CN110628418A - TiO2-quantum dot composite material, preparation method thereof and application thereof in endotoxin detection - Google Patents

TiO2-quantum dot composite material, preparation method thereof and application thereof in endotoxin detection Download PDF

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CN110628418A
CN110628418A CN201910931906.8A CN201910931906A CN110628418A CN 110628418 A CN110628418 A CN 110628418A CN 201910931906 A CN201910931906 A CN 201910931906A CN 110628418 A CN110628418 A CN 110628418A
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quantum dot
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杨丽敏
郜毓堃
张晓慧
孙景涛
姜磊
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China University of Petroleum East China
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Abstract

The invention discloses a TiO 22A quantum dot composite material, a preparation method thereof and application thereof in endotoxin detection, belonging to the field of endotoxin detection. TiO 22The preparation method of the quantum dot composite material comprises the following steps: adding TiO into the mixture2Mixing with quantum dot solution, adding ethanol and ammonia waterPerforming ultrasonic treatment until the solution becomes clear, then adding tetraethoxysilane, stirring and reacting for 12-15h, adding acetone to form precipitate, centrifuging, removing supernatant, and washing to obtain TiO taking silicon dioxide as matrix2-quantum dot aggregation spheres; for the above TiO2Dispersing the quantum dot aggregation balls until the quantum dot aggregation balls are uniformly dispersed, adjusting the pH value to 12 by using a sodium hydroxide solution, reacting for 20-30min, centrifuging, removing a supernatant, washing and drying to obtain TiO2-quantum dot composites. The invention solves the problem of low measurement sensitivity of the existing electrode caused by limited specific surface area, and has the characteristics of high detection sensitivity, high photocatalysis efficiency and high electrode reuse rate.

Description

TiO2-quantum dot composite material, preparation method thereof and application thereof in endotoxin detection
Technical Field
The invention belongs to the field of endotoxin detection, and particularly relates to TiO2-quantum dot composite material, method for its preparation and its use in endotoxin detection.
Background
Endotoxins are complex glycolipids in the outer membrane of gram-negative bacteria that are non-toxic when the endotoxin molecule is embedded in the bacterial outer membrane, and once released into the human blood, the TLR4/MD-2 receptors of the immune system can recognize the lipid a portion of endotoxin, which in turn triggers a series of immunogenic reactions. If left uncontrolled, this cascade of effects leads to the development of hypotension, multiple organ failure, sepsis or septic shock in patients, which is a serious life-threatening safety. Therefore, effective monitoring of endotoxin levels in blood can provide a reference for the prognosis of a clinically relevant disease. Currently the most common method for endotoxin diagnosis is the limulus test. The method measures endotoxin by utilizing the agglutination reaction between limulus reagent and endotoxin, or turbidity change, or the amount of chromogen released from a specific substrate by produced coagulase. However, endotoxin tends to form a bond with plasma protein in serum or whole blood, and potential inhibitory or activating factors are also present in serum, which greatly interfere with the limulus test.
Chinese patent CN 108982623A discloses a nucleic acid aptamer biosensor and its preparation and application, the sensor uses gold electrode as substrate, self-assembles 3-mercaptopropionic acid on the substrate surface, then couples amino group modified nucleic acid aptamer on 3-mercaptopropionic acid. The aptamer biosensor constructed by the technical scheme is used for detecting bacterial endotoxin, and has the advantages of simple construction, high specificity, low detection limit and sensitivity reaching 0.001 EU/mL. However, the conventional electrode regeneration technology is limited to the rough and strong treatment modes such as mechanical polishing, acid-base corrosion and the like, the microstructure of the electrode surface is seriously damaged, and the conventional endotoxin detection electrode is disposable and cannot be reused.
A photocatalytic renewable microelectrode for real-time monitoring of cells is disclosed in "photocatalytic renewable micro-electrochemical sensor for real-time monitoring of cells", published in Angewande Chemie International Edition 2015, volume 54, page 14402, 144062) The/reduction type graphene oxide sandwich type composite material is assembled on the surface of the microelectrode to realize the regeneration of the electrode through photocatalysis. This light assisted regeneration technique enables the manufacture of self-cleaning and renewable electrodes without altering the microstructure and morphology of the interface.
However, photo-assisted regeneration techniques rely on semiconductor nanomaterials mediated photocatalytic reactions. The photocatalysis principle is based on the oxidation-reduction capability of the photocatalyst under the illumination condition, so that the purpose of purifying pollutants is achieved. This reaction proceeds without isolation of the photocatalyst, light, water and oxygen. These constraints determine that the construction of a reusable measuring electrode using light-assisted regeneration techniques must overcome certain difficulties:
1) the measurement interface is limited, and certain limitation is formed on the detection sensitivity.
Whether the electrode for endotoxin detection is planar or rod-shaped, the specific surface area of the electrode material is limited, the effective action area of a measurement interface is limited, and certain limitation is easily formed on the improvement of the detection sensitivity.
2) Compatibility of rod-shaped measuring electrode and photocatalytic reaction
Conventional measurement electrodes are generally cylindrical, about 60mm long and about 6.35mm in cross-sectional diameter. One end is embedded with a working disc electrode with the diameter of 2-3mm, and the working disc electrode is a measuring interface acted with an analyte; one end of the copper lead is led out, and the copper lead can be connected with an electrochemical workstation through an electrode wire to collect electrochemical signals. When the electrode holder is used, one end of the working disk electrode is usually placed downwards on the electrode holder and fixed, so that the working disk electrode is soaked in the solution. If the light-assisted regeneration technique is directly introduced into such a measurement system, the light source can only be disposed opposite the electrode of the operating plate with the wall of the measurement cell therebetween. This mode of operation greatly reduces the amount of light energy that can reach the electrode measurement interface, and the photocatalytic efficiency is severely affected.
3) The utilization efficiency of the photocatalyst to visible light needs to be improved
TiO2Is the most commonly used photocatalyst at present. However, TiO2Belongs to a wide bandgap semiconductor, and the light absorption is only limited in an ultraviolet region. Thus, how to improve TiO2The utilization rate of visible light is a hotspot of research in the field of photocatalysis. Research shows that impurities or defects can be introduced by depositing noble metal, doping metal or nonmetal, sensitizing dye and the like on a semiconductor material, and the method is helpful for improving TiO2The utilization rate of visible light is improved, and the steady-state photodegradation quantum efficiency and the photocatalytic efficiency are improved. The application of graphene materials to the separation of photo-generated electrons and holes disclosed in the above documents broadens TiO2The visible light response of (c). Although a certain effect is achieved, the graphene material has limited absorption capacity for visible light, and tends to have a limitation on photocatalytic performance. In contrast, quantum dots act as a semiconductor with a narrow bandgap when compared to TiO2Phase recombination, not only can more effectively separate TiO2The surface electrons and holes can absorb more visible light, so that TiO is further enhanced2Photocatalytic activity of (1). However, the quantum dots currently used are used in a dispersed state, have limited intrinsic light absorption properties and photoelectron collection and transfer functions, and are compatible with TiO2There is also some randomness in the composition and assistance of (a).
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to solve the main technical problem of overcoming the problem of low measurement sensitivity of the existing electrode caused by limited specific surface area and provides the TiO with high detection sensitivity, high photocatalytic efficiency and high electrode recycling rate2-quantum dot composite material, method for its preparation and its use in endotoxin detection.
In order to solve the technical problem, the technical scheme adopted by the invention is as follows:
one aspect of the present invention provides a TiO compound2-a method for preparing a quantum dot composite material comprising the steps of:
adding TiO into the mixture2Mixing with quantum dot solution, adding ethanol and ammonia water, ultrasonic treating until the solution becomes clear, adding ethyl orthosilicate, stirring to react for 12-15 hr, adding acetone to form precipitate, centrifuging, removing supernatant, and washing to obtain TiO with silicon dioxide as matrix2-quantum dot aggregation spheres;
for the above TiO2Dispersing the quantum dot aggregation balls until the quantum dot aggregation balls are uniformly dispersed, adjusting the pH value to 12 by using a sodium hydroxide solution, reacting for 20-30min, centrifuging, removing a supernatant, washing and drying to obtain TiO2-a quantum dot composite;
the quantum dots are water-soluble quantum dots with surface ligands of mercaptopropionic acid, and the emission wavelength of the quantum dots is 510 nm.
Preferably, the quantum dots are cadmium telluride quantum dots, and the concentration of the cadmium telluride quantum dot solution is 3.2 multiplied by 1014particles/mL。
Preferably, the TiO is2The adding mass of the cadmium telluride quantum dot solution and the tetraethoxysilane is as follows: volume: the volume ratio is 10: 10: 0.05-0.1.
The invention also provides the TiO of any technical scheme2TiO prepared by preparation method of-quantum dot composite material2-quantum dot composite, said TiO2The quantum dot composite material is in the shape of a one-sided, concave, pie.
The invention also provides a composition containing the aboveTechnical scheme of the TiO2-an electrode of quantum dot composite material, said electrode being TiO2-electrode of quantum dot composite-nanogold-affinity peptide modified interface, said TiO2The electrode of the quantum dot composite material-nanogold-affinity peptide modified interface is prepared by the following method:
taking out the TiO2Adding a Nafion-ethanol solution into the quantum dot composite material, uniformly mixing, dropwise adding the Nafion-ethanol solution onto the surface of the polished glassy carbon electrode, and drying at room temperature to obtain TiO2-an electrode with a quantum dot composite modified interface;
to the above TiO2Dripping nano gold colloid solution on the electrode surface of the quantum dot composite material modified interface, and drying at a certain temperature to obtain TiO2-electrodes of quantum dot composite-nanogold modified interfaces;
mixing the above TiO with a solvent2Soaking the electrode of the-quantum dot composite material-nano gold modified interface in an affinity peptide solution for full reaction to obtain TiO2-quantum dot composite-nanogold-affinity peptide modified interface electrode.
Preferably, one end face of the electrode is TiO2-quantum dot composite-nanogold-affinity peptide modified interface.
The invention also provides a detection device comprising the electrode in any technical scheme, which comprises a reactor, a saturated calomel electrode, a platinum wire electrode, a measuring electrode and an electrochemical workstation, wherein the measuring electrode is TiO2And an electrode of a quantum dot composite material-nanogold-affinity peptide modified interface, wherein the saturated calomel electrode, the platinum wire electrode and the measuring electrode are respectively and electrically connected with the electrochemical workstation.
Preferably, the reactor is a cylinder with two open ends, the measuring electrode is partially sleeved at the bottom of the reactor, and the TiO of the measuring electrode2-a quantum dot composite-nanogold-affinity peptide modified interface is located in the reactor, and the TiO is2-the plane of the quantum dot composite-nanogold-affinity peptide modified interface is perpendicular to the upper bottom surface of the reactor; a seal is arranged between the measuring electrode and the reactorA sealing member; the saturated calomel electrode and the platinum wire electrode are partially sleeved at the top of the reactor.
Preferably, the coating also comprises a coating on the TiO2-a xenon lamp directly above the quantum dot composite material-nanogold-affinity peptide modified interface.
The invention also provides a method for detecting endotoxin by using the detection device in any technical scheme, which comprises the following steps:
adding a sample to be detected into the reactor, after the sample to be detected fully reacts at room temperature, moving the sample to be detected out of the reactor, adding a potassium ferricyanide/potassium ferrocyanide mixed solution and a potassium chloride solution into the reactor, measuring the electrochemical impedance of the measuring electrode, and obtaining the content of endotoxin by using a standard curve.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention provides a TiO2Preparation method of-quantum dot composite material, preparation method is simple, and prepared TiO2The quantum dot composite material has a regular round cake-shaped structure with one concave surface, and the TiO content is greatly improved2-specific surface area of the quantum dot composite;
2. the invention provides an electrode comprising TiO2The quantum dot composite material-nanogold-affinity peptide modified interface has higher sensitivity;
3. the invention provides a detection device which has the characteristics of high sensitivity, high photocatalytic efficiency and high electrode recycling rate.
Drawings
Fig. 1 is a schematic structural diagram of a detection apparatus according to an embodiment of the present invention;
FIG. 2 shows TiO provided in the examples of the present invention2-scanning electron microscopy characterization of the quantum dot composite;
FIG. 3 shows the electrical impedance spectrum of the measuring electrode according to the present invention before and after the endotoxin reaction at 0.1 pg/mL;
FIG. 4 shows the effect of repeated use of the measuring electrode according to the embodiment of the present invention;
FIG. 5 shows TiO prepared in comparative example 1 of the present invention2-scanning electron microscopy characterization of the quantum dot composite;
FIG. 6 shows TiO prepared according to comparative example 2 of the present invention2-scanning electron microscopy characterization of the quantum dot composite;
FIG. 7 shows TiO prepared in comparative example 3 of the present invention2-scanning electron microscopy characterization of the quantum dot composite;
FIG. 8 shows TiO prepared in comparative example 4 of the present invention2-scanning electron microscopy characterization of the quantum dot composite;
FIG. 9 shows TiO prepared in comparative example 5 of the present invention2-scanning electron microscopy characterization of the quantum dot composite;
in the above figures: 1. a reactor; 2. a saturated calomel electrode; 3. a platinum wire electrode; 4. a measuring electrode; 5. an electrochemical workstation; 6. and a sealing member.
Detailed Description
The invention is described in detail below by way of exemplary embodiments. It should be understood, however, that elements, structures and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "bottom", "inner", "top", and the like, indicate orientations or positional relationships based on those shown in fig. 1, are only used for convenience of description and simplicity of description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.
One aspect of the present invention provides a TiO compound2-a method for preparing a quantum dot composite material comprising the steps of:
s1: adding TiO into the mixture2Mixing with quantum dot solution, adding ethanol and ammonia water, ultrasonic treating until the solution becomes clear, adding ethyl orthosilicate, stirring and reacting for 12-15hAdding acetone to form precipitate, centrifuging, removing supernatant, and washing to obtain TiO with silicon dioxide as matrix2-quantum dot aggregate spheres. In this step, the reaction time is specifically limited because the reaction time is determined so that the discoid TiO having a concave center on one surface cannot be finally formed2Key to Quantum dot composites, one-sided, dished, pie TiO2The quantum dot composite material is obtained by etching silicon dioxide by strong alkali, and if a round cake-shaped TiO with a concave center on one surface is desired to be finally obtained2The quantum dot composite material is prepared by firstly obtaining a regular spherical precursor, wherein the precursor obtained with the reaction time of less than 12h or more than 15h is in a large-scale irregular aggregation form, so that a disc-shaped TiO with a concave center at one surface cannot be formed2-quantum dot composites. In addition, ethanol and ammonia water are added in the step, and it needs to be noted that ethanol is used as a cosolvent and is beneficial to TiO2And tetraethoxysilane dispersed or dissolved in the reaction system. Moreover, the ethanol also has the functions of adjusting the polarity, the speed of catalyzing the hydrolysis of the tetraethoxysilane by the ammonia water, the particle size and the like; the function of the ammonia water is to catalyze the hydrolysis of the tetraethoxysilane to form silicon dioxide spheres.
S2: for the above TiO2Dispersing the quantum dot aggregation balls until the quantum dot aggregation balls are uniformly dispersed, adjusting the pH value to 12 by using a sodium hydroxide solution, reacting for 20-30min, centrifuging, removing a supernatant, washing and drying to obtain TiO2-quantum dot composites. In this step, the pH and the reaction time are specifically limited because the S2 step mainly etches the spherical precursor obtained in the S1 step, and the pH and the etching time are to form a regular discoid TiO with a concave center on one side2The key of the quantum dot composite material is that the pH value is too large or too small, and the regular discoid TiO with the concave center on one surface cannot be formed by too long or too short etching time2-quantum dot composites.
The quantum dots are water-soluble quantum dots with surface ligands of mercaptopropionic acid, and the emission wavelength of the quantum dots is 510 nm. This example specifically defines quantum dots as water-soluble quantum dots with a surface ligand of mercaptopropionic acid, since the use of water-soluble quantum dots canThe method has the advantages of direct reaction in the water phase, no need of adding additional solvent and surfactant, convenience, environmental protection and no toxicity. If quantum dots without water solubility are adopted, organic solvent and surfactant are added, so that the operation is complex and the environment is polluted. Meanwhile, this embodiment also defines the emission wavelength of the quantum dot as 510nm, which is a fluorescence emission peak, the peak having the maximum intensity in the fluorescence spectrum, and defines the reflection wavelength as 510nm because the quantum dot whose emission wavelength is at a short wavelength of 510nm, and the TiO2Has better energy matching and is beneficial to electron transfer.
In a preferred embodiment, the quantum dots are cadmium telluride quantum dots, and the concentration of the cadmium telluride quantum dot solution is 3.2 x 1014particles/mL. The embodiment specifically defines the quantum dots as cadmium telluride quantum dots, wherein the cadmium telluride quantum dot solution is prepared by the following method:
s1: preparing a sodium hydrogen telluride solution, dissolving 0.2-0.3g of sodium borohydride in 8mL of ice water, introducing argon for 20-30min, and removing oxygen. Then adding 0.1-0.15g of fully ground tellurium powder and stirring to ensure that the sodium borohydride and the tellurium powder fully react. After 30min, the solution can be observed to be gradually clarified from black, a small amount of light purple precipitate is at the bottom, and the upper clear solution is taken, namely the sodium telluride solution.
S2: a cadmium telluride quantum dot solution was prepared by dissolving 0.46g of cadmium chloride in 70mL of water, adding 400mL of mercaptopropionic acid thereto, and adjusting the pH to 11-12 with sodium hydroxide at a concentration of 2 mol/L. Pouring the solution into a three-neck flask, adding clean magneton, introducing argon gas for 20-30min, and removing oxygen. And (3) sucking 2-3mL of the sodium hydrogen telluride solution prepared in the step S1 by using an injector, quickly adding the solution into a three-necked flask, starting stirring, heating and refluxing at 100 ℃ for no more than 1h, and stopping heating to obtain a cadmium telluride quantum dot crude product with carboxyl on the surface. And finally, adding methanol with three times volume into the crude cadmium telluride quantum dot solution to enable the crude cadmium telluride quantum dot solution to be aggregated and precipitated, centrifuging the solution at the speed of 7000-8000r/min for 10min, removing supernatant, washing the solution for three times by using the methanol, and re-dissolving the purified quantum dots in 10mL of water to obtain the cadmium telluride quantum dot solution. In this stepThe reflow time is a key parameter affecting the position of the emission peak of the quantum dot. The longer the reflow time, the larger the size of the generated quantum dot, and the longer the position of the emission peak is shifted to the long wavelength due to the confinement effect of the quantum dot. Quantum dots having emission peak at short wavelength of 510nm, and TiO2Has better energy matching and is beneficial to electron transfer.
