A cadmium sulfide quantum dot modified titanium dioxide and preparation method thereof

Abstract

The invention discloses a cadmium sulfide quantum dot modified titanium dioxide and a preparation method thereof, and belongs to the field of photocatalysis technology. The preparation method of cadmium sulfide quantum dot modified titanium dioxide comprises the following steps: (1) uniformly mixing an organic sulfur source, a modifier and a stabilizer, then adding a cadmium source and mixing and heating to obtain surface-modified cadmium sulfide quantum dots; (2) under ice-water bath conditions, dropping a mixed solution of surface-modified cadmium sulfide quantum dots and an organic solvent into a mixed solution of a titanium source and an acid solution, stirring continuously during the dropping process until precipitation occurs, and obtaining cadmium sulfide quantum dot modified titanium dioxide after centrifugation. The present invention prepares cadmium sulfide quantum dot modified titanium dioxide (titanium dioxide loaded with cadmium sulfide quantum dot nanomaterial) in situ under normal temperature aqueous phase conditions without the need for additional heating.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalysis, and in particular to cadmium sulfide quantum dot-modified titanium dioxide and a preparation method thereof. Background Art

[0002] Formaldehyde is identified by the World Health Organization as a carcinogenic gas in indoor environments. Various artificial boards, decorative materials, interior wall coatings and other coatings used in large quantities in decoration and furniture will gradually release a large amount of free formaldehyde. Acute formaldehyde poisoning manifests itself as irritation to the skin and mucous membranes. Inhalation of high concentrations of formaldehyde can lead to respiratory irritation symptoms, sneezing, coughing, and a burning sensation in the nose and throat; in addition, it can also induce bronchial asthma, pneumonia, and pulmonary edema; a large amount of formaldehyde ingested through the digestive tract at one time can cause digestive and systemic toxic symptoms, corrosive burns of the mouth, throat, and digestive tract, abdominal pain, convulsions, death, etc.; skin contact with formaldehyde can cause allergic dermatitis, pigmentation, skin necrosis and other lesions; oral ingestion of 10 to 20 mL of formaldehyde solution can be fatal.

[0003] Formaldehyde is a representative substance of organic pollutants and the main substance of indoor air pollution. Effective methods for purifying formaldehyde are being studied both at home and abroad. Photocatalytic oxidation technology can completely decompose organic pollutants into inorganic substances such as water and carbon dioxide, so it has been applied and studied in the purification of formaldehyde. 2 It has become the most popular photocatalyst due to its excellent properties, such as high stability, low cost and environmental friendliness. 2 The main disadvantage of anatase TiO 2 The bandgap width of TiO is large (3.2 eV), and the photocatalytic oxidation process can be stimulated only in the ultraviolet region, while ultraviolet light accounts for only 3-5% of the solar spectrum, which seriously hinders the development of TiO 2 In recent years, in order to improve the utilization rate of solar energy, TiO 2 The photocatalytic activity of TiO 2 A lot of research has been done on semiconductor modification and surface modification, but there are still problems such as harsh preparation conditions and easy environmental pollution. How to achieve green, simple and efficient preparation of high-performance composite materials for photocatalytic purification of formaldehyde has become a technical problem that technicians in this field need to solve urgently. Summary of the invention

[0004] The purpose of the present invention is to provide a cadmium sulfide quantum dot modified titanium dioxide and a preparation method thereof, so as to solve the problems existing in the prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: a method for preparing cadmium sulfide quantum dot-modified titanium dioxide, comprising the following steps:

[0007] (1) mixing an organic sulfur source and a modifier to obtain a mixture, then adding (22.8 to 100 mg) a cadmium source, mixing, and heating to obtain cadmium sulfide quantum dots with modified surfaces (cadmium sulfide quantum dots);

[0008] (2) Under ice-water bath conditions, a mixed solution of surface-modified cadmium sulfide quantum dots and an organic solvent is added dropwise to a mixed solution of a titanium source and an acid solution (excess), and the mixture is continuously and rapidly stirred (500-600 r / min) during the addition process until precipitation occurs. Finally, the cadmium sulfide quantum dot-modified titanium dioxide is obtained after centrifugation, washing, and drying.

[0009] Under aqueous conditions, cadmium sulfide quantum dots and titanium dioxide are in situ composited to achieve the modification effect of cadmium sulfide quantum dots on titanium dioxide.

[0010] Furthermore, in step (1), the organic sulfur source is an extract of Allium plants; and the modifier is an extract of starch-containing plants.

