A method of nanoscale infrared imaging

Abstract

The application discloses a method for nanoscale infrared imaging, which uses a phonon material as an imaging substrate, places a sample on the surface of the imaging substrate, and uses a photoinduced force microscope to perform infrared imaging. The nanoscale infrared imaging of materials with weak or no infrared absorption is realized by using the signal of the phonon substrate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of infrared spectroscopy and imaging, and particularly relates to a kind of nanoscale infrared contrast imaging using phonon imaging substrate. BACKGROUND

[0002] Nanoscale infrared imaging can provide nanomaterial electronic / vibration information with subwavelength spatial resolution, and plays an irreplaceable role in modern nanoscience and nanotechnology. Combined with synchronous atomic force microscope (AFM) imaging, nanoscale infrared can be used to analyze the composition and distribution of nanomaterials, and further explore the reaction mechanism and structure-function relationship. To realize nanoscale infrared imaging, the infrared wavelength is usually tuned to the vibration frequency of nanomaterials, and then the component distribution is distinguished by different light interactions in infrared images, which has been widely used in the fields of optics, material science, energy conversion and storage, and biological analysis.

[0003] However, this method is difficult to characterize ultrathin (<10 nm) nanomaterials or nanomaterials with weak infrared absorption cross section. The infrared signal of these materials is weak, usually below the detection limit of the instrument. In order to characterize these materials, the current methods mainly improve the surface electric field (E), including attenuated total reflection device, needle-metal gap device and resonant antenna. Using these methods, the sensitivity of nanoscale infrared imaging can be improved to the level of single molecular layer, however, these methods have poor applicability, and it is still necessary to develop a nanoscale infrared contrast imaging strategy with ultra-high sensitivity. SUMMARY

[0004] In view of the above problems of the prior art, the present application proposes a substrate-enhanced nanoscale infrared imaging strategy, which amplifies the feedback optical signal through the light-matter interaction between the substrate and the nanomaterials with different thickness and different refractive index to be imaged. It can be used to characterize the morphology, structure and chemical composition of ultrathin nanomaterials. The established nanoscale infrared imaging method can realize nanoscale resolution, and is expected to be used for identification and imaging of ultrathin nanomaterials or nanomaterials with weak absorption cross section, and to exceed the detection limit of existing nanoscale infrared imaging.

[0005] To achieve the above purpose, the present application adopts the following technical solution:

[0006] A method for nanoscale infrared imaging, using a phonon material as an imaging substrate, placing a sample on the surface of the imaging substrate, and using a photoinduced force microscope (PiFM) to perform infrared imaging.

[0007] Preferably, the infrared imaging is at the phonon vibration wavelength of the phonon material, wherein the area without sample loading forms a bright area with strong signal, and the area with sample loading forms a dark area with weak signal. The bright area and the dark area together form a high-contrast nanoscale infrared imaging.

[0008] Preferably, the phonon material is one of mica, quartz, boron nitride, silicon nitride, silicon dioxide, aluminum oxide, molybdenum trioxide or silicon carbide.

[0009] Preferably, the phonon material is mica, and the phonon vibration wavelength is 1200 cm -1 -870 cm -1 .

[0010] Preferably, the phonon material is quartz, and the phonon vibration wavelength is 1240 cm -1 -950 cm -1 .

[0011] Preferably, the phonon material is boron nitride, and the phonon vibration wavelength is 1600 cm -1 -1300 cm -1 .

[0012] Preferably, the phonon material is silicon nitride, and the phonon vibration wavelength is 1893 cm -1 -700cm -1 .

[0013] Preferably, the phonon material is silicon dioxide, and the phonon vibration wavelength is 1250 cm -1 -800cm -1 .

[0014] Preferably, the phonon material is aluminum oxide, and the phonon vibration wavelength is 2000 cm -1 -650cm -1 .

[0015] Preferably, the phonon material is molybdenum trioxide, and the phonon vibration wavelength is 1000 cm -1 -400cm -1 .

[0016] Preferably, the phonon material is silicon carbide, and the phonon vibration wavelength is 1064 cm -1 -625 cm -1

[0017] The thickness of the phonon material is any thickness, that is, any thickness of the phonon material as an imaging substrate can realize the present application.

[0018] Preferably, the surface of the phonon material is flat. The phonon material with a flat surface can have a uniform background infrared signal.

[0019] Preferably, the sample is a solid material. Any solid material can be imaged with high resolution by the method of the present application.

[0020] Preferably, the sample is a biological material such as a polymer, a nucleic acid, and a protein, an organic framework material, or a two-dimensional material.

[0021] Preferably, the thickness of the sample is 0-2000 nm. The method of the present application can be used to image samples of any thickness. For samples with a thickness of less than 10 nm, it is difficult to image the samples or the resolution of the images is low by using existing methods. The present application fills the technical gap in infrared imaging of thin samples.

[0022] The present application has the following advantages:

[0023] 1. The present application uses a phonon material as an imaging substrate, which can ensure that the substrate has a high infrared optical signal. In addition, a flat substrate can have a uniform background infrared signal.

[0024] 2. The present application uses a phonon crystal body signal and adopts a reverse imaging strategy, i.e., the sample forms a dark area and the substrate forms a bright area. Compared with using a molecular signal, the present application has a higher signal strength, can be adapted to a wider range of sample thicknesses, is especially suitable for thin samples, and can achieve higher sensitivity of infrared spectral detection.

[0025] 3. Since the reverse imaging strategy is adopted, the method of the present application can be used to achieve high-resolution infrared imaging of materials with weak infrared absorption or no infrared absorption.

[0026] 4. The present application can change the type, thickness, and other conditions of the substrate according to the need for signal enhancement at different wavelengths (such as obtaining the highest enhancement factor) to obtain a high-efficiency infrared enhancement effect.

[0027] 5. The vertical resolution of the present application can be less than 1 nm, and the horizontal resolution can be 2.6 nm.

[0028] 6. The method of the present application can be used to achieve internal imaging of materials, for example, to image irregular structures inside nanomaterials. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is the nanometer infrared spectral imaging of a polymer polydimethylsiloxane sample on a quartz surface.

[0030] Figure 2 is the nanometer infrared spectral imaging of a polymer polydimethylsiloxane sample on a mica surface.

[0031] Figure 3 is the nanometer infrared spectrum imaging of mica on the surface of quartz. Wherein a is the atomic force microscope topographic imaging of mica on the surface of quartz, b is the nanometer infrared imaging of quartz surface using quartz signal, c is the signal obtained along the arrow in figure a and figure b.

[0032] Figure 4 is the nanometer infrared spectrum imaging of DNA origami structure on the surface of mica.

[0033] Figure 5 is the nanometer infrared spectrum imaging of block copolymer nanostructure on the surface of quartz.

[0034] Figure 6 is the nanometer infrared spectrum imaging of polymer polydimethylsiloxane sample on the surface of ZnSe with a refractive index of 2.4. Wherein, a is the atomic force microscope imaging of polymer polydimethylsiloxane sample on the surface of ZnSe, b is the nanometer infrared imaging of polymer polydimethylsiloxane sample on the surface of ZnSe. DETAILED DESCRIPTION

[0035] Example 1

[0036] The imaging substrate of this embodiment is quartz and mica. The sample is a polymer polydimethylsiloxane sample on the surface of quartz and mica. Using light-induced force microscope, nanometer infrared imaging is carried out using tapping mode and sideband detection mode of the probe, and imaging and spectral scanning at different wavelengths are carried out on droplets with different thicknesses, and the results are shown in FIGS. Figure 1 and 2 , wherein, Figure 1 a and Figure 2 a are atomic force microscope topographic imaging of polydimethylsiloxane droplets on the surface of quartz and mica respectively, Figure 1 b and Figure 2 b are nanometer infrared imaging of polydimethylsiloxane droplets on the surface of quartz and mica respectively, Figure 1 c and Figure 2 c is the method described in the present application, i.e. nanometer infrared imaging using the signal of the imaging substrate quartz and the imaging substrate mica on the surface of quartz and mica respectively. It can be seen that when nanometer infrared imaging is carried out using the molecular signal of polydimethylsiloxane, the obtained infrared signal increases with the increase of sample thickness, showing a positive imaging result, while when nanometer infrared imaging is carried out using the signal of the imaging substrate of phonon material, the obtained infrared signal decreases with the increase of sample thickness, showing a negative imaging result. This embodiment shows that phonon material as imaging substrate can realize high molecular super-resolution infrared imaging.

[0037] Example 2

[0038] The imaging substrate of this embodiment is quartz. The sample is mica on the surface of quartz. Using light-induced force microscopy, using tapping mode and sideband detection mode of the probe, nanometer infrared imaging is carried out, and the mica is imaged at different wavelengths, and the results are shown in the accompanying Figure 3 Fig. 1a, wherein, Figure 3 a is the atomic force microscope topographic image of the mica on the surface of quartz, Figure 3 b is the method of the present application, i.e. nanometer infrared imaging of the mica on the surface of quartz using quartz signals. It can be seen that when nanometer infrared imaging is carried out using quartz signals, the obtained infrared signals decrease with the increase of the thickness of the mica, showing a negative imaging result, indicating that phonon materials as imaging substrate can realize super-resolution infrared imaging of two-dimensional materials. At the same time, Figure 3 c is Figure 3 a and Figure 3 b along the green arrow, it can be seen that using phonon signal imaging, a spatial resolution of 2.6 nm level can be obtained, which is the highest value of the current nanometer infrared spectrum.

