A molecular carrier for single-molecule detection

Abstract

The present invention relates to a molecular carrier for single molecule detection, which comprises a substrate and a metal layer arranged on the surface of the substrate; wherein the substrate comprises a base and a plurality of patterned protrusions arranged on the surface of the base, the patterned protrusions comprising a plurality of protrusions arranged crosswise to form a mesh structure, thereby defining a plurality of holes; the metal layer is arranged on the surface of the patterned protrusions. The molecular carrier of the present invention has the following beneficial effects: the metal layer is arranged on the surface of the patterned protrusions, and the patterned protrusions comprise a plurality of protrusions arranged crosswise to form a mesh structure, therefore, under the excitation of the external incident photoelectric magnetic field, the metal surface plasma undergoes resonance absorption, and the cross-arranged protrusions play the role of surface enhanced Raman scattering, which can improve the SERS enhancement factor and enhance Raman scattering.

Description

Technical Field

[0001] The invention relates to a molecular carrier for single molecule detection, a preparation method thereof and a method for detecting single molecules by using the carrier. Background Art

[0002] Single Molecule Detection (SMD) technology is different from general conventional detection technology. It observes the individual behavior of a single molecule. Single molecule detection technology is widely used in environmental safety, biotechnology, sensors, food safety and other fields. Single molecule detection reaches the limit of molecular detection and has been a goal that people have been pursuing for a long time. Compared with traditional analytical methods, single molecule detection studies the individual behavior of the system in a non-equilibrium state, or the fluctuating behavior in an equilibrium state. Therefore, it is particularly suitable for studying chemical and biochemical reaction dynamics, the interaction of biological molecules, structure and function information, early diagnosis of major diseases, pathological research, and high-throughput drug screening.

[0003] At present, there are many known methods for single molecule detection, and the structure of the molecular carrier plays a very important role in the development of single molecule detection technology and the detection results. Among the existing single molecule detection methods, the structure of the molecular carrier is to coat colloidal silver on the glass surface, and the silver particles are adhered to the glass surface through the colloid, and then the glass with silver particles is ultrasonically washed to form dispersed silver particles on the glass surface to form a molecular carrier. Then the analyte molecules are set on the surface of the molecular carrier, and the Raman detection system is used to provide laser radiation to the analyte molecules on its molecular carrier. The photons in the laser collide with the analyte molecules, thereby changing the direction of the photons and generating Raman scattering. In addition, the photons exchange energy with the analyte molecules, changing the energy and frequency of the photons, so that the photons have the structural information of the analyte molecules. The radiation signal from the analyte molecules is received by the sensor to form a Raman spectrum, and the analyte molecules are analyzed by a computer.

[0004] However, in the prior art, since the surface of the glass is a flat planar structure, the generated Raman scattering signal is not strong enough, so that the resolution of the single molecule detection is low and it is not suitable for the detection of low-concentration and trace samples, thus limiting the scope of application. Summary of the invention

[0005] In view of this, it is indeed necessary to provide a molecular carrier that can improve the resolution of single-molecule detection.

[0006] A molecular carrier for single molecule detection comprises a substrate and a metal layer arranged on the surface of the substrate; wherein the substrate comprises a base and a plurality of patterned protrusions arranged on the surface of the base, the patterned protrusions comprising a plurality of protrusions arranged crosswise to form a mesh structure, thereby defining a plurality of holes; the metal layer is arranged on the surface of the patterned protrusions.

[0007] As in the above molecular carrier, further, the plurality of convex strips include a plurality of first convex strips extending along a first direction and a plurality of second convex strips extending along a second direction, and an angle between the first direction and the second direction is greater than or equal to 30 degrees and less than or equal to 90 degrees.

[0008] As in the above molecular carrier, further, the width of the convex strip is 20 nanometers to 150 nanometers, the height is 50 nanometers to 1000 nanometers, and the spacing between two adjacent parallel convex strips is 10 nanometers to 300 nanometers.

[0009] As in the above molecular carrier, further, the width of the convex strip is 20 nanometers to 50 nanometers, the height is 500 nanometers to 1000 nanometers, and the spacing between two adjacent parallel convex strips is 10 nanometers to 50 nanometers.

[0010] As the above molecular carrier, further, the metal layer is a continuous layered structure and is arranged on the surface of the plurality of convex strips and in the holes between the convex strips.

[0011] As the above molecular carrier, further, the metal layer is a discontinuous layered structure, and is only arranged on the side walls of the convex strips and the substrate surface between adjacent convex strips.

[0012] As the above molecular carrier, further, the material of the metal layer is one or more of gold, silver, platinum, copper, iron and aluminum.

[0013] As the above molecular carrier, it further comprises a carbon nanotube composite structure disposed between the top surface of the patterned protrusion and the metal layer, and the carbon nanotube composite structure has the same pattern as the patterned protrusion.

[0014] As the above molecular carrier, further, the carbon nanotube composite structure includes a carbon nanotube structure and a prefabricated layer coated on the surface of the carbon nanotube structure, and the carbon nanotube structure includes a plurality of cross-arranged carbon nanotubes.

[0015] As the above molecular carrier, further, the carbon nanotube structure includes two stacked and cross-arranged carbon nanotube films, and the carbon nanotubes in the carbon nanotube films are connected end to end by van der Waals forces and arranged in the same direction.

[0016] As the above-mentioned molecular carrier, further, the material of the prefabricated layer is one or more of metal, metal oxide, metal sulfide, non-metal oxide, non-metal carbide and non-metal nitride.

