Preparation And Application Of Shell-isolated Tip

Tip-enhanced Raman spectroscopy(TERS)with ultrahigh spatial resolution can provide the morphology and chemical information at nano-scale simultaneously,even down to sub-nanometer spatial resolution on the internal molecular structure of individual molecule.However,few studies about TERS are performed in solution environment.That is because that impurities in solution are likely to adsorb on the tip,and then will interfere with the Raman information of analyte we are interested below the tip.In addition,the pollutants in air or analyte on the substrate may also adsorb on the tip.Therefore,expanding the study of TERS in these conditions is significance.In order to solve the above-mentioned problems,we developed the preparation method of shell-isolated tip based on shell-isolated nanoparticle enhanced Raman spectroscopy(SHINERS)method invented by our group.Concurrently,this shell-isolated tip has been utilized in plasmon-enhanced Raman scattering,fluorescence spectroscopy and mass spectrometry.The main findings of this thesis are as follows:1.We have developed the method for preparation of the shell-isolated tip by chemical method and atomic layer deposition technique(ALD).A compact and ultra-thin silica shell was coated on the surface of gold or silver tip.By combining TERS experiment and theoretical calculation,it was proved that the gold or silver tip coated with 2 nm silica shell have a strong electromagnetic field enhancement performance.For the silver tip,it prolonged the preservation time.For atomic layer deposition technique,different shell thickness and material,such as titanium dioxide,alumina,can be obtained.Further TERS experiment in solution showed that shell-isolated tip can effectively avoid the adsorption of impurity.2.We have developed shell-isolated tip enhanced fluorescence spectroscopy.The experimental results showed that,compared to the bare Ag tip,shell-isolated tip weakens the nonradiative energy transfer between the metal tip and the fluorescent molecules,obtaining higher fluorescence intensity,and the largest fluorescence enhancement factor was 1.7x 103.The experimental result coincided with theoretical calculation.3.To overcome the problem that the tip apex was easily destroyed in the femtosecond laser near-field enhanced experiment,we developed shell-isolated tip enhanced mass spectrometry.The experimental results showed that,the ultra-thin shell could protect the Ag tip from destruction by higher power density of laser irradiation,while maintaining stronger mass spectrometry signals,and morphology of tip before and after experiment was unchanged.