Non-toxic liquid scintillators with high light output based on phenyl-substituted siloxanes

• Performances as liquid scintillator of different liquid siloxanes were studied.
• Fluorescence analysis was performed in order to investigate excimer formation.
• Solvent-solute energy transfer was studied by means of fluorescence spectroscopy.
• Scintillation response was linked with spectrofluorimetric analysis.
• 1,1,5,5-Tetraphenyl- 1,3,3,5-tetramethyl-trisiloxane showed the best performances.

The work describes the development of a new class of liquid scintillators based on polysiloxane liquid compounds. These materials are characterized by low toxicity, chemical inertness, very low volatility and low flammability, allowing their use without concerns even at high temperatures in vacuum. In this view different polysiloxane based liquids have been tested, with variable content and distribution of phenyl lateral substituents and added with suitable dyes, namely 2,5-diphenyloxazole (PPO) and Lumogen Violet (LV). Absorption and fluorescence spectroscopy have been used in order to study the emission feature of the various compounds and to investigate the spectral matching between siloxane solvents and dissolved primary dyes. Scintillation efficiency towards 60Co and 137Cs gamma rays, relative to commercial liquid scintillator (EJ-309), has been measured and the results have been related to the energy transfer and energy migration mechanism from monomer and excimer forming sites in liquid siloxanes.