Extension of the MIRS computer package for the modeling of molecular spectra : from effective to full ab initio ro-vibrational hamiltonians in irreducible tensor form

The MIRS software for the modeling of ro-vibrational spectra of polyatomic molecules was considerably extended and improved. The original version (Nikitin, et al. JQSRT, 2003, pp. 239--249) was especially designed for separate or simultaneous treatments of complex band systems of polyatomic molecules. It was set up in the frame of effective polyad models by using algorithms based on advanced group theory algebra to take full account of symmetry properties. It has been successfully used for predictions and data fitting (positions and intensities) of numerous spectra of symmetric and spherical top molecules within the vibration extrapolation scheme. The new version offers more advanced possibilities for spectra calculations and modeling by getting rid of several previous limitations particularly for the size of polyads and the number of tensors involved. It allows dealing with overlapping polyads and includes more efficient and faster algorithms for the calculation of coefficients related to molecular symmetry properties (6C, 9C and 12C symbols for C_{3v}, T_{d}, and O_{h} point groups) and for better convergence of least-square-fit iterations as well. The new version is not limited to polyad effective models. It also allows direct predictions using full ab initio ro-vibrational normal mode hamiltonians converted into the irreducible tensor form. Illustrative examples on CH_{3} D, CH_{4}, CH_{3} Cl, CH_{3} F and PH_{3} are reported reflecting the present status of data available. It is written in C++ for standard PC computer operating under Windows. The full package including on-line documentation and recent data are freely available at [http://www.iao.ru/mirs/mirs.htm] or [http://xeon.univ-reims.fr/Mirs/||http://xeon.univ-reims.fr/Mirs/] or [http://icb.u-bourgogne.fr/OMR/SMA/SHTDS/MIRS.html].Comment: Journal of Quantitative Spectroscopy and Radiative Transfer (2012) xxx-xx

Co-ordination chemistry of novel tripodal ligands designed to host anions

The development of novel ligands for the complexation of transition metal ions in inorganic chemistry is a rapidly developing field of study. The broad objective of this work is to design novel tripodal transition metal based receptors of (TPA) frame work which can act as hosts for small molecules (guests) e.g. fluoride and succinate. In addition, investigation into the co-ordination chemistry of those receptors with first row transition metals were explored using variety of characterizing techniques such as: Infrared Spectroscopy (IR), Electronic transitions (UV-Vis), Mass Spectrometry (MS), Nuclear Magnetic Resonance (NMR), Cyclic voltammetry (CV) and Single Crystal Diffractometer (X-Ray). Mono, Bis and Tris thiourea tripodal ligands have been synthesised and their co ordination chemistry has been investigated (chapter 2, 3 and 4) as well as the binding studies of the bisthiourea (chapter 3) to bind: fluoride and succinate using *H NMR titration technique. The co-ordination chemistry of TPPA with some first row transition metals has been studied and it was expected to show high affinity for seven coordination sphere and indeed it has shown strong preference for mono capped octahedral geometry (chapter 5).EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Co-ordination chemistry of novel tripodal ligands designed to host anions

The development of novel ligands for the complexation of transition metal ions in inorganic chemistry is a rapidly developing field of study. The broad objective of this work is to design novel tripodal transition metal based receptors of (TPA) frame work which can act as hosts for small molecules (guests) e.g. fluoride and succinate. In addition, investigation into the co-ordination chemistry of those receptors with first row transition metals were explored using variety of characterizing techniques such as: Infrared Spectroscopy (IR), Electronic transitions (UV-Vis), Mass Spectrometry (MS), Nuclear Magnetic Resonance (NMR), Cyclic voltammetry (CV) and Single Crystal Diffractometer (X-Ray). Mono, Bis and Tris thiourea tripodal ligands have been synthesised and their co ordination chemistry has been investigated (chapter 2, 3 and 4) as well as the binding studies of the bisthiourea (chapter 3) to bind: fluoride and succinate using *H NMR titration technique. The co-ordination chemistry of TPPA with some first row transition metals has been studied and it was expected to show high affinity for seven coordination sphere and indeed it has shown strong preference for mono capped octahedral geometry (chapter 5)