[0017] Compared with the prior art, the molecular carrier of the present invention has the following beneficial effects: the metal layer is arranged on the surface of the patterned protrusions, and the patterned protrusions include a plurality of convex strips cross-arranged to form a mesh structure. Therefore, under the excitation of the external incident photoelectric magnetic field, the metal surface plasma undergoes resonant absorption, and the cross-arranged convex strips play a role in surface enhanced Raman scattering, which can improve the SERS (Surface enhanced Raman scattering) enhancement factor and enhance Raman scattering. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the molecular carrier provided in the first embodiment of the present invention.

[0019] Figure 2 A cross-sectional view of the molecular carrier provided in the first embodiment of the present invention along the II-II direction.

[0020] Figure 3 This is a scanning electron microscope photograph of the substrate surface of the molecular carrier provided in the first embodiment of the present invention.

[0021] Figure 4 for Figure 3 A partial enlargement of the scanning electron microscope photograph.

[0022] Figure 5 This is a flow chart of the method for preparing a molecular carrier provided in the first embodiment of the present invention.

[0023] Figure 6 Figure 5 Cross-sectional view of the carbon nanotube composite structure along line VI-VI.

[0024] Figure 7 This is a scanning electron microscope photograph of the carbon nanotube film used in the first embodiment of the present invention.

[0025] Figure 8 This is a scanning electron microscope photograph of the non-twisted carbon nanotube wire used in the first embodiment of the present invention.

[0026] Fig. 9 This is a scanning electron microscope photograph of the twisted carbon nanotube wire used in the first embodiment of the present invention.

[0027] Fig.10 This is a scanning electron microscope photograph of the carbon nanotube composite structure provided in the first embodiment of the present invention.

[0028] Fig.11This is a scanning electron microscope photograph of a single carbon nanotube coated with an aluminum oxide layer in the carbon nanotube composite structure provided in the first embodiment of the present invention.

[0029] Fig.12 This is a scanning electron microscope photograph of the top surface of the molecular carrier prepared in the first embodiment of the present invention.

[0030] Fig.13 This is a cross-sectional scanning electron microscope photograph of the molecular carrier prepared in the first embodiment of the present invention.

[0031] Fig.14 This is a flow chart of the single molecule detection method provided in the first embodiment of the present invention.

[0032] Fig.15 The single molecule detection method provided in the first embodiment of the present invention detects the Raman spectrum detection result of the rhodamine molecule.

[0033] Fig.16 This is a schematic diagram of the structure of a molecular carrier provided in the second embodiment of the present invention.

[0034] Fig.17 This is a flow chart of the method for preparing a molecular carrier provided in the second embodiment of the present invention.

[0035] Fig.18 This is a schematic diagram of the structure of a molecular carrier provided in the third embodiment of the present invention.

[0036] Main component symbols

[0037] Molecular carrier 10,

[0038] Substrate 12

[0039] Base 120

[0040] Surface 121

[0041] Patterned protrusions 122

[0042] Hole 124

[0043] Metal layer 14

[0044] Detection of molecules 16

[0045] Raman spectroscopy 18

[0046] Carbon nanotube composite structure 110

[0047] Carbon Nanotube Structure 112

[0048] Prefabricated layer 114 DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] See also Figures 1 to 4 The first embodiment of the present invention provides a molecular carrier 10 for single molecule detection, and the molecular carrier 10 includes a substrate 12 and a metal layer 14 disposed on the surface of the substrate 12. The substrate 12 includes a base 120 and a plurality of patterned protrusions 122 disposed on the base 120. The patterned protrusions 122 include a plurality of protrusions arranged crosswise to form a mesh structure, thereby defining a plurality of holes 124. The intersection of the plurality of protrusions is an integrated structure.

[0051] The substrate 12 may be an insulating substrate or a semiconductor substrate. Specifically, the material of the substrate 12 may be silicon, silicon dioxide, silicon nitride, quartz, glass, gallium nitride, gallium arsenide, sapphire, aluminum oxide or magnesium oxide, etc. The shape of the substrate 12 is not limited, and it only needs to have two oppositely disposed surfaces. In the present embodiment, the shape of the substrate 12 is a flat plate. The size and thickness of the substrate 12 are not limited and can be selected according to the actual needs of single molecule detection. In the present embodiment, the substrate 12 is a silicon wafer.

[0052] The substrate 120 and the convex strips can be an integral structure of the same material or a multilayer structure of different materials. The convex strips can be arranged on one surface of the substrate 120 or respectively arranged on two opposite surfaces of the substrate 120. The present invention defines a portion of the convex strips extending along the first direction as the first convex strips, and another portion of the convex strips extending along the second direction as the second convex strips. The angle between the first direction and the second direction is greater than 0 degrees and less than or equal to 90 degrees, preferably, greater than or equal to 30 degrees. The multiple first convex strips are substantially parallel, and the multiple second convex strips are substantially parallel. The feature that the convex strips of the present invention are substantially parallel is determined by the feature that the extension direction of the carbon nanotubes in the carbon nanotube mask used in the preparation method thereof is substantially parallel. The length of each convex strip is not limited, the width is 20 nanometers to 150 nanometers, the height is 50 nanometers to 1000 nanometers, and the spacing between parallel and adjacent convex strips is 10 nanometers to 300 nanometers. Therefore, the opening size of the hole 124 is 10 nanometers to 300 nanometers, and the depth is 50 nanometers to 1000 nanometers. Preferably, each convex strip has a width of 20 nm to 50 nm, a height of 500 nm to 1000 nm, and a spacing of 10 nm to 50 nm. In this embodiment, the plurality of first convex strips are perpendicular to the plurality of second convex strips. The convex strips extend from one side of the substrate 120 to the other side.