[0039] Example 3

[0040] The imaging substrate of this embodiment is mica. The sample is DNA origami nanostructure on the surface of mica. Using light-induced force microscopy, using tapping mode and sideband detection mode of the probe, nanometer infrared imaging is carried out, and the DNA origami nanostructure is imaged at different wavelengths, and the results are shown in the accompanying Figure 4 Fig. 2a, wherein, Figure 4 a is the atomic force microscope topographic image of the DNA origami nanostructure on the surface of mica, Figure 4 b is the nanometer infrared imaging of the mica surface using neither the DNA origami signal nor the mica signal in the prior art. It can be seen that the absolute value and contrast of its signal are very poor, and the signal-to-noise ratio is very low. Figure 4 c is the nanometer infrared imaging of the mica surface using the DNA origami signal. It can be seen that due to the very low thickness of the DNA origami, the absolute value and contrast of its signal are still very poor. Figure 4 d is the method of the present application, i.e. nanometer infrared imaging of the mica surface using the mica signal. It can be seen that using phonon signal imaging, a higher signal-to-noise ratio and contrast than using DNA signal can be obtained, which can prove that phonon materials as imaging substrate can realize super-resolution infrared imaging of biological materials. At the same time, the imaging effect of the present application is more advantageous than the prior art using the signal of the molecule itself.

[0041] Example 4

[0042] The imaging substrate in this embodiment is quartz. The sample is a block copolymer nanostructure on the surface of quartz. Photoinduced force microscopy was used, employing tapping mode and probe sideband detection mode for nano-infrared imaging. The DNA origami nanostructure was imaged at different wavelengths, and the results are shown in the attached figure. Figure 5 As shown, where, Figure 5 a is an atomic force microscopy image of the block copolymer nanostructure on the quartz surface. Figure 5 b and c are nano-infrared images of quartz surfaces using block copolymer signals, respectively. Figure 5 d represents the method of this invention, namely, nano-infrared imaging using quartz signals on a quartz surface. It can be seen that using quartz signals on a quartz surface yields a negative imaging result, while using block copolymer signals yields a positive imaging result. This proves that phonon materials, as imaging substrates, can achieve block copolymer super-resolution infrared imaging. Simultaneously, from... Figure 5 In d, it can be observed Figure 5 The fact that damage inside the sample cannot be observed in ac indicates that this technique can achieve imaging of the internal structure of the sample.

[0043] Example 5

[0044] As a comparative example, the imaging substrate in this example is ZnSe with a refractive index of 2.4. The sample is a polymer polydimethylsiloxane sample. Nanoscale infrared imaging was performed using photoinduced force microscopy in tapping mode and probe sideband detection mode. The results are as follows: Figure 6 As shown, compared to Example 1, this example uses a substrate without phonon exciton vibrations, resulting in a forward-facing optical image. Furthermore, the signal variation, especially for samples with lower thicknesses, is significantly reduced compared to using phonon vibrations. This demonstrates that the method of the present invention outperforms imaging on the surface of ordinary optical media.

Claims

1. A method of nanoscale infrared imaging, characterized by, The irregular structure inside the nanomaterial is imaged by using a photo-induced force microscope to perform infrared imaging on the irregular structure inside the nanomaterial, and the infrared imaging is performed at a phonon vibration wavelength of the phonon material.

2. The method of claim 1, wherein, The phonon material is one of mica, quartz, boron nitride, silicon nitride, silicon dioxide, aluminum oxide, molybdenum trioxide or silicon carbide.

3. The method of claim 1, wherein, The phonon material is mica or quartz.

4. The method of claim 1, wherein, The region without loading the sample forms a bright region with a strong signal, and the region with loading the sample forms a dark region with a weak signal.

5. The method of claim 4, wherein, the phononic material is mica with a phononic vibrational wavelength of 1090 cm -1 -970 cm -1 ; or the phononic material is quartz with a phononic vibrational wavelength of 1140 cm -1 -1030 cm -1 ; or the phononic material is boron nitride with a phononic vibrational wavelength of 1600 cm -1 - 1300 cm -1 ; or the phononic material is silicon nitride with a phononic vibrational wavelength of 1893 cm -1 -700 cm -1 ; or the phononic material is silicon dioxide with a phononic vibrational wavelength of 1250 cm -1 -800 cm -1 ; or the phononic material is aluminum oxide with a phononic vibrational wavelength of 2000 cm -1 -650 cm -1 ; or the phononic material is molybdenum trioxide with a phononic vibrational wavelength of 1000 cm -1 -400 cm -1 ; or the phononic material is silicon carbide with a phononic vibrational wavelength of 1064 cm -1 -625 cm -1 .

6. The method of claim 1, wherein, The sample is a solid material.

7. The method of claim 6, wherein, The sample is a polymer, a biological material, an organic framework material or a two-dimensional material.

8. The method of claim 7, wherein, The biological material is a nucleic acid or a protein.

9. The method of claim 1, wherein, The surface of the phonon material is flat.

10. The method of claim 1, wherein, The thickness of the sample is 0-2000 nm.

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