Xiaoyi Lv

Porous silicon optical microcavity biosensor on silicon-on-insulator wafer for sensitive DNA detection

Silicon-on-insulator (SOI) wafer is one of the most appealing platforms for optical integrated circuit with the potential to realize high performance Ultra Large Scale Integration (ULSI) and device miniaturization. In this work, based on simulations to obtain appropriate optical properties of a porous silicon microcavity (PSM), we successfully fabricated a highly efficient PSM on SOI wafer by electrochemical etching for DNA detection at optical wavelength 1555.0 nm. The narrow resonance peak with a full width at half maximum about 26.0 nm in the reflectance spectrum gives a high Q factor which causes high sensitivity for sensing performance. The sensitivity of this sensor is investigated through 19-base pair DNA hybridization in the PSM by surface modification using a standard cross link chemistry method. The red shift of the reflectance spectra shows a good linear relationship with complementary DNA concentration, ranging from 0.625 to 12.500 μM, and the detection limit is 43.9 nM. This optical PSM on SOI is highly sensitive, fast responsive, easy to fabricate and low-costly, that will broadly benefit to develop a new optical label-free biosensor on SOI wafer and has a great potential for biochips based on integrated optical devices.

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.

n-Type porous silicon as an efficient surface enhancement Raman scattering substrate

Abstract. Highly active and sensitive surface-enhanced Raman scattering (SERS) substrates were prepared by n-type (1 to 10  Ω·cm in resistivity) porous silicon (PS) substrates of Ag nanoparticles. SERS studies were carried on these substrates with R6G as a test molecule with a λex=785  nm laser. We optimized the fabrication procedure, which is easy and rapid, for nanostructured silver particles on the surface of PS. The maximum of SERS enhancement for R6G is observed for PS with an anodization current density of 6  mA/cm2 and an etching time of 8 min. The detection limit for R6G absorbed on Ag-coated PS (Ag-PS) is 10 nM and SERS spectra show that the Ag-PS substrate has high SERS activity. The larger pore diameter of this new Ag-PS substrate is expected and the size of the pore diameter is about 1.2 μm, which permits better biomolecule infiltration. This new Ag-PS substrate can be applied in SERS in biochemical and biomedical fields.

Angle-resolved diffraction grating biosensor based on porous silicon

In this study, an optical biosensor based on a porous silicon composite structure was fabricated using a simple method. This structure consists of a thin, porous silicon surface diffraction grating and a one-dimensional porous silicon photonic crystal. An angle-resolved diffraction efficiency spectrum was obtained by measuring the diffraction efficiency at a range of incident angles. The angle-resolved diffraction efficiency of the 2nd and 3rd orders was studied experimentally and theoretically. The device was sensitive to the change of refractive index in the presence of a biomolecule indicated by the shift of the diffraction efficiency spectrum. The sensitivity of this sensor was investigated through use of an 8 base pair antifreeze protein DNA hybridization. The shifts of the angle-resolved diffraction efficiency spectrum showed a relationship with the change of the refractive index, and the detection limit of the biosensor reached 41.7 nM. This optical device is highly sensitive, inexpensive, and simp...

Development of silicon-on-insulator-based nanoporous silicon photonic crystals for label-free DNA detection

Abstract. We fabricated a one-dimensional nanoporous silicon photonic crystal on a silicon insulator substrate by a cost-effective electrochemical method as an optical biosensor for the detection of DNA hybridization. In the first step, a transfer matrix method was used to calculate the corresponding reflectivity spectrum for the design of nanoporous silicon photonic crystals. Then silicon-on-insulator-based photonic crystals were prepared by a novel simple electrochemical etching. Genes were hybridized inside the porous silicon (PS) pores by aminopropyltriethoxysilane and glutaraldehyde and detected through frequency resolved reflectance measurements. A detection sensitivity of 17.445  nm/μM is demonstrated with good specific detection. The linear response range covers a concentration range of antifreeze protein gene from 0.625 to 10.000 μM. This high responsivity indicates that the silicon-on-insulator-based PS photonic crystal has significant potential for application in biological micro-electro-mechanical-systems technologies.

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 of a Photoluminescent Film on a Silicon-On-Insulator Device for the Simple, Rapid, and Quantitative Detection of a Hydatid Disease Diagnostic Protein Marker

A silicon-on-insulator (SOI) device is an important integrated circuit technology containing an insulating material. In this paper, an SOI wafer consisting of n-type silicon grown on the surface of a SiO2 layer was adopted. Porous silicon on the SOI surface, prepared by an electrochemical etching method that connected the anode and cathode to the surface of the SOI wafer, displayed strong photoluminescence properties. A hydatid disease diagnostic protein was used as a target molecule to test the detection ability of the device. After immersing the film in different concentrations of the target protein, which resulted in the simple adsorption of the protein by the porous structure, the photoluminescence intensity of the film decreased after adsorption of the protein, and with an increasing protein concentration, the photoluminescence further decreased. This photoluminescence SOI-based porous silicon film provided the rapid quantitative detection of a protein and may be a promising silicon-based optoelectronic material.

Porous silicon biosensor for Echinococcosis detection based on fluorescence spectroscopy

Agriculture and animal husbandry area, such as Xinjiang, has high rates of hydatid disease. Protein P38 of Echinococcus granulosus has practical value in diagnosis of hydatid disease, and it may be used as a diagnostic marker and a prognostic index. In recent years, the development of biosensors based on porous silicon has been developed rapidly. In this experiment, the protein P38 detection based on fluorescence changes of porous silicon following protein P38 molecule adsorption. The results of the tests indicated that, with the increase of antigen concentration, the fluorescence decrease of porous silicon is also increasing. It is provided the foundation for the basic research of the molecular mechanism of P38, and diagnosis and treatment of cystic echinococcosis.

Biochemical sensing application based on optical fiber evanescent wave sensor

We have designed a novel evanescent field fiber optic biosensors with porous silicon dioxide cladding. The pore size of porous silicon dioxide cladding is about 100 nm in diameter. Biological molecules were immobilized to the porous silicon dioxide cladding used APTES and glutaraldehyde. Refractive index of cladding used Bruggemanns effective medium theory. We carried out simulations of changing in light intensity in optical fiber before and after chemical coupling of biomolecules. This novel optical fiber evanescent wave biosensor has a great potential in clinical chemistry for rapid and convenient determination of biological molecule.

Computation and analysis of backward ray-tracing in aero-optics flow fields

A backward ray-tracing method is proposed for aero-optics simulation. Different from forward tracing, the backward tracing direction is from the internal sensor to the distant target. Along this direction, the tracing in turn goes through the internal gas region, the aero-optics flow field, and the freestream. The coordinate value, the density, and the refractive index are calculated at each tracing step. A stopping criterion is developed to ensure the tracing stops at the outer edge of the aero-optics flow field. As a demonstration, the analysis is carried out for a typical blunt nosed vehicle. The backward tracing method and stopping criterion greatly simplify the ray-tracing computations in the aero-optics flow field, and they can be extended to our active laser illumination aero-optics study because of the reciprocity principle.