1. A fluorescence detection sensing device based on cavity enhanced surface plasmon resonance is characterized in that: the device comprises a laser light source (1), a band-pass filtering unit (2), a light beam coupler (3), a high-reflection cavity unit (4), a long-wave pass filter (5), a focusing lens and a light information receiving unit (6);

the laser light source (1) is a tunable laser or a multi-wavelength laser and is used for emitting light beams with various single frequencies; the band-pass filter unit (2) comprises a blue algae fluorescence excitation band-pass filter (21) and a chlorophyll fluorescence excitation band-pass filter (22) and is used for selecting light beams in blue algae or chlorophyll fluorescence excitation wave bands and then sending the light beams into the light beam coupler (3); the high reverse cavity unit (4) comprises a sealed water inlet (44), a sealed water outlet (45), a high reverse cavity (41), a metal layer (42) and a nano particle layer (43); the high reflection cavity (41) is divided into a light inlet part, a reflection part and a light outlet part, and the light beam coupler (3) is arranged outside the light inlet part of the high reflection cavity (41) and is tangent to the outside of the high reflection cavity (41) and used for coupling screened light into the high reflection cavity (41) unit; the metal layer (42) and the nanoparticle layer (43) are arranged inside the reflecting part of the high reflection cavity (41) and do not overlap with each other; the long-wave pass filter (5) is arranged at the light emergent part of the high reflection cavity (51) and used for blocking non-fluorescence signals and leading the fluorescence signals out of the cavity; the optical information receiving unit (7) is arranged outside the long-wave pass filter (5), and a focusing lens (6) is arranged between the long-wave pass filter (5) and the optical information receiving unit (7).

2. The fluorescence detection sensing device based on cavity enhanced surface plasmon resonance of claim 1, wherein: the wavelength adjusting range of the light beam emitted by the laser light source (1) is 400-625 nm.

3. The fluorescence detection sensing device based on cavity enhanced surface plasmon resonance of claim 1, wherein: the wavelength range of the light beam allowed to pass through by the blue algae fluorescence excitation band-pass filter (21) is 500-625 nm, and the wavelength range of the light beam allowed to pass through by the chlorophyll fluorescence excitation band-pass filter (22) is 400-550 nm.

4. The fluorescence detection sensing device based on cavity enhanced surface plasmon resonance of claim 1, wherein: the beam coupler (3) is a prism coupler or an optical fiber coupler.

5. The fluorescence detection sensing device based on cavity enhanced surface plasmon resonance of claim 1, wherein: the high reflection cavity (41) is a three-quarter spherical high reflection cavity made of SiO₂The thickness of the cavity wall is 5-10 μm, and the diameter of the cavity is 0.5-2.5 cm.

6. The fluorescence detection sensing device based on cavity enhanced surface plasmon resonance of claim 1, wherein: the nanoparticles of the nanoparticle layer (43) are of a core-shell structure, the particle diameter is 50-80 nm, and the nanoparticle layer comprises a gold nanolayer and a silicon dioxide nanolayer wrapped outside the gold nanolayer and is used for enhancing a fluorescence sensing signal.

7. The fluorescence detection sensing device based on cavity enhanced surface plasmon resonance as claimed in claim 1 or 5, wherein: the metal layer (42) is a gold film with the thickness of 50-80 nm and is arranged on the opposite side of the quarter gap of the high reflecting cavity (41).

8. The fluorescence detection sensing device based on cavity enhanced surface plasmon resonance as claimed in claim 1 or 5, wherein: the cut-off wavelength of the long-wave pass filter (5) is 630nm and is arranged at the quarter gap of the high reflection cavity (41).

9. The fluorescence detection sensing device based on cavity enhanced surface plasmon resonance of claim 1, wherein: the optical information receiving unit (7) is a photodiode, a photomultiplier tube or an avalanche diode.

10. The fluorescence detection sensing device based on cavity enhanced surface plasmon resonance of claim 1, wherein: the system also comprises an optical information processing unit (8) which is used for analyzing and processing the information received by the optical information receiving unit to obtain the concentration of blue algae and chlorophyll in the water body; the optical information processing unit (8) comprises a microprocessor (81), a display screen (82), a wireless device (83) and a monitoring host (84).

Background

Water is a source of life, human lives and lives cannot be kept away from boiling water, but the problem of water quality pollution is frequent in various countries all over the world, so that huge economic losses are brought to the countries, and the lives and body health of people are influenced more continuously. In the aspect of water pollution, the eutrophication problem of rivers and lakes is becoming more serious, and the eutrophication can directly cause the generation of cyanobacterial bloom, which can cause extremely serious influence on the normal life of surrounding residents. Therefore, continuous monitoring of the content of blue algae and chlorophyll in water is extremely necessary.

At present, the concentration of blue algae and chlorophyll is mostly judged by the fluorescence intensity of the blue algae and the chlorophyll under specific wavelength, and the fluorescence intensity and the concentration of the blue algae and the chlorophyll are in direct proportion. Reference 1(CN 102128799 a) discloses a water quality detection sensor, which can detect the concentration of a colored soluble organic substance in water while detecting the concentration of a blue-green alga, so as to detect the eutrophication of lake water and warn the outbreak of the blue-green alga. But the accuracy is lower, and the blue algae detection with ultralow concentration cannot be realized.

In order to improve the detection sensitivity of the water quality detection sensor to water quality parameters, a reference 2(CN 106092895 a) discloses an in-situ detection device for water chlorophyll concentration and a detection method thereof, wherein the in-situ detection device for water chlorophyll concentration uses total reflection of a hexagonal prism cavity, increases a laser optical path to improve the detection sensitivity, can detect chlorophyll with 0.001-0.05 μmol/L order of magnitude concentration, and has the advantages of high fluorescence detection accuracy and high sensitivity. However, when the concentration of chlorophyll is less than 0.001 mu mol/L order of magnitude, the number of fluorescence photons which can be detected by the water body detection concentration in-situ detection device is less than 200, the detection sensitivity is greatly reduced, and the continuous use is difficult.

Therefore, it is necessary to design a device capable of simultaneously and clearly detecting the blue algae and the chlorophyll with lower concentration, and the device can reflect the content of the blue algae and the chlorophyll in water in time, further reflect the condition of water quality, so as to be beneficial to discovering the problems of the water quality in time and take effective relieving and solving measures for the problems.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a fluorescence detection sensing device based on cavity-enhanced surface plasmon resonance, which increases the laser optical path by using a high anti-resonant cavity, enhances the fluorescence intensity by the plasma resonance effect of a metal layer and a metal nano particle layer, improves the detection precision and sensitivity, and simultaneously realizes the high-precision detection of the content of blue algae and chlorophyll in a water body by using a device in cooperation with a band-pass filter unit.

A fluorescence detection sensing device based on cavity enhanced surface plasma resonance comprises a laser light source, a band-pass filtering unit, a light beam coupler, a high-reflection cavity unit, a long-wave pass filter, a focusing lens, a light information receiving unit and a processing unit.

The laser light source is a tunable laser or a multi-wavelength laser with adjustable frequency and is used for emitting light beams with various single frequencies; the band-pass filter unit comprises a blue algae fluorescence excitation band-pass filter and a chlorophyll fluorescence excitation band-pass filter, and is used for selecting a light beam in a blue algae or chlorophyll fluorescence excitation waveband and then sending the light beam into the light beam coupler; the high reverse cavity unit comprises a sealed water inlet, a sealed water outlet, a high reverse cavity, a metal layer and a nano particle layer; the high reflection cavity comprises a light inlet part, a reflection part and a light outlet part. The light beam coupler is arranged on the outer side of the light inlet part of the high-reflection cavity, is externally tangent to the high-reflection cavity and is used for coupling the screened light into the high-reflection cavity unit; the metal layer and the nano particle layer are arranged on the inner side of the reflecting part of the high reflection cavity; the long-wave pass filter is arranged on the outer side of the light outlet part of the high reflection cavity and used for blocking the short-wavelength non-fluorescence signals, enabling the long-wavelength fluorescence signals to pass through and leading the fluorescence signals out of the cavity; the outer side of the long-wave pass filter is provided with an optical information receiving unit, the long-wave pass filter and the optical information receiving unit are also provided with focusing lenses which are used for converging fluorescence passing through the long-wave pass filter and transmitting a fluorescence signal to the optical information receiving unit, and the processing unit analyzes and processes the information received by the optical information receiving unit to obtain the concentration of blue algae and chlorophyll in the water body.

Preferably, the wavelength of the light beam emitted by the laser light source is adjusted within a range of 400-625 nm.

Preferably, the wavelength range of the light beam allowed to pass through by the blue algae fluorescence excitation band-pass filter is 500-625 nm, and the wavelength range of the light beam allowed to pass through by the chlorophyll fluorescence excitation band-pass filter is 400-550 nm.

Preferably, the beam coupler is a prism coupler or a fiber coupler.

Preferably, the high-reflection cavity is a three-quarter spherical high-reflection cavity made of SiO₂The thickness of the cavity wall is 5-10 μm, and the diameter of the cavity is 0.5-2.5 cm.

