Featured Research

from universities, journals, and other organizations

Nano world: Where towers construct themselves

Date:
June 2, 2014
Source:
University of Vienna
Summary:
A tower which builds itself is absurd -- and however, in the nano world self-assembly is reality. Physicists have investigated how to control the ordering of such self-assembling structures at the nano-scale. Physicists investigated how they can control the ordering of such self-assembling structures and found out how to switch the assembly process on and off.

Inverse patchy colloids (IPCs) with two positively charged regions (in yellow) and one negatively charged equatorial belt (in grey) are confined in the vicinity of a uniformly charged substrate (in yellow).
Credit: Copyright: Emanuela Bianchi

Imagine a tower builds itself into the desired structure only by choosing the appropriate bricks. Absurd -- and however, in the nano world this is reality: There an unordered crowd of components can initiate the formation of an ordered structure -- a process known as self-assembly. The physicists Christos Likos (University of Vienna), Emanuela Bianchi and Gerhard Kahl (both Vienna University of Technology) investigate how they can control the ordering of such self-assembling structures and found out how to switch the assembly process on and off.

Materials with specific properties at the nano- and micro-scale level are heavily sought after due to the broad spectrum of applications in electronics, photovoltaics and biomimetic material synthesis. For many of these applications, mesoscopic crystalline structures are often needed and hence scientists have to deal with the challenge of developing reliable, efficient and cheap methods to produce target structures with specific symmetries and physical properties. Nowadays, rather than relying on externally-controlled tools, most of the fabrication methods are based on the self-assembly of carefully chosen/synthesized base units. The macroscopic counterpart would correspond to building a tower or a bridge just by choosing the appropriate bricks and letting them self-organize into the desired structure.

In the vast realm of functional nano- and micro-scale materials, the realization of mono- and bi-layer assemblies on surfaces is of paramount relevance. Low-dimensional systems with well-defined features have indeed applications as e.g. antireflection coatings, biosensors, data-storage, optical and photovoltaic devices, or catalysts. The properties of these materials strongly depend on a delicate balance between the properties of the assembling units and those of the underlying surface.

In our contribution we focused on nano-units with a complicated surface pattern, consisting of regions with different surface charge. The investigated units are mostly negatively charged with the exception of the positively charged polar regions on the top and at the bottom of the particles. Similar non-homogeneously charged units appear either in biosystems, e.g. viral capsids and proteins, or in experimentally synthesized systems, e.g. virus-like nano-particles, spotted vesicles and nano-cubes covered with specific metals.

In the up-coming paper we focused on the self-assembly of the described heterogeneously charged particles in the vicinity of a homogeneously charged substrate. Our computer simulations showed how complex structures at the nano-scale level can spontaneously emerge and how it is possible to reliably control the ordering of the particles into specific, quasi two-dimensional aggregates. Depending on different parameters, such as the particle/wall charge and the extension of the charged regions on the particle surface, our units can form surface layers with different densities (and possibly different responses to external stimuli): sometimes particles assemble into close-packed, hexagonally ordered crystalline aggregates, sometimes they form open, square-like layers, sometimes they do not assemble at all. Our work was able to investigate the variety of the self-assembled structures offered by the chosen bricks and to characterise the specific collective behaviors occurring on tuning the relevant parameters of these systems. Moreover and most importantly, we showed that upon subtle changes of either the pH of the solution or of the electrical charge of the substrate, it is possible to reversibly switch the assembly process on and off as well as to induce a transformation from a one specific spatial/orientational arrangement to another.


Story Source:

The above story is based on materials provided by University of Vienna. Note: Materials may be edited for content and length.


Journal Reference:

  1. Emanuela Bianchi, Christos N. Likos, Gerhard Kahl. Tunable Assembly of Heterogeneously Charged Colloids. Nano Letters, 2014; 140527155338002 DOI: 10.1021/nl500934v

Cite This Page:

University of Vienna. "Nano world: Where towers construct themselves." ScienceDaily. ScienceDaily, 2 June 2014. <www.sciencedaily.com/releases/2014/06/140602132226.htm>.
University of Vienna. (2014, June 2). Nano world: Where towers construct themselves. ScienceDaily. Retrieved September 17, 2014 from www.sciencedaily.com/releases/2014/06/140602132226.htm
University of Vienna. "Nano world: Where towers construct themselves." ScienceDaily. www.sciencedaily.com/releases/2014/06/140602132226.htm (accessed September 17, 2014).

Share This



More Matter & Energy News

Wednesday, September 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Space Race Pits Bezos Vs Musk

Space Race Pits Bezos Vs Musk

Reuters - Business Video Online (Sep. 16, 2014) Amazon CEO Jeff Bezos' startup will team up with Boeing and Lockheed to develop rocket engines as Elon Musk races to have his rockets certified. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
MIT's Robot Cheetah Unleashed — Can Now Run, Jump Freely

MIT's Robot Cheetah Unleashed — Can Now Run, Jump Freely

Newsy (Sep. 16, 2014) MIT developed a robot modeled after a cheetah. It can run up to speeds of 10 mph, though researchers estimate it will eventually reach 30 mph. Video provided by Newsy
Powered by NewsLook.com
Manufacturer Prints 3-D Car In Record Time

Manufacturer Prints 3-D Car In Record Time

Newsy (Sep. 15, 2014) Automobile manufacturer Local Motors created a drivable electric car using a 3-D printer. Printing the body only took 44 hours. Video provided by Newsy
Powered by NewsLook.com
Refurbished New York Subway Tunnel Unveiled After Sandy Damage

Refurbished New York Subway Tunnel Unveiled After Sandy Damage

Reuters - US Online Video (Sep. 15, 2014) New York officials unveil subway tunnels that were refurbished after Superstorm Sandy. Nathan Frandino reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins