CN116465948A - Microfluidic photoelectrochemical sensor and microfluidic photoelectrochemical sensing device - Google Patents
Microfluidic photoelectrochemical sensor and microfluidic photoelectrochemical sensing device Download PDFInfo
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
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Abstract
The invention relates to a microfluidic photoelectrochemical sensor and a microfluidic photoelectrochemical sensing device, comprising: a working electrode; the printing electrode comprises a substrate, a reference electrode and a counter electrode, wherein the reference electrode and the counter electrode are arranged on the substrate, a solution passing hole is formed between the reference electrode and the counter electrode, and the solution passing hole is a through hole; the microfluidic layer is provided with a liquid inlet, a liquid outlet and a fluid microchannel communicated with the liquid inlet and the liquid outlet; the fluid micro-channel is spanned on the reference electrode and the counter electrode and is communicated with the solution through the hole; the microfluidic liquid injection mechanism comprises an automatic injection part and a solution collection part, wherein the automatic injection part is communicated with the liquid inlet, and the solution collection part is communicated with the liquid outlet; the working electrode, the printing electrode and the microfluidic layer are tightly attached together from bottom to top in sequence; the reference electrode, the counter electrode and the working electrode form a three-electrode system and are respectively and electrically connected with the electrochemical workstation. The invention improves the sensitivity.
Description
Technical Field
The invention relates to the technical field of microfluidic and photoelectrochemical sensing, in particular to a microfluidic photoelectrochemical sensor and a microfluidic photoelectrochemical sensing device.
Background
Identification, quantification and monitoring of compounds in different environments has been a focus of attention from environmental remediation clinical diagnostics. With the technical development of analytical laboratory instruments, such as gas chromatography-mass spectrometry, atomic spectrometry and the like, the detection and quantification of target analytes have high sensitivity and resolution, and the accurate determination of target compounds can be realized. However, analytical instruments also have some drawbacks. These instruments are often expensive, relatively complex to operate, often require maintenance and repair by experienced operators at regular intervals, and cannot be used in the field of continuous monitoring of target compounds.
Therefore, it is becoming more and more urgent to develop simple devices that can meet the important requirements of low cost, simple operation, and accurate measurement, and research and development of chemical sensors are being conducted to meet these urgent requirements. A chemical sensor is an instrument that converts chemical information (from concentration of a specific sample component to overall component analysis) into an electrical signal for detection. The chemical sensor corresponds generally to the human olfactory and gustatory organ, analogous to the human sensory organ. Meanwhile, a chemical sensor is also defined as a micro-device that can communicate information of the presence of specific compounds or ions in complex samples online in real time.
There are two main types of chemical sensors currently in widespread use and research, namely electrochemical and photoelectrochemical sensors. The electrochemical sensor has high background noise and high detection lower limit due to the fact that the excitation signal and the detection signal are both electric signals and the interference signal is strong, so that the electrochemical sensor is unfavorable for further development of the sensor (for example, wang S Z and the like, ACS Applied Nano Materials,2021,4 (6): 5808-5815). The photoelectrochemical sensor adopts an optical signal as an excitation source and an electric signal as a detection source, so that the device has the advantages of low background noise signal, difficulty in generating interference, easiness in detecting signals and the like (such as Limin Guo and the like, ACS Sensors 2017 (5), 621-625). However, although the two types of sensors have proposed a large number of novel structures and perform monitoring, the photoelectrochemical sensing research based on the micro-volume liquid to be detected is rarely performed, and the reported sensing performance of the existing photoelectrochemical sensing device is generally low, the requirement of the ultra-high detection sensitivity of biosensing cannot be met, meanwhile, the convenience and the practicability are insufficient, the micro-volume fluid cannot be controlled, and the small-dose liquid to be detected cannot be detected in a rapid and accurate mode. There is thus an urgent need to combine new technologies, while at the same time microfluidics emerges as a unique new field in that they can manipulate fluids in channels of several tens of microns in size, while microfluidic sensors convert a physical quantity into useful signals by means of a microfluidic platform, while sensors, which are very important units in control systems, are used to detect the physical and chemical properties of the system and can control and display various parameters. The defect that the existing chemical sensor cannot rapidly and accurately detect the small-dose liquid to be detected is well overcome by the aid of the microfluidic technology. In recent years, researchers at home and abroad have also made a great deal of research on microfluidic sensors (such as Ar mita Najmi et al, sensors and Actuators B: chemical, volume 333, 2021, 129569, ISSN 0925-4005) to develop a microfluidic electrochemical sensor, but since the electrochemical sensor usually adopts an electric signal as an excitation signal and a detection signal, the background noise is large, the maintenance cost is high, the stability is poor in sensing an object to be detected, and the suitability to a working electrode is insufficient. And (such as Xinyuan Mao, talanta, volume 238, part 2, 2022, 123052, ISSN 0039-9140) developed a microfluidic photoelectrochemical sensor, but because of being a cloth-based device, the whole microfluidic device has lower required environmental temperature, poor humidity resistance and heat resistance, difficult replacement, low sensing sensitivity for substances to be detected, and failure to meet detection requirements in actual life.
Disclosure of Invention
Therefore, the invention aims to solve the technical problem of low sensitivity of the sensor in the prior art.
In order to solve the technical problems, an aspect of the invention provides a microfluidic photoelectrochemical sensor, which comprises:
a working electrode;
the printing electrode comprises a substrate, a reference electrode and a counter electrode, wherein the reference electrode and the counter electrode are arranged on the substrate, a solution passing hole is formed between the reference electrode and the counter electrode, and the solution passing hole is a through hole;
the microfluidic layer is provided with a liquid inlet, a liquid outlet and a fluid microchannel communicated with the liquid inlet and the liquid outlet; the fluid micro-channel is spanned on the reference electrode and the counter electrode and is communicated with the solution through the holes, that is, two ends of the fluid micro-channel are respectively contacted with the reference electrode and the counter electrode, so that the to-be-measured liquid flows to the upper surfaces of the reference electrode and the counter electrode;
the working electrode, the printing electrode and the microfluidic layer are tightly attached together sequentially from bottom to top; the reference electrode, the counter electrode and the working electrode form a three-electrode system and are respectively and electrically connected with the electrochemical workstation.
In one embodiment of the invention, the present application further comprises a clamping mechanism comprising an upper clamping plate and a lower clamping plate detachably and sealingly connected; the lower clamping plate and the upper clamping plate are respectively clamped at the bottom of the working electrode and the top of the microfluidic layer;
the upper clamping plate is provided with a light hole for transmitting the excitation light source to the working electrode, and the light hole is communicated with the solution through hole.
In one embodiment of the invention, the front projection of the fluid microchannel on the working electrode and the front projection of the solution passing hole on the working electrode are both located within the front projection of the light transmitting hole on the working electrode along the thickness direction of the working electrode.
In one embodiment of the invention, the upper surface of the lower clamping plate is provided with a groove, and the working electrode, the printing electrode and the microfluidic layer are positioned in the groove, and the upper surface of the microfluidic layer is higher than the upper surface of the lower clamping plate and is tightly attached to the lower surface of the upper clamping plate.
In one embodiment of the invention, the solution passes through the aperture and the fluid microchannel with their longitudinal and transverse centerlines coincident;
the length of the fluid micro-channel is larger than the length of the solution passing hole, and the width of the fluid micro-channel is smaller than the width of the solution passing hole.
In one embodiment of the invention, the working electrode comprises a conductive substrate and a top layer nanopore array, the top layer nanopore array is arranged on the upper surface of the conductive substrate, and the top layer nanopore array comprises a plurality of nanopores arranged in a displaying manner; the bottom of the nano hole is provided with a plurality of small holes towards the direction of the conductive substrate, and the small holes form a bottom layer nano hole array.
In one embodiment of the invention, the working electrode further comprises an insulating waterproof protective layer disposed on the lower surface of the conductive substrate.
In one embodiment of the invention, the counter electrode and the reference electrode of the printed electrode are both arc-shaped structures, and the arc radii of the counter electrode and the reference electrode are the same;
one end of the counter electrode and one end of the reference electrode are respectively and electrically connected with the electrochemical workstation through the conductive part, and the other ends of the counter electrode and the reference electrode are close to each other and are not conducted.
In another aspect, the invention provides a microfluidic photoelectrochemical sensing device comprising:
the microfluidic photoelectrochemical sensor according to any of the embodiments above;
the microfluidic liquid injection mechanism comprises an automatic injection part and a solution collection part;
wherein, automatic injection portion with the inlet intercommunication, solution collection portion with the leakage fluid dram intercommunication.
In one embodiment of the invention, an automatic injection part includes a syringe, a stationary fixture, and an automatic pushing member;
the injector comprises a cylinder body and a plunger rod, the front end of the plunger rod is positioned in the cylinder body, the tail end of the plunger rod is connected with an automatic pushing component, the cylinder body is fixedly connected with a fixing clamp, and the automatic pushing component pushes the plunger rod to move along the axial direction of the injector;
the automatic pushing component comprises a power part, a screw and a nut, wherein the screw is connected with the power part, the power part drives the screw to rotate, and the screw is rotationally connected with the fixed clamp; the nut and the screw rod form a screw thread pair, and the nut is propped against the tail end of the plunger rod.
