CN108732156B - Detection method for selecting rule forbidden phonon mode - Google Patents
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Abstract
The invention provides a detection method for selecting a rule forbidden phonon mode, which relates to the technical field of nano optics, wherein the detection method comprises the following steps: preparing a material to be characterized and a metal particle pattern which is tightly stacked in a single layer, so that metal particles are mutually and tightly arranged and form a gap with a preset size; and collecting the electric field gradient Raman spectrum of the material to be characterized in the gap of the metal particles so as to detect the phonon mode forbidden by the conventional Raman selection rule in the material to be characterized according to the electric field gradient Raman spectrum. The method has the advantages of low cost, simple operation, strong flexibility and the like, and solves the problem that the research on the electric field gradient Raman scattering on the sub-nanometer scale is difficult due to the limitation of the selection rule of the conventional Raman scattering in the prior art.
Description
Technical Field
The invention relates to the technical field of nano optics, in particular to a detection method for selecting a rule forbidden phonon mode.
Background
Raman spectrum is a fast and nondestructive characterization method of material scattering spectrum, Raman scattering is a photon inelastic scattering process, Raman frequency shift and intensity, polarization and the like mark phonon (or molecular vibration) properties of scattering substances, so that information of substance structures and substance composition components is derived, the information can be used as 'fingerprints' of materials, and fine changes of material properties can be accurately reflected, so that the method is widely applied to various fields of physics, chemistry, material science, biology and the like. In a material, not all phonon modes are detectable by raman spectroscopy.
When light interacts with matter, the linear term of polarizability causes raman scattering as a function of lattice vibrations, and the nonlinear term of polarizability is generally ignored because it contributes little to inelastic scattering under typical experimental conditions. In the prior art, changes in raman selection rules due to electric field gradients have been discovered, but since it has been difficult to manipulate light and materials at sub-nanometer scales, research and application of electric field gradient raman scattering has been greatly limited.
Disclosure of Invention
An object of the present invention is to provide a detection method for a phonon mode prohibited by a selection rule to solve the problem in the prior art that the study of electric field gradient raman scattering on a sub-nanometer scale is difficult due to the limitation of the selection rule of conventional raman scattering.
In particular, the present invention provides a detection method for selecting a rule-forbidden phonon mode, comprising:
preparing a material to be characterized and a single-layer closely-packed metal particle pattern, so that the metal particles are closely arranged with each other and form a gap with a preset size;
and collecting the electric field gradient Raman spectrum of the material to be characterized in the gap of the metal particles so as to detect the phonon mode forbidden by the conventional Raman selection rule in the material to be characterized according to the electric field gradient Raman spectrum.
Further, preparing a material to be characterized and a monolayer of closely packed metal particle pattern, so that the metal particles are closely arranged with each other and form gaps with a preset size range, comprising:
preparing the material to be characterized on a substrate;
preparing the single-layer closely-packed metal particle pattern on the material to be characterized, and enabling the metal particles to be closely arranged with each other and form gaps with preset sizes.
Further, preparing a material to be characterized and a monolayer of closely packed metal particle pattern, so that the metal particles are closely arranged with each other and form gaps with a preset size range, comprising:
preparing the single-layer closely-packed metal particle pattern on a substrate, and enabling the metal particles to be mutually closely arranged to form a gap with a preset size;
preparing the material to be characterized on the monolayer of closely packed metal particle patterns.
Further, the material to be characterized is a non-metal material which can be characterized by using a Raman spectrum, and can be coupled with the metal particles or plasma units of a gap structure formed between the metal particles so as to realize Raman enhancement. Wherein the gap between adjacent metal particles is within the range of the preset dimension.
Further, the material to be characterized is a non-metal material which can be characterized by using a raman spectrum, and can be coupled with plasma elements of metal nanostructures, and gaps of the metal nanostructures are in the range of the preset scale. Wherein the metal nanostructure is a nanostructure composed of the metal particles and having surface plasmon resonance.
Further, the preset dimension is less than 10 nm;
further, the predetermined dimension is less than 5 nm.
Further, the material to be characterized comprises organic molecules, carbon nanotubes, graphene and/or a monolayer of molybdenum sulfide.
