Browsing by Subject " chemistry"

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  • Mukherjee, A.B.; Bhattacharya, P. (NRC Research Press, 2001)
  • Xu, Yongjun; Liu, Xin; Cao, Xin; Huang, Changping; Liu, Enke; Qian, Sen; Liu, Xingchen; Wu, Yanjun; Dong, Fengliang; Qiu, Cheng-Wei; Qiu, Junjun; Hua, Keqin; Su, Wentao; Wu, Jian; Xu, Huiyu; Han, Yong; Fu, Chenguang; Yin, Zhigang; Liu, Miao; Roepman, Ronald; Dietmann, Sabine; Virta, Marko; Kengara, Fredrick; Zhang, Ze; Zhang, Lifu; Zhao, Taolan; Dai, Ji; Yang, Jialiang; Lan, Liang; Luo, Ming; Liu, Zhaofeng; An, Tao; Zhang, Bin; He, Xiao; Cong, Shan; Liu, Xiaohong; Zhang, Wei; Lewis, James P.; Tiedje, James M.; Wang, Qi; An, Zhulin; Wang, Fei; Zhang, Libo; Huang, Tao; Lu, Chuan; Cai, Zhipeng; Wang, Fang; Zhang, Jiabao (2021)
    Y Artificial intelligence (AI) coupled with promising machine learning (ML) techniques well known from computer science is broadly affecting many aspects of various fields including science and technology, industry, and even our day-to-day life. The ML techniques have been developed to analyze high-throughput data with a view to obtaining useful insights, categorizing, predicting, and making evidence-based decisions in novel ways, which will promote the growth of novel applications and fuel the sustainable booming of AI. This paper undertakes a comprehensive survey on the development and application of AI in different aspects of fundamental sciences, including information science, mathematics, medical science, materials science, geoscience, life science, physics, and chemistry. The challenges that each discipline of science meets, and the potentials of AI techniques to handle these challenges, are discussed in detail. Moreover, we shed light on new research trends entailing the integration of AI into each scientific discipline. The aim of this paper is to provide a broad research guideline on fundamental sciences with potential infusion of AI, to help motivate researchers to deeply understand the state-of-the-art applications of AI-based fundamental sciences, and thereby to help promote the continuous development of these fundamental sciences.
  • Salmi, Emma (Helsingin yliopisto, 2015)
    Corrosion is a major global challenge with both economical and technological impacts. The total world-wide costs of corrosion have been evaluated to rise to over 2 000 000 million euros annually. While several methods exist for corrosion protection, atomic layer deposited (ALD) coatings have an advantage in applications where thin, fully conformal, highly precise and well-defined coatings both in composition and thickness are needed. In this work the corrosion protection properties of ALD Al2O3 and Ta2O5 based coatings on low alloy steel were studied. The aim was to increase the general understanding on factors affecting the protective properties and failure mechanisms of the ALD coatings. The protective performance of ALD coatings on steel was improved by focusing on three topics: substrate pre-treatment, optimisation of the ALD coating architecture, and combination of the optimised ALD coatings with layers deposited by other methods. The substrate surface was found to significantly influence the ALD coating performance. Improved protective properties were found on steel samples that were mechanically polished to a lower surface roughness, and efficiently cleaned with H2-Ar plasma in addition to the traditional degreasing with an organic solvent. The smoother surface finish was concluded to be beneficial due to decreased defect formation after the coating deposition upon detachment of loose particles or mechanically fragile sites. The H2-Ar plasma removed organic residues from the steel surface, therefore improving the quality of the first layers of the ALD coating. The performance of the ALD coatings themselves was found to improve when Al2O3 and Ta2O5 were combined to produce Al2O3-Ta2O5 nanolaminate and AlxTayOz mixture coatings. In these coatings Al2O3 provided sealing properties and Ta2O5 the chemical stability, therefore resulting in coatings with better long-term performance than could be achieved with either material alone. Optimisation of the Al2O3-Ta2O5 nanolaminate and AlxTayOz mixture coating architectures further enhanced the protective properties. To further improve the coating-steel interface and to widen the application areas for the ALD based protective coatings, the optimised ALD coating processes were combined with layers deposited with other methods. Firstly, thin filtered cathodic arc sublayers were used to separate the ALD process from the steel surface. This enabled a more precise control of the coating-steel interface and led to improved durability of the ALD coatings. Secondly, pinhole defects in physical vapour and plasma-enhanced chemical vapour deposited hard coatings were sealed with ALD to afford coatings with both good corrosion protection performance and resistance against mechanical wear.