[0053] The metal layer 14 is arranged on the surface of the plurality of convex strips and in the holes 124 between the convex strips. The metal layer 14 can be a continuous layered structure or a discontinuous layered structure. The metal layer 14 can be a single-layer layered structure or a multi-layer layered structure. The metal layer 14 is substantially uniformly deposited on the surface of the convex strips and the surface of the substrate 120 between the convex strips. A gap (Gap) is formed at the hole 124, where surface plasma resonance exists on the surface of the metal layer 14, thereby generating Raman scattering enhancement. The thickness of the metal layer 14 is 2 nanometers to 200 nanometers, and preferably, the thickness of the metal layer 14 is uniform. The material of the metal layer 14 is not limited, and can be metals such as gold, silver, platinum, copper, iron or aluminum. It can be understood that the material of the metal layer 14 is not limited to the above, and any metal material that is solid at room temperature can be used. In this embodiment, the metal layer 14 is gold with a thickness of 20 nanometers.

[0054] See also Figure 5 as well as Figure 6 The first embodiment of the present invention provides a method for preparing the above-mentioned molecular carrier 10, which comprises the following steps:

[0055] Step S10, providing a substrate 12;

[0056] Step S20, providing a carbon nanotube composite structure 110 having a plurality of micropores 116, wherein the carbon nanotube composite structure 110 includes a carbon nanotube structure 112 and a prefabricated layer 114 coated on the surface of the carbon nanotube structure 112, and the carbon nanotube structure 112 includes a plurality of cross-arranged carbon nanotubes;

[0057] Step S30, disposing the carbon nanotube composite structure 110 on a surface 121 of the substrate 12, so that the surface 121 of the substrate 12 is partially exposed;

[0058] Step S40, dry-etching the substrate 12 using the carbon nanotube composite structure 110 as a mask, thereby obtaining a substrate 12 having a patterned protrusion 122, wherein the patterned protrusion 122 includes a plurality of cross-arranged protrusions;

[0059] Step S50, removing the carbon nanotube composite structure 110;

[0060] In step S60 , a metal layer 14 is deposited on the surface of the patterned protrusion 122 .

[0061] In step S10, the material of the substrate 12 is not limited, and can be an insulating substrate formed of materials such as silicon dioxide and silicon nitride, a metal substrate formed of materials such as gold, aluminum, nickel, chromium, copper, or a semiconductor substrate formed of materials such as silicon, gallium nitride, and gallium arsenide, as long as the substrate 12 can be etched in the subsequent etching process. The size and thickness of the substrate 12 can be selected as needed. In this embodiment, the substrate 12 is a gallium nitride with a thickness of 300 microns.

[0062] In the step S20, the carbon nanotube structure 112 includes a plurality of carbon nanotubes arranged in an orderly manner and arranged crosswise to form a plurality of micropores, and the prefabricated layer 114 is coated on the surface of the plurality of carbon nanotubes. Preferably, the prefabricated layer 114 is coated on the entire surface of each carbon nanotube. The plurality of carbon nanotubes are tightly connected by van der Waals forces so that the carbon nanotube structure 112 and the carbon nanotube composite structure 110 form a self-supporting structure. The so-called self-supporting structure means that the structure can maintain a specific film-like structure without a support. Therefore, the carbon nanotube composite structure 110 is self-supporting and can be partially suspended. The carbon nanotubes include one or more of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes. The carbon nanotubes are parallel to the surface of the carbon nanotube structure 112. The diameter of the single-walled carbon nanotube is 0.5 nanometers to 10 nanometers, the diameter of the double-walled carbon nanotube is 1.0 nanometers to 15 nanometers, and the diameter of the multi-walled carbon nanotube is 1.5 nanometers to 50 nanometers. The length of the carbon nanotube is greater than 50 micrometers. Preferably, the length of the carbon nanotube is 200 micrometers to 900 micrometers.

[0063] The carbon nanotube structure 112 includes at least one carbon nanotube film, at least one carbon nanotube wire or a combination thereof. The carbon nanotube film includes a plurality of uniformly distributed carbon nanotubes. The plurality of carbon nanotubes in the carbon nanotube film extend in one direction, and the plurality of carbon nanotubes form a plurality of carbon nanotube bundles, and the extension direction of the carbon nanotubes is parallel to the surface of the carbon nanotube film. Specifically, the carbon nanotube film may include a carbon nanotube pulling film. The carbon nanotube wire may be a non-twisted carbon nanotube wire or a twisted carbon nanotube wire. When the carbon nanotube structure 112 includes a plurality of carbon nanotube wires, the plurality of carbon nanotube wires are parallel to each other and spaced apart and cross-arranged at a certain angle to form a layered carbon nanotube structure. The layered carbon nanotube structure includes a plurality of micropores, which are through holes that penetrate the thickness direction of the layered carbon nanotube structure. The size of the micropore is 1 nanometer to 0.5 micrometer.

