Neste estudo apresenta-se a síntese de duas amostras de nanopartículas de ferrita de níquel, denominadas C-NiFe2O4 e NiFe2O4, através de um método simples, de baixo custo e ambientalmente amigável. Estudos morfológicos, estruturais, eletrônicos, ópticos e magnéticos foram realizados com o intuito de caracterizar as propriedades desses materiais para que possibilitassem, além de maior grau de conhecimento, sua aplicação como sensores colorimétricos para detecção de ácido ascórbico e peróxido de hidrogênio. Mediante a análise térmica dos precursores, foi possível determinar os intervalos de temperatura de decomposição, assim como a temperatura ótima de formação das nanopartículas. A amostra NiFe2O4 é ferromagnética e corresponde a uma fase cúbica de espinélio inverso. Os dados de difração de raios X, espectroscopia Mössbauer e o modelo iônico sugerem a presença de um certo grau de substituição, possuindo em sua estrutura um cátion divalente como agente dopante. As nanopartículas de C-NiFe2O4 foram utilizadas como catalisador na oxidação do 3,3',5,5'-tetrametilbenzidina (TMB) em meio ácido para formar uma solução azul sem adição de outro reagente. Como resultado foi utilizado como sensor colorimétrico para detecção de ácido ascórbico, visto que este reduz o complexo de transferência de carga, TMBOX, novamente para TMB. A calibração analítica apresentou uma faixa linear entre 1-20 μM para a concentração de ácido ascórbico, com limite de detecção (3/m) de 0,93 μM. A determinação em suplementos de vitamina C através do método de adição de padrão mostrou a eficiência do sensor para detectar ácido ascórbico em amostras reais. Já a amostra de NiFe2O4 demonstrou atividade catalítica semelhante as peroxidases naturais, oxidando o TMB na presença de H2O2 para formar TMBOX, que dá coloração azul a solução. Dessa forma, NiFe2O4 foi utilizado em um sensor colorimétrico para detecção de H2O2 e a calibração analítica revelou duas faixas lineares, uma entre 2,28 - 28,60 μM e a outra entre 28,60 μM - 114,20 μM. O limite de detecção (3/m) foi de 1,94 μM. Ambos os métodos apresentaram boa repetibilidade, com coeficiente de variação de 3,5% e 4% respectivamente. / This study presents the synthesis of two samples of nickel ferrite nanoparticles, termed C-NiFe2O4 and NiFe2O4, through a simple, low cost and environmentally friendly method. Morphological, structural, electronic, optical and magnetic studies were carried out with the aim of characterizing the properties of these materials, which allowed the application of colorimetric sensors for the detection of ascorbic acid and hydrogen peroxide. Through the thermal analysis of the precursors, it was possible to determine the decomposition temperature ranges, as well as the optimum temperature of formation of the nanoparticles. The sample NiFe2O4 is ferromagnetic and corresponds to a cubic phase of inverse spinel. The X-ray diffraction data, Mössbauer spectroscopy and the ionic model suggest the presence of a certain degree of substitution, having in its structure a divalent cation as a doping agent. The C-NiFe2O4 nanoparticles were used as catalysts in the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in acidic medium to form a blue solution without addition of another reagent. As a result, it was used as a colorimetric sensor for the detection of ascorbic acid, as it reduces the charge transfer complex, TMBOX, again to TMB. The analytical calibration showed a linear range between 1-20 μM for the concentration of ascorbic acid, with a detection limit (3 /m) of 0.93 μM. The determination of vitamin C supplements using the standard addition method showed the efficiency of the sensor to detect ascorbic acid in actual samples. Already NiFe2O4 sample demonstrated catalytic activity similar to natural peroxidases, oxidizing the TMB in the presence of H2O2 to form TMBOX, which gives blue coloration to the solution. Thus, NiFe2O4 was used in a colorimetric sensor to detect H2O2, and the analytical calibration revealed two linear ranges, one between 2.28 - 28.60 μM and the other between 28.60 μM - 114.20 μM. The detection limit (3 /m) was 1.94 μM. Both methods presented good repeatability, with a coefficient of variation of 3.5% and 4% respectively.