Further, the size and shape of the metal particles are selected such that the plasmon resonance peak thereof matches the wavelength of the excitation laser.
Further, the metal particles are metal particles having surface plasmon resonance, including but not limited to noble metal nanoparticles.
Further, the structure composed of the metal particles is a nanostructure having surface plasmon resonance.
Further, the metal particles are noble metal-containing nanoparticles, and the nanostructures formed by the noble metal-containing nanoparticles are nanostructures with surface plasmon resonance.
The metal particle material comprises a metal simple substance and/or an alloy and/or a heterostructure;
preferably, the metal nanoparticle material comprises a noble metal-containing simple substance and/or alloy and/or heterostructure;
the size of the metal particles is selected to be nano-scale, micro-nano-scale or micro-scale; and
the shape of the metal particles is selected from one or more of nanospheres, nano discs, nano cubes, nano polyhedrons and nano rods.
Further, the preparation method of the material to be characterized comprises spin coating, spraying and soaking a solution or dispersion liquid containing the characterization material components, and also comprises one or more of electrochemistry, chemical vapor deposition, thermal evaporation, electron beam evaporation and micromachining.
Further, the material to be characterized is a one-dimensional nanowire or nanorod or nanotube;
further, the material to be characterized is two-dimensional graphene or molybdenum disulfide or nanoparticles.
The invention has the beneficial effects that:
firstly, preparing a material to be characterized and a monolayer metal particle pattern which is tightly packed, enabling the metal particles to be mutually and tightly arranged and forming a gap with a preset scale, and then collecting an electric field gradient Raman spectrum of the material to be characterized in the gap of the metal particles so as to detect a phonon mode forbidden by a conventional Raman selection rule in the material to be characterized according to the electric field gradient Raman spectrum. Therefore, the detection method can utilize the sub-nanometer-scale gaps among the self-assembled metal particles to be compounded with the material to be characterized to construct a strong electric field gradient, so that the electric field gradient Raman scattering can be enhanced to detect the phonon mode forbidden by the conventional Raman selection rule in the material to be characterized. That is to say, in the material to be characterized without defects, the D mode cannot be detected by the conventional raman spectroscopy, and after the material is compounded with metal particle patterns which are closely arranged with each other and form a gap with a preset scale range, a strong D mode can be detected in addition to raman enhancement caused by surface plasmon elements, which indicates that the electric field gradient raman scattering breaks the selection rule of the conventional raman scattering, and realizes the detection of the central phonon mode of the non-brillouin zone. Therefore, the detection method solves the problem that the research on the electric field gradient Raman scattering on the sub-nanometer scale is difficult due to the limitation of the selection rule of the conventional Raman scattering in the prior art.
And secondly, the size and the shape of the metal nano particles are constructed to enable the plasmon resonance peak of the metal nano particles to be matched with the wavelength of the excitation laser, so that the size and the shape of the gap between adjacent noble metal nano particles can be configured by different assembling modes and conditions, and great convenience can be brought to the research of electric field gradient Raman scattering.
Moreover, the step of preparing the material to be characterized and the step of preparing the monolayer close-packed metal particle pattern can be exchanged, so that the detection method is simple, convenient and quick and has stronger flexibility.
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FIG. 1 is a schematic flow diagram of a detection method for selecting a regularly prohibited phonon mode according to one embodiment of the present invention;
FIG. 2 is a schematic flow diagram of a detection method for selecting a regularly prohibited phonon mode according to another embodiment of the present invention;
FIG. 3 is a schematic flow chart of a detection method for selecting a regularly prohibited phonon mode according to a third embodiment of the present invention;
FIG. 4 is a schematic operational diagram of the detection method of FIG. 2 for selecting a regularly disabled phonon mode;
FIG. 5 is a schematic operational diagram of the detection method of FIG. 3 for selecting a regularly disabled phonon mode;
FIG. 6 is a SEM schematic structural view of the preparation of carbon nanotubes and a schematic structural view of the preparation of a gold nanoparticle close-packed pattern on carbon nanotubes in the first embodiment;
FIG. 7 is a schematic dark field spectrum of the gold nanoparticle close-packed pattern of FIG. 5;
FIG. 8 is a schematic in situ Raman spectra of single-walled carbon nanotubes before and after a composite gold nanoparticle close-packed pattern, according to one embodiment of the present invention;
fig. 9 is a schematic diagram of D-mode raman scattering and electric field gradient raman scattering in a carbon nanotube, according to an embodiment of the present invention.