Compared with the prior art, the technical scheme of the invention has the following advantages:
specifically, the working electrode, the printing electrode and the microfluidic layer are tightly attached together in sequence from bottom to top, and the working electrode, the counter electrode and the reference electrode form a three-electrode system. The printing electrode and the microfluidic layer are respectively provided with a solution passing hole and a fluid micro-channel, so that the liquid to be detected flows from the solution passing hole and the fluid micro-channel to the working electrode to conduct a three-electrode system, thereby sensing. The three electrodes are respectively and electrically connected with the electrochemical workstation, so that the photoresponse current generated in the sensing of the liquid to be detected can be monitored in real time. Because working electrode, printing electrode and micro-fluidic layer are closely laminated together, the solution that awaits measuring of switching on three electrode system like this can only pass through solution through hole and working electrode contact, so working electrode effective area is the area of solution through hole, and this embodiment reduces working electrode effective area. In addition, in this embodiment, the automatic injection portion injects the liquid to be measured into the liquid inlet, the liquid to be measured flows to the reference electrode and the counter electrode through the fluid micro-channel, and then flows to the working electrode through the solution through the hole, so that the reference electrode, the counter electrode and the working electrode are conducted through the liquid to be measured. Then the liquid to be measured flows to the liquid outlet through the linear fluid micro-channel, and then is collected through the solution collecting part. Because the automatic injection part continuously injects the liquid to be measured into the liquid inlet in the working process, redundant liquid to be measured is discharged from the liquid outlet, so that the liquid to be measured of the sensor continuously circulates, the concentration of the liquid to be measured, which is conducted with the reference electrode, the counter electrode and the working electrode, is ensured to reach uniformity in the working process, and the change value of the concentration of the liquid to be measured is greatly reduced.
Therefore, the change value of the concentration of the solution to be detected is greatly reduced, and the effective area of the working electrode is reduced, so that the sensitivity of the photoelectrochemical sensor is improved.
Drawings
In order that the invention may be more readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings, in which
FIG. 1 is a schematic diagram of a microfluidic photoelectrochemical sensor of the invention;
FIG. 2 is a top view of one of the microfluidic photoelectrochemical sensors of FIG. 1 of the invention;
FIG. 3 is a cross-sectional view at A-A of one of the microfluidic photoelectrochemical sensors of FIG. 2 of the invention;
FIG. 4 is a schematic view of the structure of a lower clamping plate of the microfluidic photoelectrochemical sensor of FIG. 1;
FIG. 5 is a schematic view of the structure of a working electrode of the microfluidic photoelectrochemical sensor of FIG. 1;
FIG. 6 is a schematic diagram of the structure of a printed electrode in the microfluidic photoelectrochemical sensor of FIG. 1;
FIG. 7 is a schematic front view of a middle microfluidic layer of the microfluidic photoelectrochemical sensor of FIG. 1;
FIG. 8 is a schematic back view of a middle microfluidic layer of the microfluidic photoelectrochemical sensor of FIG. 1;
FIG. 9 is a schematic diagram of the structure of the upper clamping plate of the microfluidic photoelectrochemical sensor of FIG. 1;
FIG. 10 is a schematic view of a microfluidic liquid injection mechanism of the microfluidic photoelectrochemical sensor device of FIG. 1;
FIG. 11 is a scanning electron microscope image of a working electrode (n-type titanium dioxide with bottom and top nanopore arrays) in a microfluidic photoelectrochemical sensor of the invention;
FIG. 12 is a schematic diagram of a microfluidic photoelectrochemical sensor for sensing glucose in a test solution;
FIG. 13 is a graph of OCP change at 0.1M NaOH for an inventive microfluidic photoelectrochemical sensor based working electrode (n-type titania heterojunction);
FIG. 14 is a graph of current versus potential change at different concentrations of glucose based on a microfluidic photoelectrochemical sensor working electrode (n-type titania heterojunction);
FIG. 15 is a graph of photocurrent density variation for different concentrations of glucose under simulated sunlight based on a microfluidic photoelectrochemical sensor working electrode (n-type titania heterojunction) at a bias voltage of 0.2V;
FIG. 16 is a graph of a fitted sensing sensitivity to different concentrations of glucose based on a microfluidic photoelectrochemical sensor working electrode (n-type titania heterojunction) under a 0.2V bias, simulated solar illumination;
FIG. 17 is a graph of a fit of the sensing sensitivity of a working electrode (n-type titania heterojunction) to different concentrations of glucose under simulated solar light at a bias of 0.2V based on a typical electrolytic cell (comparative example).
