Schematic presentation of the formation of the C2N-h2D crystal with edge groups and reaction thermodynamics. SEM images of the C2N-h2D crystal: (a) As-prepared sample. c) Edge view of heat-treated flakes. SEM images obtained from cross-sections of the C2N-h2D crystal films on SiO2(300 nm)/Si wafer with different thickness: (a) 330.
Large-Scale Synthesis of Pure and Stable Hexaaminobenzene Trihydrochloride
- Abstract
- Introduction
- Materials and Instrumentation
- Synthesis of 2,4,6-trinitroaniline (TNA, 1)
- Synthesis of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB, 2)
- Synthesis of hexaaminobenzene trihydrochloride (HAB, 3)
- Single crystal X-ray diffraction study
- Results and Discussion
- Conclusions
- References
I have extensively researched and used the literature to achieve high purity HAB by using some of these conventional methods for the reduction of nitro groups on TATB (Figure 1.2a). However, the quality of the HAB trihydrochloride crystal is the best among the reported protocols, while the crystal quality is still insufficient for high-quality polymer synthesis (Figure 1.2c). The complete crystal structure of HAB trihydrochloride was solved for the first time by single-crystal X-ray crystallography (Figure 1.5e and 1.5f).
C 2 N holey two-dimensional crystal
Abstract
Introduction
The band gap of the newly fabricated 2D crystal with evenly distributed holes and nitrogen atoms was studied using various experimental techniques and density functional theory (DFT). Moreover, the synthesis of the N-containing 2D crystal with holes is believed to be a basic material for the coming progress of versatile 2D crystals.
Materials
Instrumentation
Synthesis of the C 2 N-h2D crystal (nitrogen containing holey 2D crystal)
C 2 N-h2D crystal as a heterogeneous catalyst (Model reaction)
First-principle calculations
STM experiments
Results and Discussion
The powder x-ray diffraction (XRD) pattern of the C2N-h2D crystal reveals a lightly layered structure with high crystallinity. The narrower d spacing of the C2N-h2D crystal is thought to originate from uniformly distributed nitrogen atoms. Analysis of properly prepared C2N-h2D crystal: (a) Powder XRD pattern from the prepared sample; (b) XPS survey spectrum showing C1, N1, and O1.
XPS recording spectrum of the heat-treated C2N-h2D crystal at 700 °C, showing C 1s, N 1s and reduced O1s compared to as-prepared spectrum (Figure 2.4b). Atomic-resolution imaging of C2N-h2D crystal: (a) an STM topography image of C2N-h2D on Cu(111); (b) Theoretically calculated image; (c) Topographic elevation profile along the sky blue line marked in (a); (d) 2D fast Fourier transform of (a). The first-principles density functional theory (DFT) calculations were also done to look at the electronic structure of the C2N-h2D crystal.
Optical images of the C2N-h2D crystals on a SiO2/Si wafer: (a) The C2N-h2D crystal can be obtained over micron scale size. Atomic force microscopy (AFM) analysis of the C2N-h2D crystal flakes indicated that the average (mean) thickness of the sample (out of 10 samples) was 8.0 ± 3.5 nm (Figure 2.16a), implying that multilayers of the C2N-h2D crystal are stacked. Typical transmission curves of the C2N-h2D crystal FET devices are presented in Figure 2.16c, and the electrical properties of the C2N-h2D crystals are summarized in Table 2.2.
Schematic representation of the Knoevenagel condensation reaction of terephthaldehyde and malononitrile in the presence of the C2N-h2D crystal as reaction catalyst.
Conclusions
Band gap of monolayer and bilayer graphene doped with aluminum, silicon, phosphorus, and sulfur. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane wave basis set.
Abstract
Introduction
Materials & Instrumentations
Synthesis of carbonized single crystal rods (C 3 N framework)
Measurement of HOMO and LUMO gap
The electrochemical measurements of C3N show an onset oxidation potential of +1.35 V and onset reduction potential of -1.32 V vs.
Results and Discussion
The micro-Raman spectrum of the C3N framework shows prominent peaks at 1510 and 1370 cm-1 corresponding to the D and G bands, respectively. This weight loss is a partial removal of the ammonium chloride (NH4Cl) to form a 2D PANI-like structure. To check the nature of the gases released during annealing of the HAB monomer, I performed Py-GC-MS (Pyrolysis coupled GC-MS).
