Invisible Glass

If you have ever watched television in anything but total darkness, used a computer while sitting underneath overhead lighting or near a window, or taken a photo outside on a sunny day with your smartphone, you have experienced a major nuisance of modern display screens: glare. Most of today’s electronics devices are equipped with glass or plastic covers for protection against dust, moisture, and other environmental contaminants, but light reflection from these surfaces can make information displayed on the screens difficult to see. Now, scientists at the Center for Functional Nanomaterials (CFN) — a U.S. Department of Energy Office of Science User Facility at Brookhaven National Laboratory — have demonstrated a method for reducing the surface reflections from glass surfaces to nearly zero by etching tiny nanoscale features into them.

Whenever light encounters an abrupt change in refractive index (how much a ray of light bends as it crosses from one material to another, such as between air and glass), a portion of the light is reflected. The nanoscale features have the effect of making the refractive index change gradually from that of air to that of glass, thereby avoiding reflections. The ultra-transparent nanotextured glass is antireflective over a broad wavelength range (the entire visible and near-infrared spectrum) and across a wide range of viewing angles. Reflections are reduced so much that the glass essentially becomes invisible.

This “invisible glass” could do more than improve the user experience for consumer electronic displays. It could enhance the energy-conversion efficiency of solar cells by minimizing the amount of sunlight lost to refection. It could also be a promising alternative to the damage-prone antireflective coatings conventionally used in lasers that emit powerful pulses of light, such as those applied to the manufacture of medical devices and aerospace components.

We’re excited about the possibilities,” said CFN Director Charles Black, corresponding author on the paper published online on October 30 in Applied Physics Letters. “Not only is the performance of these nanostructured materials extremely high, but we’re also implementing ideas from nanoscience in a manner that we believe is conducive to large-scale manufacturing.”

Our role in the CFN is to demonstrate how nanoscience can facilitate the design of new materials with improved properties,” concluded Black. “This work is a great example of that–we’d love to find a partner to help advance these remarkable materials toward technology.”

Source: https://www.eurekalert.org/

Ultra Thin Nightvision Glasses Based On NanoPhotonics

Scientists from the Australian National University (ANU) have designed a nano crystal around 500 times smaller than a human hair that turns darkness into visible light and can be used to create light-weight night-vision glasses. Professor Dragomir Neshev from ANU said the new night-vision glasses could replace the cumbersome and bulky night-vision binoculars currently in use.

ultra-thin-nano-crystal-film_anu-1

The nano crystals are so small they could be fitted as an ultra-thin film to normal eye glasses to enable night vision,” said Professor Neshev from the Nonlinear Physics Centre within the ANU Research School of Physics and Engineering.

This tiny device could have other exciting uses including in anti-counterfeit devices in bank notes, imaging cells for medical applications and holograms.”

Co-researcher Dr Mohsen Rahmani said the ANU team’s achievement was a big milestone in the field of nanophotonics, which involves the study of behaviour of light and interaction of objects with light at the nano-scale.

nightvision-glasses

These semi-conductor nano-crystals can transfer the highest intensity of light and engineer complex light beams that could be used with a laser to project a holographic image in modern displays,” said Dr Rahmani, a recipient of the Australian Research Council (ARC) Discovery Early Career Researcher Award based at the ANU Research School of Physics and Engineering.

PhD student Maria del Rocio Camacho-Morales said the team built the device on glass so that light can pass through, which was critical for optical displays.

Source: http://www.anu.edu.au/

Smart Windows Clean Themselves, Save Energy

A revolutionary new type of smart window could cut window-cleaning costs in tall buildings while reducing heating bills and boosting worker productivity. Developed by University College London (UCL) with support from EPSRC, prototype samples confirm that the glass can deliver three key benefits:
Self-cleaning: The window is ultra-resistant to water, so rain hitting the outside forms spherical droplets that roll easily over the surface – picking up dirt, dust and other contaminants and carrying them away. This is due to the pencil-like, conical design of nanostructures engraved onto the glass, trapping air and ensuring only a tiny amount of water comes into contact with the surface.
 Energy-saving: The glass is coated with a very thin (5-10nm) film of window-cleaning of vanadium dioxide which during cold periods stops thermal radiation escaping and so prevents heat loss; during hot periods it prevents infrared radiation from the sun entering the building.
 Anti-glare: The design of the nanostructures also gives the windows the same anti-reflective properties found in the eyes of moths and other creatures that have evolved to hide from predators.

self cleaning windowA scanning electron miscroscope photograph shows the pyramid-like nanostructures engraved onto glass: at 200nm they are 100 times smaller than a human hair. Controlling the surface morphology at the nanoscale allows scientists to tailor how the glass interacts with liquids and light with high precision

This is the first time that a nanostructure has been combined with a thermochromic coating. The bio-inspired nanostructure amplifies the thermochromics properties of the coating and the net result is a self-cleaning, highly performing smart window, said Dr Ioannis Papakonstantinou of UCL. The UCL team calculate that the windows could result in a reduction in heating bills of up to 40 per cent.

