Platinum cages: Liposomes as blueprints for hollow platinum nanospheres

Nov 02, 2006

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.

Citation: John A. Shelnutt, et al., Synthesis of Platinum Nanocages by Using Liposomes Containing Photocatalyst Molecules, Angewandte Chemie International Edition, doi: 10.1002/anie.200602403

Source: Angewandte Chemie

Explore further: Thinnest feasible nano-membrane produced

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Thinnest feasible nano-membrane produced

Apr 17, 2014

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Apr 17, 2014

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Making 'bucky-balls' in spin-out's sights

Apr 16, 2014

(Phys.org) —A new Oxford spin-out firm is targeting the difficult challenge of manufacturing fullerenes, known as 'bucky-balls' because of their spherical shape, a type of carbon nanomaterial which, like ...

User comments : 0

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...