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Tuning upconversion (UPC) luminescence using external stimuli and fields, as well as chemical reactions, is expected to lead to novel and efficient optical sensors. Herein, highly tunable UPC luminescence was achieved through a host--guest chemistry approach. Specifically, interlayerion exchange reactions reversibly tuned the emission intensity and green-red color of Er/Yb-codoped A2La2Ti3O10 layered perovsldte, where A corresponds to proton and alkali metal ions, enabling the visualization of host--guest interactions and reactions. [ABSTRACT FROM AUTHOR]

This paper presents an aqueous route to size-controlled and doped CeO 2nanoparticles using the Ce-oleate complex as a chemically modified precursor. In this synthesis, a hydrolytic condensation of Ce-oleate complex by aqueous ammonia solution at room temperature leads to 2.2 nm sized CeO 2nanocrystals. These products are dispersible in nonpolar solvents owing to the hydrophobic nature of the surface oleate ligand. Moreover, the size of the nanocrystals is controllable up to 5.2 nm by subsequent hydrothermal treatment at 200 °C. The proposed method can be extended for the synthesis of rare earth-doped CeO 2nanocrystals as well. The Gd 3+doped CeO 2nanocrystals synthesized by the proposed method exhibit a spherical shape (size ∼ 3.2 nm) and have a designed chemical composition by energy dispersive X-ray analysis, X-ray diffraction, Raman scattering, and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) walled channels filled by sulfate ions exhibit an optimized proton conductivity, which is higher than the proton conductivity of all other forms of GO. The sulphate ion increases the water absorbing capacity and hydrogen bond reformation process in GO. [ABSTRACT FROM AUTHOR]

Understanding the chemical and physical properties of metal/graphene oxide (M/GO) interfaces is important when GOis used in electronic and electrochemical devices because the metal layer must be firmly attached to GO. Here, permeation of metal from the surface into GO paper bulk at the M/GO interface was observed at room temperature for metals such as Cu, Ag, Ni, Au, and Pt. Cu, Ag, and Ni quickly permeated GO as ions into the bulk under humid conditions. At first, these metals changed to hydrated ions as a result of redox reactions (with reduction of GO) at the surface, and then permeated the interlayers. Au and Pt were observed to permeate GO as atoms into the GO bulk at room temperature, although the permeation rates were low. These surprising results are considered to be due to the presence of many defects and/or edges with oxygenated groups in the GO paper. [ABSTRACT FROM AUTHOR]

Single-phase nanoparticles of brookite, a less common polymorph of TiO2than rutile and anatase, were successfully synthesized using a water-soluble titanium–glycolate complex as the precursor and nanoparticle growth by an oleate-modified hydrothermal growth method. The synthesized particles were approximately 30 nm in size, had high crystallinity, and were highly dispersible in water. The morphology of the synthesized particles was a pseudocube surrounded mainly with four {210} and two {001} faces, accompanying truncation with small {111} facets. It is considered that the preferential absorption of oleate molecules on {210} and {001} faces resulted in the pseudocubic crystal shape. [ABSTRACT FROM AUTHOR]

We have investigated an in-plane electrical transport in an individual titania nanosheet, which forms a lepidocrocite structure with a few atomic layer thickness. The conductivity in the titania nanosheet varied five orders for the change of the relative humidity from 45% to 95%. The drastic change in the conductivity is due to a sensitive response with respect to water molecules adsorbed on the surface of the two-dimensional nanosheet. The results may open an avenue for nanodevices built from various oxide nanosheets. [ABSTRACT FROM AUTHOR]