2,5-Diphenyloxazole, primary

The light, hv2, from F2 is of longer wavelength than hvx from F and is more efficiently detected by a PMT. Two widely used primary and secondary fluors are 2,5-diphenyloxazole (PPO) with an emission maximum of 380 nm and l,4-bis-2-(5-phenyloxazolyl)benzene (POPOP) with an emission maximum of 420 nm. 

Excited solvent molecules transfer their energy to other solvent molecules, and eventually to a primary fluor molecule (Fx), which then emits a photon (hiq) and decays to its ground state (Equations 3-7 and 3-8). A widely used fluor is 2,5-diphenyloxazole (PPO). 

Figure 10.12. Typical primary and secondary scintillators, (a) Primary 2,5-diphenyloxazole (PPO). (b) Secondary 1,4-bis-2-(5-phenyloxazolyl)-benrene...

Beilstein Handbook Reference) BRN 0157021 2,5-Diphenyloxazole DPO (scintillator) EINECS 202-181-3 NSC 24856 Oxazole, 2,5-diphenyl- PPG (scintillator) Tritosol USAF EK-6775 DPO. Primary floor used in scintillation counters or in wavelength shifters. Solid mp = 74 bp" 360" d = 1.0940 Xm" 205, 220, 302 nm (MeOH) insoluble in H2O, soluble in EtOH, EtzO, CHCI3. . /. DuPont de Nemours Inc. Rente Mfg. Spectrum Chem. Manufacturing. 

The samples were absorbed in 9 ml of Carbo-Sorb and collected in low potassium glass scintillation vials. To this were added 13 ml of homogeneous blend toluene based scintillator (Permafluor V ). Permafluor V contains 91% PPO (2,5 diphenyloxazole) as the primary scintillator and 9% POPOP (l,4-bis-2(5-phenyloxazolyl)-benzene) as the secondary scintillator. ... 

The solvent used is usually an aromatic hydrocarbon (toluene or xylene are most common), or sometimes dioxan. The scintillator is a polyaromatic fluorophore, such as 295-Diphenyloxazole (PPO). In the past it has sometimes been necessary to add a secondary scintillator to which the energy is transferred from the primary scintillator. Secondary scintillators, of which 2,2 -(l,4-Phenylene)bis-[5-phenyloxazole] (POPOP) is the most well known, are somewhat larger molecules, with more delocalisation than the primary scintillators they emit at longer wavelengths at which photomultiplier tube sensitivity is greater. 

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