Optical characterization of luminescent silicon nanocrystals embedded in glass matrices Interstellar dust in nebulae and in the Diffuse Interstellar Medium (DISM) of galaxies contains a component which exhibits efficient visible near infrared luminescence ranging from 600 to 1000 nm known as Extended Red Emission (ERE). The ERE which was first detected by Cohen et al.1 in the spectrum of the Red Rectangle nebula more than 30 years ago generally appears as a broad structureless emission band (120 to 210 nm wide) peaking between 600 and 850 nm (see Sec. 2.1.1.1.). Interestingly the bandwidth of the ERE in creases with the position of the maximum of the band (Fig. 2.2). The ERE has been observed in many different dusty environments that are illuminated by ultraviolet photons. Therefore this visible near infrared emission is probably due to the interaction of ultraviolet photons with dust grains through photoluminescence (PL). The maximal photon conversion efficiency of the PL process leading to ERE approaches 10% (Fig. 2.3). The ERE carrier is a component of interstellar dust that must consist of the most abundant refractive elements in the cosmos (C O Si Fe and Mg) and once formed the carriers must survive under a wide range of as trophysical conditions. Silicon nanocrystals (nc Si) are discussed as possible carriers of the ERE.2 3 Indeed nc Si can emit intense PL in a wide spectral range from 600 to 1100 nm. ...