Modelagem da formação de fuligem baseada no método das seções : efeitos do CO2 e acoplamento com a técnica FGM

Regulamentações relacionadas as emissões de fuligem estão se tornando mais restritivas devido ao impacto negativo da fuligem no meio ambiente e na saúde humana. Desta forma, a massa total de fuligem e o tamanho das partículas emitidas devem ser controlados. Novas tecnologias de combustão, como oxy-fuel aliado a recirculação de gases de exaustão, tem demonstrado um grande potencial de redução da formação de poluentes. Neste contexto, este trabalho explora os efeitos da adição do CO2 na formação de fuligem em chamas de etileno enriquecidas em oxigênio. Chamas unidimensionais laminares contra-corrente foram estudadas numericamente considerando cinética química detalhada, modelos avançados de radiação térmica e o método das seções para a formação de fuligem. O método das seções contabiliza processos físicos (nucleação, condensação e coagulação) e químicos (crescimento super cial e oxidação) da formação da fuligem e é capaz de descrever a distribuição de distintos tamanhos de partículas. A radiação é resolvida através da equação da transferência radiante considerando o modelo da soma ponderada dos gases cinzas (WSGG) ou o método linha-por-linha (LBL) para a integração espectral. Os efeitos químicos, termo-físicos e radiantes do CO2 sobre formação de fuligem foram investigados através da adição de CO2 nas misturas de combustível e oxidante. Foi observado que o CO2 suprime a formação e o crescimento dos PAHs, levando a redução da produção de fuligem. Enquanto os efeitos químicos são mais importantes para a supressão dos PAHs quando o CO2 é adicionado ao oxidante, efeitos químicos e termo-físicos são igualmente importantes quando o CO2 é adicionado ao combustível. Em ambos os casos, efeitos químicos são mais signi cativos para a supressão da formação de fuligem. Uma vez que modelos globais de radiação térmica devem ser capazes de predizer adequadamente a estrutura de chamas, soluções obtidas com o modelo WSGG de superposição foram comparadas com soluções empregando a integração LBL. Pela primeira vez a abordagem LBL é empregada de forma acoplada com modelo detalhado de cinética química e o método das seções. Observou-se que o modelo WSGG de superposição obteve resultados similares aqueles encontrados com a integração LBL para a estrutura geral da chama e as predições de fuligem. Também foi mostrado que a reabsorção de radiação pelo meio participante é fundamental para as predições de fuligem, mesmo para baixos níveis de adição de CO2. No entanto, essas simulações detalhadas são computacionalmente demandantes mesmo para simulações unidimensionais. Visto que as técnicas amelets são capazes de modelar a cinética química detalhada de forma e ciente e acurada, simulações numéricas também foram conduzidas visando explorar a modelagem da formação de fuligem utilizando a técnica Flamelet-Generated Manifold (FGM). Os resultados indicaram que a técnica FGM, considerando efeitos de difusão preferencial e a abordagem simpli ca de PAHs agrupados (atuando como conexão entre a fase gás e sólida), foi capaz de prever a formação de fuligem para uma ampla faixa de taxas de deformação de chamas planas (sem efeitos de curvatura) quando comparadas com simulações detalhadas. Por outro lado, a técnica FGM, considerando um manifold formado somente por chamas planas, capturou apenas qualitativamente os processos de formação de fuligem em chamas curvadas, demonstrando a necessidade de expandir o manifold atual para contabilizar os efeitos de curvatura. Ainda é importante ressaltar que a técnica FGM foi aproximadamente três vezes mais rápida que a abordagem de cinética química detalhada para as simulações da formação de fuligem, e aproximadamente setenta vezes mais rápida quando somente a fase gás foi resolvida.Soot emissions severely damage the environment and human health. Thus, total mass and particles size of soot released from hydrocarbon combustion has to be controlled and reduced. Combustion technologies such as oxygen-enriched and oxyfuel allied with flue gas recirculation have demonstrated their potential for reducing pollutants. In this context, this work explores the effect of CO2 addition on the soot formation process under an oxygen enriched atmosphere. A set of one-dimensional laminar counter ow ethylene flames are numerically studied accounting for detailed chemistry together with an advanced model for thermal radiation and the discrete sectional model for soot formation. The radiation is solved by the radiative transfer equation with with the superposition weight-sum-of-gray-gases (WSGG) model or the line-by-line (LBL) approach for the spectral integration. The effects of CO2 on soot formation was addressed for CO2 addition on either the fuel and on the oxidizer mixtures and different contributions by chemical, thermophysical and radiation effects were identified. It was observed that CO2 suppresses the formation of PAHs building block species, leading to a suppression of larger PAHS and, consequently, in the soot formation. Regarding the suppression of larger PAHs formation, it was found that whereas chemical effects played a major role for the CO2 addition on the oxidizer side, both chemical and thermophysical effects are important for CO2 addition on the fuel side. Soot is mainly suppressed by chemical effects of CO2 addition. Since, global radiative models should be able to reproduce detailed radiation simulations at conditions found in flames, solutions with the global superposition WSGG radiation model were compared to the LBL integration. For the first time, the LBL radiation model was coupled to detailed chemical kinetics and the discrete sectional model. It was observed that the superposition WSGG model is able to accurately describe general ame structure and soot predictions respective to the LBL integration approach for the current flames and that radiation reabsorption is important for soot predictions even for low levels of CO2 addition. However, those detailed simulations of soot formation are computationally intensive even for one-dimensional simulations. Because flamelet techniques are powerful tools for modelling complex chemical kinetics with efficiency and good accuracy, numerical investigations were also conducted to gain insight about the soot formation modelling with the Flamelet-Generated Manifold (FGM) technique. The results indicated that the FGM technique, considering differential diffusion effect and the solution of lumped PAHs (acting as a link between the gas- and the solid-phases), was able to predict soot formation over a wide range of strain rates for at (zero curvature) flames when compared to detailed simulations. On the other hand, curved flames obtained with a manifold formed solely by flat flamelets showed that soot formation was only qualitatively reproduced by the technique, making clear the necessity of expanding the current manifold to take into account curvature effects. It is worth pointing out that the FGM technique was up to three times faster than the detailed approach for soot modeling, and up to seventy times faster when only the gas-phase was solved

