A photoelectric effect ion source, method of ionizing a sample under test

Abstract

The present disclosure relates to the technical field of detection, and provides a photoelectric effect ion source and a method for ionizing a sample to be detected, the method comprising: a metal silver layer, the bottom of the metal silver layer being provided with a reflection-increasing film, and the bottom of the reflection-increasing film being provided with a substrate; a UV light-emitting diode, the metal silver layer being opposite to the UV light-emitting diode, and a channel for passing the sample to be detected being left between the UV light-emitting diode and the metal silver layer; the UV light-emitting diode irradiating the metal silver layer to excite electrons on the surface of the metal silver layer to escape, molecules of the sample to be detected capturing the escaped electrons to generate reactant negative ions, and ion generation being realized; a heating device, the heating device being arranged at the bottom of the substrate and being used for heating the metal silver layer during the process of electron escape; and a shell, the UV light-emitting diode being arranged on the inner top surface of the shell, and the heating device being arranged on the inner bottom surface of the shell. The present disclosure can improve the ionization efficiency of the photoelectric effect ion source on the sample.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of detection, and particularly relates to a photoelectric effect ion source and an ionization method of a sample to be detected. BACKGROUND

[0002] The ion source is a device for ionizing neutral molecules of a sample to be detected into ions. The type and performance of the ion source directly affect the sensitivity and resolution of the analyzer, and is a key component for ensuring efficient analysis and reliable detection of the system.

[0003] The radioactive source was used early, but its use was strictly limited due to safety problems. The corona discharge ion source utilizes gas discharge ionization, which is unstable during operation and needs high voltage support. At the same time, it produces byproduct ions, which affect the experimental results. The ultraviolet lamp photoionization source is expensive; its volume is large, which limits its application in small-sized devices. The photoelectric effect ion source uses light to irradiate the surface of metal or other materials to generate electrons and ionize substances with strong electronegativity. It has the characteristics of cleanliness, safety, simplicity and high efficiency. However, the common photoelectric effect ion source has the problems of large volume of light source, poor heat dissipation performance, easy attenuation of emission electrode and low light utilization efficiency.

[0004] Patent CN101667518A discloses a photoelectric emission ion source and describes its application in mass spectrometry or ion mobility spectrometry. The device includes: an ultraviolet light source; a metal mesh or a metal ring; a carrier gas. However, the reflectivity of the metal to light is high, which reduces the absorption efficiency of light. In addition, the metal surface is easily contaminated and oxidized, which reduces the efficiency of photoelectron emission.

[0005] Patent CN108109892B discloses an ion source device based on the photoelectric effect of a graphene electrode. The ultraviolet light emitted by the light source of the device must pass through a transparent support body to irradiate the graphene layer, which causes a large amount of attenuation of the ultraviolet light during transmission, so the light source utilization efficiency is low. SUMMARY

[0006] To solve the above problems, the present disclosure provides a photoelectric effect ion source and an ionization method of a sample to be detected. The oxidation of the photoelectric effect emission electrode silver after heating is decomposed into silver, which can effectively avoid the attenuation problem caused by the oxidation of the metal. At the same time, the present disclosure adds a reflection-increasing film at the bottom of the metal silver layer, which significantly improves the light absorption efficiency and can improve the ionization efficiency of the sample to be detected.

[0007] The following are the technical details of the present disclosure:

[0008] A photoelectric effect ion source, characterized in that it comprises:

[0009] A metal silver layer, the bottom of which is provided with a reflection-increasing film, and the bottom of the reflection-increasing film is provided with a substrate.

[0010] An ultraviolet light emitting diode is arranged opposite to the silver layer, and a channel is left between the ultraviolet light emitting diode and the silver layer for the sample to pass through; the ultraviolet light emitting diode irradiates the silver layer to excite the electrons on the surface of the silver layer to escape, and the molecules of the sample capture the escaped electrons to generate reactant negative ions, thereby realizing the generation of ions;

[0011] A heating device is arranged at the bottom of the substrate to heat the silver layer during the escape of the electrons;

[0012] A housing is arranged, and the ultraviolet light emitting diode is arranged on the inner top surface of the housing, and the heating device is arranged on the inner bottom surface of the housing.