[0064] See also Figure 7Specifically, the carbon nanotube film includes a plurality of continuous and directional carbon nanotube bundles. The plurality of carbon nanotube bundles are connected end to end by van der Waals forces. Each carbon nanotube bundle includes a plurality of carbon nanotubes parallel to each other, and the plurality of carbon nanotubes parallel to each other are tightly bound by van der Waals forces. The diameter of the carbon nanotube bundle is 10 nanometers to 200 nanometers, preferably 10 nanometers to 100 nanometers. The carbon nanotubes in the carbon nanotube film are preferentially oriented and arranged in the same direction. The carbon nanotube film includes a plurality of micropores. The micropore is a through hole that runs through the thickness direction of the layered carbon nanotube structure. The micropore can be a pore and / or a gap. When the carbon nanotube structure 112 includes only a single-layer carbon nanotube film, there is a gap between adjacent carbon nanotube segments in the carbon nanotube film, wherein the size of the gap is 1 nanometer to 0.5 micrometer. It can be understood that in the carbon nanotube structure 112 composed of multiple layers of carbon nanotube film, the arrangement direction of the carbon nanotubes in two adjacent carbon nanotube films has an angle α, and 0°<α≤90°, so that the carbon nanotubes in the two adjacent layers of carbon nanotube film cross each other to form a network structure, and the network structure includes a plurality of pores, and the plurality of pores are evenly and regularly distributed in the carbon nanotube structure 112, wherein the pore diameter is 1 nanometer to 0.5 micrometer. The thickness of the carbon nanotube film is 0.01 micrometer to 100 micrometers. The carbon nanotube film can be directly obtained by drawing a carbon nanotube array. For the structure of the carbon nanotube film and its preparation method, please refer to the Chinese patent No. CN101239712B "Carbon Nanotube Film Structure and Preparation Method thereof" applied by Fan Shoushan et al. on February 9, 2007 and announced on May 26, 2010, applicants: Tsinghua University, Hongfujin Precision Industry (Shenzhen) Co., Ltd. To save space, it is only cited here, but all technical disclosures of the above application should also be regarded as part of the technical disclosures of the present application.

[0065] See also Figure 8, the non-twisted carbon nanotube wire includes a plurality of carbon nanotubes arranged along the length direction of the non-twisted carbon nanotube wire. Specifically, the non-twisted carbon nanotube wire includes a plurality of carbon nanotube segments, the plurality of carbon nanotube segments are connected end to end by van der Waals force, and each carbon nanotube segment includes a plurality of carbon nanotubes that are parallel to each other and tightly bound by van der Waals force. The carbon nanotube segment has any length, thickness, uniformity and shape. The length of the non-twisted carbon nanotube wire is not limited, and the diameter is 0.5 nanometers to 100 micrometers. The non-twisted carbon nanotube wire is obtained by treating the carbon nanotube film with an organic solvent. Specifically, the organic solvent is soaked on the entire surface of the carbon nanotube film, and under the action of the surface tension generated when the volatile organic solvent evaporates, the plurality of carbon nanotubes that are parallel to each other in the carbon nanotube film are tightly bound by van der Waals force, so that the carbon nanotube film is shrunk into a non-twisted carbon nanotube wire. The organic solvent is a volatile organic solvent, such as ethanol, methanol, acetone, dichloroethane or chloroform, and ethanol is used in this embodiment. The non-twisted carbon nanotube wire treated with an organic solvent has a smaller specific surface area and lower viscosity than the carbon nanotube film not treated with an organic solvent.

[0066] The twisted carbon nanotube wire is obtained by twisting the two ends of the carbon nanotube film in opposite directions using a mechanical force. Fig. 9 , the twisted carbon nanotube wire includes a plurality of carbon nanotubes spirally arranged around the axial direction of the twisted carbon nanotube wire. Specifically, the twisted carbon nanotube wire includes a plurality of carbon nanotube segments, the plurality of carbon nanotube segments are connected end to end by van der Waals force, and each carbon nanotube segment includes a plurality of carbon nanotubes parallel to each other and tightly bound by van der Waals force. The carbon nanotube segments have any length, thickness, uniformity and shape. The length of the twisted carbon nanotube wire is not limited, and the diameter is 0.5 nanometers to 100 micrometers. Further, the twisted carbon nanotube wire can be treated with a volatile organic solvent. Under the action of the surface tension generated when the volatile organic solvent evaporates, the adjacent carbon nanotubes in the twisted carbon nanotube wire after treatment are tightly bound by van der Waals force, so that the specific surface area of ​​the twisted carbon nanotube wire is reduced, and the density and strength are increased.

[0067] For the carbon nanotube linear structure and its preparation method, please refer to the Chinese patent application No. CN100411979C filed by Fan Shoushan et al. on September 16, 2002 and published on August 20, 2008, “A carbon nanotube rope and its manufacturing method”, applicants: Tsinghua University, Hongfujin Precision Industry (Shenzhen) Co., Ltd., and the Chinese patent application No. CN100500556C filed on December 16, 2005 and published on June 17, 2009, “Carbon nanotube filament and its manufacturing method”, applicants: Tsinghua University, Hongfujin Precision Industry (Shenzhen) Co., Ltd. In order to save space, only this is cited, but all technical disclosures of the above applications should also be regarded as part of the technical disclosures of the present invention.

[0068] In this embodiment, the carbon nanotube structure 112 is a two-layer vertically crossed carbon nanotube film, which is directly drawn from a grown carbon nanotube array. Multiple carbon nanotubes in the carbon nanotube structure 112 are connected end to end by van der Waals forces and arranged in the same direction.

[0069] The material of the prefabricated layer 114 may be at least one of metals such as gold, nickel, titanium, iron, aluminum, titanium, chromium, etc., metal oxides such as aluminum oxide, magnesium oxide, zinc oxide, hafnium oxide, or metal sulfides. It is understood that the material of the prefabricated layer 114 is not limited to the above-mentioned materials, and can also be non-metallic oxides such as silicon dioxide, non-metallic carbides such as silicon carbide, or non-metallic nitrides such as silicon nitride, etc., as long as it can be physically deposited on the surface of the carbon nanotube structure 112 and is not etched during the subsequent etching of the substrate 12. The physical deposition means that the prefabricated layer 114 does not chemically react with the carbon nanotube structure 112, but is tightly combined with the carbon nanotube structure 112 through van der Waals forces and attached to the surface of the carbon nanotubes in the carbon nanotube structure 112. The thickness of the prefabricated layer 114 is not limited, and can be 3 nanometers to 50 nanometers. In order to obtain nanometer-sized nanowire arrays 105 and prevent the micropores in the carbon nanotube structure 112 from being excessively covered by the prefabricated layer 114, the thickness of the prefabricated layer 114 is preferably 3 nanometers to 20 nanometers. The micropores 116 of the carbon nanotube composite structure 110 have a smaller pore size than the micropores in the carbon nanotube structure 112.

