In a breakthrough new "direct-doping" process, scientists have embedded light-emitting nanoparticles into glass so that it remains almost perfectly transparent, but glows brightly when stimulated by lower frequency light. Able to be molded in almost any shape, and even extruded into optical fibers, the researchers claim that this new "hybrid glass" could be used to create new smart glass devices, including smart 3D displays and remote radiation sensors.

Australian researchers at the University of Adelaide, in collaboration with Macquarie University and the University of Melbourne, created this glowing glass by molding upconversion luminescent nanoparticles directly into the translucent material using a two-temperature glass-melting technique. The embedded nanoparticles produce luminescence when two or more low-energy, longer wavelength (usually infrared) photons are absorbed by the particles which then emit a single higher-energy, shorter wavelength photon in return.

"These novel luminescent nanoparticles, called upconversion nanoparticles, have become promising candidates for a whole variety of ultra-high tech applications such as biological sensing, biomedical imaging and 3D volumetric displays," says Dr Tim Zhao, from the University of Adelaide's School of Physical Sciences and Institute for Photonics and Advanced Sensing (IPAS). "Integrating these nanoparticles into glass, which is usually inert, opens up exciting possibilities for new hybrid materials and devices that can take advantage of the properties of nanoparticles in ways we haven't been able to do before."

Dr Zhao believes that applications for this type of glass could include using luminescent glass pipettes to investigate individual neurons in the brain, rather than the current dye and guiding-laser methods, as the luminescent glass could be used like a flashlight to help guide surgeons through the complex pathways.

The researchers also believe that their new direct-doping approach could be used to embed other types of nanoparticles that could have photonic, electronic, or magnetic properties that would make the glass useful in a wide range of scientific areas.

"If we infuse glass with a nanoparticle that is sensitive to radiation and then draw that hybrid glass into a fiber, we could have a remote sensor suitable for nuclear facilities," says Dr Zhao.

Prior to this research, integrating glass with upconversion nanoparticles required relatively slow and cumbersome methods where the nanoparticles needed to be "grown" within the glass. This resulted in long wait times and, more importantly, uneven distribution of the particles within the glass itself.

"With our new direct doping method, which involves synthesizing the nanoparticles and glass separately and then combining them using the right conditions, we've been able to keep the nanoparticles intact and well dispersed throughout the glass," says Dr Zhao. "The nanoparticles remain functional and the glass transparency is still very close to its original quality. We are heading towards a whole new world of hybrid glass and devices for light-based technologies."

The research was recently published in the journal Advanced Optical Materials.