Dual pH-dependent fluorescence peaks from a semiconductor quantum dot (QD) and a pH-dependent fluorescent dye can be measured by irradiating with a single wavelength light, and the pH can be estimated from the ratio of the fluorescent intensity of the two peaks. In this work, ratiometric pH sensing was achieved in an aqueous environment by a fluorescent CdSe/ZnS QD appended with a pH-sensitive organic dye, based on fluorescence resonance energy transfer (FRET). By functionalizing the CdSe/ZnS QD with 5-(and 6)-carboxynaphthofluorescein succinimidyl ester as a pH-dependent fluorescent dye, we succeeded in fabricating sensitive nanocomplexes with a linear response to a broad range of physiological pH levels (7.5 -9.5) when excited at 450 nm. We found that a purification process is important for increasing the high-fluorescence intensity ratio of a ratiometric fluorescence pH-sensor, and the fluorescence intensity ratio was improved up to 1.0 at pH 8.0 after the purification process to remove unreacted CdSe/ZnS QDs even though the fluorescence of the dye could not be observed without the purification process. The fluorescence intensity ratio corresponds to the fluorescence intensity of the dye, and this fluorescent dye exhibited pH-dependent fluorescence intensity changes. These facts indicate that the fluorescence intensity ratio linearly increased with increasing pH value of the buffer solution containing the QD and the dye. The FRET efficiencies changed from 0.3 (pH 7.5) to 6.2 (pH 9.5).

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The instability of Eu complexes against ultraviolet (UV) light irradiation is an important problem to solve before they can be practically applied in white light-emitting diodes. A novel technique of encapsulating tris(2-thenoyltrifluoroacetonato)(1,10-phenanthroline)europium(III) [Eu(TTA)3phen] was investigated using high-pressure annealing (solvothermal process) as a final process in the sol–gel synthesis. The photoluminescence and excitation spectra of encapsulated Eu(TTA)3phen samples synthesized by solvothermal and conventional annealing processes were almost the same. A half brightness time of 589 min was achieved while irradiating with UV light of 360 nm and 5 mW/cm2 by optimization of ammonia concentration and annealing temperature. The longest half brightness time was longer than that of encapsulated Eu(TTA)3phen synthesized by conventional thermal treatment. One possible reason for this result is that the chemical reaction of the sol–gel based glass network occurs more efficiently with high-pressure annealing. As a result, a high encapsulating efficiency was achieved owing to the small amount of organic component in the sol–gel derived glass network.

We studied the effects of adding various amounts of Sb to Sn-3.5Ag-0.5Bi-6.0In-0.8Cu (SABIC) solder in terms of the phase transformation temperature for the b-Sn and g(InSn 4 ) transformation, mechanical properties such as strength and ductility, and thermal fatigue properties under thermal cycling (-40°C/175°C). With increasing amounts of added Sb, the temperature at which the phase transformation occurred increased. At 150 and 175°C, breaking elongation values of solders as a measure of ductility became the highest for an Sb content of 0.5 wt.%. As the phase transformation temperature increased, deformations of the solder joints after the thermal fatigue test were suppressed. The thermal fatigue properties were best at an Sb content of 1.0 wt.%, at which the phase transformation temperature was greater than 175°C.It is considered that raising the phase transformation temperature to a temperature higher than the maximum operating temperature of electronic devices should be the topmost priority to improve crack extension behavior.

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