[0070] The carbon nanotube composite structure 110 can be prepared by the following method: first, at least a portion of the carbon nanotube structure 112 is suspended in the air; then, a prefabricated layer 114 is deposited on the surface of the carbon nanotube structure 112 .

[0071] The carbon nanotube structure 112 has two opposite surfaces. The carbon nanotube structure 112 can be fixed by a frame, and the part located inside the frame is suspended, so that the carbon nanotube structure 112 is fully exposed, so as to facilitate the subsequent simultaneous formation of the prefabricated layer 114 on the two opposite surfaces of the carbon nanotube structure 112. The frame is a hollow structure with a through hole. The edge of the carbon nanotube structure 112 can be fixed in the frame, and the part located in the middle is exposed through the through hole and is suspended. Through the frame, the edge of the carbon nanotube structure 112 can be firmly fixed, and the carbon nanotube structure 112 located at the through hole position is kept fully exposed. In this embodiment, the frame is a "mouth"-shaped frame, and the edge of the carbon nanotube structure 112 is fixed by the frame. It can be understood that the carbon nanotube structure 112 can also be suspended by other means, such as a metal grid, a ring body with a hollow structure, etc., as long as the carbon nanotube structure 112 is suspended. The prefabricated layer 114 can be deposited on the surface of the carbon nanotube structure 112 by electron beam evaporation. It is understood that the deposition method is not limited to the above-mentioned methods, and can also be a vapor deposition method such as magnetron sputtering and atomic layer deposition, as long as the prefabricated layer 114 does not destroy the morphology and structure of the carbon nanotube structure 112 during the deposition process.

[0072] Since the carbon nanotube structure 112 is suspended, both surfaces of the carbon nanotube structure 112 are covered by the prefabricated layer 114. Specifically, the prefabricated layer 114 covers at least part of the surface of multiple carbon nanotubes in the carbon nanotube structure 112. The carbon nanotube structure 112 includes multiple microporous structures. It can be understood that the prefabricated layer 114 can also be distributed in the microporous structure. The carbon nanotubes in the carbon nanotube structure 112 are tightly combined with the prefabricated layer 114 to form an integral carbon nanotube composite structure 110. Among them, the carbon nanotube structure 112 plays a supporting role for the prefabricated layer 114. The carbon nanotube composite structure 110 includes multiple micropores 116. The micropores 116 are recessed spaces that run through the thickness direction of the carbon nanotube composite structure 110, and the recessed spaces can be gaps or micropores.

[0073] In this embodiment, the carbon nanotube composite structure 110 is obtained by arranging a prefabricated layer 114 on the surface of the carbon nanotube structure 112 by electron beam evaporation. The material of the prefabricated layer 114 is aluminum oxide, and the thickness of the prefabricated layer 114 is 5 nanometers. Each carbon nanotube in the carbon nanotube structure 112 is completely covered by the prefabricated layer 114. Fig.10 , is a scanning electron microscope photo of the carbon nanotube composite structure 110 used in this embodiment. Fig.11, is a scanning electron microscope photograph of a single carbon nanotube coated with an aluminum oxide layer in the carbon nanotube composite structure 110 used in this embodiment.

[0074] In the step S30, the carbon nanotube composite structure 110 can be directly disposed on the surface 121 of the substrate 12. Specifically, the frame and the carbon nanotube composite structure 110 can be transferred to the surface 121 of the substrate 12 together, and then the frame can be removed. Since the carbon nanotube composite structure 110 has a plurality of micropores 116, a portion of the surface 121 of the substrate 12 is exposed through the plurality of micropores 116. The carbon nanotube composite structure 110 is not in completely close contact with the surface 121 of the substrate 12, and air may exist between a portion of the carbon nanotube composite structure 110 and the surface 121 of the substrate 12.

[0075] After the carbon nanotube composite structure 110 is disposed on the surface 121 of the substrate 12, a step of treating the carbon nanotube composite structure 110 with a solvent so that the carbon nanotube composite structure 110 is attached to the surface 121 of the substrate 12 may be further included. When a solvent is dripped onto the surface of the carbon nanotube composite structure 110, the solvent will infiltrate the carbon nanotube composite structure 110, soften the carbon nanotube composite structure 110, and discharge the air between the carbon nanotube composite structure 110 and the surface 121 of the substrate 12. When the solvent is removed, the carbon nanotube composite structure 110 forms a close contact with the surface 121 of the substrate 12. The solvent may be water, an organic solvent, etc. The organic solvent is a volatile organic solvent, such as ethanol, methanol, acetone, ethylene dichloride, and chloroform. In this embodiment, the solvent is ethanol. The ethanol is dripped onto the surface of the carbon nanotube composite structure 110 and then naturally dried, so that the carbon nanotube composite structure 110 is closely attached to the surface 121 of the substrate 12 .

[0076] In the step S40, the dry etching refers to the process of introducing a gas to obtain a plasma under the action of an electric field, and the plasma can react with the etched material to obtain a volatile substance, such as inductively coupled plasma etching (ICPE) and reactive ion etching (RIE). In the present embodiment, the surface 121 of the exposed substrate 12 is etched by inductively coupled plasma etching. Specifically, by introducing a gas into a plasma system, the gas can be oxygen, chlorine, hydrogen, chlorine, argon, carbon tetrafluoride, etc. The gas is not limited to the above-mentioned gases, as long as the gas can react with the substrate 12. Preferably, the substrate 12 is etched by reactive ion etching of chlorine and argon, wherein the power of the plasma system is 20 watts to 70 watts, the introduction rate of the chlorine plasma is 10 standard-state cubic centimeter per minute (sccm), the introduction rate of the argon plasma is 25 sccm, the formed gas pressure is 6 Pa, and the etching time is 10 seconds to 60 seconds. The exposed surface of the substrate 12 is partially etched by reactive ion etching. Since the plasma fully reacts with the substrate 12, the reaction time of the process is short and the efficiency is high.

