Low temperature and decay lifetime photoluminescence of Eu and Tb nanoparticles embedded into SiO2

In the present work, we have studied the photoluminescence (PL) and decay lifetime of Tb and Eu nanoparticles (NPs) at low temperatures. The NPs were obtained by ion implantation into a SiO2 matrix. Concerning the PL emission of Tb NPs (from 370 to 700 nm), the shape does not change with the sample temperature and the PL yield has a maximum at 12 K and decreases with increasing temperature, reaching a minimum at 300 K. The PL lifetime is wavelength independent and remains almost constant at a value of 1.5 ms. Regarding Eu NPs emission, two spectral regions were identified, one with narrow emission bands (from 570 to 750 nm) and the other with a broad emission band (from 400 to 550 nm). Both PL regions show a minimum yield at 12 K, and next it rises with increasing temperatures, reaching the maximum at around 100 K. Then, the PL yields start to decrease, reaching at 300 K a value similar to the one obtained at 12 K. For the Eu NPs PL lifetime, two different results were obtained. The long wavelength spectral region shows a lifetime of the order of 1.0 ms independent of the temperature. Conversely, the short wavelength one is strongly temperature dependent, being of the order of several milliseconds for temperatures lower than 100 K down to 0.05 ms at 300 K.