Objectives: To compare two in-office bleaching methods with respect to tooth color change and level of hydrogen peroxide penetration into the pulp cavity, and evaluate relationships between penetration level and color change. Methods: 80 extracted canines were sectioned above the CEJ and pulp tissue removed. Tooth thickness was measured from the outer labial surface to the outer boundary of the pulp cavity at the cross-sectioned root 3mm below the CEJ using a digital caliper. Baseline color was measured spectrophotometrically; acetate buffer was added into the cavity. Teeth were mounted and exposed to two different bleaching regimens (conventional versus sealed bleaching technique). After exposure to 38% hydrogen peroxide gel for one hour, buffer was removed from the cavity and placed into a volumetric flask. Hydrogen peroxide amount was estimated spectrophotometrically using leucocrystal violet and horseradish peroxidase. Specimen color was re-measured 2 hours post-bleaching. Color change was measured per Commission Internationale de l'Eclairage methodology. Linear regression was used to evaluate factors affecting color change, including bleaching technique. Results: The conventional and sealed bleaching groups showed no difference at baseline with respect to tooth thickness or any of the L*a*b color measures (p>0.51); however there was significantly greater hydrogen peroxide penetration in the conventional bleaching group (p<0.0001). Linear modeling of the change in lightness (ΔL) showed that the increase in lightness tended to be greater for teeth with lower initial L* values (r=-0.32, p=0.004). After adjustment for initial L*, there was no evidence that ΔL differed with hydrogen penetration levels (p=0.53) or bleaching technique (mean group difference in ΔL= 0.36; p=0.27). Conclusion: Both groups showed significant increases in lightness exceeding 2 units and therefore discernible to the naked eye (p<0.0001); however, mean ΔL did not differ significantly with bleaching method or hydrogen peroxide penetration.

M. Tech (Department of Chemistry, Faculty of Applied and Computer Sciences) Vaal University of Technology. / Agricultural waste such as Macadamia nutshells are currently receiving more attention for removal of hexavalent chromium (Cr(VI)). However, they have low adsorption capabilities when used in their raw form. In this study, the efficiency of using Macadamia nutshell powder modified with different concentrations of hydrogen peroxide, grafted with 1,5’-diphenylcarbizide (DPC) for the removal of hexavalent chromium from aqueous solution was explored. The effects of various parameters controlling adsorption of Cr(VI) onto Macadamia adsorbents such as initial concentration, contact time, adsorbent concentration and pH were investigated. The optimal operating parameters for Macadamia nutshells treated with hydrogen peroxide (MHP) adsorbents were determined to be 75 mg/L, 3 h, 0.1 g and pH 1. The optimal operating parameters for Macadamia nutshells treated with hydrogen peroxide and grafted with 1,5’-diphenylcarbizide (MHPD) were determined to be 150 mg/L, 1 h, 0.1 g and pH 3. Fourier transform infrared (FTIR) spectroscopy of the adsorbents revealed that treated MHP showed amino groups attached to the adsorbents. Thermogravimetric analysis (TGA) revealed that the grafted material lowered the thermal stability from 180◦C to 300◦C due to volatile nature of DPC. The surface of the MHPD materials was rough due to grafting. The results showed that the 1,5’-diphenylcarbazide treatment improved the removal efficiency of Cr(VI).

Content: The utilization of mink waste generated through the industrial process attracted both industry and academia interests. In this study, the use of hydrogen peroxide as an oxidizing agent onto collagen producing self-crosslinking which extracting from mink solid waste was studied by infrared spectrum, fluorescence spectrum and thermal properties. The effect of hydrogen peroxide dosage and reaction temperature on the degree of oxidative self-crosslinking of collagen was analyzed by the changes of molecular structure and thermal stability. It was found that, hydroxide groups on the collagen side-chains can be oxidized to aldehyde groups and carboxyl groups by hydrogen peroxide in alkaline environment. These oxidized groups can crosslink with functional groups on collagen by covalent bond and ionic bond, changing collagen molecular structure and improving thermal stability. When the dosage of hydrogen peroxide was 14.74% and reaction temperature was 40℃ ±, the oxidative self-crosslinking of collagen was the strongest. This study provided theoretical basis for the high-value utilization of mink wastes. Take-Away: 1. The oxidative self-crosslink of collagen extracted mink solid waste was studied. 2. Hydrogen peroxide was applied as environment friendly oxidant. 3. The change of functional groups and degree of crosslinks during the oxidation was studied via infrared, fluorescence spectrum and differential scanning calorimetry.

This thesis is focused on so-called diaphragm discharge, which is one kind of electric discharges in liquid, which belongs among so-called AOP´s techniques, still more used for water cleaning in the present. One of effectiveness and stability indicators of diaphragm discharge is generation of hydrogen peroxide. In theoretical part, detail principle description of electric discharge in liquid is situated. Further, properties of electrolyte are introduced and general spectrophotometric method of obtained sample determination is described. In experimental part, a full procedure of experiment is introduced. Next part containing results and discussions introduces particular results of individual measurements and their reasons. Final chapter is the end, which forms total summary and evaluation of all results. By the application of all chosen electrolytes in solution at diaphragm discharge formation of hydrogen peroxide has appeared. Inorganic and organic electrolytes were used. As inorganic electrolytes following salts were selected – solutions of halogenides, next sodium nitrate as a representative of nitrates, potassium dihydrogenphosphate as a representative of phosphates, etc. Representative of organic electrolytes was citric acid. The value of initial conductivity of electrolytes had the main influence on hydrogen peroxide formation. Electrolytes potassium dihydrogenphosphate and sodium sulphate the great influence on effectiveness and stability of the diaphragm discharge. Their rate constants reached maximum value by the application of solution with initial conductivity of approximately 400 mikrosiemens, particularly 0.0492 mmol/l.min and 0.048 mmol/l.min. On the contrary, low values of rate constant were achieved in electrolyte ammonium chloride at around the same initial conductivity – 0.0269 mmol/l.min. During experiments stainless steel and platinum electrodes were used. It was found that kind of electrode material hadn’t influence on generation of hydrogen peroxide. Hydrogen peroxide was formed only in the cathode space.