[0077] During the process of etching the substrate 12, the etching gas chemically reacts with the exposed portion of the substrate 12, but does not chemically react with the prefabricated layer 114 of the carbon nanotube composite structure 110, or the speed and degree of chemical reaction with the prefabricated layer 114 is much lower than the chemical reaction between the etching gas and the substrate 12. That is, the carbon nanotube composite structure 110 acts as a mask. The materials of the etching gas and the substrate 12 and the materials of the prefabricated layer 114 can be seen in Table 1 below.

[0078] Table 1 Correspondence between etching gas and substrate material and prefabricated layer material

[0079]

[0080] During the etching process, since the selected etching gas does not chemically react with the prefabricated layer 114 but chemically reacts with the substrate 12, the surface of the exposed substrate 12 will be gradually etched, while the surface of the substrate 12 covered by the carbon nanotube composite structure 110 will not change. In addition, since the carbon nanotube composite structure 110 is tightly combined with the surface of the substrate 12, the pattern formed by the surface of the substrate 12 covered by the carbon nanotube composite structure 110 is consistent with the pattern formed by the forward projection of the carbon nanotube composite structure 110 onto the substrate 12 when the carbon nanotube composite structure 110 is suspended in the air. That is, the overall pattern of the patterned protrusions 122 obtained in the end is basically consistent with the overall pattern of the carbon nanotube composite structure 110.

[0081] In this embodiment, when the carbon nanotube structure 112 adopts a multi-layer cross carbon nanotube film, the patterned protrusions 122 with different patterns can be obtained by changing the cross angle of adjacent carbon nanotube films. When a forward cross carbon nanotube film is used as the carbon nanotube structure, the obtained patterned protrusions 122 include a plurality of convex strips arranged crosswise along two perpendicular directions.

[0082] The convex strips of the patterned protrusions 122 are strip-like or strip-like structures. The width of the convex strips is 20 nanometers to 150 nanometers. The spacing between two adjacent widths in the direction perpendicular to the extension direction of the carbon nanotubes is 10 nanometers to 300 nanometers. The size of the convex strips of the patterned protrusions 122 in the direction perpendicular to the surface of the substrate 12 is defined as the height of the convex strips. The height of the convex strips is not limited and can be determined according to the specific etching time, and can be 50 nanometers to 1000 nanometers. The multiple convex strips are perpendicular to each other and cross-distributed to form a mesh structure. See Figure 3-4 , is a scanning electron microscope photograph of the patterned protrusions 122 prepared in this embodiment. In this embodiment, the width of the protrusions is 20 nanometers to 50 nanometers, the spacing is 10 nanometers to 50 nanometers, and the height is 500 nanometers to 1000 nanometers.

[0083] It can be understood that, since the diameter of the composite structure after the carbon nanotubes in the carbon nanotube composite structure 110 are coated with the prefabricated layer 114 is tens of nanometers, and the spacing is tens of nanometers, the width and spacing of the convex strips of the prepared patterned protrusions 122 are also tens of nanometers. Therefore, the patterned protrusions 122 and the plurality of holes 124 on the surface of the substrate 12 are all nanostructures. Moreover, the spacing between adjacent convex strips and the spacing between adjacent holes 124 are both tens of nanometers, thus greatly improving the density of the nanostructure on the surface of the substrate 12, thereby improving the SERS enhancement factor and enhancing Raman scattering. For example, when the spacing between adjacent convex strips and the spacing between adjacent holes 124 are both 20 nanometers, within the width range of 1 micron, the number of the convex strips and the number of holes 124 are both 50. In the prior art, the preparation of microstructures usually adopts photolithography technology. Due to the resolution limitation, it is difficult to control the nanostructure scale of the protrusions and depressions within the range of tens of nanometers.

[0084] In the step S50, the method for removing the carbon nanotube composite structure 110 is not limited, and may be an ultrasonic method, a tearing method, an oxidation method, etc. In this embodiment, an ultrasonic method is used to remove the carbon nanotube composite structure 110. Specifically, the substrate 12 with the carbon nanotube composite structure 110 is placed in a solution of N-methylpyrrolidone and ultrasonicated for several minutes. Since the polarity of N-methylpyrrolidone is relatively large, the carbon nanotube composite structure 110 can be easily separated from the substrate 12.

[0085] In the step S60, the method of depositing the metal layer 14 on the surface of the patterned protrusion 122 is not limited, and electron beam evaporation, ion beam sputtering, atomic layer deposition, magnetron sputtering, evaporation, chemical vapor deposition, etc. can be used. The metal layer 14 is deposited on the surface of each convex strip and the surface of the substrate 12 between adjacent convex strips. The thickness of the metal layer 14 is 2 nanometers to 200 nanometers, and the material of the metal layer 14 is not limited, and can be a metal such as gold, silver, copper, iron or aluminum. In this embodiment, a 20-nanometer thick gold metal film is vertically evaporated on the surface of the substrate 12 to completely cover the patterned protrusions 122. Please refer to Fig.12 , is a scanning electron microscope photograph of the top surface of the molecular carrier 10 prepared in this embodiment. Fig.13 , is a cross-sectional scanning electron microscope photograph of the molecular carrier 10 prepared in this embodiment.

[0086] See also Fig.14 The first embodiment of the present invention further provides a single molecule detection method using the molecular carrier 10, and the detection method mainly includes the following steps:

[0087] Step (S11), providing a molecular carrier 10, wherein the molecular carrier 10 comprises a substrate 12 and a metal layer 14 disposed on the surface of the substrate 12; the substrate 12 comprises a base 120 and a plurality of patterned protrusions 122 disposed on the base 120; the patterned protrusions 122 comprise a plurality of protrusions cross-arranged to form a mesh structure, thereby defining a plurality of holes 124;

[0088] Step (S12), assembling the analyte molecules 16 on the surface of the metal layer 14 away from the substrate 12;

[0089] Step (S13), using a detector to detect the analyte molecules 16 assembled on the molecular carrier 10.

[0090] In the step (S12), the method of assembling the analyte molecules 16 on the surface of the metal layer 14 away from the substrate 12 mainly includes the following steps:

[0091] Step (S121), providing a solution of molecules of the analyte, wherein the molecular concentration of the analyte solution may be 10 - 7 mmol / L~10 -12 mmol / L can be prepared according to actual needs. The molecular concentration described in this embodiment is 10 -10 mmol / L;

[0092] Step (S122), immersing the molecular carrier 10 formed with the metal layer 14 into a solution of the substance to be detected, the immersion time can be 2 minutes to 60 minutes, preferably 10 minutes, so that the molecules of the substance to be detected are evenly dispersed on the surface of the metal layer 14;

[0093] Step (S123), taking out the molecular carrier 10, rinsing the molecular carrier with water or ethanol for 5 to 15 times, and then drying the molecular carrier 10 with a drying device such as a hair dryer to evaporate the residual water or ethanol, and assembling the analyte molecules 16 on the surface of the metal layer 14.

[0094] In the step (S13), the molecular carrier 10 assembled with the analyte molecules 16 is placed in a detection device, and the analyte molecules are detected by a detector such as a Raman spectrometer.

[0095] In this embodiment, about 10 -6 A solution of Rhodamine 6G with a concentration of 100 g / 100 ml is dropped on the surface of the metal layer 14 of the molecular carrier 10. The molecular carrier 10 assembled with the analyte molecules 16 is irradiated with a Raman spectrometer 18. The detection parameters of the Raman spectrometer are He-Ne: excitation wavelength 633 nanometers, excitation time 20 seconds, device power 9.0 mW, and working power 0.5 mW. Fig.15 This is the Raman spectrum detection result of rhodamine molecules.

[0096] The single molecule detection method provided by the present invention has the following advantages: the metal layer 14 is arranged on the surface of the patterned protrusion 122, and the patterned protrusion 122 includes a plurality of protrusions arranged crosswise to form a mesh structure. Therefore, under the excitation of the external incident photoelectric magnetic field, the metal surface plasma undergoes resonance absorption, and the cross-arranged protrusions play a role in surface enhanced Raman scattering, which can improve the SERS enhancement factor and enhance Raman scattering. The SERS enhancement factor is related to the spacing between adjacent protrusions. The smaller the distance, the greater the SERS enhancement factor. The theoretical value of the SERS enhancement factor can be 10 5 ~10 15 , so that better single molecule detection results can be obtained. The SERS enhancement factor of the molecular carrier 10 in this embodiment is greater than 10 10 In particular, the spacing between adjacent convex strips and the spacing between adjacent holes 124 are both tens of nanometers, thus greatly improving the density of the nanostructure on the surface of the substrate 12, further improving the SERS enhancement factor, and thus enhancing Raman scattering.

[0097] See also Fig.16The second embodiment of the present invention provides a molecular carrier 10A for single molecule detection, and the molecular carrier 10A includes a substrate 12 and a metal layer 14 disposed on the surface of the substrate 12. The substrate 12 includes a base 120 and a plurality of patterned protrusions 122 disposed on the base 120. The patterned protrusions 122 include a plurality of protrusions arranged crosswise to form a mesh structure, thereby defining a plurality of holes 124. The intersection of the plurality of protrusions is an integrated structure.

[0098] The molecular carrier 10A provided in the second embodiment of the present invention has a substantially similar structure to the molecular carrier 10 provided in the first embodiment, except that the metal layer 14 is a discontinuous structure. Specifically, the metal layer 14 is only disposed on the side walls of the convex strips and the surface of the substrate 120 between adjacent convex strips. That is, the metal layer 14 is only disposed on the side walls and bottom surface of the hole 124. The metal layer 14 may also be disposed only on the bottom surface of the hole 124.

[0099] See also Fig.17 The second embodiment of the present invention provides a method for preparing the above-mentioned molecular carrier 10A, which comprises the following steps:

[0100] Step S10A, disposing the carbon nanotube composite structure 110 on a surface 121 of the substrate 12, so that the surface 121 of the substrate 12 is partially exposed;

[0101] Step S20A, dry-etching the substrate 12 using the carbon nanotube composite structure 110 as a mask, thereby obtaining a substrate 12 having a patterned protrusion 122, wherein the patterned protrusion 122 includes a plurality of cross-arranged protrusions;

[0102] Step S30A, depositing a metal layer 14 on the surface of the patterned protrusion 122, and the metal layer 14 completely covers the patterned protrusion 122 and the carbon nanotube composite structure 110;

[0103] Step S40A: removing the carbon nanotube composite structure 110 .

