PPO Scintillator, 100 g

PPO, IUPAC preferred name 2,5-Diphenyl-1,3-oxazole, has an aromatic ring structure fundamental for fluorescent properties.

PPO is well-suited for use as a scintillator in various radiation detection applications. It exhibits a high photoluminescence quantum yield, indicating its efficiency in converting the energy absorbed from ionizing radiation into emitted light. This high efficiency is a desirable characteristic for a scintillator, as it leads to a stronger signal that is easier to detect.

When excited by radiation, PPO fluoresces as a violet color with an excitation wavelength of ~ 303 nm. Its emission wavelength is ~360 nm, which falls within the ultraviolet (UV) range of the electromagnetic spectrum, however, these peaks can vary depending on the solvent used. An important property of PPO is its ability to act as a wavelength shifter. This means that it can absorb light of shorter wavelengths and re-emit light at longer wavelengths.

This characteristic is particularly useful in scintillation detectors because the primary scintillation light produced by the solvent often lies in the UV region, and wavelength shifters like PPO can convert this light to wavelengths that are more efficiently detected by photomultiplier tubes, which typically have higher sensitivity in the visible or near-UV range. However, since PPO's primary emission is still in the UV range, it may be used in conjunction with secondary wavelength shifters for further optimization for liquid scintillation counting. PPO is often paired with secondary scintillator Bis-MSB which acts as a wavelength shifter to re-emit light in the ultraviolet (UV) or visible ranges which is essential for detecting with PMT based detectors.

The molecular formula of PPO is C₁₅H₁₁NO, a melting point of 70 - 72°C and a fluorescence maximum of 362 nm.