13 Jun 2016
Australian researchers at the University of Adelaide have developed a method for embedding light-emitting nanoparticles into glass without losing any of their unique properties – a major step towards ‘smart glass’ applications such as 3D display screens or remote radiation sensors.
This new “hybrid glass” successfully combines the properties of these special luminescent (or light-emitting) nanoparticles with the well-known aspects of glass, such as transparency and the ability to be processed into various shapes including very fine optical fibres.
The research, in collaboration with Macquarie University and University of Melbourne, has been published online in the journal Advanced Optical Materials.
“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 lead author 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. For example, neuroscientists currently use dye injected into the brain and lasers to be able to guide a glass pipette to the site they are interested in. If fluorescent nanoparticles were embedded in the glass pipettes, the unique luminescence of the hybrid glass could act like a torch to guide the pipette directly to the individual neurons of interest.”
Although this method was developed with upconversion nanoparticles, the researchers believe their new ‘direct-doping’ approach can be generalised to other nanoparticles with interesting photonic, electronic and magnetic properties. There will be many applications – depending on the properties of the nanoparticle.
“If we infuse glass with a nanoparticle that is sensitive to radiation and then draw that hybrid glass into a fibre, we could have a remote sensor suitable for nuclear facilities,” says Dr Zhao.
To date, the method used to integrate upconversion nanoparticles into glass has relied on the in-situ growth of the nanoparticles within the glass.
“We’ve seen remarkable progress in this area but the control over the nanoparticles and the glass compositions has been limited, restricting the development of many proposed applications,” says project leader Professor Heike Ebendorff-Heideprem, Deputy Director of IPAS.
“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. 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.”
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More information: Jiangbo Zhao et al. Upconversion Nanocrystal-Doped Glass: A New Paradigm for Photonic Materials, Advanced Optical Materials(2016). DOI: 10.1002/adom.201600296
11 Mar 2016
Manufacturers may soon have a speedy and nondestructive way to test a wide array of materials under real-world conditions, thanks to an advance that researchers at the National Institute of Standards and Technology (NIST) have made in roll-to-roll measurements. Roll-to-roll measurements are typically optical measurements for roll-to-roll manufacturing, any method that uses conveyor belts for continuous processing of items, from tires to nanotechnology components.
In order for new materials such as carbon nanotubes and graphene to play an increasingly important role in electronic devices, high-tech composites and other applications, manufacturers will need quality-control tests to ensure that products have desired characteristics, and lack flaws. Current test procedures often require cutting, scratching or otherwise touching a product, which slows the manufacturing process and can damage or even destroy the sample being tested.
To add to existing testing non-contact methods, NIST physicists Nathan Orloff, Christian Long and Jan Obrzut measured properties of films by passing them through a specially designed metal box known as a microwave cavity. Electromagnetic waves build up inside the cavity at a specific “resonance” frequency determined by the box’s size and shape, similar to how a guitar string vibrates at a specific pitch depending on its length and tension. When an object is placed inside the cavity, the resonance frequency changes in a way that depends on the object’s size, electrical resistance and dielectric constant, a measure of an object’s ability to store energy in an electric field. The frequency change is reminiscent of how shortening or tightening a guitar string makes it resonate at a higher pitch, says Orloff.
The researchers also built an electrical circuit to measure these changes. They first tested their device by running a strip of plastic tape known as polyimide through the cavity, using a roll-to-roll setup resembling high-volume roll-to-roll manufacturing devices used to mass-produce nanomaterials. As the tape’s thickness increased and decreased–the researchers made the changes in tape thickness spell “NIST” in Morse code–the cavity’s resonant frequency changed in tandem. So did another parameter called the “quality factor,” which is the ratio of the energy stored in the cavity to the energy lost per frequency cycle. Because polyimide’s electrical properties are well known, a manufacturer could use the cavity measurements to monitor whether tape is coming off the production line at a consistent thickness–and even feeding back information from the measurements to control the thickness.
Alternatively, a manufacturer could use the new method to monitor the electrical properties of a less well-characterized material of known dimensions. Orloff and Long demonstrated this by passing 12- and 15-centimeter-long films of carbon nanotubes deposited on sheets of plastic through the cavity and measuring the films’ electrical resistance. The entire process took “less than a second,” says Orloff. He added that with industry-standard equipment, the measurements could be taken at speeds beyond 10 meters per second, more than enough for many present-day manufacturing operations.
The new method has several advantages for a thin-film manufacturer, says Orloff. One, “You can measure the entire thing, not just a small sample,” he said. Such real-time measurements could be used to tune the manufacturing process without shutting it down, or to discard a faulty batch of product before it gets out the factory door. “This method could significantly boost prospects of not making a faulty batch in the first place,” Long noted.
And because the method is nondestructive, Orloff added, “If a batch passes the test, manufacturers can sell it.”
Films of carbon nanotubes and graphene are just starting to be manufactured in bulk for potential applications such as composite airplane materials, smartphone screens and wearable electronic devices.
Orloff, Long and Obrzut submitted a patent application for this technique in December 2015.
A producer of such materials has already expressed interest in the new method, said Orloff. “They’re really excited about it.” He added that the method is not specific to nanomanufacturing, and with a properly designed cavity, could also help with quality control of many other kinds of products, including tires, pharmaceuticals and even beer.
The above post is reprinted from materials provided by National Institute of Standards and Technology (NIST). Note: Materials may be edited for content and length.
- Nathan D. Orloff, Christian J. Long, Jan Obrzut, Laurent Maillaud, Francesca Mirri, Thomas P. Kole, Robert D. McMichael, Matteo Pasquali, Stephan J. Stranick, J. Alexander Liddle. Noncontact conductivity and dielectric measurement for high throughput roll-to-roll nanomanufacturing. Scientific Reports, 2015; 5: 17019 DOI: 10.1038/srep17019