Yongbo Chen

Linear ethanol sensing of SnO2 nanorods with extremely high sensitivity

The SnO2 nanorods with a diameter down to 3nm are synthesized through a hydrothermal route and their sensing properties are investigated. The small size is confirmed by the results of x-ray diffraction, transmission electron microscope and Raman scattering spectrum. The sensitivity is up to 83.8 as the nanorod sensor is exposed to 300ppm ethanol vapor in air. Moreover, the linear dependence of the sensitivity on the ethanol concentration is observed for each of the 20 sensors. Compared with the measured results of 80–180nm tin oxide particles, such linear dependence is related to the small size effect.

Synthesis and ethanol sensing characteristics of single crystalline SnO2 nanorods

In a basic water-alcohol mixing solution without any other toxically organic solvents, the single crystalline SnO2 nanorods with diameters of 4–15 nm and lengths of 100–200 nm were synthesized using SnCl4 as a precursor. The sensors fabricated from the nanorods exhibited the sensitivity of 31.4 for 300 ppm of ethanol. Both the response and recovery time are short, around 1 s. Moreover, a linear dependence of the sensitivity on the ethanol concentration was observed. These behaviors were well explained by considering the high surface-to-volume ratio of the nanorods.

Microwave absorption properties of the ZnO nanowire-polyester composites

We report on the microwave response properties of the ZnO nanowire-polyester composites fabricated into a planar plate with the area of 180×180u2009mm2 and the thickness of about 1 mm. Strong microwave absorption has been observed in X band and the maximum absorption is enhanced as the concentration of the nanowires increases in the composites. Both the low complex permittivity and the low dissipation of the pure nanowires demonstrate the pure nanowires are low-loss materials for microwave absorption in X band. The strong absorption is related to interfacial multipoles at the interface between the polyester and the ZnO nanowires, a high surface-to-volume ratio and a similar shape of the nanowires to antenna.

Synthesis and ethanol sensing properties of ZnSnO3 nanowires

ZnSnO3 nanowires in mass production have been synthesized via thermal evaporation of ZnO, SnO, and graphite mixture powders. X-ray powder diffraction results show that these nanowires are of ZnSnO3 crystal structure. These nanowires have diameters ranging from 20 to 90 nm and lengths of several ten micrometers. Gas sensors fabricated from these ZnSnO3 nanowires show a very high sensitivity to ethanol gas and the sensitivity is up to about 42 against 500 ppm ethanol gas at the operating temperature of 300u2009°C. Both the response and the recovery time are about 1 s. Mass production and good sensitivities of the nanowires indicate their potential applications in sensor technology at the industry level.

Synthesis and ethanol sensing properties of indium-doped tin oxide nanowires

Indium-doped tin oxide (ITO) nanowires are synthesized in mass production via thermal evaporation of In2O3, SnO, and graphite mixture powders. The transverse sizes of these nanowires range from 70 to 150 nm, and the lengths are up to several tens of micrometers. The three elements In, Sn, and O uniformly distribute over the whole nanowire, respectively. The atomic concentration of In is about 5%. The gas sensors realized from these ITO nanowires are very sensitive to ethanol gas, and the sensitivity is about 40 against 200ppm ethanol at the work temperature of 400°C. Both the response and recovery time are shorter than 2s. These results suggest that ITO nanowires are good candidates for fabricating gas sensors.

Extremely stable field emission from AlZnO nanowire arrays

Extremely stable electric field emission from well-aligned AlZnO nanowire arrays is realized. The emission current density is up to 6.5mA∕cm2, and no current saturation is observed. The turn-on field is 2.9V∕μm as d (distance between the nanowire emitters and anode) is 0.64mm. After aging for two days, the emission current is extremely stable with the fluctuations of±0.4%. The high stability arises from the high crystal quality with few surface states of the nanowires and the in situ fabrication of cathodes. The field emission behaviors are in excellent agreement with Fowler–Nordheim theory, and the relationship between the field enhancement factor β and d follows a universal equation. Our results imply that AlZnO nanowire arrays are promising candidates for field emission displays.

2.0W diode-pumped Er:Yb:YAl3(BO3)4 laser at 1.5–1.6μm

An efficient and high output power laser has been realized for an Er:Yb:YAl3(BO3)4 crystal end pumped by a 970nm diode laser. Under the absorbed pump power of 15.5W, quasi-continuous-wave output power of 2.0W at 1.5–1.6μm has been obtained in a hemispherical cavity. The laser had an absorbed pump threshold power of 4.7W and a slope efficiency of 21%. The influence of the laser output power and output coupler transmission on the output laser spectra has also been investigated.

Electronic transport characteristics through individual ZnSnO3 nanowires

Composite ZnSnO3 nanowires are synthesized via a one-step thermal evaporation method. The nanowires are of core-shell structures with the presence of grain boundary and out-of-phase boundaries. Transport through individual nanowires shows nonlinear current-voltage (I-V) characteristics in the range of the voltage from −3to3V. Such a behavior can be attributed to the presence of the barrier at the grain boundary, and the effective barrier height is estimated to be about 0.22eV by analyzing the I-V curves at various temperatures. The current at −3V jumps from 0.12to6.0μA within 30s at 300K as exposed to UV illumination. Such jump can be well explained in terms of effective barrier height and depletion width.

Electrical transport through individual nanowires with transverse grain boundaries

V2O4∙0.25H2O nanowires are synthesized via hydrothermal route. The nanowires are of metastable phase, and transverse grain boundaries are observed in their microstructures. Transport through individual V2O4∙0.25H2O nanowires shows nonlinear current-voltage (I-V) characteristics in the bias range of −3to3V. The resistance rapidly decreases from 2.54to0.5MΩ as the bias is raised from 0to1V. Such behaviors can be attributed to the presence of the barrier at the transverse grain boundary. By analyzing the I-V curves at various temperatures, the effective barrier height is estimated to be about 0.13eV. Our results provide important information about how the microstructure mismatch affects the electrical properties.

Large-Scale Multifunctional Electrochromic-Energy Storage Device Based on Tungsten Trioxide Monohydrate Nanosheets and Prussian White

A high-performance electrochromic-energy storage device (EESD) is developed, which successfully realizes the multifunctional combination of electrochromism and energy storage by constructing tungsten trioxide monohydrate (WO3·H2O) nanosheets and Prussian white (PW) film as asymmetric electrodes. The EESD presents excellent electrochromic properties of broad optical modulation (61.7%), ultrafast response speed (1.84/1.95 s), and great coloration efficiency (139.4 cm2 C-1). In particular, remarkable cyclic stability (sustaining 82.5% of its initial optical modulation after 2500 cycles as an electrochromic device, almost fully maintaining its capacitance after 1000 cycles as an energy storage device) is achieved. The EESD is also able to visually detect the energy storage level via reversible and fast color changes. Moreover, the EESD can be combined with commercial solar cells to constitute an intelligent operating system in the architectures, which would realize the adjustment of indoor sunlight and the improvement of physical comfort totally by the rational utilization of solar energy without additional electricity. Besides, a scaled-up EESD (10 × 11 cm2) is further fabricated as a prototype. Such promising EESD shows huge potential in practically serving as electrochromic smart windows and energy storage devices.