The making of three-dimensional nanostructured materials has become a fertile area of research, producing materials that are useful for electronics, photonics, phononics and biomedical devices. But the methods of making such materials have been limited in the 3-D complexity they can produce. Now, an MIT team has found a way to produce more complicated structures by using a blend of current "top-down" and "bottom-up" approaches. Their new 3D nanofabrication method makes it possible to manufacture complex multi-layered solids all in one step.
A high-temperature superconductor can now be switched on and off within a trillionth of a second. A team of physicists has realized an ultrafast superconducting switch by using intense terahertz pulses. This experiment opens up the possibility to discover more about the still unsettled cause of this type of superconductivity, and also hints at possible applications for ultrafast electronics in the future.
Observation of a scientific rule being broken can sometimes lead to new knowledge and important applications. Such would seem to be the case when scientists created artificial molecules of semiconductor nanocrystals and watched them break a fundamental principle of photoluminescence known as Kasha's rule. Named for chemist Michael Kasha, who proposed it in 1950, Kasha's rule holds that when light is shined on a molecule, the molecule will only emit light (fluorescence or phosphorescence) from its lowest energy excited state. This is why photoluminescent molecules emit light at a lower energy than the excitation light. While there have been examples of organic molecules, such as azulene, that break Kasha's rule, these examples are rare. Highly luminescent molecular systems crafted from quantum dots that break Kasha's rule have not been reported – until now.
Researchers have discovered a way to capture and harness energy transmitted by such sources as radio and television transmitters, cell phone networks and satellite communications systems. By scavenging this ambient energy from the air around us, the technique could provide a new way to power networks of wireless sensors, microprocessors and communications chips.