Infrared spectroscopy measurement method and system based on afm-ir

Abstract

The application discloses an infrared spectrum measurement method and system based on AFM-IR, and the method comprises the following steps: S1, placing a sample to be measured in a cavity of a nano infrared spectrometer; S2, vacuumizing the cavity of the nano infrared spectrometer, and controlling the cavity pressure to be a preset pressure; S3, measuring the AFM topographic map of the sample to be measured and the infrared spectrum signal of a sampling point in the AFM topographic map by the nano infrared spectrometer under the preset pressure. Without greatly changing the nano infrared spectrometer, the application can control the intensity of the infrared spectrum signal by controlling the cavity pressure of the nano infrared spectrometer, so that the application brings more extensive application to the precise and efficient measurement of the surface nano infrared information of low-dose materials.

Description

Technical Field

[0001] This invention belongs to the field of atomic force microscopy-infrared spectroscopy technology, specifically relating to an infrared spectroscopy measurement method and system based on AFM-IR. Background Technology

[0002] The nano-infrared spectrometer is a nano-characterization tool based on atomic force microscopy (AFM). It uses atomic force microscopy-infrared (AFM-IR) technology, also known as photothermal induced resonance technology. It uses an AFM probe to detect the thermal expansion of the sample surface at the tip due to the absorption of infrared light of a specific wavelength. Its infrared spectrum spatial resolution can break through the optical diffraction limit, down to the 10-nanometer level, which provides strong technical support for revealing the infrared spectral information of the surface and interface at the nanoscale.

[0003] The basic principle of AFM-IR is based on the thermal expansion of the sample surface at the probe tip due to the absorption of infrared light of a specific wavelength. Simply put, the absorption of infrared light of a specific wavelength by the sample surface at the probe tip can be obtained by measuring the change in the cantilever's mechanical behavior, thus simultaneously obtaining the sample's AFM morphology and infrared spectral information. When infrared light interacts with the sample, the deformation (thermal expansion) of the sample surface approximates the absorption of infrared light. The thermal expansion of the sample surface is detected by the cantilever probe of the AFM (the signal generated by the cantilever motion satisfies a certain relationship with the degree of thermal expansion of the sample surface). The motion of the cantilever can be described by the Euler-Bernoulli equation, as shown in the following formula:

[0004]

[0005] Where q is the load applied to the cantilever by thermal expansion at the probe, EI is the bending stiffness, ρ is the density, S is the cross-sectional area, and γ is the damping.

[0006] Different organic and inorganic functional groups exhibit different characteristic wavelengths of infrared absorption, resulting in varying thermal expansion and different changes in the motion state of the AFM cantilever. This allows for the effective analysis of the chemical distribution on the sample surface, yielding the surface infrared spectrum of a specific sample. AFM-IR technology has been applied to fields such as multilayer thin films, polymer nanocomposites, thin films, pharmaceuticals, and polymer blends, demonstrating its advantage in providing qualitative chemical information at the nanoscale to identify phases.

[0007] However, the above applications are based on standardized, commercial atmospheric environments. There are no examples or related studies yet on how the signal intensity of the infrared spectrum changes when sensitive samples are applied to tests in a vacuum or under specific pressures.

[0008] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide an infrared spectroscopy measurement method and system based on AFM-IR. Summary of the Invention

[0009] In view of this, the purpose of the present invention is to provide an infrared spectroscopy measurement method and system based on AFM-IR.

[0010] To achieve the above objectives, an embodiment of the present invention provides the following technical solution:

[0011] An infrared spectroscopy measurement method based on AFM-IR, the method comprising the following steps:

[0012] S1. Place the sample to be tested into the cavity of the nano-infrared spectrometer;

[0013] S2. Evacuate the cavity of the nano-infrared spectrometer and control the cavity pressure to the preset pressure.

[0014] S3. Under a preset pressure, measure the AFM morphology of the sample to be tested and the infrared spectral signal of the sampling point in the AFM morphology using a nano-infrared spectrometer.

[0015] In one embodiment, the method further includes:

[0016] AFM topography images under different cavity pressures and infrared spectral signals of sampling points in the AFM topography images were obtained, and the spectral intensity thresholds of different infrared spectral signals at the rated wavenumber were obtained.

