'''Single Particle Extinction and Scattering (SPES)''' is a technique in [[physics]] that is used to characterise micro and [[nanoparticle|nanoparticles]] in suspensionsuspended in a fluid through two independent parameters, the diameter and the [[refractive index|effective refractive index]].<ref>{{Cite web |url=https://www.ncbi.nlm.nih.gov/pubmed/28756089 |title=Single particle extinction and scattering optical method unveils in real time the influence of the blood components on polymeric nanoparticles |last=Sanvito |first=Tiziano |last2=Bigini |first2=Paolo |date=November 2017 |website=Nanomedicine: Nanotechnology, Biology, and Medicine |publisher=[[National Center for Biotechnology Information]], [[U.S. National Library of Medicine]] |pages=2597–2603 |doi=10.1016/j.nano.2017.07.008 |pmid=28756089 |access-date=16 June 2019 |last3=Cavanna |first3=Maria V. |last4=Fiordaliso |first4=Fabio |last5=Violatto |first5=Martina B. |last6=Talamini |first6=Laura |last7=Salmona |first7=Mario |last8=Milani |first8=Paolo |last9=Potenza |first9=Marco A. C.}}</ref><ref>{{Cite web |url=https://pubs.rsc.org/en/content/articlelanding/2017/nr/c6nr08977a |title=Detecting the shape of anisotropic gold nanoparticles in dispersion with single particle extinction and scattering |last=Dawson |first=K. A. |last2=Milani |first2=P. |date=2017-02-23 |website=Nanoscale |publisher=[[Royal Society of Chemistry]] |___location=United Kingdom |pages=2778–2784 |language=en |publication-place=United Kingdom |doi=10.1039/C6NR08977A |access-date=2019-06-16 |last3=Castagnola |first3=V. |last4=Boselli |first4=L. |last5=Cella |first5=C. |last6=Araújo |first6=J. M. de |last7=Monopoli |first7=M. |last8=Cai |first8=Q. |last9=Sanvito |first9=T.}}</ref>
A [[laser]] generategenerates a [[gaussian beam]] which focuses inside a flow cell. A particle whothat passes inthrough the focal region generates an interference in the beam, which is collected with a sensor. TroughThrough this signal it is possible to derive the real part and the immaginaryimaginary part of the forward scattering field, from each single particle.
The technique was developed to measure aerosols in air<ref>https://doi.org/10.1007/s11051-017-3995-3</ref> and particles in liquid.<ref>{{Cite web |url=https://www.nature.com/articles/srep18228 |title=Single particle optical extinction and scattering allows real time quantitative characterization of drug payload and degradation of polymeric nanoparticles |last=Milani |first=P. |last2=Lenardi |first2=C. |date=2015-12-15 |website=Scientific Reports |publisher=[[Nature (journal)]] |pages=18228 |doi=10.1038/srep18228 |access-date=2019-06-16 |last3=Paroli |first3=B. |last4=Cella |first4=C. |last5=Argentiere |first5=S. |last6=Sanvito |first6=T. |last7=Potenza |first7=M. a. C.}}</ref>
