This Thesis describes the application of niobium oxide and niobium phosphate as solid acids for conducting continuous flow reactions, such as the Friedel-Crafts Reaction and the Skraup Reaction, and also as supports for photosensitiser immobilisation. Chapter 1 introduces the concepts of green and sustainable chemistry, and give a review of niobium and niobium compounds, especially niobium oxide and niobium phosphate as well as their applications. A summary of flow chemistry is also presented. The continuous flow systems used to conduct the work of this Thesis are described in Chapter 2. Chapter 3 introduces continuous alkylation of aniline with dimethyl carbonate or methanol over niobium solid acids. The synthesis process is automated by a self-optimisation system to search the best conditions for different products, including the NH2 group methylation product monomethyl aniline and dimethyl aniline, and the Friedel-Crafts alkylation product N,N-dimethyl-p-toluidine. Chapter 4 describes the first exploration of the continuous Skraup synthesis of quinolones with heterogeneous catalyst niobium phosphate. A dissymmetrics substituted quinoline compound, 4-(quinolin-6-yl methyl)aniline, was synthesized, and its crystal was grown and the structure was determined by crystallographic analysis for the first time. Chapter 5 discussed the immobilisation of a photosensitiser meso-tetraphenylporphyrin on niobium solid acids, and the activity of these supported photocatalysts in continuous photo-oxidation, including the photo-oxidation of α-terpinene to ascaridole and the semi-synthesis of an antimalarial drug, artemisinin ART. Finally, Chapter 6 summarises the work described in this Thesis and examines the success of the techniques and approaches discussed. A summary of potential routes for further study is also presented.

This thesis addresses the concept of atomically precise manufacturing and aims to examine some likely aspects of the necessary infrastructure and knowledge that will be required from a theoretical standpoint. By way of introduction, I trace the history of Science Fiction's influence on scientific research and examine some examples that have specifically inspired the thinking behind nanoscience and nanotechnology. More serious speculation, both in favour of and arguing against the possibility of bottom-up manufacturing is also discussed. I look at two schools of thought; directed assembly, typified by the ambition to assemble molecular structures piece by piece and self assembly, where networks of molecules form into arrays on substrates, imparting novel properties. Various methodologies and tools available to the nanotechnologist are examined. Density functional theory, as employed in the AIMpro code, and Molecular Mechanics are discussed, particularly in respect of their strengths and weaknesses for use in simulating the kind of nanoscale processes appropriate to nanomanufacturing. The theoretical basis behind scanning tunneling microscopes is also examined, with particular attention paid to their potential for upscaling in the future. Some components found within scanning tunneling microscopes are simulated using Density Functional Theory. Models of pure tungsten tips are studied at various levels of complexity in order to decide upon a reasonable compromise between accuracy and ease of computation. The nature of the interlayer interaction in few layer graphenes is examined and pristine and defected graphitic surfaces, are studied with a view towards their use as nano-workbenches. Their images as produced in scanning tunneling microscopes are simulated. Density Functional Theory is applied to organic molecules self-assembling on metallic substrates. Specifically, tetracene on a clean copper surface and on an oxygen-terminated copper surface is studied. Finally, I discuss the significance of the results of each section, taken individually and as a whole, and try to put it into perspective regarding the practicality of actually employing this paradigm realistically in the near future.

本论文介绍了一种基于扫描共聚焦显微镜和微流反应器用于研究化学振动子同步的系统。这个系统利用300微米的PNIPAm胶体颗粒作为振动子，Ru(vmbpy)(bpy)₂(PF₆)₂ 被参杂到振动子里充当BelousovZhabotinsky（BZ）振荡反应的催化剂。扫描共聚焦显微镜具有很高的灵敏度，可以给出高质量的图片以供研究分析。通过实验证明低于56W/cm²强度的扫描激光对BZ反应没有影响。这里所运用的微流反应器包括两个部分，PMMA材质的微池和PDMS材质的流道。此反应器可通过流道不停地补充BZ反应的反应物从而保证振荡的一致性。 / 通通过此系统，我们可以研究不同的两个振动子的同步问题。在实验中，振动子间的同步是由两者间的距离决定的。振动子在靠近时同步在分开至临界距离以外处不同步。另外，我利用COMSOL来模拟实验中的现象，发现模拟的结果和实验中的现象十分吻合。 / In this thesis, I present an experimental platform based on laser scanning confocal microscopy (LSCM) and continuous flow microreactor (CFMR) to study coupled chemical oscillators. PNIPAm gel particles around 300 micron were synthesized in the microfluidic device as the oscillators. Ru(vmbpy)(bpy)₂(PF₆)₂ was used as the catalyst of the BelousovZhabotinsky (BZ) reaction. The LSCM offers a good signal-to-noise ratio and better imaging quality. We demonstrated that the scanning laser with the power below 56W/cm² had no influence to BZ reaction. The CFMR, consisting of the PMMA microwell and the PDMS microchannel, can maintain the oscillation of the oscillators with a continuous supply of the BZ mixture. / The synchronization of the double heterogeneous oscillators was studied by the platform. The coupling intensity was controlled by changing the distance between the two oscillators. Results showed that the synchronization occurred as the oscillators were close and was lost as the oscillators were separated beyond a critical distance. The results of the numerical simulation by COMSOL agreed well with the experimental observation. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Guo, Dameng. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 40-41). / Abstracts also in Chinese. / Abstract --- p.i / 摘要 --- p.ii / Acknowledgement --- p.iii / Table of contents --- p.iv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Synchronization of chemical oscillating systems --- p.1 / Chapter 1.2 --- The Belousov-Zhabotinsky reaction --- p.4 / Chapter 1.2.1 --- FKN model --- p.5 / Chapter 1.2.2 --- Effect of light illumination on ruthenium catalyzed BZ reaction --- p.7 / Chapter 1.2.3 --- Luminescence of ruthenium catalyzed in the BZ reaction --- p.8 / Chapter 1.3 --- Oscillators based on the BZ reaction --- p.9 / Chapter 1.4 --- Detection methods for the BZ oscillating systems --- p.10 / Chapter 1.4.1 --- Ion selective electrode and optical microscopy --- p.10 / Chapter 1.4.2 --- Objective of the research --- p.10 / Chapter Chapter 2 --- LSCM and continuous flow microreactor based platform --- p.12 / Chapter 2.1 --- Introduction --- p.12 / Chapter 2.2 --- Experimental --- p.13 / Chapter 2.2.1 --- The fabrication of the oscillators --- p.13 / Chapter 2.2.2 --- The fabrication of the CFMR --- p.14 / Chapter 2.2.3 --- The detection method --- p.16 / Chapter 2.3 --- Results and discussions --- p.16 / Chapter 2.3.1 --- The comparison of PMMA and PDMS microreactors --- p.16 / Chapter 2.3.2 --- The flow rate of the BZ mixture to maintain the oscillation --- p.18 / Chapter 2.3.3 --- The size of the microreactor --- p.19 / Chapter 2.3.4 --- The factors to reduce the influence of the laser on the oscillators --- p.21 / Chapter 2.4 --- Conclusions --- p.23 / Chapter Chapter 3 --- The studying of the synchronization of the double oscillators --- p.24 / Chapter 3.1 --- Introduction --- p.24 / Chapter 3.1.1 --- Kuramoto model for illustrating the synchronization of double oscillators --- p.24 / Chapter 3.1.2 --- Transition from disorder to synchronization --- p.25 / Chapter 3.2 --- Experimental and simulation --- p.26 / Chapter 3.2.1 --- The dispensing and detection of the oscillators in the microreactor --- p.26 / Chapter 3.2.2 --- The simulation model --- p.27 / Chapter 3.3 --- Results and discussion --- p.28 / Chapter 3.3.1 --- The controlling of the coupling intensity --- p.28 / Chapter 3.3.2 --- The results of the synchronization --- p.30 / Chapter 3.3.2.1 --- Synchronization --- p.30 / Chapter 3.2.2.2 --- The critical distance for the synchronization and the transition --- p.31 / Chapter 3.3.3 --- The results of the simulation --- p.34 / Chapter 3.4 --- Conclusion --- p.35 / Chapter Chapter 4 --- Conclusion --- p.37 / Chapter 4.1 --- Summary --- p.37 / Chapter 4.2 --- Discussions and future perspectives --- p.38 / Reference --- p.40 / Appendix --- p.42 / Chapter 1. --- Code in Matlab for calculating the RGB value of ROI in the images from the LSCM --- p.42 / Chapter 2. --- The power of the laser --- p.43 / Chapter 2.1 --- The power of the laser in the LSCM --- p.43 / Chapter 2.2 --- The irradiation power on the oscillators --- p.44 / Chapter 3. --- The energy transferred to the oscillator --- p.44 / Chapter 4. --- The model in COMSOL --- p.45

Systems known as complex materials have key attributes that contribute to their designation as "complex''. For example, evolving dynamical properties add complexity, as is observed in supercooled liquids. Polymers and proteins are structurally complex as they can fold in different conformations, with these different conformations affecting different biological functions or physical properties. Complex materials generally have interesting macroscopic properties that are difficult to predict from their microscopic (molecular) constituents. The connection between microscopic features and macroscopic properties in these materials has been a subject of study for decades, yet the ability to wield strong predictive power in these materials remains elusive. Imaging can provide information in both space and time necessary to understand how the microscopic details in these materials yield the observed macroscopic properties. Moreover, time-sequenced imaging allows one to understand how these properties might evolve. To image these details however, requires high resolution in both time and space. Unfortunately, obtaining images and extracting information from these images becomes quite difficult as the length scales of interest become small, especially when signal-to-background ratios are low. My dissertation work addresses the challenge of extracting such information by developing quantitative methods to circumvent obstacles related to obfuscation from low signal as well as the diffraction limit, with high-throughput and high-resolution. I apply these techniques towards the study of the following complex materials via imaging: (1) single molecules rotating in a supercooled liquid (2) conjugated polymers containing multiple emitters within the diffraction limit (3) solvent vapor annealing mediated conjugated polymer aggregation and (4) collagen gels during their formation and perturbation. The first chapter describes how the local dynamics in a supercooled liquid may be assessed by the rotations of single-molecule probes. To resolve rotations however, requires splitting the fluorescence signal from single-molecules into orthogonal polarizations thereby reducing the already low signal-to-background ratio (SBR) expected from single-molecule experiments. The data is further complicated by instances of photoblinking and out-of-plane rotation, when only background signal is present. A convenient method for excluding background signal was developed via a Monte Carlo simulation for discriminating points in the trajectory composed only of background signal that is robust to SBR. These simulations also showed an SBR dependance for the accuracy of the values extracted from rotational autocorrelation functions. This method was used experimentally to directly demonstrate ergodicity in supercooled liquids. The next chapter focuses on conjugated polymers, which display a complex relationship between chain conformation and photophysics. This conformational complexity exists even at the single-chain level, obscuring the understanding of how excitons behave in the bulk, such as in a device. Understanding this relationship however, is difficult as conformation and photophysics are hard to access in operando not only because a single conjugated polymer chain is smaller than the diffraction limit, but also because a fluorescing conjugated polymer emits light from many locations. The overall conformation is typically assessed using polarization modulation measurements, which only provide mesoscale information about a chain's conformation. A super-resolution method was developed to map the distribution of emitters and trace out single-chain conformation. The extracted radii of gyration for these single-chains matched well with polymer theory. Chapter three describes the development of experimental and image analytical tools to bridge single-chain studies of photophysics in conjugated polymer, to the photophysics that might be observed in a conjugated polymer device where chain-chain contacts and high levels of local ordering may be present. It has been shown previously that solvent vapor annealing can be used to prepare conjugated polymer aggregates of various levels of internal ordering. However, solvent vapor