[0017] Configure the cavity pressure corresponding to the spectral intensity threshold to the preset pressure.

[0018] In one embodiment, the sample to be tested is a PMMA sample containing a carbonyl functional group, with a rated wavenumber of 1730 cm⁻¹. -1 .

[0019] In one embodiment, the preset pressure is between 1.9 mTorr and 760 Torr.

[0020] In one embodiment, the preset pressure is between 100 Torr and 760 Torr.

[0021] In one embodiment, the preset pressure is between 100 Torr and 450 Torr.

[0022] In one embodiment, step S2 specifically includes:

[0023] The cavity of the nano-infrared spectrometer was evacuated until the cavity pressure was less than or equal to 0.4 mTorr;

[0024] Gas is introduced into the cavity of the nano-infrared spectrometer, and the cavity pressure is controlled to a preset pressure.

[0025] In one embodiment, the gas introduced into the cavity of the nano-infrared spectrometer is an inert gas or air.

[0026] The technical solution provided by one embodiment of the present invention is as follows:

[0027] An AFM-IR-based infrared spectroscopy measurement system, the system comprising:

[0028] A nano-infrared spectrometer, comprising a cavity for measuring the AFM morphology and infrared spectral signal of the sample under test;

[0029] The vacuum pumping equipment is connected to the cavity of the nano-infrared spectrometer and is used to evacuate the cavity of the nano-infrared spectrometer.

[0030] The inflation device is connected to the cavity of the nano-infrared spectrometer and is used to control the cavity pressure to a preset pressure.

[0031] In one embodiment, the system further includes:

[0032] The pressure measuring device is connected to the cavity of the nano-infrared spectrometer to obtain the pressure within the cavity.

[0033] The present invention has the following beneficial effects:

[0034] This invention, without significantly altering the nano-infrared spectrometer, can regulate the intensity of infrared spectral signals by controlling the cavity pressure of the nano-infrared spectrometer, thus enabling a wider range of applications for the precise and efficient measurement of surface nano-infrared information of low-dose materials. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic flowchart of the infrared spectroscopy measurement method in this invention;

[0037] Figure 2 This is a schematic diagram of an infrared spectroscopy measurement system in a specific embodiment of the present invention;

[0038] Figure 3 This is an AFM morphology image of a PMMA sample in a specific embodiment of the present invention;

[0039] Figure 4 This is the infrared spectrogram of the same sampling point in the AFM topographic map under different pressures in a specific embodiment of the present invention. Detailed implementation manners

[0040] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0041] Refer Figure 1 As shown, the present invention discloses an infrared spectrum measurement method based on AFM-IR, including the following steps:

[0042] S1. Place the sample to be measured in the cavity of the nano-infrared spectrometer;

[0043] S2. Evacuate the cavity of the nano-infrared spectrometer and control the cavity pressure to a preset pressure;

[0044] S3. Measure the AFM topographic map of the sample to be measured and the infrared spectrum signal of the sampling point in the AFM topographic map under the preset pressure through the nano-infrared spectrometer.

[0045] The present invention also discloses an infrared spectrum measurement system based on AFM-IR, including:

[0046] A nano-infrared spectrometer, which includes a cavity for measuring the AFM topographic map and infrared spectrum signal of the sample to be measured;

[0047] A vacuum pumping device, connected to the cavity of the nano-infrared spectrometer, for evacuating the cavity of the nano-infrared spectrometer;

[0048] An inflation device, connected to the cavity of the nano-infrared spectrometer, for controlling the cavity pressure to a preset pressure.

[0049] Furthermore, the system further includes:

[0050] A pressure measurement device, connected to the cavity of the nano-infrared spectrometer, for obtaining the magnitude of the pressure inside the cavity.

[0051] The following further illustrates the present invention with specific embodiments.

[0052] Refer Figure 2 As shown is a schematic diagram of the infrared spectrum measurement system in a specific embodiment of the present invention, including:

[0053] A nano-infrared spectrometer, comprising a cavity 10 for measuring the AFM morphology and infrared spectral signal of the sample under test;

[0054] Vacuum pumping device 20 is connected to the cavity of the nano-infrared spectrometer and is used to evacuate the cavity of the nano-infrared spectrometer.