  • Blanquart, Timothee (Helsingin yliopisto, 2013)
    The atomic layer deposition process (ALD) is an alternative to the chemical vapour deposition (CVD) method that is universally appreciated for its unique advantages such as excellent repeatability, conformity and thickness control at the atomic level. ALD precursor chemistry has mainly been based on homoleptic compounds such as, but not limited to, metal halides, alkylamides or alkoxides. However, these precursors have drawbacks such as possible halide contamination and low thermal stabilities with respect to the alkylamides and alkoxides. Consequently, heteroleptic precursors were investigated as alternatives to the existing homoleptic counterparts, which have led to the development of several advantageous processes. Nevertheless, no thematic review dedicated to heteroleptic precursor and their properties exists and it seems that no coherent strategy has been adopted for the development of heteroleptic precursors. This thesis gives a brief description of ALD and presents studies on the deposition of thin films of groups 4 and 5 metal oxide films using ALD. A description of the general ALD properties of homoleptic precursors in addition to a review on the thermal ALD of groups 4 and 5 metal oxides from heteroleptic precursors is provided. Trends in the properties of heteroleptic ALD precursors based on a literature review and new experimental data are discussed. Several novel heteroleptic compounds were evaluated for the ALD of thin films of TiO2, ZrO2, Nb2O5 and Ta2O5. The characteristics of these processes were evaluated and the film properties of these oxides were investigated by means of various characterization approaches. The effects of oxygen source, water or ozone, on the film growth characteristics and properties of ZrO2, Nb2O5, and Ta2O5, were also investigated. Mixed alkoxide-alkylamide and alkoxide-amidinate titanium compounds are liquid at room temperature. They are highly volatile, have excellent reactivity towards water and have high thermal stability. The deposited films exhibit high purity and conformability on high aspect ratio substrates. The growth of thin films of ZrO2 from a heteroleptic alkylamide-guanidinate zirconium precursor was notable in that the films grew in the high permittivity cubic phase and the ozone-based process had a high growth rate. Thin films of VOx were deposited from the homoleptic vanadium alkylamide precursor,vanadium tetraethylmethylamide. It was found that the structure and oxidation state of the films could be tuned from an amorphous mixture of VO2 and V2O5 to crystalline VO2 or V2O5. This was accomplished by simply exposing the films to heat treatment in different atmospheres, namely air or N2. Finally, alkylamide-imide precursors were investigated for the ALD of Nb2O5 and Ta2O5 thin films. These precursors are liquid at room temperature, and exhibited high thermal stabilities compared with the earlier known niobium and tantalum ALD precursors. The alkylamide-imide precursors studied had high volatility and excellent reactivity towards both water and ozone. The deposited films were smooth, uniform, and contained only low amounts of impurities.
  • Otaru, Sofia (Helsingin yliopisto, 2022)
    Pathologies that require non-invasive, quantitative, and repeated investigation for treatment follow-up and for patient selection are on the rise due to longer life-expectancy and lifestyle changes. Early treatment and accurate diagnosis are required for curative intervention. Positron emission tomography (PET) offers a non-invasive and quantitative imaging modality for investigating biological processes, namely metabolism and receptor expression in tissues. To achieve the requirements of selectivity and sensitivity, various radiotracers need to be designed, synthesized and evaluated. Anything from small molecules to nanoparticles and biomacromolecules, are utilized as tracers, depending on the imaging target and the kinetics of the process under investigation. Several tumors over-express on their surface receptors that can be targeted with biomolecules, such as peptides, extremely selectively. Peptides have specific amino acid sequences that interact with the binding site in the receptor, requiring careful design of the radiolabeling modifications in order not to disturb the interaction. Consequently, chemoselective radiolabeling methods are becoming more prevalent in the synthesis of biomolecular radiotracers. Given the high cost of radiopharmaceutical development, the availability of multipurpose, late-stage radiolabeling tools offering rapid radiotracer production from diverse target molecules would lower the development costs and provide wider selection of biological radiotracers for imaging studies. The aim of this work was to develop fluorine-18-labeled tetrazines for preparing biological radiotracers for PET imaging. The novel tetrazines were studied for their metabolic stability and biological performance and used for in vitro radiolabeling of the target biomolecules. Heat sensitive serum albumin protein, and cyclic receptor targeting peptides, were radiolabeled with fast click reactions of the tetrazines providing chemoselective and mild radiofluorination. The first candidate tetrazine, fluorine-18 labeled silicon-fluoride acceptor tetrazine ([18F]SiFA-Tz) with a lipophilic prosthetic group, was found to be metabolically unstable and was further studied for its in vitro metabolism pathway in mouse liver microsomes with ultra-high performance liquid chromatography (UHPLC) high-resolution mass spectrometry (HRMS). Structural optimization was done and a metabolically stable and more hydrophilic fluorine-18 labeled alkylammoniomethyltrifluoroborate tetrazine ([18F]AmBF3-Tz) was developed, and evaluated with in vivo PET-computed tomography (PET/CT) imaging and ex vivo biodistribution studies where it demonstrated excellent stability. [18F]AmBF3-Tz is currently under further investigation for in vivo pretargeted PET imaging, due to the highly promising biological behavior as a standalone radiotracer. [18F]AmBF3-Tz was subsequently used as a radiofluorination reagent for somatostatin receptor-2 (SSTR2) targeting peptides. The lead peptide tracer was used for PET/CT imaging of preclinical pancreatic carcinoma model, providing clear visualization of the tumor xenografts. The findings presented in this study demonstrate the successful development of a novel radiolabeling tool to produce new biomolecular radiotracers for PET imaging.
