another “soft confinement” mechanism that could be responsible for the formation of bicontinuous micelles. The local excess of one of the solvent species in the nano-domains could entrap a metastable morphology.

Skin Delivery of Ferulic Acid from Different Vesicular Systems

The aim of the present research is to evaluate the skin delivery capabilities of different vesicular systems, including conventional liposomes (CL), Tween 80-based deformable liposomes (DL), invasomes (INS) and ethosomes bearing ferulic acid (FA) being an antioxidant exhibiting a wide range of therapeutic effects against various diseases. All of the test formulations were characterized for particle size distribution, zeta-potential, vesicular shape and surface morphology, in vitro human skin permeation and skin deposition. Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) defined that all of liposomal vesicles were almost spherical, displaying unilamellar structures with low polydispersity (PDI < 0.2) and nanometric size range (z-average no more than 150 nm). In addition, all the vesicular systems except conventional liposomes were negatively charged to a certain extent. In vitro skin permeation and skin deposition experiments demonstrated that the permeation profile of ferulic acid through human stratum corneum epidermis membrane (SCE) and the drug deposition in skin were both improved significantly using these vesicular liposomal systems. Permeation and skin deposition enhancing effect was highlighted by the ethosomal system containing 18.0 mg/ml of ferulic acid with an significantly (P < 0.01) enhanced skin flux (267.8 +/- 16.77 microg/cm2/h) and skin drug deposition (51.67 +/- 1.94 microg/cm2), which was 75 times and 7.3 times higher than those of ferulic acid from saturated PBS (pH 7.4) solution, respectively. This study demonstrated that ethosomes are promising vesicular carriers for delivering ferulic acid into or across the skin.

The influence of dipalmitoyl phosphatidylserine on phase behaviour of and cellular response to lyotropic liquid crystalline dispersions

Lyotropic liquid crystalline nanoparticles (cubosomes) have the potential to act as amphiphilic scaffolds for the presentation of lipids and subsequent application in, for example, bioseparations and therapeutic delivery. In this work we have formulated lyotropic liquid crystalline systems based on the synthetic amphiphile 1,2,3-trihydroxy-3,7,11,15-tetramethylhexadecane (phytantriol) and containing the lipid dipalmitoyl phosphatidylserine (DPPS). We have prepared a range of DPPS-containing phytantriol cubosome formulations and characterized them using Small Angle X-ray Scattering and Cryo-transmission electron microscopy. These techniques show that increased DPPS content induces marked changes in lyotropic liquid crystalline phase behaviour, characterized by changes in crystallographic dimensions and increases in vesicle content. Furthermore, in vitro cell culture studies indicate that these changes correlate with lipid/surfactant cellular uptake and cytotoxicity. A model cell membrane based on a surface supported phospholipid bilayer was used to gain insights into cubosome–bilayer interactions using Quartz Crystal Microgravimetry. The data show that mass uptake at the supported bilayer increased with DPPS content. We propose that the cytotoxicity of the DPPS-containing dispersions results from changes in lipid/surfactant phase behaviour and the preferential attachment and fusion of vesicles at the cell membrane.

Combining back scattered electron microscopy and secondary emission scanning electron microscopy to study articular cartilage morphology without decalcifying and staining the samples

Combining back scattered electron microscopy and secondary emission scanning electron microscopy to study articular cartilage morphology without decalcifying and staining the samples

A new type of microemulsion consisting of two halogen-free ionic liquids and one oil component

A ternary system consisting of toluene, as oil phase, and two ionic liquids, i.e., 1-butyl-3-methylimidazolium octylsulfate (bmimOctOSO 3) and 1-ethyl-3-methylimidazolium ethylsulfate (emimEtOSO 3), has been investigated. The isotropic phase region was studied by means of conductometric, cyclic voltammetric and rheological measurements. The results show that microemulsions can be formed, where the bmimOctOSO 3 take over the role of a surfactant in the spontaneous interfacial film formation process. Changes in the droplet–droplet exchange process can be assigned to transitions in the microstructure of the system from the IL-in-oil to oil-in-IL microemulsions, passing a bicontinuous phase. In the region between 5 wt.% and 21 wt.% of emimEtOSO 3, reverse microemulsions with a droplet size of 2–10 nm were detected using Dynamic Light Scattering (DLS) and Cryo-Scanning Electron Microscopy (Cryo-SEM).

Synthesis of Co3W–Cu composite nanopowders by mechanical milling and hydrogen reduction process

In this research, synthesis of Co3W–Cu composite nanopowders based on Co3W intermetallic compound by mechanical milling and hydrogen reduction process was investigated. Powder mixture of Co3O4, WC and CuO with Co50W40Cu10 stoichiometry was first milled by high energy planetary ball mill and then reduced in a hydrogen reduction system. Crystallite structure of milled mixture and reduced powders was determined by X-ray diffraction. Particles size, morphology and cross-section of reduced samples were studied by SEM, TEM and SEM back scattered electron microscopy. Optimum condition of reduction under hydrogen atmosphere was found at 900°C. Particles have Cu coring structure surrounded with Co3W intermetallic compound. Mean particle size was observed less than 50 nm with six fold hexagon morphology.

The Influence of Fibrilation on the Strength Values and Elongation of the Rejenerated Cellulosic Fibres

In this study, the elongation and strength of viscose, modal, tencel standard and tencel A-100 fibres in alkali solution of NaOH, were measured at both before and after fibrillation with an Instron 4301 test equipment. NUVE ST 402 water bath and NUVE ES 500 cooling type incubator were used during the fibrillation of the fibers. It was found that the breaking loads in all fibrillated fibers were remarkably reduced comparing to the initial conditions. Tencel standard showed the largest reduction with a value of 17,93%, followed by 15,93% in modal, 11,78% in viscose and 10,23% in tencel A-100, respectively. The results also showed that the highest extension ratio after the fibrillation was recorded in modal (21,04%), and then viscose (17,91%) and tencel A- 100 (1,40%) on the contrary, this value decreased by 1,56% in tencel standard. The cross sectional area and surface structure in fibers were also visualised by using scattering electron microscopy (SEM).

A degradable soybean-based biomaterial used effectively as a bone filler in vivo in a rabbit

The ‘gold standard’ for bone filling is currently the bone autograft, but its use is limited by material availability and by the possible risks of infection or other donor site morbidity. Materials proposed so far as bone fillers do not show all the characteristics which are desirable. These are (a) osteoconductivity, (b) controlled biodegradation and (c) ease of adaptation to the implantation site. Recently, a new class of biodegradable material based on soybeans has been presented which shows good mechanical properties and an intrinsic bioactivity on inflammatory and tissue cells in vitro. The authors investigated the morphology in vivo of bone response in repairing a surgical lesion in the presence of granules of a novel soybean-based biomaterial (SB), comparing it with a sham-operated contralateral lesion of critical size (non-healing model); 26 operations were performed in New Zealand White rabbits, with back scattered electron microscopy as the analysis technique of choice. Implantation of SB granules over 8 weeks produced bone repair with features distinct from those obtained by healing in a non-treated defect. New and progressively maturing trabeculae appeared in the animal group where SB granules were implanted, while sham operation produced only a rim of pseudo-cortical bone still featuring a large defect. The trabeculae forming in the presence of SB granules had features typical of reticular bone. These findings suggest that the bone regeneration potential of SB granules and their intrinsic bioactivity, combined with their relatively easy and cost-effective preparation procedures, make them suitable candidates as a bone filler in clinical applications.