[0055] The inflation device 30 is connected to the cavity of the nano-infrared spectrometer and is used to control the cavity pressure to a preset pressure.

[0056] The pressure measuring device 40 is connected to the cavity of the nano-infrared spectrometer and is used to obtain the pressure inside the cavity.

[0057] For example, the nano-infrared spectrometer used in this embodiment is the Bruker NanoIR3-s nano-infrared spectrometer, a nano-characterization tool based on atomic force microscopy (AFM). It employs atomic force microscopy-infrared spectroscopy (AFM-IR), also known as photothermal induced resonance (PTIR), which breaks through the optical diffraction limit in infrared spectroscopy, improving the spatial resolution to the 10-nanometer level, thus providing the possibility of revealing infrared spectral information of surfaces and interfaces at the nanoscale.

[0058] Of course, other AFM-IR-based scanning near-field optical microscopes can also be used in other embodiments, which will not be described in detail here.

[0059] The nano-infrared spectrometer includes an AFM functional unit and an IR functional unit. Among them:

[0060] The IR functional unit includes an infrared light source 11, which is used to provide infrared light of a specific wavelength to the surface of the sample 50 to be tested;

[0061] The AFM functional unit includes: a cantilever probe 12 for detecting the thermal expansion of the sample surface; a laser source 13 and a photodetector 14 for detecting information such as the amplitude of the cantilever probe.

[0062] Before introducing the specific infrared spectroscopy measurement method of the present invention, we first analyze the relationship between the pressure of the cavity and the spectral intensity of the infrared spectral signal at the rated wavenumber.

[0063] The sample selected in this embodiment is PMMA (polymethylmethacrylate), whose main functional group is carbonyl (C=O), and the corresponding rated wavenumber is 1730 cm⁻¹. -1 .

[0064] First, the PMMA sample is placed in the cavity of the nano-infrared spectrometer. Then, the cavity of the nano-infrared spectrometer is evacuated to a pressure of 0.4 mTorr. The AFM morphology of the PMMA sample is measured under a pressure of 0.4 mTorr, and then the infrared spectral signal of the sampling point in the AFM morphology is measured.

[0065] Then, an inert gas (such as argon) is filled into the cavity of the nano-infrared spectrometer until the cavity pressure is 1.9 mTorr. The AFM morphology of the PMMA sample is measured at a pressure of 1.9 mTorr, and then the infrared spectral signal of the sampling point in the AFM morphology is measured.

[0066] Continue to fill the cavity of the nano-infrared spectrometer with inert gas (such as argon) until the cavity pressure is 100 Torr. Measure the AFM morphology of the PMMA sample at a pressure of 100 Torr, and then measure the infrared spectral signal of the sampling point in the AFM morphology.

[0067] Continue to fill the cavity of the nano-infrared spectrometer with inert gas (such as argon) until the cavity pressure is 450 Torr. Measure the AFM morphology of the PMMA sample at a pressure of 450 Torr, and then measure the infrared spectral signal of the sampling point in the AFM morphology.

[0068] Continue filling the cavity of the nano-infrared spectrometer with inert gas (such as argon) until the cavity pressure reaches 760 Torr. Measure the AFM morphology of the PMMA sample at a pressure of 760 Torr, and then measure the infrared spectral signal of the sampling point in the AFM morphology.

[0069] AFM morphology and spectral intensity at different wavenumbers can be measured using a nano-infrared spectrometer. Figure 3 The image shown is an AFM morphology image of the PMMA sample (the AFM morphology is the same under different pressures). Figure 4 The image shows the infrared spectrum of the same sampling point in the AFM topography at different pressures, specifically at a rated wavenumber of 1730 cm⁻¹. -1 The corresponding spectral intensities are shown in the table below.