  • Sibaouih, Ahlam (Helsingin yliopisto, 2015)
    Catalytic transformation of carbon dioxide into useful organic compounds has attracted much attention due to its economic and environmental benefits. In addition, other reasons are also taken into account, such as the possible utilization of CO2 as a renewable source chemical and the growing concern of the greenhouse effect. CO2 is an abundant, cheap, and safe C1 building block in organic synthesis. However, due to the inert nature of CO2, efficient catalytic processes of its chemical fixation remain a significant challenge. In this work, we have studied a possible pathway for practical utilization of CO2. The reaction of CO2 with epoxides giving cyclic carbonates, has been investigated. New catalyst systems based on cobalt capable of catalyzing the chemical transformation of carbon dioxide are described in detail. Oxygen is a cheap, readily available and environmentally friendly natural oxidant. The catalytic activation of molecular oxygen has great potential in a variety of applications. Catalysis and reactions, which are based on molecular oxygen, can also be considered to be ecologically benign processes. Moreover, catalytic reactions in water are highly desirable in terms of green chemistry. In this context, our purpose was to develop an environmentally friendly catalytic systems, suitable for oxidation of alcohols with molecular oxygen in water solution. In this part of the work, efficient catalysts, based on copper complexes have been synthesized and studied in the presence of TEMPO for the oxidation of benzyl and aliphatic alcohols with molecular oxygen in aqueous and nonaqueous medium.
  • Zhang, Rui (Helsingin yliopisto, 2022)
    Utilizing renewable lignocellulosic biomass as a feedstock is a promising alternative to raw oil for the synthesis of value-added chemicals and materials. The development of efficient catalytic transformation routes is greatly needed to enhance the existing contemporary biorefinery concepts. The literature review of this thesis provides a general perspective about lignin modification (e.g. fractionation) and utilization methods (e.g. oxidation). The retro-aldol condensation (RAC) of carbohydrates is discussed, where the resulting glycolaldehyde (GA) as an important and versatile intermediate for synthetic chemistry is addressed. An in-depth discussion about the catalytic RAC combined with hydrogenation, oxidation, reductive amination, and aldol reaction for fine chemicals production is presented. Additionally, the Garcia Gonzalez (GG) reaction of carbohydrates with β-dicarbonyl compounds to form furan-based compounds, polyhydroxyalkyl furans (PF) and C-glycosylfurans (GF), is reviewed. This thesis aims to explore new and efficient catalytic methods to produce vanillin from Kraft lignin (KL); and to produce alternative furanic compounds other than 5-(hydroxymethyl)furfural (HMF) and furfural from glucose and xylose, developing upon RAC and GG reactions. The results and discussion part presents the central findings from the author’s work. The first part describes a facile procedure for high yield vanillin synthesis via fractionation combined with oxidation methods. The second part presents a mild temperature H2MoO4-catalyzed conversion of glucose to furanic chemicals, where the in-situ generated GA and erythrose from [C2 + C4] RAC reacted with acetylacetone (acac) to yield the desired products. The third section focuses on the development of an efficient ZrCl4-catalyzed conversion of xylose with acac to new types of furanic compounds, with excellent yields and carbon efficiency.