Description of the specification reference numerals: 100. a lower clamping plate; 110. a groove;
200. a working electrode; 210. a conductive substrate; 220. a top layer nanopore array; 230. a bottom layer nanopore array; 240. an insulating waterproof protective layer;
300. printing an electrode; 310. a substrate; 320. a reference electrode; 330. a counter electrode; 340. solution passing holes;
400. a microfluidic layer; 410. a liquid inlet; 420. a liquid outlet; 430. a fluid microchannel;
500. an upper clamping plate; 510. a light hole;
600. a microfluidic liquid injection mechanism; 610. a syringe; 611. a cylinder; 612. a plunger rod; 620. a fixing clamp; 630. an automatic pushing member; 631. a power section; 632. a screw rod; 633. and (3) a nut.
Detailed Description
The invention will be further described in connection with the accompanying drawings and specific examples which are set forth so that those skilled in the art will better understand the invention and will be able to practice it, but the examples are not intended to be limiting of the invention.
In this application, the terms "length", "width" and "thickness" are explained as follows: the "length" refers to the dimension in the extending direction of the solution passing hole, the "width" refers to the dimension in the direction perpendicular to the extending direction of the solution passing hole in the horizontal plane, the "thickness" refers to the dimension perpendicular to the horizontal plane, and the plane in which the working electrode is located is the horizontal plane.
Referring to fig. 10, the invention provides a microfluidic photoelectrochemical sensing device comprising: a microfluidic photoelectrochemical sensor and a microfluidic liquid injection mechanism 600, the microfluidic liquid injection mechanism comprising an automatic injection portion and a solution collection portion;
wherein the automatic injection part is communicated with the liquid inlet 410, and the solution collecting part is communicated with the liquid outlet 420.
Further, the automatic injection part includes a syringe 610, a fixing jig 620, and an automatic pushing member 630;
the syringe 610 includes a barrel 611 and a plunger rod 612, the front end of the plunger rod 612 is located in the barrel 611, the rear end of the plunger rod 612 is connected to an automatic pushing member 630, the barrel 611 is fixedly connected to a fixing jig 620, and the automatic pushing member 630 pushes the plunger rod 612 to move in the axial direction of the syringe 610. The front end of the cylinder 611 communicates with the liquid inlet 410 through a hose.
The automatic pushing component 630 comprises a power part 631, a lead screw 632 and a nut 633, wherein the lead screw 632 is connected with the power part 631, the power part 631 drives the lead screw 632 to rotate, and the lead screw 632 is rotationally connected with the fixed clamp 620; the nut 633 and the screw 632 form a screw pair, and the nut 633 abuts the tail end of the plunger rod 612.
The power portion 631 may be a motor.
Specifically, the embodiment realizes the function of continuously and uniformly automatically injecting the liquid to be detected.
The solution collecting part is a liquid collecting barrel which is communicated with the liquid outlet 420 through a hose.
The matching of the automatic injection part and the solution collecting part can perfectly realize the high flow of the liquid to be measured in the sensor.
Referring to fig. 1 to 9, the invention provides a microfluidic photoelectrochemical sensor comprising:
a working electrode 200;
the printed electrode 300 comprises a substrate 310, a reference electrode 320 and a counter electrode 330, wherein the reference electrode 320 and the counter electrode 330 are arranged on the substrate 310, a solution passing hole 340 is arranged between the reference electrode 320 and the counter electrode 330, and the solution passing hole 340 is a through hole, namely, is communicated to the upper surface of the working electrode 200; the substrate 310 is non-conductive, so that the working electrode 200 is separated from the printing electrode 300 by the substrate 310, the working electrode 200 is non-conductive with the reference electrode 320 and the counter electrode 330 of the printing electrode 300 in a non-working state, and the working electrode 200 is conductive with the reference electrode 320 and the counter electrode 330 of the printing electrode 300 through the liquid to be measured in a working state;
a microfluidic layer 400 provided with a liquid inlet 410, a liquid outlet 420 and a fluid microchannel 430 communicating the liquid inlet 410 and the liquid outlet 420; a fluid microchannel 430 spans the reference electrode 320 and the counter electrode 330 and communicates with the solution through the aperture 340;
wherein the working electrode 200, the printing electrode 300 and the microfluidic layer 400 are tightly attached together from bottom to top in sequence; the reference electrode 320, the counter electrode 330 and the working electrode 200 form a three-electrode system and are electrically connected to the electrochemical workstation, respectively.
In some comparative examples, the photoelectrochemical sensor is such that the three-electrode system is immersed directly in the solution to be measured in the electrolytic cell, so that the working electrode 200 is entirely in contact with the solution to be measured, and the solution to be measured is fixed and does not flow during the operation of the photoelectrochemical sensor, and the concentration around the working electrode is changed along with the oxidation-reduction reaction of the electrode surface, so that the stability is insufficient while the effective area of the working electrode is reduced. And the sensitivity is inversely proportional to the product of the change in concentration of the solution to be measured and the effective area of the working electrode 200 (the formula of the sensitivity calculation is as follows), the photoelectrochemical sensor of this embodiment has low sensitivity.
