Verdedigde doctoraten

Amin Jafarzadeh​

• 18/12/2020
• 15.00 uur
• ​Online Doctoraatsverdediging​
• Promotoren: Erik Neyts & Annemie Bogaerts
• Departement Chemie

Abstract

The interest in utilizing plasma catalysis for environmental purposes continues to grow. Since a plasma-catalytic reaction can benefit both from the reactivity of the plasma and the high product selectivity induced by the catalyst, it is important to understand the plasma-catalyst interaction at a fundamental level in order to maximize the synergistic effects in practical experiments. Because of the highly complex network of processes happening simultaneously, revealing the entire mechanism is not straightforward. Utilizing computer simulations, we can study each factor separately and obtain detailed information about their effect on the whole reaction network. As part of an integrated multi-scale simulation scheme for understanding plasma catalysis, atomic scale calculations provide valuable insight into the interactions and subsequent changes in the catalyst electronic structure and the reactivity of atoms, molecules, and radical species present in the plasma. In that context, this thesis aims to provide answers to the following questions from the atomistic point of view: (1) How can we model plasma-induced surface charging and its impact on the adsorption of size selected catalytic nanoclusters on a support material? (2), What is the effect of “surface charging” on the activation of molecules, such as CO2 adsorbed on supported metal clusters? (3), How can we model the effect of an externally applied electric field in plasma catalysis? (4), How does the electric field change the activation and chemisorption properties of CO2 molecules adsorbed on Cu surfaces when combined with the effects of surface charging and the catalyst surface morphology? (5), How do plasma-generated radicals affect the plasma-catalytic reactions, especially for the case of ammonia reforming of methane for HCN production on Cu surfaces?, and (6) How can we simulate the reactivity of vibrationally excited species in a plasma-catalytic non-equilibrium environment?

The results of this thesis have demonstrated that the plasma-induced changes in the electronic structure of catalysts and reactants have great potential in steering the plasma-catalytic reactions and the answers to the abovementioned questions could help to adjust and optimize plasma-catalytic processes towards revamping renewable energy resources and mitigating environmental issues arising from greenhouse gas production. ​ 

Yannick Uytdenhouwen

• 11/12/2020
• 14 uur
• Online doctoraatsverdediging 
• Promotoren: Annemie Bogaerts & Pegie Cool
• Departement Chemie

Abstract

Combatting the ever rising concentrations of greenhouse gases in the atmosphere, in particular CO2 and CH4, is one of the biggest challenges of peoplekind in this century. Reducing emissions and developing innovative solutions for capturing and reusing the gases that are inevitably produced, are the tasks at hand for the next decades. However, novel technologies are required in order to convert these greenhouse gases in a sustainable and efficient way. Plasma technology could offer a viable solution, by directly targeting the molecules in reacting into value-added chemicals. Their quick on-and-off-switching capabilities by electrical energy, in combination with intermittent renewable energy sources, makes them a promising technology to directly convert CO2 and CH4 in a sustainable way. Therefore, in this work, we studied the potential use of the DBD reactor for sustainable CO2 and CH4 conversion. We aimed to improve the reactor performance via different methods, and to develop a technique to gain more fundamental insight on how the kinetics in the reactor change on the macro scale when optimising the performance. First we investigated the influence of micrometre sized discharge gaps and packing materials to enhance CO2 dissociation conversions. The results show that smaller gap sizes are beneficial and that the performance of a packing material greatly depends on the specific combination of material composition, sphere size, and gap size. Further investigation with core-shell structured spheres showed that overall sphere properties can be optimised to a specific use. Next, an apparent first order reversible reaction fit was developed to retrieve more fundamental parameters, such as equilibrium conversion and reaction rate coefficients, on a macro level scale. By tracking the reactor conversion over a wide range of residence times for different cases and matching the results to our fit, we have elucidated how the applied power, reactor pressure, discharge gap size, and the addition of packing materials change the kinetics to influence the reactor performance in CO2 dissociation, CH4 reforming, and dry reforming of methane and their product distribution. Finally, we explored whether the reactor performance can be optimised for bi-component gas mixtures by altering the gas flow design in the reactor. The results assessed the potential of this method for dry reforming of methane and ammonia synthesis and showed room for improvement in conversion and product distribution.

