A method and apparatus for testing interfacial water based on raman spectroscopy in z-direction with nanometer scale step

Abstract

The application discloses a method and device for testing interfacial water in a Z direction with nanometer scale step by Raman spectrum, and the method comprises the following steps: providing a bottom plate and an upper substrate on the top surface of the bottom plate, modifying the top surface of the bottom plate and the bottom surface of the upper substrate according to the interfacial type of the interfacial water to be tested; the left edge surface of the top surface of the bottom plate is attached to the left edge surface of the bottom surface of the corresponding upper substrate, and a partition is arranged between the top surface of the bottom plate and the bottom surface of the corresponding upper substrate; the partition forms a gap with increasing height between the top surface of the bottom plate and the bottom surface of the upper substrate; the water solution to be tested is added in the gap, the step length of the horizontal movement of the laser Raman is set, the Raman spectrum at different distances in the Z direction is obtained by detection, and the interfacial water condition at different distances in the Z direction is obtained by analysis. The method successfully analyzes the change of the interfacial water structure at different distances in the Z direction with nanometer scale for the first time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of Raman spectrum characterization of interfacial water, and particularly relates to a test method and device for testing interfacial water in a nanometer scale step test in a Z direction based on Raman spectrum. BACKGROUND

[0002] Several centuries ago, Paracelsus said, "water is the mother of the world and all living things". The interaction of water with the outside world is realized through the contact of "surface and interface", and the water / solid interface is an important place where many physical and chemical processes occur. Therefore, the research on the function and characteristics of interfacial water is the core of exploring the special physicochemical properties of water. However, the complex hydrogen bond interaction between water molecules and the interaction between water and the interface make the interfacial water structure extremely susceptible to the influence of the interface inhomogeneity and the local environment, so it is necessary to explore the hydrogen bond network and other microstructures of interfacial water from the molecular level.

[0003] Raman spectroscopy is an analytical technique based on the Raman scattering effect discovered by an Indian scientist (Raman) and applied to the study of molecular structure. In recent years, Raman spectroscopy has been widely used in the characterization of liquid water structure. With the development of surface-enhanced Raman technology and microscopic Raman imaging systems (laser confocal Raman spectrometer), Raman spectroscopy has shown its superiority in the study of interfacial water structure. For example, Li, C.-Y. et al. used in situ confocal laser Raman spectroscopy to study the interfacial water on the surface of Au single crystal electrode, revealing the changes in the hydrogen bond structure of the interfacial water in the double electric layer, and clarifying the basic understanding of the double electric layer and electrochemical processes at the interface (see: In situ probing electrified interfacial water structures at atomically flat surfaces. Nature Materials. 2019, 18(7), 697-701). Liu, D. et al. used Raman spectroscopy to study the interfacial water structure of sodium fluoride and sodium chloride aqueous solution, revealing that the deformation of the hydrogen bond network of the interfacial water of sodium fluoride and sodium iodide aqueous solution is closely related to the interfacial depth (see: Vibrational Spectroscopy of Aqueous Sodium Halide Solutions and Air-Liquid Interfaces: Observation of Increased Interfacial Depth. The Journal of Physical Chemistry B. 2004, 108(7), 2252-2260). However, due to the limitation of the spatial resolution of Raman spectroscopy (the spatial resolution of Raman is about 1 μm), direct analysis of the interfacial water in a confined space (nanoscale) cannot be achieved. In particular, the analysis and characterization of interfacial water at different distances in the Z direction in a confined space at the nanoscale cannot be achieved using conventional Raman spectroscopy. Therefore, we urgently need to develop a method based on Raman spectroscopy to test the interfacial water in the Z direction with nanoscale step testing. SUMMARY

[0004] The first object of the present application is to provide a test method for testing the interfacial water in the Z direction with nanoscale step testing based on Raman spectroscopy.

[0005] The second object of the present application is to provide a device for testing the interfacial water in the Z direction with nanoscale step testing based on Raman spectroscopy.

