AU2021103510A4 - Tip-Enhanced Raman Spectral Microscopic Imaging Device - Google Patents
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
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- G01N21/658—Raman scattering enhancement Raman, e.g. surface plasmons
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Abstract
Disclosed is a tip-enhanced Raman spectral microscopic imaging device, comprising an
exciting light unit (10), configured to generate a radially polarized light beam; a surface
plasmon polariton exciting unit (20), configured to receive the radially polarized light beam
and excite surface plasmon polaritons; a scanning unit (40) which comprises a scanning
probe (401) able to be hybridized with the surface plasmon polaritons to form a surface
plasmon polariton field hybridization unit (30); wherein the exciting light unit (10), a
measurement unit (50) and the scanning unit (40) are all connected to a monitor unit (60). By
using the radially polarized light beam to excite and generate the surface plasmon polaritons
that are focused to generate the surface plasmon polariton virtual probe, and using a gap
structure formed between the scanning probe (401) and the surface plasmon polaritons to
realize hybridization with the surface plasmon polaritons so as to form the surface plasmon
polariton field hybridization unit (30), an enhanced surface localized electric field is realized
and an enhanced Raman spectral signal of the sample to be measured is obtained, and the
measured Raman spectrum can be utilized to further realize microscopic imaging of the
sample.
Description
Description
TIP-ENHANCED RAMAN SPECTRAL MICROSCOPIC IMAGING DEVICE Technical Field The present application relates to the technical field of microscopic spectral imaging devices, and particularly relates to a tip-enhanced Raman spectral microscopic imaging device.
Background Raman spectrum is a common spectral analysis method for measuring molecular chemical bond, symmetry, or other chemical ingredient and structural information of samples, which can provide fast, simple, repeatable and non-invasive analysis, both qualitatively and quantitatively.
Tip-Enhanced Raman Spectroscope (TERS) technology is a combination of Scanning Probe Microscopy (SPM) technology and Raman Spectrum technology. The TERS technology can meet the requirements for analyzing chemical substances on a surface interface in nanoscience and nanotechnology, and has high spatial resolution and significant enhancement effect on the molecular Raman signal. Its principle is that, by using an SPM control system to put an Ag or Au probe tip having a curvature radius of tens of nanometers at a distance (e.g., 1nm) very close to the sample, when the incident light with a suitable wavelength irradiates the probe tip, the probe tip is excited by laser and generates localized surface plasmon resonance under a physical mechanism of lightning rod effect, causing intensive enhancement of localized electromagnetic field in a range of several nanometers to tens of nanometers in the vicinity of the probe tip, and at this time, the metal probe tip can be considered as a nano light source with very high power density, which can dramatically enhance the Raman signal of molecules adsorbed on the base or substrate right under the probe tip. The high spatial resolution chemical ingredient imaging by the TERS technology would provide strong technical support for solving many important scientific problems in the unimolecular science, such as acquiring information of morphology and chemical bond of a single molecule, and it also has advantages such as non-marking, in-situ, real-time, and fast acquisition of biomass information.
Surface Plasmon Polaritons (SPP) are electromagnetic waves constrained on an interface between metal and dielectric material or on a surface of metal film, formed by mutual coupling resonance of free electrons and incident photons at the metal surface, which can localize massive light wave energy on the interface between metal and dielectric material, thereby forming a very strong near-field enhancement effect.
According to differences in the relative positions of the laser beam and the probe tip, the TERS technology is classified into three typical illumination modes, namely, a Side Illumination Mode (the laser source irradiates the probe tip from a lateral side of the probe at a certain angle), a Top Illumination Mode (the laser source irradiates the probe tip from a top of the probe) and a Bottom Illumination Mode (the laser source irradiates the probe tip from a bottom of the probe).
Both the Side Illumination Mode and the Top Illumination Mode have limitations of working distance, and cannot use an object lens whose numerical aperture is too large, so their direction of enhancement of the spectral signal is limited; the Bottom Illumination Mode can use an object lens having a large numerical aperture to increase the incident optical field strength so as to enhance the spectral signal, but usually only for a transparent sample, while a non-transparent sample would lower the emitting light intensity of laser, and thus adversely affect the strength of the spectral signal.
The existing tip-enhanced Raman spectral microscopic imaging devices usually comprise a laser source, a scanning probe microscope, a microscopic imaging system and a spectrograph, and by using the laser source to irradiate the probe tip of the scanning probe of the scanning probe microscope, so as to excite surface plasmon polaritons, using the spectrograph to measure the Raman spectral signal and scanning and imaging the Raman spectrum, and using the microscopic imaging system to scan and image the sample, it can be known whether the Raman spectral signal of the sample is enhanced, as well as to what extent the signal is enhanced. Because the strength of the Raman spectral signal depends on the incident optical field strength and the surface plasmon polaritons, usually, a first approach is to use an object lens having a large numerical aperture to increase the incident optical field strength; a second approach is to use a Gap structure formed between a metal film and the probe tip of the scanning probe to enhance the Raman spectral signal. However, the first approach only works for a transparent sample, but the incident optical field strength would be lowered for a non-transparent sample; although the second approach may solve the problem of the incident optical field strength being lowered due to a non-transparent sample, the acquired strength of the Raman spectral signal remains to be further improved.
