Rayleigh Imaging Microscopy And Its Application On Nanomaterials

Recently,chirality related studies,including controlled growth,physical properties,and applications,have become the focus of carbon nanotube(CNT)research,and the high-throughput chirality assignment can speed up the chirality related studies.CNT has characteristic peaks in optical spectra(absorption,fluorescence,Raman,Rayleigh,etc.)which are the results of its electronic band structure.In principle,optical spectroscopy can be a high-throughput chirality assignment method for CNTs,but in the case of an individual CNT,which is invisible under optical microscopes,the biggest challenge is how to locate it for further spectroscopic measurements.A real time imaging technique is therefore critical for high throughput optical spectroscopy.Moreover,the advantage of optical microscope lies in convenience and potential to directly provide rich color information.Color reflects the allowed transitions between van Hove singularities in the visible region,providing direct information of the electronic structure of CNTs.Thus a true color imaging technique will provide some qualitative information of chirality.In conclusion,the true color real time imaging technique is very meaningful for the research of CNTs.Here we have designed a general purpose Rayleigh imaging microscope(RIM),which realizes the true color real time imaging of CNTs under an optical microscope.The basic function of RIM is to “see” the nanomaterials,not just CNTs,acquiring the real time information,such as position,morphology,and color,which is very important for the property studies and applications of nanomaterials.The CNTs can be observed more clearly under an optical microscope when immersed in a liquid medium,which is the result of interface dipole enhancement effect.For CNTs,sub-nanometer shells of high refractive index form at the interface when CNTs are immersed in a liquid medium.This interfacial layer,when illuminated by light,behaves as an optical dipole lattice and contributes an instantaneous near field which enhances the local field on neighboring CNTs,which is named interface dipole enhancement effect.We present a general theoretical treatment and experimental verifications of this effect.The Rayleigh imaging microscope plays an important role in the research of CNTs.First,the Rayleigh imaging assisted spectroscopy,which is assembled by the Rayleigh imaging microscope and a spectrometer,realizes the in-situ spectra recording after the quickly localization of CNTs under an optical microscope,and high-throughput chirality assignment of CNTs.Second,the electrodeposition of metal on CNTs can be in-situ recorded under the Rayleigh imaging microscope,which is a visualization technique in electrochemical study.Finally,the Rayleigh imaging technique can make the interfacial reaction visible,such as the photochemical reaction on the surface of CNTs.