[0006] To achieve the above objects, the present application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a testing method for testing interfacial water in a nanometer scale step-by-step in the Z direction based on Raman spectroscopy, comprising the following steps:

[0008] 1) providing a bottom plate and an upper substrate on the top surface of the bottom plate, and independently modifying the top surface of the bottom plate and the bottom surface of the upper substrate according to the type of the interfacial water to be tested;

[0009] 2) the left edge surface of the top surface of the bottom plate is attached to the left edge surface of the bottom surface of the corresponding upper substrate to form an attached end, and the right edge surface of the top surface of the bottom plate and the right edge surface of the bottom surface of the corresponding upper substrate include a partition; the partition forms a gap between the top surface of the bottom plate and the bottom surface of the upper substrate, which gradually increases in height in the Z direction from left to right;

[0010] 3) adding the water solution to be tested in the gap, and contacting the water solution to be tested to the top surface of the bottom plate and the bottom surface of the upper substrate, then focusing the laser beam of the microscopic Raman imaging system to the attached end, and adjusting the objective lens to be clear in the field of view;

[0011] 4) setting the step length of the horizontal movement of the microscopic Raman imaging system, so that during the detection process, the laser beam of the microscopic Raman imaging system moves continuously in the horizontal direction with a certain step length, while the Z direction between the bottom plate and the upper substrate changes continuously with a nanometer step length, then the detection is carried out to obtain the Raman spectrum at different distances in the Z direction;

[0012] 5) comparing the peak intensities of the different configurations of interfacial water corresponding to the corresponding frequency shifts in the Raman spectra at different distances in the Z direction to obtain the content change of the different configurations of interfacial water at different distances in the Z direction.

[0013] It should be noted that conventional Raman spectroscopy technology cannot realize the analysis and characterization of interfacial water at different distances in a limited space in a nanometer scale, and the present application builds a device with a certain structure, so that the laser beam of the microscopic Raman imaging system moves continuously in the horizontal direction of the modified bottom plate / substrate with a certain step length, while the laser beam of the microscopic Raman imaging system also changes continuously in the Z direction between the bottom plate and the upper substrate with a nanometer step length. Then, according to the need, Raman spectra of different time ranges are collected to obtain Raman spectra at different distances in the Z direction, and by comparing the peak intensities of the different configurations of interfacial water corresponding to the corresponding frequency shifts in the different Raman spectra, the content change of the different configurations of interfacial water at different distances in the Z direction in a nanometer scale is obtained. The step value in the Z direction is mainly controlled by the angle value between the bottom plate and the upper substrate and / or the step length in the horizontal direction, for example, the step length in the horizontal direction is X, the angle between the bottom plate and the upper substrate is Y, and the step value in the Z direction can be calculated according to the trigonometric function and / or the Pythagorean theorem.

[0014] The Raman spectrum is a Raman spectrum curve automatically generated by a microscopic Raman imaging system, with Raman frequency shift as the horizontal coordinate and peak intensity as the vertical coordinate.

[0015] According to the specific embodiment of the present application, the length of the bottom plate is 10-50 mm; the length between the upper substrates is 10-50 mm; the height of the partition is 500-2000 nm; and the step value in the horizontal direction is 100-2000 μm.

[0016] The configuration of the interfacial water includes four-coordinated water molecules, unsaturated coordinated water molecules and free water; wherein the frequency shift values of the different configurations of the interfacial water can be analyzed from the collected Raman spectrum or obtained from the literature (see: Raman spectroscopic study of the effects of dissolved NaCl on water structure. Vibrational Spectroscopy 2012, 62, 110-114), generally, the frequency shift of the four-coordinated water molecules is 3200 cm -1 , the frequency shift of the unsaturated coordinated water molecules is 3400 cm -1 , and the frequency shift of the free water molecules is 3600 cm -1 .

[0017] Preferably, the length of the bottom plate and the upper substrate is consistent.

[0018] The modification treatment of the top surface of the bottom plate and the bottom surface of the upper substrate is determined according to the interfacial type of the interfacial water to be tested. For example, if the interfacial water structure of hydrophilic interface and hydrophobic interface needs to be studied, the bottom plate and the upper substrate can be optionally subjected to hydrophilic treatment and hydrophobic treatment, respectively; if the interfacial water structure of polymer interface and hydrophobic interface needs to be studied, the bottom plate and the upper substrate can be optionally subjected to polymer modification treatment and hydrophobic treatment, respectively; if the interfacial water structure between certain protein molecules needs to be studied, the bottom plate and the upper substrate both need to be subjected to protein molecule modification. The other surface of the bottom plate and the upper substrate can be subjected to modification treatment or not subjected to modification treatment, which does not interfere with the test.