Summary of the Invention A technical problem to be solved by the present application is that the Raman spectral microscopic imaging devices in prior art has relatively low strength of Raman spectral signal, so it is needed to provide a tip-enhanced Raman spectral microscopic imaging device with high strength of Raman spectral signal and high spatial resolution.
To this end, the present application provides tip-enhanced Raman spectral microscopic imaging device comprising: an exciting light unit, configured to generate a radially polarized light beam to enter a surface plasmon polariton exciting unit which is configured to receive the radially polarized light beam and excite surface plasmon polaritons; a scanning unit, comprising a scanning probe able to be hybridized with the surface plasmon polaritons to form a surface plasmon polariton field hybridization unit; a measurement unit, configured to measure a Raman spectrum of a sample to be measured and perform scanning and imaging; a monitor unit, configured to display the Raman spectrum of the sample to be measured and perform imaging according to a characteristic spectrum of the sample to be measured; wherein the exciting light unit and the measurement unit are both connected to the monitor unit, and the scanning unit is sequentially connected to the measurement unit and the monitor unit.
Optionally, in the tip-enhanced Raman spectral microscopic imaging device, the surface plasmon polariton exciting unit comprises: an object lens; and a metal film coated on the object lens; wherein, the radially polarized light beam that enters the metal film excites and generates the surface plasmon polaritons that are focused to generate a surface plasmon polariton virtual probe, and the surface plasmon polariton virtual probe is hybridized with the scanning probe to form the surface plasmon polariton field hybridization unit.
Optionally, in the tip-enhanced Raman spectral microscopic imaging device, the metal film has a thickness of 40-50nm, and the object lens has a numerical aperture greater than 1.45.
Optionally, in the tip-enhanced Raman spectral microscopic imaging device, a gap is formed between the scanning probe and the metal film, and the gap is smaller than 10nm.
Optionally, in the tip-enhanced Raman spectral microscopic imaging device, the exciting light unit comprises: a laser element, configured to generate a laser beam with a preset wavelength; and a polarizing element, a collimating element and a vortex wafer arranged in sequence between the laser element and the object lens in an optical path output direction of the laser beam; wherein, the laser beam, after passing the polarizing element, the collimating element and the vortex wafer, is converted into the radially polarized light beam and enters the object lens.
Optionally, in the tip-enhanced Raman spectral microscopic imaging device, the collimating element is a lens group, and the radially polarized light beam is outputted as parallel light after passing the lens group.
Optionally, in the tip-enhanced Raman spectral microscopic imaging device, the surface plasmon polariton exciting unit further comprises: a beam splitting element, arranged between a beam incident end of the object lens and a beam emitting end of the vortex wafer, and configured to transmit the radially polarized light beam to the object lens to excite and generate the surface plasmon polaritons on the metal film.
Optionally, in the tip-enhanced Raman spectral microscopic imaging device, the beam splitting element is a beam splitting mirror or a dichroic mirror.
Optionally, in the tip-enhanced Raman spectral microscopic imaging device, the measurement unit comprises: an optical filter element; a spectrograph; and a CCD image sensor; wherein the optical filter element, the spectrograph and the CCD image sensor are connected to the beam splitting element through a horizontal straight line optical path; Raman scattered light of the sample to be measured, after being coupled by the object lens, is converted into coupled light and reflected to the beam splitting element, enters the spectrograph and the CCD image sensor after being transmitted through the optical filter element; and the monitor unit displays the Raman spectrum of the sample to be measured and performs imaging according to the characteristic spectrum thereof.
Optionally, in the tip-enhanced Raman spectral microscopic imaging device, the scanning probe is a probe coated with a metal film.
The technical solutions of the present application have the following advantages: 1. The tip-enhanced Raman spectral microscopic imaging device provided by the present application comprises an exciting light unit, a surface plasmon polariton exciting unit, a surface plasmon polariton field hybridization unit, a scanning unit, a measurement unit and a monitor unit, wherein the exciting light unit generates a radially polarized light beam to enter the surface plasmon polariton exciting unit so as to excite surface plasmon polaritons that are focused to generate a surface plasmon polariton virtual probe, the scanning unit comprises a scanning probe, the surface plasmon polariton virtual probe is hybridized with the scanning probe, i.e., by coupled oscillation, and an enhanced surface localized field strength is obtained in a gap structure formed between the scanning probe and the surface plasmon polariton unit, the combined action of the surface plasmon polariton virtual probe and the scanning probe enhances the surface localized electric field to acquire enhanced Raman spectral signal, the exciting localized field strength is enhanced, and the sample to be measured is excited to generate surface-enhanced Raman scattering.
