Girar, girar, girar sin parar...

Post cortito: Para que veáis las propiedades RARAS que pueden tener las cosas pequeñas,
os comento una que tienen las partículas pequeñitas, (más que lo nano, claro) como por ejemplo un electrón. Éste tiene una propiedad llamada spin, con valor 1/2... Hasta aquí OK.
Pequeño experimento: Levántate y gira 360º... ok. Si sabes que 360º es una vuelta entera,
habrás visto que estás en tu posición original. Ok. Para esto no hace falta saber física.
Pues bien, si pudiéramos coger un electrón, y girarlo 360º.... ¡¡¡¡¡NO QUEDA EN EL MISMO ESTADO QUE ESTABA!!!! Para que quede exactamente tal y como estaba, hay que girarlo 720º... ¡Dos vueltas!
Raro, ¿eh?

Folios de nanotubos de carbono

¡La leche! Leo en la web de la universidad de Texas (www.utdallas.edu) (Y no, no me recordéis qué presidente de EEUU es de allí...) que científicos de esa uni, han sido capaces de desarrollar un papel, o unas láminas, o una tela, como lo queráis llamar, hecha con Nanotubos de Carbono. En la figura de la izquierda se ve un modelo esquemático de lo que ocupa un Nanotubo de Carbono... casi nada!!! (La "pelota de fútbol" es un C60 o fullereno o buckyball, ya los veremos en otro post).Estos de la figura tienen sólo una capa de atomos, de alto unos pocos nanómetros (nm) ... Para que nos hagamos una idea, algunos tienen, tan sólo 1,4 nm... ¿es ésto poco? !Pues bien poco! Un nanotubo de carbono te ve a tí de grande, como verías tú a un tipo que midiera... ¡¡¡3 veces la distancia de la tierra a la luna!!!

Y bueno, con estas cositas tan pequeñas, han conseguido hacer un papel que es mucho más fuerte que si estuviera hecho con acero: Su relación peso-resistencia es MUY GRANDE. Además, estas hojas de nanotubos presentan finidad de aplicaciones: Sensores, músculos electrónicos, pantallas planas flexibles, para baterías, pilas de combustible, velas solares...

(Una vela solar es una capa, tela o lámina, que refleja la luz, y que impulsa por tanto a las naves que la llevan. Esto no es ciencia ficción, ¡es física!. Una vela solar de 1 kilómetro cuadrado fabricada con estas hojas de nanotubos pesaría solo 30 kg...Impresionante.)

No penséis que se trata de un simple avance de laboratorio de científicos locos, no. Este equipo ha conseguido fabricación industrial de los mismos: 7 metros de este papel de nanotubos por minuto... Ésto es lo que parece más increíble de todo, pero ¡ahí está!.

De lo que no he leído nada todavía es del precio que tiene... Pero si es realmente interesante, lo veremos pronto en nuestras casas.

Quantum dots

Mmmm. Quantum dots... what the hell are them?

This is the name used for very small things, with all of their three dimensions (length, width and height) in the order of magnitude of the nanometers. (One of the next posts will be devoted to how big a nanometer is). Just like a dot. Small, simple, but quite useful!

They can be fabricated over surfaces, like the one in the photograph, or just free, as dust or diluted in some liquid, more often called nano-particles. The photograph shows an InAsN (Indium Arsenide Nitride) quantum dot over a GaAs surface, as measured by Atomic Force Microscopy. I fabricated this using our MBE in the lab.

This dot is around 30 nm x 40 nm, and only 4 nm in heigth (around 14 or 15 atomic monolayers)... Very small, isn't it?

The applications of these dots grown on a surface are a lot:
They can be used as single photon emitters, for quantum cryptography (secure internet connections far from the scope of Echelon), in the active layer of semiconductor lasers for fiber optic communication systems (to bring you much more bandwidth for your DSL connection), ordered to form arrays for optical detection, (detection of forestal fire from space), in CCD infrared cameras (to detect buried people in natural disasters, for example), ...

Nano-world: Where Quantum Physics describes reality

The nano-world may seem amazing when observed from the point of view of its potential applications. But it may seem even more amazing if we think that at this nanoscale, only Quantum Mechanics can give reasonable explanations of the phenomena occuring at this level.
When reducing the size of things, strange things may happen. Strange, because in our macroscopic level the tricks of quantum mechanics cannot be clearly felt. A Paradox proposed by
E. Schrödinger, Nobel Prize in Physics in 1933, will help us to understand some of these strange phenomena...