Detailed Description
In a material not all phonon modes are detectable by raman spectroscopy. First, the raman scattering process has a close relationship with the symmetry of the target material, and only phonon (or phonon vibration) modes satisfying a specific symmetry can undergo inelastic scattering with electrons in an excited state to generate a raman peak. Secondly, in the Raman scattering process, because the dispersion curve of photons is extremely steep, in a visible-near infrared band, the optical transition of electrons is vertical transition, and only phonons in the center of the Brillouin area can be detected for first-order Raman scattering (only one electron-phonon scattering occurs).
In the prior art, changes in raman selection rules due to electric field gradients have been discovered, but since it has been difficult to manipulate light and materials at sub-nanometer scales, research and application of electric field gradient raman scattering has been greatly limited. In some experiments, the angle-resolved microsphere lithography is used to process the sub-nanometer scale metal nanogap, and the existence of the electric field gradient Raman scattering enhancement effect is verified, but the micro-nanometer processing technology is needed, so the process is complicated, the cost is high, and the efficiency is low.
In order to solve the above technical problems, the present embodiment provides a detection method for prohibiting phonon mode according to the selection rule, so as to solve the problem in the prior art that it is difficult to study electric field gradient raman scattering on a sub-nanometer scale due to the limitation of the conventional raman scattering selection rule. As shown in fig. 1, the detection method of the present embodiment may include:
s100, preparing a material to be characterized and a metal particle pattern tightly stacked in a single layer, so that metal particles are mutually and tightly arranged to form a gap with a preset size;
s200, collecting electric field gradient Raman spectrum of the material to be characterized in the metal particle gap, and detecting a phonon mode forbidden by a conventional Raman selection rule in the material to be characterized according to the electric field gradient Raman spectrum.
In step S100, as shown in fig. 2 and 4, the operation of preparing the material to be characterized and the single-layer closely-packed metal particle pattern, so that the metal particles are closely arranged to each other and form the gap with the preset size range may include:
s10, preparing a material to be characterized on a substrate;
s20, preparing a single-layer closely-packed metal particle pattern on the material to be characterized, and enabling the metal particles to be closely arranged with each other to form a gap with a preset size.
Alternatively, in another embodiment, as shown in fig. 3 or fig. 5, the operation of preparing the material to be characterized and the monolayer of closely-packed metal particle pattern in step S100, so that the metal particles are closely arranged with each other and form gaps with a preset size range, may include:
s1, preparing a single-layer closely-packed metal particle pattern on a substrate, and enabling metal particles to be mutually and closely arranged to form a gap with a preset size;
s2, preparing a material to be characterized on the single-layer close-packed metal particle pattern.
In the detection method of the embodiment, a material to be characterized may be first prepared on a substrate, then a single-layer closely-packed metal particle pattern is prepared on the material to be characterized, so that metal particles are closely arranged with each other and form a gap having a preset scale range (or single-layer closely-packed metal particles may be first prepared on the substrate, then the material to be characterized is prepared on the metal particles), and then an electric field gradient raman spectrum of the material to be characterized in the metal particle gap is collected. Thus, the detection method of the embodiment can utilize the sub-nanometer-scale gap between the self-assembled metal particles to be compounded with the material to be characterized to construct a strong electric field gradient (i.e. the strong local electric field gradient can be realized by utilizing simple modes such as liquid level self-assembly, evaporation-induced self-assembly and the like without using a micro-nano processing technology), so that electric field gradient raman scattering can be enhanced to detect a phonon mode forbidden by a conventional raman selection rule in the material to be characterized. That is to say, in the material to be characterized without defects, the D mode cannot be detected by the conventional raman spectroscopy, and after the material is compounded with metal particle patterns which are closely arranged with each other and form a gap with a preset scale range, a strong D mode can be detected in addition to raman enhancement caused by surface plasmon elements, which indicates that the electric field gradient raman scattering breaks the selection rule of the conventional raman scattering, and realizes the detection of the central phonon mode of the non-brillouin zone. Therefore, the detection method of the embodiment solves the problem that the research on the electric field gradient Raman scattering on the sub-nanometer scale is difficult due to the limitation of the selection rule of the conventional Raman scattering in the prior art.