[0019] According to the specific embodiment of the present application, the hydrophilic modification treatment is soaking treatment with an aiptasia solution (H2SO4:H2O2=7:3, v / v) for about half an hour, which completely removes the organic matter on the bottom plate or the upper substrate and generates hydroxyl groups on the surface, so that the surface is highly hydrophilic.

[0020] According to the embodiment of the present application, the hydrophobic modification treatment is a fluorosilane reaction on the surface of the lower substrate or the upper substrate after the hydrophilic modification treatment, so as to make the surface of the substrate hydrophobic.

[0021] According to the embodiment of the present application, the polymer modification treatment is a grafting of a silane coupling agent on the surface of the lower substrate or the upper substrate after the hydrophilic modification treatment, and then grafting the desired polymer molecules.

[0022] The solution to be tested is selected according to the type of the interface water to be explored. For example, if the interface water structure of pure water is to be tested, pure water is selected as the solution to be tested; if the interface water structure of a sodium chloride aqueous solution is to be tested, a sodium chloride aqueous solution is selected as the solution to be tested.

[0023] Further, in the above method, the height of the partition is 1 nanometer-1000 micrometers. The height is at least greater than the maximum distance in the Z direction to be measured. For example, if the maximum distance to be measured in the Z direction is 500 nanometers, the height of the partition is at least greater than 500 nanometers, and can be 800 nanometers, 1000 nanometers, 1200 nanometers, etc. In addition, the shape of the partition can be selected and adjusted by those skilled in the art according to the actual situation, for example: sphere, prism, pyramid, tube, etc. The structure of the partition can be fixed or a device with adjustable height.

[0024] Further, the upper substrate is light-transmitting; the lower substrate is non-light-transmitting; when the height of the partition is 1 nanometer-1 micrometer, the partition is light-transmitting or non-light-transmitting; when the height of the partition is 1 micrometer-1000 micrometers, the partition is light-transmitting.

[0025] Further, the modification treatment includes one of a hydrophilic modification treatment, a hydrophobic modification treatment, an organic macromolecule modification treatment, an organic group modification treatment, and a polymer modification treatment.

[0026] Further, the organic group includes a carboxyl group and / or a carbon chain.

[0027] Further, the material of the upper substrate is selected from a light-transmissive inorganic material, a light-transmissive organic material, or a light-transmissive organic / inorganic composite material; the material of the bottom substrate is selected from a non-light-transmissive inorganic material, a non-light-transmissive organic material, or a non-light-transmissive organic / inorganic composite material; when the height of the partition is 1 nanometer-1 micrometer, the material of the partition is selected from a light-transmissive inorganic material, a light-transmissive organic material, a light-transmissive organic / inorganic composite material, a non-light-transmissive inorganic material, a non-light-transmissive organic material, or a non-light-transmissive organic / inorganic composite material; when the height of the partition is 1 micrometer-1000 micrometers, the material of the partition is selected from a light-transmissive inorganic material, a light-transmissive organic material, or a light-transmissive organic / inorganic composite material.

[0028] Preferably, the light-transmissive inorganic material is quartz or glass.

[0029] Preferably, the non-light-transmissive inorganic material is silicon.

[0030] Preferably, the light-transmissive organic material includes a light-transmissive organic polymer material, such as polymethyl methacrylate.

[0031] Further, the parameters of the micro-Raman imaging system include: an excitation wavelength of 514 nm, 532 nm, or 633 nm; a laser relative intensity of 20%-100%; a test wave number of 2500-4000 cm -1 ; a microscope objective of 20 times, 50 times, or 80 times. Preferably, the excitation wavelength is 532 nm, the laser relative intensity is 50%, and the microscope objective is 50 times.

[0032] Further, the method further includes baseline adjustment, smoothing processing, and normalization processing on the Raman spectrum obtained in step (4).