_​Vincent Vermeiren​

• 23 november 2020
• Promotor: Annemie Bogaerts
• Departement Chemie
• Locatie: Online doctoraatsverdediging
• Tijdstip: 11 uur

Abstract

The problem of global climate change due to the emission of greenhouse gasses has accelerated the transition from fossil fueled energy sources to renewable ones. However, the intermittency of these energy sources makes their implementation challenging. Hence, there is an urgent need for more research on methods to store this excess electrical energy at peak production. Plasma technology has been shown to efficiently convert CO₂ to CO (and oxygen), which can then be used to synthesize hydrocarbons through the Fischer-Tropsch process. However, more insight is needed in the importance of the underlying chemistry, and the different dissociation pathways.

In our research, we aim to reveal the conditions at which the most energy efficient dissociation of CO₂ takes place, for plasmas in which both vibrational induced dissociation and thermal dissociation become important.

First, a supersonic flow microwave plasma model is investigated. This model reveals the effect of the flow on the plasma performance. The results reveal that the time delay for vibrational induced dissociation to take place, as well as the maximum specific energy input that can be added before the flow is choked are the main limitations to reaching high energy efficiency.

Next, it is shown that pulsing the plasma can increase the vibrational-translational non-equilibrium, that is needed for efficient vibrational induced dissociation. The maximum improvement is reached when the plasma pulse time equals the time at which the vibrational temperature reaches a maximum value, and for long interpulse times, so that the gas can cool down before the next pulse starts.

Finally, the effect of thermal quenching on the plasma performance is investigated for warm and cold plasmas at different specific energy inputs. It is shown that quenching can increase the final CO₂ conversion by reducing the recombination mechanisms, and that high efficiencies are reached for thermal plasmas in combination with quenching.This PhD thesis increases our knowledge of the kinetics in CO₂ plasmas, and gives valuable insight for experimentalists.

Link: https://eu.bbcollab.com/guest/8c4d58f9b42341b1873723a4b43a8d41​

Mats de Jong

• 27 augustus 2020
• Promotoren: Karolien De Wael en Nele Samyn
• Departement Chemie

Abstract

Illicit drugs are everywhere in our society. The clandestine market is growing faster than ever before, with record breaking seizures in Europe (and particularly Belgium) concerning cocaine. Cocaine is singled out as a major substance of interest, in Europe and Belgium in particular. Currently used field tests for cocaine detection have several downfalls. They lack specificity, leading to false positive results, and are also easily bypassed by adding other (often colored) compounds, producing many false negative results. This lack of accuracy causes large costs for society: juridical, health-wise and economical. This, combined with the continuously growing drug retail market, presses the need for new and better portable detection devices for cocaine. This PhD thesis aimed at the development of a portable, reliable electrochemical sensor device for cocaine, allowing accurate analysis in field settings such as the Port of Antwerp. The potential of the electrochemical approach to replace other field techniques was tested and evaluated throughout the project. Electrochemical detection, square-wave voltammetry in particular, allows a fast (<40 s) analysis with high sensitivity, specificity and the possibility to detect multiple compounds (illicit drugs, adulterants and diluents) in one measurement scan, making it perfect for on-site screening purposes. In order to obtain this optimized electrochemical approach for cocaine, several fundamental and applied research steps were conducted of which the results are presented in this thesis: (1) determination of methodology and identification of interfering compounds, (2) defining the interfering mechanism of these compounds and provide solutions, (3) test possibility towards polydrug analysis (heroin), and (4) validation and field testing. This approach was followed to guide our fundamental research towards a highly relevant application. This PhD involved close collaboration with the National Institute for Criminalistics and Criminology, as well as with the Netherlands Forensic Institute, the Federal Judicial Police and Belgian Customs. All these agencies provided expert insights into the topic, as well as access to confiscated cocaine street and smuggle samples to help validating the developed technology. Lab validation on 374 samples delivered an accuracy of 98.4 % for the developed sensor, while the field measurements presented clear advantages over other screening tests, certainly concerning the detection of cocaine in colored and mixed smuggle samples. In conclusion, this work includes the research foundations to bring this cocaine detection technology to the market, where it has the potential to replace other commonly used screening techniques.