Computational investigation of the photochemistry and spectroscopy of cyclic aromatic hydrocarbons in interstellar ice analogs

This thesis describes the photochemistry and ultraviolet (UV) spectroscopy of cyclic aromatic hydrocarbons such as benzene and naphthalene, along with small water clusters and crystalline water ice clusters. Firstly, benzene and naphthalene interactions with small water hexamer (W6) clusters, and then benzene interactions with crystalline water ice clusters are investigated. This thesis primarily focuses on the applications of a range of computational chemistry techniques to investigate and characterize excited states of these complex systems, which are generated following one-photon absorption. Benzene and naphthalene, as prototypical polycyclic aromatic hydrocarbons (PAHs), and water and crystalline ice clusters, taken as representative of interstellar ices, could also be considered as useful model systems to replicate polycyclic aromatic hydrocarbons (PAHs) in interstellar ices, and to study their behaviour under UV processing. From coupled cluster (CC) benchmark studies on small water clusters up to water the pentamer, it is shown that that highly correlated linear-response coupled cluster methods such as CCSD and CC3 are important to consider while studying electronic excitations, as electron correlation effects play an important role in such systems, with double excitations playing a dominant role. However, triple excitations contributions calculated are negligible with CCSD and CC3 methods converging monotonically to similar results. The aggregation effect on water at CCSD level has shown a blue shift of ~ 0.7 eV in the central water molecule of water pentamer (C2v) relative to water monomer (C2v), and is in good agreement with the experimental blue shift of ~ 1 eV in condensed phase. For both benzene- and naphthalene-bound water W6 clusters, we have calculated interesting features of benzene- and naphthalene-mediated electronic excitations of the water W6 cluster at wavelengths where photon absorption cross section of water is negligible i.e., above 170 nm. These excitations were originally absent in the isolated water W6 cluster. Similar features are calculated for benzene-bound crystalline ice clusters, which also illustrate the effect of cyclic aromatic hydrocarbons on electronic excitations of ice clusters, and are also observed experimentally. The brightest → ∗ electronic transition of benzene and naphthalene is calculated to be red-shifted in wavelength and occurs with lower intensities after interacting with the water W6 and ice clusters. The degeneracy of this transition is also slightly broken in benzene. We have observed new electronic transition features such as charge transfer (CT), and locally diffuse Rydberg type excitation in these complexes. We have found a good performance of hybrid DFT functionals i.e. M06-2X and CAM-B3LYP in calculating vertical excitation energies of these complexes using time dependent density functional theory (TD-DFT). Further, diffusion studies of the deuterium (D) atom have shown the importance of surface morphology in generating different potential sites and hopping characteristics of the D atom on crystalline and amorphous ice surfaces. D2 formation is found to be efficient on the amorphous ice surface, with longer residence times of the D atom indicating a possibility of the deuterium atom getting trapped in such sites. There is then a further possibility of the diffusing D atom to recombine with the trapped D atom to form a D2 molecule. However, such D atom trapping is a rare possibility on crystalline surface, as hopping is fast and thus the recombination process is not efficient on crystalline ice surface

