Hierarchical Fabrication Of Plasmene Nanosheets For Ultrasensitive And Specific Protein Detection

The great breakthroughs in multi-scale revolutionary technology enables both innovation of microscale structures and expansion of macroscale properties.Novel multifunctional metallic nanoparticles exhibit programmable morphology and unique optoelectronic properties,such as Surface Plasmon Resonance?SPR?,SPR coupling and hybridization,etc.They can be used as building blocks for the construction of nanocrystal-based superlattice materials,enabling great practical significance for flexible optoelectronic devices,biomedical sensing,cancer theranostics,and ultrasensitive biomarker detection.Plasmonic superlattice nanomembrane?Plasmene?is a conceptually new class of two-dimensional thinnest possible metamaterials,which consists of self-assembled metallic nanocrystals with highly ordered nanoscopic structures and distinctive multi-functionality,enabling great practical significance for optoelectronic devices and ultrasensitive sensors.However,it has been notoriously challenging to manipulate at will for large-scale,ordered assembly of plasmonic nanoparticles due to complex interparticle forces.Also,the structure defects severely limits their tunable plasmonic property,thus restricts their practical applications.To essentially tackle those challenges,this thesis focus on large-scale fabrication of soft plasmonic superlattice membrane by using core-shell noble metal nanoparticle as building blocks.The soft ligand induced hierarchical self-assembly at the air-liquid interface has been studied and optimized.By using thorough experimental evaluation,the optical property has been studied in details by adjusting the morphology and aspect-ratio of constituent nanoparticle.Also,this thesis developed sensitivity-enhanced soft membrane with tunable optical property and SERS enhancement factor.Finally,this thesis developed label-free protein detection method by using plasmene sheets as SERS substrate.The specific content of this thesis is as follows:1.First of all,a series of gold nanorods with adjustable aspect ratio and uniform dispersion were synthesized by traditional seed-mediated synthesis method.Several different seed-mediated growth methods were evaluated by comparing the morphology of gold nanorods.This chapter also explores the effects of surfactants,reducing agents,pH of growth solution and seed crystals in the synthesis of gold nanorods.2.On the basis of the gold nanorods synthesized in the second chapter,a uniform Ag shell is grown on the surface of the gold nanorods by surfactant replacement,thereby synthesizing Au@Ag core/shell nanobricks with different Ag shells and aspect ratios.This chapter also explores the differences between g Au@Agcore/shell nanobricks with different aspect ratio gold nanorods as nucleus,and the effect of different AgNO₃ additions on the morphology of g Au@Ag core/shell nanobricks.3.The Au@Ag core/shell nanobricks synthesized in the third chapter are used as the basic unit,and the thiolated polystyrene?PS-SH?is used as the flexible ligand to modify the Au@Ag core/shell nanobricks to make superlattice films.This chapter explores the differences in superlattice films synthesized with different aspect ratios of Au@Ag core/shell nanobricks and gold nanorods as basic nucleus.The SERS effect of the superlattice film was studied by using4-aminothiophenol?4-ATP?as a small molecule probe,SERS enhancement factor of of the superlattice film is about 1.1×10⁵.4.By using the superlattice membrane synthesized in Chapter 4 as the SERS substrate,and the polystyrene on the surface is removed by a plasmonic cleaning machine,then applied to the detection of bovine serum albumin by label-free method.The detection limit is about 15 nM,enabling promising avenue for its clinical application in ultrasensitive biomarker detection.