阅读说明：本技术 金掺杂介孔石墨相氮化碳材料及其制备方法、检测方法 (gold-doped mesoporous graphite phase carbon nitride material, and preparation method and detection method thereof ) 是由 陈星� 柯旭旭 刘瑶 孙晓彤 于 2019-09-17 设计创作，主要内容包括：本发明公开了一种金掺杂介孔石墨相氮化碳材料及其制备方法、检测方法,该制备方法包括：将双氰胺研磨成粉末后溶解于乙醇水溶液中；加入介孔分子筛并超声震荡；进行水浴处理,并搅拌烘干以生成固体产物；将固体产物将氮气气氛下加热,并在达到预设温度后保温,直至生成黄色粉末；对黄色粉末侵入氢氟酸溶液中进行酸化处理；经过水和乙醇洗涤,并对洗涤产物进行干燥以生成mpg-C<Sub>3</Sub>N<Sub>4</Sub>材料；先将mpg-C<Sub>3</Sub>N<Sub>4</Sub>材料与十六烷基三甲基氯化铵置入去离子水中,再加入氯金酸溶液并搅拌；照射紫外线；依次进行离心、水洗、干燥,获得金掺杂介孔石墨相氮化碳纳米复合材料。本发明具有优越的导电性及高的电催化活性,提高电化学检测六价铬的灵敏度,降低检测限。(The invention discloses a gold-doped mesoporous graphite phase carbon nitride material, a preparation method and a detection method thereof, wherein the preparation method comprises the following steps: grinding dicyandiamide into powder and dissolving the powder in an ethanol water solution; adding mesoporous molecular sieve and carrying out ultrasonic oscillation; carrying out water bath treatment, and stirring and drying to generate a solid product; heating the solid product in a nitrogen atmosphere, and preserving heat until a preset temperature is reached until yellow powder is generated; immersing the yellow powder into a hydrofluoric acid solution for acidification treatment; washing with water and ethanol, and drying the washed product to give mpg-C 3 N 4 A material; first mpg-C 3 N 4 Putting the material and hexadecyl trimethyl ammonium chloride into deionized water, adding chloroauric acid solution and stirring; irradiating ultraviolet rays; and sequentially carrying out centrifugation, water washing and drying to obtain the gold-doped mesoporous graphite phase carbon nitride nanocomposite. The invention has excellent conductivity and high electrocatalytic activity, improves the sensitivity of electrochemical detection of hexavalent chromium and reduces the detection limit.)

1. A preparation method of a gold-doped mesoporous graphite phase carbon nitride nanocomposite is characterized by comprising the following steps:

(1) Grinding dicyandiamide into powder and dissolving the powder in an ethanol water solution to form a mixed solution I;

(2) Adding a mesoporous molecular sieve into the mixed solution I and performing ultrasonic oscillation to form mixed solution II;

(3) Carrying out water bath treatment on the mixed solution II, and stirring and drying to generate a solid product;

(4) Heating the solid product in a nitrogen atmosphere at a constant heating rate, and preserving heat after reaching a preset temperature until yellow powder is generated;

(5) Immersing the yellow powder into a hydrofluoric acid solution for acidification treatment to form a mixed solution III;

(6) Washing the mixed solution III with water and ethanol, and drying the washing product to generate mpg-C₃N₄A material;

(7) Firstly, the mpg-C is₃N₄Putting the material and hexadecyl trimethyl ammonium chloride into deionized water, stirring and dissolving to form mixed solution IV, adding chloroauric acid solution into the mixed solution IV, and stirring in a dark environment to form mixed solution V;

(8) Irradiating ultraviolet rays to the mixed solution five to form a mixed solution six;

(9) and sequentially centrifuging, washing and drying the mixed solution VI to obtain a certain amount of the gold-doped mesoporous graphite phase carbon nitride nanocomposite.

2. The method according to claim 1, wherein 30ml of ethanol aqueous solution with a volume ratio of 2:1 is added to each gram of dicyandiamide in the first mixed solution; in the second mixed solution, each gram of dicyandiamide corresponds to 0.5 gram of mesoporous molecular sieve.

3. The method according to claim 1, wherein in the mixed solution III, 4ml of hydrofluoric acid is contained in a hydrofluoric acid solution per gram of dicyandiamide; in the mixed solution IV, the concentration of the hexadecyl trimethyl ammonium chloride is 0.02mol/L, and each milligram of mpg-C₃N₄the material corresponds to 6ml of deionized water; in the fifth mixture, every 7.5 mg of mpg-C₃N₄the material corresponds to 50 mg of chloroauric acid in a solution of chloroauric acid.