[0104] The preparation method of the molecular carrier 10A provided in the second embodiment of the present invention is basically the same as the preparation method of the molecular carrier 10 provided in the first embodiment, the difference being that a metal layer 14 is first deposited on the surface of the patterned protrusion 122, and then the carbon nanotube composite structure 110 is removed. In step S30A, part of the metal layer 14 is deposited on the surface of the carbon nanotube composite structure 110, and the other part is deposited on the side of the protrusions on the surface of the substrate 12 and between adjacent protrusions. In step S40A, part of the metal layer 14 deposited on the surface of the carbon nanotube composite structure 110 is removed together with the carbon nanotube composite structure 110, forming a discontinuous metal layer 14 on the surface of the substrate 12. In the method of the second embodiment of the present invention, the carbon nanotube composite structure 110 serves as both a mask for etching the substrate 12 and a mask for depositing the metal layer 14, which not only saves the preparation cost but also improves the preparation efficiency.

[0105] The second embodiment of the present invention further provides a single molecule detection method using the molecular carrier 10A. This method is basically the same as the single molecule detection method using the molecular carrier 10 provided in the first embodiment of the present invention, except that different molecular carriers are used.

[0106] See also Fig.18 The third embodiment of the present invention provides a molecular carrier 10A for single molecule detection, wherein the molecular carrier 10B includes a substrate 12 and a carbon nanotube composite structure 110 and a metal layer 14 disposed on the surface of the substrate 12. The substrate 12 includes a base 120 and a plurality of patterned protrusions 122 disposed on the base 120. The patterned protrusions 122 include a plurality of protrusions arranged crosswise to form a mesh structure, thereby defining a plurality of holes 124. The intersection of the plurality of protrusions is an integrated structure.

[0107] The molecular carrier 10B provided in the second embodiment of the present invention has a substantially similar structure to the molecular carrier 10 provided in the first embodiment, except that it further comprises a carbon nanotube composite structure 110 disposed between the top surface of the patterned protrusion 122 and the metal layer 14. The metal layer 14 completely covers the patterned protrusion 122 and the carbon nanotube composite structure 110.

[0108] The third embodiment of the present invention further provides a method for preparing the molecular carrier 10B. The method is substantially the same as the method for preparing the molecular carrier 10A, except that the step S40A of removing the carbon nanotube composite structure 110 is not required.

[0109] The third embodiment of the present invention further provides a single molecule detection method using the molecular carrier 10B. This method is basically the same as the single molecule detection method using the molecular carrier 10 provided in the first embodiment of the present invention, except that different molecular carriers are used.

[0110] The molecular carrier 10B in the third embodiment of the present invention has the following beneficial effects: First, since the carbon nanotube composite structure 110 is arranged on the top surface of the patterned protrusion 122, the carbon nanotube composite structure 110 and the patterned protrusion 122 respectively form two layers of nanostructures with the same pattern. Moreover, the carbon nanotubes in the carbon nanotube composite structure 110 can increase the unevenness of the top surface of the patterned protrusion 122, thereby further improving the SERS enhancement factor and enhancing Raman scattering. Secondly, since the carbon nanotube composite structure 110 is retained on the top surface of the patterned protrusion 122, the step of removing the carbon nanotube composite structure 110 in the preparation process is reduced, which not only simplifies the process and reduces the cost, but also reduces the pollution to the substrate 12 caused by removing the carbon nanotube composite structure 110.

[0111] In addition, those skilled in the art may also make other changes within the spirit of the present invention, and these changes made according to the spirit of the present invention should be included in the scope of protection required by the present invention.

Claims

1. A molecular carrier for single molecule detection, comprising a substrate and a metal layer disposed on the surface of the substrate; characterized in that: The substrate comprises a base and a plurality of patterned protrusions arranged on the surface of the base, wherein the patterned protrusions comprise a plurality of protrusions arranged crosswise to form a mesh structure, thereby defining a plurality of holes; and the metal layer is arranged on the surface of the patterned protrusions.

2. The molecular carrier according to claim 1, characterized in that The plurality of convex strips include a plurality of first convex strips extending along a first direction and a plurality of second convex strips extending along a second direction, and an angle between the first direction and the second direction is greater than or equal to 30 degrees and less than or equal to 90 degrees.

3. The molecular carrier according to claim 2, characterized in that The width of the convex strip is 20 nanometers to 150 nanometers, the height is 50 nanometers to 1000 nanometers, and the spacing between two adjacent parallel convex strips is 10 nanometers to 300 nanometers.

4. The molecular carrier according to claim 3, characterized in that The width of the convex strip is 20 nanometers to 50 nanometers, the height is 500 nanometers to 1000 nanometers, and the spacing between two adjacent parallel convex strips is 10 nanometers to 50 nanometers.

5. The molecular carrier according to claim 1, characterized in that The metal layer is a continuous layered structure and is arranged on the surfaces of the plurality of convex strips and in the holes between the convex strips.

6. The molecular carrier according to claim 1, characterized in that The metal layer is a discontinuous layered structure and is only arranged on the side walls of the convex strips and the substrate surface between adjacent convex strips.

7. The molecular carrier according to claim 1, characterized in that The material of the metal layer is one or more of gold, silver, platinum, copper, iron and aluminum.

8. The molecular carrier according to claim 1, characterized in that The invention further comprises a carbon nanotube composite structure disposed between the top surface of the patterned protrusion and the metal layer, and the pattern of the carbon nanotube composite structure is the same as that of the patterned protrusion.

9. The molecular carrier according to claim 8, characterized in that The carbon nanotube composite structure includes a carbon nanotube structure and a prefabricated layer covering the surface of the carbon nanotube structure, and the carbon nanotube structure includes a plurality of cross-arranged carbon nanotubes.

10. The molecular carrier according to claim 9, characterized in that The carbon nanotube structure includes two stacked and cross-arranged carbon nanotube films, the carbon nanotubes in the carbon nanotube films are connected end to end by van der Waals forces and are arranged in the same direction; the material of the prefabricated layer is one or more of metals, metal oxides, metal sulfides, non-metallic oxides, non-metallic carbides and non-metallic nitrides.

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