University of Michigan researchers have discovered a way to make nanocrystals in a fluid assemble into free-floating sheets the same way some protein structures form in living organisms.
"This establishes an important connection between two basic building blocks in biology and nanotechnology, that is, proteins and nanoparticles, and this is very exciting for assembling materials from the bottom up for a whole slew of applications ranging from drug delivery to energy," said Sharon Glotzer, professor of chemical engineering and materials science and engineering.
Glotzer and Nicholas Kotov, associate professor of chemical engineering, and their graduate students and post doctoral researchers have co-authored a paper scheduled to appear Oct. 13 in the journal Science.
"The importance of this work is in making a key connection between the world of proteins and the world of nanotechnology" Kotov said. "Once we know how to manipulate the forces between the nanoparticles and their ability to self-organize, it will help us in a variety of practical applications from light-harvesting nanoparticle devices to new drugs which can act like proteins, but are actually nanoparticles."
The sheets, which can appear colored under UV illumination from bright green to dark red depending on the nanoparticle size, are made from cadmium telluride crystals, a material used in solar cells. The sheets are about 2 microns in width, about 1/5 the thickness of a human hair.
Scientists have long known how to coax nanoparticles into forming sheets, Glotzer said. But those sheets have only been achieved when the particles were on a surface or at an interface between two fluids, never while suspended in a single fluid.
The work started in Kotov's lab three years ago, when he and his team observed the sheets in experiments. Though they created them, they weren't sure how.
"We were aware of certain proteins in living organisms that self-assemble into layers, called S-layers," Kotov said. S-layer proteins comprise the outermost cell envelope of a wide variety of bacteria and other single-celled, prokaryotic organisms called archaea, and they are able to form 2-d sheets with square, hexagonal, and other packings at surfaces and interfaces, as well as suspended in fluid. The group sought to make the connection between the forces governing S-layer protein assembly and the forces governing the nanoparticle assembly. That's when Glotzer's group, whose expertise is in computer modeling and simulation, became involved.
"It's likely that the forces between S-layer proteins are highly anisotropic, and we suspected this was also a feature of the nanoparticles," Glotzer said. "Computer simulations allowed us to further develop and test this hypothesis."
Post doctoral researcher Zhenli Zhang of Glotzer's group tried various combinations of forces based on information gleaned from experiments performed by post doctoral Zhiyong Tang of Kotov's group. The team discovered that the unique shape of the CdTe nanocrystals gave rise to a combination of forces that conspired to produce the unusual two-dimensional packing. Subsequent experiments by Kotov's group showed that if any of the forces were missing, the sheets would not form, confirming the simulation predictions.
"Self-assembly is nature's basic building principle for producing organized arrays of biomolecules with controlled geometrical and physicochemical surface properties," Glotzer said. "In the fabrication of functional nanoscale materials and devices, self-assembly offers substantial advantages over traditional manufacturing approaches, if we can design the building blocks appropriately. This is what we're trying to do."
Laura Bailey | EurekAlert!
Two Group A Streptococcus genes linked to 'flesh-eating' bacterial infections
25.09.2017 | University of Maryland
Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
25.09.2017 | Power and Electrical Engineering
25.09.2017 | Health and Medicine
25.09.2017 | Physics and Astronomy