摘要
目前无机纳米材料的研究主要集中于低维无机纳米材料的制备,如纳米颗粒、纳米纤维等,其制备方法已相当成熟,而对高维特殊形貌无机纳米材料的研究相对较少。近年来,具有特殊形貌的高维无机纳米材料因独特的结构和表面性质在催化、太阳能电池、传感器、微波吸收、医学等领域展现出优于低维纳米材料的性能,但制备出的材料种类少,形貌不均一,可控性较差。因此,研究者们致力于特殊形貌无机纳米材料生长机理的研究,为材料制备提供有效的理论依据。制备无机纳米材料的方法有微乳液法、溶胶-凝胶法、电化学法、水/溶剂热法等。其中水/溶剂热法制备的无机纳米材料具有晶粒发育完整、粒度分布均匀、颗粒之间少团聚、原料价格较便宜的优点,因此被广泛应用于特殊形貌无机纳米材料的制备。自组装技术作为超分子领域的新概念,在制备特殊形貌的材料中发挥着重要作用,其主要作用是将低维的纳米结构单元通过氢键、范德华力、静电力等非共价键作用力进行连接而组装成各种复杂的层级结构。现已通过自组装技术合成了片状、棒状、花状、海绵状、树枝状等特殊形貌无机纳米材料。其中片状材料的生长过程如下:第一步是纳米颗粒的奥斯特瓦尔德熟化过程,第二步是熟化的纳米颗粒定向附着自组装成片状材料。棒状材料的生长过程出现了两种情况,第一种与片状形成过程相同,第二种则是先形成片状,然后片状发生卷曲形成棒状材料,棒状材料再定向附着自组装成长径比不同的棒状材料。花状、海绵状、树枝状等复杂形貌的形成则是基于片状或棒状材料,通过氢键自组装而成。自组装过程会受到表面活性剂或模板剂、溶剂、沉淀剂、酸碱度等因素的影响。研究者们发现利用水热法制备纳米材料时,引入合适的表面活性剂或模板剂,能够促使低维纳米结构单元进行有序自组装而形成结晶度好、尺寸均匀的特殊形貌纳米材料。通过改变表面活性剂或模板剂、溶剂、沉淀剂的种类和剂量及酸碱度等因素,影响纳米颗粒的生长方向、生长速率及颗粒之间的作用力,进而控制产品的形貌和尺寸。本文对近年来国内外利用自组装技术制备特殊形貌无机纳米材料的研究成果进行了介绍,分析讨论了自组装过程的影响因素,并对自组装制备特殊形貌无机纳米材料的发展方向和应用前景进行了展望,以期为制备性能优越的特殊形貌纳米材料提供参考。
In recent years,the research of inorganic nanomaterials mainly focuse on the preparation of low-dimensional inorganic nanomaterials,such as nanoparticles and nanofibers,which possess a quite mature preparation method,while the study on high-dimensional inorganic nanomaterials with special morphology is relatively scarce.Recent researches demonstrated that high-dimensional inorganic nanomaterials with special morpho-logy exhibit superior performance than that of the low-dimensional nanomaterials in certain fields,including catalysis,solar cells,sensors,microwave absorption and medicine,due to their unique structure and surface properties,while the types of prepared high-dimensional inorganic nanomaterials are few,their morphologies are non-uniform,and their controllability is poor.Therefore,some researchers committed to the study on the growth mechanism of inorganic nanomaterials with special morphology,and expected to provide an effective theoretical basis for material preparation.Methods for preparing inorganic nanomaterials include microemulsion method,sol-gel method,electrochemical method,hydrothermal/solvothermal method,etc.Among them,the inorganic nanomaterials prepared via hydrothermal/solvothermal method have a series of advantages including complete crystalline phase,uniform particle size distribution,less agglomeration between particles and cheaper raw materials,thus they are widely adopted.As a new concept in the the field of supermolecular,the self-assembly technique plays a crucial role in preparations of these materials with special morphology.And its main function is to connect and assemble low-dimensional nanostructure units into various complex hierarchical structures by non-covalent bonds such as hydrogen bond,van der Waals force and electrostatic force.The inorganic nanomaterials with special morphology,including flakes,rods,flowers,sponges and dendrites have been synthesized by self-assembly technology.The growth process of flake-like materials are as follows:the first step is the Osterval ripening process of the nanoparticles,and the second step is directional adhesion and self-assembled of the ripened nanoparticles into the flake-like materials.There are two cases in the growth process of the rod-like materials.One is the same as the flakes forming process,the other one is firstly formed into flakes,and then curl into the rod-like units,finally,the rod-like units are directional adhesion and self-assembled to rod-like materials with different ratios of length to diameter.The formation processes of complex morphologies such as flowers,sponges,dendrites and others are self-assembled via hydrogen bonds on the basis of the formation of the flake-like or rod-like units.The self-assembly process is affected by surfactants or templating agents,solvents,precipitants and pH,etc.The researchers found that the introduction of appropriate surfactants or templating agents when utilizing the hydrothermal method can promote the order self-assembly of low-dimensional nanostructure units to form special morphological nanomaterials with well-crystallized,uniform size.The morphology and size of the product can be controlled by growth direction,growth rate and interaction force between nanparticles which are affected by changing the preparing conditions such as surfactant or template,precipitant type and dosage and pH,etc.In this paper,the research findings on the synthesis of inorganic nanomaterials with special morphology via self-assembly technology in recent years are reviewed,and the influencing factors of self-assembly process are comprehensively discussed.In addition,the development direction and application of inorganic nanomaterials with special morphology are prospected as well,looking forword to provide a reference for the preparation of special morphology nanomaterials with superior properties.
作者
陈娟
江琦
CHEN Juan;JIANG Qi(School of Chemistry and Chemical Engineering,South China University of Technology,Guangzhou 510640)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2019年第3期454-461,共8页
Materials Reports
基金
广东省教育部产学研结合项目(20090916)~~
关键词
自组装
特殊形貌
纳米材料
水热法
self-assembly
special morphology
nano-material
hydrothermal method
