Method for optically controlling photocatalytic particles and application thereof

Abstract

The invention provides a method for optically controlling photocatalytic particles, which comprises the following steps of: constructing a cavity, adding a mixed solution of fuel liquid and photocatalytic particles into the cavity, and then placing the cavity into an optical microscopic device with a radially adjustable collecting lens; the optical microscopic device emits ultraviolet light, the ultraviolet light passes through the collecting lens system to form radially symmetrical biconical light beams, and by adjusting the height of a collecting lens, the light beams at the beam waist, before the beam waist or after the beam waist irradiate the sample table to respectively form vertical, convergent and divergent light spots; light spots irradiate the photocatalytic particles, and due to the neutral diffusion phoresis effect, convergence or divergence motion control of the photocatalytic particles can be achieved. According to the technical scheme, based on the photosensitive property of the photocatalytic particles, directional transportation of the photocatalytic particles is achieved by means of the convergence or divergence property of light spots; and the transportation speed and direction can be regulated and controlled through the parameters of the light spots. The device is simple in structure, convenient to operate, low in cost and good in controllability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of intelligent control, and particularly relates to a method for optically controlling photocatalytic particles and application thereof. BACKGROUND

[0002] At the microscale, the precise capture, transport and dynamic assembly of colloidal particles can be used in the fields of targeted drug delivery, microfluidic chip integration or functional material construction. The current mainstream particle manipulation methods include optical tweezers, photoelectric tweezers and acoustic tweezers. The high-intensity laser used in the optical tweezers equipment is easy to cause thermal damage to the sample. The photoelectric tweezers equipment requires a special light guide substrate to construct a sandwich structure, and the manufacturing process is complex and difficult to integrate. The acoustic tweezers equipment requires a precise acoustic design to generate a stable acoustic field, and the control system is complex and costly. SUMMARY

[0003] In view of the above problems, the application discloses a method for optically controlling photocatalytic particles, which realizes the movement control of the photocatalytic particles by adjusting the height of the condenser in the radial direction.

[0004] To this end, the technical scheme adopted by the application is as follows:

[0005] A method for optically controlling photocatalytic particles, comprising the following steps:

[0006] A cavity is constructed, a mixed solution of fuel liquid and photocatalytic particles is added to the cavity, and then the cavity is placed in a condenser radially adjustable optical microscope device. The optical microscope device emits ultraviolet light, forms a radially symmetric biconical light beam through a condenser system, adjusts the height of the condenser, respectively makes the light beam at the beam waist, before the beam waist or after the beam waist irradiate the sample stage, respectively forms a vertical, converging or diverging light spot, and the light spot irradiates the photocatalytic particles. Due to the neutral diffusion phoresis effect, the movement control of the photocatalytic particles can be realized. The photocatalytic particles are isotropic anatase TiO2 microspheres.

[0007] When the TiO2 microspheres are irradiated by ultraviolet light, photo-generated electrons and holes are generated in the irradiated area, and H2O2 is catalytically decomposed into H2O and O2 molecules. Since the catalytic reaction only occurs in the irradiated area, and the light penetration depth is limited, O2 molecules accumulate on the light-receiving side of the TiO2 microspheres, forming a high-O2-concentration area, and the back light side is a low-O2-concentration area, thereby generating an O2 concentration gradient in the TiO2 microspheres. The asymmetric collision of O2 molecules drives the TiO2 microspheres to move to the low-O2-concentration area. Adjusting the height of the condenser, when the TiO2 microspheres are irradiated at the waist of the light beam, the light beam propagation direction is perpendicular to the sample stage downward, and the particles show mutual repulsion due to photocatalytic repulsive force; when the TiO2 microspheres are irradiated at the front of the waist of the light beam, the light beam propagation direction is centripetal to the center axis of the field of view, showing convergence, the centrifugal side of the TiO2 microspheres is light-receiving, and the centrifugal side O2 concentration is higher than the centripetal side, so the TiO2 microspheres migrate centripetally, showing positive phototaxis; when the TiO2 microspheres are irradiated at the back of the waist of the light beam, the light beam propagation direction is centrifugal away from the center axis of the field of view, showing divergence, the centripetal side of the TiO2 microspheres is light-receiving, and the centripetal side O2 concentration is higher than the centrifugal side, so the TiO2 microspheres migrate centrifugally, showing negative phototaxis.

