Novel Surface Plasmon Resonance Nanostructure And Its Application In Biological Sensing

Excited by electromagnetic wave,coherent oscillations of conduction electrons on a metal surface are known as surface plasmon resonance.This resonance is very sensitive to refractive index changes of the surrounding medium.Thus,plasmonic biosensors process the ability to monitor binding events in real time.Accompanied by the development and maturity of nanofabrication technology,many of the potential means of improving detection sensitivity have arisen.In addition,significant efforts are also taken on miniaturization and integration of the sensing platform,making plasmonic biosensor great candidate for point-of-care diagnosis.However,enhancing the sensitivities of these plasmonic biosensors is still one of the main breakthrough points and challenges in the field of biosensor.In addition,plasmonic biosensors with miniaturization and facile operation characteristics would also be significantly valued.Electromagnetic field enhancement caused by surface plasmon resonance also plays an important role in surface-enhanced raman scattering and surface-enhanced fluorescence,which has great implications in chemical and biological sensing.This paper focuses exclusively on fabrication of novel plasmonic nanostructures via low-cost method.We have studied antisymmetric surface plasmon coupling and electromagnetic field-induced enhanced fluorescence in sandwiched plasmon ruler and nanogap structure,respectively.We have achieved thickness sensitivity of 61 nm nm^-1.30.0-fold fluorescence enhancement has also been realized by using a gold nanoisland substrate.Detailed contents of this paper can be described as follows:1.We combined the colloidal lithography and the wet transfer procedure to fabricate “gold nanohole array/polystyrene/gold film”sandwiched structure.This substrate was highly sensitive to change of the spacer thickness.Using the finite-difference time-domain simulation,we revealed that high localized charge density at the bottom of the nanohole array attributed to unique Bloch wave surface plasmon polarizations?BW-SPP?was critical.The thickness sensitivity is 61 nm nm^-1,largely exceeding the current nanoparticle dimer-based plasmon ruler system.2.We proposed a new strategy where thickness change caused by the adsorption of biomolecules could be accurately detected by our sensing platform.The as-prepared sandwiched plasmon ruler showed great sensitivity in our model detection system.Moreover,we tested clinically relevant biomarkers in human serum samples without using extra antibody or chemical immobilization technique.The structure showed great accuracy,stability and specificity.The limit of detection is as low as 11.9 pg mL^-1.Facile,rapid operation and low-cost fabrication make our platform suitable for clinical diagnosis.3.We focused on electromagnetic field-induced fluorescence enhancement.Using a gold nanoparticle interfacial assembly and an annealing method,we fabricated a gold nanoisland substrate.Furthermore,we revealed that polymer modification and photolithography could greatly improve the performance.When Alexa Fluor 633 was used as a fluorescence label,30.0-fold fluorescence was measured compared with a glass substrate and this value is as 1.4 times as that of pgold,a commercial surface-enhanced fluorescence substrate.These results emphasized the importance of controlling the nanogap structure and great efficiency of the surface modification,and were of great values in fluorescence-based protein detection.In conclusion,the topic discussed in this paper is how to fabricate novel plasmonic nanostructures with low-cost methods to achieve better performance via structural optimization.We started with considering and taking advantage of the electromagnetic coupling phenomena within the plasmonic nanostructures.This paper may provide new ideas about development of ultrahighly sensitive biosensors.