[0033] In a second aspect, the present application provides a device for the above-mentioned testing method. The device includes a bottom substrate and an upper substrate on the top surface of the bottom substrate; the left edge surface of the top surface of the bottom substrate is attached to the left edge surface of the bottom surface of the corresponding upper substrate to form an attached end; the right edge surface of the top surface of the bottom substrate and the right edge surface of the bottom surface of the corresponding upper substrate include a partition; the partition forms a gap between the top surface of the bottom substrate and the bottom surface of the upper substrate, which gradually increases in the Z direction from left to right (as shown in Figure 1 ; the top surface of the bottom substrate and the bottom surface of the upper substrate are independently subjected to a modification treatment; preferably, the modification treatment includes one of hydrophilic modification treatment, hydrophobic modification treatment, organic macromolecule modification treatment, organic group modification treatment, and polymer modification treatment.

[0034] Further, the height of the partition is 1 nanometer-1000 micrometers.

[0035] Further, the upper substrate is light-transmissive; the bottom substrate is non-light-transmissive; the partition has a height of 1 nm-1 μm and is light-transmissive or non-light-transmissive; the partition has a height of 1 μm-1000 μm and is light-transmissive.

[0036] Further, the material of the upper substrate is selected from light-transmissive inorganic material, light-transmissive organic material or light-transmissive organic / inorganic composite material; when the height of the partition is 1 nm-1 μm, the material of the partition is selected from light-transmissive inorganic material, light-transmissive organic material, light-transmissive organic / inorganic composite material, non-light-transmissive inorganic material, non-light-transmissive organic material or non-light-transmissive organic / inorganic composite material; when the height of the partition is 1-1000 μm, the material of the partition is selected from light-transmissive inorganic material, light-transmissive organic material or light-transmissive organic / inorganic composite material.

[0037] The material of the bottom substrate is selected from non-light-transmissive inorganic material, non-light-transmissive organic material or non-light-transmissive organic / inorganic composite material.

[0038] Preferably, the light-transmissive inorganic material is quartz or glass.

[0039] Preferably, the non-light-transmissive inorganic material is silicon.

[0040] Preferably, the light-transmissive organic material includes light-transmissive organic polymer material, such as polymethyl methacrylate.

[0041] It is additionally noted that any range recited herein includes the end values and any numerical value between the end values and any subrange between any numerical value in the range.

[0042] Advantages of the present application

[0043] The present application provides a method for testing interface water by Raman spectroscopy in the Z direction with nanometer scale step testing, which successfully analyzes the content change of different configuration interface water at different distances in the Z direction through Z direction nanometer scale step testing.

[0044] The method for testing interface water by Raman spectroscopy in the Z direction with nanometer scale step testing provided by the present application can also be used for the research of interface water at different distances in the Z direction in other limited spaces. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The structure schematic diagram of the device for testing in the Z direction with nanometer scale step testing based on Raman spectroscopy is shown;

[0046] Figure 2A structural schematic diagram of a nanometer scale step testing device in the Z direction based on Raman spectrum of Example 1 is shown.

[0047] Figure 3 A Raman spectrum of the interface water of different configurations at different distances in the Z direction obtained by Example 1 is shown. DETAILED DESCRIPTION

[0048] The application will be described in detail below by examples. It is necessary to point out here that the examples are only used to further illustrate the application and cannot be understood as limiting the protection scope of the application. Those skilled in the art can make some non-essential improvements and adjustments according to the above content of the application. In the case of no conflict, the examples in the application and the features in the examples can be combined with each other.

[0049] The Raman spectrometer used in the following examples is an inVia-Qontor high spectral resolution analytical grade microscopic Raman imaging system of Renishaw Company.

[0050] Example 1

[0051] 1) Select a quartz piece and a silicon piece with a length of 20 mm and a width of 10 mm as the upper substrate and the bottom plate respectively, and modify the two; the modification process specifically includes the following steps:

[0052] Soak the quartz piece and the silicon piece in an arapaima solution (H2SO4:H2O2=7:3, v / v) for about half an hour, completely remove the organic matter on the quartz piece and the silicon piece and generate hydroxyl groups on the surface to make the surface highly hydrophilic; after the hydrophilic treatment, the quartz piece and the silicon piece are grafted with silane coupling agent, and then DNA molecules with a base number of 53 are grafted.