[0008] A further technical scheme of the present application is: further comprising controlling the transport rate and direction of the photocatalytic particles by controlling the light spot parameters.

[0009] A further technical scheme of the present application is: the light spot parameters include light intensity and condenser height.

[0010] A further technical scheme of the present application is: the photocatalytic particles are isotropic anatase TiO2 microsphere particles.

[0011] A further technical scheme of the present application is: the fuel liquid is an H2O2 solution with a concentration of 0.1wt.%-5wt.%.

[0012] A further technical scheme of the present application is: the cavity includes a cover glass, a glass slide and a gasket, the gasket is located between the cover glass and the glass slide, a cavity is provided at the center of the gasket, and the cavity contains a mixture of fuel liquid and photocatalytic particles.

[0013] A further technical solution of the present application is that the optical microscopic device comprises four parts of an illumination system, a condenser lens system, a sample stage, a microscopic imaging and camera system; the sample stage is used for carrying a component to be operated, and the cavity is placed on the sample stage; the illumination system comprises a light source and a first reflector, is located above the sample stage, and is used for outputting ultraviolet collimated light; the condenser lens system comprises a mechanical adjusting structure and a condenser lens, is located below the illumination system and above the sample stage, and is used for controlling radial illumination of the observed sample; the microscopic imaging and camera system comprises an objective lens, a sleeve lens, a second reflector and a CMOS camera, is located below the sample stage, and is used for imaging observation of the observed sample; the collimated light beam is emitted by the illumination light source, is reflected by the first reflector, enters the condenser lens to form a radially symmetric biconical light beam, and is imaged in the CMOS camera after the sample stage, the objective lens, the sleeve lens and the second reflector.

[0014] A further technical solution of the present application is that in the illumination system, the light source is an LED collimated light source, the intensity distribution on the cross section of the light beam is approximately a two-dimensional Gaussian distribution, and the light source is a collimated light beam with a central wavelength less than 380 nm.

[0015] A further technical solution of the present application is that in the condenser lens system, the mechanical adjusting structure supports manual control movement of the condenser lens along the optical axis direction, and the condenser lens can make the light beam irradiate the sample stage at the beam waist, before the beam waist or after the beam waist by adjusting the height of the condenser lens.

[0016] A further solution of the present application is that the sample is sensitive to ultraviolet light and the transmission angle of the light beam; when the beam waist of the light beam is below the sample stage, the photocatalytic particles will gradually gather around the light beam; when the beam waist of the light beam is above the sample stage, the photocatalytic particles will gradually move away from the light beam; and the movement state of the sample can be indirectly controlled by manually adjusting the position of the condenser lens.

[0017] The present application also discloses the application of the method for optically manipulating photocatalytic particles as described above, which is used for manipulating the enrichment or dispersion of photocatalytic particles, thereby enhancing or weakening the detection signal; or is used for assembling and disassembling colloids to obtain functional materials with different optical and mechanical properties.

[0018] The present application also discloses a method for group migration of photocatalytic particles, which adopts the method for optically manipulating photocatalytic particles according to any one of the above solutions, and realizes directional migration of photocatalytic particles by moving the light spot or the sample stage.

[0019] The present application also discloses a method for sorting or mixing photocatalytic particles, which adopts the method for optically manipulating photocatalytic particles according to any one of the above solutions, and realizes sorting or mixing of particles by enriching or dispersing photocatalytic particles from a mixed system of photocatalytic particles and inert particles.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] Firstly, the technical scheme of the present application, based on the photosensitive properties of photocatalytic particles, changes the converging / diverging properties of the light spot by radially adjusting the condenser, realizes the directional transport of photocatalytic particles such as TiO2, and can control the transport rate and direction by changing the parameters of the light spot, realizing the convergence, divergence and migration of photocatalytic particle clusters.

[0022] Secondly, the technical scheme of the present application can realize the manipulation and transport of single particles or groups; in principle, multiple transport tasks can be performed on particles at any position in the system at the same time.

[0023] Thirdly, the technical scheme of the present application avoids the thermal damage caused by high-intensity laser required by optical tweezers technology, does not require a specially designed experimental cavity or substrate, and does not require a precisely designed device. It only needs to add a mixture of fuel liquid and photocatalytic particles in the cavity, combined with the radially adjustable optical microscope of the condenser, to realize the transport of particles. The device structure is simple, easy to operate, low in cost, good in controllability, and green and environmentally friendly.

[0024] Fourthly, the technical scheme of the present application has wide application prospects in many fields such as biomedical science, material science and environmental science, for example, it can assist in biological detection to enhance or weaken the detection signal, and can also be used to manufacture microfluidic devices to realize the assembly and disassembly of colloids. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a schematic diagram of an experimental cavity of an embodiment of the present application;

[0026] Figure 2 is a schematic diagram of a radially adjustable optical microscope of a condenser of an embodiment of the present application;

[0027] Figure 3 is a schematic diagram of neutral diffusiophoresis of TiO2 microspheres of an embodiment of the present application;

[0028] Figure 4 is a schematic diagram of the influence of the relative position of the beam waist of the light beam and the sample stage on the transport direction of TiO2 microspheres of an embodiment of the present application;

[0029] Figure 5 is simulation data of the intensity distribution of the light beam along the transmission direction of the light beam when the light beam passes through the sample of an embodiment of the present application, and the data is normalized;

[0030] Figure 6 is simulation data of the intensity distribution of the beam waist of the light beam at the sample of an embodiment of the present application, and the data is normalized;

[0031] Figure 7 These are simulated intensity distribution data at distances of +5mm and -5mm from the beam waist in this embodiment of the invention, and the data have been normalized.

[0032] Figure 8 These are photographs of the transport path of TiO2 microspheres under the converged light spot in an embodiment of the present invention, as well as diagrams showing the real-time changes in the formation of TiO2 microsphere clusters at different times;

[0033] Figure 9 These are photographs of the transport path of TiO2 microspheres under the divergent light spot in an embodiment of the present invention, and diagrams showing the real-time changes in the disintegration of TiO2 microsphere clusters at different times.

[0034] Figure 10 This is data on the variation of transport rate with the height of the condenser lens in an embodiment of the present invention;

[0035] Figure 11 This is data on the variation of transport rate with ultraviolet light intensity in an embodiment of the present invention;

[0036] Figure 12 These are before-and-after comparison photos of TiO2 microsphere clusters migrating as a whole with the converged light spot under an embodiment of the present invention;

[0037] Figure 13 These are before-and-after comparison photos of TiO2 microspheres and inert fluorescent PS microspheres being sorted under a converging light spot according to an embodiment of the present invention. Attached image description:

[0039] 1-Glass slide, 2-Annular silicone gasket, 3-Experimental chamber;

[0040] 4-Illumination source, 5-First reflecting mirror, 6-Condenser adjustment frame, 7-Condenser, 8-Sample stage, 9-Objective lens, 10-Sleeve lens, 11-Second reflecting mirror, 12-CMOS. Detailed Implementation

[0041] The preferred embodiments of the present invention will be described in further detail below.

[0042] Example 1:

[0043] The experimental chamber in this embodiment is as follows: Figure 1 As shown, a 22mm × 22mm glass slide 1 was sequentially cleaned with isopropanol, anhydrous ethanol, and deionized water until the surface was clean. Then, a hollow annular silicone gasket 2 was adhered to the glass slide 1 to form an experimental cavity 3 with a diameter of 5mm and a height of 0.2mm, ensuring a tight fit. H2O2 solution (0.1wt.%-5wt.%) and a suspension of photocatalytic particles (TiO2 microspheres in this example) were added to the experimental cavity 3. Finally, a glass slide was placed over the experimental cavity 3 for sealing.

[0044] The prepared experimental cavity 3 is transferred to the sample stage of the optical microscope apparatus. The optical microscope apparatus is as follows: Figure 2 As shown, the device includes an illumination source 4, a first reflecting mirror 5, a condenser adjustment frame 6, a condenser lens 7, a sample stage 8, an objective lens 9, a sleeve lens 10, a second reflecting mirror 11, and a CMOS sensor 12. The condenser adjustment frame 6, condenser lens 7, sample stage 8, objective lens 9, and sleeve lens 10 are located on the same axis. In this device, the illumination source 4 is an LED, with an intensity distribution on the beam cross-section that approximates a two-dimensional Gaussian distribution. The center wavelength of the light is 365nm, and the output beam of the illumination source 4 is collimated light with a divergence angle of less than 7°. The output light intensity can be adjusted. The mechanical adjustment structure allows for manual control of the condenser lens 7 along the optical axis, with a control range greater than ±5mm based on the sample location. The condenser lens 7 has a light-transmitting aperture of 30mm and a numerical aperture of 0.55. After passing through the condenser lens 7, the intensity distribution on the beam cross-section approximates a two-dimensional Gaussian distribution, with a beam angle half-angle of approximately 28° and a maximum optical power density of 1460mW / cm² at the beam waist. 2 The ultraviolet light emitted by the illumination source 4 forms a radially symmetrical double-cone beam after passing through the condenser lens 7. By adjusting the height of the condenser lens 7, the beam can be directed to the sample stage 8 at the waist, in front of the waist, or behind the waist, respectively, forming vertical, converging, and diverging light spots. When the light spots illuminate the TiO2 microspheres in the experimental chamber 3, the convergence or divergence of the photocatalytic particles can be controlled due to the neutral diffusion effect.

[0045] This embodiment uses isotropic anatase TiO2 microspheres as an example to illustrate the transport mechanism of photocatalytic particles by converging / diverging light spots. First, it is necessary to explain the neutral diffusion migration that occurs in TiO2 microspheres after ultraviolet light excitation in H2O2 solution. For example... Figure 3 As shown, when TiO2 microspheres are irradiated with ultraviolet light, photogenerated electrons and holes are generated in the illuminated area, catalyzing the decomposition of H2O2 into H2O and O2 molecules. Since the catalytic reaction only occurs in the illuminated area and the light penetration depth is limited, O2 molecules accumulate on the illuminated side of the TiO2 microspheres, forming a high O2 concentration region, while the shaded side has a low O2 concentration region, thus creating an O2 concentration gradient within the TiO2 microspheres. Asymmetric collisions of O2 molecules propel the TiO2 microspheres towards the low O2 concentration region.

[0046] Furthermore, by adjusting the radial height of the condenser lens 7 using the condenser lens adjustment bracket 6, the relative position of the beam waist and the TiO2 microspheres in the experimental cavity 3 changes, thereby producing different effects on the TiO2 microspheres, such as... Figure 4As shown. When the beam waist illuminates the TiO2 microspheres in experimental chamber 3, the beam propagation direction is perpendicular to the sample stage 8 and downwards, and the particles exhibit photocatalytic repulsion, causing them to move away from each other. When the beam waist illuminates the TiO2 microspheres, the beam propagation direction is centripetal, pointing towards the central axis of the field of view, and converges. The centrifugal side of the TiO2 microspheres receives light, and the O2 concentration on the centrifugal side is higher than that on the centrifugal side, thus causing the TiO2 microspheres to migrate centripetally, exhibiting positive phototaxis. When the beam waist illuminates the TiO2 microspheres, the beam propagation direction is centrifugal, away from the central axis of the field of view, and diverges. The centrifugal side of the TiO2 microspheres receives light, and the O2 concentration on the centrifugal side is higher than that on the centrifugal side, thus causing the TiO2 microspheres to migrate centrifugally, exhibiting negative phototaxis.

[0047] Furthermore, when the beam waist illuminates the sample stage 8, i.e. when the beam is perpendicular, the condenser height is defined as 0.00 mm; when the beam in front of the waist illuminates the sample stage 8, i.e. when the beam is converging, it is called a "converging spot", and the condenser height is a negative value; when the beam behind the waist illuminates the sample stage 8, i.e. when the beam is diverging, it is called a "diverging spot", and the condenser height is a positive value.

