Single Particle Extinction and Scattering (SPES) is a technique in physics that is used to characterise micro and nanoparticles suspended in a fluid through two independent parameters, the diameter and the effective refractive index.[1][2]

A laser generates a gaussian beam which focuses inside a flow cell. A particle that passes through the focal region generates an interference in the beam, which is collected with a sensor. Through this signal it is possible to derive the real part and the imaginary part of the forward scattering field from each particle.

The technique was developed to measure aerosols in air[3] and particles in liquid.[4]


  1. ^ Sanvito, Tiziano; Bigini, Paolo; Cavanna, Maria V.; Fiordaliso, Fabio; Violatto, Martina B.; Talamini, Laura; Salmona, Mario; Milani, Paolo; Potenza, Marco A. C. (November 2017). "Single particle extinction and scattering optical method unveils in real time the influence of the blood components on polymeric nanoparticles". Nanomedicine: Nanotechnology, Biology and Medicine. 13 (8): 2597–2603. doi:10.1016/j.nano.2017.07.008. PMID 28756089.
  2. ^ Dawson, K. A.; Milani, P.; Castagnola, V.; Boselli, L.; Cella, C.; Araújo, J. M. de; Monopoli, M.; Cai, Q.; Sanvito, T. (2017-02-23). "Detecting the shape of anisotropic gold nanoparticles in dispersion with single particle extinction and scattering". Nanoscale. 9 (8): 2778–2784. doi:10.1039/C6NR08977A. PMID 28155930.
  3. ^ Mariani, Federico; Bernardoni, Vera; Riccobono, Francesco; Vecchi, Roberta; Valli, Gianluigi; Sanvito, Tiziano; Paroli, Bruno; Pullia, Alberto; Potenza, Marco A. C. (2017). "Single Particle Extinction and Scattering allows novel optical characterization of aerosols". Journal of Nanoparticle Research. 19 (8): 291. Bibcode:2017JNR....19..291M. doi:10.1007/s11051-017-3995-3. S2CID 139469999.
  4. ^ Milani, P.; Lenardi, C.; Paroli, B.; Cella, C.; Argentiere, S.; Sanvito, T.; Potenza, M. a. C. (2015-12-15). "Single particle optical extinction and scattering allows real time quantitative characterization of drug payload and degradation of polymeric nanoparticles". Scientific Reports. 5: 18228. Bibcode:2015NatSR...518228P. doi:10.1038/srep18228. PMC 4678328. PMID 26667064.