Source: https://www.epsrc.ac.uk/

Boosted Lithium Sulfur Batteries For Electric Car

Lithium-sulfur batteries have been a hot topic in battery research because of their ability to produce up to 10 times more energy than conventional batteries, which means they hold great promise for applications in energy-demanding electric vehicles.
However, there have been fundamental road blocks to commercializing these sulfur batteries. One of the main problems is the tendency for lithium and sulfur reaction products, called lithium polysulfides, to dissolve in the battery’s electrolyte and travel to the opposite electrode permanently. This causes the battery’s capacity to decrease over its lifetime.
Researchers in the Bourns College of Engineering at the University of California, Riverside have investigated a strategy to prevent this “polysulfide shuttling” phenomenon by creating nano-sized sulfur particles, and coating them in silica (SiO2), otherwise known as glass.
Bourns College
Ph.D. students in Cengiz Ozkan’s and Mihri Ozkan ‘s research groups have been working on designing a cathode material in which silica cages “trap” polysulfides having a very thin shell of silica, and the particles’ polysulfide products now face a trapping barrier – a glass cage. The team used an organic precursor to construct the trapping barrier.

Our biggest challenge was to optimize the process to deposit SiO2 – not too thick, not too thin, about the thickness of a virus”, Mihri Ozkan said.
The work is outlined in the journal Nanoscale.
Source: http://ucrtoday.ucr.edu/

The World’s Thinnest Sheet of Glass Is Two Atoms Thick

Researchers at Cornell and Germany’s University of Ulm have created the world’s thinnest pane of glass, a step towards a nanocomputer. The glass, made of silicon and oxygen, formed accidentally when the scientists were making graphene, an atom-thick sheet of carbon, on copper-covered quartz. They believe an air leak caused the copper to react with the quartz, which is also made of silicon and oxygen, producing a glass layer with the graphene. The glass is a mere three atoms thick—the minimum thickness of silica glass—which makes it two-dimensional.

Direct Imaging of a Two-Dimensional Silica Glass on Graphene
Although this is the first time such a thin sheet of freestanding glass has been produced, the image, taken with an electron microscope, isn’t entirely new. The “pane” of glass, so impossibly thin that its individual silicon and oxygen atoms are clearly visible via electron microscopy, was identified in the lab of David A. Muller, professor of applied and engineering physics and director of the Kavli Institute at Cornell for Nanoscale Science.
The two-dimensional glass could find a use in transistors, by providing a defect-free, ultra-thin material that could improve the performance of processors in computers and smartphones.

The paper, “Direct Imaging of a Two-Dimensional Silica Glass on Graphene,” was published in Nano Letters on Jan. 23, 2012, with first authors Pinshane Huang, a Cornell graduate student, and Simon Kurash, a University of Ulm graduate student. It includes collaborators from the University of Ulm, Germany; the Max Planck institute for Solid State Research in Germany; University of Vienna; University of Helsinki; and Aalto University in Finland.

Source: http://pubs.acs.org/
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http://www.news.cornell.edu/

Ultra-sensitive Tool for DNA analysis, thanks to Ancient Roman Cup

Utilizing optical characteristics first demonstrated by the ancient Romans, researchers at the University of Illinois at Urbana-Champaign have created a novel, ultra-sensitive tool for chemical, DNA, and protein analysis..plasmon resonance sensor
With this device, the nanoplasmonic spectroscopy sensing, for the first time, becomes colorimetric sensing, requiring only naked eyes or ordinary visible color photography,” explained Logan Liu, an assistant professor of electrical and computer engineering and of bioengineering at Illinois. “It can be used for chemical imaging, biomolecular imaging, and integration to portable microfluidics devices for lab-on-chip-applications“. His research team’s results were featured in the cover article of the inaugural edition of Advanced Optical Materials (AOM, optical section of Advanced Materials).

Roman Cup
Lycurgus cups were created by the Romans in 400 A.D. Made of a dichroic glass, the famous cup exhibits different colors depending on whether or not light is passing through it; red when lit from behind and green when lit from in front. It is also the origin of inspiration for all contemporary nanoplasmonics research—the study of optical phenomena in the nanoscale vicinity of metal surfaces.
Source: http://engineering.illinois.edu/