  • Benkyi, Isaac (Helsingin yliopisto, 2022)
    Expanded porphyrins, porphyrinoids, porphycenes and N-doped nanographenes are multi- ring molecules whose aromaticity cannot be easily predicted based on NMR chemical shifts. The magnetically induced current-density susceptibility and the ring-current path- ways have been elucidated for these molecules at ab initio and density functional theory (DFT) levels using the gauge-including magnetically induced current (GIMIC) method. Calculations showed that the lowest electronic transition of the antiaromatic molecules are purely magnetic transitions which is also the main reason why these molecules sustain large net paratropic ring currents. The photophysical properties of expanded porphyrins, acenes and pyrene have also been studied using quantum mechanical methods. The absorption spectrum including vibrational bands of the acenes and pyrene were simulated and compared with those obtained in high-resolution measurements of the absorption spectra in the visible range. The vibra- tional contributions to the absorption spectra were obtained by using a time-generating function approach, which is computationally faster than alternative approaches. The 0-0 transition energies of acenes and pyrene are reported. Various vibrational modes contributing to the vibrational fine structure of these molecules have been identified. The quantum yield of luminescence was determined for the expanded porphyrins by calculating rate constants for radiative and non-radiative transitions between excited electronic states and the ground state
  • Lagerspets, Emi (Helsingin yliopisto, 2022)
    The selective aerobic oxidation of alcohols to their corresponding aldehydes has been the focus of research in the field of organometallic catalysis. This is due to the fact that the conditions used in this field have stoichiometric amounts of hazardous heavy metal catalysts. Recently, the focus has been on the development of environmentally friendly and safe catalysts, which utilize oxygen out of the air and produce only water as a by-product. Copper has been the focus of the newly developed catalysts in combination with nitroxyl radicals and co-catalysts. These catalysts work under mild conditions and show a high reactivity towards the aerobic oxidation of alcohols to aldehydes. In this thesis, first, a literature overview over the oxidation of alcohols to their corresponding carbonyl compounds with primarily copper-based catalysts is given. In the experimental section, new selective and environmentally friendly methods for the selective oxidation of primary alcohols to aldehydes under ambient conditions were developed using copper(I)/copper(II) catalysts with co-catalysts. Especially the use of new ligands was the focus of this thesis and new highly active copper(I)-Schiff base complexes and copper(I)-2,2'-dipyridylamine complexes were developed. These copper-based catalysts showed a high activity towards the selective oxidation of primary alcohols and various diols. Their catalytic activity was characterized using UV-vis, in situ IR, X-ray structure determination and ESI-MS.
  • Joshi, Satya Prakash (Helsingin yliopisto, 2021)
    Combustion of practical fuels proceeds via an extremely large number of elementary reactions, which makes it difficult to model their combustion chemistry. To resolve this problem, combustion chemistry of a practical fuel can be emulated with a small set of surrogate fuels that involves a much more limited number of elementary reactions. In this work, the kinetics of various unsaturated radical reactions have been studied, which are central to the combustion of important surrogate fuels such as propene, 2-methyl-2-butene (2M2B) and methyl-crotonate (MC). Apart from investigating the reaction kinetics on a fundamental level, the practical application of this work is to provide rate coefficients data over a wide range of conditions, which is expected to significantly improve the accuracy of the current combustion models. As the reactions studied in this work are an integral part of the detailed reaction schemes utilized for modeling the combustion of practical fuels. The kinetic experiments presented in this work were conducted using laser photolysis–photoionization mass spectrometer (LP–PIMS) apparatus. Whenever required, the results of LP-PIMS experiments were further supported and extrapolated to the combustion conditions using quantum-chemistry calculations and master equation (ME) modeling. Kinetics of the CH3CCH2 + O2, cis/trans-CH3CHCH + O2, (CH3)2CCH + O2 and (CH3)2CCCH3 + O2 reactions were measured over a wide temperature range (220 – 660 K) and at low pressures (0.3 – 2 Torr). These vinyl-type radicals are derivatives of methyl-group substitution to the α- and/or β-hydrogens of the vinyl radical (C2H3). The main goal of this study was to quantify the effects of the CH3-group substitutions on the kinetics and reactivity of vinyl-type radicals towards O2. Comparing the measured bimolecular rate-coefficients for the aforementioned vinyl-type radical + O2 reactions reveals that the CH3-group substitution to the α- and β-positions of the C2H3 radical has an increasing (~50%) and decreasing (~30%) effect on its reactivity towards O2, respectively. The CH2CHCHC(O)OCH3 radical having a highly resonance-stabilized structure, the reactivity of the CH2CHCHC(O)OCH3 + O2 reaction is expected to be slow. A very low upper-limit (k ≤ 7.5 × 10-17 cm3 molecule-1 s-1) for the bimolecular rate-coefficient of the CH2CHCHC(O)OCH3 + O2 reaction was measured at 600 K. Following this, thermal unimolecular decomposition kinetics of the CH2CHCHC(O)OCH3 radical was studied over the temperature range of 750 – 869 K and at low pressures (< 9 Torr). Subsequently, the measured thermal unimolecular decomposition rate-coefficients were modeled using ME. The kinetics of the reaction between the resonance-stabilized (CH3)2CCHCH2 radical and O2 was studied over the temperature range of 238 – 660 K and at low pressures (0.2 – 5.7 Torr). The most important observation of this study was the opening of high temperature reaction channels at temperatures above 500 K. A thorough single- and multi-reference quantum-chemistry calculations and ME modeling study were performed to corroborate the experimental findings. Importantly, the observed high temperature (T > 500 K) kinetics of the (CH3)2CCHCH2 + O2 reaction is significantly faster than is currently incorporated in the combustion models.
  • Bettencourt da Silva, Ricardo J.N; Saame, Jaan; Anes, Bárbara; Heering, Agnes; Leito, Ivo; Näykki, Teemu; Stoica, Daniela; Deleebeeck, Lisa; Bastkowski, Frank; Snedden, Alan; Camões, M. Filomena (Elsevier, 2021)
    Analytica Chimica Acta 1182 (2021), 338923
    The use of the unified pH concept, pHabsH2O, applicable to aqueous and non-aqueous solutions, which allows interpreting and comparison of the acidity of different types of solutions, requires reliable and objective determination. The pHabsH2O can be determined by a single differential potentiometry measurement referenced to an aqueous reference buffer or by a ladder of differential potentiometric measurements that allows minimisation of inconsistencies of various determinations. This work describes and assesses bottom-up evaluations of the uncertainty of these measurements, where uncertainty components are combined by the Monte Carlo Method (MCM) or Taylor Series Approximation (TSM). The MCM allows a detailed simulation of the measurements, including an iterative process involving in minimising ladder deviations. On the other hand, the TSM requires the approximate determination of minimisation uncertainty. The uncertainty evaluation was successfully applied to measuring aqueous buffers with pH of 2.00, 4.00, 7.00, and 10.00, with a standard uncertainty of 0.01. The reference and estimated values from both approaches are metrologically compatible for a 95% confidence level even when a negligible contribution of liquid junction potential uncertainty is assumed. The MCM estimated pH values with an expanded uncertainty, for the 95% confidence level, between 0.26 and 0.51, depending on the pH value and ladder inconsistencies. The minimisation uncertainty is negligible or responsible for up to 87% of the measurement uncertainty. The TSM quantified measurement uncertainties on average only 0.05 units larger than the MCM estimated ones. Additional experimental tests should be performed to test these uncertainty models for analysis performed in other laboratories and on non-aqueous solutions.
  • Mustonen, Joonas Aleksi; Tommiska, Oskari Mikael; Holmström, Axi; Rauhala, Timo; Moilanen, Petro; Gritsevich, M.; Salmi, Ari; Haeggström, Edward (2021)
    Pipe fouling is a challenging problem in many industrial applications. Current cleaning techniques require halting the production during the cleaning phase and the existing methods are unable to do targeted cleaning, even though fouling is often localized to certain areas inside the pipeline. To address this issue, we use FEM-simulated, time-reversed signals to focus ultrasound power onto a pre-determined location: a fouled pipe residing inside a Plexiglas container. Ultrasound cleaning with similar acoustic power was compared to the time-reversal enhanced method in terms of cleaning efficiency. The cleaning efficiency was determined by measuring how much fouling, by mass, both protocols removed from the surface of a Plexiglas pipe, using similar input electric power and equal cleaning time. Our results indicate that the proposed time-reversal-based technique removes three times more fouling than the standard ultrasound cleaning without focusing. The study extends our previous paper on FEM-based time-reversal focusing [1].