Specifically, the working electrode 200, the printing electrode 300 and the microfluidic layer 400 are tightly attached together in sequence from bottom to top, and the working electrode 200, the counter electrode 330 and the reference electrode 320 form a three-electrode system. The printed electrode 300 and the microfluidic layer 400 are provided with a solution passing hole 340 and a fluid micro-channel 430, respectively, so that the liquid to be measured flows from the solution passing hole 340 and the fluid micro-channel 430 to the working electrode 200 to conduct the three-electrode system, thereby performing sensing. The three electrodes are respectively and electrically connected with the electrochemical workstation, so that the photoresponse current generated in the sensing of the liquid to be detected can be monitored in real time. Because the working electrode 200, the printing electrode 300 and the microfluidic layer 400 are tightly attached together, the solution to be tested which is conducted into the three-electrode system can only contact with the working electrode 200 through the solution passing hole 340, so that the effective area of the working electrode 200 is the area of the solution passing hole 340, and the effective area of the working electrode 200 is reduced in the embodiment. In addition, in the present embodiment, the automatic injection part injects the liquid to be measured into the liquid inlet 410, the liquid to be measured flows to the reference electrode 320 and the counter electrode 330 through the fluid micro-channel 430, and then flows to the working electrode 200 through the liquid to be measured through the solution passing hole 340 and the solution passing hole 340, so that the reference electrode 320, the counter electrode 330 and the working electrode 200 are conducted through the liquid to be measured. Then, the liquid to be measured flows to the liquid outlet 420 through the linear fluid microchannel 430, and is collected by the solution collecting part. Because the automatic injection part continuously injects the solution to be measured into the liquid inlet 410 in the working process, the redundant solution to be measured is discharged from the liquid outlet 420, so that the solution to be measured of the sensor can continuously circulate, and the concentration of the solution to be measured, which is conducted with the reference electrode 320, the counter electrode 330 and the working electrode 200, is ensured to reach uniformity in the working process, namely, the variation value of the concentration of the solution to be measured is greatly reduced. In addition, since the flow rate of the liquid to be measured can be changed by the microfluidic liquid injection mechanism 600 in this embodiment, when the flow rate is matched with the reaction rate of the liquid to be measured when the working electrode 200 is illuminated, the stability of the photoelectrochemical sensor during monitoring can be greatly ensured while the sensitivity of the object to be measured is improved.
Therefore, the change value of the concentration of the solution to be measured is greatly reduced, and the effective area of the working electrode 200 is reduced, so that the sensitivity of the photoelectrochemical sensor is improved.
In addition, the cost of the embodiment is low, the reagent dosage is small, the sample volume is small, the response is high, the sensitivity is high, and the adaptability is high.
Further, the fluid micro-channel 430 is made of Polydimethylsiloxane (PDMS), which is an organic polymer that is biocompatible and has good permeability under light.
Further, the application also includes a clamping mechanism comprising an upper clamping plate 500 and a lower clamping plate 100 which are detachably and sealingly connected; the lower clamping plate 100 and the upper clamping plate 500 are respectively clamped at the bottom of the working electrode 200 and the top of the microfluidic layer 400;
the upper clamping plate 500 is provided with a light-transmitting hole 510 for transmitting the excitation light source to the working electrode 200, the light-transmitting hole 510 being in communication with the solution passing hole 340. Light (excitation light source) is given right above the light hole 510, and the light hole 510 can enable the working electrode 200 to fully absorb incident light, so that the working electrode 200 generates enough electron hole pairs, and detection of the liquid to be detected becomes more sensitive and accurate.
Specifically, the lower clamping plate 100 and the upper clamping plate 500 fix the entire sensor, ensuring its sealability. Therefore, the connection of each part and the tightness of the sensor when the liquid to be measured continuously circulates in the sensor are ensured, and convenience can be provided for the circulation of the liquid to be measured in the sensor, so that the sensitivity of the sensor is further improved.
In some possible embodiments, the upper clamping plate 500 and the lower clamping plate 100 are identical in structure and size. The upper clamping plate 500 and the lower clamping plate 100 are rectangular plates. The upper clamping plate 500 has a length and a width of 40mm to 50mm and a thickness of 5mm to 10mm.
In some possible embodiments, the excitation light source is any one of sunlight, simulated sunlight, and violet light. The excitation light source enters from the light-transmitting hole 510 and is then sufficiently absorbed by the working electrode 200 through the solution-passing hole 340.
In some possible embodiments, the printed electrode 300 has a length of 20mm to 25mm, a width of 12mm to 15mm, and a thickness of 0.1 to 0.3mm.
In some possible embodiments, the upper and lower clamping plates are made of plexiglas material.
