Optical Fiber Biosensor With Enhanced Sensitivity Based On Two-dimensional Materials

DNA detection is of great significance for molecular biology research,genetic disease diagnosis,etc.Therefore,it is of great practical value to develop a highly sensitive DNA detection method.At present,there are a variety of biosensors used for DNA detection,including surface plasmon resonance(SPR)sensors,electrochemical biosensors,and field-effect transistor(FET)biosensors.Among them,SPR biosensors are widely used because of their high efficiency,high sensitivity,no labeling,real-time dynamic detection,and low sample consumption.However,most of the current commercial SPR biosensors rely on large-scale detection instruments,which have disadvantages such as high operating costs,long time consumption,large size,and difficulty in miniaturization.Optical fiber SPR biosensor has gradually attracted the attention of researchers due to its excellent advantages such as easy manufacturing and operation of integrated equipment,good insulation performance,explosion-proof,anti-corrosion,immunity to electromagnetic interference,and remote detection.Optical fiber SPR sensors have a wide range of applications in food security inspection,gene sequencing,disease diagnosis,environmental monitoring,etc.Depending on the shape of the sensor probe,the optical fiber sensor can be U-shaped,D-shaped,cone-shaped,etc.Two-dimensional materials refer to materials in which electrons can only move freely(plane motion)on the nanometer scale(1-100 nm)in two dimensions.Different two-dimensional materials have different electrical or optical anisotropy due to the special nature of the crystal structure.They have great development potential in the fields of polarized optoelectronic devices,polarized pyroelectric devices,bionic devices,and polarized light detection.Graphene is a two-dimensional material with a single-layer sheet structure composed of carbon atoms.Because of its high specific surface area,high electrical conductivity,and excellent electron mobility at room temperature,graphene can be used as an ideal material for preparing biosensors.Due to the excellent properties of graphene,fiber optic biosensors combined with graphene have attracted widespread attention.Here,based on the unique properties of the two-dimensional material graphene,this research proposed a novel U-shaped localized surface-plasmon resonance optical-fiber-biosensor based on 3D gold nanoparticles and multilayer graphene films and optical fiber SPR biosensor complying with a 3D composite hyperbolic metamaterial and a graphene film.(1)A novel localized surface plasmon resonance(LSPR)biosensor,which used a U-shaped multi-mode fiber(U-MMF),was introduced and investigated.It was modified with a complex of three-dimensional(3D)gold nanoparticles and multilayer graphene as spacer:n*(Au/G)@U-MMF,where n denotes the layer number of gold nanoparticles.The time-domain finite element analysis method was employed to simulate and calculate the electric field intensity of the particle gap.Combined with the actual experimental performance,the number of gold-nanoparticle layers was found to be critical for the sensitivity of the sensor.The sensor showed the sensitivity of 1251.44 nm/RIU,as well as high stability and repeatability;for the measurement-process of time-and concentration-dependent DNA hybridization kinetics with detection concentrations,ranging from 0.1n M to 100 n M,the sensor displayed excellent performance,which points towards a vast potential in the field of medical diagnostics.(2)An optical fiber surface plasmon resonance(SPR)biosensor was developed for measuring time-and concentration-dependent DNA hybridization kinetics.The design used a three-dimensional Au/Al₂O₃ multilayer composite hyperbolic metamaterial(HMM),combined with two-dimensional material graphene for further sensitivity enhancement.Through the time-domain finite element analysis software,the electric field and transmission spectra of HMMs with different structures were simulated.It was found that the introduction of metamaterials can effectively enhance the sensitivity of the sensor.In the experiment,after the second sensitization with graphene,the sensitivity of the appliance was shown to achieve a value of up to 4461nm/RIU,allowing its applicability for bulk refractive index sensing.Furthermore,a biosensor designed in this work displayed high-resolution capability(ranging from 10p M to 100 n M),good linearity,and high repeatability along with a detection limit down to 10 p M,thus suggesting a vast potential for medical diagnostics and clinical applications.