2. The tip-enhanced Raman spectral microscopic imaging device provided by the present application uses a metal film having a thickness of 40-50nm, uses an object lens having a numerical aperture (NA) greater than 1.45 to make the light intensity larger for the incident light that enters the sample to be measured, causes the exciting light to pass the object lens and enter the metal film to excite and generate surface plasmon polaritons that are focused to form a surface plasmon polariton virtual probe, and controls the gap structure between the scanning probe and the metal film to be smaller than 10nm, so that the surface plasmon polariton virtual probe undergoes a hybridization effect in the gap structure, the exciting localized field strength is enhanced, the enhanced surface localized field strength leads to enhanced Raman spectral signal, and meanwhile the spatial resolution of the scanning probe detection is also increased.
3. In the tip-enhanced Raman spectral microscopic imaging device provided by the present application, the scanning probe is a probe coated with a metal film, a laser element generates a radially polarized light beam to enter the object lens and excite the metal film of the object lens to generate surface plasmon polaritons that are focused to form a surface plasmon polariton virtual probe, and the surface plasmon polaritons is hybridized by the gap structure formed by the metal probe, thereby enhancing the strength of the Raman spectral signal.
Brief Description of the Drawings In order to more clearly describe the technical solutions in the specific embodiments of the present application or in the prior art, hereinafter, the appended drawings used for describing the specific embodiments or the prior art will be briefly introduced. Apparently, the appended drawings described below are only some embodiments of the present application, and for a person with ordinary skill in the art, without expenditure of creative labor, other drawings can be derived on the basis of these appended drawings.
FIG. 1 is a structural diagram of a tip-enhanced Raman spectral microscopic imaging device in an embodiment of the present application; FIG. 2 is a structural diagram of the exciting light unit and the surface plasmon polariton exciting unit of the tip-enhanced Raman spectral microscopic imaging device in an embodiment of the present application; FIG. 3 is an optical path diagram of the tip-enhanced Raman spectral microscopic imaging device in an embodiment of the present application; FIG. 4 shows a Raman spectrogram of analyzing a sample to be measured by using an embodiment of the present application and a Raman spectrogram of analyzing a sample to be measured by only using a surface plasmon polariton virtual probe obtained from the metal film; FIG. 5 shows a Raman spectrogram of analyzing a sample to be measured by using a conventional Raman spectral microscopic imaging device in prior art and a Raman spectrogram of analyzing a sample to be measured by using a microscopic imaging device having no virtual probe or scanning probe; FIG. 6 shows a microscopic image of the spatial distribution of a standard sample of carbon nanotube scanned by a scanning probe; FIG. 7 shows the resolution of a profile distribution along the dotted line in FIG. 6; FIG. 8 shows the spatial resolution of measuring a sample to be measured by using an embodiment of the present application; FIG. 9 shows Raman spectrograms of the standard sample of carbon nanotube.
Reference signs: 10-exciting light unit; 101-laser element; 102-polarizing element; 103-collimating element; 1031-first convex lens; 1032-second convex lens; 104-vortex wafer; 20-surface plasmon polariton exciting unit; 201-beam splitting element; 202-object lens; 30-surface plasmon polariton field hybridization unit; 40-scanning unit; 401-scanning probe; 50-measurement unit; 501-optical filter element; 5011-first optical filter; 5012-second optical filter; 502-spectrograph; 503-CCD image sensor; 60-monitor unit; 70-illumination unit.
Detailed Description of Embodiments A clear and complete description of the technical solution of the present application is given below, in conjunction with the appended drawings. Apparently, the described embodiments are part of, but not all of, the embodiments of the present application. All the other embodiments, obtained by a person with ordinary skill in the art on the basis of the embodiments in the present application without expenditure of creative labor, belong to the protection scope of the present application.
