CN111913008A - Method for distinguishing gas, liquid and solid nano-substances in liquid phase - Google Patents
Method for distinguishing gas, liquid and solid nano-substances in liquid phase Download PDFInfo
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- CN111913008A CN111913008A CN202010611669.XA CN202010611669A CN111913008A CN 111913008 A CN111913008 A CN 111913008A CN 202010611669 A CN202010611669 A CN 202010611669A CN 111913008 A CN111913008 A CN 111913008A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
- G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
- G01Q60/24—AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
- G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
- G01Q60/24—AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes
- G01Q60/36—DC mode
- G01Q60/363—Contact-mode AFM
Abstract
The invention discloses a method for distinguishing gas, liquid and solid nano-materials in a liquid phase, which comprises the steps of preparing a standard detection object, determining distinguishable force, obtaining a standard force curve, distinguishing a sample to be detected and the like. The method provided by the invention utilizes different responses of the nano-material under mechanical loading to discriminate the nano-material, thereby obviously improving discrimination efficiency, greatly saving time and avoiding damage to the nano-material.
Description
Technical Field
The invention relates to a substance identification method, in particular to a method for identifying gas, liquid and solid nano substances in a liquid phase.
Background
Nanobubbles have a number of potential applications including microfluidic drag reduction, surface cleaning, and prevention of protein and microbial adsorption. Currently, the mainstream method for producing nanobubbles is by alcohol-water substitution. However, the replacement of the two solutions is very easy to dope macromolecular liquid drops and solid particle pollutants, and the pollutants show similar characteristics to nano bubbles under the conventional micro-nano material characterization method, so that the identification of the nano bubbles is very difficult. Therefore, the effective separation of gas, liquid and solid micro-nano substances under the liquid phase is necessary to promote the large-scale industrial application of the nano bubbles. Because the gas-liquid-solid three-phase contact line shows different dynamic phenomena when passing through the surface nano bubbles, the polymer nano liquid drops and the solid microsphere particles, a total internal reflection fluorescence microscope is generally used for observation and characterization in the prior art, but the method can also destroy bubbles while identifying the bubbles. How to rapidly and efficiently identify nano bubbles from nano substances without destroying the bubbles becomes a difficult problem to be solved urgently.
Disclosure of Invention
Aiming at the prior art, the invention provides a method for distinguishing gas, liquid and solid nano-materials in a liquid phase, which aims to solve the problem that the micro-nano-materials are difficult to distinguish.
In order to achieve the purpose, the invention adopts the technical scheme that: the method for distinguishing the gas, liquid and solid nano-materials in the liquid phase comprises the following steps:
(1) preparation of standard assay: preparing standard nano bubbles, standard polydimethylsiloxane nano liquid drops and standard polystyrene solid microsphere solution; performing plasma hydrophilic treatment on the probe, calibrating the deflection coefficient of the cantilever beam and calibrating the elastic coefficient of the probe; ramp is used for calibrating the deflection sensitivity of the cantilever beam, and a thermal noise method is used for the elastic coefficient;
(2) determination of resolvable force: under the peak force quantitative nanometer measurement mode of an atomic force microscope, a group of forces with gradient changes are adopted to respectively image the prepared standard nanometer bubbles, standard nanometer liquid drops and standard solid microsphere solution, and the corresponding forces when the three substances show obviously different mechanical responses are taken as the minimum detection force capable of distinguishing the nanometer substances;
(3) obtaining a standard force curve: respectively obtaining standard force curves of standard nano bubbles, standard nano droplets and standard solid microsphere solutions in a force array mode of an atomic force microscope, and determining the forms of the standard force curves of the three substances;
(4) distinguishing samples to be detected: and (3) imaging the sample to be detected by adopting the distinguishable force determined in the step (2), acquiring a force curve of the sample to be detected by adopting the same method as the step (3), and comparing the image and the force curve of the sample to be detected with the image and the standard force curve of the standard detection object obtained under the minimum detection force capable of distinguishing the nano-substance to determine the substance type of the sample to be detected.
