Atomic force microscope-total internal reflection infrared spectrum synchronous acquisition device and method

Abstract

The application discloses an atomic force microscope-full internal reflection infrared spectrum synchronous acquisition device and method, relates to the field of infrared spectrum technology, and combines the infrared laser and the visible laser through a beam combiner, so that the infrared laser and the visible laser are collinear, and collinear laser is obtained. The incident adjusting assembly makes the collinear laser focus on the sample side through the incident side of the three-prism perpendicularly, and makes the focal point of the collinear laser be located directly below the needle tip, completes the spatial position coupling of the collinear laser and the atomic force microscope probe, and a processor processes the micro-cantilever deflection signal generated by the atomic force microscope and the reflected laser intensity signal generated by the photothermal detector, and simultaneously obtains the atomic force microscope infrared spectrum and the full internal reflection infrared spectrum, so that the atomic force microscope infrared spectrum and the full internal reflection infrared spectrum can be synchronously acquired, and the atomic force microscope infrared spectrum and the full internal reflection infrared spectrum can be collected simultaneously and in situ.

Description

Technical Field

[0001] This invention relates to the field of infrared spectroscopy technology, and in particular to an atomic force microscope-total internal reflection infrared spectroscopy synchronous acquisition device and method. Background Technology

[0002] Infrared spectroscopy utilizes the absorption of infrared light by a sample to detect characteristic functional groups within the sample. When the wavelength of infrared light is in the mid-infrared range, its frequency can couple with the stretching and bending vibrations of covalent bonds in the sample molecules. Therefore, infrared spectroscopy has a strong analytical capability for the internal structure of samples.

[0003] Infrared spectroscopy techniques include total internal reflection (TIR) ​​spectroscopy and atomic force microscopy (AFM) infrared spectroscopy. TIR spectroscopy involves fixing the sample to the surface of an infrared-transparent material, adjusting the incident angle to cause total internal reflection of the infrared laser at the material-air interface, and using the evanescent field generated by the TIR to excite characteristic functional groups of the sample molecules. The collected TIR laser light is then compared with the original background laser intensity to obtain the sample's TIR infrared spectrum. AFM infrared spectroscopy has seen significant development in recent years. This technique involves constructing an infrared laser optical path, irradiating the sample surface of the AFM sample with a modulated infrared laser beam, and coupling the AFM probe and the infrared laser through visible laser induction to obtain the AFM infrared spectrum. Atomic force microscopy (AFM) infrared spectroscopy uses an atomic force microscope probe as a detector for the spectrum, breaking through the diffraction limit of infrared imaging and improving the resolution of infrared imaging from the micrometer level to the nanometer level. Currently, there are two commonly used AFM infrared spectroscopy modes: top incidence and bottom incidence. The top incidence mode can be combined with a gold-plated AFM probe and a gold-plated sample substrate to enhance the infrared spectrum of AFM and achieve a higher signal-to-noise ratio. The bottom incidence mode excites the sample by generating an evanescent field when infrared laser light undergoes total internal reflection at the infrared transparent material-air interface. Gold-plated AFM probes are usually used to improve the signal-to-noise ratio.

[0004] For total internal reflection infrared spectroscopy, the long wavelength of infrared lasers (typically 5-15 micrometers) limits its infrared imaging resolution to the micrometer level due to diffraction limitations. To address this drawback, atomic force microscopy (AFM) infrared spectroscopy achieves nanometer-scale infrared imaging of samples, improving infrared imaging resolution by two orders of magnitude. However, since AFM infrared spectroscopy uses an AFM probe as the detector for the infrared laser, its detection principle is highly dependent on the sample's thermal expansion coefficient. Therefore, a total internal reflection infrared spectrum of the sample is needed as a reference to ensure the reliability of the acquired AFM infrared spectrum. However, in practice, it is difficult to simultaneously acquire total internal reflection infrared spectra and AFM infrared spectra in situ (at the same location), ultimately making it difficult to guarantee the synchronization of the two infrared spectra. Summary of the Invention

[0005] The purpose of this invention is to provide an atomic force microscope-total internal reflection infrared spectroscopy synchronous acquisition device and method, which can simultaneously acquire atomic force microscope infrared spectra and total internal reflection infrared spectra, realizing simultaneous, in-situ acquisition of atomic force microscope infrared spectra and total internal reflection infrared spectra.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] An atomic force microscope-total internal reflection infrared spectroscopy synchronous acquisition device is disclosed. The synchronous acquisition device includes an infrared laser source, a visible laser source, a beam combiner, an incident adjustment component, a prism, an atomic force microscope, a photothermal detector, and a processor. A sample is placed on the sample side of the prism. The tip of the atomic force microscope probe of the atomic force microscope is in contact with the sample.

[0008] The beam combiner is used to combine the infrared laser emitted by the infrared laser source and the visible laser emitted by the visible laser source, so that the infrared laser and the visible laser are collinear, resulting in a collinear laser, and then incident the collinear laser onto the incident adjustment component; the collinear laser includes the infrared laser and the visible laser;

[0009] The incident adjustment component is used to reflect the collinear laser, so that the collinear laser passes perpendicularly through the incident side of the prism and is focused onto the side of the sample, and the focal point of the collinear laser is located directly below the needle tip.

[0010] The atomic force microscope is used to generate a microcantilever deflection signal of the microcantilever of the atomic force microscope probe after the collinear laser is focused onto the side of the sample; the microcantilever deflection signal is a curve showing the change of the deflection of the microcantilever over time.

[0011] The photothermal detector is used to receive the reflected laser light emitted from the exit side of the prism and generate a reflected laser intensity signal; the reflected laser light is the laser light generated after the collinear laser light undergoes total internal reflection on the side of the sample; the reflected laser intensity signal is a curve showing the change of the laser intensity of the reflected laser light over time.

[0012] The processor is communicatively connected to the atomic force microscope and the photothermal detector, respectively; the processor is used to process the microcantilever deflection signal and the reflected laser intensity signal to obtain the atomic force microscope infrared spectrum and total internal reflection infrared spectrum.