[0013] Further,

[0014] An opposite electrode is further arranged on the inner top surface of the housing, and the opposite electrode is arranged opposite to the silver layer;

[0015] A positive electrode of a direct current voltage source is connected to the opposite electrode, and a negative electrode is connected to the silver layer.

[0016] Further,

[0017] The material of the housing is PCB, ceramic or glass.

[0018] Further,

[0019] The thickness of the silver layer is 5 nm.

[0020] Further,

[0021] The heating device is a polyimide heating film.

[0022] Further,

[0023] The reflection-increasing film is a mirror surface polymer reflection film.

[0024] Further,

[0025] A constant current source is further arranged and electrically connected to the ultraviolet light emitting diode to supply power to the ultraviolet light emitting diode.

[0026] A method for ionizing a sample, comprising:

[0027] Irradiating the silver layer with the ultraviolet light emitting diode to excite the electrons on the surface of the silver layer to escape;

[0028] Delivering the sample to the channel between the ultraviolet light emitting diode and the silver layer, and the molecules of the sample capture the escaped electrons to generate reactant negative ions, thereby realizing the ionization of the sample.

[0029] The heating device is used to heat the metal silver layer in the process of electron escape.

[0030] Further,

[0031] When the metal silver layer is irradiated by the ultraviolet light emitting diode, an electric field directed to the metal silver layer is applied between the metal silver layer and the inner top surface of the shell, so as to push the electron to escape from the silver metal surface.

[0032] Further,

[0033] When the electric field directed to the metal silver layer is applied between the metal silver layer and the inner top surface of the shell, the cut-off frequency of the photoelectric effect of the metal silver layer is:

[0034] ν0'=ν0-bE 1 / 2

[0035] Wherein, ν0' is the cut-off frequency of the photoelectric effect of the metal silver layer when the external electric field exists, ν0 is the cut-off frequency when the external electric field is 0V, E is the electric field intensity applied to the metal surface, and b is a constant.

[0036] Compared with the prior art, the present disclosure has the following advantages:

[0037] The present application uses the shell (3) to install the ultraviolet light emitting diode (2) on the inner top surface and the heating device (9) on the inner bottom surface, which not only provides stable structural support, but also serves as an ultraviolet light emitting diode substrate, realizes high integration of the photoelectric effect ion source, gives the system the advantage of miniaturization, and improves the integration level.

[0038] The heating device (9) heats the metal silver layer (6) in the process of electron escape, which can decompose silver oxide into silver metal, prevent the emitter electrode from decaying due to oxidation, and according to the formula, the increase of temperature will reduce the metal work function, improve the photoemission efficiency, and further improve the ionization efficiency; the high reflectivity of the anti-reflection film (8) at the bottom of the metal silver layer (6) can reflect the photons back to the metal, realize nearly twice the photon radiation effect, improve the light absorption efficiency of the metal, greatly improve the utilization rate of ultraviolet light, further improve the photoemission efficiency, and thus significantly improve the ionization efficiency.

[0039] In summary, the present application can improve the integration level of the device while significantly improving the ionization efficiency.

[0040] Other features and advantages of the present disclosure will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present disclosure. The objects and other advantages of the present disclosure can be achieved and obtained by the structure indicated in the specification; claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present disclosure, and all other drawings obtained by those of ordinary skill in the art without creative work based on these drawings are within the protection scope of the present disclosure.

[0042] Figure 1 A schematic diagram of the ion source of the present application is shown.

[0043] Figure 2 A schematic diagram of the sample detection system of the embodiment of the present application is shown.

[0044] Reference signs:

[0045] Constant current source-1; ultraviolet light emitting diode-2; shell-3; counter electrode-4; direct current voltage source-5; metal silver-6; substrate-7; anti-reflection film-8; polyimide heating film-9; sample molecules-10; sample inlet-11; sample molecules-12; mass flow meter-13; gas inlet hole-14; UV-LED photoelectric effect ion source system-15; scanning voltage source-16; separation voltage source-17; deflection voltage source-18; repulsion voltage source-19; upper and lower separation electrodes-20, 21; upper and lower detection electrodes-22, 23; shielding electrode-24; gas outlet hole-25; air pump-26; weak current detector-27; upper computer-28. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the following will combine the drawings in the embodiments of the present disclosure to clearly and completely explain the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only some of the embodiments of the present disclosure, not all. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work are within the protection scope of the present disclosure.

