Nanostructured catalysts for the development of the hydrogen economy

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2015-2016La catalyse joue un rôle essentiel dans de nombreuses applications industrielles telles que les industries pétrochimique et biochimique, ainsi que dans la production de polymères et pour la protection de l'environnement. La conception et la fabrication de catalyseurs efficaces et rentables est une étape importante pour résoudre un certain nombre de problèmes des nouvelles technologies de conversion chimique et de stockage de l'énergie. L'objectif de cette thèse est le développement de voies de synthèse efficaces et simples pour fabriquer des catalyseurs performants à base de métaux non nobles et d'examiner les aspects fondamentaux concernant la relation entre structure/composition et performance catalytique, notamment dans des processus liés à la production et au stockage de l'hydrogène. Dans un premier temps, une série d'oxydes métalliques mixtes (Cu/CeO2, CuFe/CeO2, CuCo/CeO2, CuFe2O4, NiFe2O4) nanostructurés et poreux ont été synthétisés grâce à une méthode améliorée de nanocasting. Les matériaux Cu/CeO2 obtenus, dont la composition et la structure poreuse peuvent être contrôlées, ont ensuite été testés pour l’oxydation préférentielle du CO dans un flux d'hydrogène dans le but d’obtenir un combustible hydrogène de haute pureté. Les catalyseurs synthétisés présentent une activité et une sélectivité élevées lors de l'oxydation sélective du CO en CO2. Concernant la question du stockage d'hydrogène, une voie de synthèse a été trouvée pour le composét mixte CuO-NiO, démontrant une excellente performance catalytique comparable aux catalyseurs à base de métaux nobles pour la production d'hydrogène à partir de l'ammoniaborane (aussi appelé borazane). L'activité catalytique du catalyseur étudié dans cette réaction est fortement influencée par la nature des précurseurs métalliques, la composition et la température de traitement thermique utilisées pour la préparation du catalyseur. Enfin, des catalyseurs de Cu-Ni supportés sur silice colloïdale ou sur des particules de carbone, ayant une composition et une taille variable, ont été synthétisés par un simple procédé d'imprégnation. Les catalyseurs supportés sur carbone sont stables et très actifs à la fois dans l'hydrolyse du borazane et la décomposition de l'hydrazine aqueuse pour la production d'hydrogène. Il a été démontré qu'un catalyseur optimal peut être obtenu par le contrôle de l'effet bi-métallique, l'interaction métal-support, et la taille des particules de métal.Catalysis plays an essential role in many industrial applications such as petrochemical and biochemical industries, as well as in the production of polymers and in environmental protection. Design and fabrication of efficient catalysts in a cost-effective way is an important milestone to address a number of unresolved issues in the new generation of chemical and energy conversion technologies. The objective of the studies in this thesis is the development of facile synthetic routes to prepare efficient catalysts based on non-noble metals, and elucidate fundamental aspects regarding the relationship between structure/composition and catalytic performance, in particular in the case of processes related to production and storage of hydrogen fuel. At first, a series of nanostructured porous mixed metal oxides (Cu/CeO2, CuFe/CeO2, CuCo/CeO2, CuFe2O4, NiFe2O4) have been synthesized via an improved nanocasting method. The porous structure of the nanocast products was tailored by tuning the mesostructure of the mesoporous silica phases used as templates. The obtained Cu/CeO2 materials with controlled composition and porous structure were then tested in preferential oxidation of CO in a hydrogen stream to achieve high purity hydrogen fuel. The synthesized catalysts exhibit high activity and selectivity in selective oxidation of CO to CO2. Regarding hydrogen storage, we reported a cost-effective synthetic way towards bi-component CuO-NiO catalyst showing excellent catalytic performance, which is comparable to noble metal catalysts, in the hydrogen generation from ammonia-borane. Moreover, we demonstrate that the interaction between Cu and Ni species is essential in accelerating hydrogen evolution of ammonia borane. The catalytic activity of the obtained catalyst investigated in this reaction is strongly influenced by the nature of the metal precursors, the composition and the thermal treatment temperature employed for the catalyst preparation. Finally, silica- and carbon-supported Cu-Ni nanocatalysts, with tunable composition and metal particle size, were synthesized by simple incipient wetness method. The carbon supported catalysts are stable, highly active and selective in both ammonia-borane hydrolysis and the decomposition of hydrous hydrazine for hydrogen evolution. We showed that optimal catalysts can be achieved through manipulation of bimetallic effect, metal-support interaction, and adequate metal particle size

