CN108318543B - Heavy metal ion sensor based on graphene material and operation method thereof - Google Patents
Heavy metal ion sensor based on graphene material and operation method thereof Download PDFInfo
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Abstract
The invention discloses a heavy metal ion sensor based on a graphene material, which comprises a first microelectrode array, a second microelectrode array, an upper cover plate, a lower cover plate and a multistage microfluidic cavity, wherein a microelectrode gap is formed between the first microelectrode array and the second microelectrode array, the multistage microfluidic cavity is arranged on the upper surfaces of the first microelectrode array and the second microelectrode array, a first lead-out flat cable and a second lead-out flat cable are clamped between the upper cover plate and the first microelectrode array and between the upper cover plate and the second microelectrode array, and a graphene microchip aggregate is tightly combined with the first microelectrode array and the second microelectrode array at the microelectrode gap position respectively; the invention has the characteristics of high sensitivity, less sample consumption, high detection speed, simple and easy replacement of components, convenient arrangement of lead-out flat cables, simple operation steps, high detection continuity and wide application range.
Description
Technical Field
The invention belongs to the field of micro-nano sensing, and particularly relates to a heavy metal ion sensor based on a graphene material and an operation method thereof.
Background
The metals are classified into heavy metals and light metals according to their density, usually greater than 5g/cm3The metals of (a) are called heavy metals, such as: about 45 kinds of gold, silver, copper, lead, zinc, nickel, cobalt, chromium, mercury, cadmium, etc. With the continuous acceleration of the industrialization progress, more and more heavy metal particles such as lead, cadmium, mercury, copper, zinc, vanadium and the like are discharged into water, so that the aquatic animals and plants are harmed, and the heavy metal particles enter into the biologic chain circulation through the enrichment effect, so that the whole ecological environment faces serious threats. Among them, there are 5 kinds which are the most harmful to human body: such as lead, mercury, chromium, arsenic, cadmium, etc. These heavy metals cannot be decomposed in water and combine with other toxins in the water to produce more toxic organic compounds. Other hazards to the human body are: aluminum, cobalt, vanadium, antimony, manganese, tin, thallium, and the like. The harm of heavy metals to human body is common: lead damages brain cells of human, causes carcinogenesis and mutation, etc.; mercury directly sinks into the liver after being eaten, and has great damage to the brain nerve and vision. The natural water contains 0.01 mg of mercury per liter of water and is strongly poisoned; chromium causes numbness of limbs and mental disorders; cadmium can cause hypertension, cardiovascular and cerebrovascular diseases, destroy bone calcium and cause renal dysfunction; when more aluminum is accumulated, the intelligence of children is low, the memory of middle-aged and elderly people is reduced, and the dementia is caused. The detection of the metal substance is generally performed by: ultraviolet spectrophotometry (UV), Atomic Absorption Spectroscopy (AAS), Atomic Fluorescence Spectroscopy (AFS), Inductively Coupled Plasma (ICP), X fluorescence spectroscopy (XRF), inductively coupled plasma mass spectroscopy (ICP-MS). Although the above-described methods can achieve detection of metal ions, detection at ultra-low concentrations (ion concentration) is possibleLess than 1nM), to handle sudden contaminant leakage events, with very small sample volumes (less than 10 microliters), or with continuous monitoring of an area, requires the use of ultra-sensitive, rapid, and efficient detection tools. Therefore, it is of great significance to design and manufacture a metal ion ultrasensitive detection micro device capable of meeting the above requirements.
Graphene is a monolayer sp of2The two-dimensional carbon nanomaterial which is formed by closely stacking hybridized carbon atoms and has a hexagonal honeycomb lattice structure is ultrathin (the thickness of a single layer of carbon atoms), has large specific surface area, high conductivity, room-temperature electron mobility and excellent mechanical properties, has important application prospects in the aspects of materials science, micro-nano processing, energy, biomedicine, drug delivery and the like, and is considered to be a revolutionary material in the future. Graphene also has the characteristics of wide electrochemical window, good electrochemical stability and small charge transfer resistance, and the attractive property of graphene makes it an ideal material for basic research and potential applications, such as circuits, chemical and biological sensors, composite materials and the like.
Reducing graphene oxide provides a method for mass production of Reduced Graphene Oxide (RGO), which can replace the mechanical exfoliation method to some extent. Due to the fact that the material is easy to process, low in synthesis cost, good in mechanical property and high in flexibility, the reduced graphene oxide sheet becomes a good candidate material for manufacturing an electric circuit. In addition, RGO is very sensitive to the response of the external environment. Therefore, the application of RGO in micro-environment sensing is of positive significance by utilizing the acute reaction of RGO to the external environment and converting the reaction into the change of electrical characteristics through engineering technology.
RGO is prepared by chemical reduction of graphene oxide, which can be dispersed in water or ethanol solution with added surfactant, and graphene-based sheet circuits can be prepared by dropping RGO suspension randomly on a pre-fabricated electrode. The method for preparing some microcircuit structures by using the dripping suspension liquid has the advantages of simple operation, but low controllability and is not suitable for manufacturing microcircuits with high requirement on the assembly precision of internal components.
At present, in the prior art, the detection effect of the ultra-low concentration less than 1nM is poor or the cost is high in the heavy metal ion or substance detection process; a table-top type expensive instrument is required to be used; inaccurate detection under the condition of extremely small sample amount.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides a graphene material-based metal ion sensor and an operation method thereof, wherein the graphene material-based metal ion sensor is used for adsorbing various metal ions by utilizing the defects of incompletely reduced graphene oxide, so that the electron transmission in a graphene microchip is influenced, and then the influence is converted into the current signal variation in a sensor device.
The technical problem to be solved by the invention is realized by the following technical scheme:
a heavy metal ion sensor based on a graphene material comprises a first microelectrode array, a second microelectrode array, an upper cover plate, a lower cover plate and a multistage microfluidic cavity, the first microelectrode array and the second microelectrode array are both arranged between the upper cover plate and the lower cover plate, and are positioned on the same plane, a microelectrode gap is left between the first microelectrode array and the second microelectrode array, the bottom of the multistage micro-fluid cavity spans and is arranged on the upper surfaces of the first microelectrode array and the second microelectrode array, and the microelectrode gap and the graphene microchip aggregate are exposed, the upper cover sheet and the first microelectrode array clamp a first lead-out flat cable, the upper cover plate and the second microelectrode array clamp a second lead-out flat cable, and the graphene microchip aggregate is tightly combined with the first microelectrode array and the second microelectrode array at the microelectrode gap respectively.
It should be noted that, the bottom of the microfluidic cavity described in the above technical solution is a position where the ion sample solution directly and the reduced graphene oxide material perform a physicochemical action.
As a further improved technical scheme of the invention, a glass substrate is clamped between the first microelectrode array, the second microelectrode array and the lower cover plate.
As a further improved technical scheme of the invention, the upper cover plate and the lower cover plate are clamped and fixed by fastening screws, and the number of the fastening screws is 4.
As a further improved technical scheme of the invention, the first microelectrode array and the second microelectrode array both adopt the same strip-shaped microelectrodes, and the strip-shaped microelectrodes of the first microelectrode array and the strip-shaped microelectrodes of the second microelectrode array are staggered and arranged oppositely in parallel.
As a further improved technical scheme of the invention, the first microelectrode array is composed of one or more first microelectrodes which are parallel to each other and have circular arc parts, the second microelectrode array is composed of one or more second microelectrodes which are parallel to each other and have circular disc parts, the circular disc parts of the second microelectrodes are correspondingly wrapped with the circular arc parts of the first microelectrodes, and each group of the first microelectrodes and the second microelectrodes are arranged on the same straight line.
It should be noted that, with the above improved technical solution, each microelectrode can apply an excitation electrical signal individually or in groups; the first microelectrode array and the second microelectrode array are easy to generate a strong electric field between the edges and corners of the opposite electrodes, so that the graphene nanoplatelets are gathered at the gaps of the opposite edges and corners of the opposite electrodes to form graphene nanoplatelet aggregates. For another example, when the circular arc part of the first microelectrode is used for wrapping the disc part of the second microelectrode in the central region, the graphene microchip is gathered in the gap region of the two microelectrodes under the action of dielectrophoresis force to form an aggregate, so that the gathering region of the graphene microchip corresponding to a single pair of electrodes is further increased, and the utilization rate of the single electrode is improved. In practical operation, it is not better to have a larger amount of graphene sheets aggregated at a single electrode, because too much graphene sheet aggregation at the electrode gap would make the current of reduced graphene oxide micro-sheet aggregates too large, and it is likely that the current would be overwhelmed by a large current base due to a low concentration of ions, which is not favorable for measurement. Therefore, the shape and size of the tail end of the electrode are adjusted according to specific measurement requirements and current base range, the width and the interval of each electrode in the strip microelectrode array are adjusted, or the included radian of the wrapped electrode is increased or decreased to adapt to the requirements.
As a further improved technical scheme of the invention, the multistage micro-fluid cavity is formed by overlapping a plurality of coaxial hollow cylinders with equal outer diameters, the inner diameters of the hollow cylinders are sequentially reduced from the top to the bottom of the multistage micro-fluid cavity, the center of the bottom of the multistage micro-fluid cavity is over against the center of a micro-electrode gap, and the distance between the micro-electrode gaps is not less than 1.5 times of the distance between the micro-electrodes.
It should be noted that, in the above further improved technical solution, the multistage microfluidic cavity is mainly constructed in consideration of both reducing the contact area between the sample solution and the bottom surface microelectrode array as much as possible, and facilitating the use of a macro tool, such as a pipette, by an operator to add a sample to the device. The contact area between the sample solution and the bottom surface microelectrode array is reduced so that the current in the sample solution passes through the reduced graphene oxide microchip aggregates among microelectrode gaps as much as possible, and less passes through the ion solution which is a conductive path. If the current passing through the path of the ionic solution is relatively too large, the accuracy of detecting the ion concentration by the reduced graphene oxide microchip aggregates among the microelectrode gaps is greatly influenced, even the current signal passing through the reduced graphene oxide microchip aggregates among the microelectrode gaps is influenced, so that the magnitude of the current signal obtained when the ionic solution with different concentrations is detected is not in proportion to the concentration any more, and the sensor is finally caused to work abnormally; the multi-stage micro-fluid cavity has larger capacity and is also beneficial to realizing the detection of continuous concentration, namely, a sample with low solubility can be detected firstly, after the current signal is detected for measurement, the same ion solution sample with high concentration is directly added, and after the current signal corresponding to the sample is detected, the same ion solution sample with higher concentration is added into the micro-fluid cavity; each hollow cylinder can be used as a measurement mark of the amount of the sample solution, a prompt effect is provided for measuring personnel, the problem of inaccurate injection and measurement of the amount of the sample during measurement is greatly reduced, and the magnitude relation of the concentrations is verified if the obtained current signal changes monotonously step by step.
As a further improved technical scheme of the invention, the material of the multistage microfluidic cavity is polydimethylsiloxane, organic glass or an off-stoichiometrically thio-ene polymer.
As a further improved technical scheme of the invention, the inner surface of the multistage micro-fluid cavity is coated with polyethylene glycol liquid with the molecular weight range of 200-400.
It should be noted that, the technical solution of the above improvement is to use polyethylene glycol liquid with molecular weight range of 200-400 to perform hydrophilization treatment on the multi-stage microfluidic cavity.
An operation method of a heavy metal ion sensor based on a graphene material comprises the following specific steps:
step one, placing the multi-stage microfluid cavity with the inner wall coated with polyethylene glycol liquid with the molecular weight range of 200-400 in an oven for heating and drying;
mounting the multistage micro-fluid cavity dried in the first step on the heavy metal ion sensor based on the graphene material, and connecting the heavy metal ion sensor based on the graphene material with a conventional electrochemical workstation;
thirdly, on the basis of the second step, applying a 1-3V sinusoidal voltage signal between the first lead-out flat cable and the second lead-out flat cable, adjusting the signal frequency to 1M-3MHz, controlling and moving the partially reduced graphene oxide micro-slabs to a microelectrode gap of the first microelectrode array and the first microelectrode array by utilizing a positive dielectrophoresis technology to form a graphene micro-slab aggregate, and simultaneously enabling the graphene micro-slab aggregate to reach a set density through microscopic observation;
step four: on the basis of the third step, 5-100 mu L of metal ion solution to be detected is dripped into the multistage micro-fluid cavity;
step five: on the basis of the fourth step, testing the conductivity of the graphene microchip aggregate after adsorbing the metal ions, and generating a current mutation and a volt-ampere characteristic curve under constant voltage through a computer connected with the electrochemical workstation;
step six: recording the current mutation and the volt-ampere characteristic curve obtained in the fifth step into a knowledge base, and performing comparative analysis according to the relative change of the conductivity of the graphene microchip aggregate after metal ions are adsorbed, so as to identify the concentration or the type of the current sample;
and seventhly, repeating the fourth step to the sixth step when the sample with the next concentration or the next metal ion is measured continuously.
As a further improved technical scheme of the invention, the temperature of the oven heating and drying process in the step I is 60-70 degrees, and the time duration is 1 h.
The technical scheme includes that a specific micro-detection circuit is formed by assembling a microelectrode array with a specific pattern structure and a graphene microchip, and then various metal ions are adsorbed by using the defects of incompletely reduced graphene oxide, so that the electron transmission in the graphene microchip or graphene microchip aggregates is influenced, and the current signal in the detection microcircuit is rapidly and obviously changed; by measuring the change curve of the current along with the voltage, different variation quantities of the current in the sensing chip loop caused by metal ion solutions with different concentrations can be obtained, and sensing and analysis of different ions and different concentrations of the ions are realized. Also, directional assembly of graphene sheets at predetermined positions is necessary. Dielectrophoresis is a controllable assembly technique for the internal elements of nano-electronic devices, which can exert a certain dielectrophoresis force on a polarized object under the action of a non-uniform electric field. Dielectrophoresis provides a simple, scalable, low-cost method to locate graphene sheets. Therefore, the method for assembling the micro-nano elements by utilizing the dielectrophoresis technology to construct the corresponding sensor device is a technical method with great application value. Compared with one-dimensional sensing materials such as nanowires, nanotubes, nanobelts, and the like, the two-dimensional graphene sheet for detection has unique advantages because it has an extremely high specific surface area, uniform functional groups, high charge mobility, and carrier concentration. Due to the direct exposure of the surface to the environment, the electrical properties of graphene sheets are highly sensitive to external interference, such as the amount of charge that flows through the graphene material is likely to change significantly if RGO is able to adsorb to the corresponding protein molecule, peptide chain, other macromolecule, or ion.
The invention has the beneficial effects that:
the metal ion sensing device based on the graphene material can (1) complete the detection of metal ion concentration less than 1nM, and has high sensitivity; (2) the minimum sample volume required during detection only needs 5-10 mu L, and the consumed sample amount is small; (3) the detection time can be guaranteed within 2 seconds each time, and the detection speed is very high; (4) the device is detachable, the assembly is easy to replace, and the lead-out flat cable is convenient to arrange; (5) the operation steps are simple, the accuracy is high, and the detection continuity degree is high; (6) the application range is wide, and besides the detection of metal ions, the micro-fluidic heavy metal detector can be made into a portable micro-fluidic heavy metal detector for water environment sites and detection occasions of sudden pollutant changes.
Drawings
Fig. 1 is a front view of a structure of a metal ion sensor based on graphene material according to the present invention;
fig. 2 is a structural top view of a metal ion sensor based on graphene material according to the present invention;
FIG. 3 is a schematic diagram showing the shape of a strip-shaped microelectrode array in a metal ion sensing device based on graphene materials in example 1 of the present invention;
fig. 4 is a schematic view of a shape of an arc-wrapped micro-electrode array in a metal ion sensor device based on a graphene material according to embodiment 2 of the present invention;
fig. 5 is a schematic view of an operation method of the graphene material-based metal ion sensor device according to the present invention;
description of reference numerals: 1. a lower cover plate; 2. an upper cover plate; 3. fastening screws; 4. a multi-stage microfluidic cavity; 51. a first array of microelectrodes; 52. a second array of microelectrodes; 61. a first lead-out flat cable; 62. a second lead-out flat cable; 7. a glass substrate; 8. a microelectrode spacing; 41. a first hollow cylinder; 42. a second hollow cylinder 81 and a graphene microchip aggregate; 31. fastening a first screw; 32. a second fastening screw; 33. fastening a screw III; 34. fastening a screw II; 511. a first strip microelectrode; 512. a second strip microelectrode; 513. a third strip microelectrode; 514. a strip microelectrode is IV; 521. a fifth strip microelectrode; 522. sixthly, a strip microelectrode; 523. a strip microelectrode seventh; 811. a first graphene microchip; 515. a first microelectrode; 516. a second first microelectrode; 517. a third first microelectrode; 524. the first second microelectrode; 525. a second microelectrode; 526. a third second microelectrode; 812. and a second graphene microchip.
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
Example 1
As shown in figure 1, the heavy metal ion sensor based on the graphene material comprises a first microelectrode array 51, a second microelectrode array 52, an upper cover plate 2, a lower cover plate 1 and a multistage microfluidic cavity 4, wherein the first microelectrode array 51 and the second microelectrode array 52 are arranged between the upper cover plate 2 and the lower cover plate 1 and are positioned on the same plane, a microelectrode gap 8 is reserved between the first microelectrode array 51 and the second microelectrode array 52, the bottom of the multistage microfluidic cavity 4 stretches across and is arranged on the upper surfaces of the first microelectrode array 51 and the second microelectrode array 52, the microelectrode gap 8 and a graphene microchip aggregate 81 are exposed, the upper cover plate 2 and the first microelectrode array 51 sandwich a first lead-out flat cable 61, the upper cover plate 2 and the second microelectrode array 52 sandwich a second lead-out flat cable 62, and the graphene microchip aggregate 81 respectively and the first microelectrode array 51, the second lead-out flat cable 62 at the microelectrode gap 8, The second microelectrode array 52 is tightly coupled.
The glass substrate 7 is sandwiched between the first microelectrode array 51, the second microelectrode array 52 and the lower coversheet 1.
As shown in fig. 2, the upper cover plate 2 and the lower cover plate 1 are clamped and fixed by a fastening screw 3
As shown in fig. 3, the first microelectrode array 51 and the second microelectrode array 52 both use the same strip microelectrode, the first microelectrode array 51 includes a first strip microelectrode 511, a second strip microelectrode 512, a third strip microelectrode 513 and a fourth strip microelectrode 514, the second microelectrode array 52 includes a fifth strip microelectrode 521, a sixth strip microelectrode 522 and a seventh strip microelectrode 523, wherein the two ends of the first strip microelectrode 511, the second strip microelectrode 512, the third strip microelectrode 513 and the fourth strip microelectrode 514 are aligned and arranged in parallel, the two ends of the fifth strip microelectrode 521, the six strip microelectrode 522 and the seventh strip microelectrode 523 are aligned and arranged in parallel, the first strip microelectrode 511, the fifth strip microelectrode, the second strip microelectrode 512, the sixth strip microelectrode 522, the third strip microelectrode 513, the seventh strip microelectrode 523 and the fourth strip microelectrode 514 are sequentially staggered, and the graphene microchip aggregate 8 is arranged in the gap 8, the graphene nanoplatelet aggregate 8 is composed of a plurality of graphene nanoplatelets one 811.
As shown in fig. 1 and fig. 2, the multistage microfluidic cavity 4 is formed by stacking a plurality of coaxial hollow cylinders with equal outer diameters, from the top to the bottom of the multistage microfluidic cavity 4, the inner diameters of the hollow cylinders become smaller in sequence, the center of the bottom of the multistage microfluidic cavity 4 is opposite to the center of the microelectrode gap 8, and the inner diameter of the bottom of the multistage microfluidic cavity 4 is equal to the microelectrode gap distance.
The material of the multistage microfluidic cavity 4 is organic glass.
The material of the multistage micro-fluid cavity 4 adopts polydimethylsiloxane or off-stoichiometrically thio-ene polymer material.
The inner surface of the multistage microfluidic cavity 4 is coated with polyethylene glycol liquid with molecular weight in the range of 200-400.
Method of operation
As shown in fig. 5, the operation method of the heavy metal ion sensor based on the graphene material includes the following specific steps:
step one, placing the multistage micro-fluid cavity 4 with the inner wall coated with polyethylene glycol liquid with the molecular weight range of 200-400 in a drying oven, and heating and drying for 1h at the temperature of 60-70 ℃;
mounting the multistage micro-fluid cavity dried in the first step on the heavy metal ion sensor based on the graphene material, and connecting the heavy metal ion sensor based on the graphene material with a conventional electrochemical workstation;
thirdly, on the basis of the second step, applying a 1-3V sinusoidal voltage signal between the first lead-out flat cable and the second lead-out flat cable, adjusting the signal frequency to 1M-3MHz, controlling and moving the partially reduced graphene oxide micro-slabs to a microelectrode gap of the first microelectrode array and the first microelectrode array by utilizing a positive dielectrophoresis technology to form a graphene micro-slab aggregate, and simultaneously enabling the graphene micro-slab aggregate to reach a set density through microscopic observation;
step four: on the basis of the third step, 5-100 mu L of metal ion solution to be detected is dripped into the multistage micro-fluid cavity;
step five: on the basis of the fourth step, testing the conductivity of the graphene microchip aggregate after adsorbing the metal ions, and generating a current mutation and a volt-ampere characteristic curve under constant voltage through a computer connected with the electrochemical workstation;
step six: recording the current mutation and the volt-ampere characteristic curve obtained in the fifth step into a knowledge base, and performing comparative analysis according to the relative change of the conductivity of the graphene microchip aggregate after metal ions are adsorbed, so as to identify the concentration or the type of the current sample;
and seventhly, repeating the fourth step to the sixth step when the sample with the next concentration or the next metal ion is measured continuously.
The conductivity G of the graphene nanoplatelet aggregate after metal ion adsorption is equal to I/U, wherein the voltage U is any one of 0.5 to 1V, and I is a current value at the current voltage.
The relative change of G is delta G-G0, wherein G0 is the conductivity of the graphene microchip aggregate which does not adsorb metal ions in a pure solvent environment; for each concentration of metal ion solution measured, a Δ Gi (i ═ 1,2,3, … n) is obtained. By comparing the numerical differences among Δ G1, Δ G2 and Δ G3 …, the concentration and the type of the metal ions corresponding to each datum can be judged.
Example 2
As shown in figure 1, the heavy metal ion sensor based on the graphene material comprises a first microelectrode array 51, a second microelectrode array 52, an upper cover plate 2, a lower cover plate 1 and a multistage microelectrode array 4, wherein the first microelectrode array 51 and the second microelectrode array 52 are arranged between the upper cover plate 2 and the lower cover plate 1 and are positioned on the same plane, a microelectrode gap 8 is reserved between the first microelectrode array 51 and the second microelectrode array 52, the multistage microelectrode array 4 stretches across and is arranged on the upper surfaces of the first microelectrode array 51 and the second microelectrode array 52, the microelectrode gap 8 and a graphene microchip aggregate 81 are exposed at the bottom of the multistage microelectrode array 4, the upper cover plate 2 and the first microelectrode array 51 sandwich a first lead-out flat cable 61, the upper cover plate 2 and the second microelectrode array 52 sandwich a second lead-out flat cable 62, and the graphene microchip aggregate 81 respectively and the first microelectrode array 51 at the microelectrode gap 8, The second microelectrode array 52 is tightly coupled.
The glass substrate 7 is sandwiched between the first microelectrode array 51, the second microelectrode array 52 and the lower coversheet 1.
As shown in figure 2, the upper cover plate 2 and the lower cover plate 1 are clamped and fixed by fastening screws 3, and the number of the fastening screws 3 is 4.
As shown in fig. 4, the first microelectrode array 51 comprises a first microelectrode 515, a second microelectrode 516 and a third microelectrode 517, two ends of the first microelectrode 515, the second microelectrode 516 and the third microelectrode 517 are aligned and parallel to each other, an arc part is arranged at one end of the same side, the second microelectrode array 52 comprises a first microelectrode 524, a second microelectrode 525 and a third microelectrode 526, two ends of the first microelectrode 524, the second microelectrode 525 and the third microelectrode 526 are aligned and parallel to each other, a disc part is arranged at one end of the same side, the arc part of the first microelectrode 515 is correspondingly wrapped outside the disc part of the first microelectrode 524, the first microelectrode 524 and the first microelectrode 515 are on the same straight line, the arc part of the second microelectrode 516 is correspondingly wrapped outside the disc part of the second microelectrode 525, the arc part of the first microelectrode 517 is correspondingly wrapped outside the disc part of the third microelectrode 526, each group of the first microelectrode and the second microelectrode is arranged on the same straight line.
As shown in fig. 1 and fig. 2, the multistage microfluidic cavity 4 is formed by stacking a plurality of coaxial hollow cylinders with equal outer diameters, the inner diameters of the hollow cylinders become smaller from the top to the bottom of the multistage microfluidic cavity 4 in sequence, the center of the bottom of the multistage microfluidic cavity 4 is opposite to the center of the microelectrode gap 8, and the inner diameter of the bottom of the multistage microfluidic cavity 4 is 1.5 times of the microelectrode gap distance.
The material of the multistage microfluidic cavity 4 is organic glass.
The inner surface of the multistage microfluidic cavity 4 is coated with polyethylene glycol liquid with molecular weight in the range of 200-400.
Method of operation
The same as in example 1.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A heavy metal ion sensor based on a graphene material is characterized by comprising a first microelectrode array, a second microelectrode array, an upper cover plate, a lower cover plate and a multistage micro-fluid cavity, the first microelectrode array and the second microelectrode array are both arranged between the upper cover plate and the lower cover plate, and are positioned on the same plane, a microelectrode gap is left between the first microelectrode array and the second microelectrode array, the bottom of the multistage micro-fluid cavity spans and is arranged on the upper surfaces of the first microelectrode array and the second microelectrode array, and the microelectrode gap and the graphene microchip aggregate are exposed, the upper cover sheet and the first microelectrode array clamp a first lead-out flat cable, the upper cover plate and the second microelectrode array clamp a second lead-out flat cable, and the graphene microchip aggregate is tightly combined with the first microelectrode array and the second microelectrode array at the microelectrode gap respectively;
the multistage micro-fluid cavity is formed by overlapping a plurality of coaxial hollow cylinders with equal outer diameters, the inner diameters of the hollow cylinders are sequentially reduced from the top to the bottom of the multistage micro-fluid cavity, the center of the bottom of the multistage micro-fluid cavity is over against the center of a micro-electrode gap, and the distance of the micro-electrode gap is not less than 1.5 times of the distance of the micro-electrode gap.
2. The graphene-based material heavy metal ion sensor of claim 1, wherein the first microelectrode array, the second microelectrode array and the lower cover sheet sandwich a glass substrate therebetween.
3. The graphene-based heavy metal ion sensor according to claim 1 or 2, wherein the upper cover plate and the lower cover plate are clamped and fixed by fastening screws, and the number of the fastening screws is 4.
4. The graphene-material-based heavy metal ion sensor according to claim 1 or 2, wherein the first microelectrode array and the second microelectrode array are identical strip-shaped microelectrodes, and the strip-shaped microelectrodes of the first microelectrode array and the strip-shaped microelectrodes of the second microelectrode array are staggered and arranged in parallel and opposite to each other.
5. The graphene-material-based heavy metal ion sensor according to claim 1 or 2, wherein the first microelectrode array is composed of one or more first microelectrodes parallel to each other and provided with circular arc portions, the second microelectrode array is composed of one or more second microelectrodes parallel to each other and provided with circular disk portions, the circular disk portions of the second microelectrodes are correspondingly wrapped with the circular arc portions of the first microelectrodes, and each group of the first microelectrodes and the second microelectrodes are arranged on the same straight line.
6. The graphene-based material heavy metal ion sensor of claim 1, wherein the multistage microfluidic cavity is made of polydimethylsiloxane or organic glass.
7. The graphene-based heavy metal ion sensor as recited in claim 1, wherein the inner surface of the multistage microfluidic cavity is coated with a polyethylene glycol liquid with a molecular weight range of 200-400.
8. The method for operating the graphene-based material heavy metal ion sensor according to claim 1, comprising the following specific steps:
step one, placing the multi-stage microfluid cavity with the inner wall coated with polyethylene glycol liquid with the molecular weight range of 200-400 in an oven for heating and drying;
mounting the multistage micro-fluid cavity dried in the first step on the heavy metal ion sensor based on the graphene material, and connecting the heavy metal ion sensor based on the graphene material with a conventional electrochemical workstation;
thirdly, on the basis of the second step, applying a 1-3V sinusoidal voltage signal between the first lead-out flat cable and the second lead-out flat cable, adjusting the signal frequency to 1M-3MHz, controlling and moving the partially reduced graphene oxide micro-slabs to a microelectrode gap of the first microelectrode array and the first microelectrode array by utilizing a positive dielectrophoresis technology to form a graphene micro-slab aggregate, and simultaneously enabling the graphene micro-slab aggregate to reach a set density through microscopic observation;
step four: on the basis of the third step, 5-100 mu L of metal ion solution to be detected is dripped into the multistage micro-fluid cavity;
step five: on the basis of the fourth step, testing the conductivity of the graphene microchip aggregate after adsorbing the metal ions, and generating a current mutation and a volt-ampere characteristic curve under constant voltage through a computer connected with the electrochemical workstation;
step six: recording the current mutation and the volt-ampere characteristic curve obtained in the fifth step into a knowledge base, and performing comparative analysis according to the relative change of the conductivity of the graphene microchip aggregate after metal ions are adsorbed, so as to identify the concentration or the type of the current sample;
and seventhly, repeating the fourth step to the sixth step when the sample with the next concentration or the next metal ion is measured continuously.
9. The operating method of the graphene-based material heavy metal ion sensor according to claim 8, wherein the temperature of the oven heating and drying process in the first step is 60-70 ℃ and the time duration is 1 h.
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