Materials made from nanoparticles hold promise for myriad applications, from improved solar energy production to perfect touch screens. The challenge in creating these wonder-materials is organizing the nanoparticles into orderly arrangements.
Nanoparticles of magnetite, the most abundant magnetic material on earth, are found in living organisms from bacteria to birds. Nanocrystals of magnetite self-assemble into fine compass needles in the organism that help it to navigate.
Collaborating with nanochemists led by Rafal Klajn at the Weizmann Institute of Science in Israel, who found that magnetite nanocubes can self-assemble into helical superstructures under certain conditions, University of Illinois at Chicago theoretical chemist Petr Kral and his students simulated the phenomenon and explained the conditions under which it can occur. The joint study is online in Science Express in advance of print in the Sept. 5 issue of Science.
The Weizmann researchers dissolved the nanocrystals and exposed the solution to an external magnetic field. As the solution evaporated, helical chains of nanoparticles formed. Surprisingly, the spiral helices were chiral -- that is, either left- or right-handed -- despite the fact that the nanoparticles themselves are not chiral. Densely packed assemblies of helices tended to adopt the same handedness.
Kral's UIC team modeled the self-assembly to determine how helices formed in their collaborators' experiments -- and why the helices had chirality.
They found that the self-assembly into chiral helices is the result of the competing forces acting on them — Zeeman force from the external magnetic field, dipole-dipole magnetic force, magneto-anisotropic directional force, weakly attractive van der Waals forces, and others. The chemistry of the nanoparticle ligands, the solvent, and temperature may also play a role.
In the presence of an external magnetic field, the superparamagnetic nanocubes — which are randomly magnetic and can flip with temperature changes — became tiny magnets with different symmetries of the competing forces acting between them. As a result, when two cubes are face-to-face, they tend to tilt with respect to each other, forming a small angle to the right or left — the seed of a chiral helix, as more nanocubes line up with the first two.
Kral's analysis used a Monte Carlo computer algorithm, which relies on repeated random sampling, running simulations many times over.
"We had to write a new, efficient Monte Carlo computer code describing all the necessary terms, all the values, and then explain how the highly unusual behavior that Klajn observed – the helices' self-assembly – happens," Kral said.
Gurvinder Singh of the Weizmann Institute is first author of the paper. Elijah Gelman of the Weizmann Institute, and Henry Chan, Artem Baskin and Nikita Repnin of UIC are co-authors on the study.
The work was supported by the Israel Science Foundation grant 1463/11, the G. M. J. Schmidt-Minerva Center for Supramolecular Architectures, the Minerva Foundation with funding from the Federal German Ministry for Education and Research, National Science Foundation Division of Materials Research grant 1309765 and the American Chemical Society Petroleum Research Fund grant 53062-ND6.
Jeanne Galatzer-Levy | Eurek Alert!
Nanobionics Supercharge Photosynthesis
22.05.2015 | Department of Energy, Office of Science
Mesoporous Particles for the Development of Drug Delivery System Safe to Human Bodies
22.05.2015 | National Institute for Materials Science
Physicists have developed an innovative method that could enable the efficient use of nanocomponents in electronic circuits. To achieve this, they have developed a layout in which a nanocomponent is connected to two electrical conductors, which uncouple the electrical signal in a highly efficient manner. The scientists at the Department of Physics and the Swiss Nanoscience Institute at the University of Basel have published their results in the scientific journal “Nature Communications” together with their colleagues from ETH Zurich.
Electronic components are becoming smaller and smaller. Components measuring just a few nanometers – the size of around ten atoms – are already being produced...
Development and implementation of an advanced automobile parking navigation platform for parking services
To fulfill the requirements of the industry, PolyU researchers developed the Advanced Automobile Parking Navigation Platform, which includes smart devices,...
The world's first electrical car and passenger ferry powered by batteries has entered service in Norway. The ferry only uses 150 kWh per route, which...
On Tuesday, 19 May 2015 the research icebreaker Polarstern will leave its home port in Bremerhaven, setting a course for the Arctic. Led by Dr Ilka Peeken from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) a team of 53 researchers from 11 countries will investigate the effects of climate change in the Arctic, from the surface ice floes down to the seafloor.
RV Polarstern will enter the sea-ice zone north of Spitsbergen. Covering two shallow regions on their way to deeper waters, the scientists on board will focus...
Nanoengineers at the University of California, San Diego developed a gel filled with toxin-absorbing nanosponges that could lead to an effective treatment for skin and wound infections caused by MRSA (methicillin-resistant Staphylococcus aureus), an antibiotic-resistant bacteria. This "nanosponge-hydrogel" minimized the growth of skin lesions on mice infected with MRSA - without the use of antibiotics. The researchers recently published their findings online in Advanced Materials.
To make the nanosponge-hydrogel, the team mixed nanosponges, which are nanoparticles that absorb dangerous toxins produced by MRSA, E. coli and other...
20.05.2015 | Event News
18.05.2015 | Event News
12.05.2015 | Event News
22.05.2015 | Materials Sciences
22.05.2015 | Information Technology
22.05.2015 | Materials Sciences