Further, along the thickness direction of the working electrode 200, the front projection of the fluid micro-channel 430 on the working electrode 200 and the front projection of the solution through hole 340 on the working electrode 200 are located within the front projection of the light hole 510 on the working electrode 200.
Further, the upper surface of the lower clamping plate 100 is provided with a groove 110, and the working electrode 200, the printing electrode 300 and the microfluidic layer 400 are positioned in the groove 110, and the upper surface of the microfluidic layer 400 is higher than the upper surface of the lower clamping plate 100 and is tightly attached to the lower surface of the upper clamping plate 500.
In particular, the present embodiment provides the groove 110 so that the lower clamping plate 100 and the upper clamping plate 500 are further stably and reliably fastened thereto.
In some possible embodiments, the groove 110 extends to both sides of the lower clamping plate 100, and the groove 110 may be divided into two parts, one of which houses the working electrode 200 and the other of which houses the lead terminal of the conductive substrate 210 or the electrode adaptor of the printed electrode 300.
In some possible embodiments, the depth of the groove 110 is 2mm to 5mm.
Further, the lower clamping plate 100 and the upper clamping plate 500 are fixedly coupled by bolts.
Specifically, in this embodiment, the working electrode 200, the printing electrode 300 and the microfluidic layer 400 are tightly fastened by the lower clamping plate 100 and the upper clamping plate 500 for bolts, and the bolts can be quickly detached and installed, so that quick and accurate detection on different liquids to be detected under small dosage can be realized by installing the working electrodes 200 with different functions, and the suitability of the photoelectrochemical sensor is improved. Therefore, the working electrode 200 with different functions can be installed to rapidly and accurately detect the concentration of various liquids to be detected with high sensitivity, high stability and small dosage.
In some possible embodiments, the lower clamping plate 100 and the upper clamping plate 500 are provided with threaded holes at four corners, and the diameter of the threaded holes is 2mm to 5mm.
Further, the solution passes through the holes 340 and the fluid micro-channels 430, and the longitudinal and transverse central lines of the two are coincident;
the length of the fluid micro-channel 430 is greater than the length of the solution passing hole 340, and the width of the fluid micro-channel 430 is less than the width of the solution passing hole 340.
The fluid micro-channels 430 have a length of 12mm to 15mm, a width of 300 μm to 500 μm, and a depth of 300 μm to 500 μm.
The light transmission hole 510 has a length of 15mm to 20mm and a width of 5mm to 10mm.
The solution passing hole 340 has a length of 1mm to 2mm and a width of 0.5mm to 1mm.
Both the liquid inlet 410 and the liquid outlet 420 are circular holes. The inlet 410 and outlet 420 have equal diameters. The diameters of the liquid inlet 410 and the liquid outlet 420 are 300 μm to 500 μm.
Specifically, the size of the fluid micro-channel 430 in the present embodiment is in the micrometer level, so that the sensing of the sensor in the liquid to be measured is very small, and only about 100 μl of the liquid to be measured is needed to realize the sensing under high sensitivity, so that the liquid to be measured is saved and the sensitivity is improved.
Referring to fig. 5 and 11, the working electrode 200 includes a conductive substrate 210 and a top layer nanopore array 220, the top layer nanopore array 220 being disposed on an upper surface of the conductive substrate 210, the top layer nanopore array 220 including a plurality of nanopores arranged in a row; the bottom of the nanopore is provided with a plurality of small holes towards the conductive substrate 210, and the small holes form a bottom layer nanopore array 230.
The working electrode 200 further includes an insulating waterproof protective layer 240, and the insulating waterproof protective layer 240 is disposed on the lower surface of the conductive substrate 210.
The conductive substrate 210 has lead terminals disposed thereon that are electrically connected to the electrochemical workstation.
The counter electrode 330 and the reference electrode 320 of the printed electrode 300 are arc structures, and the arc radiuses of the two are the same;
the counter electrode 330 and the reference electrode 320 are electrically connected to the electrochemical workstation at one end thereof and are electrically disconnected from each other (i.e., disconnected from each other) at the other end thereof.
The counter electrode 330 is a carbon electrode, and the counter electrode 330 is prepared by printing.
The reference electrode 320 is a silver chloride electrode, and the reference electrode 320 is prepared by printing.
The counter electrode 330 and the reference electrode 320 have good stability and conductivity, and are low in cost.
The printed electrode 300 is provided with an electrode adapter for connecting the printed electrode 300 and an electrochemical workstation. The electrode adapter can ensure to a great extent the transmission of electrical signals of the internal sensor and of the external circuit (electrochemical workstation).
Further, the conductive substrate 210 of the working electrode 200 is a metallic titanium sheet having a thickness of 0.1 to 0.5 mm.
