CN112666243B - Light addressing square wave/alternating current volt-ampere electrochemical sensing system and method - Google Patents
Light addressing square wave/alternating current volt-ampere electrochemical sensing system and method Download PDFInfo
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- CN112666243B CN112666243B CN202011376443.2A CN202011376443A CN112666243B CN 112666243 B CN112666243 B CN 112666243B CN 202011376443 A CN202011376443 A CN 202011376443A CN 112666243 B CN112666243 B CN 112666243B
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Abstract
The application discloses a light addressing square wave/alternating current volt-ampere electrochemical sensing system and a method, wherein a semiconductor chip is fixed at the lower end of a detection tank device, a through hole cavity is arranged on the detection tank device, a counter electrode and a reference electrode of an electrochemical detection device are arranged in detection liquid at intervals, a working electrode of the electrochemical detection device is electrically connected with the lower end of the semiconductor chip, a specific position of the semiconductor chip with a field effect structure is irradiated by constant laser, in-situ photon-generated carriers are excited to generate, and meanwhile, the SWV or ACV function of an electrochemical workstation is utilized to modulate the external voltage of the semiconductor chip to influence the directional migration and diffusion process of the photon-generated carriers, so that in-situ photocurrent is detected in an external circuit, the detection of the pH value of a solution and in-situ detection and imaging of the surface impedance of the chip can be realized.
Description
Technical Field
The application belongs to photoelectrochemical sensing and imaging technologies, and particularly relates to a photoelectrochemical sensing system and method of light addressing square wave/alternating current volt-ampere.
Background
Square wave voltammetry (square wave voltammetry, SWV) is to superimpose a square wave voltage with a larger amplitude on a rapidly scanned stepped voltage, record the difference between the current at the positive half-cycle end of the square wave and the current at the negative half-cycle end of the square wave, well eliminate the charging current, and record the current-potential voltammogram in a very short time. Ac voltammetry (alternating current voltammetry, ACV) is to apply a dc potential to the working electrode which is slowly scanned over time, and to superimpose a sinusoidal ac component, measure the amplitude and the corresponding phase angle of the ac component of the current, and obtain a corresponding ac voltammogram. The two methods have the characteristics of multifunction, high sensitivity and high efficiency, and are widely applied to quantitative analysis and kinetic research of substances. However, the conventional SWV and ACV electroanalysis methods do not have spatial resolution, the whole information of the detected sample is reflected by the average electrode measurement result, the requirements of high flux, multi-site detection and sensing are difficult to meet, and two-dimensional imaging of the detected sample is also impossible.
Disclosure of Invention
The application provides an addressable square wave/alternating current volt-ampere electrochemical sensing and imaging method, which realizes sensing and detection of surface potential and system impedance with spatial resolution capability so as to overcome the defect that the conventional electrochemical detection technology lacks of spatial resolution capability.
In order to achieve the above purpose, the application adopts the following technical scheme:
an optical addressing square wave/alternating current volt-ampere electrochemical sensing system comprises a laser device, a semiconductor chip, a detection cell device, an electrochemical detection device, a displacement device and an optical imaging device; the semiconductor chip is fixed in detection cell device lower extreme, be equipped with the through-hole on the detection cell device and hold the chamber, the through-hole holds the intracavity and is used for placing the detection liquid, the detection liquid can be with semiconductor chip up end contact, electrochemical detection device's counter electrode and reference electrode interval are placed in the detection liquid, electrochemical detection device's working electrode and semiconductor chip lower extreme electricity are connected, laser device and optical imaging device set up in detection cell device upper end, optical imaging device's light source and laser device's laser can be through the through-hole hold the chamber and shine in semiconductor chip upper surface, semiconductor chip and detection cell device are fixed in on the displacement device.
Further, the electrochemical detection device comprises an electrochemical workstation, a counter electrode, a reference electrode and a working electrode, wherein the counter electrode, the reference electrode and the working electrode are connected with the electrochemical workstation, the electrode adopts a platinum wire, the reference electrode adopts an Ag/AgCl reference electrode, and the working electrode is connected with the semiconductor chip.
Further, the laser device comprises a laser controller, a laser, a collimating lens, a beam splitting prism and an amplifying objective lens, wherein the amplifying objective lens is arranged at the upper end of the detection pool device, the collimating lens is arranged at the laser emitting end of the laser, the beam splitting prism is arranged between the collimating lens and the amplifying objective lens, and the laser is connected to the laser controller.
Further, the optical imaging device comprises an LED illumination light source, a field lens and a CCD camera, wherein the CCD camera is connected with a computer, the computer is used for acquiring and storing images, the field lens is arranged on one side of the beam-splitting prism, and the field lens, the beam-splitting prism and the amplifying objective lens are arranged on the same straight line.
Further, the semiconductor chip adopts a pH-sensitive semiconductor chip or an impedance-sensitive semiconductor chip.
Further, the pH sensitive semiconductor chip comprises a sensitive layer, an insulating layer, a semiconductor layer and an ohmic contact layer which are sequentially stacked from top to bottom, the ohmic contact layer is electrically connected with a working electrode of the electrochemical detection device, the sensitive layer is in contact with electrolyte in the detection cell device, the impedance sensitive semiconductor chip comprises the insulating layer, the semiconductor layer and the ohmic contact layer which are sequentially stacked from top to bottom, the ohmic contact layer is electrically connected with the working electrode of the electrochemical detection device, and the insulating layer is in contact with the electrolyte in the detection cell device.
Further, the detection cell device comprises a detection cavity and an electric connection sheet, wherein the detection cavity is provided with a through hole cavity, the semiconductor chip is in sealing contact with the lower end face of the detection cavity, the electric connection sheet is arranged at the lower end of the semiconductor chip, and the electric connection sheet is electrically connected with the semiconductor chip.
An optically addressed square wave/alternating current voltammetric electrochemical imaging method comprising the steps of:
s1, fixing a detection cell device fixed with a pH sensitive semiconductor chip on a displacement device, and adding buffer salt electrolytes with different pH values into a through hole cavity of the detection cell device; placing a counter electrode and a reference electrode of an electrochemical detection device into electrolyte, and connecting a working electrode with an ohmic contact layer of a pH sensitive semiconductor chip;
s2, adjusting the displacement device to enable laser generated by the laser to irradiate the upper end of the pH sensitive semiconductor chip through the through hole cavity of the detection pool device, and enabling the laser focusing point to be located at 0.8-1.2cm of the semiconductor surface;
and S3, sequentially performing SWV and ACV electrochemical tests on solutions with different pH values by adopting an electrochemical workstation to obtain a dark/photocurrent-potential curve, thereby completing addressable square wave/alternating current volt-ampere electrochemical sensing detection.
An optically addressed square wave/alternating current voltammetric electrochemical sensing method comprising the steps of:
s1, fixing a detection cell device fixed with an impedance sensitive semiconductor chip on a displacement device, and adding electrolyte into the detection cell device; placing a counter electrode and a reference electrode of an electrochemical detection device into electrolyte, and connecting a working electrode with an ohmic contact layer of an impedance sensitive semiconductor chip through an electric connection sheet;
s2, adjusting the displacement device to enable laser generated by the laser to irradiate on the surface of the impedance sensitive semiconductor chip through the through hole cavity of the detection pool device, and enabling the laser focusing point to be located on the surface of the semiconductor chip;
s3, adopting an electrochemical workstation to sequentially perform electrochemical testing on the SWV and the ACV, and respectively obtaining I-V curves of the tested SWV and ACV;
s4, adjusting the displacement device, observing through an optical imaging system, enabling the semiconductor chip to perform two-dimensional scanning on a horizontal plane relative to laser by taking the photoetching pattern as the center, and taking the SWV photocurrent under the fixed potential of the corresponding coordinates, so as to obtain a photocurrent distribution image of the photoetching pattern, namely a photo-addressing square wave voltammetry electrochemical impedance diagram;
further, the displacement device is adjusted to enable the electric semiconductor chip to linearly move in a horizontal direction relative to the laser, SWV scanning is conducted on the edge of the photoetching pattern on the semiconductor chip, so that a current-position curve under a fixed potential is obtained, differential processing is conducted on the current-position curve, and the half-peak width is obtained, namely the space resolution of the optical addressing square wave voltammetry impedance imaging is obtained.
Compared with the prior art, the application has the following beneficial technical effects:
the application relates to an optical addressing square wave/alternating current volt-ampere electrochemical sensing system, which is characterized in that a semiconductor chip is fixed at the lower end of a detection pool device, a through hole cavity is arranged on the detection pool device, so that detection liquid can be contacted with the upper end surface of the semiconductor chip to form a detection space, a counter electrode and a reference electrode of an electrochemical detection device are placed in the detection liquid at intervals, a working electrode of the electrochemical detection device is electrically connected with the lower end of the semiconductor chip, a laser device is arranged at the upper end of the detection pool device, laser of the laser device can irradiate the upper surface of the semiconductor chip through the through hole cavity, the semiconductor chip and the detection pool device are fixed on a displacement device, the specific position of the chip is irradiated by the laser, and addressable detection of chip surface potential and system impedance and real-time acquisition of corresponding optical images can be realized based on SWV and ACV electric analysis means of an electrochemical workstation.
