Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Nanoscale Cubes and Spheres

Abstract:
Porous nano-objects with defined sizes and structures are particularly interesting, for example, as capsules for enzymes, a means of transport for pharmaceutical agents, or building blocks for larger nanostructures. The production of such tiny, three-dimensional objects in a targeted and controlled manner-and as simply and efficiently as possible-remains a challenge for scientists. At the University of Minnesota, a team led by Andreas Stein has now developed an interesting new process for the production of nanoscopic cubes and spheres of silicon dioxide. The researchers reported their trick in Angewandte Chemie: Instead of building their particles from smaller units, they used the controlled disassembly of larger, lattice-like structures.

Nanoscale Cubes and Spheres

Germany | Posted on January 4th, 2007

Most conventional methods for the production of porous silicon dioxide nanoparticles suffer from the fact that the growing particles tend to aggregate (clump together), making it difficult to achieve a uniform size. The shape of the particles can hardly be influenced at all. Stein and his team chose a backward approach, first building up a lattice structure of silicon dioxide and then disassembling it to get the shape they wanted. The "moulds" used for the lattice were tiny spheres of a plastic called polymethylmethacrylate (PMMA), which assemble themselves through "closest packing of spheres" into a colloidal crystal. Between the spheres in this structure, there are little, nearly tetrahedral and nearly octahedral spaces. The researchers filled these cavities with a solution containing an organosilicon compound, oxalic acid, and a surfactant. This mixture hardens into a solid gel. The plastic spheres and surfactant are then burned off by heating. The surfactant leaves behind tiny pores, and the gelled organosilicon compound slowly converts to a solid silicon oxide. What remains initially is a silicate lattice that is the negative of the packed spheres: tiny tetrahedra and octahedra attached to each other by delicate bridges. As the conversion to silicon dioxide continues, the structure shrinks until it breaks at the weakest points-the bridges. The fragments formed by this process are shaped like octahedra or smaller tetrahedra. These continue to contract until the octahedra become nearly cubic and the tetrahedra become nearly spherical, making highly uniform structures with worm-like pores.

By varying the colloidal crystals used as the mould, the size and shape of the resulting particles can be controlled. Through vapor deposition or polymer grafting, other compounds can be added to the structure. Subsequent etching away of the silicon oxide allows this new technique to be used as a starting point for nanostructures made of other materials.

####

About Angewandte Chemie International Edition
Author: Andreas Stein, University of Minnesota, Minneapolis (USA), http://www.chem.umn.edu/groups/stein/

Title: Shaping Mesoporous Silica Nanoparticles by Disassembly of Hierarchically Porous Structures

For more information, please click here

Contacts:
Editorial David
Julia Lampam

Copyright © Angewandte Chemie International Edition

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 News Press

Discoveries

Iranian Researchers Present New Model to Strengthen Superconductivity at Higher Temperatures April 19th, 2014

Iranian Researchers Produce New Anti-Cancer Drug from Turmeric April 19th, 2014

'Exotic' material is like a switch when super thin April 18th, 2014

Innovative strategy to facilitate organ repair April 18th, 2014

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







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE