Preparation method of water cluster ground state high-energy isomer

Abstract

The invention provides a preparation method of a water cluster ground state high-energy isomer, which comprises the following steps: firstly, introducing high-purity argon with a first preset flow into a discharge reaction cavity, connecting the discharge reaction cavity with a mass spectrometer, applying a preset direct-current positive high voltage to the tip of a corona discharge needle through a high-voltage power supply, a forward corona electric field is formed between the high-purity argon and a counter electrode of a mass spectrometer, and the forward corona electric field ionizes trace water vapor in the high-purity argon to form water cluster free radical cations; according to the detection result of the mass spectrometer, generating a high-abundance water cluster free radical cation signal, and increasing the applied forward voltage, so that the isomers of the generated water cluster free radical cations are mainly high-energy isomers; and finally, introducing high-purity argon with a second preset air pressure, and introducing a reaction substrate for property research and application research into the discharge reaction cavity in a micro-droplet form by taking the high-purity argon as a carrier gas. The preparation method is mild in preparation condition, high in safety, energy-saving, environment-friendly and high in efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of ground state high-energy isomers of water clusters, and in particular to a method for preparing ground state high-energy isomers of water clusters. Background Art

[0002] Water clusters play an important role in geology, astronomy, chemistry and biology. Water dimers are a prototype system for studying cooperative hydrogen bonds in liquid water and have important scientific value. The ionization of water dimers and subsequent processes are the core issues of various radiation-related chemical and biological processes. Water cluster radical cations (H2O) n ·+ The structure-activity relationship of ions is of great value in fields such as chemical synthesis, nuclear waste management, and the origin of life.

[0003] Taking the dimer water cluster as an example, (H2O)2 ·+ There is [H3O + … · OH] and [H2O…OH2] ·+ There are two typical ground state isomers, among which [H3O + … · OH] is a hydrated proton · OH forms an ion-radical complex, i.e., a proton transfer isomer; [H2O…OH2] ·+ It is a structure containing two centers and three electron bonds (2c3e), composed of H2O ·+ The single electron orbital of the oxygen atom in the middle and the lone pair electron orbital of the oxygen in the adjacent water molecule partially overlap to form a three-electron half-bond isomer. ·+ The high gas phase acidity of (H2O)2 is generally considered to be the preferred structure of the water dimer radical cation, and the existence of the proton transfer isomer is confirmed by the mass spectrum of the collision reaction, infrared dissociation spectrum and liquid phase ultrafast electron diffraction spectrum. Under certain reaction conditions, based on (H2O)2 ·+ The collision-induced dissociation experiments showed that the content of the three-electron half-bond isomer was relatively high and even dominated under certain conditions.

[0004] Theoretically, water cluster radical cations should not have only two stable isomers in the ground state, and other isomers with higher Gibbs free energy should exist. Limited by the increased computational cost in high-precision theoretical analysis and the limitations of existing ionization technology, the experimental and theoretical basis for high-energy isomers of water cluster radical cations is relatively weak, and the efficiency of preparing high-energy isomers of water cluster radical cations is relatively low. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the above prior art and provide a method for efficiently preparing high-energy isomers of water cluster free radical cations.

[0006] The technical solution of the present invention is to provide a method for preparing a ground state high-energy isomer of a water cluster having the following structure, comprising the following steps:

[0007] S1, introducing a first preset flow rate of high-purity argon gas into the discharge reaction chamber, connecting the discharge reaction chamber and the mass spectrometer, applying a preset DC positive high voltage to the needle tip of the corona discharge needle through a high-voltage power supply, and forming a positive corona electric field between the needle tip and the mass spectrometer counter electrode;

[0008] S2. The positive corona electric field ionizes the trace amount of water vapor in the high-purity argon gas to form water cluster free radical cations; according to the detection results of the mass spectrometer, a high-abundance water cluster free radical cation signal is generated, and the applied forward voltage is increased, so that the high-energy isomers are mainly present in the isomers of the generated water cluster free radical cations;

[0009] S3. High-purity argon gas at a second preset pressure is introduced as a carrier gas to introduce reaction substrates for property research and application research into the discharge reaction chamber in the form of micro-droplets.

[0010] Preferably, in step S1, the first preset flow rate is 100 ml / min-400 ml / min.

[0011] Preferably, in step S1, the curvature radius of the tip of the corona discharge needle is 0.01 mm-0.1 mm.

[0012] Preferably, in step S1, the preset DC positive high voltage is 6.0 kV-8.0 kV.

[0013] Preferably, in step S2, the water cluster radical cation signal is (H2O) n ·+ , especially (H2O)2 ·+ and (H2O)3 ·+ Isohydric free radical cations.

