Signal Enhancement Based On Porous Silicon Photonic Crystal Biosensor

Porous silicon one-dimensional photonic crystal biosensor combines the excellent performance of porous silicon and photonic band-gap structure sensors,and has gradually become a promising optical sensor.Compared with the planar devices,the large specific surface area of the porous structure is the superior characteristic of porous silicon,which makes the binding ratio of bio-active probes and measured molecules that are located in porous silicon pores,and the signal capacity per unit area increase greatly.The well biological characteristics of porous silicon and the characteristics of easy preparation of various photonic devices combined with surface plasmon resonance(SPR)technology can further enhance the intensity of Raman and fluorescence detection signals or improve the detection sensitivity of biosensors.The combination of surface gratings and various types of porous silicon photonic devices enables highly sensitive Raman and fluorescence detection,making it an important substrate for the preparation of highly sensitive biosensors.Porous silicon microcavity(MC)devices and distributed Bragg reflector(DBR)devices with different parameters were successfully prepared.Gold nanoparticles(Au NPs)were deposited on the prepared porous silicon devices for rhodamine 6G(R6G)fluorescence enhancement.MC and DBR devices combined with Au NPs can enhance the fluorescence of R6 G immersed in porous silicon,while the MC substrates with different resonant cavity wavelengths have different effects on the fluorescence enhancement,especially when the MC defect wavelength is located at the maximum absorption wavelength of Au NPs(523 nm),the strongest R6 G fluorescence enhancement can be obtained,and the fluorescence intensity of R6 G is2.5 times than that of R6 G on the DBR.A porous silicon MC with a resonant cavity wavelength of 635 nm was prepared by electrochemical etching.The porous silicon MC substrate was prepared into Au NPs/ porous silicon MC fluorescent enhanced substrates by adsorbing Au NPs.The thiol-modified DNA is linked as the target DNA of attachment to the Au NPs on the fluorescence-enhanced substrate,and the Rhodamine Red(RRA)-labeled complementary DNA probe specifically hybridizes to the target DNA.Through quantitative detection,we found that the Au NPs /porous silicon MC substrate can achieve fluorescence enhancement,and the minimum detectable concentration of DNA can reach 10 pM.The Au NPs /porous silicon MC substrate enables thepreparation of highly sensitive biosensors.We present a new technique for fabricating metal nanoparticle/ porous silicon surface grating device systems.After the electrochemical etching of silicon-based rectangular grating into porous silicon,the fluorescence performance of porous silicon on the porous silicon surface grating and the fluorescence enhancement of the probe molecules were studied.Fluorescence enhanced substrate prepared by depositing metal nanoparticles(Au NPs,Ag NPs)on the porous silicon surface grating further enhances the fluorescence signal of the probe molecules.Different from the Ag NPs/ porous silicon substrates,metal nanoparticles periodically distributed on a metal nanoparticle/ porous silicon surface grating substrate have metallic grating characteristics capable of generating strong fluorescence enhancement,and in combination with fluorescence enhancement produced by a porous silicon surface grating,a three-fold increase in fluorescence intensity of the probe molecule has been achieved.In order to obtain a highly sensitive surface-enhanced Raman scattering(SERS),the Raman enhancement of silicon gratings with different groove depths was studied,and the Raman enhancement of porous silicon gratings was studied.Porous silicon surface gratings were prepared experimentally,and Ag NPs were deposited on porous silicon surface gratings to enhance the Raman signal of the detected objects.The Raman enhancement performance of the silicon grating increases with the increase of the groove depth(20 nm-500 nm),and the porous silicon surface grating further enhances the Raman enhancement performance.The SERS response of rhodamine on the Ag NPs/ porous silicon surface grating substrate is significantly enhanced compared to the SERS response of Rhodamine on the Ag NPs/ porous silicon substrate.Coupling of multiple Raman enhancements in Ag NPs/ porous silicon surface grating SERS substrate systems enables highly sensitive SERS responses.We have successfully fabricated a porous silicon composite grating by introducing a vertical porous silicon photonic crystal structure in a planar grating structure.Ag NPs were prepared on the porous silicon composite structure grating substrate by oxidation-reduction method to detect short sequence DNA.Porous silicon composite structure photonic crystals composed of gratings and porous silicon photonic crystals can improve the fluorescence and Raman detection signals of porous silicon.In addition,the MC structured porous silicon composite structure grating has advantages in terms of fluorescence luminescence properties and Ramanproperties,and in particular,Raman intensity can obtain a gain of 8 times.The metal NPs/ porous silicon DBR substrates with grating and non-grating structure prepared under the same conditions have a great influence on the fluorescence emission properties of RRA-DNA.The grating structure possesses the function of adjusting the distribution of metal NPs,so that fluorescence enhancement occurs on the grating substrate,and the grating-free substrate produces strong quenching.The multi-coupling system of porous silicon composite structure grating is conducive to the preparation of sensors based on metal-enhanced fluorescence technology for high-sensitivity biological detection.