一些碳基纳米材料的发光、光热特性研究

发布时间：2018-04-20 23:32

本文选题：碳纳米颗粒 + 氧化和还原石墨烯　；参考：《南京大学》2015年博士论文

【摘要】：认识和理解纳米材料的结构、电子态和光与物质相互作用的基础物理过程,对于调控其光电性质以及拓展在光电信息、生物医学和能源环境等方面的应用具有重要的指导意义。发光谱(PL)、激发谱(PLE)和时间分辨光谱(TRPL)等荧光光谱技术是研究纳米材料光电性质及相关物理效应的重要工具。碳基光电纳米材料具有许多非常新颖的光电磁效应,其构成元素储量丰富,环境友好,生物兼容,引起了人们广泛的关注。本文以荧光光谱技术为主要研究手段,结合各种微结构和谱学表征技术以及第一性原理的计算,探究氧化石墨烯(GO)、还原的氧化石墨烯(RGO)、碳纳米颗粒(CNDs)和联苯丙二氨酸(FF)纳米管的光电和光热特性,获得了如下的主要研究结果：1、通过自上而下和自下而上的方法分别得到了RGO和CNDs两种碳纳米结构。两种结构的发光特性表现出很多相似之处,例如,发光峰随着激发光波长变大而逐渐红移,480-550 nm发光单调均匀地移动但是蓝光部分的移动不明显。根据光谱特征,我们将非对称的PL峰Gaussian分解为两个子峰。通过高分辨透射电镜、傅里叶变换红外光谱和拉曼光谱等表征手段对GO到RGO的还原过程和CNDs的生长过程中的结构演变进行分析,结合第一性原理的计算,首次提出在这一类碳纳米材料中存在两种发光中心。PL的蓝光部分是拓扑缺陷结构导致的发射,另一部分是大家普遍接受的由sp2杂化的碳团簇尺寸效应导致的依赖于激发光波长的长波长发射。2、通过制备MnO2修饰的GO作为中间产物,进一步水热处理还原GO为RGO的同时,实现了Mn离子的介入,得到了锰离子键合的RGO。发光谱的研究发现锰离子键合的RGO相对于原来的RGO,500-600 nm的长波长发光得到了非常显著的增强,从而使材料的发光波长可在430到600 nm范围内连续可调,由此找到了一种调控RGO发光的有效途径,对推动其在光电领域的应用具有重要意义。光谱分析以及密度泛函的计算揭示了长波长发光的增强起源于Mn2+和RGO中sp2团簇之间的共振能量转移。3、通过系统的实验检验,澄清了文献中大量报道的关于石墨烯量子点(GQDs)上转换发光的争论,证实了氙灯激发石墨烯量子点的上转换荧光实质上是单色仪引起的假象。因此基于其上转换性质来设计光催化、太阳能电池等结构也是不可行的。此外,我们还在高功率飞秒脉冲激光激发下观察到真正的上转换发光,发光强度与激发功率成二次关系,证实了双光子过程的存在。4、研究了P25型号的二氧化钛颗粒与RGO组成的复合纳米结构对亚甲基蓝(MB)的光降解过程,通过滤光片选择特定的光照波段,单独研究了近红外光(NIR)对光降解过程的影响。结果表明RGO的加入除了能吸附更多污染物、吸收更多光子以及传导电子之外,RGO在NIR激发下的光热效应会使得电子在RGO上的传输更容易,该研究提示我们,可以通过利用RGO的光热效应来提升RGO复合纳米结构的光催化表现。5、通过对联苯丙二氨酸(FF)纳米管晶体结构的分析,揭示了其自发极化起源于氢键的有序排列；PL谱的分析表明,存在明显的光诱导的类量子限制Stark效应,这使得这种强的自发极化可在强光的照射下发生反转。基于以上结果,我们精细地测量了FF微米管的P-E曲线,清楚地观察到强光照射下明显的极化饱和特征,首次在实验上证实了FF微米管沿轴向铁电性的存在。
[Abstract]:The basic physical processes of understanding and understanding the structure of nanomaterials, the electronic states and the interaction of light and matter are of great guiding significance for the regulation of their photoelectric properties and their applications in the optoelectronic information, biomedicine and energy environment. Luminescence spectroscopy (PL), excitation spectrum (PLE) and time resolved spectroscopy (TRPL) and other fluorescence spectroscopy techniques It is an important tool to study the photoelectric properties and related physical effects of nano materials. Carbon based optoelectronic nanomaterials have many very novel optical and electromagnetic effects. They have rich reserves, friendly environment and biocompatibility, which have aroused widespread concern. This paper uses fluorescence spectroscopy as the main research method, combined with various microstructures and spectra. The characteristics of graphene oxide (GO), reduced graphene oxide (RGO), carbon nanoscale (CNDs) and diphenyl malonic acid (FF) nanotubes were investigated by the study of the characteristics of graphene oxide (GO), reduced graphite oxide (RGO), carbon nanoscale (CNDs) and diphenyl malonic acid (FF) nanotubes. The following main research results were obtained: two kinds of carbon and RGO, respectively, were obtained by top-down and bottom-up methods. The luminescence characteristics of the two structures show a lot of similarities, for example, the luminescence peak gradually redshifts with the excitation of the light wave length, and the 480-550 nm luminescence is monotonically and evenly moved, but the movement of the blue light part is not obvious. According to the spectral characteristics, we decompose the asymmetric PL peak Gaussian into two sub peaks. The reduction process of GO to RGO and the structural evolution of CNDs during the growth of CNDs are analyzed by