Furu Zhong

Hybridization assay of insect antifreezing protein gene by novel multilayered porous silicon nucleic acid biosensor

A fabrication of a novel simple porous silicon polybasic photonic crystal with symmetrical structure has been reported as a nucleic acid biosensor for detecting antifreeze protein gene in insects (Microdera puntipennis dzhungarica), which would be helpful in the development of some new transgenic plants with tolerance of freezing stress. Compared to various porous silicon-based photonic configurations, porous silicon polytype layered structure is quite easy to prepare and shows more stability; moreover, polybasic photonic crystals with symmetrical structure exhibit interesting optical properties with a sharp resonance in the reflectance spectrum, giving a higher Q factor which causes higher sensitivity for sensing performance. In this experiment, DNA oligonucleotides were immobilized into the porous silicon pores using a standard crosslink chemistry method. The porous silicon polybasic symmetrical structure sensor possesses high specificity in performing controlled experiments with non-complementary DNA. The detection limit was found to be 21.3nM for DNA oligonucleotides. The fabricated multilayered porous silicon-based DNA biosensor has potential commercial applications in clinical chemistry for determination of an antifreeze protein gene or other genes.

Fabrication of porous silicon-based silicon-on-insulator photonic crystal by electrochemical etching method

We present a fast, novel method for building porous silicon-based silicon-on-insulator photonic crystals in which a periodic modulation of the refractive index is built by alternating different electrochemical etching currents. The morphology and reflectance spectra of the photonic crystals, prepared by the proposed method, are investigated. The scanning electron micrograph and atomic force microscopy images show a very uniform structure and the porous silicon demonstrates an 829 nm wide photonic band gap.

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.

Studies of third-order optical nonlinearities of poly [2,1,3-benzoselenadiazole-(2,5-didodecyloxy-1,4phenylene)ethynylene] embedded in porous silicon

Third order nonlinear properties of new composite materials obtained by embedding A new type π-conjugated poly [2,1,3-benzoselenadiazole-(2,5-didodecyloxy-1,4-phenylene)ethynylene](PPE)in porous silicon are measured in 532nm. The picoseconds measurements show a significant increase of nonlinear refractive index not only with respect to the standard optical materials. The reason can be explained as follows, the Π-electron conjugation bond would be expected to have a significant effect on the ground and excited state dipole moments and electronic transition energies of the molecule and, consequently, could affect the third-order nonlinear optical property of the molecule. The result shows that it is a promising candidate for further material development and possible photonic device applications.

Measurement of the third-order optical nonlinear properties of a metal/porous silicon composite system

We report the measurements of the nonlinear refractive index of a metal/porous silicon composite system as measured by the reflection Z-scan technique. The composite system is formed by using magnetron sputtering to deposit thin metallic films onto porous silicon anodized on p-type silicon. The experiment results indicate an enhancement over the nonlinear refractive index of the composite system, which suggests an opportunity to form new-type nonlinear-optical media consisting of porous silicon for nonlinear optical applications such as power limiting or optical switching.

Optical sensor based on fractal cantor multilayer structures made of porous silicon

We have designed and characterized a novel fractal Cantor multilayer porous silicon photonic crystal with a defect embedded in its middle as an optical sensor for sensing of various chemical and biological species. Compared with the common periodic structure one (such as Bragg) and some aperiodic structure (such as Thue-morse), it is more sensitive because of the lower number of interfaces. This research lays the foundation for design all-silicon sensor for biochemical sensing and can also be good applied in excellent filter.

Porous silicon based resonant grating filters for biochemical sensing applications

Porous silicon has attracted a great deal of attention and research for biochemical sensing applications. In this study, we report a novel porous silicon based resonant grating filters as an optical sensor platform. A narrow bandwidth in the reflectance spectrum is shown of this porous silicon grating filters and this resonance dip shift obviously after little infiltration. This research also played a potential role for the extensive applications in all-silicon biosensor.