UV visible spectrophotometer has shown unique application value in particle size and morphology analysis. Based on the absorption characteristics of substances for specific wavelengths of light, it can indirectly reflect the size distribution and morphology characteristics of nanoparticles.

particle size analysis

The particle size of nanoparticles is closely related to their absorption spectrum peak positions. Taking gold nanoparticles as an example, the surface plasmon resonance absorption peak shifts towards longer wavelengths as the particle size increases. When the particle size increases from 10nm to 50nm, the absorption peak may shift from 520nm to above 550nm. By measuring the absorption peak wavelength and combining it with Mie scattering theory or empirical formulas, the average particle size of particles can be inferred. For example, a research team used a UV visible spectrophotometer to detect the absorption peak of silver nanoparticles and found that when the peak position moved from 400nm to 420nm, the corresponding particle size increased from 20nm to 30nm, which was highly consistent with the transmission electron microscopy results.

Shape correlation

The particle morphology has a significant impact on the peak width and shape of the absorption spectrum. The absorption peak of spherical particles is usually symmetrical and narrow, while rod-shaped or sheet-like particles may experience peak broadening or splitting due to anisotropy. For example, gold nanorods exhibit absorption peaks around 520nm and 700nm in longitudinal and transverse surface plasmon resonance modes, respectively. The aspect ratio can be estimated by the peak intensity ratio. A certain experiment showed that when the aspect ratio of gold nanorods increased from 2:1 to 4:1, the intensity ratio of the longitudinal peak to the transverse peak increased from 0.5 to 1.2, intuitively reflecting the morphological changes.

technical advantage