nanosphere

A nanosphere is a nanoparticle with a roughly spherical morphology, typically 1 to 100 nanometers in diameter. Nanospheres can be composed of metals (such as gold or silver), metal oxides (silica, iron oxide), or semiconductors (cadmium selenide, zinc oxide). They are used across fields because their spherical geometry and nanoscale size confer unique physical and chemical properties, including tunable optical features and high surface area.

Synthesis commonly uses colloidal chemistry. Gold nanospheres are often made by citrate reduction of chloroauric acid, yielding relatively uniform particles; silica spheres can be formed by the Stöber process; seed-mediated growth allows precise size control. Surface ligands, polymers, or biomolecules can be attached to the particle surface to tailor solubility, biocompatibility, and targeting.

Key properties include size- and shape-dependent optical responses; metal nanospheres exhibit localized surface plasmon resonance that affects absorption and scattering spectra; silica and oxide nanospheres are chemically robust and easy to functionalize; magnetic nanospheres enable magnetic separation and MRI contrast. Stability and aggregation are common considerations, and surface chemistry largely governs biocompatibility and toxicity.

Applications span biomedical imaging, drug delivery, photothermal therapy, diagnostics, catalysis, and environmental sensing. In research, nanospheres serve as carriers for therapeutics, as contrast agents, and as building blocks for more complex nanostructures. Related materials include nanoshells, nanospheres of other compositions, and quantum dots, which extend the range of optical and catalytic properties. Safety and regulatory considerations apply for biomedical uses, depending on core material and surface coating.