Background technology
In recent years, II-VI family semiconductor nanorods is because its excellent optical property, still all caused the great interest of people from angle of practical application from the angle of fundamental research.The CdS nanometer rod has the potential extensive use as a kind of important II-VI family semiconductor material at aspects such as light emitting diode (LEDs), solar cell, device for non-linear optical and photochemical catalysis.Because magnetic ion is (as Mn
2+, Co
2+) have a very strong local spin magnetic moment, there is strong spin-spin exchange interaction between the local magnetic moment of magnetic ion and the valence band electronics, make the adulterated semiconductor nanorods of magnetic ion have a series of and the distinct characteristic of general semiconductor, as huge Faraday effect, big exciton division, huge Zeeman splitting etc., show unusual magnetics, electricity, optical property and many new physical influences; Therefore, become the main direction of present research with magnetic ion doping CdS nanometer rod.
Mn
2+Ion and Cd
2+The ionic electric charge equates that ionic radius is similar to (differing about 10%), can not produce bigger influence to lattice so the Mn ion can mix the CdS lattice preferably.The report of early stage Mn doping CdS nanometer rod adopts coprecipitation method more, but the resulting nanocrystalline more defective that exists only has a small amount of Mn ion to enter intracell, and most of Mn ion is attached to nanocrystal surface or form the MnS precipitation.Adopt chemical gaseous phase depositing process to prepare the adulterated CdS nanometer rod of Mn in addition, this method not only needs main equipment and its preparation temperature height, and because the Mn ionic mixes, the nanocrystalline fluorescence lifetime of CdS significantly reduces (reduces to 20~30ps) from 590ps.Though adopt high temperature pyrolytic cracking (HTP) can prepare high-quality Mn doping CdS nanometer rod, the condition harshness must satisfy: the monomer concentration that (1) is high simultaneously; (2) high temperature of reaction (>300 ℃) and high stirring velocity; (3) utilization structure directed agents and two or more tensio-active agents, and reaction must be carried out under the condition of anhydrous and oxygen-free.
The Co that compares with the Mn ion has stronger magnetic couplings effect, the nanocrystalline of Co ion doping may produce new magneto-optic effect, (the Co ionic radius is 0.074nm but owing to the bigger lattice match difference of interionic, the Cd ionic radius is 0.097nm) and the high-ratio surface effect of nano material, make the Co ion be difficult to realize in the doping of the nanocrystalline intracell of CdS.Adopt coprecipitation method or reverse micelle method to prepare the adulterated CdS nanometer rod of Co, the Co ion is mainly attached to nanocrystal surface, and do not form uniform nanometer rod.Recently, it is nanocrystalline that Ogale and colleague thereof adopt pulse high-energy electron induced reaction to prepare the adulterated CdS of Co, but this method needs special equipment, and preparation is complicated, and the pattern of product and optical property are restive.
Summary of the invention
The invention provides the preparation method of magnetic element (Co, Mn) doping CdS nanometer rod, adopt to contain cadmium sulphur inorganic molecule bunch ((Me
4N)
4[S
4Cd
10(SPh)
16]) with the precursor of magnetic element directly in high boiling solvent pyrolysis synthetic, solved magnetic element doping CdS nanometer rod severe reaction conditions, need specific installation, problem such as preparation is complicated, and the pattern of product and optical property are restive.Method provided by the invention is simple, be easy to control, and the reaction times is short, has the solvent alternative, is fit to the adulterated CdS nanometer rod of a large amount of preparation magnetic element.
Magnetic element Co doping CdS nanometer rod of the present invention prepares by following step:
One, with high boiling solvent vacuum outgas 2 hours under 120 ℃ of conditions, will be cooled to 60 ± 3 ℃ then, and carry out reflux under argon gas atmosphere, the reflux temperature rise rate is 1.0 ℃/min, and system is warming up to 60~100 ℃ and adds (Me
4N)
4[S
4Cd
10(SPh)
16] powder, the system of the treating muddy shape that is creamy white adds (Me again
4N)
2[Co
4(SC
6H
5)
10] powder, system is the turbid shape of color contamination darkly; Two, continue to keep the temperature rise rate of 1.0 ℃/min to be heated to 200 ℃~280 ℃ and be incubated 0.5~1 hour, naturally cool to 60 ℃ afterwards, and add anhydrous methanol and precipitate with centrifugal, the solid formation that obtains precipitates centrifugal 2 times with anhydrous methanol once more; Three, the solid formation that step 2 is obtained is dissolved in toluene, adds the anhydrous methanol centrifugation again, and vacuum-drying obtains the CdS:Co nanometer rod powder of high boiling solvent surface coverage then; Four, carry out the surface ligand exchange with pyridine, promptly obtain magnetic element Co doping CdS nanometer rod; (Me in the step 1 wherein
4N)
4[S
4Cd
10(SPh)
16] add-on of powder is 1/20~1/40 of high boiling solvent quality; (Me in the step 1
4N)
2[Co
4(SC
6H
5)
10] add-on of powder is (Me
4N)
4[S
4Cd
10(SPh)
16] powder quality 1/3~1/5.
Magnetic element Mn doping CdS nanometer rod of the present invention prepares by following step:
One, with high boiling solvent vacuum outgas 2 hours under 120 ℃ of conditions, will be cooled to 60 ± 3 ℃ then, and carry out reflux under argon gas atmosphere, the reflux temperature rise rate is 1.0 ℃/min, and system is warming up to 60~100 ℃ and adds (Me
4N)
4[S
4Cd
10(SPh)
16] powder, the system of the treating muddy shape that is creamy white adds MnCl again
2Powder, system be the turbid shape of color contamination darkly; Two, continue to keep the temperature rise rate of 1.0 ℃/min to be heated to 200 ℃~250 ℃ and be incubated 0.5~1 hour, naturally cool to 60 ℃ afterwards, and add anhydrous methanol and precipitate with centrifugal, the solid formation that obtains precipitates centrifugal 2 times with anhydrous methanol once more; Three, the solid formation that step 2 is obtained is dissolved in toluene, adds the anhydrous methanol centrifugation again, and vacuum-drying obtains the CdS:Co nanometer rod powder of high boiling solvent surface coverage then; Four, carry out the surface ligand exchange with pyridine, promptly obtain magnetic element Co doping CdS nanometer rod; (Me in the step 1 wherein
4N)
4[S
4Cd
10(SPh)
16] add-on of powder is 1/20~1/40 of high boiling solvent quality; MnCl in the step 1
2The add-on of powder is (Me
4N)
4[S
4Cd
10(SPh)
16] powder quality 1/2~1/5.
During the turbid shape of color contamination, system temperature will reduce about 5 ℃ system darkly in preparation method's step 1 of magnetic element doping CdS nanometer rod of the present invention.Centrifugal in preparation method's step 2 of magnetic element doping CdS nanometer rod of the present invention with the anhydrous methanol repeated precipitation, can be with the Impurity removal that produces in the reaction process.
The inventive method is with containing cadmium sulphur inorganic molecule bunch ((Me
4N)
4[S
4Cd
10(SPh)
16]) with the precursor ((Me of cobalt
4N)
2[Co
4(SC
6H
5)
10]) or the precursor (MnCl of manganese
2) between ion-exchange character, directly pyrolysis realizes the CdS nanometer rod of magnetic element ion doping in high boiling solvent (as hexadecylamine, trioctylphosphine oxide (TOPO) or oleic acid), has operational safety, easy, advantage that cost is low; And can carry out the synthetic of heavy dose of CdS nanometer rod.Owing to be reflected in the single solvent system and carry out, need not template or main equipment, and be easy to separate purification; And the reaction conditions gentleness does not produce obnoxious flavour in the reaction process.
The high boiling solvent that uses in the inventive method (as hexadecylamine, trioctylphosphine oxide (TOPO) or oleic acid) need not purified, price is low, can form coating layer in nanorod surfaces, avoid being dissolved under the precursor high temperature of magnetic element the problem of solvent, needn't use vacuum line equipment and glove box.
Quantum dot is the nano material of accurate zero dimension (quasi-zero-dimensional), is made of a spot of atom; Can be described as nanocrystallinely again, is a kind of by the elementary composition nano particle of II-VI family or III-V family.The particle diameter of quantum dot one between 1~10nm.Nanometer rod belongs to monodimension nanometer material, and one is meant the solid nano material of length one dimension short, that vertically form is more straight cylindric (or its cross section becomes cerioid).Different formation conditions is arranged between the quantum dot of same material and the nanometer rod.
Proportionlity in the strict control of the inventive method temperature rise rate, pyrolysis temperature and the reaction system between each composition, obtained just that pattern is even, the close nanometer rod of size the time, improve ion exchange ratio, realized the preparation of high density magnetic element doping CdS nanometer rod.(Me
4N)
4[S
4Cd
10(SPh)
16] add-on of powder is lower than 1/40 of high boiling solvent quality, then can not form nanometer rod, and (Me
4N)
4[S
4Cd
10(SPh)
16] add-on of powder is higher than 1/20 of high boiling solvent quality, then nanometer rod a large amount of branches occur and causes size and the pattern inequality.Therefore, (Me
4N)
4[S
4Cd
10(SPh)
16] additional proportion of powder and high boiling solvent is huge to quality (pattern) influence of nanometer rod.The inventive method pyrolysis temperature must not be lower than 200 ℃, otherwise can't form nanometer rod, but forms nanoparticle, but pyrolysis temperature can not be too high, otherwise that nanometer rod will occur will be crosslinked; The inventive method is carried out in the hot conditions more than 200 ℃ simultaneously, realized the exchange of magnetic element ion and Cd ionic fast, shortened the preparation time of nanometer rod, not so the high temperature pyrolysis soaking time surpasses 1 hour, nanometer rod will have branch to form and pattern inhomogeneous.The strict control of the inventive method temperature rise rate (1.0 ℃/min) be to form that pattern is even, the key of the close nanometer rod of size, and can improve ion exchange ratio.
The prepared magnetic element doping CdS nanometer rod of the inventive method can be measured wherein magnetic element ionic doping content with inductively coupled plasma atomic emission spectrum (ICP-OES).
Embodiment
Technical solution of the present invention is not limited to following cited embodiment, also comprises the arbitrary combination between each embodiment.
Embodiment one: present embodiment magnetic element Co doping CdS nanometer rod prepares by following step:
One, with high boiling solvent vacuum outgas 2 hours under 120 ℃ of conditions, will be cooled to 60 ± 3 ℃ then, and carry out reflux under argon gas atmosphere, the reflux temperature rise rate is 1.0 ℃/min, and system is warming up to 60~100 ℃ and adds (Me
4N)
4[S
4Cd
10(SPh)
16] powder, the system of the treating muddy shape that is creamy white adds (Me again
4N)
2[Co
4(SC
6H
5)
10] powder, system is the turbid shape of color contamination darkly; Two, continue to keep the temperature rise rate of 1.0 ℃/min to be heated to 200 ℃~280 ℃ and be incubated 0.5~1 hour, naturally cool to 60 ℃ afterwards, and add anhydrous methanol and precipitate with centrifugal, the solid formation that obtains precipitates centrifugal 2 times with anhydrous methanol once more; Three, the solid formation that step 2 is obtained is dissolved in toluene, adds the anhydrous methanol centrifugation again, and vacuum-drying obtains the CdS:Co nanometer rod powder of high boiling solvent surface coverage then; Four, carry out the surface ligand exchange with pyridine, promptly obtain magnetic element Co doping CdS nanometer rod; (Me in the step 1 wherein
4N)
4[S
4Cd
10(SPh)
16] add-on of powder is 1/20~1/40 of high boiling solvent quality; (Me in the step 1
4N)
2[Co
4(SC
6H
5)
10] add-on of powder is (Me
4N)
4[S
4Cd
10(SPh)
16] powder quality 1/3~1/5.
High boiling solvent is hexadecylamine, trioctylphosphine oxide (TOPO) or oleic acid in the present embodiment step 1.
Adopt pyridine to carry out surface ligand exchange, the peelable Co ion that falls to be adsorbed on nanorod surfaces in the present embodiment.Inductively coupled plasma atomic emission spectrometer (ICP) is measured, and the emission peak of Cd is measured at 214.4nm; The emission peak of Co is measured at 228.6nm and 238.9nm place, measures concentration error 0.2~0.4%.
After the ICP test result showed that Co doping CdS nanometer rod is through the pyridine ligand exchange, Co ion volumetric molar concentration was respectively 0.079 (Cd
0.921Co
0.079S)---with the hexadecylamine is high boiling solvent, 0.110 (Cd
0.890Co
0.110S)---with the trioctylphosphine oxide (TOPO) is high boiling solvent and 0.185 (Cd
0.820Co
0.180S)---with oleic acid is high boiling solvent, and does not carry out that the Co ionic concn is respectively 0.082,0.117 and 0.196 in the pyridine peel sample.The reduction of Co ionic concn shows in prepared CdS:Co nanometer rod sample after the ligand exchange, 5%~7% Co ionic adsorption is arranged in the CdS nanorod surfaces.
Pyridine is peeled off and the ICP test result confirms, a large amount of Co ion dopings has entered CdS nanometer rod inside, and along with the increase of Co molecular clustering add-on, the Co doping content increases.
The TEM figure of different Co doping content CdS nanometer rod is as Fig. 1~shown in Figure 3; The x-ray diffraction pattern of different Co doping content CdS nanometer rod as shown in Figure 4.
The magnetic element Co doping CdS nanometer rod of present embodiment preparation can be dispersed in the organic solvent (as toluene, normal hexane, chloroform etc.), and is even as Fig. 1~nanometer rod pattern shown in Figure 3, narrow size distribution.
The diffraction peak that can observe three kinds of nanometer rod from Fig. 4 has tangible broadening phenomenon, shows that sample size is within nanometer range.From XRD figure, can also observe characteristic peak (002), (110), (103) and (112) diffraction peak of wurtzite structure, contrast discovery with standard JCPDS card, the position of all diffraction peaks and intensity and wurtzite structure (JCPDS No.41-1049) match, illustrating that thus the Co doping does not change the nanocrystalline crystalline texture of CdS, still is wurtzite structure.Owing to do not observe the existence of other impurity phase diffraction peak, the degree of purity of production height be described.
The Co ion has been accelerated the formation of nanometer rod in the doping of CdS intracell in the present embodiment, has shortened the reaction times.
Embodiment two: the difference of present embodiment and embodiment one is: carry out high-speed stirring with magnetic stir bar in the reflux process, the magnetic agitation rotating speed is 140~180r/min.Other step and parameter are identical with embodiment one.
Embodiment three: present embodiment and embodiment one or twos' difference is: the volume that adds anhydrous methanol in the step 3 is 1~2 times of volume of toluene.Other step and parameter are identical with embodiment one or two.
Embodiment four: the difference of one of present embodiment and embodiment one to three is: add anhydrous methanol centrifugation repetitive operation 3 times in the step 3, centrifugation time is 10min/ time, and centrifugal rotational speed is 8000~15000r/min.Other step and parameter are identical with one of embodiment one to three.
Embodiment five: the difference of one of present embodiment and embodiment one to four is: vacuum drying temperature is 10~20 ℃ in the step 3, and be 24h time of drying, and vacuum tightness is 0.1MPa.Other step and parameter are identical with one of embodiment one to four.
Embodiment six: the difference of one of present embodiment and embodiment one to five is: be heated to 245 ℃~280 ℃ and be incubated 0.5~0.7 hour.Other step and parameter are identical with one of embodiment one to five.
Embodiment seven: present embodiment magnetic element Mn doping CdS nanometer rod prepares by following step:
One, with high boiling solvent vacuum outgas 2 hours under 120 ℃ of conditions, will be cooled to 60 ± 3 ℃ then, and carry out reflux under argon gas atmosphere, the reflux temperature rise rate is 1.0 ℃/min, and system is warming up to 60~100 ℃ and adds (Me
4N)
4[S
4Cd
10(SPh)
16] powder, the system of the treating muddy shape that is creamy white adds MnCl again
2Powder, system be the turbid shape of color contamination darkly; Two, continue to keep the temperature rise rate of 1.0 ℃/min to be heated to 200 ℃~250 ℃ and be incubated 0.5~1 hour, naturally cool to 60 ℃ afterwards, and add anhydrous methanol and precipitate with centrifugal, the solid formation that obtains precipitates centrifugal 2 times with anhydrous methanol once more; Three, the solid formation that step 2 is obtained is dissolved in toluene, adds the anhydrous methanol centrifugation again, and vacuum-drying obtains the CdS:Co nanometer rod powder of high boiling solvent surface coverage then; Four, carry out the surface ligand exchange with pyridine, promptly obtain magnetic element Co doping CdS nanometer rod; (Me in the step 1 wherein
4N)
4[S
4Cd
10(SPh)
16] add-on of powder is 1/20~1/40 of high boiling solvent quality; MnCl in the step 1
2The add-on of powder is (Me
4N)
4[S
4Cd
10(SPh)
16] powder quality 1/2~1/5.
MnCl in the present embodiment
2The add-on of powder influences the quality (pattern) of nanometer rod, MnCl
2The add-on of powder is higher than (Me
4N)
4[S
4Cd
10(SPh)
16] powder quality 1/2, then can not form nanometer rod or nanocrystalline.And, pyrolysis temperature be higher than 250 ℃ then nanometer rod will occur crosslinkedly, be lower than 200 ℃, otherwise can't form nanometer rod, but form nanoparticle.
High boiling solvent is hexadecylamine, trioctylphosphine oxide (TOPO) or oleic acid in the present embodiment step 1.
Adopt pyridine to carry out surface ligand exchange, the peelable Mn ion that falls to be adsorbed on nanorod surfaces in the present embodiment.
After the ICP test result showed that Mn doping CdS nanometer rod is through the pyridine ligand exchange, Mn ion volumetric molar concentration was respectively 0.065 (Cd
0.935Mn
0.065S)---with the hexadecylamine is high boiling solvent and 0.12 (Cd
0.880Mn
0.120S)---with oleic acid is high boiling solvent.
Pyridine is peeled off and the ICP test result confirms, a large amount of Mn ion dopings has entered CdS nanometer rod inside, and along with the increase of Mn molecular clustering add-on, the Mn doping content increases.
The TEM figure of different Mn doping content CdS nanometer rod is as Fig. 5~shown in Figure 7.
The magnetic element Mn doping CdS nanometer rod of present embodiment preparation can be dispersed in the organic solvent (as toluene, normal hexane, chloroform etc.); Can observe the Mn doping content when low by Fig. 5, product is the mixture of nanoparticle and chain-cluster body and shorter nanometer rod; Increase Mn ionic doping content, the crystallinity of gained nanometer rod is greatly improved, as shown in Figure 6 and Figure 7.Illustrate that the doping of Mn ionic also helps the formation of homogeneous CdS nanometer rod.
The Mn ion has been accelerated the formation of nanometer rod in the doping of CdS intracell in the present embodiment, has shortened the reaction times; And Mn ion doping concentration is big more, helps the formation of homogeneous CdS nanometer rod more.
Embodiment eight: the difference of present embodiment and embodiment seven is: carry out high-speed stirring with magnetic stir bar in the reflux process, the magnetic agitation rotating speed is 140~180r/min.Other step and parameter are identical with embodiment seven.
Embodiment nine: present embodiment and embodiment seven or eights' difference is: the volume that adds anhydrous methanol in the step 3 is 1~2 times of volume of toluene.Other step and parameter are identical with embodiment seven or eight.
Embodiment ten: the difference of one of present embodiment and embodiment seven to nine is: add anhydrous methanol centrifugation repetitive operation 3 times in the step 3, centrifugation time is 10min/ time, and centrifugal rotational speed is 8000~15000r/min.Other step and parameter are identical with one of embodiment seven to nine.
Embodiment 11: the difference of one of present embodiment and embodiment seven to ten is: vacuum drying temperature is 10~20 ℃ in the step 3, and be 24h time of drying, and vacuum tightness is 0.1MPa.Other step and parameter are identical with one of embodiment seven to ten.
Embodiment 12: the difference of one of present embodiment and embodiment one to 11 is: be heated to 245 ℃~250 ℃ and be incubated 0.5~0.6 hour.Other step and parameter are identical with one of embodiment one to 11.