Junwei Hou

OPAA template-directed synthesis and optical properties of metal nanocrystals

Ag and Cu nanocrystals (NCs) were assembled into ordered porous anodic alumina (OPAA) by a single-potential-step chronoamperometry technique. The composition, morphology, microstructure, and optical property were analyzed by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and optical absorption spectroscopy. The results indicate that metallic NCs/OPAA composite possesses a significant surface plasmon resonance absorption. For continuous electrodeposition, metallic nanowires are smooth and uniform with face-centered cubic (fcc) single-crystalline structure; however, for interval electrodeposition, the nanowires are bamboo-like or pearl-chain-like with fcc polycrystalline structure. The length of the nanoparticle nanowires or the single-crystalline nanowires can be controlled well by adjusting the experimental cycle times or the continuous depositing time. The transverse dipole resonance of metallic NCs enhances and displays a blue shift with increasing electrodeposition time or experimental cycle times, which is consistent with Zongs results but contradictory to Duans results. The formation mechanisms of the nanoparticle nanowires and the single-crystalline nanowires were discussed in detail.

Preparation and photoluminescence of TiO2/PS composite system

A TiO2/porous silicon (PS) composite system is prepared by chemical vapor deposition. The crystal form with anatase phase of the samples is evaluated by X-ray diffraction and ultraviolet-visible (UV-vis) absorbance spectra, and the morphology with microsphere of TiO2 particles is characterized by scanning electron microscopy. The composite system formed by this technique gives a broad blue luminescence and the mechanism of photoluminescence with TiO2/PS is also discussed.

Synthesis and Characteristics of Large-Area and High-Filling CdS Nanowire Arrays in AAO Template

CdS nanowires arrays were successfully synthesized by a simple solvothermal process using AAO as templates. The phase structures, morphologies, and optical properties of the products were investigated by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and photoluminescence spectroscopy. It was found that the nanowires were composed of hexagonal structure CdS nanoparticles and the average diameters is about 60-70 nm. A strong green emission with a maximum around 505 nm was observed from the synthesized CdS nanowires at room temperature, which was attributed to near-band-edge emission. A 3D self-seed nucleation coalescent process was proposed for the formation of CdS nanowires structures. The present synthetic route is expected to be applied to the synthesis of other II-VI groups or other groups 1D semiconducting materials.

Third-order optical nonlinearities of TiO2/PS composite system

A TiO2/PS composite system is prepared by chemical vapor deposition which is a common technique in preparation of nano-materials. We report the measurements of the nonlinear refractive index of the TiO2/PS composite system as measured by the reflection Z-scan technique. The large magnitude of the third-order nonlinear coefficients of the TiO2/PS composite system shows that it is a promising candidate for further material development and possible photonic device applications.