Rearch On An Assembled Porous Silicon Microcavity Biosensor

Porous silicon,as a nanomaterial,has the characteristics of large specific surface area,good biological compatibility,and can be prepared into a variety of structural optical devices,etc.,and has been widely used in the detection of DNA,antigens,antibodies,enzymes and other organisms.Among them,the porous silicon microcavity biosensor has higher sensitivity due to its higher transmittance of defect peak and narrower half-width of transmission peak in reflection spectrum.Previous theoretical analyses have been reported based on the fact that biomolecules can enter all layers,causing the same change of refractive index in each layer of porous silicon.However,there is a big gap between the experimental results and the theory,which is represented by the increase of the half-height width of the resonant peak of the reflection spectrum and the increase of the reflectivity of the resonant peak,indicating that the detection sensitivity is far lower than the theoretical value.The reasons for these results is biological molecules are difficult to deep into the porous silicon,generally only into the depth of the porous silicon about 1 mu m,namely part into the porous silicon,the porous silicon microcavity biosensor underutilized,and only biological molecules to enter the microcavity layer and the following section,will cause the change of the refractive index is larger,the resulting is different on experiment and theory.To solve these problems,this paper designed a assembling microcavity,based on quartz glass by Bragg reflector and the first layer for defect layer below for Bragg reflector porous silicon assembly and become,due to the porous silicon defect layer directly exposed on the surface,the larger the porosity of porous silicon microcavity make biological molecules are more likely to enter layer and the following part,get larger reflection spectrum displacement,with high sensitivity,high Q value microcavity.The following are the main contents of this paper:(1)In this paper,the transfer matrix method is used to analyze the air gap generated in the assembly process.The influence of the thickness of the air gap on the porous silicon and the influence of the assembly of two Bragg mirrors with different wavelengths overall PSM are studied.And it is proved that the assembly microcavity using porous silicon only needs less refractive index change than the traditional microcavity can reach the purpose of measurement.(2)The first layer is the microcavity layer,and the Bragg mirror is below it.The probe DNA is fixed on the pore wall of the functionalized porous silicon.The target DNA is specifically combined with the probe DNA,and the Bragg mirror device based on quartz glass is assembled with porous silicon;(3)In order to reduce the detection limit of porous silicon assembled microcavity biosensor,Cd Se/Zn S quantum dot labeled probe DNA was used to amplify the refractive index,and the angle spectrum method was used to detect the microcavity biosensor.In addition,the experimental device of Angle spectrum method is small in volume and low in price,which is more conducive to biological detection in remote mountainous areas.