The application relates to a light addressing square wave/alternating current volt-ampere electrochemical sensing and imaging method, which adopts constant laser to irradiate a specific position of a semiconductor chip with a field effect structure to excite and generate in-situ photon-generated carriers, and simultaneously utilizes SWV or ACV functions of an electrochemical workstation to modulate the external voltage of the semiconductor chip to influence the directional migration and diffusion processes of the photon-generated carriers, thereby obtaining in-situ photocurrent through detection in an external circuit, realizing the detection of the pH value of a solution and the in-situ detection and imaging of the surface impedance of the chip.
Drawings
Fig. 1 is a schematic structural diagram of an embodiment of the present application.
Fig. 2 is a schematic diagram of a test cell device and a semiconductor chip mounting structure according to an embodiment of the application.
FIG. 3 is a graph of SWV current versus potential I-V for a pH sensitive semiconductor chip with and without illumination in an embodiment of the present application.
FIG. 4 is a graph showing the current-potential I-V curve of the pH sensitive semiconductor chip ACV under light and no light in the embodiment of the present application.
FIG. 5 is a graph of SWV potential scan of a pH sensitive semiconductor chip according to an embodiment of the present application; fig. 5a is a graph of optically addressed SWV in ph= 3,4,5,6,7,8,9.2 buffer solution, respectively, and fig. 5b is a graph of potential versus pH at-100 nA constant current.
Fig. 6 is a graph of ACV profile of potential scan of a pH sensitive semiconductor chip according to an embodiment of the present application, fig. 6a is a graph of ACV profile of optical addressing in ph= 3,4,5,6,7,8,9.2 buffer solution, respectively, and fig. 6b is a graph of potential versus pH at a constant current of 410 nA.
FIG. 7 is a graph of a scanned I-V plot of an impedance-sensitive semiconductor chip optically addressed SWV in areas with SU8 coverage and areas without SU8 in an embodiment of the application.
FIG. 8 is a graph of a scanned I-V curve for an optically addressed ACV of an impedance sensitive semiconductor chip in areas with SU8 coverage and areas without SU8 in an embodiment of the present application.
FIG. 9 is a two-dimensional scanning result of a focused laser on a SU8 pattern according to an embodiment of the application, and FIG. 9a is an optical image taken by an optical imaging system; FIG. 9b is a two-dimensional plot of photocurrent obtained by scanning SWV at a potential of-0.8V.
FIG. 10 is a graph of SWV current versus position (I-x) for a focused laser at the edge of the SU8 pattern for the example of the present application, FIG. 10a is a graph of SWV current versus position (I-x) for a potential of-0.8V; FIG. 10b is a result of evaluating spatial resolution based on SWV current-position (I-x) graphs.
Wherein, 1, a laser device; 2. a semiconductor chip; 3. a detection cell device; 4. an electrochemical detection device; 5. a displacement device; 6. a counter electrode; 7. a reference electrode; 8. a working electrode; 9. a sensitive layer; 10. an insulating layer; 11. a semiconductor layer; 12. an ohmic contact layer; 13. a detection cavity; 14. an electrical connection piece; 15. a seal ring; 16. a bolt group; 17. an electrochemical workstation; 18. an optical imaging device; 19. a laser controller; 20. a laser; 21. a collimating lens; 22. a beam-splitting prism; 23. a magnifying objective lens; 24. an LED illumination source; 25. a field lens; 26. a computer; 27. a CCD camera.
Detailed Description
The application is described in further detail below with reference to the attached drawing figures:
as shown in fig. 1, an optically addressed square wave/alternating current volt-ampere electrochemical sensing system comprises a laser device 1, a semiconductor chip 2, a detection cell device 3, an electrochemical detection device 4, a displacement device 5 and an optical imaging device 18; the semiconductor chip 2 is fixed in detection cell device 3 lower extreme, be equipped with the through-hole appearance chamber on the detection cell device 3, the through-hole holds the intracavity and is used for placing the detection liquid, detection liquid can be with semiconductor chip 2 up end contact, electrochemical detection device 4's counter electrode 6 and reference electrode 7 interval place in detection liquid, electrochemical detection device 4's working electrode 8 and semiconductor chip 2 lower extreme electricity are connected, laser device 1 and optical imaging device set up in detection cell device 3 upper end, optical imaging device's light source and laser device 1's laser can hold the chamber through the through-hole and shine in semiconductor chip 2 upper surface, laser device 1 and optical imaging device 2 form confocal system, semiconductor chip 2 and detection cell device 3 are fixed in on the displacement device 5.
