It looks like lather under an electron microscope: American researchers have successfully produced porous, nanoscopic, hollow platinum spheres by using liposomes as blueprints.
Tiny structures made of precious metals are of interest because of their broad spectrum of biomedical, catalytic, and optical applications. Porous nanospheres, for example, are ideal for catalytic applications that require large surfaces but can work at low concentration (and consequently with little material).
Previous production methods had a disadvantage in that the spheres consisted of individual metallic nanoparticles; these were not very stable and only relatively small spheres were accessible. A team at the Sandia National Laboratories and the University of New Mexico in Albuquerque as well as the University of Georgia in Athens has now developed a clever new technique for the production of relatively large porous platinum nanocages. These spheres do not consist of individual particles, but of continuous, branched (dendritic) platinum sheets.
Liposomes are familiar to us from creams: the tiny balls of fat carry active ingredients through the skin. In the liposome that researchers working with John A. Shelnutt used as a blueprint, the mantle of fat consists of a double lipid layer. The narrow space between the two layers contains a light-activated catalyst, a tin-containing porphyrin compound. (Porphyrin frameworks are also an important component of hemoglobin.) The liposomes are placed in a solution containing a platinum salt. When these liposomes are then irradiated with light, the photocatalyst transfers electrons to the platinum ions. The resulting uncharged platinum atoms gather into tiny clumps. Once these clumps reach a certain size, they also become active and catalyze the release of more platinum atoms from the platinum salt. Atom by atom, small, flat, branched platinum structures (dendrites) form within the double lipid layer. These continue to grow until all of the platinum salt is consumed. The important thing is to make sure that the number of tin photocatalyst molecules—and thus the initial number of platinum clumps—within the liposome double layer is very high. The resulting dendrites are then close enough to each other to grow into a network; this forms a solid but porous sphere with the same size and shape as the liposome. When the liposomes are broken up, the platinum spheres remain intact. Shelnutt, his collaborator Yujiang Song, and their team were able to produce spheres with diameters up to 200 nm. These platinum spheres aggregate into foam-like structures.
John A. Shelnutt | EurekAlert!
New type of smart windows use liquid to switch from clear to reflective
14.12.2017 | The Optical Society
New ultra-thin diamond membrane is a radiobiologist's best friend
14.12.2017 | American Institute of Physics
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
14.12.2017 | Health and Medicine
14.12.2017 | Physics and Astronomy
14.12.2017 | Life Sciences