It should be noted that when the optical field is limited to the atomic scale (e.g. 0.1-5 nm), the strong electric field gradient can make the material polarizability nonlinear effect become significant, and the electric field gradient raman scattering, which can be ignored in the conventional raman scattering, becomes strong, so that the conventional raman scattering selection rule can be disabled, and many molecular vibration modes prohibited by the conventional raman selection rule can be activated. Therefore, the phonon mode forbidden by the selection rule can be detected by using electric field gradient Raman scattering, and the application space of the spectral characterization of phonons can be expanded by complementing the conventional Raman scattering and phonon infrared absorption.
As shown in fig. 2, the material to be characterized may be deposited on the substrate in advance, which plays an important role in accurately positioning the material to be characterized and in situ, comparing the change of the raman spectrum of the material before and after enhancement, and accurately determining the contribution of the electric field gradient raman scattering.
In addition, the sequence of preparing the material to be characterized and preparing the monolayer close-packed metal particle pattern can be exchanged, so that the detection method of the embodiment has the advantages of low cost, simple and convenient operation, strong flexibility and the like, and can be widely applied to a plurality of fields of material structure analysis, phase analysis, biological characterization and the like.
In the first to third embodiments, the material to be characterized may be a non-metal material characterized by raman spectroscopy, and may be coupled with a metal particle plasmon structure to achieve raman enhancement, or may be coupled with a plasmon in a metal particle gap structure, with the gap between adjacent metal particles being within a range of preset dimensions. The predetermined dimension may be less than 20 nm. Further, the preset dimension may be less than 10 nm. Preferably, the predetermined dimension may also be less than 5 nm. The predetermined dimension may be in the range of 0.1-10nm, or 0.2-0.8nm, or less than about 5nm, i.e., the gap between adjacent metal particles may be less than about 5 nm. That is, the material to be characterized should be limited to sub-nanometer dimensions (typically less than 5nm is required) and may include, but not be limited to, organic molecules, carbon nanotubes, graphene, single-layer molybdenum sulfide, and the like.
The material to be characterized can be a one-dimensional nanowire or nanorod or nanotube, and the material to be characterized can also be two-dimensional graphene or molybdenum disulfide or nanoparticles. Namely, the dimension of the material to be characterized is not limited, and the material can be a one-dimensional nanowire, a nanorod or a nanotube, or can be two-dimensional graphene or molybdenum disulfide, or can be nanoparticles.
The preparation method of the material to be characterized can be from bottom to top or from top to bottom, and the preparation method can include but is not limited to: spin coating, spraying, dipping a solution or dispersion containing the characterizing material component, and may further include one or more of electrochemical, chemical vapor deposition, thermal evaporation, e-beam evaporation, micro-machining.
The size and shape of the metal particles are chosen such that the plasmon resonance peak matches the wavelength of the excitation laser, i.e. the size and shape of the metal particles, and the nanostructure formed, are chosen such that the surface plasmon resonance peak matches the excitation wavelength of the raman spectrum (typically requiring a laser wavelength within the full width at half maximum of the plasmon resonance peak). Because the size and the shape of the metal nano particles are constructed to enable the plasmon resonance peak of the metal nano particles to be matched with the wavelength of the excitation laser, the size and the shape of the gap between adjacent noble metal nano particles can be configured by different assembly modes and conditions, so that the electric field gradient Raman scattering excited by different wavelengths can be realized. In addition, the size and the shape of the nanogap can be realized through different assembly modes and conditions, so that great convenience is brought to the research of electric field gradient Raman scattering.