[0013] In some embodiments, the synchronous acquisition device further includes: a first reflector, a first variable aperture, a flipping component, and a second variable aperture;

[0014] The first reflector is located between the infrared laser source and the beam combiner; the first reflector is used to reflect the infrared laser to the beam combiner.

[0015] The beam combiner is used to combine the infrared laser and the visible laser to obtain a combined laser beam, and the combined laser beam is incident on the first variable aperture.

[0016] The apertures of both the first and second variable apertures are at their minimum; the first variable aperture is used to transmit the combined laser beam to the flipping assembly.

[0017] The flipping component is used to reflect the combined laser beam to the second variable aperture;

[0018] The second variable aperture is used to transmit the combined laser beam to the photothermal detector;

[0019] The photothermal detector is used to receive the combined laser beam and determine the first power of the infrared laser and the second power of the visible laser in the combined laser beam.

[0020] The processor is used to adjust the position and angle of the first reflector according to the first power and the second power until both the first power and the second power reach their maximum values.

[0021] In some embodiments, the flipping assembly includes a flipping frame and a second reflector mounted on the flipping frame; the processor is controlled to connect to the flipping frame; when it is necessary to adjust the position and angle of the first reflector, the flipping frame is controlled to be in an open state, so that the combined laser beam is reflected to the second variable aperture; when it is necessary to obtain the atomic force microscope infrared spectrum and the total internal reflection infrared spectrum, the flipping frame is controlled to be in a closed state, so that the collinear laser beam is incident on the incident adjustment assembly.

[0022] In some embodiments, the incident adjustment assembly includes a three-axis displacement stage and an off-axis parabolic mirror mounted on the three-axis displacement stage; the off-axis parabolic mirror is used to reflect the collinear laser beam.

[0023] The processor is connected to the three-axis displacement stage; the processor is used to control the movement of the three-axis displacement stage so that the collinear laser, after being reflected by the off-axis parabolic mirror, passes perpendicularly through the incident side and is focused onto the side of the sample, and the focal point of the collinear laser is located directly below the needle tip.

[0024] In some embodiments, gold nanoparticles are present on the side of the sample; the gold nanoparticles are obtained by in-situ growth after an aqueous solution of chloroauric acid is dropped onto the side of the sample.

[0025] In some embodiments, the angle between the sample side and the incident side is the same as the angle between the sample side and the exit side.

[0026] In some embodiments, the synchronization acquisition device further includes a plurality of third reflectors that are optically connected sequentially between the first variable aperture and the flipping component.

[0027] A method for simultaneous acquisition of atomic force microscopy-total internal reflection infrared spectroscopy, comprising controlling the aforementioned simultaneous acquisition device to operate, the simultaneous acquisition method including:

[0028] The microcantilever deflection signal generated by an atomic force microscope and the reflected laser intensity signal generated by a photothermal detector are acquired; the microcantilever deflection signal is the curve of the microcantilever deflection over time; the reflected laser intensity signal is the curve of the reflected laser intensity over time.

[0029] The background signal from the infrared laser source is used to process the deflection signal of the microcantilever and the reflected laser intensity signal to obtain the infrared spectrum of the atomic force microscope and the total internal reflection infrared spectrum; the background signal is the curve of the laser intensity of the infrared laser as a function of wavenumber.

[0030] In some embodiments, the process of using the background signal of the infrared laser source to process the microcantilever deflection signal and the reflected laser intensity signal to obtain the atomic force microscope infrared spectrum and the total internal reflection infrared spectrum specifically includes:

[0031] The microcantilever deflection signal is demodulated using a reference signal to obtain the microcantilever amplitude signal; the reference signal is a signal with the same frequency as the pulse repetition frequency of the infrared laser source generated by the infrared laser source; the microcantilever amplitude signal is the curve of the microcantilever amplitude changing over time.

[0032] The microcantilever amplitude signal is converted into a microcantilever amplitude wavenumber signal; the microcantilever amplitude wavenumber signal is the curve of the microcantilever amplitude versus wavenumber.

[0033] Divide the wavenumber signal of the microcantilever amplitude by the background signal to obtain the infrared spectrum of the atomic force microscope.

[0034] The reflected laser intensity signal is converted into a reflected laser intensity wavenumber signal; the reflected laser intensity wavenumber signal is the curve of the reflected laser intensity versus wavenumber.

[0035] Dividing the reflected laser intensity wavenumber signal by the background signal yields the total internal reflection infrared spectrum.

[0036] In some embodiments, the method for determining the pulse repetition frequency of the infrared laser source includes:

[0037] Under conditions where the sample is not irradiated by infrared laser, the background signal of the microcantilever deflection generated by atomic force microscopy is acquired; the background signal of the microcantilever deflection is subjected to FFT transformation to obtain the resonance frequency of the atomic force microscopy probe and the sample; the resonance frequency is set as the pulse repetition frequency of the infrared laser source.

[0038] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0039] This invention provides a device and method for simultaneous acquisition of atomic force microscopy (AFM) and total internal reflection (TIR) ​​infrared spectroscopy. A beam combiner combines infrared and visible laser beams, making them collinear. An incident adjustment component reflects the collinear laser, focusing it perpendicularly onto the sample side via the incident side of a prism, with the focal point directly below the probe tip. This achieves spatial coupling between the collinear laser and the AFM probe. The AFM generates a microcantilever deflection signal. A photothermal detector receives the reflected laser emitted from the exit side of the prism, generating a reflected laser intensity signal. A processor processes the microcantilever deflection signal and the reflected laser intensity signal to simultaneously obtain both the AFM infrared spectrum and the TIR infrared spectrum. This allows for the simultaneous, in-situ acquisition of both AFM infrared and TIR infrared spectra. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the optical path structure of the synchronous acquisition device provided in Embodiment 1 of the present invention for synchronously acquiring two infrared spectra;

[0042] Figure 2 This is a schematic diagram of the optical path of the beam combiner provided in Embodiment 1 of the present invention;

[0043] Figure 3 This is a schematic diagram of the optical path structure of the synchronization acquisition device provided in Embodiment 1 of the present invention when adjusting the collinear state;

[0044] Figure 4 This is a flowchart of the synchronization acquisition method provided in Embodiment 2 of the present invention;

[0045] Figure 5 This is a schematic diagram of the signal transmission path of the synchronization acquisition device provided in Embodiment 2 of the present invention;

[0046] Figure 6 This is a schematic diagram of the data processing flow of the synchronization acquisition device provided in Embodiment 2 of the present invention;

[0047] Figure 7 This is a schematic diagram comparing the amplitude wavenumber signal and background signal of the microcantilever of the spin-coated polystyrene ultrathin film provided in Embodiment 2 of the present invention;

[0048] Figure 8 This is a schematic diagram of the atomic force microscope infrared spectrum of the spin-coated polystyrene ultrathin film provided in Embodiment 2 of the present invention;

[0049] Figure 9 This is a schematic diagram comparing the reflected laser intensity wavenumber signal and the background signal of the spin-coated polystyrene ultrathin film provided in Embodiment 2 of the present invention;

[0050] Figure 10 This is a schematic diagram of the total internal reflection infrared spectrum of the spin-coated polystyrene ultrathin film provided in Embodiment 2 of the present invention;

[0051] Figure 11 This is a schematic diagram of the atomic force microscope-total internal reflection coupled infrared spectrum of the spin-coated polystyrene ultrathin film provided in Embodiment 2 of the present invention;

[0052] Figure 12This is a schematic diagram comparing the wavenumber signal of the microcantilever and the background signal of the spin-coated polyvinyl cinnamate film provided in Embodiment 2 of the present invention.

[0053] Figure 13 This is a schematic diagram of the atomic force microscope infrared spectrum of the spin-coated polyvinyl cinnamate film provided in Example 2 of the present invention;

[0054] Figure 14 This is a schematic diagram comparing the reflected laser intensity wavenumber signal and the background signal of the spin-coated polyvinyl cinnamate thin film provided in Embodiment 2 of the present invention;

[0055] Figure 15 This is a schematic diagram of the total internal reflection infrared spectrum of the spin-coated polyvinyl cinnamate film provided in Example 2 of the present invention;

[0056] Figure 16 This is a schematic diagram comparing the infrared spectra of the spin-coated polyvinyl cinnamate film before and after ultraviolet treatment using an atomic force microscope, as shown in Example 2 of the present invention.

[0057] Figure 17 This is a nano-infrared image of the cast polystyrene-polymethyl methacrylate blend film provided in Example 2 of the present invention. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] The purpose of this invention is to provide an atomic force microscope-total internal reflection infrared spectroscopy synchronous acquisition device and method, which can simultaneously acquire atomic force microscope infrared spectra and total internal reflection infrared spectra, realizing simultaneous, in-situ acquisition of atomic force microscope infrared spectra and total internal reflection infrared spectra.

[0060] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0061] Example 1:

[0062] This embodiment provides a device for simultaneous acquisition of atomic force microscopy-total internal reflection infrared spectroscopy, such as... Figure 1As shown, the synchronous acquisition device includes an infrared laser source (also known as an infrared laser or electro-optic modulator), a visible laser source, a beam combiner, an incident adjustment assembly, a prism, an atomic force microscope, a photothermal detector, and a processor.

[0063] Since infrared lasers cannot be observed with the naked eye, it is impossible to directly couple the infrared laser and the atomic force microscope probe in space using an optical microscope. Therefore, this embodiment further introduces a visible laser that can be observed with the naked eye as a guide laser. First, the visible laser and the infrared laser are adjusted to be collinear. Then, it is observed whether the visible laser and the atomic force microscope probe have achieved spatial coupling. When the visible laser and the atomic force microscope probe achieve spatial coupling, the infrared laser has also achieved spatial coupling with the atomic force microscope probe.

[0064] To achieve the above objectives, this embodiment simultaneously provides an infrared laser source and a visible laser source. The infrared laser source emits infrared laser light, and the visible laser source emits visible laser light. Optionally, this embodiment uses a quantum cascade laser as the infrared laser source and a photodiode as the visible laser source. Figure 1 The solid line in the diagram represents the infrared laser transmission path, and the dashed line represents the visible laser transmission path. Furthermore, to align the two laser beams (i.e., the infrared laser and the visible laser) to a collinear state, this embodiment introduces a beam combiner. The beam combiner can be a zinc selenide window with a surface coating, and its optical path diagram is shown in Figure [Figure number missing]. Figure 2 As shown, the beam combiner is placed at a 45-degree angle relative to the horizontal plane. One side of the beam combiner is coated with a reflective film, which is called the reflecting surface. The other side of the beam combiner is coated with a transmission film, which is called the transmission surface. Infrared laser light emitted from an infrared laser source illuminates the transmission surface, while visible laser light emitted from a visible laser source illuminates the reflective surface. The beam combiner achieves full transmission of 5-12μm infrared laser light incident at 45° and total reflection of 635nm visible laser light incident at 45°. The beam combiner can combine infrared and visible laser light to obtain a combined laser beam. However, to ensure that the infrared and visible laser light passing through the beam combiner are collinear, the incident position of the infrared laser light on the beam combiner needs to be further adjusted. By adjusting the incident position, the infrared and visible laser light passing through the beam combiner are made collinear, resulting in a collinear laser beam.

[0065] This embodiment determines the collinearity of infrared and visible lasers by introducing two variable apertures after the beam combiner. Specifically, if the two variable apertures are simultaneously closed to their minimum state (meaning the apertures of the two variable apertures are at their minimum, at which point the spots of the infrared and visible lasers are larger than the minimum aperture), and the photothermal detector can still detect the maximum infrared and visible laser power, then it proves that the centers of the two laser beams (i.e., the infrared and visible lasers) after passing through the beam combiner both pass through the centers of the two variable apertures. In this case, the collinearity of the infrared and visible lasers can be achieved through the beam combiner, meaning that after passing through the beam combiner, the infrared and visible lasers are in a collinear state. Based on this concept, in designing the synchronous acquisition device, this embodiment takes into account the difficulty of adjusting the incident position of the infrared laser on the beam combiner by moving the infrared laser source. Therefore, several first reflectors are set between the infrared laser source and the beam combiner. The incident position of the infrared laser on the beam combiner is adjusted by adjusting the position and angle of the first reflectors. At the same time, considering that the ultimate goal of the synchronous acquisition device is to synchronously acquire the infrared spectrum and total internal reflection infrared spectrum of atomic force microscopy, it is necessary to introduce the infrared laser and visible laser onto the sample. When judging the collinearity, it is necessary to introduce the infrared laser and visible laser into the photothermal detector. Therefore, this embodiment is equipped with a flipping component. The light path of the infrared laser and visible laser after being combined by the beam combiner is controlled by the flipping component to irradiate the photothermal detector or the sample.

[0066] Based on this, in order to achieve the above-mentioned collinearity adjustment process, such as Figure 3 As shown, the synchronous acquisition device in this embodiment includes a first reflector, a first variable aperture, a flipping assembly, and a second variable aperture. The first reflector is located between the infrared laser source and the beam combiner, and is used to reflect the infrared laser to the beam combiner. In this embodiment, there may be one or more first reflectors. Figure 3The diagram illustrates a configuration including two first reflectors. In this configuration, the infrared laser emitted from the infrared laser source is reflected by the first first reflector to the second first reflector, which then reflects the infrared laser to a beam combiner. The visible laser emitted from the visible laser source is directly incident on the beam combiner, which combines the infrared and visible lasers to obtain a combined laser beam. A first variable aperture, a flipping assembly, and a second variable aperture are sequentially arranged along the optical path from the combined laser beam to the photothermal detector. Both the first and second variable apertures have their apertures at their minimum. The beam combiner directs the combined laser beam to the first variable aperture, which then transmits it to the flipping assembly. During collinearity adjustment, the flipping assembly is in the open state, reflecting the combined laser beam to the second variable aperture. The second variable aperture then transmits the combined laser beam to the photothermal detector. The photothermal detector receives the combined laser beam and determines the first power of the infrared laser and the second power of the visible laser within it. The processor adjusts the position and angle of the first reflector based on the first and second power levels until both reach their maximum values. The position and angle of the first reflector can be adjusted manually or automatically by installing a drive assembly (such as a piezoelectric ceramic) on it. When subsequently acquiring infrared spectra and total internal reflection infrared spectra using atomic force microscopy, the position and angle of the first reflector are maintained at the levels when both the first and second power levels are at their maximum values. At this point, when the infrared laser emitted from the infrared laser source passes through the first reflector and is incident on the beam combiner, the beam combiner can combine the infrared and visible laser beams, resulting in collinear laser beams.

[0067] The flipping assembly in this embodiment may include a flipping frame and a second reflector mounted on the flipping frame. The processor is connected to the flipping frame control. When it is necessary to adjust the position and angle of the first reflector, that is, when it is necessary to incident infrared laser and visible laser onto the photothermal detector, the flipping frame is controlled to be in the open state. Under the action of the second reflector, the combined laser beam is reflected to the second variable aperture. When it is necessary to obtain the infrared spectrum and total internal reflection infrared spectrum of atomic force microscopy, that is, when it is necessary to incident infrared laser and visible laser onto the sample, the flipping frame is controlled to be in the closed state. At this time, the second reflector no longer plays a reflecting role, allowing the collinear laser to be directly incident on the incident adjustment assembly.

[0068] After adjusting the position and angle of the first reflector to ensure that the infrared and visible lasers emitted by the beam combiner are collinear, the synchronization acquisition device can begin operation. At this point, the flipping component is off. With the flipping component off, the laser beam no longer illuminates the photothermal detector but is instead focused onto the prism by the incident adjustment component. The beam combiner combines the infrared laser emitted by the infrared laser source and the visible laser emitted by the visible laser source, ensuring that the infrared and visible lasers are collinear. This collinear laser is then incident onto the incident adjustment component; the collinear laser includes both infrared and visible lasers.

[0069] The incident adjustment component is used to reflect the collinear laser, so that the collinear laser passes perpendicularly through the incident side of the prism and is focused onto the side of the sample. At this time, the focal point of the collinear laser is exactly located on the side of the sample, and the focal point of the collinear laser is located directly below the tip of the probe. Thus, the relative position of the visible laser and the atomic force microscope probe is adjusted by the incident adjustment component to complete the spatial position coupling. Since the visible laser and the infrared laser are collinear, the spatial position coupling of the infrared laser and the atomic force microscope probe is completed simultaneously. The spatial position coupling enables the in-situ acquisition of the infrared spectrum and the total internal reflection infrared spectrum obtained by the atomic force microscope. It should be noted that, since the atomic force microscope probe is very small, only tens of micrometers in size, an optical microscope is needed to align the collinear laser spot with the probe. At the same time, the optical microscope can be used to observe the spot state and determine the focusing level of the collinear laser (whether the focal point is exactly located on the sample side of the prism). Therefore, this embodiment requires manual observation under an optical microscope to drive the incident adjustment component based on the observation results. This allows the relative position of the visible laser and the atomic force microscope probe to be adjusted under the microscope, so that the collinear laser passes perpendicularly through the incident side of the prism and is focused onto the sample side, and the focal point of the collinear laser is located directly below the tip of the probe, thus completing the spatial coupling.

[0070] Specifically, the incident adjustment assembly in this embodiment includes a three-axis displacement stage and an off-axis parabolic mirror mounted on the three-axis displacement stage. The three-axis displacement stage can be a 45° three-axis displacement stage. The off-axis parabolic mirror is used to reflect collinear laser light. The off-axis parabolic mirror is controlled by the 45° three-axis displacement stage and can perform translation of the laser focus and movement along the optical axis. The processor is connected to the three-axis displacement stage control and is used to control the movement of the three-axis displacement stage so that the collinear laser light, after being reflected by the off-axis parabolic mirror, passes perpendicularly through the incident side and is focused onto the side of the sample, and the focal point of the collinear laser light is located directly below the tip of the probe, thus completing the spatial coupling between the infrared laser and the atomic force microscope probe.

[0071] When the incident adjustment assembly focuses the collinear laser perpendicularly onto the sample side of the prism, with the focal point of the collinear laser directly below the needle tip, the collinear laser will undergo total internal reflection at the prism-air interface due to the sample being placed on the sample side of the prism. This generates an evanescent field and reflected laser light. The evanescent field excites the sample, causing it to vibrate. The reflected laser light exits through the exit side of the prism and illuminates the photothermal detector. In this embodiment, the prism can be a zinc selenide triangular prism, a zinc sulfide triangular prism, or a germanium triangular prism, with a zinc selenide triangular prism being preferred.

[0072] In an atomic force microscope (AFM), the tip of the AFM probe contacts the sample. The AFM probe, composed of a microcantilever and a tip, is used to detect changes in sample surface morphology and vibrations. Specifically, after a collinear laser is focused onto the side of the sample, the resulting evanescent field excites the sample, causing vibrations. This generates a microcantilever deflection signal, which is a curve showing the deflection of the microcantilever over time. The generation process can include: the AFM's detection laser illuminates the upper surface of the microcantilever, and the reflected light illuminates a four-quadrant detector. The detection laser can be red visible light. When the sample vibrates, the microcantilever deflects, reflecting the detection laser to different positions on the four-quadrant detector. The AFM generates the microcantilever deflection signal based on these different positions of the detection laser.

[0073] The photothermal detector is used to receive the reflected laser emitted from the exit side of the prism and generate a reflected laser intensity signal. The reflected laser is the laser generated after the collinear laser undergoes total internal reflection on the side of the sample. The reflected laser intensity signal is the curve of the laser intensity of the reflected laser changing with time.

[0074] The processor is communicatively connected to both the atomic force microscope (AFM) and the photothermal detector. It processes the microcantilever deflection signal and the reflected laser intensity signal to obtain the AFM infrared spectrum and the total internal reflection infrared spectrum. Specifically, the evanescent field generated by total internal reflection excites the sample to vibrate. The AFM generates a microcantilever deflection signal, which, after demodulation and infrared laser wavelength scanning, is divided by the background signal from the infrared laser source to obtain the AFM infrared spectrum of the sample. Simultaneously, the photothermal detector receives the reflected laser intensity signal, scans it with the infrared laser wavelength, and divides it by the background signal from the infrared laser source. The background signal is measured by the photothermal detector, thus obtaining the total internal reflection infrared spectrum of the sample. This allows for the simultaneous acquisition of the AFM infrared spectrum and the total internal reflection infrared spectrum.

[0075] Preferably, the angle between the sample side and the incident side is the same as the angle between the sample side and the exit side. This allows the collinear laser to pass perpendicularly through the incident side and illuminate the sample side, and the reflected laser to pass perpendicularly through the exit side and illuminate the photothermal detector. This results in better quality of the reflected laser intensity signal generated by the photothermal detector, and the shape of the prism is easier to manufacture. More preferably, the prism in this embodiment can be an equilateral triangle or an isosceles right triangle. When using an equilateral triangle, the sample side, incident side, and exit side can be arbitrarily set. When using an isosceles right triangle, the side corresponding to the 90-degree angle is used as the sample side, and one of the other two sides is used as the incident side and the other as the exit side. In this case, an off-axis parabolic mirror focuses the collinear laser perpendicularly through the incident side onto the inclined surface (sample side) of the zinc selenide triangular prism. After total internal reflection at the inclined surface of the zinc selenide triangular prism, the visible laser and infrared laser are emitted perpendicularly through the exit side and illuminate the photothermal detector.

[0076] In this embodiment, the prism has gold nanoparticles on the sample side. The gold nanoparticles are obtained by adding an aqueous solution of chloroauric acid to the sample side and then growing them in situ. By setting the gold nanoparticles, the infrared signal can be amplified.

[0077] Optionally, the synchronization acquisition device in this embodiment further includes a plurality of third reflectors that are optically connected sequentially between the first variable aperture and the flipping component. Figure 3 The diagram illustrates a configuration with three third reflectors, each serving a reflective function. These three third reflectors work together to reflect collinear laser beams to the incident adjustment assembly or to reflect combined laser beams to the flipping assembly.

[0078] This embodiment proposes a device for simultaneous acquisition of atomic force microscopy-total internal reflection infrared spectroscopy. It directly combines down-incident atomic force microscopy infrared spectroscopy technology and total internal reflection infrared spectroscopy technology to build a new optical path system. This achieves positional coupling between the infrared laser and the atomic force microscopy probe, and a photothermal detector is added at the end of the optical path to collect the reflected laser. This enables the simultaneous acquisition of atomic force microscopy infrared spectrum and total internal reflection infrared spectrum, solving the problem of simultaneously acquiring the standard infrared spectrum (total internal reflection infrared spectrum) and nano-infrared spectrum (atomic force microscopy infrared spectrum) of polymer samples.

[0079] Example 2:

[0080] This embodiment provides a method for simultaneous acquisition of atomic force microscopy-total internal reflection infrared spectroscopy, controlling the simultaneous acquisition device described in Embodiment 1 to operate, such as... Figure 4 As shown, the synchronization acquisition method includes:

[0081] S1: Acquire the microcantilever deflection signal generated by the atomic force microscope and the reflected laser intensity signal generated by the photothermal detector; the microcantilever deflection signal is the curve of the microcantilever deflection over time; the reflected laser intensity signal is the curve of the reflected laser intensity over time.

[0082] S2: The background signal of the infrared laser source is used to process the deflection signal of the microcantilever and the reflected laser intensity signal to obtain the infrared spectrum of the atomic force microscope and the total internal reflection infrared spectrum; the background signal is the curve of the laser intensity of the infrared laser as a function of wavenumber.

[0083] The process of using the background signal from the infrared laser source to process the microcantilever deflection signal and the reflected laser intensity signal to obtain the atomic force microscope infrared spectrum and total internal reflection infrared spectrum can include:

[0084] (1) The microcantilever deflection signal is demodulated using a reference signal to obtain the microcantilever amplitude signal. The reference signal is a signal with the same frequency as the pulse repetition frequency of the infrared laser source generated by the infrared laser source. The microcantilever amplitude signal is the curve of the microcantilever amplitude changing with time.