Embodiment 1 A tip-enhanced Raman spectral microscopic imaging device of this embodiment, as shown in FIG. 1 to FIG. 9, comprises an exciting light unit 10, a surface plasmon polariton exciting unit 20, a surface plasmon polariton field hybridization unit 30, an illumination unit 70, a scanning unit 40, a measurement unit 50 and a monitor unit 60; the exciting light unit 10 is configured to generate a radially polarized light beam to enter the surface plasmon polariton exciting unit 20; the surface plasmon polariton exciting unit 20 is configured to receive the radially polarized light beam and excite surface plasmon polaritons by utilizing the energy of the radially polarized light beam as the radially polarized light beam irradiates thereon; the scanning unit 40 comprises a scanning probe 401; the scanning probe 401 is configured to scan a sample to be measured, and is also configured to be hybridized with the surface plasmon polaritons to form the surface plasmon polariton field hybridization unit 30, there is a gap structure (not shown) between the scanning probe and the surface plasmon polaritons, which is an ordinary Gap structure in the art, and the surface plasmon polariton field hybridization unit, being a surface-enhanced localized field formed in the gap structure, utilizes a hybridization effect to enhance the Raman spectral signal of the sample to be measured; the measurement unit 50 is configured to measure a Raman spectrum of the sample to be measured and perform scanning and imaging; the monitor unit 60 is configured to display an image of the Raman spectrum of the sample to be measured; the exciting light unit 10 and the measurement unit 50 are both connected to the monitor unit 60, and the scanning unit 40 is sequentially connected to the measurement unit 50 and the monitor unit 60; the illumination unit 70 is arranged under a bottom of the surface plasmon polariton exciting unit 20, and is configured to illuminate the sample to be measured.
It is found out by the inventors through research that, the enhancement effect of the hybridization phenomenon of the surface plasmon polariton field hybridization unit 30 on the detected spectral signal depends on the following several factors: the thickness of the metal film, which affects the intensity of the surface plasmon polaritons generated by excitation on the metal film, as well as whether or not such surface plasmon polaritons can be generated by excitation; the numerical aperture of the object lens, which affects the incident strength of the radially polarized light, and in turn affects the intensity of the surface plasmon polaritons generated by excitation on the metal film; the gap structure between the scanning probe 401 and the metal film, which affects the surface localized field strength, and in turn affects the strength of the Raman spectral signal associated with the surface localized field strength.
The surface plasmon polariton exciting unit 20 comprises an object lens 202 and a metal film coated on the object lens 202, specifically, the metal film is coated on a glass layer of the object lens 202, and the thickness of this metal film is optionally 40-50nm, preferably 45nm; it also comprises a beam splitting element 201 arranged at a beam incident end of the object lens 202, i.e., at a bottom side thereof as shown in FIG. 3, specifically, the beam splitting element 201 is arranged between the beam incident end of the object lens 202 and the vortex wafer 104, and is configured to reflect the radially polarized light beam generated by the exciting light unit 10 to the object lens 202, wherein the radially polarized light beam passes the object lens and irradiates the metal film to excite and generate surface plasmon polaritons that are focused to generate a surface plasmon polariton virtual probe. Specifically, the object lens 202 is a high numerical aperture object lens, and the numerical aperture (NA) thereof needs to be greater than 1.45, for example, an object lens having a numerical aperture NA=1.49, or an object lens having a numerical aperture NA=1.70. It is found out by the inventors through experimental research that the numerical aperture of the object lens 202 has a big influence on the generating of surface plasmon polaritons, when measured in a liquid environment, the existing high numerical aperture object lens (NA=1.25) cannot generate surface plasmon polaritons by polarized light beam exciting, and a numerical aperture NA>1.45 is required to effectively excite and generate surface plasmon polaritons, and under special circumstances, even an object lens with a numerical aperture NA>1.70 is required. For example, the tip-enhanced Raman spectral microscopic imaging device of the present application uses an object lens having a numerical aperture NA=1.49, the radially polarized light beam generated by the exciting light unit is reflected by the beam splitting element to the object lens 202 and then enters the sample to be measured, so as to excite on the metal film and generate surface plasmon polaritons that are focused to produce a surface plasmon polariton virtual probe.
In order to be able to allow the tip-enhanced Raman spectral microscopic imaging device of the present application to have relatively high signal, it is found out by the inventors through research that the thickness of the metal film has very important influence on the generating of surface plasmon polaritons, wherein, if the thickness of the metal film is too thin, surface plasmon polaritons cannot be generated by exciting; if the thickness of the metal film is too thick, the excited and generated surface plasmon polaritons cannot penetrate the metal film and therefore cannot be hybridized by the gap structure between the scanning probe 401 and the metal film, cannot form a surface plasmon polariton field hybridization unit, and thus cannot realize surface plasmon polariton near-field enhancement. The inventors of the present application, through multiple experimental optimizations, have obtained a metal film having a thickness above 25nm, preferably 40-50nm, and more preferably 45nm; the metal film having such a thickness can guarantee the efficiency and effect of the exciting and generating of surface plasmon polaritons. As for the material of the metal film, it may be the existing ordinary gold, silver or aluminum, which is not specifically limited and described herein.