The metal particles may be metal particles having a surface enhanced raman scattering effect, for example, the metal particles may be noble metal nanoparticles, that is, the metal nanoparticles may be nanostructures having surface plasmon resonance, and the composition thereof is not limited. The material of the metal particles may include noble metal elements and/or alloys and/or heterostructures, including, but not limited to, gold, silver, and the like, and alloys thereof. The size of the metal particles is not limited, and the metal particles can be selected to be nano-scale, micro-nano-scale or micron-scale, and can also be nano-particles and nano-structures. The shape of the metal particles is also not limited, and may be selected from one or more of nanospheres, nanoplates, nanocubes, nanopolyhedrons, nanorods, and the like. It can also be said that the shape, size and material of the metal particles are not limited, and may be particles of different shapes, sizes and materials, as long as the particles and structures of different shapes, sizes and materials form gaps of sub-nanometer scale. Wherein, the size of the gap between the adjacent metal particles can be less than 5nm, and the gap can be ordered or disordered. And the structure composed of metal particles is a metal nano-structure with a nano-structure of surface plasmon resonance. The metal nanostructure may be formed of other structures.
In any of the above embodiments, a monolayer of closely packed metal particle patterns is prepared on a substrate or on a material to be characterized, wherein close packing refers to closely arranging metal nanoparticles to each other to form sub-nanometer scale gaps (typically less than 5nm is required), and methods of preparing the monolayer of closely packed metal particle patterns include, but are not limited to: liquid level self-assembly, evaporation induced self-assembly, and the like.
In addition, the step of preparing the material to be characterized and the step of preparing the monolayer close-packed metal particle pattern can be exchanged, so that the detection method of any embodiment is simple, convenient and quick, and has strong flexibility.
In a first embodiment, which may be described in conjunction with fig. 2 and 4, a detection method for selecting a rule-inhibiting phonon mode may include:
step (1): preparing a horizontal array of the ultra-long single-walled carbon nanotubes on the Si/SiOx substrate containing the positioning marks by using a chemical vapor deposition method, and collecting the Raman spectrum of the single ultra-long single-walled carbon nanotube according to the positioning marks.
Step (2): preparing a polyhedral gold nanoparticle dilute solution with the diameter of 30nm, dripping 20 mu L of the dilute solution on the position of the marking substrate with the ultra-long single-walled carbon nanotube, and baking for 15min under an incandescent lamp to form a hexagonal close-packed gold nanoparticle pattern.
And (3): finding out the position of the pattern of the gold nanoparticles densely stacked between the ultra-long single-walled carbon nanotube and the hexagonal shape under an electron microscope, and collecting a Raman spectrum of the single-walled carbon nanotube by using 785nm laser under a microscopic confocal Raman spectrometer.
SEM photographs before and after the ultra-long single-walled carbon nanotube and the hexagonal close-packed gold nanoparticle pattern are combined are shown in fig. 6, in which a is an SEM photograph of a single aligned ultra-long single-walled carbon nanotube grown on a substrate, and b is an SEM photograph of the same position after the 30nm gold nanoparticle close-packed pattern is assembled. The dark field spectrum of the hexagonal close-packed gold nanoparticle pattern is shown in fig. 7, which shows that the plasmon resonance peak of the pattern can be well matched with 785nm laser. The single-walled carbon nanotube has a diameter of about 1.3nm, has high alignment properties, and is free from bending within 500 μm in the tube axis direction. Fig. 8 can be an in-situ raman spectrum of single-walled carbon nanotubes before and after a close-packed pattern of complex alloy nanoparticles, and a D mode in fig. 8 belongs to a phonon mode of a brillouin zone boundary. As can be explained by referring to fig. 6 to 9, in the carbon nanotube without defects, the D mode cannot be detected by the conventional raman spectroscopy, and after the carbon nanotube is compounded with the gold nanoparticle close-packed pattern, the strong D mode can be detected in addition to the raman enhancement caused by the surface plasmon, so that the electric field gradient raman scattering breaks the selection rule of the conventional raman scattering, and the detection of the central phonon mode of the non-brillouin zone is realized.
In a second embodiment, which may be described in conjunction with fig. 2 and 4, a detection method for selecting a rule-inhibiting phonon mode may include:
step (1): preparing a horizontal array of the ultra-long single-walled carbon nanotubes on the Si/SiOx substrate containing the positioning marks by using a chemical vapor deposition method, and collecting the Raman spectrum of the single ultra-long single-walled carbon nanotube according to the positioning marks.
Step (2): preparing a gold nanorod dilute solution with the diameter of about 25nm, dripping 50 mu L of the dilute solution on the position of the marked substrate with the ultra-long single-walled carbon nanotube, and baking for 20min under an incandescent lamp to form a self-organized closely-arranged gold nanorod pattern.
