Study On Optical Enhancement Effects Of Photonic Crystals And Metal Nono-composites

Recently,micro nanophotonics has attracted a lot of attention.To improve the light utilization efficiency of the process of light-matter interactions and realize the manipulation of light in micro-nano scales is the focus of the research.Two hot research fields of it are photonic crystals and surface plasmons.Photonic crystals, with the characteristic of photonic band gap based on the special periodic structures,can control the propagation of light whose wavelength is in the range of photonic band gap in a certain direction.Surface plasmons,with the characteristics of surface localization and near-field enhancement,can also modulate electromagnetic signals at the nanoscale.Due to their characteristics,photonic crystals and surface plasmons have a wide range of applications in surface enhanced Raman scattering and fluorescence enhancement.The research combining photonic crystals and surface plasmons has very important academic value and practical significance.Therefore,we conducted a study on optical enhancement effects of photonic crystals and metal nono-composites.The mainly contents and results were as follows:(1)Polystyrene microspheres were prepared by emulsion polymerization method using styrene as monomer,methacrylic acid as stabilizer,potassium persulfate as initiator. Polystyrene microspheres of different sizes and monodispersion were obtained by adjusting consumption of monomer, stabilizer and surfactant.The photonic crystals films with different photonic band gap were prepared by colloid self-assembly method.(2)Photonic crystals and silver nano-composites were prepared by ion beam sputtering after co-colloid assembly and calcination.Raman signals of R6G were enhanced significantly by using these SERS substrates.The detection limit of composite substrates prepared by sputtering 20-nanometer-thick silver was 10-9 mol/L.The detection limit of composite substrates prepared by sputtering 80-nanometer-thick silver was 10"8mol/L.However,some interfering peaks can be detected by using these composite substrates.Composite substrates prepared by solvent etching eliminated their interfering peaks.The detection limit of composite substrates prepared by sputtering 20-nanometer-thick silver and 80-nanometer-thick silver were all 10"7mol/L. Compared with the glass substrate and the silver substrate, these composite substrates all have a high density of hot-spot structures and can significantly improve detection sensitivity.(3)Silanization or hydrophobization treatment was first carried out on polystyrene photonic crystals with different photonic band gap.Then the photonic crystals and silver nano-composites were prepared by ion beam sputtering.RhB,a kind of fluorescent material with high quantum yield,was used as detection molecules.The composite substrates and the photonic crystal substrates increased the fluorescence intensity of RhB significantly.Compared with quartz substrates,photonic crystal substrates with hydrophobization treatment had the best effect of fluorescence enhancement.The fluorescence intensity can be enhanced up to 2486 times.MPS-PPV,a kind of fluorescent material with low quantum yield,was also used as detection molecule.The composite substrates and the photonic crystal substrates increased the fluorescence intensity of MPS-PPV significantly.Compared with quartz substrates,composite substrates without hydrophobization treatment had the best effect of fluorescence enhancement.The fluorescence intensity can be enhanced up to 165 times. Surface plasmons increased the excitation efficiency and radiative decay rate.Photonic crystals can suppresse spontaneous emission.Those are the reasons why the fluorescence intensity enhanced greatly. And the enhancement effects of surface plasmons were more significant to the fluorescent material with low quantum yield.