4. The method of claim 1, wherein the mesoporous molecular sieve is molecular sieve SBA-15, the hydrofluoric acid solution is 10 Wt%, and the chloroauric acid solution has a concentration of 10 mg/ml.

5. The method of claim 1, wherein the ultrasonic vibration time is 2 hours, the heat preservation time is 4 hours, the acidification time is 48 hours, the stirring time in the dark environment is 0.5 hour, and the ultraviolet irradiation time is 5 hours.

6. The method according to claim 1, wherein the second mixed solution is subjected to a water bath treatment in a water bath at a temperature of 90 ℃; heating the solid product in a tubular furnace, wherein the heating rate is 2.3 ℃/min, and the preset temperature is 550 ℃; the mixed solution five was irradiated with ultraviolet rays through a 300w mercury lamp in a photochemical reaction apparatus.

7. A method for detecting hexavalent chromium in a water environment is characterized by comprising the following steps:

Preparing a certain amount of gold-doped mesoporous graphite phase carbon nitride nanocomposite material by the method for preparing the gold-doped mesoporous graphite phase carbon nitride nanocomposite material according to any one of claims 1 to 6;

Dissolving the gold-doped mesoporous graphite phase carbon nitride nanocomposite material in deionized water to form a detection solution, sucking a suspension of the detection solution, dripping the suspension on a glassy carbon electrode, and finally air-drying the modified glassy carbon electrode;

Thirdly, detecting hexavalent chromium in the water environment by using the dried glassy carbon electrode;

And fourthly, increasing the concentration of hexavalent chromium in the water environment in an equivalent manner, measuring a series of electrochemical response values, and drawing a corresponding voltammetry curve.

8. the method of detecting hexavalent chromium in aqueous environments of claim 7, wherein the glassy carbon electrode is further pretreated prior to dispensing the suspension; the pretreatment method of the glassy carbon electrode comprises the following steps:

(a) Polishing the glassy carbon electrode by using alumina powder with the grain sizes of 1.0 mu m, 0.3 mu m and 0.05 mu m in sequence until the glassy carbon electrode presents a mirror surface;

(b) sequentially using nitric acid, absolute ethyl alcohol and deionized water to carry out ultrasonic treatment on the glassy carbon electrode for 2min so as to clean the surface of the glassy carbon electrode; wherein the volume ratio of the nitric acid to the absolute ethyl alcohol is 1: 1;

(c) and drying the cleaned glassy carbon electrode at normal temperature for later use.

9. The method for detecting hexavalent chromium in water environments of claim 7, wherein in the second step, the mass of the gold-doped mesoporous graphite phase carbon nitride nanocomposite in each detection solution is 1mg, and the volume of deionized water is 1 ml; before the suspension is sucked, carrying out ultrasonic treatment on the detection liquid for 2 min; sucking the suspension by a micropipette, wherein the sucking amount of the suspension in each detection liquid is 5 mu L;

In the third step, linear scanning voltammetry is adopted to detect hexavalent chromium; wherein the electrolyte is 0.1M HCl, and the PH value is 1 +/-0.5; in the experimental parameters of the linear sweep, the sweep range was 0.8V to-0.3V and the sweep rate was 100 mV/s.

10. a gold-doped mesoporous graphite-phase carbon nitride nanocomposite, characterized by being prepared by the method for preparing a gold-doped mesoporous graphite-phase carbon nitride nanocomposite according to any one of claims 1 to 6.

Technical Field

The invention relates to a preparation method of a composite material in the technical field of electrochemical analysis and detection, in particular to a preparation method of a gold-doped mesoporous graphite phase carbon nitride nanocomposite material, a detection method of hexavalent chromium in a water environment, and the gold-doped mesoporous graphite phase carbon nitride nanocomposite material prepared by the preparation method.

background

With the development of society and the progress of science and technology, the problem of environmental pollution seems to be more and more serious, and the heavy metal pollution is particularly prominent. In the process of mining, smelting and processing heavy metals, a lot of heavy metals such as lead, mercury, cadmium, cobalt, chromium and the like enter the atmosphere, water and soil to cause serious environmental pollution. Heavy metal sewage is directly or indirectly discharged into rivers, lakes and seas or into soil without being treated, and because heavy metal elements cannot be automatically degraded in the ecological environment, even if the concentration is low, the heavy metal elements can be accumulated in algae and bottom mud and adsorbed by the body surfaces of fishes and shellfishes to generate food chain concentration, thereby causing public nuisance.

Chromium is widely used in the industries of electroplating, leather preparation, dyeing and the like. Chromium exists mainly in trivalent and hexavalent forms in water environment, wherein Cr (VI) has the strongest toxicity, has great harm to biological systems and has strong carcinogenicity after long-term contact. Therefore, it is of great significance to the measurement of Cr (VI). The commonly used Cr (VI) detection methods include X-ray fluorescence spectroscopy, plasma mass spectrometry, atomic absorption spectroscopy and the like. Although these methods have high sensitivity, the analysis process is time-consuming, complicated and requires highly trained personnel. The electrochemical method can distinguish Cr (III) and Cr (VI) without any separation step, can realize detection in a micro instrument and has the capability of analyzing heavy metals on site. Therefore, the electrode material is a decisive factor for the effectiveness of the electrochemical analysis. Among a plurality of materials, the noble metal gold nanoparticles have excellent catalytic effect on Cr (VI) and have heavy weight on determining trace chromiumIt has important meaning. Au-mpg-C₃N₄as an electrochemical modified electrode material, Cr (VI) in a water environment can be detected. However, at present, there is no Au-mpg-C₃N₄Efficient synthesis of (1), and other mpg-C₃N₄The composite material has poor detection effect on hexavalent chromium.

Disclosure of Invention

to solve the current shortage of Au-mpg-C₃N₄Efficient synthesis of (1), and other mpg-C₃N₄The invention provides a gold-doped mesoporous graphite phase carbon nitride material, a preparation method thereof and a detection method thereof, and solves the technical problem that the detection effect of a composite material on hexavalent chromium is poor.

The invention is realized by adopting the following technical scheme: a preparation method of a gold-doped mesoporous graphite phase carbon nitride nanocomposite comprises the following steps:

(1) Grinding dicyandiamide into powder and dissolving the powder in an ethanol water solution to form a mixed solution I;

(2) Adding a mesoporous molecular sieve into the mixed solution I and performing ultrasonic oscillation to form mixed solution II;

(3) Carrying out water bath treatment on the mixed solution II, and stirring and drying to generate a solid product;

(4) Heating the solid product in a nitrogen atmosphere at a constant heating rate, and preserving heat after reaching a preset temperature until yellow powder is generated;

(5) Immersing the yellow powder into a hydrofluoric acid solution for acidification treatment to form a mixed solution III;

(6) Washing the mixed solution III with water and ethanol, and drying the washing product to generate mpg-C₃N₄A material;

(7) Firstly, the mpg-C is₃N₄Putting the material and hexadecyl trimethyl ammonium chloride into deionized water, stirring and dissolving to form mixed solution IV, adding chloroauric acid solution into the mixed solution IV, and stirring in a dark environment to form mixed solution V;

(8) irradiating ultraviolet rays to the mixed solution five to form a mixed solution six;

(9) and sequentially centrifuging, washing and drying the mixed solution VI to obtain a certain amount of the gold-doped mesoporous graphite phase carbon nitride nanocomposite.

Dissolving dicyandiamide powder in an ethanol aqueous solution to form a first mixed solution, adding a mesoporous molecular sieve into the first mixed solution, oscillating to form a second mixed solution, performing water bath treatment on the second mixed solution, stirring and drying to obtain a solid product, heating the solid product in nitrogen, performing heat preservation to form yellow powder, soaking the yellow powder into hydrofluoric acid to treat the yellow powder to form a third mixed solution, and finally washing and drying the third mixed solution to obtain the mpg-C₃N₄materials, hereafter, the invention will mpg-C₃N₄Mixing the material with hexadecyl trimethyl ammonium chloride to form mixed solution IV, adding chloroauric acid solution into the mixed solution IV, stirring to form mixed solution V, irradiating ultraviolet rays to the mixed solution V to form mixed solution VI, and finally centrifuging, washing and drying the mixed solution VI to obtain the gold-doped mesoporous graphite phase carbon nitride nano composite material, so that the problem that the existing Au-mpg-C material is lacked is solved₃N₄Efficient synthesis of (1), and other mpg-C₃N₄The composite material can efficiently detect hexavalent chromium in water environment, and the prepared gold-doped mesoporous graphite phase carbon nitride nanocomposite has excellent conductivity and high electro-catalytic activity, so that the catalytic capability of hexavalent chromium in a solution is improved, the sensitivity of electrochemical detection of hexavalent chromium is further improved, and the technical effect of detection limit is reduced.

As a further improvement of the above scheme, in the mixed solution one, each gram of dicyandiamide corresponds to 30ml of ethanol aqueous solution with the volume ratio of 2: 1; in the second mixed solution, each gram of dicyandiamide corresponds to 0.5 gram of mesoporous molecular sieve.

as a further improvement of the above scheme, in the mixed solution three, 4ml of hydrofluoric acid is contained in each gram of dicyandiamide corresponding hydrofluoric acid solution; in the mixed solution IV, the concentration of the hexadecyl trimethyl ammonium chloride is 0.02mol/L, and each milligram of mpg-C₃N₄materialCorresponding to 6ml of deionized water; in the fifth mixture, every 7.5 mg of mpg-C₃N₄The material corresponds to 50 mg of chloroauric acid in a solution of chloroauric acid.

As a further improvement of the scheme, the mesoporous molecular sieve is molecular sieve SBA-15, the weight percentage of the hydrofluoric acid solution is 10% Wt, and the concentration of the chloroauric acid solution is 10 mg/ml.

As a further improvement of the scheme, the ultrasonic oscillation time is 2 hours, the heat preservation time is 4 hours, the acidification treatment time is 48 hours, the stirring time in a dark environment is 0.5 hour, and the ultraviolet irradiation time is 5 hours.

As a further improvement of the scheme, the mixed solution II is subjected to water bath treatment by a water bath kettle, and the water bath temperature is 90 ℃; heating the solid product in a tubular furnace, wherein the heating rate is 2.3 ℃/min, and the preset temperature is 550 ℃; the mixed solution five was irradiated with ultraviolet rays through a 300w mercury lamp in a photochemical reaction apparatus.

The invention also provides a detection method of hexavalent chromium in a water environment, which comprises the following steps:

Firstly, preparing a certain amount of gold-doped mesoporous graphite phase carbon nitride nanocomposite material by the preparation method of the gold-doped mesoporous graphite phase carbon nitride nanocomposite material;

Dissolving the gold-doped mesoporous graphite phase carbon nitride nanocomposite material in deionized water to form a detection solution, sucking a suspension of the detection solution, dripping the suspension on a glassy carbon electrode, and finally air-drying the modified glassy carbon electrode;

Thirdly, detecting hexavalent chromium in the water environment by using the dried glassy carbon electrode;

And fourthly, increasing the concentration of hexavalent chromium in the water environment in an equivalent manner, measuring a series of electrochemical response values, and drawing a corresponding voltammetry curve.

As a further improvement of the above scheme, the glassy carbon electrode is also pretreated before the suspension is dripped; the pretreatment method of the glassy carbon electrode comprises the following steps:

(a) polishing the glassy carbon electrode by using alumina powder with the grain sizes of 1.0 mu m, 0.3 mu m and 0.05 mu m in sequence until the glassy carbon electrode presents a mirror surface;

(b) sequentially using nitric acid, absolute ethyl alcohol and deionized water to carry out ultrasonic treatment on the glassy carbon electrode for 2min so as to clean the surface of the glassy carbon electrode; wherein the volume ratio of the nitric acid to the absolute ethyl alcohol is 1: 1;

(c) and drying the cleaned glassy carbon electrode at normal temperature for later use.

As a further improvement of the above scheme, in the second step, the mass of the gold-doped mesoporous graphite phase carbon nitride nanocomposite in each detection solution is 1mg, and the volume of deionized water is 1 ml; before the suspension is sucked, carrying out ultrasonic treatment on the detection liquid for 2 min; sucking the suspension by a micropipette, wherein the sucking amount of the suspension in each detection liquid is 5 mu L;

In the third step, linear scanning voltammetry is adopted to detect hexavalent chromium; wherein the electrolyte is 0.1M HCl, and the PH value is 1 +/-0.5; in the experimental parameters of the linear sweep, the sweep range was 0.8V to-0.3V and the sweep rate was 100 mV/s.

The invention also provides a gold-doped mesoporous graphite phase carbon nitride nanocomposite, which is prepared by the preparation method of any gold-doped mesoporous graphite phase carbon nitride nanocomposite.

compared with the prior art, the gold-doped mesoporous graphite phase carbon nitride material, and the preparation method and the detection method thereof have the following beneficial effects:

1. The preparation method of the gold-doped mesoporous graphite phase carbon nitride nano composite material comprises the steps of firstly preparing mpg-C₃N₄Passing the material through mpg-C₃N₄the gold-doped mesoporous graphite phase carbon nitride nano composite material is prepared. Dissolving ground dicyandiamide powder in an ethanol aqueous solution to form a first mixed solution, adding a mesoporous molecular sieve into the first mixed solution to form a second mixed solution, performing water bath treatment on the second mixed solution and drying to generate a solid product, heating the solid product in nitrogen, keeping the temperature after the temperature reaches a preset temperature, and thus obtaining the dicyandiamide-containing composite materialGenerating yellow powder, acidifying the yellow powder in hydrofluoric acid to form a mixed solution III, washing the mixed solution III with water and ethanol, and drying to generate mpg-C₃N₄material to facilitate subsequent use. The preparation method is used for generating mpg-C₃N₄after the material is finished, mpg-C is added₃N₄the material is mixed with hexadecyl trimethyl ammonium chloride and placed in deionized water for mixing and stirring to form a mixed solution IV, then a chloroauric acid solution is added into the mixed solution IV and stirred in a dark environment to obtain a mixed solution V, then ultraviolet rays are irradiated on the mixed solution V to form a mixed solution VI, and finally the mixed solution VI is subjected to centrifugation, water washing and drying in sequence to generate the final gold-doped mesoporous graphite-phase carbon nitride nano composite material. The preparation method can prepare the stable gold-doped mesoporous graphite phase carbon nitride nano composite material, namely Au-mpg-C₃N₄A nanocomposite material. Due to mpg-C₃N₄Can prevent gold nanoparticles from agglomerating, and the gold nanoparticles can promote C₃N₄separation of electron-hole pairs, and the like, and the mpg-C is utilized under the condition of ultraviolet light₃N₄the gold nanoparticles are reduced by photocatalysis, so that the gold-doped mesoporous graphite phase carbon nitride nanocomposite prepared by the preparation method can efficiently detect hexavalent chromium in water environment and can conveniently detect trace chromium.

2. The preparation method of the gold-doped mesoporous graphite phase carbon nitride nanocomposite has the advantages of simple whole preparation process, low cost and mass production. Furthermore, the Au-mpg-C prepared by the preparation method₃N₄The nano composite material has excellent conductivity and high electro-catalytic activity, so that the catalytic capability of hexavalent chromium in a solution is improved, the sensitivity of electrochemical detection of hexavalent chromium is further improved, the detection limit is reduced, and the detection capability of hexavalent chromium can be improved.

3. the method for detecting hexavalent chromium in the water environment has the advantages that the linear scanning voltammetry and the chronoamperometry adopted by the method do not have any enrichment process, the detection time is greatly shortened, the effect of quick and accurate detection is achieved, the minimum detection limit of the glassy carbon electrode loaded with the material prepared by the preparation method is 17ppb and is lower than the standard 50ppb of WHO, and the trace hexavalent chromium in the water environment is detected to have high sensitivity (0.0018uA/ppb), so that the sensitivity and the stability of detecting the hexavalent chromium are improved.

Drawings

Fig. 1 is a flowchart of a method for preparing a gold-doped mesoporous graphite-phase carbon nitride nanocomposite according to example 1 of the present invention;

FIG. 2 is a diagram showing the electrochemical response of modified glassy carbon electrodes to hexavalent chromium in the method for detecting hexavalent chromium in an aqueous environment in accordance with embodiment 3 of the present invention;

FIG. 3 is a graph showing a linear relationship between current and detected ions in detection of a modified glassy carbon electrode in a detection method of hexavalent chromium in a water environment according to embodiment 3 of the present invention;

Fig. 4 shows a modified glassy carbon electrode and a bare glassy carbon electrode in a method for detecting hexavalent chromium in a water environment according to embodiment 3 of the present invention, in the presence of Cr (vi): a comparative plot of the effect of current response at 2000 ppb;

FIG. 5 is a Scanning Electron Microscope (SEM) of a portion of the Au-doped mesoporous graphite-phase carbon nitride nanocomposite material according to example 4 of the invention;

FIG. 6 is another Scanning Electron Microscope (SEM) image of a portion of the Au-doped mesoporous graphite-phase carbon nitride nanocomposite material according to example 4 of the invention;

fig. 7 is an EDS energy spectrum of the gold-doped mesoporous graphite phase carbon nitride nanocomposite of example 4 according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.