[0047] Figure 1 A schematic diagram of the device according to the present application is shown, and the specific implementation details of the present application include:

[0048] A photoelectric effect ion source:

[0049] It includes:

[0050] Metal silver layer (6);

[0051] Ultraviolet light emitting diode (2), opposite to the metal silver layer (6), a channel is left between the ultraviolet light emitting diode (2) and the metal silver layer (6) for the sample to pass through; the ultraviolet light emitting diode (2) irradiates the metal silver layer (6) to excite the electrons of the metal silver layer (6) to escape; the molecules of the sample to be tested capture the escaped electrons to generate reactant negative ions, realizing the generation of ions; a constant current source (1) is used to power the ultraviolet light emitting diode (2).

[0052] A heating device (9) is arranged at the bottom of the metal silver layer (6) for heating the metal silver layer (6) during the photoelectric effect process.

[0053] A housing (3) is provided, and the ultraviolet light emitting diode (2) is mounted on the inner top surface of the housing (3); the heating device (9) is mounted on the inner bottom surface of the housing (3).

[0054] The housing (3) not only provides stable structural support as a photoelectric effect shell, but also serves as a substrate for the ultraviolet light emitting diode, successfully realizing the high integration of the photoelectric effect ion source, thereby giving the system the advantage of miniaturization. The shell material can be selected from PCB, ceramic, glass, etc., and the specific material can be flexibly adjusted according to the requirements. This design not only meets the requirements of high integration, but also takes into account the high heat dissipation requirements, ensuring that the system can maintain a stable working state during high-power operation.

[0055] The heating device (9) can be used for heating to promote the photoelectric effect ion source to oxidize silver in the air to form silver oxide during the working process, and the silver oxide is converted into silver metal through thermal decomposition, thereby effectively preventing the attenuation problem of the emission electrode caused by oxidation. Heating not only solves the problem of photoelectric emission decay, but also improves the ionization efficiency. The relationship between metal escape and metal work function can be described by the following formula:

[0056]

[0057] Where φ o is the work function of the metal at T=0K, T is the temperature of the metal photoemission electrode, γ is the crystal structure coefficient, K B is the Boltzmann constant. According to the formula, when the photoemission electrode material is constant, γ is constant. When the temperature rises, the work function of the metal will decrease, thereby improving the photoemission efficiency.

[0058] Specifically, the heating device (9) can select to use a polyimide heating film.

[0059] Specifically, it further includes:

[0060] The opposite electrode (4) is opposite to the silver layer (6); the positive pole of the direct current voltage source (5) is connected with the opposite electrode (4), and the negative pole is connected with the silver layer (6); the ultraviolet light emitting diode (2) is arranged in the middle of the opposite electrode (4); and the opposite electrode (4) is installed on the inner top surface of the shell (3).

[0061] Under the action of the direct current voltage source (5), the repulsion voltage applied to the silver metal will affect the photoelectric emission process. The influence of the external electric field on the photoelectric emission can be described by the following formula:

[0062]

[0063] Wherein, v0' is the cut-off frequency when the external electric field is 0V, v0 is the cut-off frequency after the electric field is added, E is the electric field intensity added to the metal surface, and b is a constant. According to the formula, when the external electric field increases, the cut-off frequency decreases with the increase of the acceleration potential, thereby reducing the metal work function and increasing the photoelectric emission efficiency. The sample molecules (11) are substances with strong electronegativity, which can combine with electrons or Combination to generate reactant ions For instrument detection.

[0064] Specifically, it further comprises:

[0065] The substrate (7) is arranged on the top of the polyimide heating film (9);

[0066] The reflection-increasing film (8) is arranged between the substrate (7) and the silver layer (6);

[0067] The reflection-increasing film (8) can be a high-efficiency multi-layer mirror surface reflection polymer film, such as 3M ESR 65 Auto or 3M ESR80v2 Auto. The reflection-increasing film (8) has a reflectivity of more than 98%. The depth of the photon into the metal can be calculated according to the following formula: Wherein, I is the transmitted light intensity, I0 is the initial intensity of the incident light, λ is the wavelength of the incident light, k is the extinction coefficient of the metal at the wavelength, and r is the depth of the photon incident on the metal surface.

