A nano-particle, as the name itself suggests is a particle that has its diameter in the range 1 to 100 nm. The distinguishing property of nano-particles is that unlike microparticles, fine particles, and coarse particles, they are smaller in diameter, which inculcates very different physical and chemical properties in them. These different physical and chemical properties make them an interesting subject matter for different kinds of experimentation and observation.
Features of Nano-particle
Nano-particles have very distinguishable physical and chemical properties. Specifically, the electronic, chemical and optical properties of nanoparticles are very different from other bulk components. These distinguishing properties of nano-particles are due to the different behavior of materials at the nano level. They are present in different forms in different states of matter. In the solid or liquid phase in air, they are present as aerosols; in solids or liquids they are present as a suspension and in two liquid phases they are present as an emulsion. Materials reduced to nano levels show drastic changes compared to what they show at micro-levels. For example, opaque substances such as copper become transparent at nano-level; inert and almost unreactive elements such as platinum become catalysts and stable elements such as aluminum become combustible at nano-level. Another rather astonishing feature of a nanoparticle is the increase in surface area of particles at the nano level when compared to the same mass of material in the bulk form.
The quantum effect or the quantum-size effect describes the physics of solid particles at the electronic level with great reductions in particle size. This quantum effect does not come into the picture while going from macro to micro levels. However, this becomes dominant while reaching smaller dimensions such as nano levels.
Cooling Up To The Quantum Level
On 31st January 2020, a group of researchers in Vienna, Austria, lead by Kahan Dare and Manuel Reisenbauer cooled a nano-particle into the quantum regime. The experimental findings of this group of scientists have been published in the journal Science.
We all are well-aware of the fact that properties of individual atoms or a cloud of atoms at the quantum level can be manipulated using laser light. This gives rise to macroscopic quantum states of matter such as quantum gases or Bose-einstein condensates. But this wasn’t the exciting step here; the exciting step was to extend this level of quantum control to solid-state objects. But achieving this task was not fairly easy; it had many complications and steps involved. The first step was to completely isolate the object in question from all external environmental influences and to remove all the thermal energy of the particle- by cooling it to temperature very close to absolute zero so that the quantum mechanics dominates the particle’s motion. To demonstrate this experimentally, researchers chose a glass bead approximately 1000 times smaller than a grain of sand and containing a few million atoms. To devoid the particle of thermal energy, isolation is achieved by optically trapping the particle in a tightly focused laser beam in a high vacuum. This was the main step in achieving the experimental goal as laser cooling is well-established for atoms but it does not work this way for solids.
Scientists were satisfied by their findings, as they had upgraded their experiment and now we’re not only able to remove background gas, but were also able to send in more photon for cooling. These findings have inspired scientists worldwide and provided a ray of hope for further developments in this field.
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