X Close
Untitled Document
 
I recently came across this journal and very impressed with the quality of research articles and information available o.

Peter Nirmalraj
Research Scientist
Read more...  
International Conference of Nanoscience and Nanotechnology-ICONN2013
Nano and Water 2011
nano tech 2013 - The12th International Nanotechnology Exhibition & Conference
International Conference on Electron Nanoscopy/ XXXII Annual Meeting of EMSI
International Conference on Biotechnology and Nanotechnology (ICBN 2011)
More events...
Untitled Document
 
   News
New way to prevent cracking in nanoparticle films
Sat, 13 Oct 2012
Making uniform coatings is a common engineering challenge, and, when working at the nanoscale, even the tiniest cracks or defects can be a big problem. New research from University of Pennsylvania engineers has shown a new way of avoiding such cracks when depositing thin films of nanoparticles.
(Also check out our recent Nanowerk Spotlight on this research: "Just say no to cracks").
The research was led by graduate student Jacob Prosser and assistant professor Daeyeon Lee, both of the Department of Chemical and Biomolecular Engineering in Penn’s School of Engineering and Applied Science. Graduate student Teresa Brugarolas and undergraduate student Steven Lee, also of Chemical and Biomolecular Engineering, and professor Adam Nolte of the Rose-Hulman Institute of Technology participated in the research.
Their work was published in the journal Nano Letters ("Avoiding Cracks in Nanoparticle Films").
To generate a nanoparticle film, the desired particles are suspended in a suitable liquid, which is then thinly and evenly spread over the surface through a variety of physical methods. The liquid is then allowed to evaporate, but, as it dries, the film can crack like mud in the sun.
“One method for preventing cracking is modifying the suspension’s chemistry by putting binding additives in there,“ Prosser said. “But that is essentially adding a new material to the film, which may ruin its properties.”
This dilemma is highlighted in the case of electrodes, the contact points in many electrical devices that transfer electricity. High-end devices, like certain types of solar cells, have electrodes composed of nanoparticle films that conduct electrons, but cracks in the films act as insulators. Adding a binder to the films would only compound the problem.
“These binders are usually polymers, which are insulators themselves,” Lee said. “If you use them, you’re not going to get the targeted property, the conductivity, that you want.”
Engineers can prevent cracks with alternative drying methods, but these involve ultra-high temperatures or pressures and thus expensive and complicated equipment. A cheap and efficient method for preventing cracks would be a boon for any number of industrial processes.
The ubiquity of cracking in this context, however, means that researchers know the “critical cracking thickness” for many materials. The breakthrough came when Prosser tried making a film thinner than this threshold, then stacking them together to make a composite of the desired thickness.
“I was thinking about how, in the painting of buildings and homes, multiple coats are used,” Prosser said. “One reason for that is to avoid cracking and peeling. I thought it could work for these films as well, so I gave it a try.”
“This is one of those things where, once you figure it out,” Lee said, “it’s so obvious, but somehow this method has evaded everyone all these years.”
One reason this approach may have remained untried is that it is counterintuitive that it should work at all.
The method the researchers used to make the films is known as “spin-coating.” A precise amount of the nanoparticle suspension — in this case, silica spheres in water — is spread over the target surface. The surface is then rapidly spun, causing centrifugal acceleration to thin the suspension over the surface in a uniform layer. The suspension then dries with continued rotation, causing the water to evaporate and leaving the silica spheres behind in a compacted arrangement.
But to make a second layer over this first, another drop of liquid suspension would need to be placed on the dried nanoparticles, something that would normally wash them away. However, the researchers were surprised when the dried layers remained intact after the process was repeated 13 times; the exact mechanism by which they remained stable is something of a mystery.
“We believe that the nanoparticles are staying on the surface,” Lee said, “because covalent bonds are being formed between them even though we’re not exposing them to high temperatures. The inspiration for that hypothesis came from our colleague Rob Carpick. His recent Nature paper was all about how silica-silica surfaces form bonds at room temperature; we think this will work with other kinds of metal oxides.”
Future research will be necessary to pin down this mechanism and apply it to new types of nanoparticles.

Courtesy: nanowerk.com
   
Other News
Cracks in Electrodes may mean big Boost for Nanoelectronics
Efficient Water Splitting and Solar Energy Storage
The Iron Stepping Stones
Gold Nanoparticles to form `Diamond` Superlattices
Lithium Battery Catalyst found to harm key Soil Microorganism
The Future of Medicine could be found in this tiny Crystal Ball
Silicon-based Metamaterials could bring Photonic Circuits
Using Mathematics to Improve Human Health
Tumor Growth at Bay
Exciting Silicon Nanoparticles
New Electron-Beam Analytical Instrument
A Step towards keeping up with Moore`s Law
Nanowires, Built with Natural gas Heating
Nanosheet
Graphene and Neurons are best Friends
Increasing Oil`s Performance with Crumpled Graphene Balls
One Atom makes a Big Difference
Too-few Proteins Prompt Nanoparticles to Clump
Artificial Muscles, Self-Repairing Materials
`Sawdust`
`Bijels,`
`Be-Leaf`
Novel Nanotechnology Technique
Nano-Coating makes Coaxial Cables Lighter
Tumor-Suppressing Therapies
Graphene Barrier to Control Molecules for making Nanoelectronics
Flexible and Transparent Pressure Sensor
Tiny Gaps Provide a Golden Opportunity
Scientists Demonstrate Basics of Nucleic Acid Computing inside Cells
One-Step Printing Process Provides Coatings for Flexible Touch Screens
New Robotic Gripping Surface for Sensitive Devices
Graphene Oxide `Paper` Changes with Strain
Cooling System for the Processors of the Future
NPs Prove Effective against Antibiotic-Resistant `Superbugs`
Nano-Hybrid Materials Create Magnetic Effect
High-speed transistor
High-Quality Mono-Silicon Crystal Grown at Low Cost for Solar Cells
Tunable Materials clear the way for advanced Optics
A Bubble-Pen to write with Nanoparticles
Unique Phononic Filter
Nanoprobe Development Uncover more DNA Secrets
Flexible Film may lead to Phone-Sized Cancer Detector
Nanodevice, Build Thyself
How Mother-of-Pearl is formed from Nanoparticles
Rapid, Accurate Gene Sequencing
Maxwell`s Demon as a Self-Contained, Information-Powered Refrigerator
Make Lithium-Ion Battery Electrodes that Protect themselves
Shiny Fish Skin Inspires Nanoscale Light Reflectors
Recycling light
Improving Catalysis through Nanoconcentrator Systems
  Untitled Document
 
     
  Untitled Document
 
 
Untitled Document
  Follow us On  Follow us on FacebookFollow us on Twitter  
© 2010 Nano Digest. All Rights Reserved.   - Rify Hosting -