[0068] According to the formula, the radiation intensity of the light is almost not attenuated when the thickness of the film is generally in the range of 0.5nm to 100nm, and the silver metal film with a thickness of about 5nm is preferred as the photoelectric emission material in the present application. The reflection-increasing film is arranged directly below the silver metal film, and the light reaching the reflection-increasing film is reflected back to the metal from the surface thereof, so as to realize the effect of nearly twice the photon radiation.

[0069] The use of the reflection-increasing film (8) realizes the effect of nearly twice the photon radiation, greatly improves the utilization rate of the ultraviolet light, and further improves the efficiency of the photoelectric emission.

[0070] A neutral molecule ionization method of a sample to be tested:

[0071] 1) When the instrument is started, the ultraviolet light emitting diode (2) light source is turned on under the action of the constant current source (1), ultraviolet light irradiates the surface of the silver metal (6) emitter electrode to generate photoelectric effect and excite electrons to escape;

[0072] 2) The sample to be tested (10) is introduced into the ionization zone by the carrier gas. Under the action of the ultraviolet light emitting diode (2) photoelectric effect ion source, the sample to be tested (10) captures the escaped electrons or combines with oxygen molecular clusters (such as ) to generate reactant negative ions . Only negative ions are generated in this process, and no positive ions are generated, avoiding the loss of positive and negative ion combination.

[0073] Further:

[0074] In the photoelectric effect process, the silver metal is oxidized, the polyimide heating film (9) is turned on to decompose the oxidized silver into silver metal (6) to avoid the attenuation of the emitter electrode, and the photoelectric emission efficiency is increased.

[0075] Further:

[0076] Increasing the voltage of the direct current voltage source (5) increases the photoelectric emission effect.

[0077] The following is an embodiment of the present application:

[0078] As Figure 2 shown: After the gas sample enters the high-field asymmetric waveform ion mobility spectrometry (FAIMS) device through the gas inlet hole (14), it is excited by the ultraviolet light emitting diode photoelectric effect ion source (15) to generate negative ions. The negative ions are separated and screened under the joint action of the separation voltage source (17) and the compensation voltage source (16). At the same time, the deflection voltage source (18) is applied to the lower detection electrode (23), and by adjusting the trajectory of the negative ions, they are finally captured by the lower detection electrode (23). After the signal is amplified by the weak current detector (27), it is finally transmitted to the upper computer (28) through the current signal, so as to obtain the FAIMS spectrum.

[0079] Adjusting the size of the direct current repulsion voltage source (19) will affect the number of escaped electrons per unit time, thereby indirectly changing the ionization efficiency. There is an optimal value for the direct current repulsion voltage (19), if the voltage continues to increase, the negative ions will move towards the opposite electrode, resulting in the inability to enter the separation zone, thereby affecting the subsequent detection effect. Therefore, the temperature of the silver metal (6) emitter electrode is adjusted by the polyimide heating film (9) to improve the electron emission efficiency, and the enhancement reflection film (8) is used to improve the light utilization rate. The shell (3) solves the problem of integration and heat dissipation of the ultraviolet light emitting diode and FAIMS.

[0080] In summary, the following are the technical effects of the present application:

[0081] 1) By integrating the ultraviolet light-emitting diode directly with the shell, the photoelectric effect ion source is highly integrated.

[0082] The present application significantly improves the integration of the photoelectric effect ion source. The integrated structure tightly combines the ultraviolet light-emitting diode and the components of the photoelectric effect ion source in one module, simplifying the overall structure design and improving the reliability and compactness of the device, thereby effectively reducing the space occupation and solving the light source heat dissipation problem while ensuring high electron emission performance.

[0083] 2) The method of heating and decomposing silver oxide to decompose silver is used to solve the problem of decay of the emission electrode of the photoelectric effect ion source during operation.

[0084] In traditional photoelectric effect ion sources, long-term operation of the emission electrode may cause a decrease in ionization efficiency due to the accumulation of oxides or degradation of the electrode material. The present application proposes to use heating and decomposition to convert silver oxide ( ) into silver metal. This solves the problem of performance degradation of traditional electrode materials due to decay during use.

[0085] 3) The use of a reflective film for improving the light absorption efficiency of metal materials achieves a nearly doubled photon radiation effect.