[0048] Through simulation analysis, the intensity distribution of the light beam along the beam propagation direction when it passes through the sample is as follows: Figure 5 As shown.

[0049] Through simulation analysis, the intensity distribution of the beam waist at the sample is as follows: Figure 6 As shown.

[0050] Based on simulation analysis, the intensity distribution at distances of +5mm and -5mm from the beam waist is as follows: Figure 7 As shown.

[0051] The following experiment demonstrates the centripetal / centrifugal transport of TiO2 microspheres using the aforementioned apparatus and converging / diverging light spots:

[0052] like Figure 8 As shown, TiO2 particles with a diameter of 2.39 ± 0.60 μm are dispersed in the H2O2 solution. With the condenser lens height adjusted to -0.3 mm, the spot diameter is approximately 0.32 mm, and the ultraviolet light intensity is 1102 mW / cm². 2 With an H2O2 concentration of 0.25 wt.%, TiO2 microspheres were observed to converge from the edge of the light spot to the center and gradually form clusters. Figure a) shows the transport trajectory of 14 TiO2 microspheres within 21 s.

[0053] like Figure 9 As shown, clusters of numerous TiO2 particles are distributed at the center of the field of view. With the condenser lens height adjusted to +0.3 mm, the spot diameter is approximately 0.32 mm, and the ultraviolet light intensity is 1102 mW / cm². 2With an H2O2 concentration of 0.25 wt.%, it can be observed that TiO2 microspheres diverge from the center of the light spot to the edge of the light spot, and the clusters gradually disintegrate. Figure a) shows the transport trajectory of 11 TiO2 microspheres within 21 s.

[0054] Furthermore, the transport rate and direction of the photocatalytic particles can be controlled by adjusting the light spot parameters.

[0055] Adjust the height of the condenser lens, gradually increasing it from -0.25mm. At this point, the ultraviolet light intensity is 1460mW / cm². 2 The H2O2 concentration was 2 wt.%, and the results were as follows: Figure 10 As shown, it can be seen that as the absolute value of the condenser lens height increases, i.e. the degree of convergence / divergence deepens, the transport speed of TiO2 microspheres becomes faster.

[0056] Adjust the ultraviolet light intensity to 146 mW / cm 2 The height of the condenser lens was gradually increased, at which point the condenser lens height was 0.2 mm and -0.2 mm, and the H₂O₂ concentration was 1 wt.%. The results obtained were as follows: Figure 11 As shown, it can be seen that with the increase of light intensity, the transport speed of TiO2 microspheres is faster when the light spot is divergent, while the transport speed of TiO2 microspheres first increases and then decreases when the light spot is converged.

[0057] Example 2:

[0058] The difference in this embodiment compared to Example 1 is that the position of the light spot is changed by moving the sample stage. In this embodiment, the condenser lens height is -0.2 mm, and the ultraviolet light intensity is 1460 mW / cm². 2 The H2O2 concentration was 1 wt.%, and the results were as follows: Figure 12 As shown, a cluster of TiO2 microspheres is distributed at the center of the light spot. After the sample stage is moved, the relative position between the center of the light spot and the center of the TiO2 cluster shifts, and the TiO2 microsphere cluster migrates as a whole with the light spot, with an overall migration speed of approximately 18 μm / s.

[0059] Example 3:

[0060] Based on Example 1, this example differs in that a mixture of H2O2 solution, photocatalytic particles, and inert particles is added to experimental chamber 3. The inert particles are 3μm fluorescent PS spheres. In this example, TiO2 and PS microspheres are uniformly dispersed in the H2O2 solution. With a condenser lens height of -0.2mm and an ultraviolet light intensity of 1170mW / cm², the optimal conditions are achieved. 2 The H2O2 concentration was 1 wt.%, and the results were as follows: Figure 13As shown, after 326 seconds, TiO2 microspheres aggregated at the center of the light spot to form a huge cluster, while PS microspheres remained dispersed within the field of view, thus achieving the sorting of different colloidal particles.

