本文選題：碳納米線圈　切入點：可控制備　出處：《大連理工大學》2017年博士論文　論文類型：學位論文

【摘要】：近些年,隨著納米技術(shù)的日益成熟,人們成功制備出了多種具有不同形貌、結(jié)構(gòu)的低維碳納米材料及其復合材料。這些碳納米材料展示出了優(yōu)異的物理和化學性質(zhì),被廣泛地應用于能源、傳感、電子器件等領域,極大地促進了科技的發(fā)展。碳納米線圈(CNC)做為一種具有三維螺旋結(jié)構(gòu)的碳納米材料,展示出很多與碳納米管、石墨烯等低維碳材料所不同的物理和化學性質(zhì)。大量研究表明CNC的特性是與其線圈直徑、螺距以及結(jié)構(gòu)息息相關(guān)的,但目前對CNC的調(diào)控尚不理想,如何進一步實現(xiàn)對CNC的直徑、螺距以及結(jié)構(gòu)的調(diào)控仍然是CNC制備技術(shù)上的一大挑戰(zhàn)。本論文通過研究CNC的直徑隨反應時間的變化特征以及對CNC生長經(jīng)驗公式的擬合,得出了催化劑顆粒大小與其活性和壽命的關(guān)系。并通過調(diào)控催化劑膜厚以及利用單層氧化硅小球作為基板來調(diào)控催化劑顆粒的空間尺寸與分布,從而實現(xiàn)了對CNC的直徑、螺距以及結(jié)構(gòu)的調(diào)控,同時還對其成長機理進行了分析研究。此外,通過將磁控濺射與光催化相結(jié)合的方法對所合成的Ag納米顆粒的分布與尺寸進行優(yōu)化調(diào)控,并在分散有CNC的TiO_2薄膜表面成長出Ag納米顆粒與納米片的混合體,探索了其在表面增強拉曼散射光譜(SERS)領域中的應用。本論文主要研究工作如下:(1)CNC的線圈直徑、螺距以及結(jié)構(gòu)的調(diào)控:首先,研究了反應時間與CNC的直徑分布的依賴關(guān)系,發(fā)現(xiàn)隨著反應時間的增加,具有較大直徑的CNC的比例在逐漸增加。并對碳產(chǎn)物的產(chǎn)量與反應時間的關(guān)系進行了研究,得到了其生長經(jīng)驗公式。研究發(fā)現(xiàn)該經(jīng)驗公式具有三組不同的催化劑特征參量。這是由于在CNC的成長過程中其催化劑顆粒的大小以及活性的不均一性造成的。尺寸較小的催化劑顆粒具有比較高的活性,但是其催化壽命卻比較短,其在CNC成長初期發(fā)揮主導作用。而尺寸較大的催化劑顆粒具有的催化活性比較低,但是其催化壽命比較長,隨著反應時間的推移,其逐漸占據(jù)主導地位。其次,在保持Sn、Fe摩爾比不變的條件下,通過控制Sn/Fe催化劑的膜厚來調(diào)控催化劑顆粒的大小以及聚集程度,實現(xiàn)了對CNC的線圈直徑、螺距以及結(jié)構(gòu)的調(diào)控。研究發(fā)現(xiàn)隨著催化劑膜厚的降低,CNC的形態(tài)結(jié)構(gòu)逐漸從彈簧狀向辮狀變化,CNC的直徑逐漸減小,并且其石墨化程度越來越高。當催化劑膜厚為3nm以下時,所合成的碳產(chǎn)物由CNC轉(zhuǎn)變?yōu)樘技{米纖維以及扭曲狀碳納米線,由此可知保證高效制備CNC的最小催化劑膜厚為3到7nm之間。最后,利用單層氧化硅小球來限制催化劑顆粒的空間分布及尺寸,并為CNC的成長提供了必要的根部固定作用,從而成功實現(xiàn)了對CNC的線圈直徑的調(diào)控。研究發(fā)現(xiàn)CNC的平均直徑隨著氧化硅小球直徑的降低而減小。同時,采用氧化硅小球有利于減小副產(chǎn)物層的比例,提高了 CNC的產(chǎn)率。此外,采用氧化硅小球為模板來模樣化Sn/Fe催化劑薄膜的方法,實現(xiàn)了 CNC直徑的進一步降低。(2)小直徑碳納米線圈制備的探索:首先,研究了不同的Sn、Fe濺射次序?qū)Υ呋瘎╊w粒尺寸、空間分布以及碳產(chǎn)物形態(tài)的影響。研究發(fā)現(xiàn)按照Fe、Sn的先后次序濺射而形成的催化劑薄膜,經(jīng)過煅燒后無法形成有效的催化劑顆粒和聚集,從而無法生長出CNC;按照Sn、Fe先后次序濺射而形成的催化劑薄膜,煅燒后形成了顆粒狀的分布,并在化學氣相沉積的過程中生長出了CNC。其次,研究了不同Sn、Fe比例對CNC直徑的影響,發(fā)現(xiàn)CNC的直徑隨著Sn膜厚度的降低而減小。在此基礎上,我們采用單一的Fe薄膜作為催化劑,利用單層氧化硅小球?qū)Υ呋瘎╊w粒的形態(tài)和分布的限制以及為CNC的成長提供必要的根部固定作用,對小直徑CNC的制備展開了初步的探索。實驗結(jié)果表明利用此種方法成功地合成出了直徑在50nm以下的小直徑CNC,并且其產(chǎn)率會隨著氧化硅小球直徑的減少而增加。(3)CNC對光催化制備Ag納米顆粒及其SERS活性的影響:通過在TiO_2薄膜上預濺射高密度的Ag納米種子的方法來調(diào)控光催化過程中電子的傳輸和分布,從而提高Ag納米顆粒的成核密度,隨后利用光催化還原硝酸銀的方法在Ag納米種子上制備出了高密度的Ag納米顆粒并控制其顆粒尺寸,以上方法有效地增加了 SERS活性位點,極大地提高了對R6G分子的探測靈敏度。此外,我們利用時域有限差分法對激光照射情況下粒子表面的電場強度進行理論模擬,研究了 Ag納米顆粒的尺寸及間距對其SERS效果的影響。在以上工作的基礎上,通過光催化的方法在分散有CNC的TiO_2薄膜上成功制備出了 Ag納米顆粒與納米片的混合體,并將其應用于SERS中。CNC的螺旋形貌、導電性以及光熱轉(zhuǎn)化特性影響了光催化過程中的電子分布與轉(zhuǎn)移以及局部熱量分布,我們推測這些可能是所合成的Ag納米顆粒的形態(tài)和分布產(chǎn)生了很大變化的主要原因。利用此法制備出的Ag納米顆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.

【學位授予單位】：大連理工大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TB383.1;O657.37

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本文編號：1602885