Conductive Atomic Force Microscopic (C-AFM) Studies of Au/MoS2 Nanocomposite Films

2005 ◽  
Author(s):  
Hyun I. Kim ◽  
Jeffrey R. Lince
Keyword(s):  
Morphological Changes ◽  
Real Space ◽  
Metallic Phase ◽  
Electrical Contacts ◽  
Sliding Contact ◽  
Nanocomposite Films ◽  
Material Transfer ◽  
Atomic Force ◽  
Gradual Disappearance ◽  
Slip Rings

Au/MoS2 nanocomposite films with high Au concentrations (75 to 90 at%), recently developed at The Aerospace Corp., have shown properties that are promising for use in sliding electrical contacts, such as slip rings and relays. For such applications, it is critical to maintain low contact resistance while maintaining low friction with controlled wear (i.e. removal and transfer of material). In this report, we present results from conductive atomic force microscopic (c-AFM) investigations of Au/MoS2 nanocomposite structures and their dynamic material transfer phenomena under a sliding contact, which are both important in understanding the friction, wear and conducting mechanisms of the films. We have performed c-AFM to obtain topography, friction and current images simultaneously. Remarkable morphological changes were observed in a series of current images which initially showed distinct nanoscale metallic (Au) and semiconducting (MoS2) phases that were relatively well dispersed, but repeated contact sliding in the same area resulted in gradual disappearance of the metallic phase and reduction of the overall friction. These results reveal that MoS2 is transferred across the surface to provide lubrication while Au particles at or near the surface provide electrical conductivity. The c-AFM results provide real-time and real-space visualization of the lubrication mechanism occurring inside a nanoscale sliding contact.

Development of the UHV-STM

1990 ◽  
Vol 48 (1) ◽  
pp. 322-323
Author(s):  
M. Iwatsuki ◽  
S. Kitamura ◽  
A. Mogami
Keyword(s):  
Surface Science ◽  
Real Space ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Great Promise ◽  
Force Microscopy ◽  
Atomic Force ◽  
Stm Image ◽  
Surface Construction ◽  
Very High

Since Binnig, Rohrer and associates observed real-space topographic images of Si(111)-7×7 and invented the scanning tunneling microscope (STM),1) the STM has been accepted as a powerful surface science instrument.Recently, many application areas for the STM have been opened up, such as atomic force microscopy (AFM), magnetic force microscopy (MFM) and others. So, the STM technology holds a great promise for the future.The great advantages of the STM are its high spatial resolution in the lateral and vertical directions on the atomic scale. However, the STM has difficulty in identifying atomic images in a desired area because it uses piezoelectric (PZT) elements as a scanner.On the other hand, the demand to observe specimens under UHV condition has grown, along with the advent of the STM technology. The requirment of UHV-STM is especially very high in to study of surface construction of semiconductors and superconducting materials on the atomic scale. In order to improve the STM image quality by keeping the specimen and tip surfaces clean, we have built a new UHV-STM (JSTM-4000XV) system which is provided with other surface analysis capability.

Preparation of Cellulose Nanofibrils by High-Pressure Homogenizer and Zein Composite Films

2013 ◽  
Vol 829 ◽  
pp. 534-538 ◽  
Author(s):  
Alireza Shakeri ◽  
Sattar Radmanesh
Keyword(s):  
Atomic Force Microscopy ◽  
High Pressure ◽  
Food Packaging ◽  
Cellulose Nanofibrils ◽  
Composite Films ◽  
Average Diameter ◽  
Nanocomposite Films ◽  
Force Microscopy ◽  
Atomic Force ◽  
High Pressure Homogenizer

Cellulose nanofibrils ( NF ) have several advantages such as biodegradability and safety toward human health. Zein is a biodegradable polymer with potential use in food packaging applications. It appears that polymer nanocomposites are one of the most promising applications of zein films. Cellulose NF were prepared from starting material Microcrystalline cellulose (MCC) by an application of a high-pressure homogenizer at 20,000 psi and treatment consisting of 15 passes. Methods such as atomic force microscopy were used for confirmation of nanoscale size production of cellulose. The average diameter 45 nm were observed. Zeincellulose NF nanocomposite films were prepared by casting ethanol suspensions of Zein with different amounts of cellulose NF in the 0% to 5%wt. The nanocomposites were characterized by using Fourier transform infrared spectroscopy ( FTIR ), Atomic force microscopy ( AFM ) and X-ray diffraction ( XRD ) analysis. From the FTIR spectra the various groups present in the Zein blend were monitored. The homogeneity, morphology and crystallinity of the blends were ascertained from the AFM and XRD data, respectively. The thermal resistant of the zein nanocomposite films improved as the nanocellulose content increased. These obtained materials are transparent, flexible and present significantly better physical properties than the corresponding unfilled Zein films.

scholarly journals Deswelling Induced Morphological Changes in Dual pH and Temperature Responsive Ultra-Low Crosslinked Poly (N-Isopropyl Acrylamide)-Co-Acrylic Acid Microgels