With respect to the gap structure between the scanning probe 401 and the metal film, the applicant, through theoretical research and multiple experimental optimizations, finds out that the gap structure is preferably greater than 1nm and smaller than 10nm, so that the surface plasmon polariton virtual probe formed by focusing the surface plasmon polaritons is hybridized with the scanning probe in the gap structure to form a new surface plasmon polariton optical field with localized high filed strength; and the applicant found through research that, when the gap structure is smaller than 1nm, a tunnelling effect may occur, which reduces the hybridized field strength; when the gap structure is greater than 10nm, e.g., being 15nm, the applicant finds out through research that the hybridized field strength of such a gap structure is also reduced sharply, which lowers the detection sensitivity of the scanning probe 401.
In order to ensure the detection sensitivity of the scanning probe 401, during use, the movement of the scanning probe 401 is controlled by the monitor unit 60, so as to align the scanning probe 401 with the surface plasmon polariton virtual probe generated by exciting on the surface of the metal film, and since the surface plasmon polariton virtual probe has increased intensity at a central area thereof, a greater extent of alignment of the scanning probe 401 sweeping over this location with the surface plasmon polariton virtual probe would lead to more enhanced scattered light, so that the detection sensitivity of the scanning probe 401 is higher, and the acquired Raman spectral signal is stronger. The surface plasmon polaritons undergo hybridization reactions with the gap structure in its propagation process of penetrating the metal film, coupled oscillation occurs, and the combined action of the surface plasmon polariton virtual probe generated by the exciting light on the surface of the metal film and the scanning probe 401 enhances the Raman spectral signal associated with the surface localized field strength.
With respect to the exciting light unit 10, the exciting light unit 10 comprises a laser element 101, a polarizing element 102, a collimating element 103 and a vortex wafer 104; the laser element 101 is configured to generate a laser beam with a preset wavelength, e.g., in a wavelength range of visible light, the laser beam enters the polarizing element 102; the polarizing element 102 converts the incident laser beam into linearly polarized light which enters the collimating element 103; the collimating element 103 expands and collimates the incident linearly polarized light to obtain parallel light which enters the vortex wafer 104; the vortex wafer 104 converts the parallel light into radially polarized light which enters the surface plasmon polariton exciting unit 20, i.e., enters the object lens thereof, and irradiates the metal film to excite and generate surface plasmon polaritons, wherein the laser is focused to generate a surface plasmon polariton virtual probe. Specifically, as shown in FIG. 3, the laser element 101 is, but not limited to, an existing ordinary Helium-Neon laser emitter, the polarizing element 102 is, but not limited to, an existing polarizer, the collimating element 103 is, but not limited to, a positive lens group. The positive lens group may include a first convex lens 1031 and a second convex lens 1032 that are coaxial and spaced apart, wherein the first convex lens 1031 has a focal distance smaller than that of the second convex lens 1032, the laser beam is collimated as it passes the first convex lens 1031 and the second convex lens 1032 and is outputted as parallel light; the positive lens group may also be composed of a positive lens and a negative lens, as long as it can collimate the light beam emitted from the laser element 101 and output parallel light. In physical locations, the laser element 101, the collimating element 103 and the vortex wafer 104 are located in the same horizontal straight line optical path and are all under the bottom of the surface plasmon polariton exciting unit 20, i.e., the laser beam enters the surface plasmon polariton exciting unit 20 from the bottom thereof. More specifically, along the optical path direction, a reflector is arranged behind the vortex wafer 104, i.e., on the left of the vortex wafer 104 as shown in the Figure, this reflector forms an intersection angle of 135 with the horizontal direction, and another reflector oriented in the vertical direction is arranged above this reflector. Of course, the number of reflectors may also be another number, such as one, three, etc. The radially polarized light is reflected by the two reflectors in sequence and then enters the surface plasmon polariton exciting unit 20. In the present application, as the radially polarized light is a circular vortex light beam, the energy of the incident light can be efficiently utilized to excite the surface plasmon polariton optical field and be focused to obtain the surface plasmon polariton virtual probe.
With respect to the surface plasmon polariton exciting unit 20, it comprises an object lens 202, a metal film (not shown) and a beam splitting element 201. The beam splitting element 201 is a semi-reflective semi-transmissive structure, which is, but not limited to, an existing ordinary beam splitting mirror or dichroic mirror. The beam splitting element 201 is arranged under the bottom of the object lens 202 and in the optical path of the laser beam, the beam splitting element 201 forms an intersection angle of 135° with the horizontal direction, and the radially polarized light, after entering the beam splitting element 201, is split into two parts, namely, a first beam and a second beam, wherein, the first beam is reflected and vertically enters the object lens 202, the second beam is transmitted out through the beam splitting element 201. With respect to the object lens 202, there is a metal film coated on a glass substrate of the object lens 202, a sample to be measured is put on the glass substrate, and surface plasmon polaritons are generated at the interface between the sample to be measured and the metal film, and penetrate the metal film to enter the gap structure to be hybridized with another metal film on the scanning probe, so as to form the surface plasmon polariton field hybridization unit 30, wherein the surface plasmon polariton field hybridization unit in the present application is an enhanced mode of surface plasmon polaritons.
