Polyaniline/nano titanium dioxide/graphene nanoplatelet (PANI/TiO2/G) composite was synthesized by mechanochemical route. The structure and morphology of the composite were characterized by Fourier transform infrared spectra, ultraviolet-visible absorption spectra, x-ray diffraction and transmission electron microscopy. The electrochemical performances of the composite were investigated by galvanostatic charge-discharge, cyclic voltammetry, cycling stability and electrochemical impedance spectroscopy. The structure and properties of PANI/TiO2/G composite were compared with that of polyaniline/ graphene nanoplatelet (PANI/G) composite prepared under the same polymerization conditions. After comparative analysis with PANI/G, the effects of the nano titanium dioxide (TiO2) on the structural and physicochemical properties of the PANI/G have been discussed in depth. The comparison suggested that the PANI/TiO2/G composite has higher oxidation degree and lower crystallinity than PANI/G due to the addition of nano-TiO2. Morphology studies showed that PANI and nano-TiO2 particles were both observed on the bent and flat surfaces of graphene nanoplatelet in the PANI/TiO2/G composite. The electrochemical tests showed that the PANI/TiO2/G composite displayed a higher electrochemical activity with specific capacitance of 516 F/g (3 mA/cm2) and better cycle stability than PANI/G.

Nanoerythrocyte-shaped ytterbium orthovanadate (YbVO4) with substantially uniform size have been successfully synthesized by a simple and facile trisodium citrate-assisted hydrothermal method. The erythrocyte-shaped YbVO4 nanocrystals with self-assembled spherical and biconcave structure have a diameter of ∼500 nm, which were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy and photoluminescence. The luminescent properties of erbium ion-doped ytterbium orthovanadate nanocrystals with different morphologies by different complexing agents were different in the relative intensity under identical measurement conditions, which exhibited the interesting morphology-dependent optical properties. The different energy transfer mechanisms and photoluminescence intensities might be the result of the greatly reduced defect centers.

Uniform ytterbium ion and erbium ion codoped gadolinium oxyfluoride (GdOF: Yb3+, Er3+) hollow nanospheres of 100-nm diameter were synthesized via the nanoscale Kirkendall approach, using colloidal nanospheres of ytterbium ion and erbium ion codoped gadolinium hydroxide [Gd(OH)3: Yb3+, Er3+] as sacrificial templates and titanium tetrafluoride as fluorine source under hydrothermal condition. The shell thickness of the as-synthesized GdOF: Yb3+, Er3+ hollow nanospheres can be facilely tuned from 31 to 13 nm by controlling reaction temperature and reaction time. The upconversion emission color could be adjusted from red to yellow to green when the host lattices variedfrom gadolinium (III) oxide to gadolinium oxyfluoride to gadolinium fluoride. Furthermore, the formation mechanism of the hollow GdOF: Yb3+, Er3+ nanospheres was found to depend on the fluorine source.

A potential order-of-magnitude increase in Hall-Petch (H-P)-based strength level for nanoscale grain-size structures is an important enabler of electronic thin film material design applications. Dislocation pileups of smaller lengths in such thin film materials are blocked in a screw orientation at the through-thickness grain boundaries of relatively larger grains. For fully nanopolycrystalline materials, both strength and strain rate sensitivity measurements exhibit complementary H-P reciprocal square root of grain size dependencies. An additional increase in strength level is predicted for transition from a pileup to a single dislocation loop expanding against the grain boundary obstacle. In opposition, disordered grain boundaries are responsible for a reduced H-P stress intensity, kε. And at the limiting high stresses reached at lower-limiting nanoscale grain sizes, reversed H-P dependences are obtained both for the strength and strain rate sensitivity.