The invention provides two simple mechanical discrimination methods based on an atomic force microscope quantitative mechanical nano-measurement mode, namely the response of nano-materials to loading force and the intrinsic force curve of the nano-materials, and can rapidly and efficiently discriminate and distinguish the micro-nano-materials. For different loading forces, when the nano-substances in different states use the same force gradient, the morphological profiles of the nano-substances show different changes, namely PF-QNM imaging is carried out on different substances, and the three substances show different mechanical responses under the minimum detection force (enabling the nano-substances in different states to show obviously different forces) for distinguishing the nano-substances. For example, the contact angle of the nanobubble under the action of large loading force is close to 0, no recognizable height exists on the height map, the obvious contact line shrinkage can be observed in the nanobubble, and an extremely thin molecular layer appears at the edge of the nanobubble, so that the nanobubble is in a shape of a wide-edge cap. Meanwhile, the appearance of the solid microsphere can not be obviously changed.
In addition, the force curves for different nanospecies show different characteristics. The nano bubble force-distance relation shows good linear change, and the linear change sections of the loading/unloading force curves are completely overlapped; the force curve of the nano liquid drop shows staged linear change, a plurality of jumping points can be observed on the curve, and the loading/unloading force curves are not coincident, namely hysteresis appears; the force curve of the solid microspheroidal particle is characterized by typical hard materials, the force rises sharply with the distance change, and the loading/unloading force curves are completely coincident.
Based on the principle, the invention firstly obtains a standard force response curve on the basis of standard nano bubbles, polydimethylsiloxane nano liquid drops and polystyrene solid microspheres, and compares the force response curve result and the force response curve result of the sample to be detected with the standard force response curve as a judgment standard, so that the nano substance of which the sample to be detected belongs to can be quickly judged. The method has high distinguishing efficiency, does not damage the nano-material, and greatly improves the distinguishing efficiency and the distinguishing effect. On the basis of the technical scheme, the invention can be further improved as follows.
Further, the preparation of the standard nanobubbles comprises the following steps: freezing pure water at 4 deg.C for at least 48h to make the air content in water as close to the saturated concentration of air at 4 deg.C as possible; then placing the Highly Oriented Pyrolytic Graphite (HOPG) which is just torn off on a heating table at 65 ℃ and heating for at least 5 min; then rapidly dropwise adding the frozen pure water to the surface of the heated highly-oriented pyrolytic graphite, so that the air in the water instantly reaches an oversaturated state at an interface, and the air is separated out to obtain standard nano bubbles; the dropping amount of pure water was about 20. mu.L.
Further, the standard nano-droplets in the invention are formed by adopting a 'dip pen' technology, namely, a small amount of Polydimethylsiloxane (PDMS) droplets are absorbed by a micro-syringe with the diameter of 0.72 mm and the capacity of 0.2 mu L, and are dripped on the surface of newly-torn highly-oriented pyrolytic graphite for multiple times (5-10 times) of dipping, so that polydimethylsiloxane droplets with different micro-nano sizes are finally obtained.
Further, the standard solid microsphere solution in the invention is a polystyrene microsphere particle suspension, and the preparation method comprises the following steps: a suspension of commercially available polystyrene microspheroidal particles (concentration 7.85X 10) having a diameter of 1.0 μm was prepared-1vol%) and pure water at a volume ratio of 1:999 to obtain a standard solid microsphere solution with a concentration of 7.85X 10-4vol％。
Further, a force curve of a local position can be obtained simultaneously using a fixed Point force curve acquisition method (Point and shot).
The invention has the beneficial effects that: the method provided by the invention utilizes the response of the nano-material under the mechanical condition to discriminate the nano-material, thereby obviously improving the discrimination efficiency, greatly saving the time and avoiding damaging the nano-material.
Drawings
FIG. 1 is a graph of force response of a standard nano-material obtained by varying the loading force; wherein, fig. 1(a) is the force response morphology of a standard nanobubble, fig. 1(b) is the force response morphology of a standard nanodroplet, and fig. 1(c) is the force response morphology of a standard nanosphere solution;
FIG. 2 is a two-dimensional cross-sectional profile of a standard nanobubble obtained by varying the loading force;
FIG. 3 is a two-dimensional cross-sectional profile of a standard nano-droplet obtained by varying the loading force;
FIG. 4 is a two-dimensional cross-sectional profile of a standard solid microsphere solution obtained by varying the loading force;
FIG. 5 is a force-distance curve of a standard nanobubble taken in force array mode;
FIG. 6 is a force-distance curve of a standard nano-droplet acquired in force array mode;
FIG. 7 is a force-distance curve of a standard solid microsphere solution taken in a force array mode;
FIG. 8 is a force-distance curve for sample number 1;
fig. 9 is a force-distance curve for test sample No. 2.