Towards a circular economy: fabrication and characterization of biodegradable plates from sugarcane waste

Bagasse pulp is a promising material to produce biodegradable plates. Bagasse is the fibrous residue that remains after sugarcane stalks are crushed to extract their juice. It is a renewable resource and is widely available in many countries, making it an attractive alternative to traditional plastic plates. Recent research has shown that biodegradable plates made from Bagasse pulp have several advantages over traditional plastic plates. For example, they are more environmentally friendly because they are made from renewable resources and can be composted after use. Additionally, they are safer for human health because they do not contain harmful chemicals that can leach into food. The production process for Bagasse pulp plates is also relatively simple and cost-effective. Bagasse is first collected and then processed to remove impurities and extract the pulp. The pulp is then molded into the desired shape and dried to form a sturdy plate. Overall, biodegradable plates made from Bagasse pulp are a promising alternative to traditional plastic plates. They are environmentally friendly, safe for human health, and cost-effective to produce. As such, they have the potential to play an important role in reducing plastic waste and promoting sustainable practices. Over the years, the world was not paying strict attention to the impact of rapid growth in plastic use. As a result, uncontrollable volumes of plastic garbage have been released into the environment. Half of all plastic garbage generated worldwide is made up of packaging materials. The purpose of this article is to offer an alternative by creating bioplastic goods that can be produced in various shapes and sizes across various sectors, including food packaging, single-use tableware, and crafts. Products made from bagasse help address the issue of plastic pollution. To find the optimum option for creating bagasse-based biodegradable dinnerware in Egypt and throughout the world, researchers tested various scenarios. The findings show that bagasse pulp may replace plastics in biodegradable packaging. As a result of this value-added utilization of natural fibers, less waste and less of it ends up in landfills. The practical significance of this study is to help advance low-carbon economic solutions and to produce secure bioplastic materials that can replace Styrofoam in tableware and food packaging production

Nanoestruturas baseadas em ZnO e GaN para aplicações optoeletrónicas : síntese e caracterização