Preferably, the nanoparticles of the nanoparticle layer are of a core-shell structure, the particle diameter is 50-80 nm, and the nanoparticle layer comprises a gold nanolayer and a silicon dioxide nanolayer wrapped outside the gold nanolayer and is used for enhancing a fluorescence sensing signal of the detected liquid;

preferably, the metal layer is a gold thin film with the thickness of 50-80 nm and is arranged on the opposite side of the long-wave pass filter.

Preferably, the cut-off wavelength of the long-wavelength pass filter is 630 nm.

Preferably, the optical information receiving unit is a photodiode, a photomultiplier tube, or an avalanche diode.

Preferably, the optical information processing unit comprises a microprocessor, a display screen, a wireless device and a monitoring host.

When the concentration of blue algae and chlorophyll in a water body needs to be detected, the water body to be detected enters a high reflection cavity from a sealed water inlet, light beams emitted by a laser source respectively pass through a blue algae fluorescence excitation band-pass filter and a chlorophyll fluorescence excitation band-pass filter, the screened light beams are coupled into the high reflection cavity through a light beam coupler, the light beams are reflected for multiple times in the high reflection cavity and are in full contact with the liquid to be detected to generate fluorescence, the fluorescence is amplified by secondary enhancement under the plasma resonance action of a metal layer and a nanoparticle layer, is led out of the cavity through a long-wave pass filter, and is received and processed by an optical information receiving unit and a processing unit after passing through a focusing lens, so that the concentration of the blue algae and the chlorophyll is obtained.

The invention has the following beneficial effects:

1. the light beams emitted by the laser light source are screened through the band-pass filter unit, so that the device only detects one substance at a time, and the mutual interference of fluorescence spectrums excited by different substances is avoided.

2. The laser entering the high-reflection cavity is highly reflected in the cavity, the optical path is increased, and after the laser is fully contacted with the liquid to be detected for many times, blue algae and chlorophyll are excited to emit fluorescent signals, the metal layer arranged on the inner wall of the high-reflection cavity generates a surface plasma resonance effect under the excitation light, the nano particle layer generates a surface fluorescence enhancement effect under the excitation light, the intensity of the excitation fluorescence is enhanced, and the detection sensitivity and precision of the device are improved.

3. A focusing lens is arranged between the long-wave pass filter and the information acquisition device, so that the fluorescence signal intensity is further enhanced, and the detection sensitivity is improved.

4. Blue algae and chlorophyll with the concentration of 0.001 mu mol/L magnitude can be detected, and compared with the existing detection sensor, the detection precision is improved by 1-2 magnitude.

Drawings

Fig. 1 is a schematic structural diagram of a detection apparatus in an embodiment.

Detailed Description

The invention is further explained below with reference to the drawings;

as shown in fig. 1, a fluorescence detection sensing device based on cavity enhanced surface plasmon resonance includes a laser light source 1, a band-pass filter unit 2, a beam coupler 3, a high reflection cavity unit 4, a long-wavelength pass filter 5, a focusing lens 6, an optical information receiving unit 7 and a processing unit 8.

The laser light source 1 is a tunable laser with adjustable frequency and can emit a wavelength of 400-625 nm; the band-pass filter unit 2 comprises a blue algae fluorescence excitation band-pass filter 21 and a chlorophyll fluorescence excitation band-pass filter 22, the wavelength band of the light beam allowed to pass through by the blue algae fluorescence excitation band-pass filter 21 is 500-625 nm, the wavelength band of the light beam allowed to pass through by the chlorophyll fluorescence excitation band-pass filter 22 is 400-550 nm, and the band-pass filter unit 2 is used for selecting the light beam of the blue algae or chlorophyll fluorescence excitation band and then sending the light beam into the light beam coupler.

The high anti-cavity unit 4 comprises a sealed water inlet 44, a sealed water outlet 45, a high anti-cavity 41, and a metal layer 42 and a nano-particle layer 43 which are arranged on the inner side of the high anti-cavity 41; the water to be detected flows into the high reverse cavity 41 from the sealed water inlet 44, and flows out from the sealed water outlet 45 after detection is finished; the high-reflection cavity 41 is a three-quarter spherical high-reflection cavity, the length of the nanoparticle layer 43 is less than 1/4 of the circumference of the high-reflection cavity, the nanoparticles are of a core-shell structure, the diameter of the nanoparticles is 50-80 nm, the nanoparticles comprise a gold nanolayer and a silicon dioxide nanolayer wrapped outside the gold nanolayer, and the nanoparticles generate a surface fluorescence enhancement effect on liquid to be detected under laser irradiation; the metal layer 42 is a gold film, is positioned on the opposite side of the notch of the high reflection cavity 1/4, has the length of 1/4 of the circumference of the high reflection cavity and the thickness of 50-80 nm, realizes surface plasma resonance under laser irradiation, and enhances and amplifies a fluorescence signal generated in the cavity.