Les formes réactives de l’oxygène (peroxyde d’hydrogène, radicaux superoxydes et hydroxyles) sont produites lorsque la régulation du métabolisme de l’oxygène est perturbée. Ces espèces sont responsables, directement ou indirectement, de nombreux dommages oxydatifs au niveau moléculaire (acides nucléiques, protéines, lipides…) pouvant affecter les mécanismes cellulaires. Toutefois le peroxyde d’hydrogène pourrait également se comporter comme un messager secondaire dans différentes voies de signalisation et être à l’origine de processus physiologiques. Ainsi sa double fonction a suscité l’intérêt de nombreux laboratoires qui tentent à présent d’élucider son rôle et son degré d’implication dans les processus physiologiques et pathologiques. Pour la détection du peroxyde d’hydrogène, de nombreuses pro-sondes ont été élaborées sur la base d’une amorce boronate. La plupart de ces pro-sondes ont permis de détecter un stress oxydant in cellulo mais souffrent cependant d’un manque de réactivité. Le but du mon projet de thèse a alors été d’améliorer la réactivité de l’amorce en élaborant des pro-sondes à amorce borinate. Malgré des difficultés de synthèse, nous avons obtenu une telle pro-sonde à amorce borinate, dissymétrique, portant à la fois un phényle et la coumarine, choisie comme chromophore. Des études cinétiques ont montré que la réactivité de notre pro-sonde borinate est 100 fois plus élevée que celle des pro-sondes à amorce boronate actuelles, en conditions physiologiques. Un mécanisme réactionnel a été proposé. Enfin notre pro-sonde a pu être validée in cellulo sur des macrophages, activés au PMA pour la détection endogène du peroxyde d’hydrogène. Encouragés par ces résultats, nous synthetisons actuellement d’autres pro-sondes à amorce borinate présentant d’autres chromophores. / Reactive oxygen species (hydrogen peroxide, hydroxyl and superoxide radicals) are produced when the regulation of oxygen metabolism is disrupted. These species are directly or indirectly responsible for numerous oxidative damage at the molecular level (nucleic acids, proteins, lipids, etc.) which can affect cellular mechanisms. However, hydrogen peroxide could also behave as a secondary messenger in various signaling pathways and be the source of physiological processes. Thus its dual function has aroused the interest of many laboratories which are now trying to elucidate its role and its degree of involvement in physiological and pathological processes. In order to detect hydrogen peroxide, many pro-probes have been developed, based on a boronate trigger. Most of these probes proved able to detect an oxidative stress in cellulo but suffer from lack of reactivity. The goal of my thesis project was to improve the reactivity of the trigger by developing pro-probes with a borinate trigger. In spite of difficulties of synthesis, we obtained such a pro-probe with a borinate trigger, dissymmetrical, and bearing both a phenyl and a coumarin substituent, chosen as chromophore. Kinetic studies have shown that the reactivity of our borinate pro-probe is 100 times higher than that of the current boronate-based trigger pro-probe, under physiological conditions. A reaction mechanism has been proposed. Finally, our pro-probe has been validated in cellulo on macrophages, activated with PMA for the endogenous detection of hydrogen peroxide. Encouraged by these results, we are currently synthesizing other pro-probes with borinate trigger presenting other chromophores.

<p>Reactive oxygen species (ROS) are critical for maintaining cellular homeostasis and function when produced in physiological ranges. Important sources of cellular ROS include NADPH oxidases (Nox), which are evolutionarily conserved multi-subunit transmembrane proteins. Nox-mediated ROS regulate a variety of biological processes including stem cell proliferation and differentiation, calcium signaling, cell migration, and immunity. ROS participate in intracellular signaling by introducing post-translational modifications to proteins and thereby altering their functions. The central nervous system (CNS) expresses different Nox isoforms during both development and adulthood. There is now emerging evidence that Nox-derived ROS also control neuronal development and pathfinding. Our lab has recently shown that retinal ganglion cells (RGCs) from <i>nox2</i> mutant zebrafish exhibit pathfinding errors. However, whether Nox could act downstream of receptors for axonal growth and guidance cues is presently unknown. To investigate this question, we conducted a detailed characterization of the zebrafish <i>nox2</i> mutants that were previously established in our group. Abnormal axon projections were found throughout the CNS of the <i>nox2 </i>mutant zebrafish. Anterior commissural axons failed proper fasciculation, and aberrant axon projections were detected in the dorsal longitudinal fascicle of the spinal cord. We showed that the major brain regions are intact and that the early development of CNS is not significantly altered in <i>nox2 </i>mutants. Hence, the axonal deficits in <i>nox2</i> mutants are not due to general developmental problems, and Nox2 plays a role in axonal pathfinding and targeting. Next, we investigated whether Nox2 could act downstream of slit2/Robo2-mediated guidance during RGC pathfinding. We found that slit2-mediated RGC growth cone collapse was abolished in <i>nox2 </i>mutants <i>in vitro</i>. Further, ROS biosensor imaging showed that slit2 treatment increased growth cone hydrogen peroxide levels via mechanisms through Nox2 activation. Finally, we investigated the possible relationship between slit2/Robo2 and Nox2 signaling <i>in vivo</i>. <i>Astray/nox2</i> double heterozygous mutant larvae exhibited decreased tectal area as opposed to individual heterozygous mutants, suggesting both Nox2 and Robo2 are required for the establishment of retinotectal connections. Our results suggest that Nox2 is part of a signal transduction pathway downstream of slit2/Robo2 interaction regulating axonal guidance cell-autonomously in developing zebrafish retinal neurons.</p>

This study is dedicated to characterisation of photosensitisation properties of polymeric nanofibres with encapsulated photosentisitiser. Main goal of thesis is demonstration and study of H2O2 photoproduction. Photosensitizer used in this study was 5,10,15,20-meso-tetrafenylporfyrin (TPP), studied were also its complexes with Cu2+ a Ni2+ . Properties of nanofibers were examined using UV-Vis molecular absorption spectroscopy, fluorescence spectroscopy and electron microscopy (SEM).

During the construction of the new urban area in the north-eastern part of Stockholm, Stockholm Royal Seaport, groundwater with extremely elevated levels of the carcinogenic aromatic hydrocarbon benzene was discovered in the area Hjorthagen. Such a contamination can be remediated in-situ by the use of chemical oxidation and biodegradation. Due to the fact that many factors such as contaminant composition, groundwater characteristics and temperature vary between sites, smaller bench scale studies are usually conducted before the full scale remediation on site. Little published research exists on the ability of these remediation techniques in areas with lower groundwater temperature such as Stockholm, why the need of a bench-scale study in this case is even larger. The objective of this master thesis is to, out of three investigated remediation agents, find the most suitable one for remediation of the benzene-contaminated groundwater in Hjorthagen. This was made in the form of a bench-scale study and the techniques studied were chemical oxidation, for which the two agents hydrogen peroxide (uncatalyzed and catalyzed in the form of Fenton’s reagent) and persulfate (activated with iron (II)) were used, and biological degradation by the use of a calcium peroxide-based compound. The study showed that the benzene-contaminated groundwater was best remediated with Fenton’s reagent, which was able to degrade the benzene with great success.

<p>Open questions remain on the influence of various conditions and ion behavior on the hydration-shell of oily molecules. My research uses Raman spectroscopy and Raman multivariate curve resolution to study the hydration-shell of oily molecules as tools to help answer some of these open questions.</p><p>More specifically, I present results on the effect of molecular crowding on the structure of water around various oily molecules, and report the effect of molecular crowding on hydrophobic crossover. These results are important, as crowding has the potential to influence several fields, such as biology and environmental sciences. This work shows that increasing molecular concentration results in oil-oil crowding, decreases the tetrahedrality of the water structure around the oily molecules, and subsequently, the crossover temperature.</p><p>In addition to studying the hydration-shell under crowded conditions, I also present work on ion affiliation for the hydration-shell of an oily molecule. Ion affiliation for oil/water interfaces has been an ongoing topic of research since the Hoffmeister experiments because of their effect on biological processes. This study focuses on hydroxide and its affiliation for tert-butyl alcohol in comparison to other electrolytes. These results show iodide is less repelled by the oil/water interface in comparison to hydroxide.</p><p>Finally, I present findings on the influence of hydrogen peroxide in comparison to other small molecules on the water structure of an oily molecule. Hydrogen peroxide has been shown to reach supercooled temperatures, which may be useful in future studies of liquid phase transitions or studies on solute behavior at supercooled conditions. It is found that hydrogen peroxide does not significantly influence the water structure around tert-butyl alcohol, while other small molecules display significant water structure changes.</p><p>All these projects aim to contribute results to heated debates, as well as share information for future experiments.</p>