Investigation Of Near-Infrared Surface Plasmon Resonance Sensing Mechanism And Biochemical Sensing Technology

In recent years,surface plasmon resonance(SPR)sensors have attracted considerable attentions because of their advantages like high sensitivity,real-time response and label-free.It is ideal for detecting surface bioaffinity adsorption of biological and chemical analytes.Surface plasmons confined to metallic/dielectric interface are widely known to be sensitive to dielectric refractive index(RI)changes within the decay length of an evanescent field,so it can be used to detect the physical and chemical parameters relating to RI.However,traditional plasmonic sensing technique has been facing the technical challenge in detecting small analytes at low concentrations.The limits of detection(LOD)of most plasmonic biosensors are insufficient to detect trace amounts of small molecules for early-stage disease diagnosis.It is of great significance to develop novel high sensitivity free-label plasmonic sensing technology.In this thesis,we focus on the improvement of sensing sensitivity and biomolecule LOD of SPR sensing technique,and the idea was that the near-infrared SPR sensing technology and its biosensing applications study.Based on the fundamental theory of surface plasmonic sensing,we analyzed the typical characteristics of near-infrared SPR sensing mode,designed and fabricated multifunctional biochemical sensing chips.The near-infrared SPR sensing platform was successfully constructed to realize different biomolecules specific binding monitoring with ultra-low concentration.This work solves the bottleneck problem that limits current SPR sensor to realize small molecule detection at low concentration.Major research works are as follows:1.To improve sensing sensitivity of SPR technique,we demonstrated a highly-sensitive sensing approach based on achieving near-infrared light plasmonic excitation.According to Maxwell's equations,it was predicted the high RI sensitivity characteristics of near-infrared SPR sensing model.Through theoretical analysis of specific characteristics and electromagnetic field distribution of near-infrared SPR,we found that near-infrared incident light at a small incident angle can excite high-sensitive SPR compared with traditional SPR that occurred in visible spectral region,due to its greater interactive volume and stronger electric field intensity in near-infrared area.By constructing and analyzing near-infrared SPR sensing system,high RI sensitivity in the experiments is consistent with the theoretical models,which is more than 1 orders of magnitude better than that of traditional SPR sensors.2.SPR sensor can also improve LOD by increasing the accuracy,except bulk RI sensitivity optimization.The referencing channel can effectively solve the cross-sensitivity effect.We designed a novel self-referencing near-infrared SPR sensor.Dual-channel monitoring scheme was employed to eliminate interference signal caused by nonspecific adsorption and improve sensing accuracy.And graphene oxide-gold nanoparticles conjugates were synthesized and used as signal amplification tags to form sandwich complex on the sensing surface.The designed SPR sensing approach has a great potential for ultralow LOD of various biomolecules.It is worth noting that DNA molecule was successfully detected in the serum sample.The labelfree and highly sensitive SPR technique enables the real-time interrogation of small molecules,allowing for detection of low concentration.3.To further break through the measurement bottlenecks associated with plasmonic sensors for biological sensing,a novel near-infrared plasmonic sensor for ultrasensitive biological sensing was designed and developed based on a continuous gold-coated nanotriangular array sensing structure,so as to achieve high bulk-and surface-sensitivity simultaneously.We further enhanced the detection level for small molecules by using plasmonic coupling between gold nanoparticles and extremely strong local electric near-fields around the nanotriangular array.This technical approach is used to detect hybridization adsorption events of DNA molecule.We detected DNA molecule with an estimated LOD of 1.2 aM,which reached the detection level of traditional fluorescent labeling method.Finally,we summarized the full work,and provided analysis and prospections for future research.We will continuously focus on plasmonic property investigation of metallic materials,optimizing nanostructured biosensing detection and system integration in future work.