And (3): finding the position of the ultra-long single-walled carbon nanotube between the gold nanorods in the close packed state in the parallel arrangement under an electron microscope, and collecting a Raman spectrogram of the single-walled carbon nanotube by using 785nm laser under a microscopic confocal Raman spectrometer.
Plasma element resonance peak energy of the gold nanorod patterns in the orderly close packing is well matched with 785nm laser, and in-situ Raman spectrograms of the single-walled carbon nanotubes before and after the ultra-long single-walled carbon nanotubes and the gold nanorod patterns in the self-organized close packing are compounded are measured. In the carbon nano tube without defects, the D mode can not be detected by the conventional Raman spectrum, and after the carbon nano tube is compounded with the gold nano rods in the close packed in the same row, the strong D mode can be detected besides the Raman enhancement caused by the surface plasma elements, so that the electric field gradient Raman scattering breaks the selection rule of the conventional Raman scattering, and the detection of the central phonon mode of the non-Brillouin area is realized.
In a third embodiment, which may be described in conjunction with fig. 2 and 4, a detection method for selecting a rule-inhibiting phonon mode may include:
step (1): preparing a horizontal array of the ultra-long single-walled carbon nanotubes on the Si/SiOx substrate containing the positioning marks by using a chemical vapor deposition method, and collecting the Raman spectrum of the single ultra-long single-walled carbon nanotube according to the positioning marks.
Step (2): preparing a 30 nm-diameter gold @ palladium core-shell structure polyhedral dilute solution, dripping 30 mu L of the dilute solution on a position of a marked substrate with an ultra-long single-walled carbon nanotube, and baking for 30min under an incandescent lamp to form a self-organized close-packed gold @ palladium core-shell structure pattern.
And (3): finding the position of the ultralong single-walled carbon nanotube and the self-organized close-packed gold @ palladium core-shell structure pattern under an electron microscope, and collecting a Raman spectrogram of the single-walled carbon nanotube by using 785nm laser under a microscopic confocal Raman spectrometer.
The plasmon resonance peak of the self-organized close-packed gold @ palladium core-shell structure pattern can be well matched with 785nm laser. And measuring in-situ Raman spectrograms of the single-walled carbon nanotubes before and after the ultra-long single-walled carbon nanotubes are compounded with the close-packed gold @ palladium core-shell structure pattern. In the carbon nano tube without defects, the D mode cannot be detected by the conventional Raman spectrum, and after the carbon nano tube is compounded with the gold nano particle close-packed pattern, besides Raman enhancement caused by surface plasma elements, the strong D mode can be detected, so that the electric field gradient Raman scattering breaks the selection rule of the conventional Raman scattering, and the detection of the central phonon mode of the non-Brillouin area is realized.
In a fourth embodiment, which may be described in conjunction with fig. 2 and 4, a detection method for selecting a rule-inhibiting phonon mode may include:
step (1): preparing single crystal graphene on a Si/SiOx substrate containing a positioning mark by using a chemical vapor deposition method, and collecting a Raman spectrum of the single crystal graphene according to the positioning mark.
Step (2): preparing a polyhedral gold nanoparticle dilute solution with the diameter of 30nm, dripping 30 mu L of the dilute solution on the position of a marking substrate with single crystal graphene, and baking for 15min under an incandescent lamp to form a hexagonal close-packed gold nanoparticle pattern.
And (3): finding the position of the single crystal graphene and the hexagonal close-packed gold nanoparticle pattern under an electron microscope, and collecting a Raman spectrogram of the single crystal graphene by using 785nm laser under a microscopic confocal Raman spectrometer.
In the single crystal graphene without defects, a D mode cannot be detected by a conventional Raman spectrum, and after the single crystal graphene is compounded with a gold nanoparticle close-packed pattern, a strong D mode can be detected besides Raman enhancement caused by surface plasma elements, so that the selection rule of the conventional Raman scattering can be broken by electric field gradient Raman scattering, and the detection of a non-Brillouin zone central phonon mode is realized.
