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Europium-doped cubic Gd 2 O 3 :Eu 3+ nanoparticles containing various activator content in the range of 5–15 wt% were synthesized by a liquid-phase reaction method to investigate the influence of Eu 3+ loading on the optical properties of phosphors by using XRD, TEM, BET, spectrometer and fluorometer. The size of Gd 2 O 3 :Eu 3+ powders was in the range 21–41 nm. The phosphors showed an initial increase in luminescence and then a subsequent decrease with further doping (above 10 wt%). The decay time was reduced with increasing Eu loading; however, it decreased significantly above the 10% Eu doping. From spectroscopic studies, the Eu 3+ doping ion distribution was uniform and homogeneous up to the 10 wt% loading because no concentration quenching effect was observed. However, further Eu 3+ doping above 10 wt% reduced the luminescence due to the concentration quenching effect, as deduced from the shortening of the decay time.

We report on conducting polyaniline (PANI) films doped with a thermally stable polymer dopant, linear ladder-type sulfonated polyphenylsilsesquioxane (S-PPSQ). The PANI/S-PPSQ films exhibited high-temperature stable electrical conductivity. With a heat treatment at 120 °C, the electrical conductivity of conventional PANI films doped with the molecular dopant camphorsulfuric acid (CSA) rapidly decreased to half of its initial value, while that of PANI/S-PPSQ films were relatively unaffected. Moreover, PANI/S-PPSQ films with high electrical conductivity exhibited unusual negative temperature coefficient of resistance (TCR) values above room temperature, in contrast to conventional PANI/CSA films that exhibited positive TCR values. By using a solution blend of PANI/S-PPSQ and PANI/CSA with negative and positive TCR values, respectively, we successfully demonstrated control of TCR behavior. Therefore, PANI/S-PPSQ materials are very promising for organic electronic applications.