Submicrometer

Submicrometer refers to objects with dimensions below one micrometer (1 µm = 10^-6 m). In practice, submicrometer materials span roughly from tens of nanometers up to just under 1 µm. The term sits between the nanometer scale (1–999 nm) and the larger micrometer range. Submicron particles are widely studied because their small size markedly affects surface area, reactivity, and transport properties.

Size influences properties such as surface-to-volume ratio, diffusion, and optical behavior. Particles in this range exhibit pronounced Brownian motion and can form stable colloids; their optical scattering and absorption depend on size relative to the light wavelength. Typical submicron particles are encountered in aerosols, pigments, emulsions, and nanostructured films.

Synthesis and measurement: Submicron particles are produced by chemical precipitation, sol-gel, hydrothermal methods, vapor deposition, milling, and encapsulation techniques. Characterization employs transmission electron microscopy (TEM), scanning electron microscopy (SEM) for morphology and size; dynamic light scattering (DLS) or nanoparticle tracking analysis (NTA) for hydrodynamic/diffraction-limited sizes; atomic force microscopy (AFM); X-ray diffraction for crystallinity; and surface analysis methods.

Applications and considerations: They are used in coatings, pigments, electronics, catalysis, drug delivery, and filtration. In atmospheric science, submicron aerosols impact climate and air quality. Health implications include respiratory deposition and clearance; due to high surface area, submicron particles can be more reactive and may pose different toxicological profiles than larger particles. Regulation often treats particle size distribution as a key parameter.