2018 ◽  
Author(s):  
Molla Islam ◽  
Maddie Tumbarello ◽  
Andrew Lyon
Keyword(s):  
Light Scattering ◽  
Acrylic Acid ◽  
Morphological Changes ◽  
Scattering Data ◽  
Ionization State ◽  
Force Microscopy ◽  
Temperature Responsive ◽  
Atomic Force ◽  
Isopropyl Acrylamide ◽  
The Impact

<div>We demonstrated the deswelling induced morphological change in dual pH and Temperature responsive ultra-low crosslinked Poly (N-isopropyl acrylamide)-co-acrylic acid microgels. The responsivity with pH and temperature were studied by light scattering and atomic force microscopy. Light scattering data suggest that at pH 4.5 the microgels undergo multiple transitions associated with collapse of pNIPAm-rich segments and repulsion between the AAc-rich segments. The evolution of punctate structures around the periphery or throughout the whole microgels at pH 4.5 and 6.5 respectively was revealed by AFM, further illustrating the heterogeneous deswelling present in the ionized copolymer microgels.</div><div>The impact of this study and understanding how ionization state of copolymer dictates the overall structural properties of microgels will widen our understanding for their applications in biotechnology</div><div><b><br></b></div>

scholarly journals pH-depended protein shell dis- and reassembly of ferritin nanoparticles revealed by atomic force microscopy

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Lukas Stühn ◽  
Julia Auernhammer ◽  
Christian Dietz
Keyword(s):  
Atomic Force Microscopy ◽  
Ph Value ◽  
Surrounding Medium ◽  
Real Space ◽  
Iron Storage ◽  
Liquid Environment ◽  
Force Microscopy ◽  
Atomic Force ◽  
Dependent Change ◽  
Protein Shell

AbstractFerritin, a protein that is present in the human body for a controlled iron storage and release, consists of a ferrihydrite core and a protein shell. Apoferritin, the empty shell of ferritin, can be modified to carry tailored properties exploitable for targeted and direct drug delivery. This protein shell has the ability to dis- and reassemble depending on the pH value of the liquid environment and can thus be filled with the desired substance. Here we observed the dis- and reassembly process of the protein shell of ferritin and apoferritin in situ and in real space using atomic force microscopy. Ferritin and apoferritin nanoparticles adsorbed on a mica substrate exhibited a change in their size by varying the pH value of the surrounding medium. Lowering the pH value of the solution led to a decrease in size of the nanoparticles whereas a successive increase of the pH value increased the particle size again. The pH dependent change in size could be related to the dis- and reassembling of the protein shell of ferritin and apoferritin. Supplementary imaging by bimodal magnetic force microscopy of ferritin molecules accomplished in air revealed a polygonal shape of the core and a three-fold symmetry of the protein shell providing valuable information about the substructure of the nanoparticles.

scholarly journals Touch-induced seedling morphological changes are determined by ethylene-regulated pectin degradation

2020 ◽  
Vol 6 (48) ◽  
pp. eabc9294
Author(s):  
Qingqing Wu ◽  
Yue Li ◽  
Mohan Lyu ◽  
Yiwen Luo ◽  
Hui Shi ◽  
...  
Keyword(s):  
Cell Wall ◽  
Morphological Changes ◽  
Mechanical Forces ◽  
Ethylene Signaling ◽  
Pectin Degradation ◽  
Force Microscopy ◽  
Mechanical Responses ◽  
Atomic Force ◽  
Wall Stiffness ◽  
Molecular Framework

How mechanical forces regulate plant growth is a fascinating and long-standing question. After germination underground, buried seedlings have to dynamically adjust their growth to respond to mechanical stimulation from soil barriers. Here, we designed a lid touch assay and used atomic force microscopy to investigate the mechanical responses of seedlings during soil emergence. Touching seedlings induced increases in cell wall stiffness and decreases in cell elongation, which were correlated with pectin degradation. We revealed that PGX3, which encodes a polygalacturonase, mediates touch-imposed alterations in the pectin matrix and the mechanics of morphogenesis. Furthermore, we found that ethylene signaling is activated by touch, and the transcription factor EIN3 directly associates with PGX3 promoter and is required for touch-repressed PGX3 expression. By uncovering the link between mechanical forces and cell wall remodeling established via the EIN3-PGX3 module, this work represents a key step in understanding the molecular framework of touch-induced morphological changes.

scholarly journals Insights into dynamic sliding contacts from conductive atomic force microscopy

2020 ◽  
Vol 2 (9) ◽  
pp. 4117-4124
Author(s):  
Nicholas Chan ◽  
Mohammad R. Vazirisereshk ◽  
Ashlie Martini ◽  
Philip Egberts
Keyword(s):  
Electrical Conductivity ◽  
Atomic Force Microscopy ◽  
Sliding Contact ◽  
Current Transport ◽  
Conductive Atomic Force Microscopy ◽  
Sliding Contacts ◽  
Force Microscopy ◽  
Single Asperity ◽  
Atomic Force ◽  
Sliding Dynamics

Measuring the electrical conductivity serves as a proxy for characterizing the nanoscale contact. In this work, the correlation between sliding dynamics and current transport at single asperity sliding contact is investigated.

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