Flame-Formed Carbon Nanoparticles: Synthesis and characterization

Nanoparticles and nanostructured materials characterize an increasing research area, gaining strong attention from the scientific community in several fields. During the last decades, many and extraordinary technological advances have been obtained by nano-materials due to their physicochemical properties. In nature, at micro- and nano-scale, materials have existed for a long time before, but it is only through the advent of the technological era, and consequently, the development of nanotechnology, that they have come to the fore. There are several forms of nanoparticles: metal-based, organic-based or organic/inorganic combination and carbon-based ones. Carbon nanoparticles are the most widely studied as carbon is suitable and available raw material. Except for hydrogen, carbon has the most significant number of known compounds and is present on the planet in various forms: from carbon to light and heavy hydrocarbons. Carbon-based nanoparticles have shown a wide variety of structural arrangements that make them a great advantage as they are suitable for various purposes. Several techniques exist to cope with the production of the nano-size materials in both liquid and gas phase; examples are arc-discharge, laser ablation, chemical vapour deposition. The more the process allows to have a production (functional to specific final characteristics of the material) on a large scale and in an economical way, the more it is taken into consideration and studied. Among the various techniques, the use of flame and, therefore, combustion technology is increasingly taken into consideration. Traditionally, combustion is associated with the study of particulate matter and undesired products released into the atmosphere daily to understand the onset of their formation and reduce, if not abate, their emissions. Nevertheless, on the other hand, flame-formed carbon nanoparticles have been the subject of increasing interest in recent decades as a new procedure for synthesizing engineered nanoparticles. In order to obtain flame nanoparticles with desired characteristics and with the highest yield, it is necessary to have an in-depth knowledge of their formation process through the reaction system, the flame. It is necessary to delve into the chemical and physical details of the various steps of the mechanism that lead to the final product; pay attention to the inherent characteristics of the particles, such as size distribution, chemical composition, and physical characteristics. Moreover, depending on the final product to be obtained, flames can be modulated and varied in parameters such as temperature, residence time, mixing effect, and the fuel or additive structure. This PhD thesis focuses on studying and characterizing the carbon nanoparticles synthesized in the well-controlled combustion conditions of premixed fuel-rich flame, using a lab-scale reactor constituted by flat laminar ethylene/air premixed flame. The primary purpose of this activity has been to perform an experimental study on flame-formed carbon nanoparticles, with great attention on the still too unclear step of particle formation in flame, i.e. the nucleation. The first year of the PhD was primarily centred on the study and preliminary characterization of physicochemical evolution of flame-formed carbon nanoparticles. In order to produce different sizes of particles, carbon nanoparticles were collected at different distances from the flame front, i.e., the residence time in the flame was changed. Then, various techniques were used to characterize the produced particles. One of the first investigations was performed in the flame by the on-line differential mobility analyzer to study the particle size distribution. Subsequently, the analytical tools continued with ex-situ techniques such as Raman spectroscopy and Electron Paramagnetic Resonance, the former for chemical and structural information on particles modification and the latter to reveal and confirm the presence of radicals and to identify them. In this thesis, great attention was laid on the presence and role of radical species, above all, in the determining step of nucleation. For this reason, the research continued in the second year with a more detailed analysis of radical formation in the flame products mechanism and a more specific structural characterization of carbon nanoparticles. Indeed, a density functional theory study investigated some aspects related to the behaviour of radical molecules in flame in terms of dimerization and formation of cluster structures. Notably, the study was helpful in the differentiation between - and -radicals. Following the theoretical evaluation of the radical molecules, the question was raised about how such radicals could form, i.e., whether specific structural elements could facilitate their formation and, consequently, direct carbon particles' formation through a specific mechanism. This type of structural investigation was performed through the Proton Nuclear Resonance Spectroscopy ,1H-NMR; for the first time used in a system such as the one studied in this thesis work. Then, in the third and final year of this PhD research work, a comparative physicochemical evolution study in an aromatic fuel environment has been performed. The addition of an aromatic dopant, such as benzene, leads to some change in the flame and the particle formation in terms of particles size distribution, Raman features, and especially radical production, allowing to face up the same questions in such environment and to investigate the effect of aromatic fuel on the nature and the role of radicals in particle nucleation and growth