The light beam coupler 3 is a prism coupler, is arranged on the outer side of the high reflecting cavity 41, is externally tangent to the high reflecting cavity 41 and is used for coupling screened light into the high reflecting cavity unit 4;

as the fluorescence emission wavelength of the blue algae is about 650nm and the fluorescence emission wavelength of the chlorophyll is about 670nm, the cut-off wavelength of the long-wave pass filter 5 is 630nm to reflect non-fluorescence signals with the wavelength less than 630nm, so as to reduce interference. The long-wave pass filter 5 is arc-shaped, is arranged at the 1/4 notch of the high-reflection cavity 41 and is symmetrically distributed with the metal layer 42, and the scattered fluorescent signal generated by the metal layer 42 and having excellent convergence effect on the fluorescent signal in the spherical high-reflection cavity can be more fully led out from the long-wave pass filter 5.

The focusing lens 6 is used for converging the fluorescence passing through the long-wave pass filter 5 and transmitting the fluorescence signal to the optical information receiving unit 7, the optical information receiving unit 7 is a photodiode, the light sensing window of the photodiode is limited, and the fluorescence signal selected by the long-wave pass filter 5 is converged at the light sensing window of the photodiode after being converged by the focusing lens 6, so that the intensity of the detected fluorescence signal is further enhanced, and the detection sensitivity is improved. The processing unit 8 comprises a microprocessor 81, a display screen 82, a wireless device 83 and a monitoring host 84, and is used for analyzing and processing the information received by the optical information receiving unit to obtain the concentration of the blue algae and chlorophyll in the water body.

The detection method of the blue algae concentration comprises the following steps: the liquid to be measured enters from the sealed water inlet 44, light beams emitted by the laser light source 1 pass through the blue-green algae fluorescence excitation band-pass filter 21, the blue-green algae fluorescence excitation band-pass filter 21 selects light with a wave band of 500-625 nm, and then the light beams are coupled into the high reflection cavity 41 through the light beam coupler 3, the light beams entering the high reflection cavity 41 can continuously and highly reflect with the inner cavity wall in the cavity, are fully contacted with the liquid to be measured for many times and excite the liquid to generate fluorescence signals, meanwhile, the excitation light beams are contacted with the metal layer 42 arranged in the cavity under the reflection effect and excite the surface plasma resonance fluorescence enhancement effect, are contacted with the nanoparticle layer 43 in the cavity and excite the surface fluorescence enhancement effect, and the fluorescence signals can be continuously enhanced and amplified under the dual effects of cavity enhancement and surface plasma resonance. The long-wavelength-pass filter 5 reflects light with a wavelength less than 630nm, light with a wavelength greater than 630nm and containing enhanced fluorescent signals passes through, the fluorescent signals after undergoing cavity enhancement and surface plasma resonance dual enhancement amplification are converged by the focusing lens 6, enter the optical information receiving unit 7 to be received, and finally parameters such as the concentration of the ultra-low-concentration blue algae are collected and processed by the optical information processing unit 8.

The detection method of the chlorophyll concentration comprises the following steps: the liquid to be measured enters from the sealed water inlet 44, light beams emitted by the laser light source 1 pass through the chlorophyll fluorescence excitation band-pass filter 22, the chlorophyll fluorescence excitation band-pass filter 22 selects light with a wave band of 400-550 nm, and then the light beams are coupled into the high reflection cavity 41 through the light beam coupler 3, the light beams entering the high reflection cavity 41 can continuously and highly reflect on the inner cavity wall, and are fully contacted with the liquid to be measured for many times and excite the liquid to generate fluorescence signals, meanwhile, the excitation light beams are contacted with the metal layer 42 arranged in the cavity under the reflection effect and excite to generate a surface plasma resonance fluorescence enhancement effect, and are contacted with the nanoparticle layer 43 in the cavity and excite to generate a surface fluorescence enhancement effect, and the fluorescence signals can be continuously enhanced and amplified under the dual effects of cavity enhancement and surface plasma resonance. The long-wavelength-pass filter 5 reflects light with a wavelength less than 630nm, light with a wavelength greater than 630nm and containing enhanced fluorescent signals passes through, the fluorescent signals after undergoing cavity enhancement and surface plasmon resonance dual enhancement amplification undergo a converging effect through the focusing lens 6, enter the optical information receiving unit 7 to be received, and finally parameters such as the concentration of chlorophyll with ultralow concentration are collected and processed through the optical information processing unit 8.