Nanotechnology Now

Our NanoNews Digest Sponsors


Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Polymer structures serve as 'nanoreactors' for nanocrystals with uniform sizes, shapes: Tiny chemistry

Georgia Tech professor Zhiqun Lin examines a gold nanoparticle toluene solution. The work is part of research on using star-shaped block co-polymers to create nanocrystals of uniform size and shape.

Credit: Georgia Tech Photo: Gary Meek
Georgia Tech professor Zhiqun Lin examines a gold nanoparticle toluene solution. The work is part of research on using star-shaped block co-polymers to create nanocrystals of uniform size and shape.

Credit: Georgia Tech Photo: Gary Meek

Abstract:
Using star-shaped block co-polymer structures as tiny reaction vessels, researchers have developed an improved technique for producing nanocrystals with consistent sizes, compositions and architectures - including metallic, ferroelectric, magnetic, semiconductor and luminescent nanocrystals. The technique relies on the length of polymer molecules and the ratio of two solvents to control the size and uniformity of colloidal nanocrystals.

Polymer structures serve as 'nanoreactors' for nanocrystals with uniform sizes, shapes: Tiny chemistry

Atlanta, GA | Posted on June 11th, 2013

The technique could facilitate the use of nanoparticles for optical, electrical, optoelectronic, magnetic, catalysis and other applications in which tight control over size and structure is essential to obtaining desirable properties. The technique produces plain, core-shell and hollow nanoparticles that can be made soluble either in water or in organic solvents.

"We have developed a general strategy for making a large variety of nanoparticles in different size ranges, compositions and architectures," said Zhiqun Lin, an associate professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. "This very robust technique allows us to craft a wide range of nanoparticles that cannot be easily produced with any other approaches."

The technique was described in the June issue of the journal Nature Nanotechnology. The research was supported by the Air Force Office of Scientific Research.

The star-shaped block co-polymer structures consist of a central beta-cyclodextrin core to which multiple "arms" - as many as 21 linear block co-polymers - are covalently bonded. The star-shaped block co-polymers form the unimolecular micelles that serve as a reaction vessel and template for the formation of the nanocrystals.

The inner blocks of unimolecular micelles are poly(acrylic) acid (PAA), which is hydrophilic, which allows metal ions to enter them. Once inside the tiny reaction vessels made of PAA, the ions react with the PAA to form nanocrystals, which range in size from a few nanometers up to a few tens of nanometers. The size of the nanoparticles is determined by the length of the PAA chain.

The block co-polymer structures can be made with hydrophilic inner blocks and hydrophobic outer blocks - amphiphilic block co-polymers, with which the resulting nanoparticles can be dissolved in organic solvents. However, if both inner and outer blocks are hydrophilic - all hydrophilic block co-polymers - the resulting nanoparticles will be water-soluble, making them suitable for biomedical applications.

Lin and collaborators Xinchang Pang, Lei Zhao, Wei Han and Xukai Xin found that they could control the uniformity of the nanoparticles by varying the volume ratio of two solvents - dimethlformamide and benzyl alcohol - in which the nanoparticles are formed. For ferroelectric lead titanate (PbTiO3) nanoparticles, for instance, a 9-to-1 solvent ratio produces the most uniform nanoparticles.

The researchers have also made iron oxide, zinc oxide, titanium oxide, cuprous oxide, cadmium selenide, barium titanate, gold, platinum and silver nanocrystals. The technique could be applicable to nearly all transition or main-group metal ions and organometallic ions, Lin said.

"The crystallinity of the nanoparticles we are able to create is the key to a lot of applications," he added. "We need to make them with good crystalline structures so they will exhibit good physical properties."

Earlier techniques for producing polymeric micelles with linear block co-polymers have been limited by the stability of the structures and by the consistency of the nanocrystals they produce, Lin said. Current fabrication techniques include organic solution-phase synthesis, thermolysis of organometallic precursors, sol-gel processes, hydrothermal reactions and biomimetic or dendrimer templating. These existing techniques often require stringent conditions, are difficult to generalize, include a complex series of steps, and can't withstand changes in the environment around them.