A Spectroscopic Investigation of the Phenalenyl Radical and its Formation

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the interstellar medium (ISM). However, their formation mechanisms and abundances are not well known. Astrochemical models are largely based on high-temperature combustion chemistry models that are unable to correctly explain PAH abundances in the ISM. Hence, alternate formation mechanisms in addition to spectroscopic measurements of PAHs is required. In this thesis, a barrierless formation mechanism for the production of the phenalenyl radical is discovered for the first time in a jet-cooled molecular beam, formed from the electrical discharge of acenaphthylene and methane. This leads to a thorough investigation of the spectroscopic properties of phenalenyl using mass-selective, multi-photon ionization techniques. Results are combined with high-level electronic structure theory that assist in their interpretation. Resonant ionization and isotopic labelling techniques show that the CH cycloaddition mechanism can convert the five-membered ring of acenaphthylene to a six-membered ring. An excitation spectrum for the phenalenyl radical is recorded across an energy range of 18350-35000cm-1, spanning transitions to five different excited states which are ascribed to phenalenyl through three-laser hole-burning spectroscopy. A vibronic Hamiltonian containing Jahn-Teller and \textit{pseudo}-Jahn-Teller coupling gradients between the excited states of the phenalenyl radical is constructed to simulate the observed excitation spectrum at the EOMEE-CCSD level of theory. This allows for additional assignments of the D1 D0 transition, and a complete assignment of the D3 D0 transition, to be made. The ionization energy for phenalenyl is measured to be 6.496(3)~eV in the absence of an electric field through pulsed grid ionization techniques. High-level calculations using the CCSD method are conducted to benchmark the accuracy of several different basis sets in predicting the ionization energy of open-shell PAH radicals based on this experimental value. The excited state lifetimes for the D1, D3 and D4 states are measured as 341 +- 14ns, 172 +- 5ns and 108+-3ns, respectively. The applicability of the CH cycloaddition mechanism to PAH formation is extended to the formation of naphthalene from indene and methane within an electrical discharge using isotopic labelling techniques and a jet-cooled molecular beam. A spectroscopic investigation of the discharge products of an azulene and naphthalene containing molecular beam is also conducted, and the identification of 1- and 2-methylnaphthalene, 1- and 2-naphthylmethyl radicals and phenylcyclopentadiene is achieved

Electronic Spectra of Aromatic Hydrocarbons: A Deductive Approach to the Diffuse Interstellar Bands

The diffuse interstellar bands (DIBs) are a series of more than 500 interstellar absorption features, the carriers of which have remained unidentified since 1919. In order to determine which aromatic chemical species are likely to be carriers of the DIBs, trends observed in the spectroscopic features of polycyclic aromatic hydrocarbon (PAH) species with chromophores ranging from 6 to 17 carbon atoms are considered. These trends are explored for PAHs with differing charge states and multiplicities, for multiple electronic transitions. Previously unreported electronic transitions of the neutral radicals 1-naphthylmethyl, 2-napthylmethyl, 9-methylanthracene and 1-pyrenylmethyl as well as the 9-methylanthracenium+ and phenalenium+ radical cations and the closed-shell neutral molecule 1H-phenalene were recorded. The D1 ← D0 transitions of small PAH resonance stabilized radicals (RSRs) are shown to be unlikely to be responsible for the DIBs. The spectroscopic properties of larger PAH RSRs were empirically extrapolated from experimental and computational trends. The vibronic structures of these molecules were assigned. As the D1 ← D0 transitions of PAH RSRs are weak, techniques were developed to obtain the gas-phase spectra of more intense electronic transitions to higher excited-states by double-resonance spectroscopy. Several strong transitions were observed, which were then assigned using ab-initio and TD-DFT computational methods. The spectra of PAH radical cations were recorded. The recorded spectra covered a range from the mid infrared to the ultraviolet. As a result of the work presented, several classes of PAH can now be dismissed as possible carriers of the DIBs. Further avenues of research have been suggested. The role of this work as part of the ongoing search for the carriers of the DIBs will be discussed

