Study of the Structural, Electronic and Spectroscopic Properties of Graphene NanoRibbons

الموضوعات

علوم تطبيقية وتكنولوجية

الملخص

This thesis focuses on the quantum mechanical treatment of the structural, electronic, and spectroscopic properties of Graphene NanoRibbons (GNRs). Density Functional Theory (DFT) was used with the hybrid functional B3LYP/6-31G level of theory to investigate the proposed structures. These structures are divided into four groups, which are pure GNRs as a first group, fluoride- and chloride-GNRs as a third group, as well as oxidant-GNRs as a fourth group. The aim of this work concerns the effect of the nanoribbon width and studying the effects of adding different atoms on the structural and electronic properties of GNRs. The proposed structures were designed using the Nanotube Modular program, and the DFT calculations have been performed using the Gaussian09 package of programs. Before the nanostructures are reorganized and studied in the laboratory, the computational calculations provide a useful tool for estimating the structural and electronic properties to offer information about these materials. The calculated structural properties included the geometrical parameters of the structures and the standard coordinates of all atoms in each structure. The electronic properties included the total energy, electronic states (HOMO and LUMO energies), energy gap, some electronic variables, electron density, electrostatic potential, density of states, molecular polarizability, and the relative IR-spectra. The electronic variables are calculated according to the so-called orbital vertical theorem (Koopmans’ theorem). The results showed that the geometrical optimization of all pure GNRs has been found in good agreement with experimental data due to their relaxation, and for the other doped GNRs, there is no reference data. The current study supplies new data in this field. The total energy of GNRs decreased with the increasing number of atoms in the nanoribbon. In addition, the results showed that the energy gap of pure GNRs without hydrogen atoms in the terminal ends of phenyl rings increased with the increasing width of the nanoribbon, while the energy gap of pure GNRs with hydrogen atoms in the terminal ends of phenyl rings reduced with the increasing width of the nanoribbon. For the same width of the nanoribbon, the smaller one with hydrogen atoms has a larger energy gap than that without hydrogen atoms. Replacing the hydrogen atoms with fluorine and chlorine atoms in the nanoribbons leads to a few reductions in the energy gap; this is due to the linear combination of atomic orbitals of different atoms to construct the molecular orbitals. On the other hand, adding oxygen atoms instead of hydrogen atoms to construct the oxidant-GNRs changes both the HOMO and LUMO energies, and therefore, the structures in the two groups of oxidant-GNRs have various values of the energy gap depending on the number and position of the oxygen atoms in each structure. This result is the main feature of the current study, in which some of the oxidant-GNRs have insulating properties and others have semiconducting applications. The results showed that IE, EA, and EN of the pure GNRs with hydrogen atoms are greater than those of both pure GNRs without hydrogen atoms in the terminal ends of phenyl rings in the nanoribbons, while H is decreased and S is increased with adding hydrogen atoms except for the first smaller nanoribbon, which has inverse behavior. All the electronic variables of fluorine and chloride-GNRs are smaller than those of pure GNRs except S, which increased with the addition of fluorine and chlorine atoms. Moreover, the degeneracy of energy levels of each structure depends on the width of the nanoribbon, the type, number, and position of atoms in the nanoribbon. In general, the results of this study refer to the fact that the proposed constructed structures have various electronic properties. It was found that there are different shapes of electrostatic potential and total electron density according to the symmetric and asymmetric distribution areas of charges in each structure. The results showed that the pure GNRs without hydrogen atoms have molecular polarizability greater than that of the pure GNRs with hydrogen atoms. So, the molecular polarizability increased with the increasing width of the nanoribbons. Adding fluorine, chlorine, and oxygen atoms instead of hydrogen atoms gave the structures different values of molecular polarizability depending on the type, position, and number of atoms in each structure. The calculated values of frequency of stretching and bending vibrations from IR-spectra of the two groups of pure GNRs showed good agreement with experimental results of the phenyl ring compounds, while for the fluorine, chloride-GNRs, and oxidant-GNRs, this study supplies new data in this aspect.

روابط وملفات

التعريف والنوع

رقم الوثيقة

05513518-1ae2-459d-b519-f80e9f200b3f

رقم العقد

0

نوع الوسائط

Crawler

نوع المحتوى

الرسائل العلمية

صيغة المصدر

رسائل ماجيستير

نوع الملف

pdf text

أسماء الملفات

998302_1.pdf

بيانات النشر

ترجمة العنوان

دراسة الخواص التركيبية الالكترونية والطيفية لشرائط الكرافين النانوية

ألقاب المؤلفين

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اللغة

English

المصدر والدورية

اسم المصدر

Study of the Structural, Electronic and Spectroscopic Properties of Graphene NanoRibbons

المحتوى والصفحات

عدد الصفحات

0

كلمات الباحثين

Graphene, Graphene Nanoribbons, Density Functional Theory, Energy Gap, HOMO, LUMO, Molecular Polarizability, Electronic Structure, IR Spectra, Substituted Atoms.

إشراف وإعداد

الإشراف

حامد ابراهيم عبود, رباب سعدون عبدون

الإعداد

ايات عبد السادة يوسف طعيمة

الاقتباسات الببليوغرافية