Joy Eliaerts​

• 3 juni 2020
• Promotoren: Karolien De Wael, Koen Janssens en Natalie Meert
• Departement Chemie

Abstract

Wereldwijd is cocaïne één van de meest inbeslaggenomen en gebruikte drugs. De huidige screening van cocaïne in inbeslaggenomen poeders wordt uitgevoerd met kleurtesten. De voornaamste nadelen van deze testen zijn een gebrek aan specificiteit en een subjectieve kleureninterpretatie (’50 shades of blue’). De hoge prevalentie van cocaïne en de beperkingen van de kleurtesten hebben ertoe geleid dat er een algemene interesse is in het ontwikkelen van een snelle methode voor identificatie en kwantificatie van cocaïne.

In dit doctoraat werd een nieuwe strategie ontwikkeld met behulp van Midden-InfraRood [MIR] spectroscopie en Support Vector Machines [SVM]. De SVM modellen resulteerden in een duidelijke output (cocaïne gedetecteerd/niet gedetecteerd) en in een betrouwbare schatting van de zuiverheid van cocaïne in verschillende soorten straatstalen. De MIR techniek gecombineerd met SVM is een eenvoudige, gebruiksvriendelijke en snelle methode voor het identificeren en kwantificeren van cocaïne.

De ontwikkelde chemometrische modellen werden in de praktijk toegepast op grote inbeslagnames van cocaïne. Er werd een strategie ontwikkeld om informatie te bekomen over de homogeniteit van loten, de aanwezigheid en de concentratie van cocaïne en zijn meest voorkomend versnijdingsmiddel, levamisol. Deze werkwijze had tot gevolg dat zowel het aantal staalnames als het aantal bevestigende analyses konden worden verminderd.

Verder werd nagegaan of de ontwikkelde modellen konden worden gebruikt bij een ander MIR instrument van hetzelfde merk. Voor het uitvoeren van deze kalibratietransfer werden verschillende mogelijkheden vergeleken. Een gemengd model, opgebouwd met data van beide instrumenten, was het meest succesvol en kon worden gebruikt op beide instrumenten voor het detecteren van cocaïne.

Om na te gaan of andere spectroscopische technieken zoals Raman en Nabij-InfraRood [NIR], naast de MIR techniek, kunnen worden aangewend voor het classificeren en kwantificeren van cocaïne, werd een vergelijkende studie uitgevoerd. In het algemeen presteerden deze technieken gelijkaardig en kunnen ze als goede alternatieven voor de MIR techniek worden beschouwd.

Ten slotte werden de huidige screeningstechnieken (kleurtesten en MIR spectroscopie) geëvalueerd voor de detectie van cocaïne in complexe smokkelstalen. Het detecteren van cocaïne was enkel mogelijk na het uitvoeren van een extractie vóór screeningsanalyse.

Als besluit kan gesteld worden dat de combinatie van spectroscopische technieken met chemometrische methoden een belangrijke meerwaarde biedt voor de initiële screening van cocaïne. Bovendien is een schatting van de zuiverheid mogelijk zonder het toepassen van ‘wet chemistry’. De vergaarde kennis in het kader van dit werk kan ook worden toegepast voor de detectie van andere veelvoorkomende drugs zoals heroïne en amfetamines.

Parisa Nematollahi

• 27 mei 2020
• Promotor: Erik Neyts 
• Departement Chemie

Abstract

Since the industrial revolution, the global air and sea temperature has increased significantly because of the rise in the concentration of greenhouse gases. Therefore, extensive research is carried out to both minimize the carbon emission from the exhaust of automobiles, petrochemical, agricultural and chemical industries, and reduce the current high levels of greenhouse gases by converting them into carbon-neutral fuels and other value-added industrial chemicals.

Graphene-based nanocatalysts are of great interest to the catalysis community due to their outstanding catalytic activity, surface properties, environmental friendliness, and cost-effectiveness. Surface modification of graphene-based materials is of great interest since it enhances the catalytic activity, electronic property, mechanical strength, and thermal conductivity of the nanocatalyst. The most commonly used surface modification methods are introducing defects, and doping with single metal atoms.

Two promising nanocatalysts are graphene and BC2N nano-flakes. The surface modification includes introducing defects or doping with single metal atoms. Depending on the type of nanocatalyst, the type of defects may change. The exact characteristics of the modified surfaces, the detailed reaction mechanisms, and the potential energy surface of direct conversion of methane to methanol, along with CO and NO oxidation to CO₂ and NO₂ on these surfaces at ambient conditions are unclear. Therefore, finding the corresponding reactions, detailed mechanisms, and characteristics of the tailored nano-surfaces was the main goal of this Ph.D. All the simulations were carried out using density functional theory (DFT) calculations. Our results reveal that the modified graphene and BC₂N nanoflakes hold great promise toward gas conversion. Using these tuned nanostructures is energetically and thermodynamically interesting since they reduce the oxidation steps and their energy barriers, the formation of sub-chemicals, the possibility of surface poisoning with unwanted species, and make the reactions occur at ambient conditions. Our results may serve as guidance for fabricating a cost-effective graphene-based single-atom catalyst.