When heated, ammonia is released and detected by moist pH paper, which turns dark green at the mouth of the test tube (Figure 3.6d). High-resolution SEM shows more like graphitic structure with stacked layered and highly wrinkled morphology, which is attributed to the 2D nature of the C3N structure and sheet-like appearance. The hexagonal shape of the HAB crystals is well preserved in the structure after charring.
Energy dispersive spectroscopy (EDS) of the SEM reveals the elemental composition of the materials, indicating the complete removal of chlorides from the material (Figures 3.8 and 3.10). SEM images of the pure HAB crystals show a well-defined hexagonal rod-like framework of several crystals. SEM images of the C3N framework at different magnifications show the stacked layers and the prominent hexagonal rod-like morphology is well preserved after annealing at 500 °C.
The molecular structure of C3N was investigated by UHV low-temperature scanning tunneling microscopy (Specs. JT-STM) at 77 k.
Conclusions
The conversion of polyaniline nanotubes to nitrogen-containing carbon nanotubes and their comparison with multi-walled carbon nanotubes.
Fe-Cocooned C 2 N-h2D Structures as Efficient Oxygen Reduction Catalysts
- Abstract
- Introduction
- Materials
- Instrumentation
- Synthesis of the iron containing holey 2D crystal (Fe@C 2 N-h2D)
- Cyclic voltammogram
- Results and Discussion
- Conclusions
- References
The resulting Fe@C2N-h2D exhibits unusual catalytic activity with excellent stability in both acidic and alkaline media. The resulting Fe@C2N-h2D is colored black and shows a strong magnetic response (Figure 4.1b), indicating the presence of Fe nanoparticles. Energy dispersive spectroscopy (EDS) combined with SEM (SEM-EDS) was used to confirm the elemental composition in the Fe@C2N-h2D (Figure 4.2).
Energy dispersive X-ray spectroscopy (EDS) spectrum of Fe@C2N-h2D showing elemental mapping and composition (C, N, O and Fe) from SEM image. Surprisingly, the capacitance of Fe@C2N-h2D was more than twice that of the commercial Pt/C catalyst under acidic and basic conditions (Figures 4.8 and 4.9). Cyclic stability of samples before and after 200 cycles in 1 M aq. a) Fe@C2N-h2D under nitrogen conditions (b) Pt/C under nitrogen-saturated atmosphere (c) Fe@C2N-h2D under oxygen-saturated conditions (d) Pt/C under oxygen-saturated environment.
Cyclic stability of the samples before and after 200 cycles in 1 M aq. a) Fe@C2N-h2D in nitrogen condition (b) Pt/C in nitrogen saturated atmosphere (c) Fe@C2N-h2D in oxygen saturated condition (d) Pt/C in oxygen saturated environment. Stability test of the Fe@C2N-h2D in H2SO4 and KOH, both in oxygen and nitrogen atmospheres, after 10,000 cycles. These results are indicative of the promising activities of the Fe@C2N-h2D as a stable ORR catalyst in the DMFC.
Based on the results, Fe@C2N-h2D outperforms the Pt/C as the cathode catalyst for ORR in fuel cells.
C 2 N-h2D polymer encapsulated cobalt oxide catalyst for hydrogen evolution
- Abstract
- Introduction
- Materials
- Instrumentation
- Synthesis of Co@C 2 N
- Catalyst test
- Catalytic reduction reaction
- Results and discussion
- Conclusions
- References
In a typical experiment, an oven-dried flask containing 10 mg of Co@C2N catalyst was evacuated and effectively flushed with nitrogen. After annealing, the material shows a strong attraction towards an external magnet (Figure 5.1b). a) Schematic representation of Co@C2N synthesis; (b) behavior of Co@C2N in a magnetic field. Scanning Electron Microscope (SEM) and High Resolution Transmission Electron Microscope (HR-TEM) were used to study the morphology and provide deep insight into the structure of the Co@C2N material (Figures 5.1c,d,e).
HR-TEM study of the Co@C2N material revealed the presence of well-dispersed particles in the C2N polymer framework (Figure 5.1d) with an average diameter of about 10-40 nm. Co@C2N energy dispersive X-ray spectroscopy (EDS) showing the elemental mapping and composition (C, N, O and Co) from the SEM image. SEM coupled energy dispersive spectroscopy (SEM-EDS) was also used to confirm the elemental composition in the Co@C2N (Figure 5.2).