[0086] To further improve the performance of the photoelectric effect ion source, the present application introduces a reflective film (such as 3M ESR 65 Auto or 3M ESR 80v2 Auto film) to enhance the light absorption efficiency. The reflective film enhances the reflection of light, thereby improving the light absorption efficiency of the emission electrode, significantly improving the utilization rate of the UV light source, and achieving a nearly doubled photon radiation effect. This not only improves the ionization efficiency of the photoelectric effect ion source, but also enables higher electron generation at lower power consumption.

[0087] In summary, the present application achieves high integration of the ion source components through the shell, forming an integrated structure design. The low work function metal silver is selected as the photoelectric emission material, and the oxidized silver of the photoelectric effect emission electrode is decomposed into silver by heating, thereby effectively avoiding the decay problem caused by oxidation of the metal. At the same time, the present application adds a reflective film at the bottom of the silver layer, significantly improving the light absorption efficiency and thereby improving the ionization efficiency of the sample to be tested.

[0088] Although the present disclosure is explained in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A photoelectric effect ion source, characterized by, It comprises: a metal silver layer (6) with a bottom provided with a reflection enhancement film (8), and the bottom of the reflection enhancement film (8) is provided with a substrate (7); a UV light emitting diode (2) opposite to the metal silver layer (6), and a channel is left between the UV light emitting diode (2) and the metal silver layer (6) for the passage of a sample to be tested; the UV light emitting diode (2) irradiates the metal silver layer (6) to excite the electrons on the surface of the metal silver layer (6) to escape, and the molecules of the sample to be tested capture the escaped electrons to generate reactant negative ions to realize the generation of ions; a heating device (9) arranged at the bottom of the substrate (7) for heating the metal silver layer (6) during the escape of the electrons; a shell (3), and the UV light emitting diode (2) is arranged on the inner top surface of the shell (3); the heating device (9) is arranged on the inner bottom surface of the shell (3); an opposite electrode (4) is further arranged on the inner top surface of the shell (3), and the opposite electrode (4) is opposite to the metal silver layer (6); the positive electrode of a direct current voltage source (5) is connected with the opposite electrode (4), and the negative electrode is connected with the metal silver layer (6).

2. A photoelectric effect ion source as claimed in claim 1, wherein, The material of the shell (3) is PCB or ceramic or glass.

3. The photoelectric effect ion source of claim 1, wherein The thickness of the metal silver layer (6) is 5 nm.

4. The photoelectric effect ion source of claim 1, wherein The heating device (9) is a polyimide heating film.

5. The photoelectric effect ion source of claim 1, wherein, The reflection enhancement film (8) is a mirror surface polymer reflection film (8).

6. A photoelectric effect ion source as defined in claim 1, wherein It further comprises: a constant current source (1) electrically connected with the UV light emitting diode (2) for supplying power to the UV light emitting diode (2).

7. A method of ionization of a sample under test based on the photoelectric effect ion source of claim 1, characterized in that, It comprises: irradiating the metal silver layer (6) with the UV light emitting diode (2) to excite the electrons on the surface of the metal silver layer (6) to escape; delivering the sample to be tested to the channel between the UV light emitting diode (2) and the metal silver layer (6), and the molecules of the sample to be tested capture the escaped electrons to generate reactant negative ions to realize the generation of ions; heating the metal silver layer (6) with the heating device (9) during the escape of the electrons.

8. The method of ionization of a sample under test according to claim 7, characterized in that, When the UV light emitting diode (2) irradiates the metal silver layer (6), an electric field directed to the metal silver layer (6) is applied between the metal silver layer (6) and the inner top surface of the shell (3) to push the electrons to escape from the surface of the silver metal.

9. The method of ionization of a sample under test according to claim 8, characterized in that, When the electric field directed to the metal silver layer (6) is applied between the metal silver layer (6) and the inner top surface of the shell (3), the cut-off frequency of the photoelectric effect of the metal silver layer (6) is: v0' = v0- bE 1 / 2 wherein v0' is the cut-off frequency of the photoelectric effect of the metal silver layer (6) when an external electric field exists, v0 is the cut-off frequency when the external electric field is 0 V, E is the electric field intensity applied to the metal surface, and b is a constant.

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