[0053] 2) Build the device: first stack the modified quartz piece and the silicon piece, then add about 0.5 μL of ethanol dispersion solution of silicon powder with a diameter of about 1 μm to one end, the left edge surface of the bottom surface of the quartz piece and the left edge surface of the top surface of the silicon piece are attached to form an attached end, and the silicon powder forms a gap between the top surface of the silicon piece and the bottom surface of the quartz piece with a height increasing in the range of 0-1000 nm;

[0054] 3) Add about 10 μL of sodium chloride aqueous solution to the gap to cover the top surface of the silicon piece and contact the bottom surface of the quartz piece, and then place it on the test platform of the microscopic Raman imaging system, focus the laser beam of the microscopic Raman imaging system to the attached end of the silicon piece, and adjust the objective lens to be clear;

[0055] 4) Set the excitation wavelength of the microscopic Raman imaging system to 532 nm, the relative intensity of the laser to 50%, and the test wave number to 2500-4000 cm -1, the microscope objective is 50 times, and the step length of the horizontal movement of the Raman laser is 1mm, so that the Raman spectrum data in the Z direction between the two modified surfaces are collected with a step length of 50nm, and the device structure diagram in the specific operation is shown in Figure 2 ;

[0056] 5) The laser beam of the micro-Raman imaging system is continuously moved in the horizontal direction from the bonding end of the silicon wafer to the spaced end, and the Raman spectrum at different distances in the Z direction is obtained;

[0057] 6) The Raman spectrum measured in step 5) is respectively subjected to baseline adjustment, smoothing processing, and spectrum peak fitting by using WiRE to obtain the Raman spectrum of the interfacial water at different distances in the Z direction, and the Raman spectrum peak intensity of the interfacial water is normalized and then analyzed, so that the interfacial water at different distances (50nm, 100nm and 300nm) in the Z direction can be obtained.

[0058] Analysis result: according to the Raman frequency shift 3200cm -1 , 3400cm -1 , 3600cm -1 , the peaks are divided, 3200cm -1 is a four-coordinated water molecule, and the other two frequency shift positions are other types of water molecules, wherein 3400cm -1 is an unsaturated coordinated water molecule, and 3600cm -1 is free water. Figure 3 It can be known that the specific change of the interfacial water structure at different distances in the Z direction of the modified quartz plate and the silicon wafer, for example, the content of the four-coordinated water molecule at 100nm in the Z direction is greater than that at 50nm and 300nm in the Z direction.

[0059] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not a limitation on the embodiments of the present application. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description, and it is impossible to enumerate all the embodiments here. Any obvious changes or variations derived from the technical solutions of the present application still fall within the protection scope of the present application.

Claims

1. A method of testing interfacial water based on Raman spectroscopy in the Z direction with nanometer scale steps, characterized by, The method comprises the following steps: 1) providing a bottom plate and an upper substrate on the top surface of the bottom plate, and modifying the top surface of the bottom plate and the bottom surface of the upper substrate independently according to the interface type of the interface water to be tested; 2) the left edge surface of the top surface of the bottom plate is attached to the left edge surface of the bottom surface of the corresponding upper substrate to form an attached end, and the right edge surface of the top surface of the bottom plate and the right edge surface of the bottom surface of the corresponding upper substrate comprise a partition; the partition forms a gap between the top surface of the bottom plate and the bottom surface of the upper substrate, and the height of the gap increases gradually in the Z direction from left to right; 3) adding the water solution to be tested in the gap, and making the water solution to be tested contact the top surface of the bottom plate and the bottom surface of the upper substrate, then focusing the laser beam of the microscopic Raman imaging system to the attached end, and adjusting the objective lens to the clear field of view; 4) setting the step length of the horizontal movement of the microscopic Raman imaging system, so that during the detection process, the laser beam of the microscopic Raman imaging system moves continuously in the horizontal direction with a certain step length, and at the same time, the Z direction between the bottom plate and the upper substrate changes continuously with a step length of nanometer level, then the detection is carried out, and the Raman spectrum at different distances in the Z direction is obtained; 5) comparing the peak intensities of different configuration interface water corresponding to the corresponding frequency shift in the Raman spectrum at different distances in the Z direction, to obtain the content change of the interface water of different configurations at different distances in the Z direction.