By contrast, nanoparticle production technique developed by the Georgia Tech researchers is general and robust. The nanoparticles remain stable and homogeneous for long periods of time - as much as two years so far - with no precipitation. Such flexibility and stability could allow a range of practical applications, Lin said.

"Our star-like block co-polymers can overcome the thermodynamic instabilities of conventional linear block co-polymers," he said. "The chain length of the inner PAA blocks dictates the size of the nanoparticles, and the uniformity of the nanoparticles is influenced by the solvents used in the system."

The researchers have used a variety of star-like di-block and tri-block co-polymers as nanoreactors. Among them are poly(acrylic acid)-block-polystyrene (PAA-b-PS) and poly(acrylic acid)-blockpoly(ethylene oxide) (PAA-b-PEO) diblock co-polymers, and poly(4-vinylpyridine)-block-poly(tert-butyl acrylate)-block-polystyrene (P4VP-b-PtBA-b-PS), poly(4-vinylpyridine)-block-poly (tert-butyl acrylate)-block-poly(ethylene oxide) (P4VP-b-PtBA-b-PEO), polystyrene-block-poly(acrylic acid)-block-polystyrene (PS-b-PAA-b-PS) and polystyrene-block-poly(acrylic acid)-block-poly(ethylene oxide) (PS-b-PAA-b-PEO) tri-block co-polymers.

For the future, Lin envisions more complex nanocrystals with multifunctional shells and additional shapes, including nanorods and so-called "Janus" nanoparticles that are composed of biphasic geometry of two dissimilar materials.

This research was supported by the Air Force Office of Scientific Research (AFOSR) under awards FA9550-09-1-0388 and FA9550-13-1-0101. The conclusions expressed in this news releases are those of the principal investigator and do not necessarily represent the official views of the AFOSR.

####

For more information, please click here

Contacts:
John Toon

404-894-6986

Copyright © Georgia Institute of Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

CITATION: Xinchang Pang, Lei Zhao, Wei Han, Xukai Xin and Zhiqun Lin, "A general and robust strategy for the synthesis of nearly monodisperse colloidal nanocrystals," (Nature Nanotechnology, 8, 426, 2013):

Related News Press

News and information

Yale researchersí technology turns wasted heat into power June 27th, 2016

FEI Launches Helios G4 DualBeam Series for Materials Science: The Helios G4 DualBeam Series features new capabilities to enable scientists and engineers to answer the most demanding and challenging scientific questions June 27th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Ultrathin, flat lens resolves chirality and color: Multifunctional lens could replace bulky, expensive machines June 25th, 2016

Chemistry

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Quantum calculations broaden the understanding of crystal catalysts: Quantum mechanics and a supercomputer help scientists to identify the position of atoms on the surface of rutile June 22nd, 2016

Govt.-Legislation/Regulation/Funding/Policy

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Ultrathin, flat lens resolves chirality and color: Multifunctional lens could replace bulky, expensive machines June 25th, 2016

Particle zoo in a quantum computer: First experimental quantum simulation of particle physics phenomena June 23rd, 2016

Titan shines light on high-temperature superconductor pathway: Simulation demonstrates how superconductivity arises in cuprates' pseudogap phase June 22nd, 2016

Discoveries

Yale researchersí technology turns wasted heat into power June 27th, 2016

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Announcements

Yale researchersí technology turns wasted heat into power June 27th, 2016

FEI Launches Helios G4 DualBeam Series for Materials Science: The Helios G4 DualBeam Series features new capabilities to enable scientists and engineers to answer the most demanding and challenging scientific questions June 27th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Military

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Ultrathin, flat lens resolves chirality and color: Multifunctional lens could replace bulky, expensive machines June 25th, 2016

Scientists engineer tunable DNA for electronics applications June 21st, 2016

Marrying superconductors, lasers, and Bose-Einstein condensates: Chapman University Institute for Quantum Studies (IQS) member Yutaka Shikano, Ph.D., recently had research published in Scientific Reports June 20th, 2016

Photonics/Optics/Lasers

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Marrying superconductors, lasers, and Bose-Einstein condensates: Chapman University Institute for Quantum Studies (IQS) member Yutaka Shikano, Ph.D., recently had research published in Scientific Reports June 20th, 2016

A new trick for controlling emission direction in microlasers June 20th, 2016

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







Car Brands
Buy website traffic