[0085] The method for determining the pulse repetition frequency of the infrared laser source includes: acquiring the microcantilever deflection background signal generated by an atomic force microscope (AFM) under conditions where the sample is not irradiated by infrared laser. This microcantilever deflection background signal is generated by the vibration of the sample under the influence of air molecules, causing the microcantilever to deflect. An FFT transform is performed on the microcantilever deflection background signal to obtain a frequency domain signal. The frequency corresponding to the resonance peak (i.e., peak point) in the frequency domain signal is selected as the resonance frequency between the AFM probe and the sample. This resonance frequency is then set as the pulse repetition frequency of the infrared laser source. During the actual operation of the synchronous acquisition device, the infrared laser source operates at this pulse repetition frequency, thereby achieving signal amplification. The FFT transform is a highly efficient algorithm of the DFT, called the Fast Fourier Transform, used to convert time-domain signals into frequency-domain signals.

[0086] (2) The microcantilever amplitude signal is converted into a microcantilever amplitude wavenumber signal, which is the curve of the microcantilever amplitude versus wavenumber. The microcantilever amplitude wavenumber signal is divided by the background signal to obtain the atomic force microscope infrared spectrum.

[0087] Since infrared laser sources are narrowband sources, their emitted wavenumber changes linearly with time. Therefore, a wavenumber-time curve (i.e., a wavenumber-time curve) can be obtained. By aligning the time of the microcantilever amplitude signal with the wavenumber-time curve, the amplitude-wavenumber curve of the microcantilever (i.e., the sample's vibration amplitude as a function of the infrared laser emission wavenumber) can be generated, thus converting the microcantilever amplitude signal into a microcantilever amplitude-wavenumber signal. The obtained microcantilever amplitude-wavenumber signal is then divided by the background signal. The gain of the microcantilever amplitude-wavenumber signal is adjusted according to the infrared laser radiation intensity at each wavenumber to obtain the atomic force microscope infrared spectrum of the sample.

[0088] (3) Convert the reflected laser intensity signal into a reflected laser intensity wavenumber signal, which is the curve of the reflected laser intensity versus the wavenumber. Divide the reflected laser intensity wavenumber signal by the background signal to obtain the total internal reflection infrared spectrum.

[0089] Since infrared laser sources are narrowband sources, their emitted wavenumber changes linearly with time. Therefore, a wavenumber-time curve (i.e., a wavenumber-time curve) can be obtained. By aligning the time of the reflected laser intensity signal with the wavenumber-time curve, a wavenumber-time curve of the reflected laser intensity can be generated, thus converting the reflected laser intensity signal into a reflected laser intensity wavenumber signal. The obtained reflected laser intensity wavenumber signal is then divided by the background signal. The gain of the reflected laser intensity wavenumber signal is adjusted according to the infrared laser radiation intensity at each wavenumber to obtain the total internal reflection infrared spectrum of the sample.

[0090] The processor in this embodiment may include a lock-in amplifier and a host. The signal transmission path of the synchronization acquisition device is as follows: Figure 5 As shown, the data processing flow is as follows: Figure 6As shown, the atomic force microscope (AFM) transmits the background signal of the cantilever deflection to a lock-in amplifier (LCAP). The LCAP calculates the resonant frequencies of the AFM probe and the sample using an FFT transform and transmits this to an infrared laser source. The infrared laser source sets the resonant frequency to the pulse repetition frequency of the infrared laser, thus generating infrared laser light during the actual operation of the synchronous acquisition device. Simultaneously, it generates a reference signal with the same frequency as the pulse repetition frequency and transmits this reference signal to the LCAP. The LCAP then demodulates the cantilever deflection signal acquired by the AFM based on the received reference signal, obtaining the amplitude of the cantilever at the pulse repetition frequency and generating a cantilever amplitude signal. The LCAP transmits the calculated cantilever amplitude signal to the host computer. The host computer plots the amplitude-wavenumber curve (i.e., the cantilever amplitude-wavenumber signal) using the emitted wavenumber of the infrared laser source (wavenumber is the reciprocal of wavelength). The host computer then divides the cantilever amplitude-wavenumber signal by the background signal and adjusts the gain of the cantilever amplitude-wavenumber signal according to the radiation intensity of each wavenumber, thus obtaining the AFM infrared spectrum of the sample. Simultaneously, the photothermal detector transmits the real-time received reflected laser intensity (i.e., reflected laser intensity signal) to a lock-in amplifier, which then outputs the reflected laser intensity signal to the host computer. The host computer plots a laser intensity-wavenumber curve (i.e., reflected laser intensity wavenumber signal) based on the emitted wavenumber of the infrared laser source. The reflected laser intensity wavenumber signal is then divided by the background signal to adjust the gain of the reflected laser intensity wavenumber signal according to the radiation intensity at each wavenumber, thus obtaining the total internal reflection infrared spectrum of the sample. Finally, by comparing the two sets of data (atomic force microscopy infrared spectrum and total internal reflection infrared spectrum), the detection result can be obtained.

[0091] The background signal is obtained by collecting infrared laser light emitted by an infrared laser source using a photothermal detector and recording it in the software.

[0092] To verify the working status of the synchronization acquisition device, several sets of standard samples were used to test its functionality:

[0093] (1) Spin-coated polystyrene ultrathin film

[0094] Because the infrared absorption intensity of polymer ultrathin films is extremely weak, suitable signal amplification methods are required. By growing gold nanoparticles on the side of a zinc selenide triangular prism used for total internal reflection, the infrared signal can be amplified. In this embodiment, an aqueous solution of chloroauric acid is dropped onto the side of the zinc selenide triangular prism sample to grow gold nanoparticles in situ. Experiments showed that a solution concentration of 5 mM (also written as 5 mmol / L, where mol / L is the concentration unit, abbreviated as M) and a modification time (i.e., the time for the aqueous solution of chloroauric acid to soak the side of the zinc selenide triangular prism sample) of 40 s resulted in the optimal signal-to-noise ratio for the infrared signal.

