scholarly journals Self-Assembly of Diphenylalanine-Based Nanostructures in Water and Electrolyte Solutions

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Sergio M. Acuña ◽  
María C. Veloso ◽  
Pedro G. Toledo
Keyword(s):  
Electron Microscopy ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Hydrophobic Interactions ◽  
Electrolyte Solutions ◽  
Salt Solutions ◽  
Shape Information ◽  
Transmission Electron ◽  
Structure Breaking ◽  
Scanning Electron

Diphenylalanine (FF) is a peptide that can form different nanostructures; this makes it particularly attractive for both biological and technological applications. However, any application using this type of nanostructures requires controlling their size and shape. Information is provided about the various structures formed through the peptide FF self-assembly in different salt solutions (NaCl, CaCl2, and AlCl3), concentrations (50 mM, 100 mM, and 200 mM), and pH (3 to 10). Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy were used to characterize the nanotubes. Results show that FF nanotube formation through self-assembly is a delicate balance between electrostatic, hydrogen bonding, and hydrophobic interactions; any imbalance in these can impede nanotube formation. Our results demonstrate that salts, such as NaCl and CaCl2, along with the studied concentrations promote the formation of very long nanotube agglomerates. This would be due to a combined screening effect and the fact that cations are structure-forming and promote hydrophobic interactions; therefore, nanotube agglomeration occurs and also benefits electrostatic interactions, hydrogen bonds, and longer nanotubes. The presence of AlCl3 produces an imbalance in the abovementioned interactions because of excess Cl-, a structure-breaking anion that impedes the nanostructure formation.

Click Synthesis of Shape-Persistent Azodendrimers and their Orthogonal Self-Assembly to Nanofibres

2018 ◽  
Vol 71 (6) ◽  
pp. 463 ◽  
Author(s):  
Tamer El Malah ◽  
Hany F. Nour
Keyword(s):  
Electron Microscopy ◽  
Mass Spectrometry ◽  
Self Assembly ◽  
Molecular Structures ◽  
Side Chain ◽  
Spectroscopic Techniques ◽  
Molecular Weights ◽  
Transmission Electron ◽  
Click Synthesis ◽  
Scanning Electron

The copper(i)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction has been efficiently utilized to synthesize a series of dendrons with amino functionalities. The aminodendrons successfully underwent azodimerization to furnish a series of pyridyl- and phenyl-based azodendrimers with peripheral alkyl or ether side chain substituents. The molecular structures of the azodendrimers were fully assigned using different spectroscopic techniques, such as 1H NMR and 13C NMR, and the molecular weights were determined using MALDI-TOF mass spectrometry. The molecular self-assembly of the azodendrimers was investigated by scanning electron microscopy and transmission electron microscopy, which revealed the formation of highly ordered and uniform self-assembled nanofibres.

scholarly journals Nanohydrogels Based on Self-Assembly of Cationic Pullulan and Anionic Dextran Derivatives for Efficient Delivery of Piroxicam

Pharmaceutics ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 622 ◽  
Author(s):  
Dorota Lachowicz ◽  
Przemyslaw Mielczarek ◽  
Roma Wirecka ◽  
Katarzyna Berent ◽  
Anna Karewicz ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Dextran Sulfate ◽  
Force Microscopy ◽  
Grafting Reaction ◽  
Atomic Force ◽  
Transmission Electron ◽  
Efficient Delivery ◽  
Model Drug

A cationic derivative of pullulan was obtained by grafting reaction and used together with dextran sulfate to form polysaccharide-based nanohydrogel cross-linked via electrostatic interactions between polyions. Due to the polycation-polyanion interactions nanohydrogel particles were formed instantly and spontaneously in water. The nanoparticles were colloidally stable and their size and surface charge could be controlled by the polycation/polyanion ratio. The morphology of the obtained particles was visualized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The resulting structures were spherical, with hydrodynamic diameters in the range of 100–150 nm. The binding constant (Ka) of a model drug, piroxicam, to the cationic pullulan (C-PUL) was determined by spectrophotometric measurements. The value of Ka was calculated according to the Benesi—Hildebrand equation to be (3.6 ± 0.2) × 103 M−1. After binding to cationic pullulan, piroxicam was effectively entrapped inside the nanohydrogel particles and released in a controlled way. The obtained system was efficiently taken up by cells and was shown to be biocompatible.

Fabrication of Nanosheets and Micro-Spheres from the Self-Assembly and Polymerization of N-Octadecyltrichlorosilane

2011 ◽  
Vol 311-313 ◽  
pp. 485-488 ◽  
Author(s):  
Shuai Zhang ◽  
Qing Ping Ke ◽  
Lei Zhang ◽  
Tian Di Tang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Self Assembly ◽  
Micelle Formation ◽  
The Self ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Hydrolysis Process ◽  
Scanning Electron

Formation of layered nanosheets and micro-spheres from a simple self-assembly and polycondensation of n-octadecylsilane (PODS) in water and toluene is demonstrated, respectively. The structure of the micro-spheres was characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). According to the TEM images, it was firstly confirmed that the micro-spheres consist of stacks of bilayered polymerized n-octadecylsilane with head-to-head arrangements. The co-effects of water and solvent were proposed to control the octadecyltrichlsilane hydrolysis process and eventually the morphology of the micro-spheres. A micelle formation mechanism for the formation of the PODS micro-spheres under the co-effects of water and solvent were firstly proposed.

