碳纳米线圈的调控制备及其在SERS中的应用

发布时间：2018-03-12 19:04

本文选题：碳纳米线圈　切入点：可控制备　出处：《大连理工大学》2017年博士论文　论文类型：学位论文

【摘要】：近些年,随着纳米技术的日益成熟,人们成功制备出了多种具有不同形貌、结构的低维碳纳米材料及其复合材料。这些碳纳米材料展示出了优异的物理和化学性质,被广泛地应用于能源、传感、电子器件等领域,极大地促进了科技的发展。碳纳米线圈(CNC)做为一种具有三维螺旋结构的碳纳米材料,展示出很多与碳纳米管、石墨烯等低维碳材料所不同的物理和化学性质。大量研究表明CNC的特性是与其线圈直径、螺距以及结构息息相关的,但目前对CNC的调控尚不理想,如何进一步实现对CNC的直径、螺距以及结构的调控仍然是CNC制备技术上的一大挑战。本论文通过研究CNC的直径随反应时间的变化特征以及对CNC生长经验公式的拟合,得出了催化剂颗粒大小与其活性和寿命的关系。并通过调控催化剂膜厚以及利用单层氧化硅小球作为基板来调控催化剂颗粒的空间尺寸与分布,从而实现了对CNC的直径、螺距以及结构的调控,同时还对其成长机理进行了分析研究。此外,通过将磁控溅射与光催化相结合的方法对所合成的Ag纳米颗粒的分布与尺寸进行优化调控,并在分散有CNC的TiO_2薄膜表面成长出Ag纳米颗粒与纳米片的混合体,探索了其在表面增强拉曼散射光谱(SERS)领域中的应用。本论文主要研究工作如下:(1)CNC的线圈直径、螺距以及结构的调控:首先,研究了反应时间与CNC的直径分布的依赖关系,发现随着反应时间的增加,具有较大直径的CNC的比例在逐渐增加。并对碳产物的产量与反应时间的关系进行了研究,得到了其生长经验公式。研究发现该经验公式具有三组不同的催化剂特征参量。这是由于在CNC的成长过程中其催化剂颗粒的大小以及活性的不均一性造成的。尺寸较小的催化剂颗粒具有比较高的活性,但是其催化寿命却比较短,其在CNC成长初期发挥主导作用。而尺寸较大的催化剂颗粒具有的催化活性比较低,但是其催化寿命比较长,随着反应时间的推移,其逐渐占据主导地位。其次,在保持Sn、Fe摩尔比不变的条件下,通过控制Sn/Fe催化剂的膜厚来调控催化剂颗粒的大小以及聚集程度,实现了对CNC的线圈直径、螺距以及结构的调控。研究发现随着催化剂膜厚的降低,CNC的形态结构逐渐从弹簧状向辫状变化,CNC的直径逐渐减小,并且其石墨化程度越来越高。当催化剂膜厚为3nm以下时,所合成的碳产物由CNC转变为碳纳米纤维以及扭曲状碳纳米线,由此可知保证高效制备CNC的最小催化剂膜厚为3到7nm之间。最后,利用单层氧化硅小球来限制催化剂颗粒的空间分布及尺寸,并为CNC的成长提供了必要的根部固定作用,从而成功实现了对CNC的线圈直径的调控。研究发现CNC的平均直径随着氧化硅小球直径的降低而减小。同时,采用氧化硅小球有利于减小副产物层的比例,提高了 CNC的产率。此外,采用氧化硅小球为模板来模样化Sn/Fe催化剂薄膜的方法,实现了 CNC直径的进一步降低。(2)小直径碳纳米线圈制备的探索:首先,研究了不同的Sn、Fe溅射次序对催化剂颗粒尺寸、空间分布以及碳产物形态的影响。研究发现按照Fe、Sn的先后次序溅射而形成的催化剂薄膜,经过煅烧后无法形成有效的催化剂颗粒和聚集,从而无法生长出CNC;按照Sn、Fe先后次序溅射而形成的催化剂薄膜,煅烧后形成了颗粒状的分布,并在化学气相沉积的过程中生长出了CNC。其次,研究了不同Sn、Fe比例对CNC直径的影响,发现CNC的直径随着Sn膜厚度的降低而减小。在此基础上,我们采用单一的Fe薄膜作为催化剂,利用单层氧化硅小球对催化剂颗粒的形态和分布的限制以及为CNC的成长提供必要的根部固定作用,对小直径CNC的制备展开了初步的探索。实验结果表明利用此种方法成功地合成出了直径在50nm以下的小直径CNC,并且其产率会随着氧化硅小球直径的减少而增加。(3)CNC对光催化制备Ag纳米颗粒及其SERS活性的影响:通过在TiO_2薄膜上预溅射高密度的Ag纳米种子的方法来调控光催化过程中电子的传输和分布,从而提高Ag纳米颗粒的成核密度,随后利用光催化还原硝酸银的方法在Ag纳米种子上制备出了高密度的Ag纳米颗粒并控制其颗粒尺寸,以上方法有效地增加了 SERS活性位点,极大地提高了对R6G分子的探测灵敏度。此外,我们利用时域有限差分法对激光照射情况下粒子表面的电场强度进行理论模拟,研究了 Ag纳米颗粒的尺寸及间距对其SERS效果的影响。在以上工作的基础上,通过光催化的方法在分散有CNC的TiO_2薄膜上成功制备出了 Ag纳米颗粒与纳米片的混合体,并将其应用于SERS中。CNC的螺旋形貌、导电性以及光热转化特性影响了光催化过程中的电子分布与转移以及局部热量分布,我们推测这些可能是所合成的Ag纳米颗粒的形态和分布产生了很大变化的主要原因。利用此法制备出的Ag纳米颗粒展示了出非常出色的SERS活性,并且具有良好的SERS均一性。
[Abstract]:In recent years, with the increasing maturity of nanotechnology, people were successfully prepared with different morphologies, low dimensional carbon nano materials and composite materials. The structure of the carbon nano materials exhibit excellent physical and chemical properties, is widely used in the field of energy, sensor, electronic devices, greatly promote the science and technology the development of carbon nano coil (CNC) is a kind of carbon nano materials with 3D spiral structure, showing many of the physical and chemical properties of carbon nanotubes, graphene and other low dimensional carbon materials are different. A large number of studies show that the characteristics of CNC is its coil diameter, pitch and structure are closely related, but the current regulation the CNC is not ideal, how to achieve the CNC diameter, pitch and structure regulation is still a big challenge for the preparation of CNC technology. Through the research of CNC diameter with reaction time variable The characteristics and fitting growth experience formula of CNC, obtained the relationship between catalyst particle size and activity and life. And through the regulation of film thickness of catalysts and the use of single-layer silica spheres as substrate to space size and distribution regulation of catalyst particles, so as to realize the CNC diameter, pitch and structure regulation, but also to the growth mechanism was studied. In addition, optimize control by the distribution of Ag nanoparticles synthesized by magnetron sputtering method and the size and photocatalytic combination, and dispersed in TiO_2 thin film surface CNC grew out of a mixture of Ag nano particles and nano films, to explore its Raman scattering spectra in surface enhanced (SERS) application. The main research work of this thesis are as follows: (1) CNC coil diameter, pitch and structure regulation: first, study the reaction time and the diameter of CNC The dependence of distribution, with the increase of reaction time, with larger diameter ratio of CNC increased gradually. And the relationship between yield and reaction time on carbon products were studied, the growth of the empirical formula. The study found that the empirical formula with three different sets of catalyst characteristic parameters. This is due to not the size uniformity of catalyst particles and