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Lead selenide (PbSe) quantum dots (QDs) doped with Sr 2 + were precipitated in silicate glasses. The absorption and photoluminescence (PL) bands of the glasses blue-shifted as SrO concentration increased. These changes resulted mainly because Sr incorporation increased the band gap of PbSe nanocrystals. After heat treatment at 520 °C for 10 h, mean QD diameters were similar before and after the addition of SrO: ~ 7.2 nm with 0% SrO and ~ 6.9 nm with 10 mol% SrO. However, these two glasses show the absorption bands at 1743 nm and 1246 nm, and PL bands at 1803 and 1370 nm, respectively. These large shifts are due to the increase in the band gap through the formation of Pb 1 − x Sr x Se mixed-type QDs. One typical chemical composition of QDs formed in a glass with 10 mol% SrO after heat treatment at 520 °C for 10 h is Pb 0.89 Sr 0.11 Se with a band gap of ~ 0.58 eV. [ABSTRACT FROM AUTHOR]

Infrared photoluminescence (PL) properties of Sn-modified PbSe quantum dots (QDs) in silicate glass were investigated. The QDs' sizes were controlled by changing the heat treatment temperatures. The longest absorption peak from Sn-modified PbSe QDs was centered at 2590 nm, and the PL band extended to 2650 nm. X-ray diffraction peaks indicated that the PbSe QDs formed in the glass matrix although low Sn content resulted in no obvious difference between PbSe QDs and Sn-modified PbSe QDs. Sn was found in QDs that proves the incorporation of Sn into PbSe QDs. The proposed composition of the Sn-modified PbSe QDs was Pb 0.92 Sn 0.08 Se with a band gap of ~ 0.13 eV; the small amount of Sn changed the energy structure of QDs, narrowed the band-gap, and increased the PL emission wavelength. [ABSTRACT FROM AUTHOR]

Lead selenide quantum dots (QDs) were precipitated in germanosilicate glasses to investigate the effect of GeO 2 content on the precipitation and optical properties. The absorption and photoluminescence (PL) bands red-shifted strongly as GeO 2 concentration increased. After heat-treatment at 470 °C for 10 h, the first excitonic absorption bands red-shifted from 801 nm to 2593 nm as GeO 2 content increased from 0 to 40 mol%, and thus PL at 2619 nm was achieved. The corresponding average QD diameters were 2.48–12.54 nm. The precipitation of large PbSe QDs resulted from the enhancement of diffusion with the increase of GeO 2 concentration, and is the main reason for these red-shifts. [ABSTRACT FROM AUTHOR]

Abstract Magic angle spinning nuclear magnetic resonance (MAS NMR) experiments on network formers of 29Si, 27Al and 11B were performed to determine the network connectivity of the quenched glasses. The viscosity and electrical resistivity of alkali-free boro-aluminosilicate glasses were measured at high temperatures, and this temperature dependence of both the two properties were well described by Arrhenius relation. The Mauro-Yue-Ellison-Gupta-Allan (MYEGA) equation was employed to study the viscosity and fragility of glass melts from glass transition temperature to melting temperature. With increasing in the RO substitution for the Al 2 O 3 from 13.5 to 19.5 mol%, the melting temperature of glasses decreased from 1630.4 to 1532.6 °C, the fragility index m increased from 22.6 to 24.0 and the resistivity at 1600 °C decreased from 52.3 to 28.9 Ω·cm. It was mainly corresponding to the depolymerization of network connectivity. The NMR results showed that the number of Q4 units decreased from 27.4 to 21.1% and the value of the non-briding oxygen per tetrahedral cation (NBO/T) increased from 0.482 to 0.744. The four-fold coordinated aluminum always predominated in Al groups, and the relative fraction of [BO 4 ] in B groups increased from 5.1% to 16.4%. It cannot be ignored that most of boron kept in [BO 3 ] group even when the ratio of RO/(B 2 O 3 + Al 2 O 3) > 1, which is large different from that in alkali aluminoborosilicate glasses. It is associated with the higher field strength of alkali-earth cations who prefer to form NBO rather than [BO 4 ]. Highlights • Network connectivity of aluminoborosilicate glass were studied by NMR. • Resistivity of aluminoborosilicate glass at high temperature range • Relationship between the viscosity, resistivity and glass structure [ABSTRACT FROM AUTHOR]