Self-Assembly of Aligned Multi-Walled Carbon Nanotubes in Polypropylene-Coated Multi-Walled Carbon Nanotubes Composites

2013 ◽  
Vol 669 ◽  
pp. 55-62 ◽  
Author(s):  
Yi Na Xiong ◽  
Xiao Hua Chen ◽  
Qun Huang ◽  
Long Shan Xu
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Scanning Electron Microscopy ◽  
Self Assembly ◽  
Butyl Methacrylate ◽  
Transmission Electron ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
Scanning Electron

Polypropylene (PP)-coated multi-walled carbon nanotubes (MWNTs) composite with MWNTs exceptional alignment dispersed and improved mechanical properties was prepared with maleic anhydride (MAH) as a compatibilizer and poly (butyl methacrylate) (PBMA) as a binding. Scanning electron microscopy (SEM) results showed that MWNTs within composite were aligned without aggregation and the oriented MWNTs were connected by matrix. High-resolution transmission electron microscopy (HRTEM) results demonstrated that the nanotubes were densely coated with a PP layer. Infrared spectroscopy (IR) results revealed that there was covalently linkage of MWNTs with PP via MAH. The interactions between MWNTs-PP and MWNTs-PBMA induced orientation of MWNTs. The improved mechanical properties of PP - coated MWNTs composite was also shown.

Spontaneous Self-Assembly of Thiol-Capped CdTe Nanoparticles Into Nanowires Under Dark Conditions

2015 ◽  
Vol 15 (10) ◽  
pp. 8275-8278
Author(s):  
Yea Eun Lee ◽  
Jeong Won Kang ◽  
Ki-Sub Kim
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Self Assembly ◽  
Driving Forces ◽  
Evolutionary Process ◽  
Cdte Nanoparticles ◽  
Transmission Electron ◽  
Synthetic Procedure ◽  
Dark Conditions ◽  
Scanning Electron

Thiol-capped cadmium telluride (CdTe) nanoparticles (NPs) self-assembled into nanowires (NWs) under dark conditions, and the evolutionary process was investigated. Thiolglycolic acid (TGA) was selected as one of the stabilizers and a TGA-to-Cd ion ratio of 1.3 rather than the traditional 2.4 ratio was used. The reduced amount of the stabilizer and the oxidation of tellurium ions on CdTe NP surface under dark conditions resulted in reorganization from individual NPs into NWs consisting of multi-layers of individual NPs. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were performed to characterize the synthesized nanostructures. The NWs produced were straight and long, with lengths ranging from 500 nm to 10 μm. Photoluminescence (PL) showed that the nanostructure wavelengths were slightly blue-shifted from 546 to 539 nm. Both control of the amount of stabilizer and oxidation of Te ions acted as driving forces to form NWs. Thus, small modifications in synthesis yielded a major difference in the final nanomaterial structure. The suggested synthetic procedure provides a viable pathway for the fabrication of nanomaterials.

scholarly journals Growth of Nacre Biocrystals by Self-Assembly of Aragonite Nanoparticles with Novel Subhedral Morphology

Crystals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 3
Author(s):  
Ruohe Gao ◽  
Rize Wang ◽  
Xin Feng ◽  
Gangsheng Zhang
Keyword(s):  
Electron Microscopy ◽  
Self Assembly ◽  
The Self ◽  
Growth Stages ◽  
Research Model ◽  
Biomimetic Materials ◽  
Transmission Electron ◽  
Nanoparticle Morphology ◽  
Different Growth Stages ◽  
Scanning Electron

Nacre has long served as a research model in the field of biomineralization and biomimetic materials. It is widely accepted that its basic components, aragonite biocrystals, namely, tablets, are formed by the nanoparticle-attachment pathway. However, the details of the nanoparticle morphology and arrangement in the tablets are still a matter of debate. Here, using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), we observed the nanostructure of the growing tablets at different growth stages and found that: (1) the first detectable tablet looked like a rod; (2) tablets consisted of subhedral nanoparticles (i.e., partly bounded by crystal facets and partly by irregular non-crystal facets) that were made of aragonite single crystals with a width of 160–180 nm; and (3) these nanoparticles were ordered in orientation but disordered in position, resulting in unique subhedral and jigsaw-like patterns from the top and side views, respectively. In short, we directly observed the growth of nacre biocrystals by the self-assembly of aragonite nanoparticles with a novel subhedral morphology.

