Blue-emitting SiO2:Eu 2+ compound has been successfully synthesized and characterized. The PL intensity of SiO2:Eu .ଶ ଶା compound is about 24 times higher than that of the O-defective SiO2 compound (without activators) which emits blue light. The valence state of Eu ions as the nature of the highly enhanced blue emission in resulting material, is determined to be Eu 2+ using reference materials (EuCl2 and EuCl3) in XPS measurements. The Eu 2+ -activator ions occupied in the interstitial sites of SiO2 matrix, are confirmed by FT-IR, XPS, and 29 Si MAS-NMR spectroscopy. Even though the void spaces formed structurally in both α-quartz and α-cristobalite can accommodate Eu 2+ ions (ionic radius = 1.25 Å at CN = 8), SiO2:Eu 2+ compound fired at 1300℃ under hydrogen atmosphere is destined to be deficient in O or Si atoms, indicating the formation of the wider void spaces in SiO2 crystal lattice. A sputtered depth profile of SiO2-related compounds obtained by time-of-flight secondary ion mass spectrometry (TOF-SIMS) corroborates the O-defective SiO2 induced by hydrogen. In particular, the interatomic potentials depending on the interstitial positions of Eu atom in α-cristobalite and α-quartz are calculated based on Lennard-Jones potential and coulomb potential; for α-cristobalite the minimum potential value is -51.47 eV, for α-quartz 221.8 eV, which reveals that the Eu 2+ -activator ions more preferably enter the interstitial sites of αcristobalite than those of α-quartz. Thanks to the stable Eu 2+ -activator ions enclosed by Si-O linkages, SiO2:Eu .ଶ ଶା compound emits blue light and its PL emission intensity is about 24 times higher than that of the O-defective SiO2 compound. This phosphor material could be a platform for modeling a new phosphor and application in the solidstate lighting field.

The potential electrochromic application of graphene-based nanohybrids is hampered by the challenges in interfacing the electrochromic nanoparticles with graphene at atomic scale and in fabricating their thin film on the substrate through a scalable method. In an effort to overcome these challenges, we demonstrate a highly dispersible graphene-based molybdenum oxide nanohybrid (mRGO-MoO3-x) for flexible electrochromic application. With only a squeeze pipet, mRGO-MoO3-x could be deposited with a high coverage on various substrates through a scalable equipment-free Langmuir-Blodgett film deposition method. By taking advantage of high transmittance benefited from its remarkable thinness, the mRGO-MoO3-x Langmuir-Blodgett film shows a superior reversible electrochromic property with high coloration efficiency on both hard and flexible substrates.

A highly stable and scalable photosynthetic reaction center–mercapto reduced graphene oxide system has been developed for solar energy transduction.