Uniform distribution of Co nanoparticles in the Co@C2N framework was detected by elemental mapping in the SEM-EDS analysis. EDS and XPS (Figure 5.5a) study spectra of the Co@C2N material show the presence of C, N, O and Co and. Deconvoluted XPS spectrum (Figure 5.4) of Cobalt reveals that Co in the Co@C2N material is mainly in the form of Co+2 state (inset in Figure 5.5a)33.
The X-ray powder diffraction (XRD) pattern of Co@C2N after annealing at 450 °C reveals that its structure is highly crystalline (Figure 5.5b).
Organic Ferromagnetism from Self-Polymerized TCNQ
Abstract
Introduction
Materials & Instrumentations
Scanning electron microscope (SEM) images were taken on a Nanonova 230 field emission scanning electron microscope FEI, USA.
Self-Polymerization of 7,7,8,8-tetracyanoquinodimethane (TCNQ)
Electron spin resonance (ESR) measurements
Results and discussion
Trimerization of the cyano (-CN) groups in TCNQ leads to the formation of a triazine framework in the presence of TFMSA 21. The data obtained in nitrogen (N2) and air environments indicated good stability of the material (Figure 6.4a) . The bulk morphology of the p-TCNQ was investigated by field emission scanning electron microscopy (FE-SEM).
The ESR spectrum clearly provides unequivocal evidence for the existence of free radicals in p-TCNQ. Solid state NMR spectra: (a) as prepared sample; b) after annealing at 400 °C, indicating the destruction of the structure and the radicals. To rule out the possibility of the presence of metallic impurities in the p-TCNQ structure, I performed ICP-MS to identify the trace metal content of the material.
The temperature dependence of the field-cooled (FC) magnetization at H = 1000 Oe is depicted in Figure 6.12a. Determination of the angular momentum quantum number J via Brillouin function fitting: (a) the estimated Mpara component as a function of field H at 5 K (black symbols). The best fitting parameter for the critical exponent was 0.48, which is close to the mean field theory value.
This value of the magnetic moment corresponds to the fraction of non-interacting spins mol-1 (about one in 675 TCNQ units).
Conclusions
Jong-Beom Baek for his guidance, kindness, encouragement and extremely helpful attitude during my exhausting doctoral research work, without his assistance and guidance the culmination of this project would have been almost a dream for me. Hyung Joon Shin for their constant help and discussions with collaborative opportunities, their guidance will always help me in my future research work. Sun-Min Jung, she looks angry young girl, but in reality she is very kind and kind-hearted, Ms.
In short, their cooperation enabled me to overcome the difficulties I encountered in my research work. My special, heartfelt and heartfelt thanks to my family, parents, brothers and sisters who always prayed for my success and bright future. Javeed Mahmood, Minbok Jung, Dongbin Shin, Hyun-Jung Choi, Jeong-Min Seo, Jung Min Park, Dongwook Kim, Jung-Woo Yoo, Myoung Soo Lah, Noejung Park, Hyung-Joon Shin, Jong-Beom Baek, 2D C3N structure obtained from carbonized single crystals submitted.
Javeed Mahmood, Hyun-Jung Choi, Gyung-Joo Sohn, Sun-Min Jung, Jeong-Min Seo, Jungmin Park, Jung-Woo Yoo, and Jong-Beom Baek, Fe-Cocooned C2N-h2D Structures as Efficient Oxygen Reduction Catalysts . Javeed Mahmood, Sun-Min Jung, Seok-Jin Kim, Jungmin Park, Jung-Woo Yoo, and Jong-Beom Baek, C2N-h2D Network Polymer-Enclosed Cobalt Oxide Catalyst for Hydrogen Evolution, Chemistry of Materials, i accepted. Javeed Mahmood, Jungmin Park, Hyun-Jung Choi, Jeong-Min Seo, Jung-Woo Yoo, Jong-Beom Baek, Organic Ferromagnetism by Self-Polymerized TCNQ, Submitted.
Javeed Mahmood, Eun Kwang Lee, Joon Hak Oh, Jong-Beom Baek, Synthetically engineered polymer with extremely high charge carrier mobility, manuscript in preparation.
