CN107340239B - Optical fluid chip light field polarization distribution detection method based on gold nanorod colloid - Google Patents

Optical fluid chip light field polarization distribution detection method based on gold nanorod colloid Download PDF

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CN107340239B
CN107340239B CN201710519525.XA CN201710519525A CN107340239B CN 107340239 B CN107340239 B CN 107340239B CN 201710519525 A CN201710519525 A CN 201710519525A CN 107340239 B CN107340239 B CN 107340239B
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laser
polarization
polarization direction
gold
light
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CN107340239A (en
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阚雪芬
殷澄
许田
韩庆邦
姜学平
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Changzhou Campus of Hohai University
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Changzhou Campus of Hohai University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/06—Illumination; Optics
    • G01N2201/061—Sources
    • G01N2201/06113—Coherent sources; lasers

Abstract

The invention discloses a method for detecting optical fluid chip light field polarization distribution based on gold nanorod colloid, which is characterized by comprising the following steps: 1) preparing gold colloid and gold nanorods, preparing an optical fluid chip, and building a test platform; 2) selecting proper laser wavelength, incident angle and polarization mode, and selecting laser as a light source; laser beams output from a laser are incident on a sample, and the working wavelength of the laser is selected in the range of visible light and infrared light; 3) fixing the white light polarization, and changing the laser polarization direction for capturing the nanorods, namely changing the included angle between the laser polarization direction and the white light polarization direction; 4) keeping the laser direction unchanged, waiting for the solution to evaporate, opening the photo-fluidic chip, and measuring the SEM image. The invention achieves the following beneficial effects: the invention is suitable for detecting the polarization characteristic of the optical fluid chip, has the advantages of small instrument, simple operation, simple design, convenient operation, obvious phenomenon, less time consumption and strong verification, and can realize accurate measurement.

