Classification of nanoparticles

Formation and development of Nanochemistry

The term “nano” refers to the metric prefix 10^-9. It means one billionth of something. “Nano” can be recognized to any unit of measure. For example, you may report a very small mass in nanograms or the amount of liquid in one cell in terms of nanoliters.

So, what is nanoscience? Nanoscience is the study of structures and materials on the scale of nanometers. To give you an idea of how long a nanometer is, this printed page is about 75,000 nanometers thick. When structures are made small enough—in the nanometer size range—they can take on interesting and useful properties.

With Nanoscience being the study of phenomena and manipulation of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scaleand Nanotechnology being a device or machine, product or process, based upon individuals or multiple integrated nanoscale components, then What is Nanochemistry?

In its broad test terms, the defining feature of Nanochemistry is the utilization of synthetic chemistry to make nanoscale building blocks of different size and shape, composition and surface structure, charge and functionality. These building blocks may be useful in their own right or in a self-assembly construction process, spontaneous, directed by templates or guided by chemically or lithographically defined surface patterns. They may form architectures that perform an intelligent function and portend a particular use.

Nanoparticle isa structural unit of new substances and materials. Itcan be definedas particles with at least one of their three - dimensional sizes in the range of 1– ∼100 nm(1 nm=10^-9 m). This is between the size of atoms or molecules and bulk materials. Within this size range, they can usually consist of 10–10,000 atoms. First, let us clarify the terms. Various terms that describe the nanosized particles have been adopted in the literature. The term is sometimes based on just the size, sometimes based on the physical property of the particles, and sometimes based on the shape of the particles. The term nanoparticle is obviously the most widely used one, and it is safe to say that this term encompasses most of the nanosized particles regardless of their physical property, size, and shape. Also, nanoparticles can be in either an amorphous or crystalline state. Nanoparticle refers to both states. When the crystalline state is considered, the term nanocrystal is preferred.

The terms cluster or nanocluster are also frequently used. Some of the literature uses these words as equivalent to or as replacements for nanoparticle. They are sometimes used to refer even to the aggregates of colloidal particles. This seems not to be a problem, as long as they are meant to represent the particles of the nanometer range. However, cluster is originally adopted to define the size range of atomic aggregates whose optical transition is not dependent on the number of atoms.As we will discuss later, the opticalproperties of nanoparticles are strongly dependent on their size. Hence, once the optical properties show variation in changes in size, the term cluster had better not be used to replace the term nanoparticle.

Classification of nanoparticles

The US Environmental Agency has classified current nanomaterials into four types, namely:

1. Carbon base materials: with spherical, ellipsoidal or tubular forms. Its fundamental properties are its reduced weight and its greater hardness, elasticity and electrical conductivity.

2. Metallic base materials: they can be quantum dots (quantum dots or transistors of a single electron) or nanoparticles of gold, silver42 or of reactive metals like titanium dioxide, among others.

3. Dendrimers: nanometric polymers constructed as a tree in which the branches grow from others and so on; The endings of each branch chain can be designed to execute specific chemical functions (a useful property for catalytic processes).

4. Composites: combine certain nanoparticles with others or with larger materials. The case of nanostructured clays is an example of extended use.

Typical examples of various nanoparticles:

Based on the materials, nanoparticles can be composed of semiconductive, pure metallic, metal oxide, organic, polymeric, and biological components as we can see in the following table:

Table No. 1. Various nanoparticles