[0014] Preferably, in step S2, the structure of the high-energy isomer of the water cluster radical cation is: [ · H(H2O) n … + OH2-OH], especially (H2O)2 ·+ The high-energy isomer structure is [ · H… + OH2-OH].

[0015] Preferably, in step S3, the second preset air pressure is 0.05Mpa-0.40Mpa.

[0016] Preferably, in step S3, the reaction substrate includes one or more of benzene and its derivatives, polycyclic aromatic hydrocarbons and their derivatives, aldehydes, ketones, nitriles, olefins and imines.

[0017] Preferably, in step S3, the raw material injection rate of the micro-droplets is 3 μl / min-50 μl / min.

[0018] Preferably, the counter electrode is an electrode at the entrance of a mass spectrometer, and the gas flow containing product ions partially enters the ion transmission channel of the mass spectrometer and is then detected by a mass analyzer of the mass spectrometer, thereby enabling online monitoring of the properties and application research of high-energy isomers of water cluster radical cations.

[0019] Compared with the prior art, the method for preparing a water cluster ground state high-energy isomer of the present invention has the following advantages:

[0020] High-purity argon contains about 0.5-3ppm of water vapor. The present invention ionizes trace amounts of water vapor through a positive corona electric field to form water cluster free radical cations. On this basis, the intensity of the corona electric field is further increased to increase the content of high-energy isomers in the formed water cluster free radical cations. Finally, the reaction substrate is sprayed out in the form of micro-droplets, so that the high-energy isomers of the water cluster free radical cations generated above react with the substrate at the gas-liquid interface of the micro-droplets, effectively strengthening the mass transfer process and accelerating the chemical reaction at the interface. The present invention has mild preparation conditions, high safety, energy saving and environmental protection, and solves the problems of the prior art lacking low-temperature plasma generation technology for preparing high-energy isomers of water cluster free radical cations and methods for characterizing their properties and applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of preparing high-energy isomers of water cluster radical cations in the present invention;

[0022] Figure 2 is a primary mass spectrum of the high-energy isomer of the water dimer free radical cation prepared in the present invention;

[0023] Figure 3 It is a water dimer radical cation proton transfer isomer [H3O + … · OH](a) and high energy isomers [ · H… + OH2-OH](b) Schematic diagram of the spin density of the configuration;

[0024] Figure 4 for [H3O +… · OH](a) and [ · H… + OH2-OH] (b) Schematic diagram of the geometry and natural layout analysis of the configuration;

[0025] Figure 5 This is the mass spectrum of the gas phase reaction between the high-energy isomers of water dimer free radical cation and volatile nitriles. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 and Figure 2 As shown, the present invention discloses a method for preparing a ground state high-energy isomer of a water cluster, comprising the following steps:

[0028] S1. Pass high-purity argon gas at a flow rate of 100 mL / min into the discharge reaction chamber, connect the discharge reaction chamber and the mass spectrometer, apply a preset DC positive high voltage to the tip of the corona discharge needle through a high-voltage power supply, and form a positive corona electric field between the counter electrode of the mass spectrometer. The positive corona electric field ionizes the trace amount of water vapor in the high-purity argon gas to form water cluster free radical cations; wherein the curvature radius of the tip of the corona discharge needle selected is 0.01 mm, the preset voltage applied is +3.0 kV, and the formed water cluster free radical cations are mainly water dimer free radical cations, i.e. (H2O)2 ·+ ;

[0029] S2. According to the detection results of the mass spectrometer, the preset voltage is further increased to +7.0 kV, so that the isomers of the generated water cluster radical cations are mainly high-energy isomers, that is, [ · H… + OH2-OH];

[0030] S3, introducing high-purity argon gas with a pressure of 0.3 MPa to make it an atomizing gas, and using it as a carrier gas to deliver the reaction substrate input by the injection pump into the discharge reaction chamber in the form of microdroplets; wherein the reaction substrates are volatile 1-butyronitrile, 1-pentanenitrile, cyclopentanenitrile and benzonitrile, and the injection rate of the reaction substrates is 20 μl / min.

[0031] like Figure 3 As shown in the figure, in order to explore the location of positive charges and radicals in the high-energy isomers of the water dimer radical cation, their spin densities were calculated. [H3O + … · OH] configuration can be regarded as the hydrated proton and · OH is formed by hydrogen bonding, and the free radicals are concentrated in · OH. ·H… + OH2-OH] has a relatively special configuration, with free radicals concentrated on H, forming weak hydrogen bonds with protons in water. + OH combines with oxygen in water to form protonated hydrogen peroxide + OH2-OH.

