Application Of Double-pulse Laser And Fiber-based Laser Ion Sources In Solid And Biological Samples

Elemental analysis of solid samples has always been the focus point of analytical chemistry.High ionization potential elements are widely used,but their physical and chemical properties are stable,so solution-based analytical methods not only require complex pretreatment,but also easily introduce impurities.As a direct solid sampling technique,laser is often used in conjunction with spectroscopy and mass spectrometry for the elemental analysis of solid samples.For detection of high ionization potential elements,a large laser power density is often required,which results in widely dispersed kinetic energy of ions and deteriorated spectral resolution.This impasse was broken until the advent of double-pulse laser technology.Desorption and ionization are independent processes,which can be regulated separately.But they work together to greatly alleviates the problem of kinetic energy dispersion caused by single-pulse laser.With increasing attention to the distribution of foreign substances within cells,many methods have been developed for the study of it.However,due to the small size of cells,submicron sampling and high sensitivity analysis are difficult.Though,laser technology is widely used in analysis and detection,it still restricted by the diffraction.At present,most laser-based analysis methods remain at low micron resolution.Hence,in this dissertation divided into two parts.The first part:a self-built double-pulse laser ionization source combined with spectrometer and mass spectrometer respectively to analyze solid samples.The second part:a tapered lens fiber is introduced and coupled with a single femtosecond laser to analyze solid and biological samples.1、A self-built double-pulse laser ionization source was combined with spectrometer and mass spectrometer respectively,for the analysis of elements(especially high ionization potential element).In the spectral experiment,three solid samples were tested by gradient experiments,respectively.The second laser spot to sample distance and the two pulses delay time were optimized.We have optimized the relevant parameters,and compared the ability on solid elements analysis between single-pulse laser and double-pulse laser.The results show that the energy of single-pulse laser is adjusted to produce a weak signal in the samples.By introducing double-pulse laser,signal of the samples is improved to some extent.It is proved that double-pulse laser technique is an effective method to enhance the sample utilization rate and improve the analysis method of detection signal in the case of very small sample amount.In the mass spectrometry experiment,using double-pulse laser ionization mass spectrometry to detect the high ionization potential elements such as Pd(8.644 eV),Sb(8.644 eV),Cd(8.995 eV),Au(9.229 eV)and Pt(9.020 eV).On the one hand,the weak desorption laser energy greatly alleviates the problem of large kinetic energy dispersion and significantly improves the spectral resolution.On the other hand,laser postionization utilizes the "wasted" neutral atoms to improve the atomic utilization and the sensitivity of the instrument.It highlights the strength of double-pulse laser technique on high ionization energy samples.2、A tapered lens fiber prepared by a special method is introduced,and we couple it with a single femtosecond laser to analyze solid and cell samples.Firstly,copper powder and 3,6-diaminoacridine were used to verify the feasibility of the technique.Secondly,the crater size of planar fiber and tapered lens fiber are compared on Al film.When the planar fiber is replaced by the tapered lens fiber,the crater size significantly reduced.It highlights the excellent light gathering ability of tapered lens fiber.Benefit from the excellent performance of femtosecond laser,a submicron crater was obtained on Al film.Finally,with the help of the confocal laser scanning microscope,50 μg/mL was confirmed to be the optimal supply concentration of InP/ZnS quantum dots cultured cells.At the optimum concentration,this technique is applied to the signal acquisition of InP/ZnS quantum dots in cells.In a word,this kind of tapered lens fiber based on special structure has the merits of easy preparation,universality and economy etc.,which brings good news to the exploration of the microscopic world,even inside the cell.