The electrochemical detection device 4 comprises an electrochemical workstation 17, a counter electrode 6, a reference electrode 7 and a working electrode 8. The counter electrode, the reference electrode and the working electrode are connected with an electrochemical workstation and are used for electrochemical detection of SWV and ACV; the counter electrode adopts a platinum wire, the reference electrode adopts an Ag/AgCl reference electrode, and the working electrode is connected with the semiconductor chip.
The laser device 1 comprises a laser controller 19, a laser 20, a collimating lens 21, a beam splitting prism 22 and an amplifying objective lens 23, wherein the amplifying objective lens 23 is arranged at the upper end of the detection pool device 3, the collimating lens 21 is arranged at the laser emitting end of the laser 20, the beam splitting prism 22 is arranged between the collimating lens 21 and the amplifying objective lens 23, the laser is connected with the laser controller and generates laser with the wavelength of 405nm, the laser irradiates the upper surface of a semiconductor chip through the collimating lens 21, the beam splitting prism 22, the amplifying objective lens 23 and a through hole cavity, and the diameter of a light spot is about 10 mu m when focusing; the magnification of the magnifying objective lens 23 is 10 times.
The optical imaging device comprises an LED illumination light source 24, a field lens 25 and a CCD camera 27, wherein the CCD camera is connected with a computer 26, the computer 26 is used for acquiring and storing images, the field lens 25 is arranged on one side of the beam splitting prism 22, the field lens 25, the beam splitting prism 22 and the amplifying objective lens 23 are arranged on the same straight line, LED illumination light irradiates on the upper surface of the semiconductor chip through the through hole cavity, and reflected light passes through the amplifying objective lens 23, the beam splitting prism and the field lens to the CCD camera to acquire optical images.
The semiconductor chip 2 is a pH-sensitive semiconductor chip or an impedance-sensitive semiconductor chip; the pH sensitive semiconductor chip comprises a sensitive layer 9, an insulating layer 10, a semiconductor layer 11 and an ohmic contact layer 12 which are sequentially stacked from top to bottom, wherein the ohmic contact layer 12 is electrically connected with a working electrode 8 of the electrochemical detection device 4 to form good contact so as to conduct current, and the sensitive layer 9 is in contact with electrolyte in the detection cell device 3. The impedance sensitive semiconductor chip comprises an insulating layer 10, a semiconductor layer 11 and an ohmic contact layer 12 which are sequentially stacked from top to bottom, wherein the ohmic contact layer 12 is electrically connected with a working electrode 8 of the electrochemical detection device 4, the insulating layer 10 is in contact with electrolyte in the detection cell device 3, and SU8 photoresist patterns are prepared on the surface of the insulating layer.
As shown in fig. 2, the detection cell device 3 includes a detection cavity 13 and an electrical connection piece 14, the detection cavity 13 is provided with a through cavity, the semiconductor chip 2 is contacted with the lower end surface of the detection cavity 13, the electrical connection piece 14 is arranged at the lower end of the semiconductor chip 2, and the electrical connection piece 14 is electrically connected with the semiconductor chip 2; the semiconductor chip 2 is fixedly connected with the detection cavity 13 through the bolt group 16, and the semiconductor chip 2 is clamped between the electric connecting sheet 14 and the detection cavity 13; specifically, the ohmic contact layer 12 of the semiconductor chip 2 is in contact with the electrical connection pad 14.
A sealing ring 15 is arranged between the semiconductor chip 2 and the lower end surface of the detection cavity 13, and the sealing ring adopts a silicon rubber sealing ring. The detection cavity 13 is made of organic glass. The electrical connection pads 14 are made of aluminum.
The pH sensitive semiconductor chip is used for testing the pH of a solution, and the specific structure of the pH sensitive semiconductor chip is as follows: (50 nm Si) 3 N 4 ) Insulating layer (100 nm SiO) 2 ) A semiconductor layer (p-Si, 100, 1-10. OMEGA cm) -ohmic contact (30 nm Cr,150nm Au), wherein Si 3 N 4 And ohmic contact are prepared by using a magnetron sputtering method, and SiO 2 Is grown by a thermal oxidation method.