Alternatively, the n-type titanium dioxide layer is prepared by subjecting a conductive metallic titanium sheet substrate to anodic oxidation treatment twice.
The microfluidic layer 400 is provided with a solution passing hole 340, so that when the liquid to be measured circulates, the counter electrode 330 and the reference electrode 320 on the printed electrode 300 and the working electrode 200 can be conducted through the solution passing hole 340, thereby forming a three-electrode architecture under illumination.
The application can ensure that the trace liquid to be measured can not generate short circuit under the condition of continuous circulation, and can generate stable photoelectrochemical reaction with the liquid to be measured with different concentrations under the condition of illumination, thereby improving the sensitivity.
In the application process, the lower clamping plate 100, the working electrode 200, the printing electrode 300, the microfluidic layer 400 and the upper clamping plate 500 are assembled in sequence, and are sealed and fixed by screws. The automatic injection part is used for injecting the glucose to-be-measured liquid into the liquid inlet 410 through a catheter (a hose), and then the glucose to-be-measured liquid flows out through the liquid outlet 420, so that the high flow-through property of the to-be-measured liquid in the sensor and the recovery of glucose waste liquid are realized. After being injected through the liquid inlet 410 of the microfluidic layer 400, the glucose to be measured flows into the surface of the printing electrode 300 through the fluid micro-channel 430 of the microfluidic layer 400, and then flows into the surface of the working electrode 200 through the solution passing hole 340 in the middle of the printing electrode 300. And then the lead terminals arranged on the lower conductive substrate 210 of the working electrode 200 and the electrode adapters matched with the printing electrode 300 are respectively connected with an external circuit (electrochemical workstation), so that the light response current generated in the sensing of the glucose to-be-detected liquid is accurately monitored on line in real time.
As shown in fig. 12, when incident light irradiates the surface of the working electrode 200, the titanium dioxide in the working electrode 200 generates electron-hole pairs, the surface charge of the titanium dioxide selectively reacts with glucose molecules to generate oxidation reaction, and the photo-generated electrons flow to the counter electrode 330 through the conductive substrate 210 to generate corresponding reduction reaction, so that photocurrent response is formed between the working electrode 200 and the counter electrode 330; the connected electrochemical workstation can monitor the current in real time, and the displayed photoelectric value shows the characteristic of positive correlation with the concentration of the glucose to be detected, so that the rapid and accurate detection of high sensitivity and high fluxion of the glucose to be detected under small dosage is realized.
The following experimental verification was performed for the present application (in this verification, the working electrode 200 employs an n-type titanium dioxide nanotube, and the test solution is a glucose test solution):
after the assembly of the microfluidic photoelectrochemical sensor is completed in the above sequence, the micro-booster is used to inject the glucose to be measured into the microfluidic layer 400 through the conduit at a flow rate of 20 μl/min, and when the solution is observed to flow out at a flow rate of about 20 μl/min through the liquid outlet of the microfluidic layer 400, it is indicated that the glucose to be measured maintains high fluidity in the sensor, and the effluent from the sensor flows into the prepared collection barrel or beaker through the liquid outlet, so as to complete the recovery of the glucose effluent.
The OCP profile was measured for the sensor with or without simulated solar illumination at 0.1M NaOH. As shown in fig. 13, the open circuit potential is very stable with time in the presence or absence of simulated solar illumination, illustrating the tandem effect of counter electrode 330, reference electrode 320 and working electrode 200 on printed electrode 300, and the stable three-electrode architecture under illumination.
A plot of current versus potential was tested for different concentrations of glucose. As shown in fig. 14, after the working electrode 200 (n-type titanium dioxide heterojunction) is mounted, the sensor has an obvious rectifying effect on the sensing of the glucose test solution under the simulated sunlight, and as the solubility of the glucose test solution increases, the photoresponsive current also increases.
Then according to the curve graph of current with potential change, inA plot of photocurrent density versus time was tested for different concentrations of glucose under a 0.2V bias voltage and simulated solar light. As shown in fig. 15, as the solubility of the glucose test solution increases, the photocurrent density also increases in the forward direction, which accords with the expected effect of the experiment. And the sensitivity was fitted to the sensitivity of the sensor as shown in FIG. 16, with a sensitivity of up to 90. Mu.A mM -1 cm -2 。
In addition, a set of comparative experiments were performed in which the same working electrode 200 (n-type titania heterojunction) was placed in a general electrolytic cell (comparative example) and the glucose test solution was sensed under the same test conditions, and then the sensing sensitivity was fitted. As shown in FIG. 17, the sensitivity was 4.1. Mu.A mM -1 cm -2 。
From the experimental results, the sensitivity of the sensor is obviously higher than that of a common photoelectrochemical sensor.
