LABEL-FREE DETECTION OF PROTEIN MICROARRAY WITH HIGH THROUGHPUT SURFACE PLASMON RESONANCE IMAGING(SPRI)

A surface plasmon resonance imaging(SPRI)system was developed for the discrimination of proteins on a gold surface.As a label-free and high-throughput technique,SPRI enables simultaneously monitoring of the biomolecular interactions at low concentrations.We used SPRI as a label-free and parallel method to detect different proteins based on protein microarray.Bovine Serum Albumin(BSA),Casein and Immunoglobulin G(IgG)were immobilized onto the Au surface of a gold-coated glass chip as spots forming a 6×6 matrix.These proteins can be discriminated directly by changing the incident angle of light.Excellent reproducibility for label-free detection of protein molecules was achieved.This SPRI platform represents a simple and robust method for performing high-sensitivity detection of protein microarray.

Imaging Ultrafast Plasmon Dynamics within a Complex Dolmen Nanostructure Using Photoemission Electron Microscopy

We report direct nanoscale imaging of ultrafast plasmon in a gold dolmen nanostructure excited with the 7is laser pulses by combining the interferometric time-resolved technology with the three-photon photoemission electron microscopy （PEEM）. The interferometric time-resolved traces show that the plasmon mode beating pattern appears at the ends of the dimer slabs in the dolmen nanostructure as a result of coherent superposition of multiple localized surface plasmon modes induced by broad bandwidth of the ultrafast laser pulses. The PEEM measurement further discloses that in-phase of the oscillation field of two neighbor defects are surprisingly observed, which is attributed to the plasmon coupling between them. Furthermore, the control of the temporal delay between the pump and probe laser pluses could be utilized for manipulation of the near-field distribution. These findings deepen our understanding of ultrafast plasmon dynamics in a complex nanosystem.

Nano-infrared imaging of localized plasmons in graphene nano-resonators

We conduct in-situ near-field imaging of propagating and localized plasmons（cavity and dipole modes） in graphene nano-resonator. Compared with propagating graphene plasmons, the localized modes show twofold near-field amplitude and high volume confining ability（- 10^6）. The cavity resonance and dipole mode of graphene plasmons can be effectively controlled through optical method. Furthermore, our numerical simulation shows quantitative agreement with experimental measurements. The results provide insights into the nature of localized graphene plasmons and demonstrate a new way to study the localization of polaritons in Van der Waals materials.

Background-free three-dimensional selective imaging of anisotropic plasmonic nanoparticles

There is an increasing demand for advanced optical imaging techniques that can detect and resolve nanosize objects at a spatial resolution below the optical diffraction limit, especially in three-dimensional （3D） cellular environments. In this study, using a polarization-activated localization scheme based on the orientation-dependent properties of anisotropic plasmonic metal nanoparticles （MNPs）, ＂photoswitchable＂ imaging of single gold nanorods （AuNRs） was accomplished not only in two dimensions but also in three dimensions. Moreover, the Rayleigh scattering background arising from the congested subcellular structures was efficiently suppressed. Thus, we obtained the 3D distributions of both the position and the orientation of the AuNRs inside the cells and investigated their intemalization kinetics. To our knowledge, this is the first demonstration of the confocal-like 3D imaging of non-fluorescence nanoparticles with a high resolution and almost zero background. This technique is easy to implement and should greatly facilitate MNP studies and applications in biomedicine and biology.

Chemical Measurement and Analysis: from Phenomenon to Essence

The review summaries our achievements in optical,electrochemical,as well as mass spectrometry analysis and imaging with high sensitivity,specificity,and spatiotemporal resolution.We promoted the plasmonic imaging system,and developed ultra-sensitive plasmonic nanoprobes for the tracking of single molecules in single living cells,as well as plasmonic nanocatalysts for highly efficient energy conversion.In addition,we contributed a lot in electrogenerated chemiluminescence(ECL)analysis and imaging.Pioneering works including localized surface plasmon resonance(LSPR)enhanced ECL,ECL ratiometric detection,BPE based ECL system,multi-color ECL sensing as well as super-resolved ECL imaging have been initiated by our group.Furthermore,we also dedicated in nanopipette based electrochemical analysis in single living cells,as well as ESI-MS analysis on short time scale.