Wide bandgap semiconductors, such as GaN and ZnO, are materials with a wide range of applications in several important technological areas including lighting, transparent electronics, sensors, catalysis or photovoltaics. This thesis focuses on the study of GaN and ZnO, including related compounds. In the first case, the emphasis is given to the incorporation of rare-earth (RE) ions (4fn) into the nitride hosts envisaging to contribute for the development of “all-nitride” solid state lighting devices. GaN and related III-nitrides ternary alloys appear as excellent hosts for the incorporation of these ions. The use of RE ions is motivated by the electromagnetic widespread spectral range (from the ultraviolet to the near infrared) covered by the intraionic radiative relaxation of the trivalent charged ions. Ion implantation appears as an alternative approach to doping since it allows the introduction of impurities in a controlled way and without solubility limits. GaN samples with different dimensionalities were analysed and their influence in the luminescence properties of the RE3+ was investigated. Photoluminescence (PL) measurements revealed that after thermal annealing a successful optical activation of the RE3+ was achieved for the samples implanted with the different RE3+. A detailed spectroscopic analysis of RE3+ luminescent tarnsitions is presented by using temperature dependent steady-state PL, room temperature PL excitation and time resolved PL. This thesis also aims to the growth and characterization of ZnO micro and nanostructures, through a new growth technique designated by laser assisted flow deposition (LAFD). LAFD is a very high yield method based on a vapour-solid mechanism that enables the growth of ZnO crystals in a very short timescale. LAFD was used in the growth of wurtzite micro/nanocrystalline ZnO with different morphologies (nanoparticles, tetrapods and microrods) as revealed by the extensive morphological characterization. Moreover, structural analysis evidenced the high crystalline quality of the produced crystals. The optical properties of the as-grown ZnO crystals were fully investigated by luminescence techniques, which revealed a high optical quality of the LAFD produced ZnO. In addition to the unintentionally doped micro/nanocrystals, ZnO/Ag and ZnO/carbon nanotubes (CNT) composite structures were also synthesized by LAFD. Silver-related spherical particles were found to be inhomogeneously distributed at the microrods surface, accumulating at the rods tips and promoting the ZnO nanorods re-nucleation. For the case of the ZnO/CNT composites two main approaches were adopted: i) a direct deposition of ZnO particles on the surface of vertically aligned multi-walled carbon nanotubes (VACNTs) forests without employing any additional catalyst and ii) ZnO/CNT buckypaper nanocomposites. It was found that the use of the LAFD technique carried out in framework of the first approach preserves the CNTs structure, their alignment, and avoids the collapse of the VACNTs array, which is a major advantage of this method. Additionally, taking into account that a crucial step in designing modern optoelectronic devices is to accomplish bandgap engineering, the optical properties of CdxZn1-xO alloy were also evaluated. A tuning of the ZnO bandgap towards the visible spectral region was accomplished by alloying this semiconductor with CdO. Finally, the potential application of the LAFD produced ZnO structures in the photocatalysis and photovoltaic fields was tested.Os semicondutores de elevado hiato energético, como é o caso do GaN e do ZnO, são materiais com aplicações em diversas áreas tecnológicas, que incluem, por exemplo, iluminação, eletrónica transparente, sensores, catalisadores ou fotovoltaicos. Esta tese é dedicada ao estudo de materiais baseados em GaN e ZnO, sendo dada ênfase à incorporação de iões terras-raras (RE) nas matrizes de nitretos, com a finalidade de contribuir para o desenvolvimento de dispositivos de iluminação de estado sólido. O uso dos iões RE é motivado pelas suas emissões intraiónicas abrangendo uma ampla gama espectral (do ultravioleta ao infravermelho próximo), quando estão no seu estado de carga trivalente. A implantação iónica surge como uma alternativa para a dopagem destes materiais, uma vez que permite a introdução de dopantes de uma forma controlada e independente dos limites de solubilidade dos iões nas matrizes. Amostras de GaN com diferentes dimensionalidades foram analisadas e a sua influência nas propriedades luminescentes dos RE3+ foi investigada. Medidas de fotoluminescência (PL) revelaram que, depois de um tratamento térmico, a ativação ótica dos iões foi bem-sucedida para as amostras implantadas com os diferentes iões. Uma análise espectroscópica detalhada das transições luminescentes dos RE3+ foi realizada usando técnicas como a PL em estado estacionário e transiente e excitação da fotoluminescência. Outro objetivo desta tese foi o crescimento e caracterização de micro e nanoestruturas de ZnO, recorrendo a uma nova técnica de crescimento designada por deposição de fluxo assistida por laser (LAFD). Este é um método com elevado rendimento, baseado num mecanismo sólido-vapor, que permite o crescimento de ZnO com diferentes morfologias (nanopartíclulas, tetrapodes e microfios). A sua análise estrutural pôs em evidência a excelente qualidade cristalina do ZnO produzido por esta técnica. As propriedades óticas foram também investigadas através de fotoluminescência, revelando a sua elevada qualidade ótica. Para além dos cristais não dopados intencionalmente, foram ainda preparados compósitos com prata e nanotubos de carbono (CNTs). No primeiro caso, foram observadas partículas esféricas de prata distribuídas de uma forma não uniforme na superfície dos microfios, mostrando uma tendência para se acumularem no topo destes e promovendo a sua renucleação. No caso dos compósitos ZnO/CNTs, foram usadas duas abordagens: i) deposição de partículas de ZnO diretamente no topo dos CNTs alinhados verticalmente, sem a utilização de nenhum catalisador adicional, e ii) produção de ZnO/CNTs buckypapers. No primeiro caso, a técnica de LAFD provou manter o alinhamento dos CNTs, evitando o seu colapso, sendo esta uma vantagem do método usado. Adicionalmente, tendo em consideração a importância do controlo do hiato energético dos materiais a ser aplicados em dispositivos optoelectrónicos, foram também estudadas as propriedades óticas da liga CdxZn1-xO. Devido ao aumento da fração molar de CdO na liga ternária observou-se um desvio do hiato do ZnO para a região visível do espetro eletromagnético. Finalmente, as estruturas de ZnO crescidas por LAFD foram testadas em dispositivos fotovoltaicos e em estudos de fotocatálisePrograma Doutoral em Nanociências e Nanotecnologi