annealing is a process that is difficult to control and difficult to evaluate. Therefore, a first-of-its-kind apparatus was constructed that can generate and deliver solvent vapor in a controlled fashion to swell polymer films while monitoring both film dynamics by fluorescence imaging as well as swelling extent via a quartz crystal microbalance. Fluorescent images acquired during aggregation showed heterogeneous diffusion among aggregates, possibly indicating heterogeneous sizing. Fluorescent characterization of presumably differently sized aggregates indicates a possible emergent quenching phenomenon in a bulk conjugated polymer material. The final chapter of this dissertation describes an effort to characterize dynamics in collagen gels. Collagen gels form through a complex sol-gel process precipitated by nucleation and growth fibrillogenesis. To probe the long length scales of interest here, single-molecule methods were not practical. Instead, an optical flow algorithm was explored to detect key physical events in the evolving system. One effort aims to characterize the dynamics of the early gelation process. In particular, the optical flow measurements provide a high-resolution measure for the moment at which the sol-gel transition occurs. Another application involves the use of optical flow to observe distortions in the collagen network while it is undergoing strain stiffening. Preliminary studies show that at critical strain, local breaks in the gel propagate throughout the gel until the gel completely loses its ability to sustain stress. In general, the ability to quantify details about complex materials from imaging data can be quite a complex endeavor itself, requiring awareness of the physical phenomena of interest, how said phenomena manifests optically, and the use and development of appropriate algorithms. As described in this dissertation, the proper use and/or development of the proper image analysis methods allow for extraction of key information from dense data.

In the past several decades, low-dimensional materials (0D materials, 1D materials and 2D materials) have attracted much interest from both the experimental and theoretical points of view. Because of the quantum confinement effect, low-dimensional materials have exhibited a kaleidoscope of fascinating phenomena and unusual physical and chemical properties, shedding light on many novel applications. Despite the enormous success has been achieved in the research of low-dimensional materials, there are three fundamental challenges of research in low-dimensional materials: 1) Develop new computational tools to accurately describe the properties of low-dimensional materials with low computational cost. 2) Predict and synthesize new low-dimensional materials with novel properties. 3) Reveal new phenomenon induced by the interaction between low-dimensional materials and the surrounding environment. In this thesis, atomistic modelling tools have been applied to address these challenges. We first developed ReaxFF parameters for phosphorus and hydrogen to give an accurate description of the chemical and mechanical properties of pristine and defected black phosphorene. ReaxFF for P/H is transferable to a wide range of phosphorus and hydrogen containing systems including bulk black phosphorus, blue phosphorene, edge-hydrogenated phosphorene, phosphorus clusters and phosphorus hydride molecules. The potential parameters were obtained by conducting global optimization with respect to a set of reference data generated by extensive ab initio calculations. We extended ReaxFF by adding a 60° correction term which significantly improved the description of phosphorus clusters. Emphasis was placed on the mechanical response of black phosphorene with different types of defects. Compared to the nonreactive SW potential of phosphorene, ReaxFF for P/H systems provides a significant improvement in describing the mechanical properties of the pristine and defected black phosphorene, as well as the thermal stability of phosphorene nanotubes. A counterintuitive phenomenon was observed that single vacancies weaken the black phosphorene more than double vacancies with higher formation energy. Our results also showed that the mechanical response of black phosphorene is more sensitive to defects in the zigzag direction than that in the armchair direction. Since ReaxFF allows straightforward extensions to the heterogeneous systems, such as oxides, nitrides, the