2. The method of claim 1, wherein, The height of the partition is 1 nanometer-1000 micrometers.

3. The method according to claim 1 or 2, characterized in that, The upper substrate is light-transmitting; the bottom plate is non-light-transmitting; when the height of the partition is 1 nanometer-1 micrometer, the partition is light-transmitting or non-light-transmitting; when the height of the partition is 1 micrometer-1000 micrometers, the partition is light-transmitting.

4. The method of claim 1, wherein, The modification treatment comprises one of hydrophilic modification treatment, hydrophobic modification treatment, organic macromolecule modification treatment, organic group modification treatment and polymer modification treatment; the organic group modification treatment comprises carboxyl modification treatment and / or carbon chain modification treatment.

5. The method of claim 1, wherein, The material of the upper substrate is selected from light-transmitting inorganic material, light-transmitting organic material or light-transmitting organic / inorganic composite material; when the height of the partition is 1 nanometer-1 micrometer, the material of the partition is selected from one of light-transmitting inorganic material, light-transmitting organic material, light-transmitting organic / inorganic composite material, non-light-transmitting inorganic material, non-light-transmitting organic material or non-light-transmitting organic / inorganic composite material; when the height of the partition is 1 micrometer-1000 micrometers, the material of the partition is selected from light-transmitting inorganic material, light-transmitting organic material or light-transmitting organic / inorganic composite material; The material of the bottom plate is selected from non-light-transmitting inorganic material, non-light-transmitting organic material or non-light-transmitting organic / inorganic composite material.

6. The method of claim 1, wherein, The parameters of the microscopic Raman imaging system include: excitation wavelength is 514 nm, 532 nm or 633 nm; laser relative intensity is 20%-100%; test wave number range is 2500-4000cm -1 ; microscope objective is 20 times, 50 times or 80 times.

7. The method of claim 1, wherein, The method further comprises baseline adjustment, smoothing treatment and normalization treatment on the Raman spectrum obtained in step (4).

8. A device for use in the test method of any one of claims 1 to 7, characterized in that The device comprises a bottom plate and an upper substrate on the top surface of the bottom plate; the left edge surface of the top surface of the bottom plate is attached to the left edge surface of the bottom surface of the corresponding upper substrate to form an attached end; the right edge surface of the top surface of the bottom plate and the right edge surface of the bottom surface of the corresponding upper substrate comprise a partition; the partition forms a gap between the top surface of the bottom plate and the bottom surface of the upper substrate, which gradually increases in height in the Z direction from left to right; the top surface of the bottom plate and the bottom surface of the upper substrate are each independently subjected to a modification treatment; The modification treatment comprises one of hydrophilic modification treatment, hydrophobic modification treatment, organic macromolecule modification treatment, organic group modification treatment and polymer modification treatment.

9. The apparatus of claim 8, wherein, The height of the partition is 1 nanometer-1000 microns; the upper substrate is light-transmissive; the bottom plate is non-light-transmissive; when the height of the partition is 1 nanometer-1 micron, the partition is light-transmissive or non-light-transmissive; when the height of the partition is 1 micron-1000 microns, the partition is light-transmissive.

10. The apparatus of claim 8, wherein, The material of the upper substrate is selected from light-transmissive inorganic material, light-transmissive organic material or light-transmissive organic / inorganic composite material; when the height of the partition is 1 nanometer-1 micron, the material of the partition is selected from one of light-transmissive inorganic material, light-transmissive organic material, light-transmissive organic / inorganic composite material, non-light-transmissive inorganic material, non-light-transmissive organic material or non-light-transmissive organic / inorganic composite material; when the height of the partition is 1 micron-1000 microns, the material of the partition is selected from light-transmissive inorganic material, light-transmissive organic material or light-transmissive organic / inorganic composite material; The material of the bottom plate is selected from non-light-transmissive inorganic material, non-light-transmissive organic material or non-light-transmissive organic / inorganic composite material.

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