Ultrastructural Analysis of the Salivary Glands of Gromphadorhina Portentosa (Schaum)

1977 ◽  
Vol 35 ◽  
pp. 638-639
Author(s):  
P.J. Dailey
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Salivary Glands ◽  
Secretory Vesicles ◽  
The Past ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Gromphadorhina Portentosa ◽  
Scanning Electron ◽  
Topographical Relief

The structure of insect salivary glands has been extensively investigated during the past decade; however, none have attempted scanning electron microscopy (SEM) in ultrastructural examinations of these secretory organs. This study correlates fine structure by means of SEM cryofractography with that of thin-sectioned epoxy embedded material observed by means of transmission electron microscopy (TEM).Salivary glands of Gromphadorhina portentosa were excised and immediately submerged in cold (4°C) paraformaldehyde-glutaraldehyde fixative1 for 2 hr, washed and post-fixed in 1 per cent 0s04 in phosphosphate buffer (4°C for 2 hr). After ethanolic dehydration half of the samples were embedded in Epon 812 for TEM and half cryofractured and subsequently critical point dried for SEM. Dried specimens were mounted on aluminum stubs and coated with approximately 150 Å of gold in a cold sputtering apparatus.Figure 1 shows a cryofractured plane through a salivary acinus revealing topographical relief of secretory vesicles.

Two- or three-way observations of the identical cell elements within the same sections by LM, TEM and/or SEM

1978 ◽  
Vol 36 (2) ◽  
pp. 82-83 ◽  
Author(s):  
Nakazo Watari ◽  
Yasuaki Hotta ◽  
Yoshio Mabuchi
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Light Microscopy ◽  
Thin Sections ◽  
Transmission Electron ◽  
Identical Cell ◽  
Electron Microscopes ◽  
Scanning Electron

It is very useful if we can observe the identical cell elements within the same sections by light microscopy (LM), transmission electron microscopy (TEM) and/or scanning electron microscopy (SEM) sequentially, because, the cell fine structure can not be indicated by LM, while the color is; on the other hand, the cell fine structure can be very easily observed by EM, although its color properties may not. However, there is one problem in that LM requires thick sections of over 1 μm, while EM needs very thin sections of under 100 nm. Recently, we have developed a new method to observe the same cell elements within the same plastic sections using both light and transmission (conventional or high-voltage) electron microscopes.In this paper, we have developed two new observation methods for the identical cell elements within the same sections, both plastic-embedded and paraffin-embedded, using light microscopy, transmission electron microscopy and/or scanning electron microscopy (Fig. 1).

Scanning and Transmission Microscopy of Nematocyst Batteries in Epitheliomuscular Cells of Hydra

1971 ◽  
Vol 29 ◽  
pp. 410-411 ◽  
Author(s):  
Jane A. Westfall ◽  
S. Yamataka ◽  
Paul D. Enos
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Osmium Tetroxide ◽  
External Surface ◽  
Three Dimensional ◽  
Surface Structures ◽  
Transmission Microscopy ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Scanning Electron

Scanning electron microscopy (SEM) provides three dimensional details of external surface structures and supplements ultrastructural information provided by transmission electron microscopy (TEM). Animals composed of watery jellylike tissues such as hydras and other coelenterates have not been considered suitable for SEM studies because of the difficulty in preserving such organisms in a normal state. This study demonstrates 1) the successful use of SEM on such tissue, and 2) the unique arrangement of batteries of nematocysts within large epitheliomuscular cells on tentacles of Hydra littoralis.Whole specimens of Hydra were prepared for SEM (Figs. 1 and 2) by the fix, freeze-dry, coat technique of Small and Màrszalek. The specimens were fixed in osmium tetroxide and mercuric chloride, freeze-dried in vacuo on a prechilled 1 Kg brass block, and coated with gold-palladium. Tissues for TEM (Figs. 3 and 4) were fixed in glutaraldehyde followed by osmium tetroxide. Scanning micrographs were taken on a Cambridge Stereoscan Mark II A microscope at 10 KV and transmission micrographs were taken on an RCA EMU 3G microscope (Fig. 3) or on a Hitachi HU 11B microscope (Fig. 4).

Application of Scanning Electron Microscopy to Medical Research

1969 ◽  
Vol 27 ◽  
pp. 12-13
Author(s):  
J. D. Hutchison
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Medical Research ◽  
Prosthetic Heart Valve ◽  
School Of Medicine ◽  
Transmission Electron ◽  
Definition Of ◽  
Mechanism Of Failure ◽  
The Brain ◽  
Scanning Electron

When the transmission electron microscope was commercially introduced a few years ago, it was heralded as one of the most significant aids to medical research of the century. It continues to occupy that niche; however, the scanning electron microscope is gaining rapidly in relative importance as it fills the gap between conventional optical microscopy and transmission electron microscopy.IBM Boulder is conducting three major programs in cooperation with the Colorado School of Medicine. These are the study of the mechanism of failure of the prosthetic heart valve, the study of the ultrastructure of lung tissue, and the definition of the function of the cilia of the ventricular ependyma of the brain.

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