proposed ReaxFF parameters for P/H systems also underpinned the reactive force field description of heterogeneous P systems, including P-containing 2D van der Waals heterostructures, oxides, etc. Based on the evolutionary algorithm driven structural search, we proposed a new stable trisulfur dinitride (S3N2) 2D crystal that is a covalent network composed solely of S-N σ bonds. S3N2 crystal is dynamically, thermally and chemically stable as confirmed by the computed phonon spectrum and ab initio molecular dynamics simulations. GW calculations showed that the 2D S3N2 crystal is a wide, direct band-gap (3.92 eV) semiconductor with a small hole effective mass. The anisotropic optical response of 2D S3N2 crystal was revealed by GW-BSE calculations. Our result not only marked the prediction of the first 2D crystal composed of nitrogen and sulfur, but also underpinned potential innovations in 2D electronics, optoelectronics, etc. Inspired by the discovery of S3N2 2D crystal, we proposed a new 2D crystal, diphosphorus trisulfide (P2S3), based on the extensive evolutionary algorithm driven structural search. The 2D P2S3 crystal was confirmed to be dynamically, thermally and chemically stable by the computed phonon spectrum and ab initio molecular dynamics simulations. This 2D crystalline phase of P2S3 corresponds to the global minimum in the Born-Oppenheimer surface of the phosphorus sulfide monolayers with 2:3 stoichiometry. It is a wide band gap (4.55 eV) semiconductor with P-S σ bonds. The electronic properties of P2S3 structure can be tuned by stacking into multilayer P2S3 structures, forming P2S3 nanoribbons or rolling into P2S3 nanotubes, expanding its potential applications for the emerging field of 2D electronics. Then we showed that the hydrolysis reaction is strongly affected by relative humidity. The hydrolysis of CO32- with n = 1-8 water molecules was investigated by ab initio method. For n = 1-5 water molecules, all the reactants follow a stepwise pathway to the transition state. For n = 6-8 water molecules, all the reactants undergo a direct proton transfer to the transition state with overall lower activation free energy. The activation free energy of the reaction is dramatically reduced from 10.4 to 2.4 kcal/mol as the number of water molecules increases from 1 to 6. Meanwhile, the degree of the hydrolysis of CO32- is significantly increased compared to the bulk water solution scenario. The incomplete hydration shells facilitate the hydrolysis of CO32- with few water molecules to be not only thermodynamically favorable but also kinetically favorable. We showed that the chemical kinetics is not likely to constrain the speed of CO2 air capture driven by the humidity-swing. Instead, the pore-diffusion of ions is expected to be the time-limiting step in the humidity driven CO2 air capture. The effect of humidity on the speed of CO2 air capture was studied by conducting CO2 absorption experiment using IER with a high ratio of CO32- to H2O molecules. Our result is able to provide valuable insights to designing efficient CO2 air-capture sorbents. Lastly, the self-assembly mechanism of one-end-open carbon nanotubes (CNTs) suspended in an aqueous solution was studied by molecular dynamics simulations. It was shown that two one-end-open CNTs with different diameters can coaxially self-assemble into a nanocapsule. The nanocapsules formed were stable in aqueous solution under ambient conditions, and the pressure inside the nanocapsule was much higher than the ambient pressure due to the van der Waals interactions between two parts of the nanocapsule. The effects of the normalized radius difference, normalized inter-tube distance and aspect ratio of the CNT pairs were systematically explored. The electric field response of nanocapsules was studied with ab initio molecular dynamics simulations, which showed that nanocapsules can be opened by applying an external electric field, due to the polarization of carbon atoms. This discovery not only shed light on a simple yet robust nanocapsule self-assembly mechanism, but also underpinned potential innovations in drug delivery, nano-reactors, etc.

No description available.

Thesis (Ph. D.)--University of Pennsylvania, 1961. / Title form home page.(viewed Nov. 20, 2003). Includes bibliographical reference and indexes.

Thesis--Ph. D., University of Hong Kong. / Mimeographed.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

No description available.