At first it was very simple. In 2000, President Clinton signed the “National Nanotechnology Initiative” document. The definition of nanotechnology is the creation of technologies and research at the atomic, molecular and macromolecular levels between about 1 and 100 nm to understand the fundamental basis of phenomena and properties of materials at the nanoscale, and the creation and use of structures, equipment and systems with new properties and functions determined by their size.
In 2003, the UK government asked the Royal Society6 and the Royal Academy of Engineering for their views on the need to develop nanotechnology and to assess the benefits and challenges that its development may cause. This report, entitled Nanoscience and nanotechnologies: opportunities and uncertainties, appeared in July 2004 and, to our knowledge, for the first time provided separate definitions of nanoscience and nanotechnology.
Nanoscience is the study of phenomena and objects at the atomic, molecular and macromolecular levels whose characteristics differ significantly from the properties of their macroanalogs.
Nanotechnology is the design, characterization, production and application of structures, devices and systems whose properties are determined by their shape and size at the nanometer level.
Thus, the term “nanotechnology” refers to a set of technological techniques that allow the creation and/or manipulation of nano-objects. All that remains is to define nanoobjects. But this turns out to be not so simple, so most of the article is devoted to this definition.
To begin with, here is a formal definition that is most widely used nowadays.
Nanoobjects (nanoparticles) are objects (particles) with characteristic size of 1-100 nanometers, at least in one dimension.
All seems well and understandable, it is not clear only why such a rigid definition of the lower and upper limits of 1 and 100 nm is given? It seems to be chosen voluntaristically, especially suspicious is the assignment of the upper limit. Why not 70 or 150 nm? After all, given all the variety of nanoobjects in nature, the boundaries of the nanoparticle size scale can and should be significantly blurred. And in general, it is impossible to draw any exact boundaries in nature – some objects flow smoothly into others, and this happens in a certain interval, not at a point.
Before we talk about boundaries, let’s try to understand what physical meaning is contained in the concept of “nano-object”, why it should be distinguished by a separate definition?
As noted above, only at the end of the 20th century the understanding began to appear (or rather, to be confirmed in minds) that the nanoscale interval of matter structure has its own features, that at this level the substance has other properties which are not manifested in the macrocosm. It is very difficult to translate some English terms into Russian, but in English there is the term “bulk material”, which can be roughly translated as “bulk matter”, “bulk matter”, “solid medium”. So, some properties of “bulk materials” can begin to change when the size of its constituent particles reaches a certain size. In this case, it is said that there is a transition to the nanostate of matter, nanomaterials.
And this happens because as the particle size decreases, the fraction of atoms located on its surface and their contribution to the object’s properties become significant and grow with further decreasing in size.
But why does increasing the fraction of surface atoms significantly affect the properties of particles?
So-called surface phenomena have been known for a long time – these are surface tension, capillary phenomena, surface activity, wetting, adsorption, adhesion, etc. The totality of these phenomena is due to the fact that the interaction forces between the particles composing a body are not compensated on its surface. In other words, atoms on the surface (of a crystal or a liquid – it doesn’t matter) are in special conditions. For example, in crystals, the forces forcing them to be in the nodes of the crystal lattice act on them only from below. Therefore, properties of these “surface” atoms differ from properties of the same atoms in the volume.
Since the number of surface atoms increases sharply in nanoobjects, their contribution to the properties of the nanoobject becomes decisive and grows with further reduction of the object size. This is one of the reasons for the manifestation of new properties at the nanoscale.
Another reason for the discussed change of properties is the fact that at this dimensional level the laws of quantum mechanics begin to work, i.e. the level of nanoscale is the level of transition, exactly transition, from the reign of classical mechanics to the reign of quantum mechanics. And as is well known, the most unpredictable thing is the transition states.
By the middle of the twentieth century, people had learned how to work with a mass of atoms, as well as with a single atom.
Subsequently, it became obvious that a “little bunch of atoms” was something different, not quite like a mass of atoms or a single atom.
Scientists and technologists probably first came face to face with this problem in semiconductor physics. In their pursuit of miniaturization they reached such sizes of particles (several tens of nanometers or less), at which their optical and electronic properties began to differ sharply from those of “ordinary” particles. It was then that it finally became clear that the scale of “nanoscale” is a special field, different from the field of existence of macroparticles or solid media.
Therefore, in the above definitions of nanoscience and nanotechnologies, the most essential point is the indication that “real nano” begins with the appearance of new properties of substances related to transition to these scales and differing from the properties of bulk materials. That is, the most essential and most important quality of nanoparticles, their main difference from micro- and macroparticles, is the appearance of their fundamentally new properties, which are not manifested at other sizes.
