Study On Angle Spectrum Detection Biosensor Based On Quantum Dot Amplification

Porous silicon with microcavity structure has been widely used to prepare biosensors with high sensitivity.In order to further improve the detection sensitivity of the porous silicon microcavity biosensor,the carboxyl water-soluble Cd Se/Zn S quantum dot(QDs,wavelength is 625 nm)was used to label the complementary DNA(cDNA)molecule for refractive index amplification,and the angle spectrum method based on the porous silicon microcavity structure was used for detection.The main research contents and achievements of this paper are as follows:1.The angle spectrum detection method is optimized by using glass slice,and the principle of the optimized angle spectrum detection method is described in detail.Using Bruggeman theory,the refractive index magnification of porous silicon microcavity(PSM)devices with porosity of 60 % and 80 % respectively under QDs was calculated.The results show that the magnification of PSM devices with porosity of 60 % is 1.15,and that of PSM devices with porosity of 80 % is 1.17.2.Add QDs cDNA solution and QDs solution respectively to the fully functionalized porous silicon microcavity device,and then detect their fluorescence emission spectra respectively,to eliminate the possibility that QDs which are not successfully connected with DNA will cause interference to the experiment.The test results show that QDs without successful DNA connection will not be directly connected to the porous silicon microcavity after full functionalization(after the surface aldehyde group is closed),but will be washed out and will not affect the experiment.In order to verify whether QDs and cDNA are covalently coupled,the X-ray photoelectron spectroscopy(XPS)and Fourier infrared spectroscopy(FIIR)of QDs-cDNA solution are tested to prove whether QDs successfully forms covalent bond with cDNA.The results showed that QDs successfully formed covalent bond with cDNA.3.The porous silicon microcavity device with a central wavelength of 633 nm was designed and fabricated.The cDNA molecules were successfully labeled by the carboxyl water-soluble Cd Se/Zn S QDs and then added to the PSM substrate where the probe was fixed to amplify the refractive index.Finally,the DNA molecules of 16 base pairs were detected by the optimized angle spectrum method.In this method,the TE mode laser with the same wavelength as the central wavelength of the porous silicon microcavity is used as the detection light source,and the glass plate is used to correct the influence caused by the unstable laser power and other factors,so as to ensure the accuracy of the experimental results.The results showed that with the increase of QDs cDNA concentration,the change of angle also increased linearly,and the detection limit was 36 PM.