[0095] A 35 nm thick spin-coated polystyrene ultrafilm was selected as the sample for spectral data acquisition. The microcantilever amplitude-wavenumber curve (microcantilever amplitude-wavenumber signal) and background signal are displayed in the same spectrum, as shown below. Figure 7 As shown, Figure 7 The solid line in the image represents the wavenumber signal of the microcantilever, and the dashed line represents the background signal. A division operation is performed between the wavenumber signal of the microcantilever and the background signal to adjust the gain of the spectrum, obtaining the atomic force microscope infrared spectrum of the spin-coated polystyrene ultrafilm, as shown below. Figure 8 As shown. (Through) Figure 8 1452cm can be observed -1 1492cm -1 and 1601cm -1 The absorption peaks all correspond to the characteristic absorption peaks of polystyrene.

[0096] The reflected laser intensity wavenumber signal and the background signal are displayed in the same laser intensity-wavenumber spectrum, such as... Figure 9 As shown, Figure 9 The solid line in the image represents the reflected laser intensity wavenumber signal, and the dashed line represents the background signal. Dividing the reflected laser intensity wavenumber signal and the background signal allows for gain adjustment of the spectrum, yielding the total internal reflection infrared spectrum of the spin-coated polystyrene ultrathin film, as shown below. Figure 10 As shown. (Through) Figure 10 1452cm can be observed -1 1492cm -1 and 1602cm -1 The absorption peaks all correspond to the characteristic absorption peaks of polystyrene.

[0097] The infrared spectrum from atomic force microscopy and the total internal reflection infrared spectrum are superimposed for display, such as... Figure 11 As shown, the same absorption peak can be observed, proving that this technology has the ability to detect polymer ultrathin films in the infrared.

[0098] (2) Spin-coated polyvinyl cinnamate film

[0099] A 100 nm thick polyvinyl cinnamate film was selected as the sample for spectral acquisition. The microcantilever amplitude-wavenumber curve (microcantilever amplitude-wavenumber signal) and background signal are displayed in the same spectrum, as shown below. Figure 12 As shown, Figure 12 The solid line represents the wavenumber signal of the microcantilever, and the dashed line represents the background signal. A division operation is performed between the microcantilever wavenumber signal and the background signal to adjust the gain of the spectrum, yielding the atomic force microscope infrared spectrum of the spin-coated polyvinyl cinnamate film, as shown below. Figure 13 As shown. (Through) Figure 13 979cm can be observed -1 1171cm -1 1202cm -1 1281cm -1 1309cm -1 1449cm -1 1496cm -1 1577cm -1 1636cm -1 and 1709cm -1 The absorption peaks all correspond to the characteristic absorption peaks of polyvinyl cinnamate.

[0100] The reflected laser intensity wavenumber signal and the background signal are displayed in the same laser intensity-wavenumber spectrum, such as... Figure 14 As shown, Figure 14 The solid line represents the reflected laser intensity wavenumber signal, and the dashed line represents the background signal. Dividing the reflected laser intensity wavenumber signal and the background signal allows for gain adjustment of the spectrum, yielding the total internal reflection infrared spectrum of the spin-coated polyvinyl cinnamate film, as shown below. Figure 15 As shown. (Through) Figure 15 979cm can be observed -1 1171cm -1 1202cm -1 1281cm -1 1309cm -1 1449cm -1 1496cm -1 1577cm -1 1636cm -1 and 1709cm -1 The absorption peaks all correspond to the characteristic absorption peaks of polyvinyl cinnamate.

[0101] The spin-coated polyvinyl cinnamate film was irradiated with 254 nm ultraviolet light to induce a chemical cross-linking reaction within it. Atomic force microscopy infrared spectroscopy was then performed again, and the spectral data are as follows: Figure 16 As shown, the corresponding C=C double bond 1636 cm can be observed. -1The disappearance of the absorption peak at 1709 cm⁻¹ and the corresponding carbonyl group -1 The blue shift behavior of the absorption peak at that point demonstrates the accurate spectral detection capability of the synchronous acquisition device.

[0102] (3) Casting polystyrene-polymethyl methacrylate blend film

[0103] For atomic force microscopy infrared spectroscopy systems, nanoscale infrared imaging can be achieved. To verify this function, polystyrene-polymethyl methacrylate blend films were prepared by casting using ethyl acetate as a solvent. Infrared imaging was performed on the film surface at 1728 cm⁻¹. -1 (characteristic absorption peak of polymethyl methacrylate) and 1492 cm⁻¹ -1 Infrared imaging was performed on the characteristic absorption peaks of polystyrene, and the results are as follows: Figure 17 As shown, it can be observed that when imaging is performed at two different wavenumbers, the two phases present in the sample have strong absorption of infrared light of a single wavelength. The nanoscale phase separation behavior of the sample can be clearly distinguished from the imaging results, thus verifying the nano-infrared imaging function of the instrument.

[0104] For atomic force microscopy (AFM) infrared spectroscopy, since the AFM probe is used as the detector, traditional infrared spectroscopy is often required to confirm the sample state in actual sample testing. However, for more sensitive samples (such as those with photoinitiated reactions), this non-in-situ detection method cannot ensure experimental accuracy. Therefore, a combined technique is needed to acquire the total internal reflection (TIR) ​​infrared spectrum of the sample simultaneously with the AFM infrared spectrum. This embodiment, through the design of a synchronous acquisition device and optical path for AFM-TIR spectroscopy, combined with a self-developed data processing method, enables the in-situ, simultaneous acquisition of both infrared spectra of a single sample. Furthermore, this embodiment uses chloroauric acid solution to treat the zinc selenide prism to enhance the signal intensity and signal-to-noise ratio of the AFM infrared spectrum; that is, by using gold nanoparticles, the infrared absorption signal intensity of the sample is successfully enhanced. This allows the technology to be applied to the infrared detection of polymer ultrathin films, making it suitable for detecting polymer thin film samples commonly used in optoelectronic devices and other fields.