The laser beam enters the metal film on the object lens 202, the scanning probe 401 detects the Raman scattered light of the sample to be measured and, after being coupled by the object lens 202, obtains coupled light, the coupled light is reflected to the beam splitting element 201 and, after being transmitted through the optical filter element 501, enters the measurement unit 50, and the monitor unit 60 displays an image of the Raman spectrum of the sample to be measured. Specifically, an optical filter element 501, a lens, a spectrograph 502 and a CCD image sensor 503 are arranged in sequence in the reflection optical path of the beam splitting element 201, and in physical locations, the beam splitting element 201, the optical filter element 501, the lens, the spectrograph 502 and the CCD image sensor 503 are located in the same horizontal straight line optical path which is parallel to the horizontal straight line optical path of the respective components of the exciting light unit 10; the optical filter element 501 comprises a first optical filter 5011, i.e., the optical filter on the left as shown in FIG. 3, and a second optical filter 5012, i.e., the optical filter on the right as shown in FIG. 3, the two optical filters symmetrically disposed on the left and right constitute the optical filter element, wherein the first optical filter 5011 on the left forms an intersection angle, e.g., 135, with the horizontal line, and the second optical filter 5012 on the right forms an intersection angle, e.g., 45, with the horizontal line. The laser beam is reflected by the reflector to the first optical filter 5011 and then is reflected to the beam splitting element 201, therefore, the optical path for the laser beam to enter the metal film is partially overlapping the optical path of reflection from the sample to be measured, and the overlapping part is the part of optical path between the beam splitting element 201 and the optical filter element 501, so that the optical paths are reduced, with a more compact structure. The structure and working principles of the optical filter element and the lens are not limited and described herein; the spectrograph 502 is also an existing ordinary Raman spectrograph, whose specific structure and working principle is not limited and described herein. The purpose of arranging the optical filter element is for filtering out the exciting light wavelength and only allowing the Raman spectrum wavelength of the sample to be measured to pass and enter the spectrograph and the CCD image sensor. The optical filter element 501 can filter out the light of the sample to be measured that is reflected by the metal film, and allow the detection light thereof to be transmitted therethrough and enter the spectrograph 502 and the CCD image sensor 503.
The present application also comprises a scanning platform (not shown), the scanning probe 401 is movably disposed on the scanning platform, and the scanning platform is connected to the monitor unit 60, so as to realize synchronization of the monitor unit 60, the CCD image sensor 503 and the scanning platform; the scanning platform has a sample to be measured placed thereon, the monitor unit 60 can control the scanning probe 401 to move and performing scanning detection on the sample to be measured, so as to acquire a Raman spectrogram of the sample to be measured and display an image on the monitor unit 60; the scanning probe 401 is sequentially connected to the spectrograph 502 and the monitor unit 60, wherein, the scanning probe 401 detects and sends the sample surface morphology and spectral information of the sample to be measured to the spectrograph, the spectrograph is configured to measure the Raman spectrum of the sample to be measured and scan the Raman spectrum of the sample to be measured for imaging, and the scanned image of the Raman spectrum of the sample to be measured is sent to the monitor unit 60 for displaying the image. Optionally, in the present application, the scanning platform is, but not limited to, an atomic force microscope, the scanning probe 401 is, but not limited to, an atomic force microscope probe, and as the atomic force microscope has relatively high precision, the present application preferably uses an atomic force microscope and an atomic force microscope probe; the scanning probe in the present application is a metal probe or a probe coated with a metal film. The scanning probe 401 may be disposed on the scanning platform by means of an existing ordinary microcantilever (not shown) of an atomic force microscope, whose specific structure and working principle is not limited and described herein.
The monitor unit 60 in the present application comprises a control system (not shown) and a display system (not shown), and is preferably a computer.
The illumination unit 70 comprises an illumination light source, a beam splitting mirror, a lens and a camera, wherein, the illumination light source and the beam splitting mirror are located in the same vertical optical path with the beam splitting element 201, the beam splitting mirror is under the bottom of the beam splitting element and forms an intersection angle of 450 with the horizontal line, the camera is arranged on the left of the beam splitting mirror, the lens is arranged between the beam splitting mirror and the camera, the lens, the camera and the beam splitting mirror are located in the same horizontal straight line optical path; the light reflected from the sample passes and is partially transmitted through the beam splitting element 201, and is then reflected by the beam splitting mirror to the camera. The illumination light source is preferably a white light source.