[0011] Furthermore, the preparation of the Allium family plant extract specifically includes: chopping the Allium family plant, adding water, heating and boiling, maintaining for 30 minutes, filtering and removing impurities, and obtaining the Allium family plant extract;

[0012] The preparation of the starch-containing plant extract specifically includes: chopping the starch-containing plant, adding water, heating and boiling, keeping for 30 minutes, filtering to remove impurities, standing for 1 day, and collecting the supernatant as the starch-containing plant extract.

[0013] The use of starch-containing plant extracts as modifiers and stabilizers, and the use of Allium plant extracts as sulfur sources greatly reduced the harm of raw materials to the human body and the environment during the synthesis of cadmium sulfide quantum dots. Subsequently, by introducing an aqueous phase system (aqueous solution of cadmium sulfide quantum dots with modified surfaces), the hydrolysis of butyl titanate was greatly inhibited under the conditions of excessive acetic acid and ice water bath, thereby achieving in-situ recombination of cadmium sulfide quantum dots and titanium dioxide.

[0014] Environmentally friendly plant extracts are used as raw materials because they contain a variety of functional groups with modification effects (carboxyl, amino, thiol and other functional groups), and the starch in the extract can provide a colloid-like environment for material synthesis, which is more conducive to material synthesis. At the same time, the use of plant extracts can reduce the cost of synthetic materials, environmental pollution and harm to the human body.

[0015] Furthermore, the Alliumaceae plant includes any one of garlic, shallot and onion; the starch-containing plant includes any one of potato, purple sweet potato, yam, taro, sweet potato and lotus root.

[0016] Furthermore, in step (1), the cadmium source is an organic salt of cadmium metal and / or an inorganic salt of cadmium metal; the heating treatment is a steam sterilization treatment; the temperature of the steam sterilization treatment is 121° C. and the time is 20 min.

[0017] Furthermore, the cadmium source is cadmium chloride, cadmium sulfate or cadmium acetate.

[0018] Furthermore, in step (2), the organic solvent is anhydrous ethanol; the titanium source is butyl titanate; the acid solution is acetic acid solution; and the mole / volume ratio of the titanium source and the acid solution is 10-30 mmol: 50-150 mL.

[0019] Furthermore, in step (2), the molar percentage of cadmium in the surface-modified cadmium sulfide quantum dot aqueous solution and titanium in the titanium source is 0.1% to 10%.

[0020] The second technical solution of the present invention: a cadmium sulfide quantum dot-modified titanium dioxide prepared by the above-mentioned preparation method of cadmium sulfide quantum dot-modified titanium dioxide.

[0021] Technical solution three of the present invention: an application of the above-mentioned cadmium sulfide quantum dot-modified titanium dioxide in catalytic degradation of organic matter.

[0022] The present invention discloses the following technical effects:

[0023] (1) The present invention prepares titanium dioxide-supported cadmium sulfide quantum dot nanomaterials (cadmium sulfide quantum dot-modified titanium dioxide) in situ under normal temperature aqueous phase conditions. The hydrolysis of butyl titanate is suppressed by an excess of weak acid and an ice-water bath, and the prepared surface-modified cadmium sulfide quantum dot aqueous solution is slowly added dropwise to the titanium dioxide synthesis process without additional heating, thereby preparing titanium dioxide-supported cadmium sulfide quantum dot nanomaterials in situ.

[0024] (2) In the process of preparing cadmium sulfide quantum dots, the toxicity to the environment and human body is reduced from the raw materials. Except for cadmium metal salts, all synthetic raw materials use natural plant extracts as raw materials, and the extracts of starch-containing plants are used as stabilizers and modifiers to replace traditional chemical surfactants and modifiers; the extracts of Allium plants are used as sulfur sources to replace traditional organic / inorganic sulfur sources. A surface-modified and well-dispersed cadmium sulfide quantum dot aqueous solution is prepared.

[0025] (3) The synthesis temperature and conditions of the present invention are relatively loose and not harsh, and the synthesis and modification can be completed in one step. The traditional synthesis method of titanium dioxide is the sol-gel method, which requires two steps, namely the sol-gel process and the heating synthesis process. The present invention directly synthesizes titanium dioxide in situ under aqueous conditions, adds a cadmium sulfide quantum dot aqueous solution during the synthesis process, and completes the in-situ composite of titanium dioxide loaded with cadmium sulfide quantum dot nanomaterials without the need for an additional heating step. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 The TEM image and solution color image of cadmium sulfide quantum dots prepared in Example 1 of the present invention, wherein (a) is a TEM image and (b) is a solution color image;

[0028] Figure 2 TEM image of cadmium sulfide quantum dot-modified titanium dioxide prepared in Example 1 of the present invention;

[0029] Figure 3 The CdS-TiO prepared in Example 1 and Comparative Example 1 of the present invention 2 and unmodified TiO 2 Comparison chart of the effect of formaldehyde degradation;

[0030] Figure 4 This is a comparison chart of the degradation rates of formaldehyde by photocatalytic degradation of titanium dioxide modified with cadmium sulfide quantum dots prepared in Examples 1 to 4 of the present invention. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0033] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0034] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] Example 1

[0037] A preparation method of cadmium sulfide quantum dot modified titanium dioxide:

[0038] (1) Low-toxicity preparation of cadmium sulfide quantum dots:

[0039] A. Preparation of starch-containing plant extract: Weigh 100 g of potato tubers, cut into small pieces, place in a 2 L beaker, add 1 L of deionized water, heat to boiling and start timing for 30 minutes, then stop heating, filter out coarse impurities through ten layers of gauze and let stand in a refrigerator for 1 day, collect the supernatant which is the starch-containing plant extract.

[0040] B. Preparation of the extract of Allium family plants: Weigh 500g of peeled garlic, cut into small pieces, place in a 2L beaker, add 1L of deionized water, heat to boiling and start timing for 30 minutes, then stop heating, filter out coarse impurities through ten layers of gauze, let stand for 2h and take the supernatant, which is the extract of Allium family plants.

[0041] C. Stir and mix 500 mL of the starch-containing plant extract and 500 mL of the Allium plant extract, and add 22.8 mg of hydrated cadmium chloride (CdCl 2 2.5H 2 O), stirring and mixing to obtain a mixture, placing the mixture in a steam sterilizer, reacting at 121° C. for 20 min, and cooling to room temperature to obtain a surface-modified cadmium sulfide quantum dot aqueous solution (TEM image of cadmium sulfide quantum dot CdS and solution color image are shown in FIG. Figure 1 ).

[0042] (2) Preparation of cadmium sulfide quantum dots modified titanium dioxide (in-situ synthesis in aqueous phase):

[0043] A. Add 34 mL of butyl titanate (10 mmol) and 50 mL of acetic acid into a beaker and mix to obtain a mixed solution I.

[0044] B. Take out the surface-modified cadmium sulfide quantum dot aqueous solution prepared in step (1) at a molar ratio of cadmium to titanium of 5‰ (the molar ratio of cadmium in the surface-modified cadmium sulfide quantum dot aqueous solution to titanium in the mixed solution A is 5‰) and mix it with 300 mL of anhydrous ethanol to obtain a mixed solution II.

[0045] C. In an ice-water bath, the mixed solution II was slowly added to the mixed solution I using a syringe, and the mixture was stirred rapidly (500-600 r / min) during the addition process until precipitation occurred. Finally, the mixture was centrifuged, washed, and dried in an oven at 80°C for 12 h to obtain a cadmium sulfide quantum dot modified titanium dioxide powder material (CdS-TiO 2 , the loading amount of cadmium sulfide quantum dots is 5‰), the TEM image of cadmium sulfide quantum dots modified titanium dioxide is shown in Figure 2 .

[0046] Comparative Example 1

[0047] Preparation of CdS-TiO by Sol-Gel Method 2 :

[0048] First, 34 mL of butyl titanate was mixed with 300 mL of ethanol to form solution A; cadmium sulfide quantum dots (prepared by the same method as in Example 1) were mixed with 300 mL of ethanol to form solution B; the pH of solution B was adjusted to 1 with nitric acid, and then solution A was added dropwise to solution B in a rapidly stirred state (speed 500-600 r / min) to obtain CdS-TiO 2 The gel was then poured into a watch glass, placed in an oven, and aged at 80°C to obtain CdS-TiO 2 Material.

[0049] Effect Example 1

[0050] The CdS-TiO prepared in Example 1 (method of the present invention) and Comparative Example 1 (sol-gel method) were 2 and unmodified TiO 2 Used for photocatalytic degradation of formaldehyde at a concentration of 10 mg / L and record the degradation rate. The results are shown in Figure 3 .

[0051] from Figure 3 It can be seen that after modification, CdS-TiO 2The degradation effect of (prepared in Example 1) is better than that of unmodified TiO 2 (Comparative Example 1) Among the two modification methods, the degradation effect of the method of the present invention on formaldehyde is significantly better than that of CdS-TiO prepared by the traditional sol-gel method. 2 , 15 minutes after the reaction started, the degradation rates reached 75% (sol-gel method) and 90% (method of the present invention) respectively; after 45 minutes of reaction, the CdS-TiO prepared by the method of the present invention 2 The degradation rate of formaldehyde reached 98%. The CdS-TiO prepared by the sol-gel method 2 The degradation rate of formaldehyde is only 85%, which proves that the cadmium sulfide quantum dot modified titanium dioxide prepared by the method of the present invention has good photocatalytic performance.

[0052] Example 2

[0053] Same as Example 1, except that the molar ratio of cadmium to titanium is 1‰.

[0054] Example 3

[0055] Same as Example 1, except that the molar ratio of cadmium to titanium is 1%.

[0056] Example 4

[0057] Same as Example 1, except that the molar ratio of cadmium to titanium is 5%.

[0058] Effect Example 2

[0059] The CdS-TiO prepared in Examples 1 to 4 2 Used for photocatalytic degradation of formaldehyde at a concentration of 10 mg / L and record the degradation rate. The results are shown in Figure 4 .

[0060] from Figure 4 It can be seen that the cadmium-titanium molar ratio with the best formaldehyde degradation effect is the ratio in Example 1, that is, the cadmium-titanium molar ratio is 5‰, and the final formaldehyde degradation efficiency is 99%, close to 100%.

[0061] Comparative Example 2

[0062] Same as Example 1, except that the extract of the Allium family plant is replaced with thioacetamide.

[0063] The performance of the prepared cadmium sulfide quantum dot-modified titanium dioxide is comparable to that of Example 1.

[0064] Comparative Example 3

[0065] Replacing the starch-containing plant extract with an ordinary starch solution cannot produce an aqueous solution of cadmium sulfide quantum dots.

[0066] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing cadmium sulfide quantum dot modified titanium dioxide, characterized in that: The following steps are involved: (1) mixing an organic sulfur source and a modifier evenly, then adding a cadmium source, mixing, and heating to obtain cadmium sulfide quantum dots with modified surfaces; (2) under ice water bath conditions, adding a mixed solution of surface-modified cadmium sulfide quantum dots and an organic solvent dropwise to a mixed solution of a titanium source and an acid solution, stirring continuously during the adding process until precipitation occurs, and obtaining the cadmium sulfide quantum dot-modified titanium dioxide after centrifugation; In step (1), the organic sulfur source is an extract of Allium plants; the modifier is an extract of starch-containing plants; In step (2), the organic solvent is anhydrous ethanol; the titanium source is butyl titanate; the acid solution is acetic acid solution; the mole / volume ratio of the titanium source and the acid solution is 10-30 mmol: 50-150 mL; In step (2), the molar percentage of cadmium in the aqueous solution of the surface-modified cadmium sulfide quantum dots and titanium in the titanium source is 0.1% to 1%.

2. The method for preparing cadmium sulfide quantum dot modified titanium dioxide according to claim 1, characterized in that: The preparation of the Allium family plant extract specifically comprises: chopping the Allium family plant, adding water, heating and boiling, maintaining for 30 minutes, filtering and removing impurities, and obtaining the Allium family plant extract; The preparation of the starch-containing plant extract specifically includes: chopping the starch-containing plant, adding water, heating and boiling, keeping for 30 minutes, filtering to remove impurities, standing for 1 day, and collecting the supernatant as the starch-containing plant extract.

3. The method for preparing cadmium sulfide quantum dot modified titanium dioxide according to claim 2, characterized in that: The Alliumaceae plant includes any one of garlic, shallot and onion; the starch-containing plant includes any one of potato, purple sweet potato, yam, taro, sweet potato and lotus root.

4. The method for preparing cadmium sulfide quantum dot modified titanium dioxide according to claim 1, characterized in that: In step (1), the cadmium source is an organic salt of cadmium metal and / or an inorganic salt of cadmium metal; the heating treatment is a steam sterilization treatment; the temperature of the steam sterilization treatment is 121° C. and the time is 20 min.

5. The method for preparing cadmium sulfide quantum dot modified titanium dioxide according to claim 4, characterized in that: The cadmium source is cadmium chloride, cadmium sulfate or cadmium acetate.

6. Cadmium sulfide quantum dot-modified titanium dioxide prepared by the method for preparing cadmium sulfide quantum dot-modified titanium dioxide according to any one of claims 1 to 5.

7. Use of the cadmium sulfide quantum dot-modified titanium dioxide as claimed in claim 6 in photocatalytic degradation of organic matter.

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