Contents:
Lights that emit radiation outside the range of human vision waste energy. Most red phosphors boost color quality in white LEDs by filling in red tones, but they also emit broadly, spilling out of the visible spectrum and into the infrared range, wasting energy and causing the light from their LEDs to score poorly in luminous efficacy. By examining a relatively unexplored family of compounds known as nitridoaluminates, the Munich-based team discovered a strontium member that, when doped with europium ions, functions as a red-emitting phosphor with a narrow emission band about 50 nm.
The sharpness of the emission in the red region means the phosphor produces relatively little infrared light, thereby wasting less energy. That advance, which would reduce power requirements and simplify the supporting electronics, could help lower the purchase price of high-CRI white-light LEDs.
Researchers have also found a new phosphor that seems to outperform those currently used in liquid-crystal displays. One hallmark of any high-quality display is its ability to depict a rich assortment of vibrant colors and hues. Because of the way LCDs create colors, that range—the color gamut—is heavily affected by the individual color components making up the white LED backlight for example, the green and red from the phosphors and the blue from the source light.
All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License. But this is all predicated, or this is all based on, this energy traveling through a medium. Student Life. This unique combination of precision and resilience is due to the Several well characterized systems of high nuclearity, e. When aiming to realize these goals and when aiming at the synthesis of potential catalysts for model systems of artificial photosynthesis, it will eventually be the chemist whose creativity, knowledge about molecular structures, and methodological competence can offer viable solutions.
The sharper the bands, the higher the quality of the LCD output and the broader the color gamut. Related: Perovskite phosphor boosts visible light communication. These phosphors were discovered in the lab, but another new one was found in silico. Efforts to discover new phosphors have nearly always occurred in an Edisonian fashion, through painstaking, trial-and-error experiments—for example, by using exploratory crystal-growth methods and combinatorial chemistry.
Using density functional theory calculations, the team screened thousands of materials, searching for stable, earth-abundant compounds that could host europium and cerium ions and be excited with blue and near-UV light. The researchers synthesized Eu- and Ce-doped versions and found they produced green-yellow and blue emission bands, respectively. Computational methods have been used for years to search for new materials for batteries, fuel cells, and catalysts, McKittrick says.
But as far as she knows, no one has ever taken this approach to search for new phosphors. Finding a new phosphor using a novel approach may be astonishing.
Just watch and see, McKittrick says. The power is now in your nitrile gloved hands Sign up for a free account to increase your articles. Or go unlimited with ACS membership. Chemistry matters.
Join us to get the news you need. Don't miss out. Renew your membership, and continue to enjoy these benefits. Not Now.
Grab your lab coat. Let's get started Welcome! It seems this is your first time logging in online. Please enter the following information to continue. As an ACS member you automatically get access to this site. All we need is few more details to create your reading experience. Not you? Sign in with a different account.
Need Help? Membership categories. Regular or Affiliate Member. Graduate Student Member. And probably the most amazing thing about light-- well, actually there's tons of amazing things about light-- but one of the mysterious things is when you really get down to it-- and this is actually not just true of light, this is actually true of almost anything once you get onto a small enough quantum mechanical level-- light behaves as both a wave and a particle.
And this is probably not that intuitive to you, because it's not that intuitive to me. In my life, I'm used to certain things behaving as waves, like sound waves or the waves of an ocean. And I'm used to certain things behaving like particles, like basketballs or-- I don't know-- my coffee cup. I'm not used to things behaving as both. And it really depends on what experiment you run and how you observe the light.
So when you observe it as a particle, and this comes out of Einstein's work with the photoelectric effect-- and I won't go into the details here, maybe in a future video when we start thinking about quantum mechanics-- you can view light as a train of particles moving at the speed of light, which I'll talk about in a second. We call these particles photons. If you view light in other ways-- and you see it even when you see light being refracted by a prism here-- it looks like it is a wave.
And it has the properties of a wave. It has a frequency, and it has a wavelength. And like other waves, the velocity of that wave is the frequency times its wavelength. Now even if you ignore this particle aspect of light, if you just look at the wave aspect of the light, it's still fascinating. Because most waves require a medium to travel through. So for example, if I think about how sound travels through air-- so let me draw a bunch of air particles.
I'll draw a sound wave traveling through the air particles. What happens in a sound wave is you compress some of the air particles and those compress the ones next to them. And so you have points in the air that have higher, I guess you could say, higher pressure and points that have lower pressure, and you could plot that.
So we have high pressure over here. High pressure, low pressure, high pressure, low pressure. And as these things bump into each other, and this wave essentially travels to the right-- and if you were to plot that you would see this wave form traveling to the right. But this is all predicated, or this is all based on, this energy traveling through a medium.
And I'm used to visualizing waves in that way. But light needs no medium. Light will actually travel fastest through nothing, through a vacuum. And it will travel at an unimaginably fast speed-- 3 times 10 to the eighth meters per second. And just to give you a sense of this, this is million meters per second.
Or another way of thinking about it is it would take light less than a seventh of a second to travel around the earth. Or it would travel around the earth more than seven times in one second. So unimaginably fast. And not only is this just a super fast speed, but once again it tells us that light is something fundamental to our universe. Because it's not just an unimaginable fast speed. Suppose you have a continuous spectrum that begins with light at a wavelength of nm, and ends with light at a wavelength of nm.
Because it's continuous, that spectrum contains light with any wavelength between nm and nm. It contains light with a wavelength of nm. It contains light with a wavelength of It even contains light with a wavelength of Write down any number including a number with decimal places that is bigger than and smaller than A continuous electromagnetic spectrum between nm and nm will include light with a wavelength equal to the number you've written down. As shown in the last section, within the visible range of the electromagnetic spectrum, a light's wavelength corresponds to its color.
Therefore, another way of defining a continuous spectrum in the visible range is to say that it is a spectrum which contains every possible color between the color at the beginning of the list and the color at the end. Figure 5.
The first continuous spectrum starts with a deep indigo blue and ends with red. Notice how the colors in this spectrum change smoothly all the way from indigo to red.
What we know as light is more properly called electromagnetic radiation. We know from experiments that light acts as a wave. As such, it can be described as . Peter Douglas and Mike Garley investigate how chemistry and light interact in many aspects of our everyday life.
There are no gaps, or missing colors. The same is true of the second continuous spectrum.