activity in the growth process of CNC. The smaller size of the catalyst particles with relatively high activity, but the catalytic life is relatively short, the CNC in the early growth play a leading role. The catalytic activity of the catalyst particle size is relatively low, but its catalytic life long as the reaction time, which gradually occupy the leading position. Secondly, in Sn, the molar ratio of Fe under the same conditions, by controlling the film thickness of Sn/Fe catalyst catalytic control The size and the degree of aggregation of particles, the coil diameter of CNC, pitch and structure regulation. It is found that the catalyst film thickness decreases, the morphology of CNC changed gradually from spring to braid, the diameter of the CNC decreases gradually, and the graphitization degree increasing. When the film thickness of catalysts below 3nm, the carbon compounds from CNC into carbon nanofibers and twisted carbon nanowires, thus ensure the minimum efficient preparation of CNC catalyst film thickness is between 3 to 7Nm. Finally, the spatial distribution and size of the single-layer silica spheres to limit the catalyst particles, and provides a fixed root the role necessary for the growth of CNC, so as to achieve the CNC coil diameter regulation. The study found that the average diameter of CNC decreases with the diameter of silica spheres. At the same time, the use of silicon oxide is beneficial to reduce the ball The proportion of byproducts, increased the yield of CNC. In addition, methods using silica spheres as template to Sn/Fe like catalyst film, can further reduce the diameter of CNC. (2) to explore the small diameter of carbon nano coil preparation: first of all, the effects of different Sn, Fe sputtering sequence of catalyst particles the size, distribution and influence the morphology of carbon products. The study found that according to Fe, the sequence of Sn catalyst films formed by sputtering, after calcination to form catalyst particles effectively and thus unable to grow together, CNC; according to Sn, Fe catalyst film sequence of sputtering formed after calcination, formation of granular the distribution of sedimentary facies in chemical process and gas in the growth of a CNC. second, the effect of different Sn. The effect of Fe ratio on CNC diameter, CNC diameter decreases with the thickness of Sn. On this basis, I The single Fe thin film as a catalyst, to provide the necessary role of fixed root morphology and distribution of the catalyst particles using single-layer silica spheres and the limitation of the growth of CNC, the small diameter of the preparation of CNC carry out preliminary exploration. The experimental results show that the method has been successfully synthesized in small diameter diameter CNC below 50nm, and its yield will increase with the decrease of silicon oxide ball diameter. (3) effects of CNC synthesis of Ag nanoparticles and its photocatalytic activity of SERS system: the method of pre sputtering on TiO_2 thin films of high density Ag nano seeds to control the transmission and distribution of electronic light catalytic process. In order to improve the nucleation density of Ag nanoparticles, followed by method of photocatalytic reduction of silver nitrate in Ag nano seeds were prepared on Ag nanoparticles with high density and control of the particle size, the above method effectively. Increase of SERS active site, greatly improve the detection sensitivity of R6G molecules. In addition, we use the FDTD method to simulate the electric field intensity on the surface of particles under laser irradiation, the size and spacing of Ag nanoparticles on the SERS effect. On the basis of the above work, through the method of photocatalytic TiO_2 films dispersed with CNC prepared on a mixture of Ag nano particles and nano film, and its application in spiral morphology in SERS.CNC, electrical conductivity and photothermal conversion characteristics of the electronic distribution and transfer of the photocatalytic process and local heat distribution, we speculate that these may be the main reason for the morphology and distribution of the synthesized Ag nanoparticles have great changes. The use of Ag nanoparticles prepared by this method for showing the activity of SERS is very good, and has good Good SERS homogeneity.

【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.1;O657.37

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