Radiation induced color centers in multicomponent glasses

Manipulation of Gold Nanoparticles inside Transparent Materials

“…The peaks at 245, 306, 430, and 620 nm can be assigned to E' centers (E' = Si), which include an electron trapped in an sp 3 orbital of silicon at the site of an oxygen vacancy, a hole trapped by an oxygen vacancy that neighbors alkali-metal ions, and nonbridging oxygen holes HC1 (a hole trapped by an SiO 4 polyhedron that contain one bridging oxygen and three nonbridging oxygen atoms) and HC2 (a hole trapped by an SiO 4 polyhedron that contain two nonbridging oxygen atoms). [7] The extinction spectra of the Au 2 O 3 -doped glasses, which were annealed at various temperatures for 30 min after irradiation, are also plotted in Figure 2. When the annealing temperature is below 300 8C, the extinction (300-800 nm) intensities induced by irradiation decrease as the annealing temperature increases, and completely disappear when the temperatures reaches 300 8C.…”

Metallic nanoparticles grown in the core of femtosecond laser micromachined waveguides

“…In this case, the irradiation resulted in an increase of the absorbance for the visible region of the spectrum (a ¼ 1.6 cm À1 ) due to the formation of color center and reduction of silver ions. 10,11,18 A small plasmon band was observed only after a heat treatment, preformed at 400 C for 1 h. The effect of color centers caused by the irradiation using the MHz laser can be ruled out, since the absorbance due to the plasmon band overcomes any absorption caused by the color center.…”

“…19 These secondary electrons and holes are trapped by defects in the glass matrix producing new electronic configurations that are understood as color centers. 18,20 In the case of femtosecond lasers in transparent glasses, free electrons are generated due to nonlinear optical interactions, as photoionization and avalanche ionization. 7,8 The former directly promotes electrons from the valence to the conduction band by multiphoton absorption, while avalanche ionization requires seed electrons already in the conduction band, which keep absorbing energy from the photons until it has enough energy to transfer an electron from the valence to the conduction band by collision.…”

Modified Au-Based Nanomaterials Studied by Surface Plasmon Resonance Spectroscopy

“…21 These color centers are attributed to the formation of electron-hole pairs which, in turn, can yield the creation of defects, causing high absorbance in the UV and visible region. According to the literature, 17,199,200 radiation induces defects on glasses associated with either oxygen excess or oxygen defect in the network. For soda-lime glass, the most typically reported defects are non-bridging oxygen hole center (NBOHC: ≡Si − O * ), E center (≡Si * ), peroxy radical (POR: ≡Si − O − O * ) and trapped electron (TE), where the symbol "≡" denotes three bonds with other oxygens in the glass network and the " * " represents an unpaired electron.…”

“…For soda-lime glass, the most typically reported defects are non-bridging oxygen hole center (NBOHC: ≡Si − O * ), E center (≡Si * ), peroxy radical (POR: ≡Si − O − O * ) and trapped electron (TE), where the symbol "≡" denotes three bonds with other oxygens in the glass network and the " * " represents an unpaired electron. 17,199 A proper identification of the type of color center can be obtained by optical absorption spectroscopy, since each of these defects induces absorption bands at different wavelengths. 21, 188 Figure 6.4 shows the result of an irradiated soda-lime glass (referenced to non-irradiated soda-lime glass in order to obtain the net irradiation induced absorption) measured one month after the irradiation.…”