CN101962537B - Method for preparing (Zn,Cd)S quantum dot - Google Patents

Abstract

The invention relates to a method for preparing a (Zn,Cd)S quantum dot, which comprises the following steps of: (1) dissolving soluble salt of zinc or/and and cadmium and thioacetamide raw materials into water or water-ethanol mixed liquor and adjusting a pH value to weak acidity with weak acid to obtain homogeneous reaction system mother liquor; and (2) transferring the homogeneous reaction system mother liquor obtained in the step (1) into a hydrothermal reactor for automatically generating pressure for sealing, heating to 70-100 DEG C and reacting for 30minutes to 24 hours to obtain the (Zn,Cd)S quantum dot. Compared with the prior art, the invention has the advantages of low cost, controllable process and product property, high uniformity, energy saving, high efficiency, pure water phase preparation and environmental protection.

Description

The preparation method of (Zn, Cd) S quantum dot

Technical field

The invention belongs to the semiconductor nano material preparing technical field, concrete (the Zn that relates to, Cd) Pallution-free preparation method of S and doped quantum dot thereof, particularly a kind ofly take the inorganic zinc source or/and cadmium source and thioacetamide carry out precipitation from homogeneous solution (PFHS) to prepare the method for sulfide and doped quantum dot thereof as raw material, under the reaction conditions of autogenous pressure.

Background technology

Quantum dot (Quantum dots, QDs) be often referred to the semiconductor nanocrystal materials that radius was less than or approached the exciton Bohr radius, it is the aggregate of atom and molecule in the nanoscale scope, general diameter is between 2-20 nm, its yardstick approaches middle-sized protein, than bacterium and little many of biomass cells.Due to electronics and hole, by quantum confinement, continuous energy band structure becomes the discrete energy levels structure with molecular characterization, can emitting fluorescence after being excited.With (Zn, Cd) S quantum dotand hotchpotch is representative II-VI family broad-band gap quantum dot not only has this quantum size effect and good photoluminescent property, and its emmission spectrum makes it have a wide range of applications in biomedical research fields such as biological fluorescent labeling mark, imaging, diagnosis at visible-range.With traditional organic fluorescence molecule, compare, (Zn, Cd) S and doped quantum dot thereof have the exciting light spectrum width, emmission spectrum is symmetric and width is narrow, color is adjustable, photochemical stability is high, be difficult for the significantly superiority such as photodissociation.In addition, (Zn, Cd) S and doped quantum dot thereof can also be applied to photodiode, the hidden and fields such as Emergency Light, high resolution demonstration, solar cell, photochemical catalysis and quantum dot laser.

The preparation method of quantum dot plays decisive role for performance quality and the actual application prospect of quantum dot.Quantum dot is traditional preparation method carry out mostly in organic phase, as the Organometallic Chemistry method (X.G. Peng etc., j. Am. Chem. Soc., 1998,120:5343-5344; j. Am. Chem. Soc., 2001,123:183-184 etc.), the quantum dot that this method prepares water-soluble very poor, aspect bioprobe and biomarker, be difficult to be applied, and this method agents useful for same (raw material is as zinc ethyl, dimethyl cadmium, or solvent is as TOPO/HDA) is expensive, unstable, hypertoxic, inflammable and explosive, with the synthetic quantum dot of this raw material, reaction unit that must be special carry out the step complexity under the exacting terms such as high temperature, anoxybiotic, exhausted water, be difficult to control, pollute also larger.Utilize the hot method of hydrothermal/solvent (J. Li etc., solid State Communications, 2004,130:619-622; H. Zhang etc., adv. Mater.,2003,15 (20): 1712-1715 etc.) prepare the reaction conditions that quantum dot needs high temperature (surpass or approach critical temperature), high pressure (autoclave), to having relatively high expectations of equipment, and particle homogeneity and the lower problem of luminous efficiency also need to solve.The employing precipitator method (R. Vacassy etc., j. Am. Ceram. Soc., 1998,81:2699-2707; Yellow wind China etc., synthetic chemistry, 2004,12:529-531 etc.) and the precipitation process (can complete in several minutes) too rapidly for preparing quantum dot, operability and controllability are poor, and repeatability is not high, and the product particle is easy to reunite, particle diameter is inhomogeneous, affects its luminous efficiency and follow-up use properties.

The method of Chinese invention patent 200310122744.2 disclosed a kind of preparing semiconductor quantum-point material by low-temperature solvents adopts inorganic salt as raw material, short period of time under the lesser temps of 110 ℃ ~ 170 ℃ (3 ~ 60 minutes) can obtain quantum dot, but this method still needs organic solvent as reaction medium.A kind of disclosed method for preparing II-IV type quantum dot and it is carried out to water-soluble conversion of Chinese invention patent 200510120547.6 is modified the quantum dot surface by the measure of surface chemistry, the oil soluble quantum dot carry out water-solubleization, and preparation process is comparatively complicated.Chinese invention patent 200510029928.3 and Chinese invention patent 200910199631.X all disclose a kind of method of synthesizing quantum dot in water, the former is reacted Zn/Cd source and S/Se/Te source in anti-microemulsion, reaches the purpose of regulating quantum dot size by the size of controlling the micro emulsion glue; The latter is reacted cadmium sulfydryl mixture presoma and S/Se/Te source presoma in organic masterplate agent aqueous solution, the size distribution of the micella duct control quantum dot that utilizes the Polymer stencils agent to form.In above-mentioned two kinds of methods, the preparation of anti-microemulsion system or masterplate agent solution is comparatively complicated, and operability and repeatability are not strong, and in preparation process, have large amount of organic discarded, and easy contaminate environment, be unfavorable for realizing industrial mass production.

In sum, although successfully prepare at present various quantum dots report oneself have a lot, how when obtaining high-quality quantum dot, to make preparation process greenization more, low cost, high-level efficiency and be easy to realize that the problem such as productions in enormous quantities still remains further solution.

Summary of the invention

Problem to be solved by this invention is to propose a kind of preparation of (Zn for above-mentioned the deficiencies in the prior art, Cd) method of S quantum dot, thereby can utilize relatively simple raw material, greenization under relatively gentle condition, low cost, high-level efficiency prepare high-quality (Zn, Cd) S quantum dot.

The problem that the present invention is the above-mentioned proposition of solution is adopted solution to be: the preparation method of (Zn, Cd) S quantum dot comprises the steps:

1) take zinc or/and the soluble salt of cadmium and thioacetamide are raw material, and it is dissolved in water or water-ethanol mixed solution, with weak acid for adjusting pH value, to slightly acidic, obtain the homogeneous reaction system mother liquor;

2) step 1) gained homogeneous reaction system mother liquor is transferred in the hydrothermal reaction kettle of autogenous pressure and seals, be heated to 70 ~ 100 ℃, react 30 minutes ~ 24 hours, can obtain (Zn, Cd) S quantum dot.

Press such scheme, in the described raw material of step 1), also be added with foreign cation, described foreign cation is for can replace Zn in (Zn, Cd) S quantum dot ²⁺or Cd ²⁺metallic cation.

Press such scheme, described foreign cation is Mn ²⁺, Mg ²⁺, Cu ²⁺, Ag ²⁺, Al ³⁺, Co ²⁺, Ni ²⁺, Eu ³⁺or Tb ³⁺.

Press such scheme, the described pH value of step 1) is pH=4 ~ 6.

Press such scheme, described zinc is or/and the mol ratio between cadmium and thioacetamide is 1:2～2:1, and all cationic total concn in the homogeneous reaction system mother liquor is 0.01～0.3mol/L.

Press such scheme, described zinc is or/and the mol ratio between cadmium and foreign cation and thioacetamide is 1:2～2:1, and all cationic total concn in the homogeneous reaction system mother liquor is 0.01～0.3mol/L.

Of the present invention is the hydrothermal reaction kettle of autogenous pressure, and its compactedness is 40～90%.

(Zn as above, Cd) preparation method of S and doped quantum dot thereof, can pass through the standing or centrifugal solid-liquid separation of carrying out, again through washing, drying, can obtain (Zn, Cd) powder of S and doped quantum dot thereof, be applied to photodiode, the hidden and fields such as Emergency Light, high resolution demonstration, solar cell, photochemical catalysis and quantum dot laser.

The present invention is usingd thioacetamide as the sulphur source, has utilized thioacetamide to issue the unboiled water solution at certain temperature and acidic conditions and has reacted and generate H ₂the characteristics of S, make Zn ²⁺or Cd ²⁺and foreign cation precipitates with the form of sulfide, reaction equation is:

（1）

（2）

M in formula ²⁺for Zn ²⁺or Cd ²⁺or foreign cation.Under open system, very fast (several minutes to tens minute can complete) that above-mentioned reaction process is carried out, the precipitation of MS easily forms reunion, and a large amount of H are arranged in process ₂the S air release enters air, wastes raw material, reduces productive rate on the one hand, on the other hand air ambient is polluted.The hydrolysis reaction that the present invention is thioacetamide provides the closed environment of an autogenous pressure: work as H ₂after S concentration increases to certain value, MS supersaturation occurs and forms nucleus, now the crystallization of homo(io)thermism, MS and H ₂the release of S is synchronous, and mother liquor system saturation ratio is almost constant, and precipitation process remains on homogeneous system; Compactedness and mother liquid concentration by quantitative adjusting encloses container, MS grows up under controlled condition at the uniform velocity to carry out, can effectively suppress rapid precipitation and the reunion of MS, and can realize easily the control to (Zn, Cd) S and doped quantum dot grain-size thereof by the control to experiment conditions such as reaction times.

The present invention compared with prior art, has the following advantages:

(1) low cost: using inorganic salt cheap and easy to get and thioacetamide as main raw material, significantly reduce the preparation cost of quantum dot;

(2) process and product property are controlled: the characteristics such as airtight, stable, high pressure of utilizing the autogenous pressure reaction system, make the hydrolysis of thioacetamide evenly, slowly, can realize easily the Effective Regulation to quantum dot size and photoluminescent property by the control to reaction conditions, operability and repeatability are stronger;

(3) homogeneity is high: reaction raw materials evenly mixes, and the quantum dot homogeneous nucleation, at the uniform velocity grows up, and easily realizes the Uniform Doped of low concentration doping ion;

(4) efficient energy-saving: the preparation of quantum dot is carried out under the condition of the low temperature below 100 ℃, autogenous pressure, lower to the requirement of equipment and the energy;

(5) prepared mutually by pure water: reaction system is complete water, prepares (Zn, Cd) S quantum dot and doped quantum dot good water solubility thereof, is easy to be applied at aspects such as bioprobe, fluorescent marks;

(6) greenization: reaction system is airtight, and preparation process is without the release of poisonous, obnoxious flavour or liquid with discarded, and environmental friendliness, be easy to realize large-scale commercial production.

The accompanying drawing explanation

The excitation spectrum of ZnS quantum dot when 430nm monitors that Fig. 1 is the embodiment of the present invention 1 preparation;

The emmission spectrum of ZnS quantum dot under 330nm excites that Fig. 2 is the embodiment of the present invention 1 preparation.

Embodiment

Following instance is that the present invention is including but not limited to following instance to the further illustrating of technique of the present invention.

Embodiment 1

With Zn (Ac) ₂2H ₂the O(analytical pure) and C ₂h ₅the NS(analytical pure) be starting raw material, be dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 1:1, and regulate pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.2mol/L.Above-mentioned mixing solutions is transferred to autogenous pressure hydrothermal reaction kettle (stainless steel casing, polytetrafluoroethyllining lining), and compactedness is 75%, is heated to 80 ℃ of isothermal reactions 2 hours, obtains ZnS quantum dot solution after cooling, and the median size of ZnS is 2.3nm.ZnS quantum dot solution is carried out to centrifugation and, with putting into vacuum drying oven after absolute ethanol washing, after 80 ℃ of dryings, can obtain the ZnS quantum dot powder, and its excitation and emission spectra is shown in respectively accompanying drawing 1 and accompanying drawing 2.

Embodiment 2

With ZnCl ₂(analytical pure) and C ₂h ₅the NS(analytical pure) be starting raw material, be dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 1:1.5, and regulate pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.2mol/L.The isothermal reaction time is 3 hours, and other conditions are with embodiment 1.Obtain ZnS quantum dot after cooling, the median size of ZnS is 3.3nm.

Embodiment 3

With Zn (NO ₃) ₂6H ₂the O(analytical pure) and C ₂h ₅the NS(analytical pure) be starting raw material, be dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 1:2, and regulate pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.2mol/L.The isothermal reaction time is 6 hours, and other conditions are with embodiment 1.Obtain ZnS quantum dot after cooling, the median size of ZnS is 6.1nm.

Embodiment 4

With Cd (Ac) ₂2H ₂the O(analytical pure) and C ₂h ₅the NS(analytical pure) be starting raw material, be dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 1:1, and regulate pH value to 5, Cd with Glacial acetic acid ²⁺initial concentration be 0.1mol/L.Other conditions are with embodiment 1.Obtain the CdS quantum dot after cooling, the median size of CdS is 3.1nm.

Embodiment 5

With Zn (Ac) ₂2H ₂the O(analytical pure), Cd (Ac) ₂2H ₂the O(analytical pure) and C ₂h ₅the NS(analytical pure) be starting raw material, be dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 0.9:0.1:1, and regulate pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.18mol/L, Cd ²⁺initial concentration be 0.02mol/L.Other conditions are with embodiment 1.Obtain (Zn after cooling _0.9cd _0.1) the S quantum dot.

Embodiment 6

With Zn (Ac) ₂2H ₂the O(analytical pure), Mn (Ac) ₂4H ₂the O(analytical pure) and C ₂h ₅the NS(analytical pure) be starting raw material, be dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 0.9:0.1:1, and regulate pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.18mol/L, Mn ²⁺initial concentration be 0.02mol/L.Other conditions are with embodiment 1.Obtain ZnS:Mn after cooling ²⁺quantum dot.

Embodiment 7

With Zn (Ac) ₂2H ₂the O(analytical pure), Mg (Ac) ₂4H ₂the O(analytical pure) and C ₂h ₅the NS(analytical pure) be starting raw material, be dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 0.9:0.1:1, and regulate pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.18mol/L, Mg ²⁺initial concentration be 0.02mol/L.Other conditions are with embodiment 1.Obtain ZnS:Mg after cooling ²⁺quantum dot.

Embodiment 8

With Zn (Ac) ₂2H ₂the O(analytical pure), Cu (Ac) ₂h ₂the O(analytical pure) and C ₂h ₅the NS(analytical pure) be starting raw material, be dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 0.9:0.1:1, and regulate pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.18mol/L, Cu ²⁺initial concentration be 0.02mol/L.Other conditions are with embodiment 1.Obtain ZnS:Cu after cooling ²⁺quantum dot.

Embodiment 9

With CdCl ₂(analytical pure), MnCl ₂(analytical pure) and C ₂h ₅the NS(analytical pure) be starting raw material, be dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 0.9:0.1:1, and regulate pH value to 5, Cd with Glacial acetic acid ²⁺initial concentration be 0.09mol/L, Mn ²⁺initial concentration be 0.01mol/L.Other conditions are with embodiment 1.Obtain CdS:Mn after cooling ²⁺quantum dot.

Embodiment 10

With Zn (Ac) ₂2H ₂the O(analytical pure), Cd (Ac) ₂2H ₂the O(analytical pure), Mn (Ac) ₂4H ₂the O(analytical pure) and C ₂h ₅the NS(analytical pure) be starting raw material, be dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 0.8:0.1:0.1:1, and regulate pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.16mol/L, Cd ²⁺initial concentration be 0.02mol/L, Mn ²⁺initial concentration be 0.02mol/L.Other conditions are with embodiment 1.Obtain (Zn after cooling _0.8cd _0.1) S:0.1Mn ²⁺quantum dot.

Claims (3)

1.ZnS the preparation method of quantum dot, comprise the steps:

1) with analytical pure Zn (Ac) ₂2H ₂o and analytical pure C ₂h ₅nS is starting raw material, is dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 1:1, and regulates pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.2mol/L;

2)above-mentioned mixing solutions is transferred to the autogenous pressure hydrothermal reaction kettle, and it is stainless steel casing, polytetrafluoroethyllining lining, and compactedness is 75%, is heated to 80 ℃ of isothermal reactions 2 hours, obtains ZnS quantum dot solution after cooling, and the median size of ZnS is 2.3nm;

3)znS quantum dot solution is carried out to centrifugation and, with putting into vacuum drying oven after absolute ethanol washing, after 80 ℃ of dryings, can obtain the ZnS quantum dot powder.

2.ZnS the preparation method of quantum dot, comprise the steps:

1) with analytical pure ZnCl ₂with analytical pure C ₂h ₅nS is starting raw material, is dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 1:1.5, and regulates pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.2mol/L;

2)above-mentioned mixing solutions is transferred to the autogenous pressure hydrothermal reaction kettle, and it is stainless steel casing, polytetrafluoroethyllining lining, and compactedness is 75%, is heated to 80 ℃ of isothermal reactions 3 hours, obtains ZnS quantum dot solution after cooling, and the median size of ZnS is 3.3nm;

3)znS quantum dot solution is carried out to centrifugation and, with putting into vacuum drying oven after absolute ethanol washing, after 80 ℃ of dryings, can obtain the ZnS quantum dot powder.

3.ZnS the preparation method of quantum dot, comprise the steps:

1) with analytical pure Zn (NO ₃) ₂6H ₂o and analytical pure C ₂h ₅nS is starting raw material, is dissolved into water/alcohol mixeding liquid of 3:1 by the mol ratio of 1:2, and regulates pH value to 5, Zn with Glacial acetic acid ²⁺initial concentration be 0.2mol/L;

2)above-mentioned mixing solutions is transferred to the autogenous pressure hydrothermal reaction kettle, and it is stainless steel casing, polytetrafluoroethyllining lining, and compactedness is 75%, is heated to 80 ℃ of isothermal reactions 6 hours, obtains ZnS quantum dot solution after cooling, and the median size of ZnS is 6.1nm;

3)znS quantum dot solution is carried out to centrifugation and, with putting into vacuum drying oven after absolute ethanol washing, after 80 ℃ of dryings, can obtain the ZnS quantum dot powder.

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