Nanoparticles

Nanoparticles are particles with dimensions in the nanoscale, typically 1-100 nm in at least one dimension. Their small size yields large surface area to volume ratio and often quantum effects, leading to novel optical, electronic, and chemical properties compared with bulk materials.

Common types include metallic (gold, silver), metal oxides (titanium dioxide, zinc oxide), ceramic, polymeric, carbon-based (fullerenes, carbon nanotubes), and quantum dots. Synthesis approaches encompass bottom-up methods like chemical reduction, sol-gel, and hydrothermal processes, as well as top-down methods such as milling or lithography. Surface modification and functionalization are used to tailor solubility, stability, biocompatibility, and targeting.

Characterization and properties are assessed with techniques such as electron microscopy (TEM/SEM), dynamic light scattering for size distribution, X-ray diffraction for crystallinity, and spectroscopy for optical properties. Applications span medicine (drug delivery, imaging), electronics and optoelectronics, catalysis, energy storage, sensing, and coatings.

Safety and regulation discuss potential toxicity due to small size, capacity to cross biological barriers, environmental fate, and concerns about aggregation and release. Regulation varies by region; risk assessment, lifecycle analysis, and standardized testing are ongoing areas of development.