Hi Serena
I know a few projects aimed at measuring particles with low cost sensors
http://luftdaten.info/feinstaubsensor-bauen/
https://ourairquality.org/
I have not try any of them but I’m currently working on the development of a Open Air Quality Monitor (MACA) in
Argentina. For particles we are experimenting with the Shinyei PPDS42 but you can find laser based sensors as Plantower or SDS011 that look better.
www.monitorabierto.wikidot.com
And here you can find a lot of general info about of low cost sensors, monitors and calibrations
www.snuffle.org
http://www.aqmd.gov/aq-spec
I hope this helps
Saludos
Nano