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[Image above] Credit: NIST

Toward tiny, solar-powered sensors harvest energy at 80% efficiency

MIT researchers presented a new power converter chip that can harvest more than 80% of the energy trickling into it, even at the extremely low power levels characteristic of tiny solar cells. Previous ultralow-power converters that used the same approach had efficiencies of only 40%–50%. Where its predecessors could use a solar cell to either charge a battery or directly power a device, this new chip can do both, and it can power the device directly from the battery.

Single-catalyst water splitter produces clean-burning hydrogen 24/7

Stanford University scientists have invented a low-cost water splitter that uses a single catalyst to produce both hydrogen and oxygen gas 24 hours a day, seven days a week. In an engineering first, the team used lithium-ion battery technology to create one low-cost catalyst that is capable of driving the entire water-splitting reaction. Researchers discovered that nickel-iron oxide, which is cheap and easy to produce, is actually more stable than some commercial catalysts made of precious metals.

Detecting spin precession in silicon nanowires

Scientists at the U.S. Naval Research Laboratory have reported the first observation of spin precession of spin currents flowing in a silicon nanowire transport channel, and determined spin lifetimes and corresponding spin diffusion lengths in these nanoscale spintronic devices. The spin currents were electrically injected and detected using ferromagnetic metal contacts with a tunnel barrier consisting of single layer graphene between the metal and silicon nanowires.

Nanowires could be the LEDs of the future

Nanowires for LEDs are made up of an inner core of gallium nitride and a layer of indium-gallium-nitride on the outside, both of which are semiconducting materials. “The light in such a diode is dependent on the mechanical strain that exists between the two materials and the strain is very dependent on how the two layers are in contact with each other. We have examined a number of nanowires using X-ray microscopy and even though the nanowires should in principle be identical, we can see that they are different and have very different structure,” say researchers from the Niels Bohr Institute.

Biomanufacturing of CdS quantum dots

A team of Lehigh University engineers has demonstrated a bacterial method for the low-cost, environmentally friendly synthesis of aqueous soluble quantum dot nanocrystals at room temperature. Using an engineered strain of Stenotrophomonas maltophilia to control particle size, the team biosynthesized quantum dots using bacteria and cadmium sulfide to provide a route to low-cost, scalable and green synthesis of CdS nanocrystals with extrinsic crystallite size control in the quantum confinement range.

Robust new process forms 3-D shapes from flat sheets of graphene

Researchers from the University of Illinois at Urbana-Champaign have developed a new approach for forming 3-D shapes from flat, 2-D sheets of graphene. The researchers’ robust approach to integrate graphene onto 3-D microstructured surfaces maintains the structural integrity of graphene. The process incorporates three sequential steps: 1) substrate swelling using a solvent that 2) shrinks during the evaporation process, allowing graphene to 3) adapt, or conform to the shape of a prepared substrate, to achieve damage-free, large area integration of graphene on 3D microstructures.