In a fifth embodiment, which may be described in conjunction with fig. 3 and 5, a detection method for selecting a rule-inhibiting phonon mode may include:
step (1): preparing a 30 nm-diameter polyhedral gold nanoparticle dilute solution, dripping 30 mu L of dilute solution on a marked Si/SiOx substrate, and baking for 15min under an incandescent lamp to form a hexagonal close-packed gold nanoparticle pattern.
Step (2): and preparing the single crystal graphene by using a chemical vapor deposition method. And transferring the single crystal graphene to a hexagonal close-packed gold nanoparticle pattern with a positioning mark substrate.
And (3): finding the position of the single crystal graphene and the hexagonal close-packed gold nanoparticle pattern under an electron microscope, and respectively acquiring Raman spectrograms of the single crystal graphene at the position with or without the hexagonal close-packed gold nanoparticle pattern by using 785nm laser under a microscopic confocal Raman spectrometer. Therefore, in-situ Raman spectrograms of the single crystal graphene before and after the single crystal graphene and the hexagonal close-packed gold nanoparticle pattern are compounded can be measured. In the single crystal graphene without defects, a D mode cannot be detected by a conventional Raman spectrum, and after the single crystal graphene is compounded with a gold nanoparticle close-packed pattern, besides Raman enhancement caused by surface plasma elements, a strong D mode can be detected, so that the selection rule of the conventional Raman scattering can be broken by electric field gradient Raman scattering, and the detection of a non-Brillouin zone center phonon mode is realized.
Thus, it should be understood by those skilled in the art that while exemplary embodiments of the present invention have been illustrated and described in detail herein, many other variations or modifications which are consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.
Claims (10)
1. A detection method for selecting a rule-inhibiting phonon mode, comprising:
preparing a material to be characterized and a monolayer tightly-packed metal particle pattern, wherein the metal particles are tightly arranged with each other to form a gap with a preset size, the preset size is less than 10nm, the material to be characterized has no defects, and the monolayer tightly-packed metal particle pattern is prepared by a self-assembly method;
collecting electric field gradient Raman spectrum of the material to be characterized in the gap of the metal particles;
after the material to be characterized is detected to be compounded with the metal particle patterns which are mutually and tightly arranged and form the gap with the preset scale range according to the electric field gradient Raman spectrum, besides Raman enhancement caused by surface plasma elements, a strong D mode can be detected, and detection of a central phonon mode of a non-Brillouin zone is realized.
2. The detection method according to claim 1, wherein preparing a pattern of metal particles to be characterized and a monolayer of close-packed metal particles so that the metal particles are closely arranged to each other and form gaps having a predetermined range of dimensions comprises:
preparing the material to be characterized on a substrate;
preparing the single-layer closely-packed metal particle pattern on the material to be characterized, and enabling the metal particles to be closely arranged with each other and form gaps with preset sizes.
3. The detection method according to claim 1, wherein preparing a pattern of metal particles to be characterized and a monolayer of close-packed metal particles so that the metal particles are closely arranged to each other and form gaps having a predetermined range of dimensions comprises:
preparing the single-layer closely-packed metal particle pattern on a substrate, and enabling the metal particles to be mutually closely arranged to form a gap with a preset size;
preparing the material to be characterized on the monolayer of closely packed metal particle patterns.
4. The detection method according to claim 1,
the material to be characterized is selected from non-metallic materials which can be characterized by Raman spectroscopy and can be coupled with the metal particle plasma element structure to realize Raman enhancement.
5. The detection method according to any one of claims 1 to 4,
the preset dimension is less than 5 nm.
6. The detection method according to any one of claims 1 to 4,
the size and shape of the metal particles are selected so that their plasmon resonance peaks match the wavelength of the excitation laser.
7. The detection method according to any one of claims 1 to 4,
the metal particles are metal particles having surface plasmon resonance, and the structure composed of the metal particles is a nanostructure having surface plasmon resonance.
8. The detection method according to any one of claims 1 to 4,
the metal particle material comprises a simple metal and/or an alloy and/or a heterostructure.
9. The detection method according to claim 1,
the material to be characterized is a one-dimensional nanowire or nanorod or nanotube.
10. The detection method according to claim 1,
the material to be characterized comprises an organic molecular material, a carbon nanotube material, graphene and/or a monolayer of molybdenum sulfide.
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