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Displaying theses 1-10 of 703 total
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B.J. van Enter
Master programme: Science for Energy and Sustainability - Physics / Chemistry January 31st, 2019
Institute: VU / Physics & Astr. Research group: Hybrid Solar Energy Conversion Graduation thesis Supervisor: Elizabeth von Hauff
Towards accurate glucose sensing: Determining the effect of pH on glucose detection
Diabetes is a worldwide epidemic that can cause severe medical complications. There are limitations on accuracy and practicality with the current technologies used for diabetes management, so research on improving techniques and on new technologies is prevalent. One of the technologies with great potential for glucose detection is Raman spectroscopy. Raman Spectroscopy is a useful analytical tool that can be applied to study glucose properties and concentrations in physiologically relevant (i.e. aqueous) solutions. Glucose is a unique organic molecule and thus has a unique Raman spectrum. In this MSC research project glucose was dissolved in aqueous solutions under varying acidity (pH 3 – 8), and measured with Raman spectroscopy, enzymatic test-strips and NMR. This way it was possible to measure the proposed change of equilibrium as well as checking the potential for Raman spectroscopy to reliably detect glucose under varying circumstances.
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A.V. Panteleev
Bachelor programme: Scheikunde January 30th, 2019
Institute: HIMS Research group: Heterogeneous Catalysis and Sustainable Chemistry Graduation thesis Supervisor: dr. N.R. Shiju
Dehydration of glucose to 5-hydroxymethylfurfural using WO3-doped Nb2O5 Catalysts
The increasing concern over the use of fossil fuels has resulted in increasing focus on the development of sustainable feedstocks for chemicals and fuels. Biomass is a promising candidate for this due to its abundance. Lignocellulose is the biomass that cannot be used as food, making it especially suitable as a feedstock. The glucose in lignocellulose can be dehydrated to hydroxymethylfurfural (HMF), a platform chemical that can be used for the carbon neutral synthesis of biofuels and important chemicals. To effectively gain HMF from biomass, an effective catalyst for the conversion of glucose to HMF is necessary. Niobium(V)oxide (Nb2O5) possesses the right characteristics for this. For transition metal oxides like Nb2O5 it is known that addition of tungsten(VI)oxide (WO3) results in more active acid sites, potentially improving yield. This study found the highest HMF-yield when the catalyst contained 30% WO3 and was calcined at 300°C. This is because WO3 has a different ratio of Lewis and Brönsted acid sites, so its addition can optimize the ratio for this reaction. Calcination at higher temperatures reduces the amount of available acids, causing the HMF-yield to decrease.
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Y. Boeije
Bachelor programme: Scheikunde January 28th, 2019
Institute: HIMS Research group: Molecular Photonics Group Graduation thesis Supervisor: Fred Brouwer
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Deep Ultraviolet Photochemistry of a Tin-oxo Cage
Nowadays, everybody is making use of microchips. To make more efficient laptops and mobile phones, the patterns in microchips should be made smaller. To achieve that, it is important to know how these patterns are created. With photolithography, a photoresist is exposed to light, which leads to a difference in solubility. Unfortunately, it is not well known how the solubility changes of most photoresists. The aim of this research was to discover what happens if a tin-oxo cage, which is a potential photoresist, is exposed to light. In this research, we got to know more about the photochemistry, by exposing a solution of the tin-oxo cage with a laser at 225 nm and analyzing with spectroscopic techniques. It was discovered that tin-carbon bonds split after the exposure, after which radicals are formed. The butyl radical converts to 1-butene, 1-butanol and 1,1-dimethoxybutane.
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E. Blokker
Master programme: Chemistry - Molecular Science January 17th, 2019
Institute: VU / Chem. & Pharm.Sc. Research group: VU Division of Theoretical Chemistry Graduation thesis Supervisor: Prof. Dr. F.M. Bickelhaupt
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Bonding Mechanisms of C-C, Si-Si and SiO-OSi Bonds – A Theoretical Study
In this thesis, we have studied the bonding properties of various selected single element-element, with the use of density functional theory (DFT) at BLYP-D3(BJ)/TZ2P. An elaborated analysis of the bonding mechanisms of R3AAR3 (A = C, Si, OSi) systems reveals the underlying physical factors that determine structure and stability of single bonds in the model systems and beyond.
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M.L.A. Hakkennes
Bachelor programme: Scheikunde January 17th, 2019
Institute: HIMS Research group: Synthetic Organic Chemistry Graduation thesis Supervisor: Dr. M.A. Fernádez Ibáñez
C-H olefination of 1,2,3,4-tetrahydroquinolines promoted by a S,O-ligand
Tetrahydroquinolines are abundant in natural products and bioactive compounds, but often require a multistep synthesis. In the last few decades functionalization of carbon hydrogen bonds has been a solution to bypass this problem. A new catalytic system developed by Fernández-Ibáñez et al., and based on palladium and a bidentate S,O-ligand, showed a greater acceleration on the C-H olefination of simple arenes. Furthermore, the catalytic system proved to be efficient for the selective para-C-H olefination of anilines. Herein, we report the C-H olefination of 8-substituted-1,2,3,4-tetrahydroquinolines using the Pd/S,O-ligand catalytic system.
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L.H. Polak
Master programme: Chemistry - Molecular Science December 20th, 2018
Institute: HIMS Research group: Homegeneous and Supramolecular Catalysis Graduation thesis Supervisor: Bas de Bruin
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Base-metal catalysed amidation reactions via acyl nitrenes from 1,4,2-dioxazol-5-ones
Amide-functionalized building blocks are widespread in natural and pharmaceutical compounds. Nevertheless, synthesis of these structures is highly challenging and usually requires multiple steps. Transition-metal catalyzed amidation reactions can provide a solution for this problem, yielding the product in one step with fewer byproducts. However, the required acyl nitrene intermediates are inherently unstable due to the Curtius rearrangement, in which the R group migrates from the carbonylgroup to the nitrogen atom. To circumvent this problem, 1,4,2-dioxazol-5-ones can be used as alternative nitrene precursors. After coordination to a transition metal, CO2 is eliminated resulting in an acyl nitrene species that can be utilized for a large variety of reactions, such as C-H amidation and aziridination reactions. Nevertheless, a Curtius rearrangement can still occur on the transition metal. Hence, the catalyst should be designed such that the desired reaction outcompetes the Curtius rearrangement. In this project, radical nitrene transfer catalysts and common carbene transfer catalysts were used as an inspiration to achieve direct amidation reactions via acyl nitrenes.
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M. Ahmad
Master programme: Chemistry - Analytical Sciences November 13th, 2018
Institute: HIMS Research group: Analytical Chemistry Literature thesis Supervisor: Freek Ariese
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A study on: Online analysis of photo-degradation
The goal of this literature study is find on-line spectroscopy methods that can measure photo degradation processes in the time dimension, preferably in combination with separation techniques and without any interfering with the process itself. Goals of this study are: Looking into certain aspects of photo degradation, creating criteria that spectroscopical approaches need to apply to, finding such approaches, comparing results of papers that show such methods and drawing a conclusion from the comparison.
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Scientific abstract (docx 13K)   Full text (pdf 5965K)

G.T.G. Bruijn
Bachelor programme: Scheikunde November 7th, 2018
Institute: VU / Chem. & Pharm.Sc. Research group: VU Division of Theoretical Chemistry Graduation thesis Supervisor: Ivan Infante
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The Electronic Structure of CdX (X = S, Se, Te) Quantum Dots
Nowadays, intensive research is conducted to quantum dots (QDs). These are nanocrystals of small size – usually between 2 and 10 nanometers – of semiconductor material. These QDs contain very promising optical and electronical properties that can be integrated in many fields of application. Think, for example, about solar panels, LED-lights, and optical amplifiers, that contain semiconductor materials. QDs can replace these ‘bulk materials’ on the nanoscale and this way give rise to more efficient systems and sharper colors. By adjusting the QD-size during synthesis, you can alter the BG. Because of their small size QDs have a large surface-to-core ratio which makes them very susceptible for interactions that could reduce their efficiency. In order to protect the core properties a shell – consisting of another semiconductor material – could be synthesized. Moreover, the core-shell dot is surrounded by ligands to provide stability during synthesis and to neutralize its charge (a QD does not consist of the same amount of positive as negative elements). In this research, the influence is tested of several aspects on the electronic structure of the dot. It is examined what happens when dot size is altered, the difference between several semiconductor materials, and what difference surface ligands make.
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M.H. Bistervels
Master programme: Chemistry - Molecular Simulation and Photonics October 29th, 2018
Institute: AMOLF Research group: AMOLF - Ultrafast Spectroscopy Graduation thesis Supervisor: Huib Bakker
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A Study on Stearic acid on the water-air interface probed by Sum Frequency Generation Spectroscopy
The interaction action of fatty acids on water is believed to play a major role in the oil yield that is obtained by water flooding oil recovery processes and one thinks that the composition of the water has a large influence in this. Conditions on the interfacial surface of two isotropic media can significantly differ from the conditions in the bulk which can lead to a very different behavior. Sum frequency generation (SFG) is a surface specific spectroscopic method that can measure the vibrational spectra between two isotropic media. The SFG output beam that is generated on a surface sample propagates on the sum of two input beams and allows to analyze direct information of the chemical species at the interface. The present work aims at the investigation of the configuration state of the deuterated carbon tail - Stearic acid (StA) on the water-air interface relative to varied system conditions, with the use of SFG spectroscopy. The condition changing in water was performed in terms of pH (3-11), salt concentration (0-2000 mM) and temperature (26-56 C). In order to gain information on the (deuterated carbon tail) carboxylic head group, the region (1800-2300 cm-1) 1400-1800 cm-1 has been probed.
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A. van Kooten Niekerk
Master programme: Chemistry - Analytical Sciences October 18th, 2018
Institute: VU / Other Research group: Biophotonics & Medical Imaging Literature thesis Supervisor: Dr. Freek Ariese
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New developments in Surface Enhanced Raman Spectroscopy – A review
The aim of this review was to provide an overview of the latest developments of novel substrates with respect to Surface-Enhanced Raman Spectroscopy (SERS). The topics discussed in this review are new developments in single-composition colloidal nanomaterials, multiple-composition colloidal nanomaterials, planar substrates, composite-metal substrates, SERS based sensors and hyphenated SERS methods. Overall, new morphologies for substrates have been employed as well as improvement of enhancement limiting parameters to gain more sensitivity, in some cases almost reaching single-molecule level. Also, more robust composite-metal substrates and several tuneable, facile and re-usable substrates have been employed. These developments promise a wide range of study perspectives for fundamental and industrial purposes.
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Scientific abstract (pdf 4K)   Full text (pdf 1809K)

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