[0105] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0106] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A device for simultaneous acquisition of atomic force microscopy and total internal reflection infrared spectroscopy, characterized in that, The synchronous acquisition device includes an infrared laser source, a visible laser source, a beam combiner, an incident adjustment assembly, a prism, an atomic force microscope, a photothermal detector, and a processor; a sample is placed on the sample side of the prism; the tip of the atomic force microscope probe of the atomic force microscope is in contact with the sample; The beam combiner is used to combine the infrared laser emitted by the infrared laser source and the visible laser emitted by the visible laser source, so that the infrared laser and the visible laser are collinear, resulting in a collinear laser, and then incident the collinear laser onto the incident adjustment component; the collinear laser includes the infrared laser and the visible laser; The incident adjustment component is used to reflect the collinear laser, so that the collinear laser passes perpendicularly through the incident side of the prism and is focused onto the side of the sample, and the focal point of the collinear laser is located directly below the needle tip. The atomic force microscope is used to generate a microcantilever deflection signal of the microcantilever of the atomic force microscope probe after the collinear laser is focused onto the side of the sample; the microcantilever deflection signal is a curve showing the change of the deflection of the microcantilever over time. The photothermal detector is used to receive the reflected laser light emitted from the exit side of the prism and generate a reflected laser intensity signal; the reflected laser light is the laser light generated after the collinear laser light undergoes total internal reflection on the side of the sample; the reflected laser intensity signal is a curve showing the change of the laser intensity of the reflected laser light over time. The processor is communicatively connected to the atomic force microscope and the photothermal detector, respectively; the processor is used to process the microcantilever deflection signal and the reflected laser intensity signal to obtain the atomic force microscope infrared spectrum and total internal reflection infrared spectrum.

2. The synchronous acquisition device according to claim 1, characterized in that, The synchronous acquisition device further includes: a first reflector, a first variable aperture, a flipping component, and a second variable aperture; The first reflector is located between the infrared laser source and the beam combiner; the first reflector is used to reflect the infrared laser to the beam combiner. The beam combiner is used to combine the infrared laser and the visible laser to obtain a combined laser beam, and the combined laser beam is incident on the first variable aperture. The apertures of both the first and second variable apertures are at their minimum; the first variable aperture is used to transmit the combined laser beam to the flipping assembly. The flipping component is used to reflect the combined laser beam to the second variable aperture; The second variable aperture is used to transmit the combined laser beam to the photothermal detector; The photothermal detector is used to receive the combined laser beam and determine the first power of the infrared laser and the second power of the visible laser in the combined laser beam. The processor is used to adjust the position and angle of the first reflector according to the first power and the second power until both the first power and the second power reach their maximum values.

3. The synchronous acquisition device according to claim 2, characterized in that, The flipping assembly includes a flipping frame and a second reflector mounted on the flipping frame; the processor is controlled and connected to the flipping frame; when it is necessary to adjust the position and angle of the first reflector, the flipping frame is controlled to be in an open state, so that the combined laser beam is reflected to the second variable aperture; when it is necessary to obtain the infrared spectrum of the atomic force microscope and the total internal reflection infrared spectrum, the flipping frame is controlled to be in a closed state, so that the collinear laser beam is incident on the incident adjustment assembly.

4. The synchronous acquisition device according to claim 1, characterized in that, The incident adjustment assembly includes a three-axis displacement stage and an off-axis parabolic mirror mounted on the three-axis displacement stage; the off-axis parabolic mirror is used to reflect the collinear laser beam. The processor is connected to the three-axis displacement stage; the processor is used to control the movement of the three-axis displacement stage so that the collinear laser, after being reflected by the off-axis parabolic mirror, passes perpendicularly through the incident side and is focused onto the side of the sample, and the focal point of the collinear laser is located directly below the needle tip.

5. The synchronous acquisition device according to claim 1, characterized in that, The sample has gold nanoparticles on its side surface; the gold nanoparticles are obtained by in-situ growth after an aqueous solution of chloroauric acid is dropped onto the side surface of the sample.

6. The synchronous acquisition device according to claim 1, characterized in that, The angle between the sample side and the incident side is the same as the angle between the sample side and the exit side.

7. The synchronous acquisition device according to claim 2, characterized in that, The synchronous acquisition device also includes a plurality of third reflectors that are optically connected sequentially between the first variable aperture and the flipping component.

8. A method for simultaneous acquisition of atomic force microscopy and total internal reflection infrared spectroscopy, wherein the simultaneous acquisition device described in claim 1 is controlled to operate, characterized in that, The synchronization acquisition method includes: The microcantilever deflection signal generated by an atomic force microscope and the reflected laser intensity signal generated by a photothermal detector are acquired; the microcantilever deflection signal is the curve of the microcantilever deflection over time; the reflected laser intensity signal is the curve of the reflected laser intensity over time. The background signal from the infrared laser source is used to process the deflection signal of the microcantilever and the reflected laser intensity signal to obtain the infrared spectrum of the atomic force microscope and the total internal reflection infrared spectrum; the background signal is the curve of the laser intensity of the infrared laser as a function of wavenumber.

9. The synchronization acquisition method according to claim 8, characterized in that, The process of using the background signal from the infrared laser source to process the microcantilever deflection signal and the reflected laser intensity signal to obtain the atomic force microscope infrared spectrum and total internal reflection infrared spectrum specifically includes: The microcantilever deflection signal is demodulated using a reference signal to obtain the microcantilever amplitude signal; the reference signal is a signal with the same frequency as the pulse repetition frequency of the infrared laser source generated by the infrared laser source; the microcantilever amplitude signal is the curve of the microcantilever amplitude changing over time. The microcantilever amplitude signal is converted into a microcantilever amplitude wavenumber signal; the microcantilever amplitude wavenumber signal is the curve of the microcantilever amplitude versus wavenumber. Divide the wavenumber signal of the microcantilever amplitude by the background signal to obtain the infrared spectrum of the atomic force microscope. The reflected laser intensity signal is converted into a reflected laser intensity wavenumber signal; the reflected laser intensity wavenumber signal is the curve of the reflected laser intensity versus wavenumber. Dividing the reflected laser intensity wavenumber signal by the background signal yields the total internal reflection infrared spectrum.

10. The synchronous acquisition method according to claim 9, characterized in that, The method for determining the pulse repetition frequency of the infrared laser source includes: Under conditions where the sample is not irradiated by infrared laser, the background signal of the microcantilever deflection generated by atomic force microscopy is acquired; the background signal of the microcantilever deflection is subjected to FFT transformation to obtain the resonance frequency of the atomic force microscopy probe and the sample; the resonance frequency is set as the pulse repetition frequency of the infrared laser source.

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