December 12, 2005

Nature's nano sensors

When it comes to building nanostructures, nature has humanity beat hands down. Millions of years of evolution will do that for you.

Recently scientists have proposed using the nanostructured silica shells of diatoms -- a type of algae -- to control lightwaves and as templates for micro and nanodevices.

Researchers from the Italian National Council of Research, 2nd University of Naples and University of Naples "Federico II" have carried out a detailed optical study of marine diatoms and found that their shells' luminescence changes depending on the type of gas surrounding them.

In the study, they fired laser beams at the shells of Thalassiosira rotula in the presence of nitrous oxide, acetone, ethanol, air, xylene and pyridine, and measured the wavelengths of the light emitted by the shells in response. The shells turn slightly different colors depending on the surrounding gas.

The ubiquity of diatoms and the variety of shell structures, which vary by species, make them potentially useful for chemical sensing applications. They could eventually be used, for example, in devices that monitor the environment or detect chemical warfare agents.

(Marine Diatoms As Optical Chemical Sensors, Applied Physics Letters, December 5, 2005)

Buckyballs bind to DNA

Scientists examining the interactions among nanoscale objects, living beings and the environment are uncovering nanotechnology's dark side.

Researchers from Oak Ridge National Laboratory and Vanderbilt University have used computer simulations to show that C60 molecules, or buckyballs, will attach to and deform DNA molecules in aqueous environments.

Buckyballs, which are spheres of 60 carbon atoms, have been touted as potential drug delivery vehicles. Given that the human body is an aqueous environment, the simulations show that it might not be such a good idea to flood the body with the molecules.

The study shows that buckyballs could have a negative impact on the structure and biological functions of DNA molecules. The carbon molecules bind to single- and double-stranded DNA, and bind to damaged sections of DNA molecules, which could interfere with DNA's natural self-repair process.

(C60 Binds to and Deforms Nucleotides, Biophysical Journal, December 2005)

Quantum nets advance

Scientists have taken a significant step down the road to building quantum networks, a technology that promises to extend quantum cryptography systems over long distances and eventually link quantum computers.

Quantum cryptography systems promise potentially perfect security. Quantum computers are theoretically many orders of magnitude faster than today's classical computers for certain types of very large problems.

Separate research teams from Georgia Institute of Technology and Harvard University have demonstrated (1, 2) the ability to generate a photon from one cloud of atoms, transmit it over optical fiber to another cloud of atoms, briefly store the photon there, and then release it.

The next steps in this line of research are adding a third cloud of atoms to demonstrate the necessary control of storage and retrieval from the second cloud; transmitting, storing and retrieving quantum bits, or qubits, rather than "blank" photons; increasing storage times and improving the quality of the quantum information transmitted by the prototype network.

When perfected, the systems the researchers are developing could be used as quantum repeaters -- the devices needed to boost fading signals in quantum communications networks.

(Storage and Retrieval of Single Photons Transmitted between Remote Quantum Memories, Electromagnetically Induced Transparency with Tunable Single-Photon Pulses, Nature, December 8, 2005)

Shocks produce laser-like light

It looks like blasting crystals with shock waves makes them shine.

A theoretical study by researchers from Lawrence Livermore National Laboratory and the Massachusetts Institute of Technology predicts a new type of coherent light similar to the light produced by lasers.

Shock waves through a crystalline material should produce coherent electromagnetic radiation in the terahertz frequency range. Terahertz waves fall between microwaves and infrared radiation in the electromagnetic spectrum.

The speed of the shock waves and the distance between the atoms or molecules in the crystal determine the exact frequency of the emitted light. The technique could be used as a way of identifying the structure of crystal materials, which helps determine their optical, mechanical and electronic properties.

(Coherent Optical Photons from Shock Waves in Crystals, Physical Review Letters, accepted for publication)

Bits and pieces

A chip traps individual ions (as opposed to neutral atoms -- see Chip protects single atoms, TRN, June 30/July 7, 2004), which opens a promising route to quantum computers; a geometric approach promises to improve data mining -- the practice of extracting information from large amounts of computer data; "smart fluid" valves speed biochips.