In a preferred embodiment, the TiO is2The adding mass of the cadmium telluride quantum dot solution and the tetraethoxysilane is as follows: volume: the volume ratio is 10: 10: 0.05-0.1. In this example, TiO is defined2The reason why the adding proportion of the cadmium telluride quantum dot solution and the tetraethoxysilane is too large is that if the tetraethoxysilane is used, the proportion of the silicon dioxide in the formed spherical precursor is too much, and the silicon dioxide is not easy to etch, so that the regular round cake-shaped TiO with the concave center at one surface cannot be formed2-a quantum dot composite; if the amount of tetraethoxysilane used is too small, the resulting spherical precursor is easily over-etched, and regular discoid TiO having a concave center on one side cannot be formed2-quantum dot composites. For this ratio, it may also be 10: 10: 0.06, 10: 10: 0.07, 10: 10: 0.08, 10: 10: 0.09 and any point value ratios within the range thereof.
The invention also provides the TiO of any embodiment2TiO prepared by preparation method of-quantum dot composite material2-quantum dot composites, TiO2The quantum dot composite material is in the shape of a one-sided, concave, pie. TiO 22Is the most commonly used photocatalyst at present. However, TiO2Belongs to a wide bandgap semiconductor, and the light absorption is only limited in an ultraviolet region. Thus, how to improve TiO2The utilization rate of visible light is a hotspot of research in the field of photocatalysis. The quantum dot is used as a semiconductor with narrow forbidden band when being mixed with TiO2Phase recombination, not only can more effectively separate TiO2The surface electrons and holes can absorb more visible light, so that TiO is further enhanced2Photocatalytic activity of (1). However, the quantum dots currently used are used in a dispersed state, have limited intrinsic light absorption properties and photoelectron collection and transfer functions, and are compatible with TiO2There is also some randomness in the composition and assistance of (a). TiO provided by the embodiment of the invention2The quantum dot composite material can enhance TiO by the following two ways2And make the quantum dot pair TiO2The compounding and the assistance of (2) become necessary from random: on one hand, the quantum dots exist in an aggregate form, an electron transfer chain of green plant photosynthesis is simulated, and the aggregate form is more favorable for collection and transmission of photoelectrons and promotes TiO2Separation of electrons and holes at the surface; on the other hand, the material takes silicon dioxide as a substrate, quantum dots and TiO are added in the preparation process2Fixed in the same nano structure to make the quantum dots and TiO2The composition and the assistance of (c) are changed from random to inevitable. Due to the TiO2The quantum dot composite material is in a round cake shape with a concave center on one surface, and is similar to red blood cells, and the red blood cells have larger specific surface area and can adapt to the functions of the red blood cells to the maximum extent. Thus, the TiO2The quantum dot composite material can effectively enlarge the measurement interface of the measurement electrode 4, increase the contact area between the sensing material and the analyte to be detected, and finally obtain the detection performance with high sensitivity.
The invention also provides a TiO compound containing the above embodiment2-electrodes of quantum dot composite material, the electrodes being TiO2-electrode of quantum dot composite-nanogold-affinity peptide modified interface, TiO2The electrode of the quantum dot composite material-nanogold-affinity peptide modified interface is prepared by the following method:
s1: taking TiO2Adding a Nafion-ethanol solution into the quantum dot composite material, uniformly mixing, dropwise adding the Nafion-ethanol solution onto the surface of the polished glassy carbon electrode, and drying at room temperature to obtain TiO2-electrodes with quantum dot composites modified interfaces. In the step, Nafion is perfluorinated resin solution with the mass fraction of 5%, and the solvent is water and low aliphatic alcohol. When it is used, it is diluted 100 times with ethanol to obtain 0.05% Nafion-ethanol solution.In essence, poly-tetraVinyl fluorideAnd perfluoro-3, 6-diepoxy-4-methyl-7-decene-sulfuric acid, commonly used to modify glassy carbon electrodes, whose main function is to fix and prevent the nanoparticles from falling off; secondly, it is negatively charged, and can utilize the electrostatic action to reduce the interference of some negatively charged substances, i.e. improve the anti-interference capability. The glassy carbon electrode subjected to polishing treatment is subjected to polishing treatment by the following method: pouring a little of alumina powder with the grain diameter of 0.5 mu m on the polishing flannelette, dripping 5-6 drops of ultrapure water to be uniformly mixed with the alumina powder to form alumina slurry, and polishing the glassy carbon electrode on the alumina slurry in an 8 shape for about 3 min; then, rinsing the surface of the electrode by using ultrapure water, and then ultrasonically cleaning for 3-5min in an ultrapure water medium; taking out, polishing the electrode on the alumina slurry for about 3min, washing the surface of the electrode with ultrapure water, and then sequentially placing the electrode in ultrapure water and ethanol mediums for ultrasonic cleaning for 3min respectively; and after the ultrasonic treatment is finished, washing the surface of the electrode by using ultrapure water, and then blowing the electrode by using inert gas argon to dry, thereby finishing the pretreatment of the glassy carbon electrode. The glassy carbon electrode is selected because compared with a gold electrode, the glassy carbon electrode has the advantages of good conductivity, high chemical stability, easiness in polishing into a mirror surface, wide potential application range and the like.