Combustion generated fine carbonaceous particles

Soot is of importance for its contribution to atmospheric particles with their adverse health impacts and for its contributions to heat transfer in furnaces and combustors, to luminosity from candles, and to smoke that hinders escape from buildings during fires and that impacts global warming or cooling. The different chapters of the book adress comprehensively the different aspects from fundamental approaches to applications in technical combustion devices

Role of Microplastics on the Release and Adsorption of Organic Compounds in Natural Waters

Microplastics in the aquatic system are among the many inevitable consequences of plastic pollution, which has cascading environmental and public health impacts. The implications lead to the production of leachate comprised of dissolved organic matter (DOM) and increasing adsorption potential of organic compounds (OCs) onto the microplastic surfaces. In this study, the adsorption potential of organic pollutants and the formation of microplastic leachate from ultraviolet (UV) light were explored. The adsorption potential was created through a summarization and critical review of the literature on the adsorption of synthetic OCs by microplastics in aqueous environments since their emergence in 2008. A database of 92 articles, reporting 178 OCs, was created to provide a reference for our work. Our findings indicated that phenanthrene was the most commonly investigated OC, appearing in 13 of these studies. The adsorption of OCs were compared between the four most prevalent polymer types: polyethylene (PE), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC) using the linear isotherm parameter, KD, to determine adsorption variability and understand the controlling factors for adsorption. ii Surface interactions and leachate production of six microplastics under UV irradiation were determined. Leachate production was analyzed for the dissolved organic content (DOC), UV absorbance (i.e., UV254), and fluorescence through excitation emission (EEM) to determine the amount of leachate produced and the mechanisms involved in leachate production via UV irradiation. The aged microplastic samples were analyzed for Fourier-transform infrared spectroscopy (FT-IR), Raman, and X-ray photoelectron spectroscopy (XPS), to determine the surface changes in combination with leachate formation. The differences in leachate formation for different polymers were attributed to their chemical makeup and their potency to interact with UV. Findings indicated that all microplastics showed evidence of surface oxidation, affirming that the leachate formation is an interfacial interaction and could be a significant source of organic compound influx to natural waters due to the abundance of microplastics and their large surface area. In terms of adsorption of organic compounds by microplastics, it was found that the octanolwater partitioning coefficient, Kow, is an appropriate predictor for adsorption capacity with simply structured polymer types, particularly PE. As hydrophobicity increases, PE adsorbs the most, followed by PVC, and then PP. Comparing the KD to the dipole moments for several different compounds on PE and PS showed that microplastics probably do not have induced electronic interactions, and supported the conclusion that adsorption is most likely driven by a compound’s repulsion from water rather than its affinity for microplastics

INTERACTION OF POLYCYCLIC AROMATIC HYDROCARBONS WITH DISSOLVED AND SEDIMENT ASSOCIATED HUMIC MATERIALS (NMR, FLUORESCENCE)

A fluorescence quenching method was developed for determining association constants of polycyclic aromatic hydrocarbons (PAH)s with dissolved and sediment bound humic materials. The technique is based upon the observation that PAH fluorescence in aqueous solution is quenched upon association with humic material. Association constants are derived from the fractional decrease in fluorescence intensity as a function of added humic material using Stern-Volmer plots. No separation is required and since the technique involves a ratio measurement the exact concentration of pollutant is not required. Anthracene-humic acid association constants normalized to the fraction of organic carbon in the sorbent (K(,oc)), determined by fluorescence quenching, correlated quite well with K(,oc) estimates determined by a reversed-phase procedure. The long term reproducibility was (+OR-)3.8% relative standard deviation. The fluorescence quenching technique was used to investigate the effects of pH, ionic strength, and humic acid composition on pyrene-humic acid K(,oc) values. Carbon, hydrogen, and nitrogen analysis plus UV, infrared, and 13C solid state nuclear magnetic resonance (NMR) spectroscopy were used to investigate compositional and structural variations in humic materials. Three measures of the degree of C=C bond formation (UV absorptivity at 272 nm, atomic H/C ratio, and fraction of aromatic carbon determined by 13C NMR spectroscopy) indicated that pyrene is sorbed preferentially by humic acids possessing a high degree of aromaticity. Solution ionic strength affected K(,oc) estimates in a complex manner. It was hypothesized that humic acid conformational changes and PAH salting out effects accounted for this behavior. Variations in the concentration of stock humic acid solution used in the fluorescence quenching experiments also produced a change in K(,oc) values. Variations in pH from 5 to 8 did not produce significant effects. Measured K(,oc) values were similar for anthracene binding to a purified sediment sample and humic acid extracted from that sediment; however, after partial extraction with dilute base, anthracene sorption to the sediment increased by a factor of two. The residual organic matter after extraction is believed to be enriched in humin and responsible for the increased sorption. In a separate study, determination of PAH in Great Bay sediments by extraction and capillary gas chromatography produced a very good correlation between the total PAH concentration and the organic matter content of the sediments

