Semiconductor quantum dot upconversion fluorescence spectrum detection system

Abstract

A semiconductor quantum dot upconversion fluorescence spectrum detection system, including laser, the pulsed laser emitted by laser is transmitted to the half mirror after being expanded by first and second lenses in turn, and the pulsed laser is divided into two light paths; in the reflected light path, the incident pulsed laser passing through the objective lens is focused on the surface of the semiconductor quantum dot sample, the semiconductor quantum dot sample radiates upconversion fluorescence after being excited, and the upconversion fluorescence and the reflected pulsed laser of the surface of the semiconductor quantum dot sample are transmitted to the half mirror through the objective lens into the transmitted light path after acting on the fluorescence enhancement substrate; in the transmitted light path, the transmitted fluorescence and the reflected pulsed laser passing through the half mirror enter the third lens through the optical filter, and then enter the spectrometer and EMCCD camera for fluorescence spectrum collection, the spectrometer and EMCCD camera are regulated and data processed by using the electronic computer, and the fluorescence spectrum of the semiconductor quantum dot sample is displayed, and the present application provides technical support for temperature detection in the living cells of biological organisms.

Description

Technical Field

[0001] This invention belongs to the field of fluorescence detection technology, specifically relating to a semiconductor quantum dot upconversion fluorescence spectroscopy detection system. Background Technology

[0002] Semiconductor quantum dots are a novel type of nanoluminescent material. Compared to traditional dyes, semiconductor quantum dots offer advantages such as high quantum yield, tunable emission wavelength, fluorescence stability, and ease of surface modification, leading to their widespread application in research fields such as biomolecular detection, cell fluorescence imaging, and multicolor labeling. Furthermore, due to the temperature-dependent fluorescence properties (intensity, full width at half maximum, peak wavelength) at the surface of semiconductor quantum dots, research on nanoscale in-situ thermometry within cells using semiconductor quantum dots has been extensively conducted. Since specific organelles within cells undergo temperature changes after disease progression, it is hoped that laser scanning of intracellular quantum dot probes can be used to construct a three-dimensional temperature field at the nanoscale within the cell, enabling precise analysis of diseased organelles in living organisms, which is of great significance for disease diagnosis and pathological research.

[0003] Considering that the fluorescence of semiconductor quantum dots requires excitation by an ultraviolet light source (Chem.Soc.Rev.,2013,doi.org / 10.1039 / C3CS60102A), and that ultraviolet light is destructive to living biological cells, it is currently difficult to widely apply semiconductor quantum dot fluorescence to temperature detection within living biological cells. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a semiconductor quantum dot upconversion fluorescence spectroscopy detection system. This system utilizes bio-friendly red or infrared light to excite semiconductor quantum dots to form upconversion fluorescence, and uses a femtosecond laser seed source in conjunction with a fluorescence-enhancing substrate to construct a semiconductor fluorescence detection system. This system enables precise detection and analysis of the conversion spectrum, providing technical support for temperature detection and other applications within living biological cells.

[0005] To achieve this objective, the technical solution adopted by the present invention is as follows:

[0006] A semiconductor quantum dot upconversion fluorescence spectroscopy detection system includes a laser 1. The pulsed laser emitted by the laser 1 is expanded by a first lens 2 and a second lens 3 and then transmitted to a semi-transparent mirror 4, which splits the pulsed laser into two optical paths, one being a reflected optical path and the other being a transmitted optical path. The second lens 3 is disposed on the back focal plane of the first lens 2.

[0007] In the reflected light path of the semi-transparent mirror 4, there is an objective lens 5, a stage 8, a fluorescence enhancement substrate 7, and a semiconductor quantum dot sample 6. The semiconductor quantum dot sample 6 is adsorbed on the fluorescence enhancement substrate 7, and the fluorescence enhancement substrate 7 is mounted on the stage 8. The incident pulsed laser light passing through the objective lens 5 is focused on the surface of the semiconductor quantum dot sample 6. After being excited, the semiconductor quantum dot sample 6 emits upconversion fluorescence. After the upconversion fluorescence interacts with the fluorescence enhancement substrate 7, it is transmitted together with the reflected pulsed laser light on the surface of the semiconductor quantum dot sample 6 through the objective lens 5 to the semi-transparent mirror 4 and enters the transmission light path.

[0008] The semi-transparent mirror 4 has a filter 9, a third lens 10, a spectrometer 11, and an EMCCD camera 12 in its transmission light path. The spectrometer 11 and the EMCCD camera 12 are connected, and the spectrometer 11 and the EMCCD camera 12 are connected to a computer 13. The transmitted fluorescence and reflected pulsed laser light passing through the semi-transparent mirror 4 enter the third lens 10 through the filter 9, and then enter the spectrometer 11 and the EMCCD camera 12 for fluorescence spectrum acquisition. The computer 13 is used to control and process the data of the spectrometer 11 and the EMCCD camera 12, and displays the fluorescence spectrum of the semiconductor quantum dot sample 6.

[0009] The laser 1 is a femtosecond laser system or a femtosecond laser seed source, with a center wavelength of 700nm to 800nm, an output power greater than 450mW, a repetition frequency greater than 70MHz, and a pulse width of no more than 100fs.

[0010] The fluorescence-enhancing substrate 7 includes a substrate on which a dielectric eccentric spherical cavity particle monolayer array is disposed. Semiconductor quantum dot samples 6 are adsorbed on the surface of the dielectric eccentric spherical cavity particle monolayer array. The material of the spherical cavity particles is amorphous silicon or crystalline silicon. The maximum shell thickness of the spherical cavity particles is between 30 nm and 80 nm. The spacing between adjacent sidewalls of the spherical cavity particle monolayer array is between 0 and 10 nm.

[0011] The semiconductor quantum dot sample 6 is made of cadmium telluride (CdTe), cadmium selenide (CdSe), zinc selenide (ZnSe), cadmium sulfide (CdS), zinc sulfide (ZnS) and their core-shell or core-shell-shell structures, with a quantum dot diameter of 2 nm to 5 nm.

[0012] The semiconductor quantum dot sample 6 is uniformly coated on the fluorescence enhancement substrate 7 by electrostatic adsorption. After the fluorescence enhancement substrate 7 is modified with hydroxyl groups on its surface, it is positively modified with 3-aminopropyltrimethoxysilane (APTMS) or polydiallyldimethylammonium chloride (PDDA). Finally, it is placed in an aqueous quantum dot colloid for 1 to 3 hours to complete the adsorption of quantum dots.

[0013] The beneficial effects of this invention are as follows:

[0014] This invention utilizes bio-friendly red or infrared light to excite semiconductor quantum dots, generating upconversion fluorescence. Since the upconversion fluorescence signal of quantum dots is relatively weak, a semiconductor fluorescence detection system is constructed using a femtosecond laser seed source in conjunction with a fluorescence-enhancing substrate. Specifically, when the semiconductor quantum dot sample 6 is irradiated by a laser, the incident pulsed laser and the emitted upconversion fluorescence resonate with the multi-level scattering modes of highly refractive dielectric particles on the surface of the fluorescence-enhancing substrate 7. This achieves effective excitation of the upconversion fluorescence of the semiconductor quantum dots using a low-power pulsed laser from the femtosecond laser seed source, enabling the detection of the upconversion spectrum of the semiconductor quantum dots. Because the infrared excitation source is non-destructive to living biological cells, it can be applied to labeling or temperature detection within living biological cells. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the system of the present invention;

[0016] Figure 2 This is a schematic diagram of the fluorescence-enhancing substrate of the present invention;

[0017] Figure 3 This is a schematic diagram of the fluorescence-enhanced substrate adsorbed quantum dot sample of the present invention;

[0018] Figure 4 The fluorescence spectra of cadmium telluride (CdTe) quantum dot samples excited by a 405 nm continuous laser and an upconversion fluorescence spectra excited by a 750 nm femtosecond laser are shown in the examples. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0020] Reference Figure 1 A semiconductor quantum dot upconversion fluorescence spectroscopy detection system includes a laser 1. The pulsed laser emitted by the laser 1 is expanded by a first lens 2 and a second lens 3 and then transmitted to a semi-transparent mirror 4, which splits the pulsed laser into two optical paths, one being a reflected optical path and the other being a transmitted optical path. The second lens 3 is set on the back focal plane of the first lens 2.

[0021] In the reflected light path of the semi-transparent mirror 4, there is an objective lens 5, a stage 8, a fluorescence enhancement substrate 7, and a semiconductor quantum dot sample 6. The semiconductor quantum dot sample 6 is adsorbed on the fluorescence enhancement substrate 7, and the fluorescence enhancement substrate 7 is mounted on the stage 8. The incident pulsed laser light passing through the objective lens 5 is focused on the surface of the semiconductor quantum dot sample 6. After being excited, the semiconductor quantum dot sample 6 emits upconversion fluorescence. After the upconversion fluorescence interacts with the fluorescence enhancement substrate 7, it is transmitted together with the reflected pulsed laser light on the surface of the semiconductor quantum dot sample 6 through the objective lens 5 to the semi-transparent mirror 4 and enters the transmission light path.

[0022] The semi-transparent and semi-reflective mirror 4 has a filter 9, a third lens 10, a spectrometer 11, and an EMCCD camera 12 in its transmission light path. The spectrometer 11 and the EMCCD camera 12 are connected, and the spectrometer 11 and the EMCCD camera 12 are connected to a computer 13. The transmitted fluorescence and reflected pulsed laser light passing through the semi-transparent and semi-reflective mirror 4 enter the third lens 10 through the filter 9, and then enter the spectrometer 11 and the EMCCD camera 12 for fluorescence spectrum acquisition. The computer 13 is used to control and process the data of the spectrometer 11 and the EMCCD camera 12, and displays the fluorescence spectrum of the semiconductor quantum dot sample 6.

[0023] The laser 1 is a femtosecond laser seed source with a center wavelength of 750nm, an output power of 500mW, a repetition frequency of 80MHz, and a pulse width of 100fs.

[0024] The semiconductor quantum dot sample 6 is made of cadmium telluride (CdTe) semiconductor quantum dots with a diameter of 3.4 nm.

[0025] Reference Figure 2 The fluorescence-enhancing substrate 7 includes a substrate 7-1, on which an amorphous silicon eccentric spherical cavity particle monolayer array 7-2 with an inner diameter of 220 nm and an outer diameter of 290 nm is provided. The maximum thickness of the silicon spherical shell is about 70 nm, and the spacing between adjacent particles is about 0.

[0026] Reference Figure 3 The fluorescence enhancement substrate 7 was subjected to surface oxygen plasma cleaning at a power of 100W for 90 seconds to make the surface negatively charged. Then it was placed in 50 ml of 1% PDDA solution for 10 minutes. Finally, it was placed in aqueous CdTe quantum dot colloid and left to stand for 1 hour. This process was repeated 3 times. Semiconductor quantum dot sample 6 was adsorbed on the surface of the amorphous silicon eccentric spherical cavity particle monolayer array 7-2, thus forming a fluorescence enhancement substrate with uniformly adsorbed CdTe quantum dots on the surface.

[0027] The working principle of this embodiment is as follows:

[0028] The pulsed laser from the femtosecond laser seed source is expanded by the first lens 2 and the second lens 3 and then transmitted to the semi-transparent mirror 4, which splits the pulsed laser into two optical paths: a reflection path and a transmission path. In the reflection path of the semi-transparent mirror 4, the incident pulsed laser, after passing through the objective lens 5, is focused on the surface of the CdTe semiconductor quantum dot sample 6. The CdTe semiconductor quantum dot sample 6 is excited and emits upconversion fluorescence, which interacts with the silicon spherical cavity in the fluorescence enhancement substrate 7. The pulsed laser reflected from the surface of the CdTe semiconductor quantum dot sample 6 is then transmitted through the objective lens 5 to the semi-transparent mirror 4 and enters the transmission path. In the transmission path of the semi-transparent mirror 4, the fluorescence and reflected pulsed laser passing through the semi-transparent mirror 4 enter the third lens 10 through the filter 9, and then enter the spectrometer 11 and the EMCCD camera 12 for fluorescence spectrum acquisition. The spectrometer 11 is set with a fine grating, and the temperature of the EMCCD camera 12 is set to -98℃.

[0029] Reference Figure 4 The CdTe semiconductor quantum dot sample 6 adsorbed on the fluorescence-enhanced substrate 7 was subjected to 405nm continuous laser irradiation and according to... Figure 1 Excitation by the system's 750nm femtosecond laser seed source yields results such as Figure 4 The downconversion and upconversion fluorescence spectra shown demonstrate that the system of this invention can excite and detect the upconversion fluorescence spectrum of CdTe semiconductor quantum dot sample 6. Figure 4 The upconversion fluorescence peak wavelength of CdTe semiconductor quantum dots almost coincides with its downconversion fluorescence peak wavelength, and the upconversion fluorescence intensity is also high enough, making it promising for applications such as labeling or temperature detection in living cells.

[0030] The above description is merely an embodiment of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the present invention. These should also be considered within the scope of protection of the present invention.

Claims

1. A semiconductor quantum dot upconversion fluorescence spectroscopy detection system, comprising a laser (1), characterized in that: The pulsed laser emitted by the laser (1) is transmitted to the semi-transparent mirror (4) after passing through the first lens (2) and the second lens (3) in sequence to expand the beam. The pulsed laser is divided into two optical paths, one is a reflected optical path and the other is a transmitted optical path. The second lens (3) is set on the back focal plane of the first lens (2). In the reflected light path of the semi-transparent mirror (4), there is an objective lens (5), a stage (8), a fluorescence enhancement substrate (7), and a semiconductor quantum dot sample (6). The semiconductor quantum dot sample (6) is adsorbed on the fluorescence enhancement substrate (7), and the fluorescence enhancement substrate (7) is mounted on the stage (8). The incident pulsed laser through the objective lens (5) is focused on the surface of the semiconductor quantum dot sample (6). After the semiconductor quantum dot sample (6) is excited, it emits upconversion fluorescence. After the upconversion fluorescence interacts with the fluorescence enhancement substrate (7), it is transmitted together with the reflected pulsed laser on the surface of the semiconductor quantum dot sample (6) through the objective lens (5) to the semi-transparent mirror (4) and enters the transmission light path. In the transmission light path of the semi-transparent mirror (4), there is a filter (9), a third lens (10), a spectrometer (11) and an EMCCD camera (12). The spectrometer (11) and the EMCCD camera (12) are connected, and the spectrometer (11) and the EMCCD camera (12) are connected to the computer (13). The transmitted fluorescence and reflected pulsed laser light passing through the semi-transparent mirror (4) enter the third lens (10) through the filter (9), and then enter the spectrometer (11) and the EMCCD camera (12) for fluorescence spectrum acquisition. The computer (13) is used to control and process the data of the spectrometer (11) and the EMCCD camera (12), and displays the fluorescence spectrum of the semiconductor quantum dot sample (6). The fluorescence-enhancing substrate (7) includes a substrate on which a dielectric eccentric spherical cavity particle monolayer array is disposed. Semiconductor quantum dot samples (6) are adsorbed on the surface of the dielectric eccentric spherical cavity particle monolayer array. The material of the spherical cavity particles is amorphous silicon or crystalline silicon. The maximum shell thickness of the spherical cavity particles is between 30 nm and 80 nm. The spacing between adjacent sidewalls of the spherical cavity particle monolayer array is between 0 and 10 nm.

2. The system according to claim 1, characterized in that: The laser (1) is a femtosecond laser system or a femtosecond laser seed source, with a center wavelength of 700nm to 800nm, an output power greater than 450mW, a repetition frequency greater than 70MHz, and a pulse width of no more than 100fs.

3. The system according to claim 1, characterized in that: The semiconductor quantum dot sample (6) is made of cadmium telluride (CdTe), cadmium selenide (CdSe), zinc selenide (ZnSe), cadmium sulfide (CdS), zinc sulfide (ZnS) and their core-shell and core-shell-shell structures, with a quantum dot diameter of 2 nm to 5 nm.

4. The system according to claim 1, characterized in that: The semiconductor quantum dot sample (6) is uniformly covered on the fluorescence enhancement substrate (7) by electrostatic adsorption. After the fluorescence enhancement substrate (7) is modified with hydroxyl groups on its surface, it is positively modified with 3-aminopropyltrimethoxysilane (APTMS) or polydiallyldimethylammonium chloride (PDDA). Finally, it is placed in the quantum dot colloid synthesized in the aqueous phase for 1 to 3 hours to complete the adsorption of quantum dots.

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