The impedance sensitive semiconductor chip is used for impedance imaging, and the specific structure of the impedance sensitive semiconductor chip adopted by the application is as follows: insulating layer self-assembled machine monomolecular film (self-assembled organic monolayers, SAMs) -semiconductor layer (p-Si, 100,1-10 Ω cm) -ohmic contact (30 nm cr,150nm Au), wherein SAMs is an undecylenic acid film grown using a thermally induced silylation method, has a thickness of 1nm, and can significantly increase the impedance sensitivity of the system compared with the conventional silicon oxide insulating layer. In electrochemical detection, the sensitive layer of the semiconductor chip faces upwards, the sensitive layer is used as a working electrode to be contacted with electrolyte, and SU8 2005 photoresist patterns with the thickness of about 5 mu m are prepared on the surface of the insulating layer.
The displacement device 5 adopts a three-dimensional electric displacement system, and the detection pool device 3 is fixed on an XY plane of the displacement system.
An optically addressed square wave/alternating current voltammetric electrochemical sensing method comprising the steps of:
s1, cleaning and assembling a semiconductor chip:
step 1, ultrasonically cleaning the semiconductor chip in acetone, isopropanol and pure water for 15min respectively, and blow-drying the semiconductor chip for later use by a nitrogen gun.
Step 2, placing the cleaned semiconductor chip sensitive layer upwards on an aluminum sheet, placing an organic glass cavity on the semiconductor chip to enable the through hole cavity to be positioned above the chip, fixing the semiconductor chip 2 and the detection cavity 13 by utilizing the bolt group 16, and sealing the semiconductor chip 2 and the detection cavity 13 through the sealing ring 15;
and 3, fixing the detection pool device 3 assembled with the semiconductor chip on the displacement device 5, and adjusting the displacement device to enable the laser generated by the laser device 1 to irradiate the semiconductor chip.
S2, photocurrent response test:
the Z-direction height of the displacement device 5 is regulated, so that a semiconductor chip on the detection pool device 3 is positioned at a position of 0.8-1.2cm of a laser focus position generated by the laser device 1, namely, in a non-focusing state, and the laser is turned off or turned on.
A pH sensitive semiconductor chip is connected with a working electrode, a silver/silver chloride reference electrode is used as a reference electrode, and a platinum wire is used as a counter electrode to form a three-electrode system; the voltage sweep range of the SWV is: 0.4 to-1.2V, the amplitude is 0.05V, and the scanning frequency is 1KHz; the voltage sweep range of ACV is: 0.1 to-1.5V, the amplitude is 0.02V, and the scanning frequency is 200Hz.
S3, pH sensitivity test:
the Z-direction height of the displacement device 5 is regulated, so that the semiconductor chip on the detection pool device 3 is positioned at the position of 0.8-1.2cm of the focal position of the laser generated by the laser device 1, namely in a non-focusing state, and the sensitivity of the pH sensitive semiconductor chip to the pH of the solution is inspected. 2ml of different buffers (pH: 3-9.2) of 0.1M NaCl were added to the detection chamber, respectively, and the I-V curves corresponding to SWV and ACV were tested accordingly. The voltage sweep range of the SWV is: 0.4 to-1.2V, the amplitude is 0.05V, and the scanning frequency is 1KHz; the voltage sweep range of ACV is: 0.1 to-1.5V, the amplitude is 0.02V, and the scanning frequency is 200Hz.
S4, impedance in-situ detection and imaging:
and step 1, adjusting the Z-direction height of the displacement device 5 to focus laser on the surface of the impedance sensitive semiconductor chip, and examining the impedance in-situ detection function of the optical addressing square wave/alternating current voltammetry. Specifically, SU8 2005 patterns were prepared on the surface of the semiconductor chip using standard photolithography, the photoresist thickness was 5 μm, and the patterns were squares with a side length of 100 μm. The position of the impedance sensitive semiconductor chip relative to the laser is adjusted by the displacement device 5, so that the laser just irradiates the photoresist covered or non-photoresist covered area, and SWV and ACV I-V curves are respectively tested. Wherein the voltage scanning range of the SWV is-0.4 to-0.8V, the amplitude is 0.05V, and the scanning frequency is 100Hz; the ACV potential scanning range is-0.3 to-0.55V, the potential amplitude is 0.1V, and the scanning frequency is 10Hz.
And 2, based on the SWV I-V curve result obtained in the step 1, carrying out two-dimensional scanning on the SU8 pattern at the potential of-0.8V to obtain a SWV photoelectric diagram, and comparing the SWV photoelectric diagram with an optical diagram shot by an optical imaging system. The pattern was subjected to SWV testing (-0.78 to-0.8V, amplitude 0.05V, scanning frequency 100 Hz) by two-dimensional scanning (step size: 4 μm, dead time: 2.3s, scanning range: 200 μm. Times.200 μm) in x and y directions by a displacement device, i.e., the SWV current magnitude at-0.8V was collected every time the displacement device was moved to a point, thereby obtaining a photocurrent two-dimensional image.
SU8 2005 patterns were prepared on the surface of the semiconductor chip using standard photolithography techniques, with a photoresist thickness of 5 um and a square with a side length of 100 um.
Step 3) detecting the resolution size of the optically addressed SWV impedance imaging at-0.8V potential: and (3) performing SWV scanning (-0.78 to-0.8V, amplitude 0.05V and scanning frequency 100 Hz) on the edge of the pattern through linear movement (step length: 2 mu m and dead time: 2.3 s) of the displacement device in the x direction, namely collecting the SWV current of a point at-0.8V when the displacement device moves to the point, so as to obtain a photocurrent-position (I-x) curve, and performing differential processing on the curve to obtain the half-peak width, namely the space resolution of the optically addressed SWV impedance imaging.
For the above-described applications for surface potential sensing and impedance imaging, the detection results are as follows:
when the potential scanning range is 0.4 to-1.2V, the potential amplitude is 0.05V, and the scanning frequency is 1KHz, the SWV I-V curve of the pH sensitive semiconductor chip is shown in FIG. 3, and as can be seen from FIG. 3, the photocurrent has an "s" curve variation trend along with the potential: when the potential is relatively positive (0.4 to-0.1V), SWV current is relatively low and change is relatively small, and the accumulated layer corresponds to the specific I-V curve of the field effect structure; along with the continuous decrease of the potential, the absolute value of the photocurrent is gradually increased and corresponds to the depletion layer of the field effect structure; the current reaches saturation at the potential of-1.2V, corresponding to the inversion layer of the field effect structure.
When the potential scanning range is 0.1 to-1.5V, the amplitude is 0.02V, and the scanning frequency is 200Hz, the ACV photocurrent curve of the pH sensitive semiconductor chip is shown in FIG. 4. As can be seen from fig. 4, the photocurrent also has a "s" curve trend with the potential: when the potential is 0.1 to-0.1V, the current is relatively low and the change is small; with the continuous decrease of the potential, the photocurrent gradually increases until about-1.2V reaches saturation.
When the potential scanning range is 0.4 to-1.2V, the potential amplitude is 0.05V, and the scanning frequency is 1KHz, the optical addressing SWV curve of the pH sensitive semiconductor chip tested in different pH solutions is shown in FIG. 5 a; the I-V curve gradually shifts to the negative potential direction along with the increase of the pH value of the solution; as shown in FIG. 5b, the pH sensitivity was 55.9mV/pH at a constant current of-100 nA.
When the potential scanning range is 0.3 to-0.8V, the amplitude is 0.02V, and the scanning frequency is 200Hz, the optical addressing ACV curves of the pH sensitive semiconductor chip tested in different pH solutions are shown in FIG. 6 a. As the pH of the solution increases, the I-V curve also gradually shifts towards a negative potential. As shown in FIG. 6b, the pH sensitivity was 46.7mV/pH at a constant current of 405 nA.
When the potential scanning range is-0.4 to-0.8V, the potential amplitude is 0.05V, and the scanning frequency is 100Hz, the SWV curve of the focused laser scanning the covered area and the uncovered area of the SU8 photoresist on the impedance sensitive semiconductor chip is shown in figure 7. Since SU8 photoresist increases the impedance of the chip surface in situ, the absolute value of photocurrent at the chip surface with SU8 coverage is significantly lower than that at the locations without SU8 in the current saturation region, i.e., inversion layer.
When the potential scanning range is-0.3 to-0.55V, the potential amplitude is 0.1V, and the scanning frequency is 10Hz, the ACV curves of the area covered by the SU8 photoresist and the area not covered by the SU8 photoresist on the impedance sensitive semiconductor chip are shown in fig. 8, and the impedance of the chip surface is increased in situ by the SU8 photoresist, so that the photocurrent of the part covered by the SU8 on the chip surface is obviously reduced compared with that of the part not covered by the SU8 on the inversion layer.
An optical image was taken using an optical imaging system centered on SU8 pattern as shown in fig. 9 a. Taking SU8 pattern as center, carrying out two-dimensional scanning in xy direction (step length: 4 μm, dead time: 2.3s, scanning range: 200 μm×200 μm) by displacement device, and simultaneously carrying out SWV test (-0.78 to-0.8V, amplitude 0.05V, scanning frequency 100 Hz), and obtaining SWV photocurrent two-dimensional image under-0.8V corresponding position coordinate as shown in figure 9 b. Since SU8 photoresist increases the impedance of the chip surface in situ, the photocurrent in the area covered by the photoresist is significantly lower. The SWV photocurrent image corresponds well to the optical image.
By linear movement (step length: 2 μm, dead time: 2.5s, scanning range: 90 μm) in the x-direction of the displacement device, the impedance-sensitive semiconductor chip SU8 is scanned for SWV-0.78 to-0.8V at the pattern edge, the amplitude is 0.05V, the scanning frequency is 100Hz, the SWV current at the corresponding position coordinate-0.8V is obtained, the current-position I-x curve is shown in fig. 9a, and the curve obtained by differentiating the I-x curve is shown in fig. 9 b. As can be seen from fig. 9a, the absolute value of the photocurrent increases dramatically as the laser moves from SU8 coverage to SU 8-free areas, as SU8 increases the in-situ impedance of its coverage area. The spatial resolution of the optically addressed SWV was found to be about 5.2 μm by differentiating the peak width at half.
The application provides an addressable photoelectrochemical detection method, which uses a beam of constant laser to irradiate a semiconductor field effect structure to generate local photogenerated carriers, and simultaneously utilizes the SWV or ACV function of an electrochemical workstation to modulate the external voltage of a semiconductor chip to detect and obtain photocurrent. The results indicate that when silicon nitride is used as the sensitive layer, detection of the pH of the solution can be achieved. In addition, SAMs-insulation-based semiconductor chips can be used for in-situ detection and imaging of chip surface impedance. Compared with the traditional electrochemical analysis method, the optical addressing SWV/ACV provided by the application has a certain spatial resolution capability, and provides a solution for high-flux and multi-site electrochemical detection.
Claims (8)
1. An optical addressing square wave/alternating current volt-ampere electrochemical sensing system is characterized by comprising a laser device (1), a semiconductor chip (2), a detection cell device (3), an electrochemical detection device (4), a displacement device (5) and an optical imaging device (18); the semiconductor chip (2) is fixed at the lower end of the detection cell device (3), a through hole containing cavity is arranged on the detection cell device (3), detection liquid is used for being placed in the through hole containing cavity, the detection liquid can be in contact with the upper end face of the semiconductor chip (2), a counter electrode (6) and a reference electrode (7) of the electrochemical detection device (4) are placed in the detection liquid at intervals, a working electrode (8) of the electrochemical detection device (4) is electrically connected with the lower end of the semiconductor chip (2), a laser device (1) and an optical imaging device (18) are arranged at the upper end of the detection cell device (3), a light source of the optical imaging device (18) and laser light of the laser device (1) can be irradiated on the upper surface of the semiconductor chip (2) through the through hole containing cavity, the semiconductor chip (2) and the detection cell device (3) are fixed on the displacement device (5), the electrochemical detection device (4) comprises an electrochemical working station, a counter electrode, a reference electrode and a working electrode are connected with the electrochemical working station, the reference electrode and the working electrode are all connected with the electrochemical working station, the electrode adopts platinum wire, the reference electrode adopts AgAg/Cl reference electrode, the working electrode is connected with the semiconductor chip, a light source (1), a light source of the optical imaging device (18) and a laser lens (20) and a laser amplifying device (20) are arranged on the laser amplification device (23) and a laser amplifying device (23) on the laser amplification device) through the laser amplification device (20), the collimating lens (21) is arranged at the laser emitting end of the laser (20), the beam splitting prism (22) is arranged between the collimating lens (21) and the amplifying objective lens (23), and the laser is connected to the laser controller.
2. An optically addressed square wave/alternating current voltammetric electrochemical sensing system according to claim 1, characterized in that the optical imaging means comprises an LED illumination source (24), a field lens (25) and a CCD camera, the CCD camera being connected to a computer (26), the computer (26) being adapted to acquire and store the image, the field lens (25) being arranged on one side of the beam splitting prism (22), the field lens (25), the beam splitting prism (22) and the magnifying objective (23) being in a straight line.
3. An optically addressed square wave/alternating current volt-ampere electrochemical sensing system according to claim 1, characterized in that the semiconductor chip (2) is a pH sensitive semiconductor chip or an impedance sensitive semiconductor chip.
4. A light-addressed square wave/alternating current voltammetric electrochemical sensing system according to claim 3, characterized in that the pH-sensitive semiconductor chip comprises a sensitive layer (9), an insulating layer (10), a semiconductor layer (11) and an ohmic contact layer (12) stacked in sequence from top to bottom, the ohmic contact layer (12) being electrically connected with the working electrode (8) of the electrochemical detection means (4), the sensitive layer (9) being in contact with the electrolyte in the detection cell means (3), the impedance-sensitive semiconductor chip comprising an insulating layer (10), a semiconductor layer (11) and an ohmic contact layer (12) stacked in sequence from top to bottom, the ohmic contact layer (12) being electrically connected with the working electrode (8) of the electrochemical detection means (4), the insulating layer (10) being in contact with the electrolyte in the detection cell means (3).
5. The light-addressable square wave/alternating current volt-ampere electrochemical sensing system according to claim 1, wherein the detection cell device (3) comprises a detection cavity (13) and an electric connection sheet (14), a through hole cavity is arranged on the detection cavity (13), the semiconductor chip (2) is in sealing contact with the lower end face of the detection cavity (13), the electric connection sheet (14) is arranged at the lower end of the semiconductor chip (2), and the electric connection sheet (14) is electrically connected with the semiconductor chip (2).
6. A method of optically addressed square wave/ac voltammetric electrochemical testing based on the optically addressed square wave/ac voltammetric electrochemical sensing system of claim 3, comprising the steps of:
s1, fixing a detection cell device fixed with a pH sensitive semiconductor chip on a displacement device, and adding buffer salt electrolytes with different pH values into a through hole cavity of the detection cell device; placing a counter electrode and a reference electrode of an electrochemical detection device into electrolyte, and connecting a working electrode with an ohmic contact layer of a pH sensitive semiconductor chip;
s2, adjusting the displacement device to enable laser generated by the laser to irradiate the upper end of the pH sensitive semiconductor chip through the through hole cavity of the detection pool device, and enabling the laser focusing point to be located at 0.8-1.2cm of the semiconductor surface;
and S3, sequentially performing SWV and ACV electrochemical tests on solutions with different pH values by adopting an electrochemical workstation to obtain a dark/photocurrent-potential curve, thereby completing addressing square wave/alternating current volt-ampere electrochemical sensing detection.
7. A method of optically addressed square wave/ac voltammetric electrochemical imaging based on the optically addressed square wave/ac voltammetric electrochemical sensing system of claim 3, comprising the steps of:
s1, fixing a detection cell device fixed with an impedance sensitive semiconductor chip on a displacement device, and adding electrolyte into the detection cell device; placing a counter electrode and a reference electrode of an electrochemical detection device into electrolyte, and connecting a working electrode with an ohmic contact layer of an impedance sensitive semiconductor chip through an electric connection sheet;
s2, adjusting the displacement device to enable laser generated by the laser to irradiate on the surface of the impedance sensitive semiconductor chip through the through hole cavity of the detection pool device, and enabling the laser focusing point to be located on the surface of the semiconductor chip;
s3, adopting an electrochemical workstation to sequentially perform electrochemical testing on the SWV and the ACV, and respectively obtaining I-V curves of the tested SWV and ACV;
s4, adjusting the displacement device, observing through an optical imaging system, enabling the semiconductor chip to perform two-dimensional scanning on a horizontal plane relative to laser by taking the photoetching pattern as the center, and taking the SWV photocurrent under the fixed potential of the corresponding coordinates, so as to obtain a photocurrent distribution image of the photoetching pattern, namely a photo-addressing square wave voltammetry electrochemical impedance diagram.
8. The method of electro-chemical imaging of square wave/ac voltammetry of claim 7, wherein the displacement device is adjusted to make the semiconductor chip move linearly in horizontal direction relative to the laser, and SWV scanning is performed on the edge of the lithography pattern on the semiconductor chip, so as to obtain a current-position curve under a fixed potential, and differential processing is performed on the current-position curve, so as to obtain the half-peak width, namely the size of the spatial resolution of the electro-chemical imaging of square wave voltammetry of the light addressing.
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