Posted by Iván Camacho Anguiano | Posted in Extras Química, Mezclas, compuestos y elementos, Química | Posted on 13 Enero 2012
La ciencia cantada. Genial video presentado por Morgan Freeman, Michio Kaku, Stephen Hawking, Brian Cox, Richard Feynman y Frank Close. Se darán participaciones a los alumnos de tercero que sean los primeros en comentar (aquí en el blog, dentro de este post) sobre qué trata el video y quiénes son los personajes que aparecen en él y por qué son importantes.
Posted by Iván Camacho Anguiano | Posted in Curiosidades, Mezclas, compuestos y elementos, Proyectos y experimentos, Química | Posted on 26 Diciembre 2011
Posted by Iván Camacho Anguiano | Posted in Extras Química, Mezclas, compuestos y elementos, Proyectos y experimentos, Química | Posted on 15 Diciembre 2011
Posted by Iván Camacho Anguiano | Posted in Extras Química, Mezclas, compuestos y elementos, Química | Posted on 29 Septiembre 2011
by Benjamin Skuse
CONTRARY TO POPULAR BELIEF, graphene is not a recent discovery. It was observed for the first time in 1962 by German chemists Ulrich Hofmann and Hanns-Peter Boehm, the latter giving the material its name. But while some scientists had known about graphene for decades, its unique properties remained undiscovered.
This all changed when Andre Geim and Konstantin Novoselov from the University of Manchester in the UK used Sellotape to peel off a single layer of graphite from a pencil, studying the residue in detail.
What they found was stunning enough for them to be awarded the 2010 Nobel Prize in Physics. Graphene is a material like no other.
A two-dimensional material only one atom thick that is, gram for gram, stronger than any other material known to man. Graphene is peculiar in that its strength is matched by great flexibility.
While this is incredible in itself it is not the end of the story, as graphene is also transparent, light and a fantastic conductor, being able to carry more electricity more efficiently, more rapidly and with more precision than any other material.
ALL OF THESE PROPERTIES AND MORE have got scientists incredibly excited, with many research papers being published on the subject every day, and hundreds of start-up companies and well-known multinational technology companies investing heavily in graphene.
Yet, despite all the hype and heavy investment, there are still no graphene products on the market. It’s a curious situation that could be set to change.
Recently there have been a number of proof-of-concept demonstrations, which have shown that graphene will soon be incorporated into numerous devices we use every day.
So now is the perfect time to ask, exactly what have we got to look forward to?
NEARLY ALL ELECTRONIC PRODUCTS CURRENTLYon the market have displays (such as TVs, computer monitors, mobile phones and cameras) containing indium tin oxide (ITO).
ITO is transparent and highly conductive, making it ideal for these applications, but indium is becoming increasingly rare and therefore more expensive.
In contrast, graphene is derived from carbon, which is (practically) limitless in abundance, cheap and easily recyclable.
Another limitation of ITO is that it is not very flexible. “This isn’t a problem in rigid glass displays like those in today’s telephones, but is a limitation in the displays envisioned by materials scientists and electrical engineers,” explains Nathaniel D Robinson, a researcher from Linköping University in Sweden.
Graphene, then, could not only replace ITO but change the face of electronics – from something static to something highly flexible. Think ‘roll up’ TVs and computers, and stretchy, flexible wireless devices that could morph from being a phone, to a wristwatch, to a laptop or mobile TV.
The possibilities – with graphene – are practically limitless.
THIS MAY ALL SOUND a little fanciful, but many of the initial hurdles to making such devices a reality have already been overcome. For instance, a 76 centimetre-wide, flexible and transparent graphene touchscreen was recently demonstrated by Korean researchers in collaboration with Samsung.
Not only is this the largest film of graphene ever created but it was also produced in a way that could easily transfer to mass manufacturing. Of course, having a flexible touchscreen is not much use if the rest of the device is rigid.
Amazingly though, great steps have also been made in this area, with IBM leading the way: first presenting a wafer-scale graphene transistor in 2010 and very recently unveiling a proof-of-concept graphene circuit, which operates as an analogue broadband radio frequency mixer.
Combining these flexible screens and flexible circuits into a bendy device will be a challenge, but some researchers believe we may begin to see these types of devices on the market as early as 2013
Whilst high-profile applications such as flexible electronics hog the limelight, a number of other products and devices might change our world in more unexpected ways.
Among them, graphene has been touted as a key component of hydrogen fuel cells in future cars due to its unmatched impermeability, as electrodes to carry the current to and from better, cheaper solar cells and as a super-efficient replacement for batteries.
ONE OF THE LESS WELL KNOWN properties of graphene is that it is electrochemically stable. This makes it an ideal material to be used in light-emitting electrochemical cells (LECs).
When the electrochemical stability of graphene is combined with its flexibility and transparency, the possibilities increase dramatically, says Robinson: “Many people visualise LECs as ‘light-emitting wallpaper’. Others would like to see a conformable large-area lamp.”