The test results fully illustrate the structure adopted by the sensor according to the scheme, so that the microfluidic photoelectrochemical sensor has very high adaptability to the working electrode 200, and the high sensitivity, high fluxion and real-time rapid and accurate detection of different liquids to be tested under small dosage can be realized by installing the working electrode 200 with different functions.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. And obvious changes and modifications which are extended therefrom are still within the scope of the invention.
Claims (10)
1. A microfluidic photoelectrochemical sensor, characterized in that: comprising the following steps:
a working electrode;
the printing electrode comprises a substrate, a reference electrode and a counter electrode, wherein the reference electrode and the counter electrode are arranged on the substrate, a solution passing hole is formed between the reference electrode and the counter electrode, and the solution passing hole is a through hole;
the microfluidic layer is provided with a liquid inlet, a liquid outlet and a fluid microchannel communicated with the liquid inlet and the liquid outlet; the fluid micro-channel is spanned on the reference electrode and the counter electrode and is communicated with the solution through holes;
the working electrode, the printing electrode and the microfluidic layer are tightly attached together in sequence from bottom to top; the reference electrode, the counter electrode and the working electrode form a three-electrode system and are respectively and electrically connected with an electrochemical workstation.
2. The microfluidic photoelectrochemical sensor according to claim 1, wherein: the clamping mechanism comprises an upper clamping plate and a lower clamping plate which are detachably and hermetically connected; the lower clamping plate and the upper clamping plate are respectively clamped at the bottom of the working electrode and the top of the microfluidic layer;
the upper clamping plate is provided with a light-transmitting hole for transmitting the excitation light source to the working electrode, and the light-transmitting hole is communicated with the solution passing hole.
3. The microfluidic photoelectrochemical sensor according to claim 2, wherein: and along the thickness direction of the working electrode, the orthographic projection of the fluid micro-channel on the working electrode and the orthographic projection of the solution passing hole on the working electrode are both positioned in the orthographic projection of the light transmitting hole on the working electrode.
4. The microfluidic photoelectrochemical sensor according to claim 2, wherein: the upper surface of lower grip block is equipped with the recess, working electrode the printing electrode with the micro-fluidic layer is located in the recess, the upper surface of micro-fluidic layer is higher than the upper surface of lower grip block and with the lower surface of upper grip block closely laminates.
5. The microfluidic photoelectrochemical sensor according to claim 1, wherein: the solution passes through the holes and the fluid micro-channels, and the longitudinal and transverse central lines of the holes and the fluid micro-channels are overlapped;
the length of the fluid micro-channel is greater than the length of the solution passing hole, and the width of the fluid micro-channel is smaller than the width of the solution passing hole.
6. The microfluidic photoelectrochemical sensor according to claim 1, wherein: the working electrode comprises a conductive substrate and a top layer nanopore array, wherein the top layer nanopore array is arranged on the upper surface of the conductive substrate and comprises a plurality of nanopores which are arranged in a displaying way; the bottom of the nanopore is provided with a plurality of small holes towards the direction of the conductive substrate, and the small holes form a bottom layer nanopore array.
7. The microfluidic photoelectrochemical sensor according to claim 6, wherein: the working electrode further comprises an insulating waterproof protection layer, and the insulating waterproof protection layer is arranged on the lower surface of the conductive substrate.
8. The microfluidic photoelectrochemical sensor according to claim 1, wherein: the counter electrode and the reference electrode of the printed electrode are arc structures, and the arc radiuses of the counter electrode and the reference electrode are the same;
one end of the counter electrode and one end of the reference electrode are respectively and electrically connected with the electrochemical workstation through a conductive part, and the other ends of the counter electrode and the reference electrode are close to each other and are not conducted.
9. A microfluidic photoelectrochemical sensing device, characterized in that: comprising the following steps:
the microfluidic photoelectrochemical sensor of any of claims 1 to 8;
the microfluidic liquid injection mechanism comprises an automatic injection part and a solution collection part;
wherein, automatic injection portion with the inlet intercommunication, solution collection portion with the leakage fluid dram intercommunication.
10. The microfluidic photoelectrochemical sensing device according to claim 9, wherein: the automatic injection part comprises a syringe, a fixed clamp and an automatic pushing component;
the syringe comprises a barrel body and a plunger rod, the front end of the plunger rod is positioned in the barrel body, the tail end of the plunger rod is connected with the automatic pushing component, the barrel body is fixedly connected with the fixing clamp, and the automatic pushing component pushes the plunger rod to move along the axial direction of the syringe;
the automatic pushing component comprises a power part, a screw and a nut, wherein the screw is connected with the power part, the power part drives the screw to rotate, and the screw is rotationally connected with the fixing clamp; the nut and the screw rod form a screw thread pair, and the nut abuts against the tail end of the plunger rod.
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