Nano-Optical Sensing Research Based On Charge Transfer Plasmons

Currently,there are many biological and medical analyses based on the use of optical signals for specific molecular sensing.Due to the development of nanotechnology,various nanostructures have been widely used in biological and chemical analysis based on optical signals.Among them,noble metal(for example,Au,Ag)nanoparticles are most noticeable due to their unique localized surface plasmon resonance(LSPR)properties.In addition,due to the outstanding optical,catalytic properties and various signal output modes of bimetallic plasmonic nanostructures,they have various applications in sensing and biosensing.The first part of this work was to synthesize monodisperse gold nanoparticles with uniform particle size.Then,Au nanoparticle dimers with high purity were prepared by using silver ion soldering method combined with agarose gel electrophoresis.Subsequently,a selective deposition of silver was achieved by using a seed-mediated growth method to obtain the structurally stable and high concentration Au dimer@Ag structures.Particularly,Silver was selectively deposited at the nanogap of Au dimers,so that the concentration of deposited silver can be controlled to achieve the effective regulation of charge transfer plasmon(CTP)resonance over a wide wavelength range at 630-830 nm.And because silver has the property of being easily oxidized,the structure had a good spectral response to hydrogen peroxide,and thus it is expected to be applied in the process of hydrogen peroxide-mediated chemical reaction.The second part of the work was based on Au dimer@Ag structure obtained above,and glucose can produce hydrogen peroxide in the presence of glucose oxidase,through the different optical signals generated by the structure which reacted with glucose,we achieved its application in glucose detection.We mainly used the specificity of Au dimer@Ag structure,which was,silver as the conductive junction(CJ),the width of the junction would directly affect the intensity and position of the CTP peak.And because the silver conductive junction was in the "hot spot" of the dimer structure,its width would also affect the intensity of the SERS signal.Using the relationship between the intensity of the CTP resonance absorption peak of Au dimer@Ag and the glucose concentration,we obtained two standard curves with different linear ranges firstly.Then,a significant color change occurred in the Au dimer@Ag sample solution after reacting with different concentrations of glucose,so that micromolar of glucose can be detected by naked-eye.Finally,the standard curve of the SERS intensity change value with respect to the glucose concentration was obtained by the relationship between the SERS signal and the glucose concentration.