Paper Spray Ionization Mass Spectrometry Establishment And Application Based On Boron Nitride

In recent years,two-dimensional nanomaterials have attracted extensive attention due to their rich chemical and physical properties.Among the large families of two-dimensional nanomaterials,graphene based materials have been widely used in mass spectrometry(MS)due to their universal,frequency independent optical absorption properties and high energy transfer efficiency.However,the application of hexagonal boron nitride nanosheets(h-BNs),which known as "white graphene",was rarely employed in MS.Compared with graphene,h-BNs has many unique characteristics,such as high thermal conductivity and stability,high oxidation resistance and chemical stability.Moreover,h-BNs is a kind of adsorption material,because of the polarity of B-N bond and the large specific surface area for weak interaction with other molecules.In addition,fluorine doped boron nitride nanosheets(h-FBNs)not only own the properties of h-BNs,but also gives the material new characteristics,such as semi gold property,due to the doping of fluorine atoms.Paper spray ionization mass spectrometry(PSI-MS)is a new open environmental mass spectrometry technology which uses paper as the support for sample separation and ionization,which own several advantages,like fast detection speed,low cost,simple preparation etc.However,there are still some disadvantages which hinder its wider application:(1)large number of hydroxyl groups on the surface of the paper,which will form hydrogen bonds or other van Edward interactions with some functional groups of the target compounds,resulting in the target compounds being difficult to elute;(2)in the negative ion mode,corona discharge is easily occurred,which will lead to the decomposition of analyte on the paper substrate,making the MS signal unstable or degraded.Therefore,developing a new type of paper matrix is of great significance to improve the analysis performance of PSI-MS.In view of the existing problems of paper spray mass spectrometry technology and the advantages of h-BNs and h-FBNs,we first combined h-BNs and h-FBNs with paper spray mass spectrometry to establish a negative ion mode paper spray mass spectrometry detection platform based on boron nitriding,and applied it to the detection of molecules in complex biological samples.Additionally,in recent years,monatomic site catalysts have attracted much more attention due to their excellent catalytic performance.However,the research on their catalytic mechanism is relatively limited.Compared with other technologies,MS technology has excellent chemical specificity,which can provide molecular weight and structure information,and directly identify the substrate intermediates.Therefore,this work is the first time to combine the single-atom catalyst with PSI-MS to explore the mechanism of the catalytic reaction,which has important guiding significance for the reasonable design of the target single-atom catalyst with ideal catalytic performance.The main work of this thesis includes the following contents:1.Establishment of negative ion mode PSI-MS based on h-FBNs.By investigating the coating method of nanomaterials,spray voltage,spray solvent,nano material incubation time and other factors,the optimal experimental conditions were obtained,and then a method for the detection of small molecules in complex biological samples was established,especially for the quantification of traditional Chinese medicine components(TCM)in blood samples.Experimental results indicated that the sensitivity of paper spray mass spectrometry with h-FBNs coated paper as substrate increased significantly.LOD of Baicalin in serum and whole blood were calculated to be 20 pmol and 37 pmol respectively,indicating that h-FBNs coated paper base could be used as a new matrix material for negative mode paper spray mass spectrometry.2.The single-atom catalyst catalyst Au/h-BNs is designed and synthesized,and the catalytic mechanism of this composite nanomaterials is explored by combining with PSI-MS.In this work,a classical reaction of nitrophenol reduction to aminophenol was explored for studying the catalyzing mechanism of Au/h-BNs.The results show that the combination of Au/h-BNs with PSI-MS can maintain its catalytic activity and simultaneously applied for detecting the intermediate of catalytic reaction.The design of this project is important for the study of the mechanism of catalytic process and useful for the design of a single atomic site catalyst with ideal catalytic performance.