Properties and Applications of Silica Nanoparticles

1. Properties and Applications of Silica Nanoparticles Silicon dioxide nanoparticles, also known as silica nanoparticles, are promising for biological applications owing to their excellent biocompatibility, low toxicity, thermal stability, facile synthetic route, and large-scale synthetic availability. The particle size, crystallinity, porosity, and shape can be precisely manipulated, enabling the silica nanoparticles for various applications. Moreover, numerous available surface modifications of silica nanoparticles permit their control of surface chemistry to achieve drug loading, good dispensability, and site-specific targeting. These properties, if combined and developed appropriately, make silica nanoparticles a platform for biomedical imaging, detecting, therapeutic delivery, monitoring, and ablative therapies. With the design of diverse dopants, surface functional groups, and assembly techniques, multifunctional nanoparticles can be developed with theranostic applications. Silica nanoparticles have also widely applied in other areas such as energy source, electronic, sensor, and catalysis purposes. Properties Silica nanoparticles are divided into P-type and S-type based on their structure. The former nanoparticles are characterized by numerous nanopores featuring a pore rate of 0.61 ml/g. The latter nanoparticles have a relatively smaller surface area. In contrast to the S-type, the P-type silica nanoparticles manifest a higher ultraviolet reflectivity. The silica nanoparticles are fabricated via the condensation of silanes to form nanoparticles composed of an amorphous network of silicon and oxygen. The nanoparticles are monodisperse with high stability, and the nanoparticles have narrow size distributions. The density of the nanoparticles is approximately 2 g/cm-3 slightly affected by the degree of condensation. The refractive index is determined to be 1.43. The nanoparticles are well-dispersed in polar solvents like water and ethanol. The nanoparticles can be converted into hydrophobic ones through coupling different silanes to the nanoparticle surface.