Background technology
(Quantum Dots QDs) can be described as semiconductor nanocrystal (Semicondutor Nanocrystal) again to quantum dot, is a kind of by the elementary composition nano particle of II-VI family or III-V family.Compare with traditional organic fluorescent dye, quantum dot has extremely good spectrum property, and is wide as excitation wavelength range, and emission wavelength ranges is narrow, and Stokes shift is big, and fluorescence lifetime is long, is difficult for advantages such as photobleaching, caused people's extensive concern.Particularly water miscible quantum dot has shown extremely wide application prospect in research fields such as biological chemistry, cytobiology, molecular biology.Yet the preparation method of quantum dot is many based on organic synthesis, and what obtain is fat-soluble product, serious obstruction the application of quantum dot in the biological study field.At this problem, the scientific research personnel has launched number of research projects, in numerous solutions, quantum dot is carried out the silanization processes and displays gone out more and more many advantages: (1) is based on surface silicon alkanisation modifying method, can be very convenient, the silicon shell type quantum dot is carried out the connection of chemical groups such as the modification of hydrophilic radical and amino efficiently, and then can be coupled with biomolecules such as DNA, protein, for its Biology Applications has been established solid basis; (2) the surface silicon web frame has greatly stoped entering of oxygen molecule, makes the anti-photobleaching performance of quantum dot significantly improve; (3) the silicon shell can effectively reduce Cd2+Etc. leaking of heavy metal ion, the biocompatibility of quantum dot is further improved.As people such as Alivisatos (Science, 1998,281 (5385): 2013～2016) prepare the silicon shell type quantum dot fluorescence nano particle that has than high light stability indirectly by the method for using follow-up silanization, promptly at first prepare fat-soluble quantum dot and centrifugal purification, utilize 3-(sulfydryl propyl group) Trimethoxy silane (MPS) trioctylphosphine oxide that it is surperficial (TOPO) to replace then, again solution is adjusted to alkalescence, make methoxy silane hydrolysis and dehydrating condensation, thereby formed the shell that one deck has silica/silicon oxygen alkane on the surface of quantum dot, further can react (as: TSL 8330 etc.) with some bifunctional methoxylation compounds, make its surface be with chemical groups such as amino, finally realized coupled with biomolecules.(Nano Letters such as Schroedter, 2002,2 (12): 1363～1367) at first adopt water synthetic method to prepare the water-soluble quantum dot that pan coating has mercaptoethylamine, add NaOH solution and Virahol then and carry out centrifugal treating, with removing the free mercaptoethylamine, then adopt MPS with the mercaptoethylamine displacement of coordination at particle surface, the one-step hydrolysis of going forward side by side becomes shell, thereby has obtained the silicon shell type quantum dot fluorescence nano particle of stable existence.Although adopt aforesaid method can prepare the quantum dot fluorescence nano particle of silicon shell bag quilt indirectly, but preparation method's complexity, tediously long steps such as the preparation of needs process quantum dot, centrifugally operated, MPS exchange, silanization processing, and multistep is handled and is caused productive rate to reduce, thereby has limited its further development and applied research.Therefore develop a kind of simple to operately, the silicon shell style CdTe quanta point preparation method that productive rate is high then is the gordian technique that silicon shell type quantum dot fluorescence nano particle Application Areas constantly enlarges.
Summary of the invention
The objective of the invention is to deficiency and defective at above-mentioned preparation method, provide a kind of easy and simple to handle, mild condition directly prepares the method for silicon shell type CdTe quantal-point, to solve the problem that indirect technology of preparing exists.
The technical scheme that realizes above-mentioned purpose is:
The direct preparation method of silicon shell type CdTe quantal-point is for feeding high pure nitrogen in methyl alcohol that contains cadmium salt or tetrahydrofuran solution, 3-(sulfydryl propyl group) Trimethoxy silane that adds 0.005～0.05M then feeds by sulfuric acid and Al under logical nitrogen of continuation and stirring condition2Te3The H that reaction generates2Te gas was removed later on nitrogen in 10 minutes, and under 65～70 ℃ condition reflux 8～15 minutes, obtain MPS coordinate CdTe quantum dot; The pH value that adds tetramethylphosphonihydroxide hydroxide amine regulator solution again is 8.0～8.5, continues to reflux 30～40 minutes, promptly obtains the silicon shell type CdTe quantal-point fluorescent nano particle.
Used cadmium salt is: cadmium perchlorate, Cadmium Sulphate, cadmium iodate, cadmium acetate, cadmium chlorate, cadmium nitrate or Cadmium chloride fine powder.The mol ratio of Cd and Te is 1: (0.2～0.4), wherein the volumetric molar concentration of Cd is 1.0～2.5mM, the volume of methyl alcohol or four nitrogen furans is 50～300ml.
Be described in further detail the present invention below:
The direct preparation of silicon shell type CdTe quantal-point comprises the steps:
1, the preparation of CdTe quantum dot
The methyl alcohol or the tetrahydrofuran solution deoxidation that will contain cadmium salt with nitrogen are protected, and add the 3-that concentration is 0.005～0.05M (sulfydryl propyl group) Trimethoxy silane (MPS) then, are continuing to feed sulfuric acid and Al under logical nitrogen and the stirring condition2Te3The H that reaction generates2Te gas was removed nitrogen later in 10 minutes and was begun heating, refluxed 8～15 minutes down in 65～70 ℃, obtained MPS coordinate CdTe quantum dot.
Cadmium salt of the present invention can be selected any in cadmium perchlorate, Cadmium Sulphate, cadmium iodate, cadmium acetate, cadmium chlorate, cadmium nitrate, the Cadmium chloride fine powder for use.
The mol ratio of Cd and Te is 1 among the present invention: (0.2～0.4), wherein the volumetric molar concentration of Cd is 1.0～2.5mM, the volume of methyl alcohol or tetrahydrofuran (THF) is 50～300mL.
2, the formation of surface silicon web frame
With tetramethylphosphonihydroxide hydroxide amine the pH value of above-mentioned solution is adjusted to 8.0～8.5, methoxyl group on the MPS begins to be hydrolyzed to hydroxyl, continue 30～40 minutes original position dehydrating condensations that reflux, thereby form fine and close silicon net, directly obtained the silicon shell type CdTe quantal-point fluorescent nano particle on the quantum dot surface.
The present invention is coordination agent with MPS, under the experiment condition of gentleness, has directly prepared the silicon shell type CdTe quantal-point fluorescent nano particle first, has following advantage:
One: this method experimental installation is simple, processing ease, need not harsh experiment conditions such as High Temperature High Pressure, can directly obtain pan coating has the CdTe quantum dot fluorescence nano particle of silicon shell, complex steps such as MPS exchange have been save, make the preparation method simple and easy to do, and can further be applied to the preparation of the other types quantum dot of silicon shell bag quilt.
Its two: this particle monodispersity is good, and homogeneity is strong, and can be used as a kind of novel uv materials, is applied to research fields such as laser apparatus, photodiode, sensitive materials.
Its three: the existence of surface silicon web frame, improved the anti-photobleaching performance of quantum dot greatly, help carrying out the long-term spike and the observation of protein and other.
Its four: based on surface silicon alkanisation modifying method, rely on the silica shell structure of the quilt that wraps, be expected to convenient, efficiently particle is further processed, make it be with functionalization groups such as amino, carboxyl, phosphate according to demand, thereby for the connection of biomolecules such as protein has brought convenience, for biomedical research provides a kind of effective instrument.
Embodiment
Below the invention will be further described by several specific exampless:
Embodiment one
The preparation of silicon shell type CdTe quantal-point:
Take by weighing Cd (ClO4)26H2O 100mg places three-necked flask, adds 100mL methyl alcohol, feeds high pure nitrogen then, with the oxygen that removes in the solution.In solution, add 0.715mL MPS, under stirring condition, feed the H of prepared fresh2Te gas is (by the Al of 13.9mg2Te3H with 0.5mol/L2SO4Reaction generates), stop ventilation afterwards, 65 ℃ of following reflux 10 minutes transfer to 8.0 and continue to reflux 40 minutes with tetramethylammonium hydroxide with reacting liquid pH value, thereby have directly prepared the quantum dot fluorescence nano particle that pan coating has the silicon shell.
Embodiment two
The preparation of silicon shell type CdTe quantal-point:
Take by weighing Cd (AC)22H2O 63.5mg places three-necked flask, adds the 100mL tetrahydrofuran (THF), feeds high pure nitrogen then, with the oxygen that removes in the solution.In solution, add 1mL MPS, under stirring condition, feed the H of prepared fresh2Te gas is (by 15mg Al2Te3H with 0.5mol/L2SO4Reaction generates), stop ventilation afterwards, 70 ℃ of following reflux 10 minutes transfer to 8.5 and continue to reflux 30 minutes with tetramethylammonium hydroxide with reacting liquid pH value, thereby have directly prepared the quantum dot fluorescence nano particle that pan coating has the silicon shell.
Embodiment three
The preparation of silicon shell type CdTe quantal-point:
Take by weighing Cd (ClO4)26H2O 41.9mg places three-necked flask, adds 100mL methyl alcohol, feeds high pure nitrogen then, with the oxygen that removes in the solution.In solution, add 0.625mL MPS, under stirring condition, feed the H of prepared fresh2Te gas is (by 4.25mg Al2Te3H with 0.5mol/L2SO4Reaction generates), stop ventilation afterwards, 65 ℃ of following reflux 12 minutes transfer to 8.0 and continue to reflux 40 minutes with tetramethylammonium hydroxide with reacting liquid pH value, thereby have directly prepared the quantum dot fluorescence nano particle that pan coating has the silicon shell.
According to the method for the invention, can directly prepare the other types quantum dot of silicon shell bag quilt.