[0032] like Figure 4 As shown, the charge distribution characteristics of the high-energy isomers of the water dimer radical cation were further analyzed. The spin density analysis results were verified by natural layout analysis. + … · In the OH] configuration, the negative charge carried by O (-0.32e) is significantly lower than the charge of O in water (-0.81e). This is because O · The formal charges of OH and H2O are -1 and -2 respectively. · H… + OH2-OH] configuration, it can be clearly seen · The charge of H is 0.06e, which is consistent with · The characteristics of H, the charges of the two O are close to -0.30e, which is consistent with the characteristics of -1 valence O. The O-O bonding can be clearly seen in this structure.

[0033] like Figure 5 As shown, from the primary spectrum, it can be preliminarily analyzed that (the reaction substrate is M) and the main product is [M+H] + 、[M+H2O] ·+ and [2M+H] + Plasma, [M+H2O] ·+ Ions are dominant. [M+H] + and [2M+H] + Possibly derived from (H2O)2 ·+ The reaction of the proton transfer isomer with M; (H2O)2 ·+ The three-electron half-bond isomer and high-energy isomer of can undergo addition reaction with M to generate [M+H2O] ·+ .

[0034] The analysis results showed that no characteristic fragment ions of the amide products formed by the addition of the three-electron half-bond isomers (such as the fragment ions of the lost amine group; + CH2CH2CONH2 (m / z 72); +CONH2 (m / z 44)); however, we found specific fragment ions of oxime losing alkyl, especially the characteristic fragment ions of olefin (such as m / z 59 ion) and alkyne (the reaction substrate is benzonitrile) after McLaren rearrangement and its subsequent cleavage products, such as amine vinyl ion (m / z 43). In addition, when benzonitrile is selected as the reactant, we can not only observe the products of addition with cyano group (-C≡N), but also observe the phenolic products formed by activated benzene ring. However, because cyano group can deactivate the benzene ring, the intensity of m / z 119 ion is slightly lower.

[0035] According to the above preliminary experimental analysis, it is fully verified that the high-abundance water cluster radical cation high-energy isomers can be prepared based on the present invention, and used for performance characterization and application research. The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a ground state high-energy isomer of a water cluster, characterized in that: The following steps are involved: S1, introducing a first preset flow rate of high-purity argon gas into the discharge reaction chamber, connecting the discharge reaction chamber and the mass spectrometer, applying a preset DC positive high voltage to the needle tip of the corona discharge needle through a high-voltage power supply, and forming a positive corona electric field between the needle tip and the mass spectrometer counter electrode; S2. The positive corona electric field ionizes the trace amount of water vapor in the high-purity argon gas to form water cluster free radical cations; according to the detection results of the mass spectrometer, a high-abundance water cluster free radical cation signal is generated, and the applied forward voltage is increased, so that the high-energy isomers are mainly present in the isomers of the generated water cluster free radical cations; S3. High-purity argon gas at a second preset pressure is introduced as a carrier gas to introduce reaction substrates for property research and application research into the discharge reaction chamber in the form of micro-droplets.

2. The method for preparing a ground state high-energy isomer of water clusters according to claim 1, characterized in that: In step S1, the first preset flow rate is 100 ml / min-400 ml / min.

3. The method for preparing a ground state high-energy isomer of water clusters according to claim 1, characterized in that: In step S1, the curvature radius of the tip of the corona discharge needle is 0.01 mm-0.1 mm.

4. The method for preparing a ground state high-energy isomer of water clusters according to claim 1, characterized in that: In step S1, the preset DC positive high voltage is 6.0 kV-8.0 kV.

5. The method for preparing a ground state high-energy isomer of water clusters according to claim 1, characterized in that: In step S2, the water cluster radical cation signal is (H2O) n ·+ .

6. The method for preparing a ground state high-energy isomer of water clusters according to claim 1, characterized in that: In step S2, the structure of the high-energy isomer of the water cluster radical cation is: [ · H(H2O) n … + OH2-OH].

7. The method for preparing a ground state high-energy isomer of water clusters according to claim 1, characterized in that: In step S3, the second preset air pressure is 0.05Mpa-0.40Mpa.

8. The method for preparing a ground state high-energy isomer of water clusters according to claim 1, characterized in that: In step S3, the reaction substrate includes one or more of benzene and its derivatives, polycyclic aromatic hydrocarbons and their derivatives, aldehydes, ketones, nitriles, olefins and imines.

9. The method for preparing a ground state high-energy isomer of water clusters according to claim 1, characterized in that: In step S3, the raw material injection rate of the micro-droplets is 3 μl / min-50 μl / min.

10. The method for preparing a ground state high-energy isomer of water clusters according to claim 1, characterized in that: The counter electrode is the electrode at the entrance of the mass spectrometer. The gas flow containing product ions partially enters the ion transmission channel of the mass spectrometer and is then detected by the mass analyzer of the mass spectrometer. The properties and application research of high-energy isomers of water cluster free radical cations can be monitored online.

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