Nanoparticle, ultrafine unit with dimensions measured in nanometres (nm; 1 nm = 10−9 metre). In 2008 the International Organization for Standardization (ISO) defined a nanoparticle as a discrete nano-object where all three Cartesian dimensions are less than 100 nm.
Nanoparticles exist in the natural world and are also created as a result of human activities. Because of their submicroscopic size, they have unique material characteristics, and manufactured nanoparticles may find practical applications in a variety of areas, including medicine, engineering, catalysis, and environmental remediation.
CLASSIFICATION:
Classification based on organic and inorganic nanoparticles: the first group includes dendrimers, liposomes, and polymeric nanoparticles, while the latter includes fullerenes, quantum dots, and gold nanoparticles.
Classification on the basis of composition: carbon-based, ceramic, semiconducting, or polymeric. On the basis of hardness: nanoparticles can be classified as hard (e.g., titania [titanium dioxide], silica [silica dioxide] particles, and fullerenes) or as soft (e.g., liposomes, vesicles, and nanodroplets).
There are three major physical properties of nanoparticles
they are highly mobile in the free state
they have enormous specific surface areas
they may exhibit what are known as quantum effects.
Thus, nanoparticles have a vast range of compositions, depending on the use or the product.
Nanoparticle-based technologies
In general, nanoparticle-based technologies centre on opportunities for improving the efficiency, sustainability, and speed of already-existing processes. That is possible because, relative to the materials used traditionally for industrial processes (e.g., industrial catalysis), nanoparticle-based technologies use less material, a large proportion of which is already in a more “reactive” state.
Polymers: nanoclays have been incorporated into polymers to improve their strength and impact resistance.
Food packaging: to control the ambient atmosphere around food, keeping it fresh and safe from microbial contamination.
Flame retardants: in the event of a serious fire, products with nanoclays and hydroxide nanoparticles were associated with fewer emissions of harmful fumes than products containing certain other types of additives.
Batteries and supercapacitors: The ability to engineer nanocomposite materials to have very high internal surface areas for storing electrical charge in the form of small ions or electrons has made them especially valuable for use in batteries and supercapacitors.
Nanoceramics: combining the unique functional (e.g., electrical, magnetic, or mechanical) properties of a nanocomposite material with the properties of ceramics materials.
Light control: potential to produce white light at significantly reduced costs.
Application in Medicine: A) Magnetic nanoparticles have been used to replace radioactive technetium for tracking the spread of cancer along lymph nodes. B) Nanoparticles can be designed to enhance fluorescent imaging or to enhance images from positron emission tomography (PET) or ultrasound. C) The development of nanoparticles to aid in the delivery of a drug to the brain via inhalation holds considerable promise for the treatment of neurological disorders such as Parkinson disease, Alzheimer disease, and multiple sclerosis.
There are several mechanisms by which nanoparticles are believed to affect the environment negatively.
that the mobility and sorptive capacity of nanoparticles (natural or human-made) make them potent vectors (carriers) in the transport of chemical pollutants (e.g., phosphorus from sewage and agriculture), particularly in rivers and lakes.
that some nanoparticles are able to reduce the functioning of (and may even disrupt or kill) naturally occurring microbial communities, as well as microbial communities that are employed in industrial processes (e.g., those that are used in sanitation processes, including sewage treatment).
