Molecular Foundry post-doctoral scholar Hoi Ri Moon, staff scientist Jeff Urban, and Facility Director Delia Milliron demonstrate magnesium oxide nanocrystals that could be a bright candidate for solid-state lighting. (Roy Kaltschmidt, Berkeley Lab)
Scientists at Berkeley Lab have created non-toxic magnesium oxide nanocrystals whose size can be adjusted within just a few nanometers. The nanocrystals glow blue when exposed to ultraviolet light, and could be a bright candidate for lighting that consumes less energy and has a longer lifespan. The nanocrystals could also allow researchers to probe a key pathway in carbon dioxide sequestration.

In its bulk form, magnesium oxide is a cheap, white mineral used in applications like insulating cables. Current routes for generating these alkaline earth metal oxide nanocrystals require processing at high temperatures, which causes uncontrolled growth or fusing of particles to one another - not a desirable outcome when the properties you seek are size-dependent. Vapor phase techniques, which provide size precision, are time and cost-intensive, and leave the nanocrystals attached to a substrate.

The scientists created the nanocrystals of magnesium oxide using an organometallic chemical synthesis route. “We’ve discovered a fundamentally new, unconventional mechanism for nicely controlling the size of these nanocrystals, and realized we had an intriguing and surprising candidate for optical applications,” said Delia Milliron, Facility Director of the Inorganic Nanostructures Facility at Berkeley Lab’s nanoscience research center, the Molecular Foundry. “This efficient, bright blue luminescence could be an inexpensive, attractive alternative in applications such as bio-imaging or solid-state lighting.”

Unlike conventional incandescent or fluorescent bulbs, solid-state lighting makes use of light-emitting semiconductor materials - in general, red, green, and blue emitting materials are combined to create white light. However, efficient blue light emitters are difficult to produce, suggesting the potential of these oxide nanocrystals.

The magnesium oxide nanocrystals will also “serve as a test system for modeling the kinetics of dissolution and mineralization in a simulated fluid-rock reservoir, allowing us to probe a key pathway in carbon dioxide sequestration,” said Jeff Urban, a staff scientist in the Inorganic Nanostructures Facility at the Molecular Foundry. “The geological minerals that fix magnesium into a stable carbonate are compositionally complex, but our nanocrystals will provide a simple model to mimic this intricate process.”

(Berkeley Lab)