martedì 20 maggio 2014

                                                   Jumping  into a nano blue land

          Different technologies has been implemented to make water consumption more efficient and available in a world where almost 1 billion people still have no access to this blue gold and other millions die because of contaminated water.                                                                                                                               
          Scientists started looking for solutions  at the “bottom”of the materil, at atom level, jumping into nano-demantion land.First of all nanoparticles did not come out  in these decades as it may seem  but they have a long history.  Nanoparticles ante litteram was already exploited by Roman artisans in IV century,  and during the Middle Ages master glaziers included small amount of metal oxide to make amazing colorful glass wall. But only at the end of XX century  scientific researches  and the development of sophisticated instruments like STM (Scanning Tunnelling Microscope)  made possible the comprehension about the properties of nanoparticles and their handling.
      Nowadays particular nano structures built with a specific chemical and structural conformations are being more and more studied, from the nanoshells or golden nano particles  as non invasive treatment agaist cancer in the devopling field of nanomedicine  to new nano materials used in energy engineering; we have a great list but let’s focus on what concerns our topic.
It is  well known the story of Graphene, a one-atom thick layer of graphite, made of only carbon atoms that are densely packed in a regular sp2-bounded atomic hexagonal pattern. This 2-dimantional nano strucure  is remarkably strong for its very low weight (100 times stronger than steel), it conducts heat and electricity efficiently, it is the basic strucure element for nanotubes and fullerenes and because  of its significant properties it has been subject of increasing number of researches and studies. At MIT , for instance, Jeffrey C. Grossman, an associate professor of power engineering, and his graduate students David Cohen-Tanugi and Shreya Dave are developing a filtration material made of a sheet of nanoporous graphene. The holes in the graphene are small enough to block salt ions while letting water molecules through. This is   a  process of desalination that applays reverse osmosis principle, which relies on semipermeable membranes to filter salt from water. But such systems demand high pressure to force water ( agaist osmosis)  through the membranes which are about a thousand times thicker than ones made of graphene. Moreover graphene is 500 more permeable.

      Another study conducted by Jin-Woo Kim at the University of Arkansas  has tested the effectivness of multi-walled carbon nanotubes (MWNT) , smooth pipes of water-repelling graphite,  in cleaning contaminated water.  Keeping  it simple, by exploiting the magnetic susceptibility and bacterial affinity of nanotubes pathogenes are captured and enbodied in MWNTs cluster, then separetad from water through an external magnet.                                                                                                                        
      Conventional purification methods such as chlorination, standard filtration, UV radiation, and the infusion of water with ozone gas, aren’t that cheap, nor are they always practical for developing countries therefore  the challenge is  to make the purification  process more efficient, affordable, and available to more people through nanotechnology.
At this link you can see a reasonalble cheap nanofilter  realized using peculiar properties of nanoparticles

       If you want to have a general view and to know more about  nanotech and this fascinating nanoworld an easy but complete and well written, though only in italian, book that I can suggest is “ Quanto è piccolo il mondo”by Gianfranco Pacchioni.

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