Public perceptions on LGBT issues in modern Vietnam

This paper examines the history, culture, and policies in Vietnam as fundamentals for an analysis on one of the most emerging topics in the modern Vietnamese society: the Lesbian, Gay, Bisexual and Transgender (LGBT) community. I have collected data from opinions and comments on different means of social media as representation of public opinion toward LGBT, which seem to most expressed in three aspects: lack of knowledge, stereotype, and prejudice; the categorization and labeling as Third World; and advocacy for LGBT equality. With the quite strict tradition and high stress on family ties, the challenge for the members of this community to advocate for their rights is quite high. Even though it is not easy to transform people\u27s minds and change moral values, recent changes on positive side in this discourse allow us to hope for the best

In My Own Little Box

University of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/133989/1/FINALTHESISPAPER.pd

Utilization Of Antibody-Conjugated Gold Nanoparticles, Dynamic Light Scattering And Sers In Influenza Virus Detection

Influenza A H3N2, H1N1, and influenza B viruses primarily cause winter illness in humans, leading to significant morbidity and mortality in the population of the very young, the elderly, and people with chronic disease. In addition to the regular seasonal epidemics of influenza, influenza pandemics associated with the emergence of new influenza A strains are threatening due to high levels of mortality, social disruption, and economic losses. These novel strains are not affected by the human immunity developed to older strains of influenza, therefore can spread readily and infect a vast number of people. The most recent flu pandemic outbreak was in 2009, in which pandemic swine influenza A H1N1 was transmitted. Thus, an initiative to prevent human infections with new strains of influenza A virus with pandemic potential has been supported by the government and become a focus of many laboratories. The first step in any preventative measures is early detection. Therefore, it is essential to develop a detection platform that is capable of simultaneous multiplexing and exploitable for point-of-care (POC) analysis. Virus culture, nucleic acid testing, and immunoassays are primary detection approaches to confirm acute human influenza virus infection. Nucleic acid testing has great sensitivity and specificity to subtype influenza strains, and high capacity for multiplexed detection. However, it is time and labor intensive, and expensive. Virus isolation is slow, costly, and not feasible for routine diagnostic testing. Immunoassays, in contrast, are known for availability, low-cost, accuracy, and versatility, and therefore have become a centerpiece in diagnostics. Among a number of analytical detection techniques developed for immunoassays, SERS (surface enhanced Raman spectroscopy) biosensing utilizing antibody-conjugated gold nanoparticles (Ab-AuNPs) is a promising virus detection technique providing high sensitivity (down to single molecule detection) and multiplexing (distinction of different strains of a single virus type). Herein a simple, rapid, sensitive AuNP-based immunoassay was developed to quantitatively detect influenza A virus, utilizing dynamic light scattering (DLS) and surface enhanced Raman spectroscopy (SERS). The assay platform was established based on the principle of homogeneous format. Antigen-specific antibodies (Abs) were attached to the surface of gold nanoparticles (AuNPs), rendering the biospecificity for the detection. AuNPs serve as a signal generator or label. A biological sample containing targeted analytes was mixed with Ab-conjugated AuNPs (or AuNP probes); aggregation of nanoparticle was induced in the presence of the analyte(s). The antibody molecules on the particle surface recognized and bound to the analyte via the key-lock like mechanism, cross-linking AuNPs together to form aggregates. The quantification of antigen became the matter of detecting aggregation. The reaction happened in a timely fashion, oftentimes in a few minutes owing to the fast solution phase kinetics. No washing was required; therefore, time and labor were remarkably saved relative to heterogeneous assays. When utilizing this platform, alteration of different antigen-specific antibodies can perform detection of different antigen analytes individually (singleplexing). The combination of multiple types of AuNP probes in one assay allows simultaneously multiplexed detection. In order to ensure the robustness of the assay, optimization for each stage of the platform design was thoroughly studied. The optimal conditions for maintaining the stability of the gold nanoparticles coated with monoclonal antibodies (mAbs) were investigated by varying pH, conjugation chemistry, mAbs concentrations, and blocking reagents. DLS is exploited to monitor the conjugation of the antibodies on AuNPs and verify the aggregate formation of the antigen-induced AuNP probes based on hydrodynamic diameter measurements. The DLS-based immunoassay has been demonstrated as an excellent rapid screening method to evaluate the specificity and affinity of antibody-antigen binding. Comparing to a conventional method for antibody screening (i.e. ELISA), a DLS assay requires only 30 min while it takes 24 h to perform an ELISA. To address the urgent need for multiplexed detection, we have slightly modified the DLS assay to develop a SERS-based homogeneous immunoassay. Namely, Raman reporters and antibody were co-immobilized on the AuNPs to construct ERLs (extrinsic Raman labels). Raman reporters provide distinctive and amplified signal for detection. In order to detect multiple analytes, multiple types of ERLs were separately prepared; each type was a unique combination of one antigen-specific antibody and one Raman reporter. The ERLs were then mixed together and added to the sample. Aggregation was induced upon the introduction of the antigen to the suspension of ERLs on the order of minutes. ERLs of the same type were cross-linked via the antigen specific to the antibody conjugated to the very type of ERLs. The nonspecific ERLs remained unreacted if their antigens were not present in the sample. Once aggregation occurred, the SERS signals provided by the Raman reporters on the reacted ERLs were turned on. AuNPs in the aggregating state were in proximity to each other and created small gaps between them. Raman reporters once trapped in those gaps generated signal for detection. In theory, SERS analysis can be performed in solution but in reality poor plasmonic coupling between antibody-modified AuNP limits the SERS enhancement. However, dehydration of the aggregates reduces interparticle spacing to yield higher SERS signals. Therefore, separation of aggregated ERLs on a well-defined nanoporous membrane was applied to intensify the signal. The conditions for optimal filtration process have been investigated. Preliminary data have shown progress made toward a fully developed configuration for a portable multiplexed, sensitive, and rapid POC detection platform