The Raman spectral signal enhancement of the tip-enhanced Raman spectral microscopic imaging device of the present application can be affirmed by the Raman spectrograms of the sample measured by the spectrograph, as shown in FIG. 4, wherein a represents the Raman spectral signal strength of the measured sample acquired by using a microscopic imaging device of the present application, b represents the Raman spectral signal strength of the measured sample acquired by only using a virtual probe formed by focusing on a metal film; as shown in FIG. 5, wherein c represents the Raman spectral signal strength of the measured sample acquired by using a conventional Raman spectral microscopic imaging device having no virtual probe, d represents the Raman spectral signal strength of the measured sample acquired by using a device without a surface plasmon polariton virtual probe generated on a metal film or a gap structure formed between a scanning probe and a metal film. As clearly seen from FIG. 4 and FIG. 5, the Raman spectral signal of the tip-enhanced Raman spectral microscopic imaging device of the present application has higher signal strength.
The resolution of the tip-enhanced Raman spectral microscopic imaging device of the present application is also improved, as shown in FIG. 6 to FIG. 9, herein, a carbon nanotube is used as a standard sample to calibrate the resolution, FIG. 6 shows a microscopic image of the spatial distribution of the carbon nanotube scanned by a tip-enhanced Raman spectral microscopic imaging device of the present application; FIG. 7 shows a profile distribution along the dotted line in FIG. 6, wherein the horizontal coordinate represents a spatial location of the carbon nanotube, herein, the spatial location is a representation of the spatial dimensions of the carbon nanotube, the vertical coordinate represents a height of the carbon nanotube, and the obtained scanning resolution is 43nm; FIG. 8 shows that the spatial resolution obtained by scanning the measured sample by using a tip-enhanced Raman spectral microscopic imaging device of the present application can reach 13.5nm; FIG. 9 corresponds to Raman spectrograms of the standard sample of carbon nanotube.
Apparently, the aforementioned embodiments are merely examples illustrated for clearly describing the present application, rather than limiting the implementation ways thereof. For a person with ordinary skill in the art, various changes and modifications in other different forms can be made on the basis of the aforementioned description. It is unnecessary and impossible to exhaustively list all the implementation ways herein. However, any obvious changes or modifications derived from the aforementioned description are intended to be embraced within the protection scope of the present application.
Claims (10)
- Claims 1. A tip-enhanced Raman spectral microscopic imaging device, comprising:an exciting light unit (10), configured to generate a radially polarized light beam to enter a surface plasmon polariton exciting unit (20) which is configured to receive the radially polarized light beam and excite surface plasmon polaritons;a scanning unit (40), comprising a scanning probe (401) able to be hybridized with the surface plasmon polaritons to form a surface plasmon polariton field hybridization unit (30);a measurement unit (50), configured to measure a Raman spectrum of a sample to be measured and perform scanning and imaging;a monitor unit (60), configured to display the Raman spectrum of the sample to be measured and perform imaging according to a characteristic spectrum of the sample to be measured;wherein the exciting light unit (10) and the measurement unit (50) are both connected to the monitor unit (60), and the scanning unit (40) is sequentially connected to the measurement unit (50) and the monitor unit (60).
- 2. The tip-enhanced Raman spectral microscopic imaging device according to Claim 1, characterized in that, the surface plasmon polariton exciting unit (20) comprises:an object lens (202); anda metal film coated on the object lens (202);wherein, the radially polarized light beam that enters the metal film excites and generates the surface plasmon polaritons that are focused to generate a surface plasmon polariton virtual probe, and the surface plasmon polariton virtual probe is hybridized with the scanning probe (401) to form the surface plasmon polariton field hybridization unit.
- 3. The tip-enhanced Raman spectral microscopic imaging device according to Claim 2, characterized in that, the metal film has a thickness of 40-50nm, and the object lens (202) has a numerical aperture greater than 1.45.
- 4. The tip-enhanced Raman spectral microscopic imaging device according to Claim 3, characterized in that, a gap is formed between the scanning probe (401) and the metal film, and the gap is smaller than1Onm.
- 5. The tip-enhanced Raman spectral microscopic imaging device according to Claim 4, characterized in that, the exciting light unit (10) comprises:a laser element (101), configured to generate a laser beam with a preset wavelength; and a polarizing element (102), a collimating element (103) and a vortex wafer (104) arranged in sequence between the laser element (101) and the object lens (202) in an optical path output direction of the laser beam; wherein, the laser beam, after passing the polarizing element (102), the collimating element (103) and the vortex wafer (104), is converted into the radially polarized light beam and enters the object lens (202).
- 6. The tip-enhanced Raman spectral microscopic imaging device according to Claim 5, characterized in that, the collimating element (103) is a lens group, and the radially polarized light beam is outputted as parallel light after passing the lens group.