Roberta Sgammato​

• 8 mei 2020
• Promotoren: Wouter Herrebout en Christian Johannessen
• Departement Chemie

Abstract

Globins are haem containing proteins ubiquitously expressed in all kingdoms of life, from bacteria to vertebrates. Thanks to the haem iron, globins can reversibly bind small ligands and can be involved in redox reactions. Nowadays more than 400 globins have been identified and classified into three main lineages and two structural families. Many of the recently discovered globins exhibit quite unusual structural architecture and a still unexplored mechanism of action. Revealing details about their structure-function paradigm can have an important biomedical relevance: a simple interaction between the globin haem iron with an exogenous ligand can eventually change the habits of the host organism and influence its adaptability to the environment, or in some cases its virulence. Moreover, some newly characterised globins are thought to have a neuroprotective function, hence a detailed knowledge of their mechanism of action could be beneficial for pharmacological purposes.

In the present work, we propose a spectroscopic approach to the study of haem-containing proteins, based on a combination of chiroptical techniques. In particular, we base our investigation on the use of resonance Raman optical activity (rROA) and electronic circular dichroism (ECD). While these techniques are routinely employed for the determination of the absolute configuration of natural compounds, their application to the study of the haem chromophore in globins, has been so far very poorly explored. The present thesis represents therefore a first, preliminary approach to relatively simple globins (or globin domains solely), using a non-classical spectroscopic approach. We have highlighted the capability of this methodology to detect conformational modifications of the achiral haem chromophore when placed in a protein matrix, and its fine sensitivity to small perturbations of the haem planarity induced by ligand binding. The early results show the potential of the chiroptical approach, and set the bases for a future investigation of more complex chimeric globins, via rROA and ECD.

Jeroen Van Dijck

• 4 mei 2020
• Promotoren: Vera Meynen en Anita Buekenhoudt
• Departement Chemie

Abstract

Organic surface modified metal oxides are of great interest for the chemical due to their selective control of surface properties, triggering particular features and enhancing performance in applications. The most commonly used surface modification technique is organosilylation. Organosilylation of metal oxides is not ideal because the stability of the resulting organic layer is limited. Therefore, the search for more suitable surface modification techniques for metal oxides has gained significant interest over the past years.Two promising alternatives are organophosphonic acid surface modification and Grignard surface modification. Organophosphonic acid modification is a condensation reaction between the organophosphonic acid and the surface hydroxyls of the metal oxides. Stable (sub)monolayers are grafted and the modification can be easily controlled by adjusting the reaction conditions. A drawback is that multiple bonding states exist, which could introduce side interactions. Moreover, it is often difficult to control the type and uniformity of these bonding states. Therefore, another alternative method has been developed by UAntwerpen and VITO: Grignard surface modification. It results in a direct bond between the organic functional group and the metal oxide surface, meaning that no reactive bonds of the precursors remain unbound on the surface. Grignard modification is not a condensation reaction and its exact mechanism is unclear. Therefore, unravelling this mechanism has been one of the key research questions of this PhD.Both methods give rise to entirely new generations of organic modified metal oxides surfaces with unique physicochemical properties and behavior in application, that can be tailored to the application when the synthesis-properties and properties-performance correlations can be unraveled. While the impact of reaction conditions on the surface properties has been (partly) described for organophosphonic acid modification, the impact of these differences in surface properties on the affinity of the modified surface for molecular interactions has not been studied in-depth. For the Grignard surface modification insights in both the synthesis-properties and properties-performance correlations is missing due to the lack of understanding of the modification mechanism. It is for that reason, that this PhD has a particular attention on the one hand for unravelling part of the synthesis-properties correlation of Grignard modification on titania, by gaining a better understanding of the mechanism and the impact of reaction conditions, and on the other hand to study the impact of the synthesis on the sorption behavior of both Grignard and phosphonic acid modified surfaces.

Stijn Heijkers​

• 27 april 2020
• Promotor: ​Annemie Bogaerts
• Departement Chemie

Abstract

The ever increasing atmospheric CO₂ concentrations lead to accelerated global warming. Therefore, we should reduce our greenhouse gas emission drastically by shifting towards renewable energy and by storing this (fluctuating) energy through simultaneously converting greenhouse gases into fuels or value-added chemicals. One emerging technology for this purpose is plasma technology. Plasma chemical kinetics modelling is very suitable to gain more knowledge in the underlying plasma processes, needed for further optimization. Therefore, in this PhD thesis we focus on chemical kinetic modelling of CO₂ and CH₄ in different plasma reactors.We studied the most important processes in pure CO₂, CO₂/CH₄ and CO₂/N₂ mixtures in a gliding arc plasmatron (GAP). The GAP shows the advantage of intense vibrational excitation at atmospheric pressure, beneficial for industrial implementation. However, the CO₂ dissociation mainly occurs from the lowest vibrational levels, due to the high temperature in the arc (3000 K), so that the vibrational-translational non-equilibrium is negligible. Adding CH₄ enhances the CO₂ conversion, and the overall performance in terms of energy cost / energy efficiency reaches values above the required efficiency target, due to the reaction of CO₂ with H atoms, formed upon dissociation of CH₄. The addition of N₂ causes the formation of NO and NO₂. However, the NO_x concentrations reached are somewhat too low to be valuable for N₂ fixation.Pure CO₂ splitting was also studied in a nanosecond repetitively pulsed (NRP) discharge, which shows promising results by stimulating vibrational excitation. More than 20 % of all CO₂ dissociation occurs from the highest asymmetric stretch mode levels. However, in between the pulses, fresh gas entering the plasma, VT relaxation and recombination reactions limit the overall conversion and energy efficiency.Finally, we studied CH₄ conversion in different plasma reactors, i.e., dielectric barrier discharge (DBD), microwave (MW) plasma and GAP. Higher temperatures, especially in the GAP but also in atmospheric pressure MW plasmas, result in more CH₄ conversion, and in neutral dissociation and dehydrogenation of the hydrocarbons created, forming especially C₂H₂ and H₂, and (some) C₂H₄. Low temperature plasmas, such as DBD and reduced pressure MW plasmas, result in more electron impact dissociation and three-body recombination, creating more saturated compounds, i.e., mainly C₂H₆, but also higher hydrocarbons..Overall, the results of this thesis give valuable insight in the possibilities and limitations of plasma-based CO₂ and CH₄ conversion.

Fabio Bottari​

• 20 januari 2020
• Promotoren: Karolien De Wael en Ronny Blust
• Departement Chemie

Abstract

In the broad context of food and environmental safety, the development of selective and sensitive analytical tools for the detection of β-lactam antibiotics in milk down to their Maximum Residues Limits (MRL), is still an open challenge. To address this need, the design of new bio(mimetic) electrochemical sensors was investigated in the present thesis. These sensors are based on the intrinsic electrochemistry of β-lactam antibiotics, taking advantages of the characteristic electrochemical fingerprints of the core structures and redox active side chain groups. Once verified the applicability of a direct electrochemical detection, different sensor configurations were tested mainly focusing on:

- the selection and validation of aptamers to be used as bioreceptors in the development of β-lactam biosensors;- the design of biomimetic receptors, particularly molecularly imprinted polymers, and other synthetic electrode modifiers compatible with a direct detection strategy.

Lastly, the research activity was directed towards milk sample analysis following two parallel routes: the development of a pre-treatment protocol for raw milk, based on solvent addition and the study of β-lactam antibiotics electrochemistry in undiluted raw milk.

Jeroen Van Dyck

• 16 januari 2020
• Promotoren: Frank Sobott en Dirk Snyders
• Departement Chemie

Abstract

Native mass spectrometry has shown over the past years to be a very useful tool in the investigation of membrane proteins and pores, which provides additional information next to the conventional structural techniques. This information concerns for example the stoichiometry of complexes and structural information. In recent years native mass spectrometry has shown to be very useful for the investigation of large noncovalent, mainly globular structures. In this thesis different projects are presented and discussed showing the versatility of native mass spectrometry; including membrane associated proteins and nanopores build from custom designed DNA strands. To investigate each of the different projects ion mobility and mass spectrometric techniques were used. This also includes the methods of sample preparation required to transfer the samples into the gas phase without disturbing the complexes formed significantly.