Ramsey numbers for set-colorings

For s, t, n ∈ N with s ≥ t, an (s, t)-coloring of K$_n$ is an edge coloring of Kn in which each edge is assigned a set of t colors from {1, . . . , s}. For k ∈ N, a monochromatic K$_k$ is a set of k vertices S such that for some color i ∈ [s], i ∈ c(uv) for all distinct u, v ∈ S. As in the case of the classical Ramsey number, we are interested in the least positive integer n = R$_{s,t}$(k) such that for any (s, t)-coloring of K$_n$, there exists a monochromatic K$_k$. We estimate upper and lower bounds for general cases and calculate close bounds for some small cases of R$_{s,t}$(k)

Policy of mobilizing financial resources for developing new countryside in Vietnam

Financial resources and the institutional framework, as well as policies for mobilizing financial resources, are important issues that need to be addressed in the construction of new countryside in Vietnam. Financial resources for the new countryside mainly come from the state budget, credit sources, investments from enterprises, contributions, and support from organizations, individuals, and the local community. In recent years, the state has paid attention to financial investment and issued policies to mobilize financial resources for the new countryside. Through these policies, Vietnam's rural areas have achieved important results, with rural areas being renewed, the economy being developed, and the living standards of the people being improved. However, statistical analysis and research results show that, alongside the achievements, financial resources for new countryside have not yet satisfied the needs, and the policies for mobilizing resources are sluggish to innovate and have neither fully exploited the potential of rural areas nor effectively mobilized resources from the state and society. The state budget resources for investing in the new countryside are limited, and the investment resources from enterprises have yielded low results. Contributions from the people and the local community are voluntary and have not become the main resources mobilized for the new countryside. Based on the research results, the author proposes some solutions to improve the policies for mobilizing financial resources for the new countryside in Vietnam

Capital Solutions to Promote Fleet Investment in Shipping in Countries Such as Vietnam

Purpose: Research on capital solutions to develop the fleet in Vietnam's shipping enterprises from 2022 to 2030.   Originality/value: The research sample is the fleet of boats that Vietnamese shipping enterprises registered at the Vietnam Maritime Administration from 2011 – 2018.    Design/methodology/approach: Using Qualitative Research (Statistical Analysis Methods; System analysis; Expert interview methods) and quantitative research methods (Comparative methods; Methods of analysis of indicators).   Findings: Based on the research, the author offers several discussions and recommendations on capital solutions to promote investment and development of the fleet in Vietnam's shipping