Study On The Mechanism Of Interaction Between Biomolecules And Metal Micro-nano Structure With Surface Plasmon Polaritons Response

Surface plasmon polaritons are electromagnetic modes which are formed by the coupling of free electrons and electromagnetic waves on the metal surface,they have the ability of limiting electromagnetic energy to subwavelength scale and nonlinear optical enhancement effect.Surface plasmon polaritons can break the diffraction limit and have wide application prospect in the fields of nanophotonics,biochemical sensing and near-field optics.In this paper,the mechanism of interaction between biological molecules and metal micro-nano structures was investigated by using finite difference time domain method.We analyzed three kinds of biological molecules(i.e.,reducing cytochrome c molecules,bovine serum albumin molecules,1,2,3,4,6-O-penta-o-galloyl-d-glucose molecules)and resonances of surface plasmon polaritons in three corresponding kinds of metal structures(i.e.,metallic nanoparticle array structure,single metallic slit structure,metallic grating structure),and we explored the effect of three biological molecules on the optical properties of the corresponding metallic structures.Our results are helpful for exploring simple,sensitive,convenient and fast methods of detecting and recognizing biomolecules,and can provide theoretical basis for the development of metal nano-biosensors in the future.Our main works is listed as follows.1.We investigated the optical properties of the metal nanoparticle array structure covered by a reduced cytochrome c molecule layer.With the introduction of the reduced cytochrome c molecular layer,the energy of surface from plasmon polaritons can directly transfer to reduced cytochrome c molecules,it leads to the splitting of peak in exticntion spectrum.The wavelength of the cleavage valley in the extinction spectrum is determined by the wavelength of absorption peak of reduced cytochrome c molecules.At the same time,we analyzed the influence of geometrical parameters on the spectral curve.It was found that the peak in exticntion spectrum is redshifted when the length(L)of the metal nanoparticle is increased.As the width(W)of nanoparticle is increased,the peak in exticntion spectrum is blueshifted.When the period(P)is increased,the peak in exticntion spectrum is shifted to long wavelength region.As the molecule layer number is increased,extinction dip becomes deep,however the position of extinction dip is not changed.2.We analyzed the effects of bovine serum albumin molecules layer on the transmission properties of metal nano-slit structure.We found that,with the introduction of molecular layer of bovine serum albumin,the effective refractive index of the metal nano-slit is increased,which results in the redshift of transmission peak.The position and peak value of transmission peak can also be adjusted by the width,thickness of metal slit single,and the number of molecule layer.When the width of the metal slit is increased,the transmission peak is blueshifted.With the increase of the thickness of metal slit and the number of the molecule layer,the transmission peak wavelength is shifted to the long wavelength region.3.We investigated the effect of 1,2,3,4,6-O-penta-o-galloyl-d-glucose molecules layer on the transmission properties of metal grating structure.The 1,2,3,4,6-O-penta-o-galloyl-d-glucose molecules enhance the effective refractive index of metal grating structure,so peak originated from the resonance of surface plasmon polaritons is increased.We also found that geometrical parameters can control the wavelength and value of transmission peak.When the width of metal grating is increased,the transmission peak is blueshifted.When the thickness of metal grating is increased,the transmission peak is redshifted.When the number of molecule layer increased,the transmission peak is also redshifted.