Temperature dependence of O2 singlet photoluminescence in silica nanoparticles

Abstract The near infrared singlet emission and photoluminescence lifetime of O 2 molecules embedded in silica nanoparticles are studied from room temperature down to 10 K. The area of the photoluminescence band under infrared excitation decreases for temperature above 100 K and the lifetime is shortened. These observations provide evidence of a thermally activated relaxation channel with activation energy of about 40 meV. This relaxation mechanism adds to the already known temperature independent electronic-to-vibrational coupling involving high energy vibrational modes of the host matrix or its impurities. The thermally activated process is suggested to consist in the breakage of the O 2 molecule weak bonds with walls of the matrix interstices with ensuing molecular motion and collisional exchange of energy.