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The adaptability of field emitters in oxidizing environment is an important issue for practical applications. Herein, the effect of ozone exposure on the field emission property of molybdenum (Mo) nanowalls was studied. Results indicate that Mo nanowall cold cathode shows strong resistance to high doses of atomic oxygen exposure. The immunity of Mo nanowalls to oxidizing environment was attributed to the protection of surface amorphous layer. Mo nanowall cold cathode could be a promising candidate for electron source used in oxidizing environment.

Self-heating effect can be applied to develop gas sensors avoiding use of external heaters. We report here a prototype self-heated hydrogen gas sensor based on Pt-coated W 18 O 49 nanowire networks. Such a sensor has been shown to have promising performance, e.g., high sensitivity (able to detect down to 50 ppm of H 2 ), good selectivity (poor response to ethanol, CH 4 , CO, and C 3 H 8 ), and low power consumption of 30–60 mW at 6 V compatible to a portable device. Coaxial cable model and percolation theory are applied to explain the gas sensing effect of the Pt-coated W 18 O 49 nanowire networks.

H2 sensors able to operate at room temperature are very important for safe detection of H2 leakage. We report the large electrical response to H2 of Pt-coated WO3 (Pt−WO3) nanowire films without the need of using an external heater. More important, hydrogen sensing processes have been investigated under various conditions, including in air, vacuum filled with pure gas, and a mixture of H2 and other gases. This is carried out with both electrical and optical methods. The evidence shows that hydrogen will inject into the nanowire and create oxygen vacancy, in addition to reducing adsorbed oxygen at the surface, as is often recognized. It is experimentally demonstrated that the increase of electrical conductivity resulting from the reaction with hydrogen is hampered by coadsorption of O2, while N2 has no such effect. A model has been developed to combine these new findings to give a clearer understanding of the mechanism responsible for H2 sensing behavior.

A novel approach for preparation of europium (III)-doped yttrium oxide (Y2O3:Eu3+) nanoparticles by microemulsion–microwave heating was reported in this paper. Y2O3:Eu3+ nanoparticles were successfully obtained by microwave-heating the as-prepared particles of yttrium hydroxide and europium hydroxide, formed in a reaction between Y(NO3)3–Eu(NO3)3 and NH3·H2O in the reverse microemulsion composed of Triton X-100, n-hexanol, cyclohexane and water. Field-emission scanning electron microscopy (FE-SEM) and powder X-ray diffraction (XRD) results indicated that the resultant nanoparticles showed a narrow size distribution, small size (20–30 nm) and spherical shape. The ratios of Eu to Y in the products, determined by energy dispersive spectroscopy (EDS), were in good agreement with those of the feed. The nanoparticles emitted much strong red light at 611 nm under UV excitation, especially around 255 nm. Furthermore, this novel method required a very short heating-time and the energy consumption was much smaller compared with conventional heating ways.

A novel organic ligand, 6-paramethylaniline carbonyl 2-pyridine carboxylic acid (Hp-MAP), and the corresponding europium complex, tris(6-paramethylaniline carbonyl 2-pyridine carboxylato) europium(III) (Eu-p-MAP) have been designed and synthesized. The results showed that Eu-p-MAP was a conjugated complex, emitting remarkably strong red luminescence. The lifetimes of 5 D 0 of Eu 3+ in the complex were examined using time-resolved spectroscopic analysis; the lifetime values were 0.72±0.01 ms for 1.0×10 −5 mol l −1 Eu(p-MAP) 3 ethanol solution and 1.16±0.01 ms for solid of Eu(p-MAP) 3 , respectively. Thermogravimetric analysis showed the europium complex had good thermal stability.

Silica-based composite materials incorporated with sodium tris(pyridine dicarboxylato) europate(III), SiO2 : Na3Eu(DPA)3, where H2DPA is 2,6-pyridine dicarboxylic acid, were prepared by a sol-gel method. Photoluminescent properties of SiO2 : Na3Eu(DPA)3 composite were studied after heat treatment between room temperature and 600 °C. The strong red emission of SiO2 : Na3Eu(DPA)3 was intensified by heat-treatment under appropriate conditions. The thermal stability of Na3Eu(DPA)3·9H2O and its silica-based composite was examined. The results demonstrate that SiO2 : Na3Eu(DPA)3 composite material possesses very good thermal stability with intense visible fluorescence, and may be applied as a potential luminescent material.

A terbium(III) complex, Na 3 Tb(DPA) 3 ·9H 2 O, where H 2 DPA is 2,6-dicarboxy pyridine acid, has been synthesized and incorporated into silica gel by sol-gel method to obtain a composite material, SiO 2 :Na 3 Tb(DPA) 3 . Photoluminescent properties of SiO 2 :Na 3 Tb(DPA) 3 composite were studied after heat treatments between room temperature and 600°C. The strong green emission of the composite material was intensified by heat-treatment under appropriate conditions. The effects of the dopant concentration and heat-treatment on the luminescence for the composite material have been examined. The results indicate that SiO 2 :Na 3 Tb(DPA) 3 composite material possesses high thermal stability with intense green fluorescence, and may be applied as a potential luminescent material.

Interest in silicon field emitters for flat screen display and other applications has continued to grow very rapidly over the past several years. To obtain stable field emission from silicon emitters, diamond and DLC coatings are being considered widely. In this paper we report results from a series of experiments to assess the influence of a thin layer of amorphous diamond coating on ultra sharp single crystal silicon field emitter arrays.

We report the first observation of ultraviolet superfluorescence (SF) from oxygen vacancies in WO3−x nanowires at room temperature, and of picosecond-scale energy transfer between emission centers (oxygen vacancies) in a plane. A theoretical development from Dicke’s model leads to general formulation for a two-dimensional system, and is applied to explain the energy transfer process. The results demonstrate a possibility to generate ultrafast pulse of ultraviolet light through SF from a localized ensemble of defect states.

Tungsten trioxide (WO3) nanowires were synthesized by thermal evaporation of tungsten powder in two steps: tungsten suboxide (WO3−x) nanowires were synthesized, and then oxidized in O2 ambient and transformed into WO3 nanowires. Raman spectroscopy was applied to study the thermochromic phase transition of one-dimensional WO3 nanowires. From the temperature dependence of the characteristic mode at 33cm−1 in WO3, the phase transition temperature was determined. It was found that the phase transition of WO3 nanowires was reversible and the phase transition temperatures were even lower than that of WO3 nanopowder.