Description:

Title: Nanoparticle-enhanced Photosensors for UV Light Detection

Speaker: Dr. Stephen Magill, Argonne National Laboratory
 

Abstract: Detection of UV photons is becoming increasingly necessary with the use of noble gases and liquids in elementary particle experiments.  Cerenkov light in crystals and glasses, scintillation light in neutrino, dark matter, and rare decay experiments all require sensitivity to UV photons.  Sensor materials are needed that can directly detect UV photons and/or absorb UV photons and re-emit light in the visible range measurable by existing photosensors.  Quantum confinement in nanoparticles increases in the band gap, resulting in sensitivity to low wavelengths; and discrete energy states at the band gap edges produce tunable re-emitted light at (visible) wavelengths dependent on the nanoparticle size.  Nanoparticle coatings used as wavelength shifters can extend the range of existing photosensors into the UV.  Mixed with an appropriate glue or grease, nanoparticles may also be used to extract fast scintillation light from crystals.  Also, with a thin nanoparticle layer, UV-sensitive photodiodes can be achieved in a very compact package.  Initial tests of the wavelength-shifting properties of several nanoparticles are presented here that indicate by placing a film of nanoparticles in front of a standard visible-wavelength detecting photosensor, the response of the sensor is significantly enhanced at wavelengths < 320 nm.