Sunday, November 18, 2012

Excellent Strategy for Fingerprint Identification using Gold nanoparticles

Identifying fingerprints on paper is a commonly used method in police forensic work, but unfortunately it is not easy to make those fingerprints visible. Now, scientists at the Hebrew University of Jerusalem have developed a new approach for making such fingerprints more readily readable.

The new method, created by a team headed by Prof. Yossi Almog and Prof. Daniel Mandler of the Institute of Chemistry at the Hebrew University, uses an innovative chemical process to produce a negative of the fingerprint image rather than the positive image produced under current methods. Unlike the latter, the Hebrew University-developed process is nearly independent of the composition of the sweat residue left behind on the paper.

In many criminal investigations, paper evidence plays an important role, and it is useful to know who has handled such documents as checks, paper currency, notes, etc. Studies have shown that less than half of the fingerprints on paper items can be made sufficiently visible to enable their identification. The main reason for this seems to be the highly variable composition of the sweat left behind on the paper.

The new procedure developed at the Hebrew University avoids these problems. It involves an inversion of an established method in which gold nanoparticles are first deposited onto the invisible fingerprints, followed by elemental silver, similar to the development of a black and white photograph.

 In the conventional technique, the gold particles get stuck to the amino acid components of the sweat in the fingerprints, and then silver is deposited onto the gold. The result is quite often low-contrast impressions of the fingerprints. In the new method, the gold nanoparticles stick directly to the paper surface, but not the sweat. This technique utilizes the sebum from the fingerprints as a medium to avoid this interference. (Sebum is an oily substance secreted by the sebaceous glands that helps prevent hair and skin from drying out.) Treatment with a developer containing silver then turns the areas with gold on them black, resulting in a clear, negative image of the fingerprint.

Since the method relies only on the fatty components in the fingerprints, the sweaty aspects play no role in the imaging process This technique also promises to alleviate another problem; for example if paper has become wet, it has previously been difficult to detect fingerprints because the amino acids in the sweat, which are the primary substrate for current chemical enhancement reactions, are dissolved and washed away by water, whereas the fatty components are barely affected. Thus, the avoidance of the sweat aspect provides a further enhancement for police laboratory.

Emerging idea of cooling of nanoscale Computer chips by Crystals


Researchers at the Carnegie Institution have discovered a new efficient way to pump heat using crystals. The crystals can pump or extract heat, even on the nanoscale, so they could be used on computer chips to prevent overheating or even meltdown, which is currently a major limit to higher computer speeds.

Researchers at the University of Chicago performed the preliminary simulations on ferroelectric crystals materials that have electrical polarization in the absence of an electric field. The electrical polarization can be reversed by applying an external electrical field. The scientists found that the introduction of an electric field causes a giant temperature change in the material, dubbed the electrocaloric effect (a phenomenon in which a material shows a reversible temperature change under an applied electric field), far above a temperature to a so-called paraelectric state.

The electrocaloric effect pumps heat through changing temperature by way of an applied electric field. The effect has been known since the 1930s, but has not been exploited because people were using materials with high transition temperatures. So low transition temperature materials are preferred, as in that way, the effect is larger if the ambient temperature is well above the transition temperature,

Ferroelectrics become paraelectric, that is, have no polarization under zero electric field above their transition temperature, which is the temperature at which a material changes its state from ferroelectric to paraelectric.
 
Scientists used atomic-scale molecular dynamics simulations, where they followed the behavior of atoms in the ferroelectric lithium niobate as functions of temperature and an electrical field.

Vortex Beams opens new possibilities for electron microscopy


Vortex beams render completely new possibilities for electron microscopy. A method of producing extremely intense vortex beams has been discovered at the Vienna University of Technology (TU Vienna).

Nowadays, electron microscopes are an essential tool, especially in the field of materials science. At TU Vienna, electron beams are being created that possess an inner rotation; these vortex beams cannot only be used to display objects, but to investigate material-specific properties with minute precision. A new breakthrough in research now allows scientists to produce much more intense vortex beams than ever before.

In a tornado, the individual air particles do not necessarily rotate on their own axis, but the air suction overall creates a powerful rotation. The rotating electron beams that have been generated at TU Vienna behave in a very similar manner. Vortex beams can only be explained in terms of quantum physics: the electrons behave like a wave, and this quantum wave can rotate like a tornado or a water current behind a ship's propeller.

After the vortex beam gains angular momentum, it can also transfer this angular momentum to the object that it collides. The angular momentum of the electrons in a solid object is closely linked to its magnetic properties. For materials science it is therefore a huge advantage to be able to make statements regarding angular momentum conditions based on these new electron beams.

Peter Schattschneider and Michael Stöger-Pollach (USTEM, TU Vienna) have been working together with a research group from Antwerp on creating the most intense, clean and controllable vortex beams possible in a transmission electron microscope. The first successes were achieved two years ago: at the time, the electron beam was shot through a minuscule grid mask, whereby it split into three partial beams: one turning right, one turning left and one beam that did not rotate.

Now, a new, much more powerful method has been developed: researchers use a screen, half of which is covered by a layer of silicon nitride. This layer is so thin that the electrons can penetrate it with hardly any absorption, however they can be suitably phase-shifted. After focusing using a specially adapted astigmatic lens, an individual vortex beam is obtained.
 
More exotic applications of vortex beams are also conceivable: in principle, it is possible to set all kinds of objects in rotation, even individual molecules using these beams, which possess angular momentum. Vortex beams could therefore also open new doors in nanotechnology.