A nanoparticle is a microscopic particle whose size is measured in nanometres. Nanoparticles are thus larger than angstroms (Å), but smaller than micrometres. At the small end of the size range, nanoparticles are often referred to as clusters (cluster (physics)).
Metal, dielectric, and semiconductor nanoparticles have been formed, as well as hybrid structures (e.g., core-shell nanoparticles). Nanospheres, nanorods, and nanocups are just a few of the shapes that have been grown. Semiconductor quantum dots and nanocrystals are types of nanoparticles.
Nanoparticle characterization is necessary to establish understanding and control of nanoparticle synthesis and applications. Characterization is done by using a variety of different techniques, mainly drawn from materials science. Common techniques are electron microscopy, Atomic force microscopy, x-ray photoelectron spectroscopy, fourier transform infra red spectroscopy (FTIR).
Nanoparticle research is currently an area of intense scientific research, due to a wide variety of potential applications in biomedical, optical, and electronic fields.
In biomedical applications nanoparticles are used as drug carriers or imaging agents. For this purpose the nanoparticle may have a hollow structure providing a central reservoir that can be filled with anticancer drugs, detection agents, or chemicals, known as reporters, that can signal if a drug is having a therapeutic effect. The surface of a nanoparticle can also be adorned with various targeting agents, such as antibodies, drugs, imaging agents, and reporters. Most nanoparticles are constructed to be small enough to pass through blood capillaries and enter cells.