Anomalous microwave emission from spinning nanodiamonds around stars

Several interstellar environments produce 'anomalous microwave emission' (AME), with brightness peaks at tens-of-gigahertz frequencies. The emission's origins are uncertain -- rapidly spinning nanoparticles could emit electric-dipole radiation, but the polycyclic aromatic hydrocarbons that have been proposed as the carrier are now found not to correlate with Galactic AME signals. The difficulty is in identifying co-spatial sources over long lines of sight. Here we identify AME in three proto-planetary discs. These are the only known systems that host hydrogenated nanodiamonds, in contrast to the very common detection of polycyclic aromatic hydrocarbons. Using spectroscopy, the nanodiamonds are located close to the host stars, at physically well-constrained temperatures. Developing disc models, we reproduce the emission with diamonds 0.75--1.1 nm in radius, holding <= 1-2% of the carbon budget. Ratios of microwave emission to stellar luminosity are approximately constant, allowing nanodiamonds to be ubiquitous but emitting below detection thresholds in many star systems. This result is compatible with the findings with similar-sized diamonds found within Solar System meteorites. As nanodiamond spectral absorption is seen in interstellar sightlines, these particles are also a candidate for generating galaxy-scale AME

Investigating the role of curvature on the formation and thermal transformations of soot

In this work, the role of curved polycyclic aromatic hydrocarbons (cPAH) on the initial formation mechanism and thermal transformations of soot was explored. Experimental and computational techniques were used to probe the integration, presence and impact of internal pentagonal rings on the nucleation mechanism of these particulates. A significant charge polarisation was found to occur when an internal pentagonal ring pyramidalises the aromatic network. Phase contrast transmission electron microscopy allowed for the extent of conjugation and degree of curvature to be determined in early soot nanoparticulates with 15 aromatic rings and two pentagons being the median species. The dipole moment of such a species was calculated to be 5.32 debye. The polarity was found to be persistent at flame temperatures with inversion and fluctuations being minimal. Homogeneous nucleation was considered with homodimerisation energies with one or two internal pentagonal rings within cPAH found to be comparable in energy to flat PAH (fPAH) homodimers of similar weight, with more pentagons reducing the binding energy. Ion-induced nucleation was considered with binding energies calculated between chemi-ions and cPAH suggesting small stable clusters at flame temperatures. However, physical and ion-induced nucleation of cPAH were found to be insufficient alone to explain the formation of soot. The impact of curvature on the reactivity of PAH were then studied. Strong crosslinks between σ-radicals and cPAH were found to form at their rim due to decreased aromaticity. Partially saturated rim-based pentagonal rings were also found to form localised π-radicals that allow stacked and bonded complexes to form, suggesting a covalently stabilised soot nucleation. Finally, the curved geometry of highly annealed soot, otherwise known as non-graphitising carbon, was explored using annealed molecular dynamics simulations and a discrete mesh analysis method. Analysis of the angular defect of the meshes revealed an excess of negative curvature. The coexistence of curved and layered ribbon-like structures was found to be possible due to the presence of a small number of non-sp² defects such as screw dislocations and free edges, which will impact the synthesis of novel carbon materials and the oxidation of thermally annealed soot. The incorporation of curvature and pentagonal rings is therefore considered critical for understanding the properties, formation and destruction of combustion generated carbonaceous particles and other carbon materials.This project is supported by the National Research Foundation (NRF), Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme