问题：李亚栋教授文章缩要
类型：交流
提问：layytent
等级：▲
版块：纳米科技(yunshiyu,zjb771019,)
信誉：0%
回复：0
阅读：1829
时间：2006-07-17 17:40:00 编辑加入/取消收藏订制/取消短消息举报该贴

李亚栋　
李亚栋
论文题目：半导体纳米材料的溶剂热合成、结构与性能研究
作者简介：李亚栋，男，1964年11月生，1995年09月师从中国科学技术大学钱逸泰教授，于1998年06月获得博士学位。
摘要

本文旨在探索半导体纳米材料的化学合成新方法。通过大量文献调研，发现在半导体纳米材料的化学合成研究领域中存在的问题与机遇。提出并建立了溶剂热元素直接反应、有机溶剂室温转化、溶剂热还原、自还原、中温热解催化合成、水热化学反应自控制等六种纳米材料合成新方法，成功地合成出了二十余种半导体纳米材料。

发展了溶剂热元素直接反应合成II-VI族半导体纳米晶合成路线

M(M=Zn, Cd)+E(E=S, Se, Te) ¾® ME

在吡啶溶液中，将等摩尔比的硫粉（或硒粉）与锌粉在180°C进行溶剂热反应一定时间后一步可以得到平均粒径为10nm的ZnS和15nm的ZnSe纳米晶。实验表明：反应溶剂的配位能力决定目标产物能否形成。反应的温度和反应时间对产物的粒径影响较大。类似地，用金属镉和硫属元素（S,
Se, Te）在吡啶和胺类溶剂中直接反应,
可以得到CdE。以CdS为例，在吡啶中形成六方相球形CdS纳米晶,平均粒径约为50nm；在1-6已二胺中得到的是棒状立方纤锌矿的CdS；在二乙胺中，得到的是立方和六方的混合相，产物形貌为球形粒子。尺寸在20nm左右。在乙二胺中得到的是立方相的CdS纳米棒。用Raman光谱和XPS对所得的CdS纳米棒进行表征，结果表明样品纯度高，质量好，CdS纳米棒的吸收光谱与发射光谱表明：由于形貌和尺寸的变化，与传统体相材料相比，吸收光谱变宽且发生了蓝移。对CdSe和CdTe,也进行了的系统的研究
[参见Inorg. Chem. 38（1999），1382]。除了对反应的温度、溶剂以及可能的反应机理进行探讨,
我们还提出了纳米棒的可能形成机理，乙二胺、已二胺作为双齿配体可以和金属离子配位，有利于CdS在某一结晶面上的聚集和生长，抑制了在其它方向上的生长，形成纳米棒。[参见Chem.Mater.
10(9),2301,1998 ]

在制备汞的硫属化合物半导体时，考虑到汞单质较强的毒性和避免使用剧毒性硫属元素氢化物如H2S。我们在乙二胺中将氧化汞和硫属元素直接混合：

HgO+E¾®HgE, E=S, Se, Te

在室温下，电磁搅拌反应7~10小时，可以分别得到六方纤锌矿的HgS和立方闪锌矿的HgSe以及HgTe。分析表明，反应完全，没有HgO以及其它杂质。TEM显示所有产物均为50nm球形粒子。成功地建立了有机溶剂室温直接转化法合成半导体纳米晶。[参见J.Phys.
&Chem. Solids, 60(7),965,1999]

III-V族化合物半导体纳米材料的研究是目前物理，化学，材料以及电子等学科研究的热点。从化学的角度来说，对该类化合物研究主要是集中在（1）传统的高温固相反应；（2）利用金属有机化合物；（3）金属氯化物和磷属元素的钾盐或钠盐的转换反应。由于这些反应所涉及的过程往往比较复杂，实验条件要求较高，试剂昂贵且比较危险。为此发展简便、价廉的合成途径意义重大。本论文提出了溶剂热共还原合成III-V族半导体纳米材料新的化学合成路线：

InCl3+AsCl3+3Zn¾®InAs+3ZnCl2

以InCl3和AsCl3为反应物，有机溶剂为反应介质，在还原剂的存在下，合成出了晶粒尺寸为10nm左右的立方闪锌矿InAs纳米晶。反应的可能机理是金属锌和反应体系中的微量水反应形成活性氢，活性氢再还原AsCl3和InCl3产生具有较高反应活性的As和In纳米团簇，在反应的温度下，直接化合形成InAs。实验中详细考虑了各种实验条件对产物的形成，颗粒尺寸以及纯度等的影响，发现反应体系中的水的量应合适，太高容易形成氢氧化物杂质,污染InAs：还原剂的还原性应适中，太强或太弱对InAs的形成均不利；温度过高（如300°C），反应速度加快，同样不利于形成小粒径的InAs纳米晶；在乙二醇体系中，通过乙二醇与反应物之间的配位效应，有效地控制了反应速度；得到了结晶较好的球形产物，而在乙二胺中则有部分一维纳米棒形成。进一步验证了乙二胺的双齿配体对形成一维纳米棒的模板作用[参见J.Am.Chem.Soc.119(33),7869,1997]。

在上述方法的基础上，发展了溶剂热自还原法制备其它一些III-VI族半导体纳米材料，如InAs(晶须)、InSb、InP、GaSb等。由于在制备过程中避免使用了其它还原剂，为提高产品的质量提供了保障。具体方法为，以PCl3、AsCl3、SbCl3为原料，金属铟和镓为还原剂，利用溶剂热方法制备出一些III-V族纳米半导体材料。其中InSb的液相合成在国际上尚未见报道。关于InAs纳米晶须的形成，可以用Vapour-Liquid-Solid(VLS)生长机制进行解释。

以低熔点的金属（如钠）为熔剂，在一定量的催化剂存在下，进行了CCl4的中温催化还原热解法制备金刚石粉。在有机合成中利用传统的Wurtz反应可以使烷烃链长增加。由此启示利用sp3杂化的C源，直接制得金刚石。从XRD可以清楚地看到（111），（100）和（311）晶面的衍射峰，并用Raman光谱对制得的金刚石粉进行了表征[参见Science,281,783,1998]。

利用水热反应制备出一系列金属氧化物半导体纳米材料
1).
ZnGa2O4是一种低压荧光半导体材料，可用于场发射显示装置的真空平板阴极射线管，以Zn和GaCl3的稀盐酸溶液进行水热合成制备出尖晶石结构的ZnGa2O4,TEM显示其粒径为10nm左右,适宜的合成温度为140-170℃,产率大于95%。由于反应过程中金属锌可以和稀盐酸反应,控制了Zn2+的形成和水溶液体系中pH值，对ZnGa2O4的形成起到了决定性的作用；[参见Chem.
Mater. 1091],17,1998]
2）以(NH4)2SO4·FeSO4·6H2O和水合肼为反应物在不同的pH值条件下利用水合肼的氧化—还原特性可以获得α-Fe2O3和Fe3O4；[参见Mater.
Res.Bull., 33(6),841,1998]
3)在聚乙二醇的保护下，将SnCl4·5H2O在氨性介质中150℃进行水热反应，可以得到无团聚、分散好、粒径分布均匀的3nm的SnO2,分别用红外光谱和拉曼光谱对所得的样品进行了表征；
4）以KMnO4为原料，H2O2还原法首先在180℃水热条件下处理得到前驱物，经1：1HNO3多次洗涤干燥后，在400℃下脱水可以制得γ-MnO2，实验表明，水热处理后的胶体的静置时间对产物的形貌影响较大，此外不同的晶化温度可以得到不同的产物，400℃是γ-MnO2，700℃下是Mn2O3；
5)在混合溶剂中也可以利用水热法制备出纳米级的NiO和Co3O4。

Abstract
The object of this dissertation is to explore new synthetic methods to nanoscale
semiconductors. It is found that, based on the study of so much currently
available literatures, there are some challenges existed in the present
research of nanoscale semiconductors, especially for the synthetic strategy.
Here, solvohermal elemental direct combination, room temperature organic solvent
conversion, solvothermal reduction and self-reduction, mild temperature
pyrolysis-reduction-catalysis as well as hydrothermal self-regulation process
have been proposed and established for the synthesis of nanoscale materials.
More than twenty kinds of nanoscale semiconductors have been successfully
synthesized by the above mentioned methods or the combination of some of them.
Developing solvohermal elemental direct combination route to II-VI semiconductor
nanocrystals
M(M=Zn, Cd)+E(E=S, Se, Te) ¾® ME
Stoichiometric sulfur (or selenium) and zinc were added to pyrridine holden in
stainlessness’ autoclave with Teflon liner. After reaction at 180°C for a
certain duration time, nanocrystalline ZnS and ZnSe with average particle sizes
of 10nm and 15nm could be obtained through one-pot synthetic process. The
formation of these products depend on the complex ability of the solvents and
the particle sizes are determined in a large scale of the reaction temperature
and duration time. Similarly, cadmium chalcogenides can be also prepared through
the reaction of cadmium and chalcogen in pyridine and some other amine solvents.
Take CdS for account, hexagonal spherical CdS with average particle size of 50nm
was formed in pyridine, cubic rod-like in 1,6 hexyl diamine, mixtures of cubic
and hexagonal spherical particles with 20nm in biethylamine and and cubic
nanorods in ethylenediamine。The nanorods of CdS obtained in ethylenediamine were
also characfterized be Raman and XPS spectroscopy, these results indicate that
the product were in high purity and quality. Compared with conventional bulk
materials, the absorbance of CdS was broadened and shifted to blue range due to
the change of morphology and size. The synthesis and characterization of CdSe
and CdTe have been also systematically investigated. More information about this
can be seen in detail in [Inorg. Chem. 38（1999），1382]。Besides all of these, the
possible mechanism for the formation of nanorods in some system was also
proposed. It is believed that the formation of nanorods in 1,6 hexylene diamine
and ethylenediamine was originated from the bidentric properties of these two
solvents. A detailed dexcription concerning this can be found in [Chem.Mater.
10(9),2301,1998 ].
In preparing mercury chalcogenides, in order to avoid the use of toxic mercury
and gas such as H2S, HgO and chalcogen were mixed together and
electromagnetically agitated at room temperature for 7-10 hours
HgO+E¾®HgE, E=S, Se, Te
Hexagonal HgS and cubic HgSe as well as HgTe could be conveniently obtained.。No
impurities such as HgO and chalcogen could be found in the XRD pattern。TEM
showed that all products were spherical with diameters about 50nm。So an organic
solvent room temperature direct conversion process has been established for the
synthesis of semiconductors. More information can be seen in [J.Phys. &Chem.
Solids, 60(7),965,1999].
The research of III-V nanoscale materials has appealed a lot of research
interest of physical, chemical,material, and electronic scientist. From the view
of chemistry, the research is mainly concentrated on pursuing novel and
convenient synthetic process to these materials since the conventional methods
such as (1) high-temperature solid state reaction, (2) utilizing organometallic
precursors, (3) the metethesis reactions between metal halides and sodium or
potassium pnictides, are usually complicated and require extreme experiment
conditions. Besides this, the reagent used are usually expensive and dangerous.
So it is significant to develop simple and low-cost preparation routine for
these compounds. A new solvothermal co-reduction chemical process to III-V group
semiconductors was raised here:
InCl3+AsCl3+3Zn ¾® InAs+3ZnCl2
With the use of organic solvent as reaction medium, cubic InAs with about 10nm
particles size could be synthesized from InCl3, AsCl3 and reductive such as
zinc. The process might involve the combination of newly reduced clusters of As
and In, which were produced from the redox reactions between AsCl3,InCl3 and
reactive atomic hydrogen released from the reaction between zinc powder and the
co-existed water in the reaction system. Many factors were considered in this
synthesis, for example, the amount of water in the reaction system should not be
too much otherwise there would be impurities like In(OH)3 accompanying the final
products. The reducing ability of reductive could not be too strong or weak for
it is disadvantage for the formation of InAs at this condition and particles
with larger size would be produced if the temperature is as high as 300°C due to
accelerated reaction rates. For the ethylene glycol reaction system, the
reaction rates can be controlled through the coordination between the reactant
and ethylene glycol and spherical particles with good crystallinity was
obtained. For the ethylenediamine system, InAs nanorods were obtained, which
further supports the bidentric template mechanism of ethylenediamine on the
formation of nanorods. [J.Am.Chem.Soc.119(33),7869,1997]。
Based on the above established methods, a self-reduction method to other III-V
semiconductors nanomaterials was developed, such as InAs (whiskers), InSb, InP,
GaSb. Since the use of external reductive was circumvented in the preparation
process, it is helpful to improve the quality of the product. In a typical
process, some III-V semiconductors are prepared by the solvothermal methods,
using PCl3、AsCl3、SbCl3 as source materals and metallic Indium and Gallium as
reductives. To the best of our knowledge, it is the first time to prepare InSb
in the liquid medium. In the case of the formation of nano whiskers of InAs, the
Vapour-Liquid-Solid (VLS) growth mechanism was discussed.
Using metal (such as Sodium) with low melting point, the diamond powder was
prepared by Pyrolysis- Reduction -Catalysis of CCl4 at a moderate reaction
temperature. The chain increment of alkylane is usually realized by using the
Wurtz reaction in organic synthesis. This give a hint that diamond might be
prepared directly from sp3 hybridized carbon source. XRD pattern clearly shows
three typical reflection peaks of (1111), (100) and (311) lattice plane. In
addition, the diamond powder was characterized by Raman spectroscopy
[Science,281,783,1998]。
A number of metal oxides nano materials have been synthesized through
hydrothermal processes:
1) As a low voltage luminescence semiconductor, ZnGa2O4 can be employed as
vacuum flat cathode ray tubes (CRT) using field emitting display.
Nanocrystalline spinel ZnGa2O4 with diameter of 10nm was prepared in diluted
hydrochloric solution of GaCl3 with the presence of zinc powder. The favorable
reaction temperature range is 140-170℃ and the yield is larger than 95%.The
formation of ZnGa2O4 depends largely on the concentration of Zn2+ and pH value
of solution. Since the concentration of Zn2+ and pH value can be regulated
through the reaction of zinc and HCl, this process can be viewed as a
self-regulated process [Chem. Mater. 1091],17,1998]
2) Nanocrystalline α-Fe2O3 and Fe3O4 were made from (NH4)2SO4·FeSO4·6H2O and
hydrazine by hydrothermal process under various pH, for the redox properties of
hydrazine change with the pH value of the reaction solutions.[Mater. Res.Bull.,
33(6),841,1998]
3) With the protection of polyglycol, less agglomerated and uniform 3nm SnO2 was
hydrothermally prepared from SnCl4·5H2O in amine solution at 150℃.The product
was characterized by FTIR and Raman spectroscopy.
4) Under hydrothermal condition, a precursor of γ-MnO2 was reduced from KMnO4 by
H2O2 at 180℃. After being washed by 1：1 HNO3 for several times and desiccated,
the precursor was dehydrated at 400℃ to form γ-MnO2. The morphology of final
product is influenced by the aging time of the hydrothermally treated precursor.
In addition, different products can be obtained at different crystalline
temperature, for example: γ-MnO2 at 400℃ and Mn2O3 at 700℃.
5) Nanoscale NiO and Co3O4 can also be hydrothermally synthesized in mixed
solvents.

　回主页

问题讨论没有结束...

您尚未进入本论坛,登录之后才可以回贴

8msec