This paradox is called Schrödinger's cat. Imagine a cat (capado o sin capar ;) ) in a box, together with a radiactive atom. If this radiactive atom disintegrates, it will break a poisonous bottle, which will immediately kill the cat. Imagine that the probability of the atom to disintegrate is 50%. This atom, as it is very small, is described by Quantum Mechanics Laws. QM says that one CAN NOT know wether the atom is disintegrated or not. It can only predict the possibility (50%) for that to occur. That means that the atom is described by a mixture of states, 50% normal, 50% disintegrated. We can ONLY know EXACTLY if it's desintegrated or not once we OPEN the box and SEE (measure) it.

Uffffff, ok. An atom that should be described by a mixture (entanglement) of states, 50% on, 50% off...Crazy physicists... But... what about the cat? The cat, as it is forming a quantum system with the atom, must also be described by quantum mechanics... so, the CAT IS 50% ALIVE AND 50% DEAD at the same time!!!! We can only know the "state" of the cat (if it is dead or not) by opening the box. If we open the box, a phenomenon called "collapse" occur, and we will observe the cat ONLY in one of the states, alive or death... But until then, the cat is dead and alive in the same amount... Incredible! But true!

This is only one example of the phenomena occuring at the nano-level... Too far from our common-sense!!! (One of the less common senses found among people, as one of my teachers usually said.. :D ).

Nanotechnology and Medicine

Have you ever read "Fantastic Voyage" ("Viaje alucinante", in Spanish)? There, Isaac Asimov invented a story where a man was miniaturized together with a kind of spaceship, and was inserted into a man's body. The possibilities of this really fantastic voyage would be incredible: The destruction of cancer cells, the possibility of in-situ nano-surgery, ...
This is still science-fiction, since the reduction of matter is not physically possible. Protons are that size, neutrons are those...
But what really is being developed at the moment, an it's NOT sci-fi, is the application of nanotechnology to the medicine, what nano-people usually call nanomedicine. I have not described the actual size of 1 nanometer (I hope it will be the next post), but let's make a fast comparison. Have you ever seen a red blood cell? We know that our blood is red because it contains billions and trillions of little red blood cells. They are so small they cannot be seen by the naked eye. But you can measure their diameter by lots of methods (I did it using diffraction, at the university), and they are around 7 microns in diameter... 7 micron.. so what? 7 microns are 7000 (seven thousand) times the size of a nanometer... (Imagine that 1 nanometer would be your sizel: Then, the diameter of a red blood cell would be like 10 km long in our real world (!!!)).
Thus, if we can design structures of tens of a nanometer, we will be able to develop nanostructures capable of handling biological systems, from the bottom-up approach. Possible applications for these nanostructures would be carrying drugs to be delivered exactly at the cancerous cells, or nanostructures containing radioactive atoms, radiating only the tumoral areas, ...
This structures are so small they can perfectly serve for all these purposes. And it's not science-fiction. It's being done by researchers throughout the world.
Particularly, in Spain, groups in the USC , leaded by José Rivas and María José Alonso, are making research in this direction: They are patenting lots of discoveries in the nanomedicine area, working in nanosystems delivering insuline, and nano-delivery of drugs.
I particularly enjoy science-fiction, by I enjoy much more when Science broadens and conquers the land of sci-fi to bring it to real life with applications for human development.

Don't walk on the grass...

The usual way to finish the sentence used as the title for this news, in my home town, leganés, is:
"....!fúmatela!" (meaning: Smoke it!). But chinese nanotechnology researchers do n0t think the same as us (Spain is different!): I read in the Nanotechnology journal a paper entitled: "Obtaining carbon nanotubes from grass". Wow! Have you got a garden? Take some grass, place it in a fast oven, and... voilà! You get carbon nanotubes (CNTs). The grass, containing lignin and cellulose (in the vascular bundles), annealed at 600ºC in an oxygen atmosphere, dehydrate and turn into CNTs of diameters between 30 and 50 nm...
Incredible? Not at all. Approaches like this one are needed to generate tons of CNTs to be used in the industry. If straw, for example, can be used for this purpose, the price of a kilogram of CNTs should decrease a lot, and could be applied to lots of applications, from construction materials to nanoelectronics.

Second Input

Yeah, it's still not very interesting, but some quantum mechanics problems do not allow me to write something interesting about the nano-world. Just in case somebody's looking for a PhD in nanomachines, here is an interesting offer (in Madrid, Spain): "Towards the comprehension of the structural richness of molecular nanomachines" (It's possibly an spanglish translation...) Hope it's useful for somebody (I'm interested in that, but it's better for me to finish my undergraduate physics courses...). It seems quite interesting, the potential of these theoretically possible machines is almost infinite...