means of electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. In combination with the calculation of the first principle, the blue light of two kinds of luminescent center.PL in this kind of carbon nanomaterials is first proposed, and the other is the structure of the topology defect structure. One part is the long wave long wavelength emission.2, which is generally accepted by the SP2 hybrid cluster size effect, which depends on the excitation wavelength. By preparing the MnO2 modified GO as the intermediate product and the further hydrothermal treatment of GO to RGO, the interference of the Mn ion is realized, and the manganese ion bonded RGO. luminescence spectrum has been found to find manganese. The long wavelength luminescence of the ion bonded RGO is very significant relative to the original RGO, 500-600 nm long wave length luminescence, which makes the luminescent wavelength of the material continuously adjustable within the range of 430 to 600 nm, thus finding an effective way to regulate the RGO luminescence. It is of great significance to promote its application in the photoelectric collar. The degree functional calculation reveals that the enhancement of the long wave length luminescence originates from the resonance energy transfer.3 between the SP2 clusters in Mn2+ and RGO. Through the experimental test of the system, the argument about the upconversion luminescence of the graphene quantum dots (GQDs), which is reported in the literature, is clarified. It is confirmed that the upconversion fluorescence of the graphene quantum dots excited by the xenon lamp is essentially the same. Therefore, it is not feasible to design the photocatalyst based on its upconversion properties. In addition, we have also observed real upconversion luminescence under high power femtosecond pulse laser excitation, the luminescence intensity and the excitation power have two relations, which confirmed the existence of.4 in the two-photon process, and studied the P25 The photodegradation process of methylene blue (MB) by the composite nano structure of titanium dioxide and RGO, and the effect of near infrared light (NIR) on the photodegradation process by selecting a specific light wave band through a filter. The results show that the addition of RGO can absorb more pollutants, absorb more photons and conduction electrons. The photothermal effect of RGO under the excitation of NIR makes the transmission of electrons easier on RGO. This study suggests that we can enhance the photocatalytic performance of RGO nanostructures by using the photothermal effect of RGO. By segregation of the crystal structure of the dianine (FF) nanotube, the spontaneous polarization of the hydrogen bond is revealed by the segregation of the crystal structure of the dianine (FF) nanotube. The analysis of PL spectra shows that there is an obvious light induced quasi quantum confinement Stark effect, which makes this strong spontaneous polarization reversible under strong light. Based on the above results, we have fine measured the P-E curves of the FF microtubules and clearly observed the obvious polarization saturation characteristics under strong illumination, for the first time in the experiment. The existence of the axial ferroelectric properties of the FF microtubules has been confirmed.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1;TQ127.11

【共引文献】