Description

Optical fluid chip light field polarization distribution detection method based on gold nanorod colloid
Technical Field
The invention relates to a method for detecting optical field polarization distribution of an optical fluid chip based on gold nanorod colloids, and belongs to the technical field of optical fluid and nanoscale detection.
Background
With the continuous intersection and fusion of the subjects of nanotechnology, micromachining technology, life science and the like, optical fluids and chip technology taking the optical fluids as cores are increasingly and widely valued and applied.
Optofluidic technology is understood to mean the combination of light and fluid on a micro-scale, using light to monitor the properties of fluids and using fluids to control the tunability of photonic instruments. For specific applications such as surface raman enhanced detection, the use of microfluidics can significantly reduce the sample volume and improve the accuracy and sensitivity of the detection.
The optical fluid technology can be used for capturing, rotating, assembling, moving metal nano particles, biological cells, protein macromolecules, DNA long chains, microfluidic pumps and the like, and has irreplaceable effects in the aspects of pharmacological research, cell surgery, control of nano robots and the like. The optical fluid chip can solidify a specific function and integrate the specific function on a certain microchip, so that the stability is improved, and the optical fluid chip is very important for further popularization of the technology. The polarization properties of light are very important parameters for all chip designs, and in the case of micro-motors in microfluidics, when a micro-or even nano-scale propeller is trapped by a laser beam using the Optical tweezers (Optical tweezer) effect, the rotation is manipulated by changing the polarization of the laser. Namely, the micro propeller is fixed by using the optical tweezers effect, and then the propeller is rotated by using the polarization direction of the rotating laser so as to drive the flow of the surrounding fluid. Therefore, the polarization properties of light are important in optofluidic chips. On the other hand, however, the optical fluid chip is not like an optical waveguide structure with precise design, and its design is limited by many aspects of processing technology, microfluidics technology, etc., thereby making its structure complicated and diversified. For such a situation, it is impossible to analyze the distribution of the light field and even the polarization characteristic, but analyzing the polarization characteristic of the light field by means of numerical analysis by using a model building method is also very complicated and even impossible.
Disclosure of Invention
In order to solve the defects of the prior art, the invention aims to provide a method for detecting the optical fluid chip optical field polarization distribution based on gold nanorod colloids, so that the method is suitable for detecting the optical fluid chip polarization characteristics, the instrument is miniaturized, the operation is simple and convenient, and the accurate measurement can be realized.
In order to achieve the above object, the present invention adopts the following technical solutions:
a method for detecting optical fluid chip optical field polarization distribution based on gold nanorod colloid is characterized by comprising the following steps:
1) preparing gold gel and gold nanorods, preparing an optical fluid chip, and building a test platform.
2) Selecting proper laser wavelength, incident angle and polarization mode, and selecting laser as a light source; laser beams output from a laser are incident on a sample, and the working wavelength of the laser is selected in the range of visible light and infrared light;
3) fixing the white light polarization, and changing the laser polarization direction for capturing the nanorods, namely changing the included angle between the laser polarization direction and the white light polarization direction;
4) keeping the laser direction unchanged, waiting for the solution to evaporate, opening the photo-fluidic chip, and measuring the SEM image.
Further, the gold nanorods in the step 1) have an average length of 40nm,
further, the laser wavelength selected in the step 2) is 830 nm.
Further, the laser power selected in step 2) is between 50 and 100 mW.
Further, the polarization mode in the step 2) can be selected according to the measurement requirement.
Further, the operating wavelength of the laser in the step 2) is selected in the visible light and infrared light range.
The invention achieves the following beneficial effects: the invention is suitable for detecting the polarization characteristic of the optical fluid chip, has the advantages of small instrument, simple operation, simple design, convenient operation, obvious phenomenon, less time consumption and strong verification, and can realize accurate measurement.
Drawings
FIG. 1 is a schematic view of the apparatus of the present invention;
FIG. 2 is a schematic of the strength enhancement around nanorods using finite element simulation;
FIG. 3 is a SEM image of prepared gold nanorods.
The meaning of the reference symbols in the figures:
the device comprises a 1-laser, a 2-polaroid, a 3-beam splitter, a 4-photodiode, a 5-reflector, a 6-polarizer, a 7-dark field condenser, an 8-optical fluid chip and a 9-microscope platform.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
The device of the invention comprises a laser, a polaroid, a microscope, a beam splitter, a photodiode, a reflector, an optical fluid chip and a dark field condenser. As shown in fig. 1, where the laser polarization direction can be controlled by a mirror, linearly polarized white light illumination is obtained with a polarizer.
Based on the measuring device, the method realizes the detection of the polarization characteristic of the optical fluid chip by a brand new thought, and comprises the following specific steps:
the first step is as follows: preparing gold gel, wherein the average length of the gold nanorods is about 40nm, preparing an optical fluid chip, and building a test platform.
The second step is that: and selecting proper laser wavelength, incident angle and polarization mode, and selecting laser as a light source. The laser beam output from the laser is incident on the sample and the operating wavelength can be selected in the visible and infrared ranges. The polarization mode can be selected according to the measurement requirements.
In the embodiment, the laser wavelength is selected to be 830nm, the power is between 50 and 100mW, the white light polarization is fixed, and the included angle between the laser polarization direction and the white light polarization direction is changed.
The third step: the polarization of the white light is fixed, and the polarization direction of the laser used for capturing the nanorods is changed, namely, the included angle between the polarization direction of the laser and the polarization direction of the white light is changed (the direction of the reflector is adjusted), so that the polarization direction of the white light is finally parallel to the polarization direction of the laser.
The polarization direction of the trapping light beam is rotated, namely when the included angle is reduced, the light spot in the dark field is brighter and brighter, and the intensity of the scattering peak is correspondingly enhanced. This indicates that the long axis of the nanorods gradually becomes coincident with the white light polarization direction. That is, the nanorods tend to align along the polarization direction of the laser light, thereby minimizing the optical potential.
When the polarization direction of the white light is perpendicular to the polarization direction of the laser, one light spot appears in a dark field; when the polarization direction of the white light is gradually parallel to the polarization direction of the laser, the color of the light spot changes, the spectral line is red-shifted, and the corresponding peak value becomes larger. This indicates that the polarized localized plasmons are parallel to the long axis of the nanorods. While these results indicate that the captured nanorods are parallel to the laser polarization.
When the nanorods are aligned with the polarization direction of the laser, the polarization is strong, which is equivalent to an electric dipole. While the electric dipole is always in the direction of the electric field, i.e. the polarization direction. When the nanorods are aligned with the polarization direction of the laser, the polarization of the nanorod end points is strongest. The longer the wavelength, the more pronounced the polarization of the nanorod end points. As shown in fig. 2.
The fourth step: keeping the laser direction unchanged, waiting for the solution to evaporate, opening the photo-fluidic chip, and measuring the SEM image. The nanorods were found to be aligned with the laser polarization direction.
FIG. 2 is a schematic representation of the strength enhancement around nanorods using finite element simulations. In the figure, the laser wavelengths are 400nm,500nm,600nm and 700nm from a to d, respectively, and the particle length is 50nm and the width is 10 nm. The arrows in the figure indicate the polarization direction of the excitation light field. It can be seen from the figure that the polarization field of the particles is strong when the orientation of the particles is aligned with the polarization direction of the light, and weak when the turning of the particles is perpendicular to the polarization direction. According to the electronic principle, one electric dipole always makes itself consistent with the polarization direction of the electric field in the electric field, so that when the metal rod particles are consistent with the polarization direction, the energy of the whole system is lower, the system is more stable, and the metal rod particles always make the steering of the metal rod particles consistent with the polarization direction of the light field at the position of the metal rod particles.
The longer the wavelength, the more obvious the polarization of the corresponding nanorod end points when the nanorods are aligned with the laser polarization direction; and when the nanorod is perpendicular to the polarization direction of the laser, the polarization is weak.
FIG. 3 is a SEM measured image of prepared gold nanorods.
The gold nanorod is prepared by the existing method which comprises the following two steps: the first step is mainly to use a small amount of NaBH, a strong reducing agent4Reduction of Au3+Forming Au monocrystal seed crystals with uniform appearance and tiny size; the second step is to add Au3+Adding the single crystal Au seed grown in the first step into the growth solution, and simultaneously utilizing weak reductionThe original agent AA is Au3+Reduction to Au+And then combined with seed crystals, Au+Further reduced on the seed crystal already formed to grow Au particles.
According to the scheme, the mode field condition and the polarization information calculated by original modeling can be converted into observation of the laser polarization and the particle spectrum red shift condition, so that the polarization information in the general optical fluid is obtained, the accuracy of the polarization information is greatly improved, and the acquisition difficulty is greatly reduced.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (6)

1. A method for detecting optical fluid chip optical field polarization distribution based on gold nanorod colloid is characterized by comprising the following steps:
1) preparing gold colloid and gold nanorods, preparing an optical fluid chip, and building a test platform;
2) selecting proper laser wavelength, incident angle and polarization mode, and selecting laser as a light source; a laser beam output from the laser is incident on the sample;
3) fixing white light polarization, changing the laser polarization direction for capturing the nanorods, namely changing an included angle between the laser polarization direction and the white light polarization direction, so that the white light polarization direction is finally parallel to the laser polarization direction, wherein the process of enabling the white light polarization direction to be finally parallel to the laser polarization direction is as follows: rotating the polarization direction of the laser, wherein when the included angle is reduced, the light spot in a dark field is brighter and brighter, the intensity of a scattering peak is correspondingly enhanced, and when the light spot is brightest and the peak value of the scattering peak is maximum, the long axis of the nanorod is superposed with the polarization direction of the white light, namely the nanorod tends to be arranged along the polarization direction of the laser, and the optical potential energy is minimum;
4) keeping the laser direction unchanged, waiting for the solution to evaporate, opening the photo-fluidic chip, and measuring the SEM image.
2. The method for detecting the optical field polarization distribution of the optofluidic chip based on the gold nanorod colloids as claimed in claim 1, wherein the average length of the gold nanorods in step 1) is 40 nm.
3. The method for detecting the optical field polarization distribution of the optical fluid chip based on the gold nanorod colloid according to claim 1, wherein the laser wavelength selected in the step 2) is 830 nm.
4. The method for detecting the optical field polarization distribution of the optofluidic chip based on the gold nanorod colloids as claimed in claim 1, wherein the laser power selected in the step 2) is between 50mW and 100 mW.
5. The method for detecting the optical field polarization distribution of the optofluidic chip based on the gold nanorod colloids as claimed in claim 1, wherein the polarization mode in the step 2) is selected according to the measurement requirement.
6. The method for detecting the optical field polarization distribution of the optofluidic chip based on the gold nanorod colloids as claimed in claim 1, wherein the laser operating wavelength in step 2) is selected within the visible light range and the infrared light range.
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Family Cites Families (2)

* Cited by examiner, † Cited by third party
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US7768654B2 (en) * 2006-05-02 2010-08-03 California Institute Of Technology On-chip phase microscope/beam profiler based on differential interference contrast and/or surface plasmon assisted interference
CN101487932B (en) * 2009-02-23 2010-06-16 南京邮电大学 Magneto-optic rotation reinforced device

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Concentric circular grating generated by the patterning trapping of nanoparticles in an optofluidic chip;Hailang Dai et al.;《Scientific Reports》;20160823;第2页第2段至第6页第1段，图3-5 *
Quanitative optical trapping of single gold nanorods;Christine Selhuber-Unkel et al.;《Nano Letters》;20080823;第8卷(第9期);第2999页第1栏第1段 *
Rotating Au nanorod and nanowire driven by circularly polarized light;Jiunn-Woei Liaw et al.;《Optics Express》;20141015;第22卷(第21期);说明书第3.1节 *

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