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Phonon Coupling Properties of Non Bridging Oxygen Hole Centers at a Silica Surface Probed by Site-Selective Luminescence Excitation
No full textVibrational properties of the surface-nonbridging oxygen in silica nanoparticles
No full textBy studying the site-selective luminescence spectra of oxidized silica nanoparticles we identify the electronic
and the vibrational lines associated with the surface nonbridging oxygen, Si-O•. This defect emits a
zero-phonon line inhomogeneously distributed around 2.0 eV with full width at half maximum of 0.04 eV,
weakly coupled with the local Si-O• stretching mode whose frequency is measured to be 920 cm−1. These findings are different from those of the well-characterized defect in the bulk silica thus evidencing structural peculiarities of the surface defect that is characterized by a nearly unperturbed nonbridging oxygen and of the
nanoparticles that induce a narrower inhomogeneous broadening of the electronic transition
Luminescenza risolta in tempo del non bridging oxygen hole center in silice: proprietà di volume e di superficie
No full textTime-resolved luminescence of non-bridging oxygen hole centre in silica: Bulk and surface properties
No full text
Luminescence of the surface nonbridging oxygen hole center: Spectral and decay properties
No full textWe investigated the red luminescence in a porous film of silica nanoparticles, originating from surface nonbridging oxygen hole centers. The excitation spectrum was measured from 1.8 to 8.0 eV by a tunable laser system and a synchrotron radiation source; this spectrum evidences a peak at 2.0 eV, nearly overlapping with
the emission, and an ultraviolet broadband with peaks at 4.8 and 6.0 eV. The emission is characterized by a spectrum with two subbands split by 0.07 eV, its decay occurs with lifetime longer than 30 microsec and undergoes
a thermal quenching by a factor aboout 2 with increasing temperature from 10 to 290 K. The optical characteristics of surface and bulk centers are discussed on the basis of the reported experimental results and quantum
chemical calculations
Zero phonon line associated with Non Bridging Oxygen Hole Center in silica: comparison between bulk and surface properties
No full textLuminescence properties of non bridging oxygen hole centers at a silica surface
No full textTwo variants of the surface-nonbridging oxygen hole center, („Si–O)3Si–O and („Si–O)2(H–O)Si–O
,
stabilized in porous films of silica nano-particles were investigated by time resolved luminescence
excited in the visible and UV spectral range by a tunable laser system. Both defects emit a photoluminescence
around 2.0 eV with an excitation spectrum evidencing two maxima at 2.0 and 4.8 eV, this emission
decreases by a factor 2 on increasing the temperature from 8 up to 290 K. However, the different local
structure influences the emission lineshape, the quantum yield and the deca
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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