Nanospheres

Nanospheres are nanoscale particles with a roughly spherical shape, typically in the size range from about 1 to several hundred nanometers. They can be composed of inorganic materials such as silica or metals, or of organic polymers. The small size and spherical geometry confer a high surface area to volume ratio and enable tunable optical, mechanical, and chemical properties that are useful across a range of applications.

Nanospheres are classified by composition and structure. Solid nanospheres include polymeric particles produced by emulsion or dispersion polymerization and silica or metal spheres prepared by sol-gel or chemical reduction methods. Hollow nanospheres have a central cavity and are often made by template-assisted approaches, sacrificial cores, or selective etching of shells. Core-shell nanospheres feature a distinct core material surrounded by a shell with different chemistry, enabling decoupled properties for loading, protection, or targeting.

Key properties of nanospheres include controllable size and size distribution, surface functionality, and porosity. Optical properties are particularly important for metal nanospheres, which exhibit localized surface plasmon resonances that depend on size, shape, and the surrounding medium. Surface chemistry can be tailored through functional groups, enabling conjugation of drugs, targeting ligands, or stabilizing agents.

Applications are broad and include drug delivery and imaging in biomedicine, catalysis, coatings and paints, sensors, and energy storage or conversion. Challenges include achieving uniform size distributions, preventing aggregation, ensuring biocompatibility and safety for medical use, and scaling production while maintaining quality and regulatory compliance.