Summary: Preparation and morphology of high density polyethylene (HDPE)/ polyamide 6 (PA 6)/modified clay nanocomposites were studied. The ability of PA 6 in dispersing clays was used to prepare modified delaminated clays, which were then mixed with HDPE. Mixing was performed using melt processing in a torque rheometer equipped with roller rotors. After etching the materials with boiling toluene and formic acid at room temperature, the morphology was examined by SEM analyses, showing that the PA 6 formed the continuous phase and HDPE the dispersed phase. X-ray diffraction patterns show that the (001) peak of the clay is dramatically decreased and shifted to lower angles, indicating that intercalated/exfoliated nanocomposites are obtained. TEM analyses confirmed the typical structure of exfoliated nanocomposites. A scheme for the mechanism of exfoliation and/or intercalation of these HDPE /PA 6/ /organoclay nanocomposites is proposed. 相似文献
DNA nanotechnology utilizes DNA double strands as building units for self-assembly of DNA nanostructures.The specific base-pairing interaction between DNA molecules is the basis of these assemblies.After decades of development,this technology has been able to construct complex and programmable structures.With the increase in delicate nature and complexity of the synthesized nanostructures,a characterization technology that can observe these structures in three dimensions has become necessary,and developing such a technology is considerably challenging.DNA assemblies have been studied using different characterization methods including atomic force microscopy(AFM),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).However,the three-dimensional(3D)DNA assemblies always collapse locally due to the dehydration during the drying process.Cryogenic electron microscopy(cryo-EM)can overcome the challenge by maintaining three-dimensional morphologies of the cryogenic samples and reconstruct the 3D models from cryogenic samples accordingly by collecting thousands of two-dimensional(2D)projection images,which can restore their original morphologies in solution.Here,we have reviewed several typical cases of 3D DNA-assemblies and highlighted the applications of cryo-EM in characterization of these assemblies.By comparing with some other characterization methods,we have shown how cryo-EM promoted the development of structural characterization in the field of DNA nanotechnology. 相似文献
The texture evolution during deformation of high purity fcc single crystals with initial (112) [11
] orientation has been characterised in detail by transmission (TEM) and scanning (SEM–FEG) electron microscopes. The channel-die
deformed samples up to reduction of about 1–1.5, first developing strongly anisotropic layers of elongated cells or twin-matrix
plates and then compact clusters of SB. Substantial progress in understanding the mechanism of the SB formation was possible
thanks to systematic local orientation measurements (orientation mapping) using SEM and TEM. These two techniques of local
orientation measurements have been compared with respect to their applicability for the study of shear banding phenomenon
and for characterization of the specific nanostructure of SB in metals with fcc lattice. It was shown that well-developed
SB exhibit large orientation spreads up to 35–40° with respect to the adjacent areas outside the band. Most of these misorientations
occur by rotations about the TD‖〈110〉 axis with significant further rotations about 〈112〉 poles. This ultimately leads to
the formation of the texture components whose occurrence cannot be explained by models homogeneous deformation. 相似文献
We describe epitope mapping data using multiple covalent labeling footprinting-mass spectrometry (MS) techniques coupled with negative stain transmission electron microscopy (TEM) data to analyze the antibody–antigen interactions in a sandwich enzyme-linked immunosorbant assay (ELISA). Our hydroxyl radical footprinting-MS data using fast photochemical oxidation of proteins (FPOP) indicates suppression of labeling across the antigen upon binding either of the monoclonal antibodies (mAbs) utilized in the ELISA. Combining these data with Western blot analysis enabled the identification of the putative epitopes that appeared to span regions containing N-linked glycans. An additional structural mapping technique, carboxyl group footprinting-mass spectrometry using glycine ethyl ester (GEE) labeling, was used to confirm the epitopes. Deglycosylation of the antigen resulted in loss of potency in the ELISA, supporting the FPOP and GEE labeling data by indicating N-linked glycans are necessary for antigen binding. Finally, mapping of the epitopes onto the antigen crystal structure revealed an approximate 90° relative spatial orientation, optimal for a noncompetitive binding ELISA. TEM data shows both linear and diamond antibody–antigen complexes with a similar binding orientation as predicted from the two footprinting-MS techniques. This study is the first of its kind to utilize multiple bottom-up footprinting-MS techniques and TEM visualization to characterize the monoclonal antibody-antigen binding interactions of critical reagents used in a quality control (QC) lot-release ELISA.
The present paper describes a simple route to prepare organic-inorganic colloids with a core-corona structure. Colloids are obtained by complexation of multivalent metal cations by anionic-neutral double hydrophilic block copolymers leading to hybrid polyion complex micelles. The hybrid colloids can then be mineralized in suspension by performing hydrolysis of metal cations within the micelles. The present study focuses on the structural characterization of the colloidal complexes and of the mineralized nanoparticles using a combination of transmission electron microscopy (TEM) techniques including conventional bright-field imaging (with and without negative staining) and cryo-TEM observations. It is shown that the different types of TEM observations are complementary and necessary to get a complete picture of the core-corona colloids. 相似文献
Well‐developed crystals of [Pt(NH3)4](HCO3)2 are employed as template for the synthesis of silicon dioxide nanotubes (SiO2‐NTs). Silicon dioxide, which is produced by a sol‐gel reaction, coats the surface of these crystals and builds up the nanotube walls. In the final step, the Pt‐salt fibers are thermally decomposed and auto‐reduced to metallic Pt nanoparticles. Scanning and transmission electron microscopy (SEM and TEM) investigations of the product confirm the formation of silicon dioxide nanotubes in high yield. The tube walls consist of amorphous silicon dioxide. The tube length generally is 0.5 — 3 μm, while the thickness varies in two distinct ranges: thick tubes have a diameter of 100 — 500 nm and thin ones of approximately 50 nm. Most of the NTs are filled with Pt particles, but others, typically the larger ones with open tube ends, obviously are empty. Presumably, open ends cause the observed Pt loss. In closed SiO2‐NTs, Pt forms as ca. 10 nm large particles in the tube core and as 1 — 2 nm large particles inside the tube walls. 相似文献