Detailed Description
The following examples are provided to illustrate specific embodiments of the present invention.
Example one
A method for distinguishing gas, liquid and solid nano-substances in a liquid phase comprises the following steps:
(1) preparation of standard assay:
freezing pure water at 4 deg.C for at least 48h to make the air content in water as close to the saturated concentration of air at 4 deg.C as possible; then placing the high-orientation pyrolytic graphite which is just torn on a heating table at 65 ℃ and heating for 5 min; then rapidly dropwise adding the frozen pure water to the surface of the heated highly-oriented pyrolytic graphite, so that the air in the water instantly reaches an oversaturated state at an interface, and the air is separated out to obtain standard nano bubbles; the dropping amount of pure water was about 20. mu.L.
And (3) sucking a small amount of polydimethylsiloxane nano-droplets by using a micro-syringe with the diameter of 0.72 mm and the capacity of 0.2 mu L, dropwise adding the polydimethylsiloxane nano-droplets on the surface of the newly-torn high-sequence pyrolytic graphite, and dipping for 6 times to finally obtain the polydimethylsiloxane nano-droplets, namely the standard nano-droplets.
A suspension of commercially available polystyrene microspheroidal particles (concentration 7.85X 10) having a diameter of 1.0 μm was prepared-1vol%) and pure water at a volume ratio of 1:999 to obtain a concentration of 7.85X 10-4vol% standard solid microsphere solution.
(2) Determination of resolvable force: under the peak force quantitative nanometer measurement mode of an atomic force microscope, the prepared standard nanometer bubbles, standard nanometer liquid drops and standard solid microsphere solution are imaged by using loading forces of 0.3nN, 1.5nN, 3.0nN and 5.0nN respectively, and the corresponding forces when the three substances show obviously different force responses are taken as the minimum detection force for distinguishing the nanometer substances; the imaging results are shown in fig. 1 to 4, wherein fig. 1(a) is the force response morphology of a standard nanobubble, fig. 1(b) is the force response morphology of a standard nanodroplet, and fig. 1(c) is the force response morphology of a standard solid microsphere solution; fig. 2 is a two-dimensional cross-sectional profile of a standard nanobubble obtained by changing a loading force, fig. 3 is a two-dimensional cross-sectional profile of a standard nanodrop obtained by changing a loading force, and fig. 4 is a two-dimensional cross-sectional profile of a standard solid microsphere solution obtained by changing a loading force. As can be seen from the graph, the contact angle of the nanobubbles approaches 0 with a loading force of 5nN, with no apparent contact line on the height map; when the force applied on the polydimethylsiloxane nano-droplet is 5nN, the obvious contact line shrinkage can be observed, and an extremely thin molecular layer appears at the edge of the droplet; the morphology of the polystyrene microparticles is not obviously changed when a force of 5nN is applied. Thus, the resolvable force was determined to be 5 nN.
(3) Obtaining a standard force curve: under the force array mode of an atomic force microscope, standard force curves of a standard nano bubble, a standard nano liquid drop and a standard solid microsphere solution are respectively obtained, the forms of the standard force curves of the three substances are determined, and the results are shown in fig. 5-7. As can be seen from the figure, the standard nano bubbles show good linear change, and the linear change sections of the loading/unloading force curves are obviously overlapped; the force curve of the polydimethylsiloxane nano-droplet shows similar linear change on the whole, but the loading/unloading force curve is discontinuous, and a force jump point can be observed on the force curve; the force curve of the solid microspheroidal particle is characterized by typical hard materials, the force rises sharply with the distance change, and the loading/unloading force curves are completely coincident.
(4) Distinguishing samples to be detected: and (3) imaging the No. 1 sample to be tested by adopting the distinguishable force determined in the step (2), and drawing a force curve of the No. 1 sample to be tested by adopting the same method as the step (3), wherein the force curve of the No. 1 sample to be tested is shown in a figure 8 and shows good linear change, and linear change sections of the force adding/unloading curves are obviously overlapped. And comparing the image and the force curve of the No. 1 sample to be detected with the image and the standard force curve of the standard detection object obtained under the distinguishable force, and determining that the No. 1 sample to be detected is the nano bubble.
Example two
A method for distinguishing gas-liquid-solid substances under micro-nano scale comprises the following steps:
the steps (1) to (3) are the same as in the first embodiment.
(4) Distinguishing samples to be detected: and (3) imaging the No. 2 sample to be tested by adopting the resolvable force determined in the step (2), and drawing a force curve of the No. 2 sample to be tested by adopting the same method as the step (3), wherein the force curve of the No. 2 sample to be tested is shown in FIG. 9, the whole sample to be tested shows similar linear change, but the loading/unloading force curve is discontinuous, and a force jump point can be observed on the force curve. And comparing the image and the force curve of the No. 2 sample to be detected with the image and the standard force curve of the standard detection object obtained under the distinguishable force, and determining that the No. 2 sample to be detected is the nano bubble.
While the present invention has been described in detail with reference to the embodiments, it should not be construed as limited to the scope of the patent. Various modifications and changes may be made by those skilled in the art without inventive step within the scope of the appended claims.
Claims (5)
1. A method for distinguishing gas, liquid and solid nano-materials in a liquid phase is characterized in that the distinguishing method is carried out based on different mechanical responses of different nano-materials in the liquid phase, and comprises the following steps:
(1) preparation of standard assay: preparing standard nano bubbles, standard polydimethylsiloxane nano liquid drops and standard polystyrene solid microsphere solution; performing plasma hydrophilic treatment on the probe, calibrating the deflection coefficient of the cantilever beam and calibrating the elastic coefficient of the probe;
(2) determination of resolvable force: under the peak force quantitative nanometer measurement mode of an atomic force microscope, a group of forces with gradient changes are adopted to respectively image the prepared standard nanometer bubbles, standard nanometer liquid drops and standard solid microsphere solution, and the corresponding forces when the three substances show obviously different mechanical responses are taken as the minimum detection force capable of distinguishing the nanometer substances;
(3) obtaining a standard force curve: respectively obtaining standard force curves of standard nano bubbles, standard nano droplets and standard solid microsphere solutions in a force array mode of an atomic force microscope, and determining the forms of the standard force curves of the three substances;
(4) distinguishing samples to be detected: and (3) imaging the sample to be detected by adopting the distinguishable force determined in the step (2), acquiring a force curve of the sample to be detected by adopting the same method as the step (3), and comparing the image and the force curve of the sample to be detected with the image and the standard force curve of the standard detection object obtained under the minimum detection force capable of distinguishing the nano-substance to determine the substance type of the sample to be detected.
2. The method for distinguishing gas, liquid and solid nano-materials under the liquid phase according to claim 1, wherein the preparation of the standard nanobubbles comprises the following steps:
SS 1: freezing pure water at 4 ℃ for 48-55 h;
SS 2: heating the high-orientation pyrolytic graphite at 65 ℃ for 5-10 min;
SS 3: and dropwise adding the pure water treated by SS1 to the surface of the heated highly-oriented pyrolytic graphite, and separating out air to obtain standard nano bubbles.
3. The method for distinguishing gas, liquid and solid nano-materials under the liquid phase according to claim 1, wherein the standard nano-droplets are polydimethylsiloxane droplets, and are prepared by the following steps: and dripping polydimethylsiloxane liquid drops on the surface of the highly oriented pyrolytic graphite, and dipping for 5-10 times to obtain standard nano liquid drops.
4. The method for distinguishing gas, liquid and solid nano-materials under the liquid phase according to claim 1, wherein: the set of forces with gradient changes in step (2) were 0.3nN, 1.5nN, 3.0nN and 5.0 nN.
5. The method for distinguishing gas, liquid and solid nano-materials under the liquid phase according to claim 1, wherein: the resolvable force determined in step (2) was 5.0 nN.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2020079020A1 (en) * | 2018-10-15 | 2020-04-23 | University College Dublin, National University Of Ireland, Dublin | A system, method and generator for generating nanobubbles or nanodroplets |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2020079020A1 (en) * | 2018-10-15 | 2020-04-23 | University College Dublin, National University Of Ireland, Dublin | A system, method and generator for generating nanobubbles or nanodroplets |
Non-Patent Citations (3)
| Title |
|---|
| CHON U. CHAN 等: "Collapse of Surface Nanobubbles", 《PHYSICAL REVIEW LETTERS》 * |
| HONGJIE AN 等: "Distinguishing nanobubbles from nanodroplets with AFM: the influence of vertical and lateral imaging forces", 《LANGMUIR》 * |
| YOUQUAN JIA 等: "Identification of surface nanobubbles and resolving their", 《PHYSICS, MECHANICS & ASTRONOMY》 * |
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