- 7. The tip-enhanced Raman spectral microscopic imaging device according to Claim 5, characterized in that, the surface plasmon polariton exciting unit (20) further comprises:a beam splitting element (201), arranged between a beam incident end of the object lens (202) and a beam emitting end of the vortex wafer (104), and configured to transmit the radially polarized light beam to the object lens (202) to excite and generate the surface plasmon polaritons on the metal film.
- 8. The tip-enhanced Raman spectral microscopic imaging device according to Claim 7, characterized in that, the beam splitting element (201) is a beam splitting mirror or a dichroic mirror.
- 9. The tip-enhanced Raman spectral microscopic imaging device according to Claim 7, characterized in that, the measurement unit (50) comprises:an optical filter element (501);a spectrograph (502); anda CCD image sensor (503);wherein the optical filter element (501), the spectrograph (502) and the CCD image sensor (503) are connected to the beam splitting element (201) through a horizontal straight line optical path;Raman scattered light of the sample to be measured, after being coupled by the object lens (202), is converted into coupled light and reflected to the beam splitting element (201), enters the spectrograph (502) and the CCD image sensor (503) after being transmitted through the optical filter element (501); and the monitor unit (60) displays the Raman spectrum of the sample to be measured and performs imaging according to the characteristic spectrum thereof.
- 10. The tip-enhanced Raman spectral microscopic imaging device according to any one of Claims 1-9, characterized in that, the scanning probe (401) is a probe coated with a metal film.
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| CN201911378038.1A CN110967333A (en) | 2019-12-27 | 2019-12-27 | Needle tip enhanced Raman spectrum microscopic imaging device |
| PCT/CN2020/130516 WO2021129267A1 (en) | 2019-12-27 | 2020-11-20 | Tip-enhanced raman spectroscope microscopic imaging device |
| AUPCT/CN2020/130516 | 2020-11-20 |
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| CN110967333A (en) * | 2019-12-27 | 2020-04-07 | 深圳大学 | Needle tip enhanced Raman spectrum microscopic imaging device |
| CN111474164B (en) * | 2020-06-01 | 2024-07-30 | 广州贝拓科学技术有限公司 | Microscopic laser Raman spectrometer and working method thereof |
| CN111721750A (en) * | 2020-06-23 | 2020-09-29 | 深圳大学 | Method and device for improving non-contact mode TERS signal of atomic force microscope |
| CN112014308A (en) * | 2020-09-07 | 2020-12-01 | 中国石油大学(华东) | Raman-enhanced electrochemical corrosion cell and control method thereof |
| CN113030063A (en) * | 2021-03-31 | 2021-06-25 | 厦门大学 | Small-sized needle tip enhanced Raman spectrum measuring device and detection method thereof |
| CN113625205B (en) * | 2021-08-09 | 2022-03-25 | 中国人民解放军军事科学院国防科技创新研究院 | Multichannel atomic magnetic field measuring device |
| CN114460674B (en) * | 2022-01-25 | 2023-11-14 | 南京邮电大学 | Addressable surface plasmon closed-loop control modulation system and method |
| CN118090605B (en) * | 2024-04-17 | 2024-07-05 | 北京大学长三角光电科学研究院 | Detection method and detection system for lithium niobate polarization structure |
| CN118671956B (en) * | 2024-08-20 | 2024-10-29 | 浙江大学 | Single-molecule plasmon optical tweezers system integrating quantum tunneling sensing |
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| CN102707342B (en) * | 2012-06-20 | 2013-12-25 | 北京大学 | Surface plasmon lens integrated with metal nano-cavity |
| CN102798735B (en) * | 2012-08-14 | 2015-03-04 | 厦门大学 | Pinpoint enhanced dark-field microscope, electrochemical testing device and leveling system |
| US10012674B2 (en) * | 2015-09-04 | 2018-07-03 | The Regents Of The University Of California | Nanoantenna scanning probe tip, and fabrication methods |
| US10145799B2 (en) * | 2017-02-22 | 2018-12-04 | Baylor University | Fiber-coupled metal-tip near-field chemical imaging spectroscopy |
| CN108152267B (en) * | 2018-01-31 | 2020-05-01 | 西北工业大学 | Method for efficiently exciting surface-enhanced Raman scattering of metalized optical fiber |
| CN209327689U (en) * | 2018-12-11 | 2019-08-30 | 深圳大学 | A kind of surface phasmon light forceps device |
| CN109929748A (en) * | 2019-03-08 | 2019-06-25 | 东南大学 | The instrument platform of DNA sequencing is realized based on pinpoint enhanced Raman scattering spectrum technology |
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| CN110967333A (en) * | 2019-12-27 | 2020-04-07 | 深圳大学 | Needle tip enhanced Raman spectrum microscopic imaging device |
| CN211602937U (en) * | 2019-12-27 | 2020-09-29 | 深圳大学 | Needle tip enhanced Raman spectrum microscopic imaging device |
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