[0070] Table 1 shows the wave number at different pressures, with a maximum of 1730 cm⁻¹. -1 spectral intensity at

[0071] 1 0.4mTorr 5.1 2 1.9mTorr 6.7 3 100Torr 14.9 4 450 Torr 24.8 5 760Torr 29.0

[0072] It is evident that when using a nano-infrared spectrometer for nano-infrared characterization of samples, the intensity of infrared spectral lines can be effectively adjusted by controllably changing the pressure (or force) of the cavity. Increased cavity pressure results in a significant enhancement of the signal intensity. Therefore, for samples with low concentrations of specific functional groups, their infrared spectra can be tested at higher pressures to improve their detection limits, leading to broader applications for the accurate and efficient measurement of surface nano-infrared information in low-dose materials.

[0073] Compared to testing under atmospheric conditions, the spectral line intensity changes under vacuum or specific pressures. The main reason for this is the change in damping in the Euler-Bernoulli equation. The damping of the probe in a vacuum is less than that under atmospheric conditions. Therefore, the load exerted on the cantilever by thermal expansion at the probe is also less than under atmospheric conditions, resulting in weaker spectral line intensities. Furthermore, it can be inferred that when placed in an environment higher than atmospheric conditions, the resulting spectral line intensity may be further enhanced. This would, to some extent, help improve the infrared detection limit of the sample and enhance the instrument's characterization and analytical capabilities.

[0074] Based on the above analysis, the infrared spectroscopy measurement method in this embodiment includes the following steps:

[0075] S1. Place the sample to be tested into the cavity of the nano-infrared spectrometer;

[0076] S2. Evacuate the cavity of the nano-infrared spectrometer and control the cavity pressure to the preset pressure.

[0077] S3. Under a preset pressure, measure the AFM morphology of the sample to be tested and the infrared spectral signal of the sampling point in the AFM morphology using a nano-infrared spectrometer.

[0078] For example, the sample to be tested in this embodiment is a PMMA sample.

[0079] In this embodiment, the infrared spectral signal of the same sampling point in the AFM topography image under different cavity pressures is first obtained, and the spectral intensity threshold of different infrared spectral signals at the rated wavenumber is obtained; then, the cavity pressure corresponding to the spectral intensity threshold is configured as the preset pressure.

[0080] For example, in this embodiment, the wave number is first obtained at pressures of 0.4 mTorr, 1.9 mTorr, 100 Torr, 450 Torr, and 760 Torr, respectively, with a wave number of 1730 cm⁻¹. -1 The spectral intensities at the specified locations are 5.1, 6.7, 14.9, 24.8, and 29.0, respectively. Based on testing requirements, the spectral intensity threshold is configured to 6.7 in this embodiment (corresponding to a preset pressure of 1.9 mTorr).

[0081] Therefore, when using a nano-infrared spectrometer to perform infrared spectral measurements on PMMA samples, the cavity pressure can be controlled at 1.9 mTorr.

[0082] Of course, the requirements for spectral intensity differ in other embodiments, and the corresponding preset pressure can be configured according to the actual testing needs. The corresponding relationship is as follows:

[0083] When the preset pressure ranges from 1.9 mTorr to 760 Torr, the corresponding spectral intensities are 6.7 to 29.0.

[0084] When the preset pressure ranges from 100 Torr to 760 Torr, the corresponding spectral intensities are 14.9 to 29.0.

[0085] When the preset pressure ranges from 100 Torr to 450 Torr, the corresponding spectral intensity is 14.9 to 24.8.

[0086] In another preferred embodiment of the present invention, for PMMA samples, the spectral intensity threshold is set to 14.9–24.8, corresponding to a preset pressure value of 100 Torr–450 Torr. This ensures both the intensity of the spectral signal and the signal-to-noise ratio (SNR) of the spectral signal, thereby obtaining the optimal infrared spectral signal.

[0087] For example, in this embodiment, the pressure inside the cavity is controlled by filling it with an inert gas. In other embodiments, air or other gases may also be filled in. However, for sensitive materials, only inert gases can be used.

[0088] The above embodiments use PMMA samples containing carbonyl functional groups as an example for illustration. In other embodiments, samples of other materials can be used. Regardless of the material of the sample, the damping of the cantilever probe can be affected by changing the chamber pressure, thereby changing the signal intensity of the infrared spectrum.