“Furthermore, if a transparent organic layer is used in combination with two graphene electrodes, the resulting device would itself be nearly transparent when it is off. This would make a very interesting window, which one can look through during the day and ‘turn on’ at night for both privacy and light.”
But Robinson adds a word of caution that making graphene, which is both transparent and conductive enough for large-area light-emitting devices, is a tough challenge.
ANOTHER APPLICATION LIKELY TO APPEAR in the near future will make use of the materials incredible strength. When added to composite materials graphene could make our aircrafts, boats, tyres and buildings considerably stronger.
As Novoselov elucidates: “You create a composite material which has all the benefits from the traditionally used carbon nanofibres but stronger, and you can also monitor strain in it.”
The latter property will be particularly useful because strain could be continuously monitored via graphene in aircraft parts or racing cars, for example, which could prevent catastrophic accidents resulting from failure.
So why are we not adding graphene to composites right now? “It used to be the problem of how to create large enough quantities of graphene, but this problem is more or less resolved now,” remarks Novoselov. “The problems are only technical and psychological now: how to implement it into real production.”
THE SUPERLATIVES FOR GRAPHENE SEEM TO NEVER END. NASA’s Spitzer Space Telescope recently detected the first extraterrestrial signature of graphene in two small galaxies. Scientists believe it could hold clues to how carbon-based life developed.
This finding opens up graphene’s possibilities even beyond applications in our immediate, physical surroundings.
Novoselov believes we are only at the beginning of discovering the material’s range of uses: “We still haven’t explored our imagination completely yet because it really has a combination of unique properties.”
Posted by Iván Camacho Anguiano | Posted in Curiosidades, Extras Química, Mezclas, compuestos y elementos, Química | Posted on 22 Agosto 2011
Crittervision: What a dog’s nose knows
- 22 August 2011 by Caroline Williams
Ever wondered how a dog, with a sense of smell that may be thousands of times more sensitive than ours, can bear to bury its face in the trash can? Alexandra Horowitz, a dog-cognition researcher at Columbia University in New York City and author of Inside of a Dog: What dogs see, smell, and know, says it’s because the dog isn’t simply smelling a stronger version of the revolting mono-stench that we smell. “It is not that smells are ‘louder’,” she says. “The smells have different layers, which probably give dogs a much bigger range of types of information.” She compares it to the way we might enjoy a painting from across the room, but appreciate it in a different way when we can get up close and see the brush strokes.
This makes a dog’s experience fundamentally different to our own. When we go out for a walk, for example, we get almost all of our information from vision. But the dog’s eyes are just a back-up. This was shown when police tracker dogs were given a scent trail that seemed to run in the opposite direction to a set of footprints on the ground; they invariably followed their noses and ignored the contradictory visual cues (Applied Animal Behaviour Science, vol 84, p 297). This reliance on smell explains why a dog that isn’t expecting to see its owner will often stop a metre or so away for a quick sniff before jumping all over them.
To imagine the scent-based world of a dog, says Horowitz, look around and imagine that everything you see has its own individual scent. And not just each object – different parts of the same object may hold different types of information. Horowitz gives the example of a rose: each petal might have a different scent, telling the dog it has been visited by different insects that left telltale traces of pollen from other flowers. Besides picking up on the individual scent of humans that had touched the flower, it could even guess when they may have passed by.
In this way, smell might give a dog a way of understanding the passage of time, Horowitz suggests. A dog can perhaps perceive the past by smelling that a dog urinated here long enough ago that the scent has changed in character and become weaker. One recent study, from 2005, showed that dogs may even be able to detect the subtle differences in odour from one footstep to the next as they follow a human’s scent trail (Chemical Senses, vol 30, p 291). The dog could imagine the future by picking up the scent of the dogs, humans or other objects coming towards them on the breeze.
Unfortunately there’s no way for a mere human to get inside this highly detailed world. Even if we get down on the ground and sniff, we cannot do it like a dog. When we sniff we are sporadically blind to scent as we breathe in and out through the same holes. A 2009 study of the fluid dynamics of the dog’s sniff showed that their system is far more complex. Each nostril is smaller than the distance between the two, which means that they inhale air from two distinct regions of space, allowing the dog to decipher the direction of a scent. The sniff also funnels stale air out through the sides of the nostrils, an action which pulls new air into the nose. Once inside the nose the air swirls around up to 300 million olfactory receptors, compared with our measly 6 million (Journal of the Royal Society Interface, vol 7, p 933).
Even if humans could gather this information, our brains wouldn’t know what to do with it: the dog olfactory cortex, which processes scent information, takes up 12.5 per cent of their total brain mass, while ours accounts for less than 1 per cent.
While we can never truly experience the world of the dog, we can at least imagine the kinds of fascinating information that a dog might get from sniffing that lamp post. And maybe, just occasionally, we will resist the temptation to tug the lead to get somewhere more “interesting”.