We develop new multifunctional microscopic techniques based on Raman, and fluorescence signals, such as tip-enhanced optical spectroscopy and microscopy. Based on the ‘localized plasmon effect’ and the ‘lightning effect’, an optically excited sharp noble metal tip raster scans over the sample surface at a very close tip-sample distance (e.g. less than 3 nm), allowing to collect the topography and optical information at the nanometer scale simultaneously. This combination provides a unique view-point to investigate nanoscale physical and chemical properties.

We investigate organic semiconductor systems that are commonly used in photovoltaics and organic light emitting diode and their hybrids with metallic nanostructures. We are particularly interested in studying the morphology – related issues, such as the molecular stacking orders, orientation, and the domain formation (size and the arrangement). These issues are found to be critical in the light-management, the charge carrier mobility, exciton diffusion and dissociation in many optoelectronic devices. Employing the unique scanning near-field optical microscopy developed in our lab, we are able to direct study these effects at both micro- and nanometer scale.

We investigate metallic nanostructures of different composition and geometry, especially regarding the plasmonic resonance influences on the second harmonic generation, two/one photon photoluminescence, and surface-enhanced Raman scattering.

We investigate the optical properties (Raman and fluorescence lifetime) of molecules, soft matters, and thin films in dry and liquid conditions. Through the non-linear effects using near infrared ultrafast laser, optical imaging with intrinsic confocal optical resolution in three-dimensional can be achieved. We explore the application of this noninvasive optical method to image the distributions of photosensitizers in tumor tissues for photodynamic therapy.