[0089] For samples of different materials, the rated wavenumber is selected based on the functional groups of the material, and the corresponding spectral intensity threshold and preset pressure are set according to different needs. Examples will not be given here.

[0090] As can be seen from the above technical solutions, the present invention has the following beneficial effects:

[0091] This invention, without significantly altering the nano-infrared spectrometer, can regulate the intensity of infrared spectral signals by controlling the cavity pressure of the nano-infrared spectrometer, thus enabling a wider range of applications for the precise and efficient measurement of surface nano-infrared information of low-dose materials.

[0092] The specific embodiments described above with reference to the accompanying drawings are exemplary embodiments, but do not represent all embodiments that can be implemented or fall within the scope of the claims. The term "exemplary" as used throughout this specification means "serving as an example, instance, or illustration" and does not imply that it is "preferred" or "advantageous" compared to other embodiments. Specific details are included to provide an understanding of the described techniques. However, these techniques can be practiced without these specific details. In some instances, well-known structures and apparatuses are shown in block diagram form to avoid obscuring the concepts of the described embodiments.

[0093] The foregoing description of this disclosure is provided to enable any person skilled in the art to implement or use this disclosure. Various modifications to this disclosure will be apparent to those skilled in the art, and the general principles applicable herein can be applied to other variations without departing from the scope of this disclosure. Therefore, this disclosure is not limited to the examples and designs described herein, but is consistent with the widest scope of the principles and novel features disclosed herein.

Claims

1. An infrared spectroscopy measurement method based on AFM-IR, characterized in that, The method includes the following steps: S1. Place the sample to be tested into the cavity of the nano-infrared spectrometer; S2. Evacuate the cavity of the nano-infrared spectrometer and control the cavity pressure to the preset pressure. S3. Under a preset pressure, measure the AFM morphology of the sample to be tested and the infrared spectral signal of the sampling point in the AFM morphology using a nano infrared spectrometer. The method further includes: AFM topography images under different cavity pressures and infrared spectral signals of sampling points in the AFM topography images were obtained, and the spectral intensity thresholds of different infrared spectral signals at the rated wavenumber were obtained. Configure the cavity pressure corresponding to the spectral intensity threshold to the preset pressure.

2. The infrared spectroscopy measurement method based on AFM-IR according to claim 1, characterized in that, The sample to be tested is a PMMA sample containing a carbonyl functional group, with a rated wavenumber of 1730 cm⁻¹. -1 .

3. The infrared spectroscopy measurement method based on AFM-IR according to claim 2, characterized in that, The preset pressure ranges from 1.9 mTorr to 760 Torr.

4. The infrared spectroscopy measurement method based on AFM-IR according to claim 2, characterized in that, The preset pressure ranges from 100 Torr to 760 Torr.

5. The infrared spectroscopy measurement method based on AFM-IR according to claim 2, characterized in that, The preset pressure ranges from 100 Torr to 450 Torr.

6. The infrared spectroscopy measurement method based on AFM-IR according to claim 1, characterized in that, Step S2 specifically involves: The cavity of the nano-infrared spectrometer was evacuated until the cavity pressure was less than or equal to 0.4 mTorr; Gas is introduced into the cavity of the nano-infrared spectrometer, and the cavity pressure is controlled to a preset pressure.

7. The infrared spectroscopy measurement method based on AFM-IR according to claim 6, characterized in that, The gas introduced into the cavity of the nano-infrared spectrometer is either an inert gas or air.

8. An infrared spectroscopy measurement system based on the AFM-IR-based infrared spectroscopy measurement method according to any one of claims 1 to 7, characterized in that, The system includes: A nano-infrared spectrometer, comprising a cavity for measuring the AFM morphology and infrared spectral signal of the sample under test; The vacuum pumping equipment is connected to the cavity of the nano-infrared spectrometer and is used to evacuate the cavity of the nano-infrared spectrometer. The inflation device is connected to the cavity of the nano-infrared spectrometer and is used to control the cavity pressure to a preset pressure. The pressure measuring device is connected to the cavity of the nano-infrared spectrometer to obtain the pressure within the cavity.

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