[0061] Based on the experimental results of the above embodiments, it can be used to assist in biological detection. For example, this technology can be used to manipulate and enrich or disperse analytes with low concentrations in the sample to be tested, thereby achieving the purpose of enhancing or weakening the detection signal. It can also be used to manufacture a microfluidic device for the assembly and disassembly of colloids to obtain functional materials with different optical and mechanical properties.

[0062] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for optically manipulating photocatalytic particles, characterized in that: Includes the following steps: A cavity is constructed, and a mixture of fuel liquid and photocatalytic particles is added into the cavity. The cavity is then placed in an optical microscope with a radially adjustable condenser lens. The optical microscope emits ultraviolet light, which is formed into a radially symmetrical double-cone beam by the condenser lens system. By adjusting the height of the condenser lens, the beam can be directed to the sample stage at the beam waist, in front of the beam waist, or behind the beam waist, respectively, forming vertical, converging, and diverging light spots. The light spots irradiate the photocatalytic particles, and the convergence or divergence of the photocatalytic particles can be controlled due to the neutral diffusion effect.

2. The method for optically manipulating photocatalytic particles according to claim 1, characterized in that: It also includes controlling the transport rate and direction of the photocatalytic particles by controlling the light spot parameters.

3. The method for optically manipulating photocatalytic particles according to claim 2, characterized in that: The light spot parameters include light intensity and condenser lens height.

4. The method for optically manipulating photocatalytic particles according to claim 1, characterized in that: The photocatalytic particles are isotropic anatase TiO2 microspheres.

5. The method for optically manipulating photocatalytic particles according to claim 1, characterized in that: The fuel liquid is an H2O2 solution with a concentration of 0.1 wt.% to 5 wt.%.

6. The method for optically manipulating photocatalytic particles according to claim 1, characterized in that: The cavity includes a cover glass, a glass slide, and a gasket. The gasket is located between the cover glass and the glass slide. A cavity is provided at the center of the gasket, and the cavity includes a mixture of fuel liquid and photocatalytic particles.

7. The method for optically manipulating photocatalytic particles according to claim 1, characterized in that: The optical microscopy device comprises four parts: an illumination system, a condenser lens system, a sample stage, and a microscopic imaging and camera system. The sample stage carries the component to be operated, and the cavity is placed on the sample stage. The illumination system, including a light source and a first reflecting mirror, is located above the sample stage and outputs collimated ultraviolet light. The condenser lens system, including a mechanical adjustment structure and a condenser lens, is located below the illumination system and above the sample stage and controls the radial illumination of the observed sample. The microscopic imaging and camera system, including an objective lens, a telescopic lens, a second reflecting mirror, and a CMOS camera, is located below the sample stage and is used for imaging and observing the sample. The collimated beam is emitted from the illumination source, reflected by the first reflecting mirror, and enters the condenser lens to form a conical beam. After illuminating the sample stage, the beam passes through the objective lens, the telescopic lens, and the second reflecting mirror before entering the CMOS camera for imaging.

8. The method for optically manipulating photocatalytic particles according to claim 7, characterized in that: In the lighting system, the light source is an LED collimated light source, and the intensity distribution on the beam cross section is approximately a two-dimensional Gaussian distribution, with adjustable output light intensity.

9. The method for optically manipulating photocatalytic particles according to claim 7, characterized in that: In the condenser system, the mechanical adjustment structure supports manual control of the condenser's movement along the optical axis. The condenser can be adjusted in height to allow the beam to illuminate the sample stage at the waist, before, or after the beam waist.

10. The application of the method for optically manipulating photocatalytic particles as described in any one of claims 1-9, characterized in that: It can be used to control the enrichment or dispersion of photocatalytic particles, thereby enhancing or weakening the detection signal; or to assemble and disassemble colloids to obtain functional materials with different optical and mechanical properties; or to control the directional migration of photocatalytic particles; or to enrich or disperse photocatalytic particles from a mixed system of photocatalytic particles and inert particles, thereby achieving particle sorting or mixing.

Images