Bing Wu

Fabrication of one-dimensional alumina photonic crystals with a narrow band gap and their application to high-sensitivity sensors

In this study, alumina photonic crystals (PCs) were fabricated by applying a sine-wave current in the anodization of aluminum. The effect of periodic time and peak–peak value of the current on the photonic band gap (PBG) were discussed. By selecting the appropriate experimental conditions, a full-width at half maximum (FWHM) of the PBG of only 18 nm was achieved. The experimental results show that the central position of the PBG was proportional to the periodic time of the current signal in the anodization process. A short periodic time allowed the formation of alumina PCs with a narrow band gap. By changing the peak–peak value of the current, the position of the PBG with a narrow FWHM could also be tuned artificially. The as-prepared alumina PCs showed a linear shift of PBG position and transmittance with the increase of refractive index of the analytes infiltrated into the pores, indicating their potential application in chemical sensing or bio-sensing.

A facile and universal way to fabricate superlattice nanowire arrays

A facile and universal synthetic approach for preparing superlattice nanowire (SLNW) arrays is developed. In this method, two kinds of elements are alternately electrodeposited into the holes of the anodic alumina oxide (AAO) template, automatically in separate electrolytes by a programmed device. This method is not restricted by the relative values of the reduction potentials of the elements, and the deposition of each element can be controlled independently. Three kinds of representative SLNW arrays containing noble-metal material (Ag/Ni), thermoelectric material (Bi/Sb) and magnetic material (Ni/Cu) with adjustable segment length are fabricated successfully.

The fabrication and thermal expansion properties of 4H-Ag nanowire arrays in porous anodic alumina templates.

Hexagonal silver nanowire (4H-Ag NW) arrays with preferred orientation are fabricated into the holes of porous anodic alumina membranes (AAMs) by direct current electrodeposition. The addition of tartaric acid and low deposition temperature are crucial conditions for the growth of 4H-Ag NWs. The thermal expansion properties of the as-prepared and annealed 4H-Ag NWs are studied by in situ x-ray diffraction in the temperature range from room temperature to 800 °C. The axial thermal expansion coefficient (TEC) of the as-prepared sample decreases initially and increases subsequently, while that of the annealed sample consistently increases during the whole measuring process.

Alumina Photonic Crystals with Defect Modes for Sensor Application

One-dimensional alumina photonic crystals with defect modes were successfully fabricated through inserting a constant voltage waveform into the periodic voltage signals. The transmission spectra show that the thickness of defects plays a key role in determining the transmittance of defect modes. When the thickness was ∼180 nm, an obvious defect mode with the high transmittance of 55% and a narrow full width at half maximum of 18 nm was observed in the original photonic band gaps. The defect mode shifted linearly with the increasing of refractive index of the analytes infiltrated into pores, indicating its potential application in chemical sensing or bio-sensing.