Nanotechnology deals with various structures of matter having dimensions of the order of a billionth of a meter (nanometer). Since the advent of nanotechnology, researchers have realized that certain materials could exhibit different properties based on their size and shape.
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Nanomaterials possess specific properties that make them different from that of bulk materials, including large surface area, the ability to tailor their functionalities for varying applications, and high surface energy.
In this article, the different types of nanoparticles, a common category of nanomaterials, are discussed.
What are the Different Types of Nanoparticles?
Nanoparticles can be classified according to their size, morphology, physical and chemical properties. Often, the classification of these nanomaterials determines their function.
Predominantly, carbon-based nanoparticles are split into carbon nanotubes (CNTs) and fullerenes. The use of these nanomaterials tends to focus on structural reinforcement as they are 100 times stronger than steel.
CNTs can be classified into single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). CNTs are unique in a way as they are thermally conductive along the length and non-conductive across the tube.
Fullerenes are carbon allotropes with a hollow cage structure of sixty or more carbon atoms. The structure of C60 is called Buckminster fullerenes, and resembles a hollow football.
The carbon units in these structures have a pentagonal and hexagonal arrangement. Such carbon-based nanoparticles have commercial applications due to their electrical conductivity, structure, high strength, and electron affinity.
These nanomaterials are inorganic solids composed of oxides, carbides, carbonates and phosphates. Ceramic nanoparticles have high heat resistance and chemical inertness and have applications in photocatalysis, photodegradation of dyes, drug delivery, and biological imaging.
By controlling their specific characteristics like size, surface area, porosity, surface-to-volume ratio, these nanomaterials perform as good drug delivery agents.
Ceramic nanoparticles have been used effectively as a drug delivery system for several diseases like bacterial infections, glaucoma, and cancer.
Metal nanoparticles are prepared from metal precursors, and can be synthesized by chemical, electrochemical, or photochemical methods. In chemical methods, the metal nanoparticles are obtained by reducing the metal-ion precursors in solution with chemical reducing agents. The resultant nanomaterials can adsorb small molecules and have high surface energy.
Metal nanoparticles are utilized across several research fields, including detection and imaging of biomolecules and in environmental and bioanalytical applications. For example, gold nanoparticles are used to coat the sample before SEM analysis to enhance SEM and produce high-quality electron microscopy images.
Semiconductor nanoparticles have properties like those of metals and non-metals, and are found in the periodic table in groups II-VI, III-V or IV-VI. These nanoparticles have wide bandgaps, which upon tuning show different properties. Some examples of semiconductor nanoparticles are GaN, GaP, InP, InAs from group III-V, ZnO, ZnS, CdS, CdSe, CdTe are II-VI semiconductors and silicon and germanium are from group IV.
Semiconductor nanoparticles are applied to photocatalysis, electronics devices, nanophotonics and water splitting applications.
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Polymeric nanoparticles are organic-based nanoparticles. Depending upon the preparation method, polymeric nanoparticles have structures shaped like nanocapsules or nanospheres.
A nanosphere nanoparticle has a matrix-like structure, whereas nanocapsules have core-shell morphology. In nanosphere polymeric nanoparticles, the active compounds and the polymer are uniformly dispersed while in nanocapsule nanoparticles, the active compounds are confined and surrounded by a polymer shell.
Some of the advantages of polymeric nanoparticles include controlled release, protection of drug molecules as they travel within the internal and external environment, the ability to combine therapy and imaging, and specific targeting.
Polymeric nanoparticles have applications in drug delivery and diagnostics. Drug delivery systems with polymeric nanoparticles are also highly biodegradable and biocompatible.
Lipid nanoparticles are generally spherical with a diameter ranging from 10 to 100nm. Their structure consists of a solid core made of lipid and a matrix containing soluble lipophilic molecules, and the external core is stabilized by surfactants and emulsifiers.
Lipid nanoparticles have applications in the biomedical field as drug carriers and RNA release in cancer therapy.
Impact of Nanoparticles on the Future of Nanotechnology
The different types of nanoparticles have been a significant driver behind the expansion of nanotechnologies, establishing life-saving innovations in drug delivery, as well as improved efficiency in a myriad of processes.
As the field of nanotechnology advances, the construction and synthesis of functional nanoparticles for applications across the pharmaceutical, energy generation, and chemical engineering sectors will continue.
References and Further Reading
Khan, I., Saeed, K. and Khan, I., (2019) Nanoparticles: Properties, applications and toxicities. Arabian Journal of Chemistry, 12(7), pp.908-931. https://www.sciencedirect.com/science/article/pii/S1878535217300990
Thomas, S., Harshita, B., Mishra, P. and Talegaonkar, S., (2015). Ceramic Nanoparticles: Fabrication Methods and Applications in Drug Delivery. Current Pharmaceutical Design, 21(42), pp.6165-6188. https://doi.org/10.2174/1381612821666151027153246
Crucho, C. and Barros, M., (2017) Polymeric nanoparticles: A study on the preparation variables and characterization methods. Materials Science and Engineering: C, 80, pp.771-784. https://doi.org/10.1016/j.msec.2017.06.004