S2: to the above TiO2Dripping nano gold colloid solution on the electrode surface of the quantum dot composite material modified interface, and drying at a certain temperature to obtain TiO2Quantum dot composite-nanogold modified interface electrodes. In the step, the drying condition of drying at a certain temperature is drying treatment for 5 hours at 65 ℃; the nano gold colloid solution is prepared by the following method: adding 195mL of ultrapure water into a beaker, adding 5mL of 10mM chloroauric acid solution into the beaker, heating and stirring until the solution is boiled, quickly adding 4mL of 13.6mM trisodium citrate solution into the beaker, continuously heating until the solution is wine red, stopping heating, and obtaining the nano gold colloidal solution after the solution is cooled to room temperature.
S3: mixing the above TiO with a solvent2Soaking the electrode of the-quantum dot composite material-nano gold modified interface in an affinity peptide solution for full reaction to obtain TiO2-quantum dot composite-nanogold-affinity peptide modified interface electrode. In the step, the affinity peptide solution is prepared by the following method: weighing 10mg of Li5-025 affinity peptide with K 'YSSSISSIRAC', K 'and C' being D-turn K and C respectively, having high affinity for endotoxin and dissociation constant KdUp to 0.01 nM. Adding 1-2 drops of dimethyl sulfoxide to dissolve, sequentially adding 0.028-0.030g of tris (2-carboxyethyl) phosphine hydrochloride and 20 mu L of HEPES buffer solution with the concentration of 100nM, and finally adding water to a constant volume of 10mL to obtain the affinity peptide solution with the concentration of 1 mg/mL.
In a preferred embodiment, one end face of the electrode is TiO2-quantum dot composite-nanogold-affinity peptide modified interface. The electrode used in the invention is a disc electrode, the whole electrode is in a rod shape, one end of the electrode is provided with a metal disc surface with the diameter of 3mm, and the metal disc surface is covered with a glassy carbon material, is a measuring interface and can be used for modifying various materials. The other end is a copper wire which is directly inserted into the electrode and connected with the metal disc.
The invention also provides a detection device comprising the electrode of any one of the embodiments, which comprises a reactor 1, a saturated calomel electrode 2, a platinum wire electrode 3, a measuring electrode 4 and an electrochemical workstation 5, wherein the measuring electrode 4 is TiO2An electrode of a quantum dot composite material-nano gold-affinity peptide modified interface, a saturated calomel electrode 2, a platinum wire electrode 3 and a measuring electrode 4 are respectively and electrically connected with an electrochemical workstation 5. The working principle of the detection device is as follows: sequentially coating TiO on the surface of a common glassy carbon electrode2Quantum dot composite material and nanogold, and finally modifying endotoxin affinity peptide Li5-025(K 'YSSSISSIRAC', K 'and C' are respectively D-form K and C) on the surface of the nanogold through a gold-sulfur bond to obtain the measuring electrode 4. When endotoxin detection is carried out, endotoxin in a sample can be captured by affinity peptide on the surface of an electrode, and the formed affinity peptide-endotoxin complex blocks the transmission of electrons on the surface of the electrode through the double actions of steric hindrance and charge repulsion. If potassium ferricyanide/potassium ferrocyanide is used as oxideThe probe is reduced, and the electric impedance can be obviously increased by adopting an electrochemical impedance spectroscopy. Based on this, the quantitative detection of endotoxin can be realized. After the detection is finished, the TiO is irradiated by light2Under the double assistance of the quantum dots and the nano-gold, the photocatalytic activity of the nano-gold is exerted, organic substances (including affinity peptide, endotoxin and the like) on the surface of the electrode are degraded, and the nano-modification material is reserved. Reuse of the electrode can then be achieved by replenishing the consumed affinity peptide.
In a preferred embodiment, the reactor 1 is a cylinder with two open ends, the measuring electrode 4 is partially sleeved on the bottom of the reactor 1, and the TiO of the measuring electrode 42The quantum dot composite material-nano gold-affinity peptide modified interface is positioned in the reactor 1, and TiO2The plane of the quantum dot composite material-nanogold-affinity peptide modified interface is vertical to the upper bottom surface of the reactor 1; a sealing component 6 is arranged between the measuring electrode 4 and the reactor 1; the saturated calomel electrode 2 and the platinum wire electrode 3 are partially sleeved at the top of the reactor 1. A conventional measuring electrode 4 is generally rod-shaped, having a length of about 60mm and a cross-sectional diameter of about 6.35 mm. One end is embedded with a working disc electrode with the diameter of 2-3mm, and the working disc electrode is a measuring interface acted with an analyte; one end of the copper lead is led out, and the copper lead can be connected with an electrochemical workstation 5 through an electrode wire to collect electrochemical signals. When the electrode holder is used, one end of the working disk electrode is usually placed downwards on the electrode holder and fixed, so that the working disk electrode is soaked in the solution. If the light-assisted regeneration technique is directly introduced into such a measurement system, the light source can only be disposed opposite the electrode of the operating plate with the wall of the measurement cell therebetween. This mode of operation greatly reduces the amount of light energy that can reach the electrode measurement interface, and the photocatalytic efficiency is severely affected. This embodiment provides a way to improve the compatibility of the measuring electrode 4 with the photocatalytic reaction. The method specifically comprises the following steps: the measuring electrode 4 was assembled in the syringe instead of the plunger rod of the syringe. When in use, the piston type electrode is fixed on the electrode frame in an inverted manner. At this time, one end of the disk electrode faces upwards and is positioned in the injector. And one end of the copper wire faces downwards and is positioned outside the injector. Before measurement, one end of the syringe needle is cut off to form an open container. The original piston push rod of the syringe is externally provided with a rubber plug, so that the syringe has good performanceAnd (4) good sealing performance. The measurement solution may be placed in a container and directly contacted with the measurement surface of the disk electrode. And the copper wire is not in contact with the solution because the copper wire is positioned outside the injector. A normal xenon lamp was placed directly above the container. After the measurement is finished, the light source can be directly turned on to carry out photocatalytic regeneration treatment. At the moment, no partition wall exists between the light source and the measuring interface, so that the light energy can be effectively ensured to reach the action interface.
In a preferred embodiment, the coating also comprises a coating layer arranged on the TiO2-a xenon lamp directly above the quantum dot composite material-nanogold-affinity peptide modified interface. The xenon lamp enables no partition wall to exist between the light source and the measuring interface, can effectively ensure that light energy reaches the action interface, and improves the compatibility between photocatalysis and electrodes.
The invention also provides a method for detecting endotoxin by using the detection device of any one of the above embodiments, which comprises the following steps:
adding a sample to be detected into the reactor 1, after the sample to be detected fully reacts at room temperature, moving the sample to be detected out of the reactor 1, adding a potassium ferricyanide/potassium ferrocyanide mixed solution and a potassium chloride solution into the reactor 1, measuring the electrochemical impedance of the measuring electrode 4, and obtaining the content of endotoxin by using a standard curve. The detection principle of the detection process is as follows: the endotoxin in the sample can be captured by the affinity peptide on the surface of the electrode, and the formed affinity peptide-endotoxin complex can block the transmission of electrons on the surface of the electrode through the double actions of steric hindrance and charge repulsion. If the potassium ferricyanide/potassium ferrocyanide is used as the redox probe and an electrochemical impedance spectroscopy method is adopted, the electrical impedance can be measured to be obviously increased. Based on this, the quantitative detection of endotoxin can be realized.
To more clearly describe the TiO provided by the embodiments of the present invention in detail2Quantum dot composites, methods for their preparation and their use in endotoxin detection, as described below with reference to specific examples.
Example 1
TiO2Preparation of-Quantum dot composites
Step 1: preparation of TiO2-quantum dot aggregate spheres
Adding 10mg of TiO2(P25), 0.1mL ethanol, 10mL cadmium telluride quantum dot aqueous solution (3.2X 10)14particles/mL, fluorescence emission peak 500nm) and stirred for 10 min. Then, 0.4mL ethanol and 0.08mL ammonia were added and sonicated for 25min until the solution became clear. Adding 75 μ L of ethyl orthosilicate, stirring for reaction for 13h, adding acetone with three times volume to precipitate, centrifuging at 7000r/min for 10min, removing supernatant, and washing with ethanol/water (volume ratio of 1:1) for three times to obtain TiO with silicon dioxide as matrix2-quantum dot aggregate spheres. The cadmium telluride quantum dot aqueous solution is prepared by the following method:
1) preparation of sodium hydrogen telluride solution
0.25g of sodium borohydride was dissolved in 8mL of ice water, and argon was introduced for 25min to remove oxygen. Then 0.15g of fully ground tellurium powder is added and stirred, so that the sodium borohydride and the tellurium powder fully react. After 30min, the solution can be observed to be gradually clarified from black, a small amount of light purple precipitate is at the bottom, and the upper clear solution is taken, namely the sodium telluride solution.
2) Preparing cadmium telluride quantum dot solution
0.46g of cadmium chloride was dissolved in 70mL of water, 400mL of mercaptopropionic acid was added thereto, and the pH was adjusted to 12 with sodium hydroxide at a concentration of 2 mol/L. The solution was poured into a three-necked flask, to which clean magnetons were added, and argon gas was introduced for 25min to remove oxygen. 2.5mL of the sodium hydrogen telluride solution prepared above was sucked up by a syringe, quickly added to a three-necked flask, stirred and heated under reflux at 100 ℃. With the increase of the reaction time, the solution gradually changes from light yellow to orange red to obtain a cadmium telluride quantum dot crude product with carboxyl on the surface. And finally, adding methanol with three times volume into the cadmium telluride quantum dot crude product solution to enable the cadmium telluride quantum dot crude product solution to be aggregated and precipitated, centrifuging for 10min at the speed of 7000r/min, removing supernatant, washing for three times by using methanol, and re-dissolving the purified quantum dots in 10mL of water to obtain the cadmium telluride quantum dot solution.
Step 2: preparation of TiO2-quantum dot composite material
1mg of the TiO prepared in step 1 are taken2Dispersing the quantum dot aggregation spheres in 30mL of ethanol/water (volume ratio of 1:3) solution, and stirring for 25 min. Then, the pH was adjusted to 12 with 2mol/L NaOH, after 25min of reaction, the mixture was centrifuged at 3000r/min for 5min, after which the supernatant was removed and the precipitate was washed three times with ethanol/water (volume ratio 1: 1). Then, the precipitate is placed in a vacuum drying oven for drying treatment for 15h to obtain TiO2-quantum dot composite material, storing it at 4 ℃ in dark place for later use. The TiO being2Scanning electron microscopy characterization of the quantum dot composite is shown in figure 2. As can be seen from FIG. 2, the TiO compound2The quantum dot composite material has a regular round cake shape with one concave surface, and TiO is greatly increased2-specific surface area of the quantum dot composite.
Example 2
TiO2The preparation method of the quantum dot composite material is the same as that of the example 1, and the difference is that 50 mu L of tetraethoxysilane is added in the step 1, and the mixture is stirred and reacts for 12 hours; in step 2, the pH value is adjusted to 12, and the reaction is carried out for 20 min.
Example 3
TiO2The preparation method of the quantum dot composite material is the same as that of the example 1, and the difference is that 100 mu L of tetraethoxysilane is added in the step 1, and the stirring reaction is carried out for 15 hours; in step 2, the pH value is adjusted to 12, and the reaction is carried out for 30 min.
Comparative example 1
TiO2The preparation method of the quantum dot composite material is the same as that of the example 1, except that 75 mu L of tetraethoxysilane is added in the step 1, and the mixture is stirred and reacted for 10 hours.
Comparative example 2
TiO2The preparation method of the quantum dot composite material is the same as that of the example 1, except that 75 mu L of tetraethoxysilane is added in the step 1, and the mixture is stirred and reacts for 17 hours.
Comparative example 3
TiO2The quantum dot composite material was prepared in the same manner as in example 1, except that the pH was adjusted to 12 in step 2 and the reaction was carried out for 40 min.
Comparative example 4
TiO2The quantum dot composite material was prepared in the same manner as in example 1, except that the pH was adjusted to 12 in step 2 and the reaction was carried out for 10 min.
Comparative example 5
TiO2The preparation method of the quantum dot composite material is the same as that of example 1, except that 110. mu.L of tetraethoxysilane is added in the step 1.
The composites prepared from examples 1-3 had a regular pie-like structure with a concave center on one side; as shown in FIGS. 5 and 6, TiO prepared in comparative example 1 and comparative example 22Quantum dot composites do not yield regular spheres; as shown in fig. 7, comparative example 3 has a condition that the etching time is too long, which causes large-area breakage of the aggregation balls; as shown in fig. 8, comparative example 4 has too short etching time, and the aggregation balls are still as original; as shown in FIG. 9, in comparative example 5, addition of excessive ethyl orthosilicate had little effect on balling. However, after etching, the aggregate spheres remained intact, i.e., a discoid structure with one concave side was not obtained.
Example 4
TiO2Construction of-quantum dot composite material-nanogold-affinity peptide modified interface electrode
Step 1: preparation of nano gold colloid solution
Adding 195mL of ultrapure water into a beaker, then adding 5mL of 10mM chloroauric acid solution into the beaker, heating and stirring until the solution is boiled, quickly adding 4mL of 13.6mM trisodium citrate solution into the beaker, continuously heating until the solution is wine red, stopping heating, and obtaining the nano gold colloidal solution after the solution is cooled to room temperature. The mixture is stored at 4 ℃ in the dark for standby.
Step 2: TiO 22Construction of-quantum dot composite material-nanogold-affinity peptide modified interface electrode
1) Pretreatment of glassy carbon electrodes
Pouring a little of alumina powder with the diameter of 0.5 mu m on the polishing flannelette, dripping 5 drops of ultrapure water to be uniformly mixed with the alumina powder to form alumina slurry, and polishing the glassy carbon electrode on the alumina slurry in an 8 shape for about 3 min; then, rinsing the surface of the electrode by using ultrapure water, and then ultrasonically cleaning for 4min in an ultrapure water medium; taking out, polishing the electrode on the alumina slurry for about 3min, washing the surface of the electrode with ultrapure water, and then sequentially placing the electrode in ultrapure water and ethanol mediums for ultrasonic cleaning for 3min respectively; and after the ultrasonic treatment is finished, washing the surface of the electrode by using ultrapure water, and then blowing the electrode by using inert gas argon to dry, thereby finishing the pretreatment of the glassy carbon electrode.
2) Construction of TiO2-quantum dot composite modified interface
1mg of the TiO prepared in example 1 are weighed out2And (3) adding 1mL of Nafion-ethanol solution with the mass fraction of 0.05% into the quantum dot composite material, and uniformly mixing. Absorbing 8 mu L of the solution and dripping the solution on the surface of the glassy carbon electrode after the pretreatment, and finishing TiO after the surface of the electrode is dried at room temperature2Construction of quantum dot composite modified interfaces.
3) Construction of TiO2-quantum dot composite-nanogold modified interface
Taking 20 mu L of the nano gold colloidal solution prepared in the step 1, and dropwise adding the nano gold colloidal solution to the TiO obtained in the step 2)2-quantum dot composite modifying the interface. Then, the electrode is placed in an oven to be dried for 5 hours at the temperature of 65 ℃, and after the surface of the electrode is dried, TiO is finished2Construction of quantum dot composite-nanogold modified interface.
4) Construction of TiO2-quantum dot composite-nanogold-affinity peptide modified interface
10mg of Li5-025 affinity peptide was weighed, 1 drop of dimethyl sulfoxide was added to dissolve it, and then 0.028g of tris (2-carboxyethyl) phosphine hydrochloride and 20. mu.L of HEPES buffer solution with a concentration of 100nM were sequentially added, and finally a volume of 10mL was fixed with water to obtain an affinity peptide solution with a concentration of 1 mg/mL. Then, 3) finishing TiO2Soaking the electrode constructed by the quantum dot composite material-nano gold modified interface in an affinity peptide solution for 12h, and then washing the redundant affinity peptide on the surface of the electrode by ultrapure water to finish TiO2Construction of quantum dot composite material-nanogold-affinity peptide modified interface.
Example 5
Assembly of detection device
Taking a common 20mL plastic syringe, pulling out the needle head, cutting off the syringe needle near the needle head end by 2-3cm with an art designing knife, and leaving the restThe remaining syringe portion was used as a reaction vessel, and the plunger portion was removed to leave the rubber stopper portion, and a cut of about 2mm was made with a utility knife. Then, the TiO prepared in example 4 was added2An electrode constructed by a quantum dot composite material-nanogold-affinity peptide modified interface is inserted into a rubber plug to replace a push rod. Finally, the push rod type electrode is placed upside down on an electrode frame according to the modified interface and the copper lead is downward, so that the assembly of the endotoxin detection device is completed, and the structure is shown in figure 1.
Example 6
Endotoxin measuring method
Step 1: drawing of standard curve
First, 2.5mL of a 4mM potassium ferricyanide/potassium ferrocyanide mixed solution and 2.5mL of a 2mM potassium chloride solution were added as a supporting electrolyte to a reaction vessel of the detection apparatus assembled in example 5, thereby preparing an electrochemical working solution. Then, the saturated calomel electrode 2 and the platinum wire electrode 3 were inserted into the reaction vessel from the direction of the upper end opening of the reaction vessel, and the ends were immersed in the working solution. And finally, respectively connecting the measuring electrode 4, the saturated calomel electrode 2 and the platinum wire electrode 3 to an electrochemical workstation 5 by three wires, obtaining an initial electrochemical impedance map by adopting an electrochemical impedance method, and obtaining an initial resistance value from the initial electrochemical impedance map.
A2 mL plastic syringe was inserted into the reactor 1 and the working solution was aspirated off.
5mL of endotoxin standards at different concentrations (0.1pg/mL, 1pg/mL, 10pg/mL, 100pg/mL, 1ng/mL, 10ng/mL, and 100ng/mL) were added to the reaction vessel and reacted at room temperature for 15 min.
Using a 2mL plastic syringe, the reaction vessel 1 was deepened and the entire amount of the standard solution was aspirated. Then, ultrapure water was added to the reactor 1, and the reactor was washed three times.
And 5mL of working solution is added into the reaction vessel, and the electrochemical impedance is measured through an electrochemical workstation 5 to obtain the resistance value after the reaction. Finally, a standard curve is drawn by taking the change in resistance value (i.e., Δ Ret) as the ordinate and the log of endotoxin concentration as the abscissa.
Step 2: detection of samples
After diluting the blood sample 2 times, 5mL of the diluted blood sample was added to a reaction vessel and reacted at room temperature for 15min, and then the whole sample solution was aspirated out using a 2mL plastic syringe. And 5mL of working solution is added into the reaction vessel, and the electrochemical impedance is measured through an electrochemical workstation 5 to obtain the resistance value after the reaction. And subtracting the initial resistance value to obtain the variation value of the resistance value. Substituting into the standard curve to obtain the endotoxin content in the blood sample.
Example 7
Light-assisted regeneration of measuring electrodes 4
Step 1: light treatment of the measuring electrode 4
After completion of the measurement, the saturated calomel electrode 2 and the platinum wire electrode 3 were removed from the electrode holder, and 2 to 5mL of ultrapure water was added to the reaction vessel. Vertically placing a common xenon lamp (300W, spectral output range of 300-2500 nm) right above the electrode, pulling the electrode, and adjusting the distance from a light source to the surface of the electrode to ensure that the light power reaching the surface of the electrode is 50mW cm-2. After 1h of light treatment, the light source is turned off. Finally, the entire amount of water was aspirated out using a 2mL plastic syringe, and the light treatment of the measuring electrode 4 was completed.
Step 2: regeneration of measuring electrode 4
5mL of the affinity peptide solution obtained in step 2) of example 4 was added to the reaction vessel, and after 12 hours of reaction at room temperature, the entire amount of the affinity peptide solution was aspirated out using a 2mL plastic syringe and washed three times with ultrapure water to complete the regeneration of the measuring electrode 4.

Claims (10)

1.TiO2-a method for preparing a quantum dot composite, characterized in that it comprises the following steps:
adding TiO into the mixture2Mixing with quantum dot solution, adding ethanol and ammonia water, ultrasonic treating until the solution becomes clear, adding ethyl orthosilicate, stirring to react for 12-15 hr, adding acetone to form precipitate, centrifuging, removing supernatant, and washing to obtain TiO with silicon dioxide as matrix2-quantum dot aggregation spheres;
for the above TiO2Dispersing the quantum dot aggregation balls until the quantum dot aggregation balls are uniformly dispersed, adjusting the pH value to 12 by using a sodium hydroxide solution, reacting for 20-30min, centrifuging, removing a supernatant, washing and drying to obtain TiO2-a quantum dot composite;
the quantum dots are water-soluble quantum dots with surface ligands of mercaptopropionic acid, and the emission wavelength of the quantum dots is 510 nm.
2. The TiO of claim 12The preparation method of the quantum dot composite material is characterized in that the quantum dots are cadmium telluride quantum dots, and the concentration of a cadmium telluride quantum dot solution is 3.2 x 1014particles/mL。
3. The TiO of claim 22-method for the preparation of a quantum dot composite, characterized in that said TiO2The adding mass of the cadmium telluride quantum dot solution and the tetraethoxysilane is as follows: volume: the volume ratio is 10: 10: 0.05-0.1.
4. TiO according to any one of claims 1 to 32TiO prepared by preparation method of-quantum dot composite material2-a quantum dot composite material, characterized in that: the TiO is2The quantum dot composite material is in the shape of a one-sided, concave, pie.
5. Comprising the TiO of claim 42-an electrode of a quantum dot composite, characterized in that the electrode is TiO2-electrode of quantum dot composite-nanogold-affinity peptide modified interface, said TiO2The electrode of the quantum dot composite material-nanogold-affinity peptide modified interface is prepared by the following method:
taking out the TiO2Adding a Nafion-ethanol solution into the quantum dot composite material, uniformly mixing, dropwise adding the Nafion-ethanol solution onto the surface of the polished glassy carbon electrode, and drying at room temperature to obtain TiO2-an electrode with a quantum dot composite modified interface;
to the above TiO2Amount ofDripping nano gold colloid solution on the electrode surface of the interface modified by the sub-point composite material, and drying at a certain temperature to obtain TiO2-electrodes of quantum dot composite-nanogold modified interfaces;
mixing the above TiO with a solvent2Soaking the electrode of the-quantum dot composite material-nano gold modified interface in an affinity peptide solution for full reaction to obtain TiO2-quantum dot composite-nanogold-affinity peptide modified interface electrode.
6. The electrode of claim 5, wherein one end face of the electrode is TiO2-quantum dot composite-nanogold-affinity peptide modified interface.
7. Detection device comprising an electrode according to any one of claims 5 to 6, characterized in that it comprises a reactor (1), a saturated calomel electrode (2), a platinum wire electrode (3), a measuring electrode (4), and an electrochemical workstation (5), the measuring electrode (4) being TiO2The electrode of the quantum dot composite material-nano gold-affinity peptide modified interface is characterized in that the saturated calomel electrode (2), the platinum wire electrode (3) and the measuring electrode (4) are respectively and electrically connected with the electrochemical workstation (5).
8. The detection device according to claim 7, wherein the reactor (1) is a cylinder with two open ends, the measuring electrode (4) is partially sleeved on the bottom of the reactor (1), and the TiO of the measuring electrode (4) is2-the quantum dot composite-nanogold-affinity peptide modified interface is located in the reactor (1), and the TiO is2-the plane of the quantum dot composite-nanogold-affinity peptide modified interface is perpendicular to the upper bottom surface of the reactor (1); a sealing component (6) is arranged between the measuring electrode (4) and the reactor (1); the saturated calomel electrode (2) and the platinum wire electrode (3) are partially sleeved at the top of the reactor (1).
9. The detecting device for detecting the rotation of a motor rotor as claimed in claim 8, further comprising a sensor disposed on the TiO2-quantum dot composite-nanoA xenon lamp right above the gold-affinity peptide modified interface.
10. The method for detecting endotoxin according to any one of claims 7 to 9, comprising the steps of:
adding a sample to be detected into the reactor (1), after the sample to be detected fully reacts at room temperature, moving the sample to be detected out of the reactor (1), adding a potassium ferricyanide/potassium ferrocyanide mixed solution and a potassium chloride solution into the reactor (1), measuring the electrochemical impedance of the measuring electrode (4), and obtaining the content of endotoxin by using a standard curve.
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