Cellulose Nanocrystals as Chiral Inducers: Enantioselective Catalysis and Transmission Electron Microscopy 3D Characterization

2015 ◽  
Vol 137 (19) ◽  
pp. 6124-6127 ◽  
Author(s):  
Madhu Kaushik ◽  
Kaustuv Basu ◽  
Charles Benoit ◽  
Ciprian M. Cirtiu ◽  
Hojatollah Vali ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cellulose Nanocrystals ◽  
Enantioselective Catalysis ◽  
Transmission Electron

Linear, non-linear and plastic bending deformation of cellulose nanocrystals

2016 ◽  
Vol 18 (29) ◽  
pp. 19880-19887 ◽  
Author(s):  
Pan Chen ◽  
Yu Ogawa ◽  
Yoshiharu Nishiyama ◽  
Ahmed E. Ismail ◽  
Karim Mazeau
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cellulose Nanocrystals ◽  
Deformation Behavior ◽  
Plastic Bending ◽  
Bending Deformation ◽  
Multi Scale ◽  
Scale Modeling ◽  
Transmission Electron ◽  
Multi Scale Modeling

Bending deformation of cellulose nanocrystal is investigated by using multi-scale modeling and transmission electron microscopy, which highlights importance of shear contribution in the deformation behavior of cellulose.

Sample preparation utilizing sputter coating increases contrast of cellulose nanocrystals in the transmission electron microscope

Microscopy ◽  
2019 ◽  
Author(s):  
Marina R Mulenos ◽  
Bernd Zechmann ◽  
Christie M Sayes
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cellulose Nanocrystals ◽  
Particle Aggregation ◽  
Crystalline Cellulose ◽  
Metal Atoms ◽  
Transmission Electron ◽  
Final Layer ◽  
Sputter Coating ◽  
Cellulose Materials

Abstract Cellulose nanocrystals (CNCs) are prepared for transmission electron microscopy (TEM) using positive or negative stains in an effort to increase the contrast between the specimen and background. When imaging CNCs, conventional stains have been shown to induce particle aggregation and produce artifacts. In this study, we report on methods used to image CNCs. To increase contrast and decrease artifacts and aggregation, sputter coating was used to coat the samples. CNCs were loaded onto copper grids and sputter coated with one of four different metals: iridium, carbon, gold, and titanium. The final layer was deposited at 5 nm to ensure surface homogeneity. The thin layer of conductive metal atoms deposited onto the specimen surface significantly increased contrast and improved image quality. The results presented here demonstrate the advantages of using sputter coating for imaging of highly crystalline cellulose materials with TEM.

scholarly journals Major Factors Influencing the Size Distribution Analysis of Cellulose Nanocrystals Imaged in Transmission Electron Microscopy

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3318
Author(s):  
Hui Qian
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Size Distribution ◽  
Cross Section ◽  
Cellulose Nanocrystals ◽  
Staining Method ◽  
Distribution Analysis ◽  
Size Measurement ◽  
Transmission Electron ◽  
Coffee Ring Effect

Size distributions of cellulose nanocrystals (CNCs), extracted from softwood pulp via strong sulfuric acid hydrolysis, exhibit large variability when analyzed from transmission electron microscopy (TEM) images. In this article, the causes of this variability are studied and discussed. In order to obtain results comparable with those reported, a reference material of CNCs (CNCD-1) was used to evaluate size distribution. CNC TEM specimens were prepared as-stained and dried with a rapid-flushing staining method or hydrated and embedded in vitreous ice with the plunge-freezing method. Several sets of bright-field TEM (BF-TEM), annular dark-field scanning TEM (ADF-STEM) and cryogenic-TEM (cryo-TEM) images were acquired for size distribution analysis to study the contributing factors. The rapid-flushing staining method was found to be the most effective for contrast enhancement of CNCs, not only revealing the helical structure of single CNCs but also resolving the laterally jointed CNCs. During TEM specimen preparation, CNCs were fractionated on TEM grids driven by the coffee-ring effect, as observed from contrast variation of CNCs with a stain-depth gradient. From the edge to the center of the TEM grids, the width of CNCs increases, while the aspect ratio (length to width) decreases. This fractionated dispersion of CNCs suggests that images taken near the center of a droplet would give a larger mean width. In addition to particle fractionation driven by the coffee-ring effect, the arrangement and orientation of CNC particles on the substrate significantly affect the size measurement when CNC aggregation cannot be resolved in images. The coexistence of asymmetric cross-section CNC particles introduces a large variation in size measurement, as TEM images of CNCs are mixed projections of the width and height of particles. As a demonstration of how this contributes to inflated size measurement, twisted CNC particles, rectangular cross-section particles and end-to-end jointed CNCs were revealed in reconstructed three-dimensional (3D) micrographs by electron tomography (ET).

Techniques for Transmission Electron Microscopy of Fiber-Matrix Interfaces in Aluminum Alloy-Boron Composites by Ion Erosio

1971 ◽  
Vol 29 ◽  
pp. 204-205
Author(s):  
G. G. Shaw
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aluminum Alloy ◽  
Electron Beam ◽  
Pure Aluminum ◽  
Ion Milling ◽  
Transmission Electron ◽  
Fiber Matrix ◽  
Ion Erosion ◽  
Row Of Fibers

The morphology and composition of the fiber-matrix interface can best be studied by transmission electron microscopy and electron diffraction. For some composites satisfactory samples can be prepared by electropolishing. For others such as aluminum alloy-boron composites ion erosion is necessary.When one wishes to examine a specimen with the electron beam perpendicular to the fiber, preparation is as follows: A 1/8 in. disk is cut from the sample with a cylindrical tool by spark machining. Thin slices, 5 mils thick, containing one row of fibers, are then, spark-machined from the disk. After spark machining, the slice is carefully polished with diamond paste until the row of fibers is exposed on each side, as shown in Figure 1.In the case where examination is desired with the electron beam parallel to the fiber, preparation is as follows: Experimental composites are usually 50 mils or less in thickness so an auxiliary holder is necessary during ion milling and for easy transfer to the electron microscope. This holder is pure aluminum sheet, 3 mils thick.

Direct Observation of Heat Exchanger Deposits by Cross Sectioning

1967 ◽  
Vol 25 ◽  
pp. 364-365
Author(s):  
R. W. Anderson ◽  
D. L. Senecal
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Heat Exchanger ◽  
Direct Observation ◽  
Cross Sections ◽  
Preparation Method ◽  
Specimen Preparation ◽  
Flowing Water ◽  
Transmission Electron ◽  
Deposit Layer

A problem was presented to observe the packing densities of deposits of sub-micron corrosion product particles. The deposits were 5-100 mils thick and had formed on the inside surfaces of 3/8 inch diameter Zircaloy-2 heat exchanger tubes. The particles were iron oxides deposited from flowing water and consequently were only weakly bonded. Particular care was required during handling to preserve the original formations of the deposits. The specimen preparation method described below allowed direct observation of cross sections of the deposit layers by transmission electron microscopy.The specimens were short sections of the tubes (about 3 inches long) that were carefully cut from the systems. The insides of the tube sections were first coated with a thin layer of a fluid epoxy resin by dipping. This coating served to impregnate the deposit layer as well as to protect the layer if subsequent handling were required.

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