The BAX protein revealed to behave differently, when different detergents were present in solution above the critical micelle concentration or when binding the directly activating molecule BAM-7. Ion mobility and mass spectrometry show that it forms oligomers and conformational changes.

Native mass spectrometry turned out to be very useful in the investigation of lipid interactions with membrane proteins. This was shown by MgtA membrane protein revealing a very specific binding of lipids. Native MS has shown to be very useful for observing of specifically bound lipids even when high concentrations of other lipid were present.

DNA origami is a term used for artificial designed nano-structures from DNA building blocks. Within this thesis the formation of such a DNA nano-structure was investigated concerning the formation of a DNA nanopore. This pore is formed from different DNA strands which should only fit together in one possible manner. Using ion mobility mass spectrometry it was shown that the salt concentration, in the form of ammonium acetate, has a profound influence on the actual form of the hexameric pore.

Charlotte Vets 

• 10 januari 2020
• Promotor: Erik Neyts

Abstract

Nanomaterialen van koolstof zijn veelbelovend voor verschillende toepassingen in de elektronica. In dit werk bestudeerden we twee van deze materialen: koolstofbuisjes en carbyn. Beiden bestaan in verschillende geometrieën, die hun elektrische eigenschappen bepalen. De geometrie wordt gedefinieerd tijdens het maken, ofwel groeien, van de materialen. Om ze effectief te kunnen gebruiken in elektronische toepassingen, is het dus cruciaal om het groeiproces te controleren. Dit is momenteel nog zeer moeilijk. Daarom proberen we in dit werk de invloed van een aantal mechanismen die belangrijk zijn tijdens de groei, uit te klaren. Zo hopen we meer inzicht te krijgen in hoe de groei gestuurd kan worden richting materialen met specifieke elektrische eigenschappen. Computersimulaties, meer bepaald dichtheidsfunctionaaltheorie (DFT) en moleculaire dynamica (MD), werden gebruikt om de groeimechanismen van koolstofbuisjes en carbyn te onderzoeken.Koolstofbuisjes zijn opgerolde hexagonale netwerken van koolstofatomen. Om ze te kunnen groeien is een katalysator nodig. De randstructuur van het hexagonale netwerk, ofwel de chiraliteit, definieert de elektrische eigenschappen van het koolstofbuisje. De meest gebruikte katalysatoren zijn nanodeeltjes van Ni, Fe of Co. Uit experimenten komen bimetallische katalysatoren echter veelbelovend naar voren voor chiraliteitscontrole. Daarom deden we een studie met zowel DFT als Born-Oppenheimer MD naar stabiliteiten van NiFe, NiGa en FeGa nanodeeltjes.Zowel thermodynamische als kinetische mechanismen spelen een rol in de groei van koolstofbuisjes. Het thermodynamische mechanisme werd bestudeerd door middel van de adhesie-energie tussen koolstofbuisjes met verschillende chiraliteiten en Ni, Fe en FeNi nanodeeltjes. Hierbij maakten we gebruik van DFT-berekeningen. We onderzochten of de adhesie-energie tussen koolstofbuisje en katalysator gestuurd kan worden door het gebruik van bimetallische katalysatoren in verschillende concentraties, om zo chiraliteitsselectieve groei mogelijk te maken.Uit de verschillende kinetische mechanismen werd defectheling gekozen, omwille van de hoge invloed op chiraliteitsvorming. Defectheling werd bestudeerd met behulp van klassieke MD. We onderzochten de invloed van het contact tussen defect en metaalkatalysator op defectheling. We bestudeerden stabiliteiten van koolstofbuisjes met 5-7 defecten, Stone-Wales defecten en vacatures, en evalueerden deze resultaten op Ni nanodeeltjes.Naast koolstofbuisjes bestudeerden we ook carbyn. Carbyn is een lineaire koolstofketen. Hoewel carbyn met succes is gesynthetiseerd in dubbelwandige koolstofbuisjes, is het groeimechanisme nog niet gekend. Het is echter wel duidelijk dat dit groeimechanisme afhankelijk is van de katalysator en de precursor. We bestudeerden de nucleatie en groei van verschillende koolstofketens in een dubbelwandig koolstofbuisje dat Ni bevat, met koolstoffen en koolwaterstoffen als precursors.