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Abstract: Fluorescence intensity ratios (FIRs) of the 640 nm and 602 nm emissions from Sm3+ were recorded at various temperatures T to identify the temperature increases ΔT associated with laser‐induced local heating of Ag nanoparticles. The FIRs increased as intensities of the excitation beam from a 532‐nm continuous‐wave laser increased. Estimated T of the irradiated region increased to as high as 586°C when at laser irradiation of 1.5 W on the surface containing Ag nanoparticles. Local heating due to the surface plasmon resonance of Ag nanoparticles is a main reason for the ΔT that eventually leads to precipitation of PbS quantum dots in glasses. [ABSTRACT FROM AUTHOR]

The influence of Nd3+ ions was investigated on the precipitation and optical properties of PbS quantum dots ( QDs) inside silicate glasses. The diameters of the PbS QDs decreased as the concentration of Nd3+ in the glass increased as evidenced by blue shifts in the absorption and photoluminescence spectra. Electron energy loss spectroscopy shows that Nd3+ ions exist preferentially inside the PbS nanocrystals rather than in the glass matrix. We postulate that Nd-O clusters are preserved during heat treatment and serve as nucleation sites for PbS crystals. No change in the local bonding scheme of the Nd3+ ions was observed following heat treatment. [ABSTRACT FROM AUTHOR]

This article reports the effect of Ag+ ion-exchange on the precipitation of PbS quantum dots ( QDs) in silicate glasses. The glasses were subjected to ion-exchange in AgNO3 salt melts at 260°C for 60 s. Ag nanoparticles ( NPs) and PbS QDs precipitated after heat treatment at temperatures of 440°C-460°C for 10 h. Photoluminescence wavelength λPL of PbS QDs was longer (~1525 ≤ λPL ≤ ~1580 nm) in Ag+ ion-exchanged regions than in Ag+-free regions (~1030 ≤ λPL ≤ ~1200 nm). Average diameter D of PbS QDs estimated by calculation and TEM images was larger in Ag+ ion-exchanged regions (~5.2 ≤ D ≤ ~5.5 nm) than in Ag+-free regions (~2.4 ≤ D ≤ ~3.3 nm). Ag NPs that formed during heat treatment provided the sites for heterogeneous nucleation of PbS QDs and promoted the precipitation of PbS QDs in glasses. [ABSTRACT FROM AUTHOR]

Abstract: Precipitation of PbS quantum dots (QDs) in silicate glasses controlled by Ag+ ion diffusion was investigated. Ag+ ions penetrated ~0.5μm into the glass when the glass was immersed in the AgNO3 solution at 80°C. Ag nano-particles (NPs) and PbS QDs were formed after heat-treatment at temperatures of 420–460°C for 10h. PbS QDs in Ag+-diffused regions photoluminesced at longer wavelengths than did those in Ag+-free regions. This indicates that PbS QDs thus formed in regions containing Ag NPs were larger than those in Ag+-free regions and this size difference was confirmed from the transmission electron microscope images. PbS QDs can grow at temperature as low as 420°C in Ag+-diffused regions and this implies that PbS QDs form preferentially using Ag NPs as nucleating agents. [Copyright &y& Elsevier]

PbS and PbS/CdS core/shell colloidal quantum dots (QDs) were mixed with As 2 S 3 glass powders to prepare solid composite materials. PbS QDs showed an absorption band centered at a wavelength of λ = 1478 nm and a photoluminescence (PL) band centered at λ = 1547 nm. PbS/CdS core/shell QDs had higher PL intensity than did bare PbS QDs. Solid composites made by mixing QDs and As 2 S 3 glass powders showed clear PL bands at λ = 1385 nm. Optical fibers of As 2 S 3 glass can be prepared from these composite materials if appropriate scale-up technology is realized. [ABSTRACT FROM AUTHOR]

PbS QDs of ~ 5nm diameter were precipitated in glasses containing Ag nanoparticles after 3 min of 1.5-W continuous-wave laser illumination at λ = 532 nm. Photoluminescence spectra of the PbS QDs recorded in the 1.3~1.6 μm wavelength region revealed conversion of photon energy to thermal energy by surface plasmon resonance. Laser-assisted local heating around Ag NPs can provide a new method to control the spatial distribution of QDs in glasses. [ABSTRACT FROM AUTHOR]

Precipitation of PbS quantum dots (QDs) in glasses was controlled by thermal diffusion of Ag+ ions from Ag paste at a temperature of 320°C. After subsequent heat treatment at 420–450°C, PbS QDs formed in the near-surface regions where the silver paste was applied. After the glasses were heat-treated at 440 or 450°C, PbS QDs were larger in Ag-affected surface regions than in Ag-free glasses. PbS QDs grew in Ag-affected regions when they were heat-treated at 420 or 430°C. Ag+ ions penetrated ~25μm from the glass surface after thermal diffusion of Ag+ ions and subsequent heat treatment at 430°C. Thermal diffusion of Ag+ ions from Ag paste is a viable method to control the precipitation and spatial distribution of PbS QDs in glasses. [ABSTRACT FROM AUTHOR]

Abstract: Electric-field assisted solid-state diffusion of Ag+ was used to control precipitation of PbS quantum dots (QDs) inside glasses. Precipitation of PbS QDs was confirmed by transmission electron microscopy images and photoluminescence (PL) spectra. PL bands moved to longer wavelengths as applied voltage increased under the same subsequent heat-treatment, and as heat-treatment temperature increased under the same voltage. PbS QDs can preferentially precipitate at low temperature and photo-luminesce at longer wavelengths in Ag+-affected regions than in unaffected regions. Ag nanoparticles were also formed inside affected regions after thermal treatment, and provided nucleation sites for PbS QDs. Precipitation of PbS QDs and their spatial distribution in glasses can be controlled by electric field-assisted Ag+ migration. [Copyright &y& Elsevier]

Abstract: Optical properties of PbS quantum dots (QDs) precipitated inside the oxide glass matrix were investigated. Photoluminescence (PL) from the PbS QDs showed peak wavelengths located at 1170–1680nm with widths of 150–550nm. Radii of QDs in glasses were 2.3–4.7nm depending upon the thermal treatment. Peak wavelengths of PL bands shifted as much as 70nm as the temperatures and excitation irradiances increased. Calculated effective local temperatures indicated that these shifts of PL spectra were associated with local heating induced by the temperatures and laser beam. [Copyright &y& Elsevier]

Formation of PbS QDs in the glasses containing a small amount of lead oxide was examined. Oversaturation of sulfur only was sufficient to promote the formation of PbS QDs in the glasses. Upon thermal treatment, absorption of PbS QDs was tuned from 824nm to 2213nm. Infrared photoluminescence, especially, mid-infrared photoluminescence from PbS QDs was observed in the range of 1008nm to 2182nm. Ostwald ripening of PbS QDs occurred when the heat-treatment temperature was 530°C or 540°C, and led to the decrease in the absorption coefficients and splitting of the photoluminescence bands. [ABSTRACT FROM AUTHOR]

Abstract: The size and spatial distribution of PbS QDs in glasses need to be controlled in order to achieve desired optical characteristics. This paper reports on the use of several rare-earth oxides such as Ho2O3, Er2O3, and La2O3 to control the size of PbS QDs in silicate glasses. Additions of rare-earth oxides result in blue shifts of the absorption bands from 1344nm to 930nm, and the wavelengths of PL bands can be controlled between 1421nm and 1035nm. Additions of up to 0.8mol% of Ho2O3 decreased the diameters of PbS QDs from 4.82nm to 3.02nm. The same tendencies were found for both Er2O3 and La2O3 additions, although the size of PbS QDs increased as the ionic radius of rare-earth ions increased. It is proposed that clusters of RE–O bonds act as nucleating agents for the precipitation of PbS QDs. [Copyright &y& Elsevier]

Abstract: Heat-treatment was used to precipitate PbS quantum dots (QDs) in silicate glasses doped with different amounts of Ag2O, and the influence of Ag2O on QDs was investigated. Under given heat-treatment conditions, the absorption coefficients and photoluminescence intensities of PbS QDs increased with the addition of Ag2O. Ag clusters formed by thermal treatment nucleated formation of PbS QDs in glasses. [Copyright &y& Elsevier]