  • Wymore, Adam S.; Johnes, Penny J.; Bernal, Susana; Brookshire, E. N. Jack; Fazekas, Hannah M.; Helton, Ashley M.; Argerich, Alba; Barnes, Rebecca T.; Coble, Ashley A.; Dodds, Walter K.; Haq, Shahan; Johnson, Sherri L.; Jones, Jeremy B.; Kaushal, Sujay S.; Kortelainen, Pirkko; López-Lloreda, Carla; Rodríguez-Cardona, Bianca M.; Spencer, Robert G. M.; Sullivan, Pamela L.; Yates, Christopher A.; McDowell, William H. (American Geophysical Union, 2021)
    Global Biogeochemical Cycles, 35(8), e2021GB006953
    A comprehensive cross-biome assessment of major nitrogen (N) species that includes dissolved organic N (DON) is central to understanding interactions between inorganic nutrients and organic matter in running waters. Here, we synthesize stream water N chemistry across biomes and find that the composition of the dissolved N pool shifts from highly heterogeneous to primarily comprised of inorganic N, in tandem with dissolved organic matter (DOM) becoming more N-rich, in response to nutrient enrichment from human disturbances. We identify two critical thresholds of total dissolved N (TDN) concentrations where the proportions of organic and inorganic N shift. With low TDN concentrations (0–1.3 mg/L N), the dominant form of N is highly variable, and DON ranges from 0% to 100% of TDN. At TDN concentrations above 2.8 mg/L, inorganic N dominates the N pool and DON rarely exceeds 25% of TDN. This transition to inorganic N dominance coincides with a shift in the stoichiometry of the DOM pool, where DOM becomes progressively enriched in N and DON concentrations are less tightly associated with concentrations of dissolved organic carbon (DOC). This shift in DOM stoichiometry (defined as DOC:DON ratios) suggests that fundamental changes in the biogeochemical cycles of C and N in freshwater ecosystems are occurring across the globe as human activity alters inorganic N and DOM sources and availability. Alterations to DOM stoichiometry are likely to have important implications for both the fate of DOM and its role as a source of N as it is transported downstream to the coastal ocean.
  • Holding, Ashley John (Helsingin yliopisto, 2016)
    In this thesis, the synthesis and application of tetraalkylphosphonium-based ionic liquids towards the dissolution of cellulose (and lignocellulose) is explored. Ionic liquids were synthesised from trialkylphosphines by quaternisation with alkyl halides or dimethylcarbonate and subsequent anion exchange reactions. The ionic liquids were used to dissolve lignin, and were found only to dissolve cellulose upon addition of a polar aprotic molecular solvent, such as DMSO (dimethylsulfoxide). The cellulose dissolution capabilities of a range of these phosphonium ionic liquids in combination with DMSO was studied. It was found that these organic electrolyte solutions were very effective solvents for cellulose, with a high molar dissolution capacity. At the greatest extent, only one mole of ionic liquid per glucose units in cellulose is needed to dissolve cellulose. The role of the cation and anion in the dissolution process is explored, with the aid of solvent parametisation techniques and NMR studies. Other solvents, including GVL (gamma-valerolactone), were explored as greener replacements for DMSO. For the shorter chain phosphonium ionic liquids with DMSO and GVL, upper critical solution temperature behaviour was observed and explored in more detail. In these solutions, cellulose is only soluble at high temperatures, and reforms at low temperatures to form a gel with a spherical micro-particle morphology. The phase behaviour of hydrophobic phosphonium ionic liquids, DMSO, and water was studied and applied to the recovery of the ionic liquid after cellulose dissolution in the electrolyte solutions. Ternary phase diagrams of three of the hydrophobic ionic liquids in combination with DMSO and water were constructed. Finally, phosphonium ionic liquid and deuterated DMSO electrolytes were studied and successfully used for the NMR analysis of high molecular weight cellulose materials. Future work in this area is expected to focus further on the theoretical understanding of cellulose dissolution in phosphonium ionic liquid-based organic electrolyte solutions - with expanded NMR measurements, and other experimental techniques, in tandem with molecular dynamics modelling. Additionally, it is expected that techniques for the solution-state NMR of cellulose will be applied at extended range of analytes, including but not limited to, whole biomass, modified and unmodified nano-celluloses, and high molecular weight cellulose derivatives. The thermo-responsive behaviour (UCST-type) phase-separation of cellulose will continue to be explored especially in its application to new materials, included fibres and shaped spherical particles.
  • Rico del Cerro, Daniel (Helsingin yliopisto, 2021)
    The overall aim of this thesis is to understand the chemistry of different types of ionic liquids (ILs) and their application in cellulose processing, as well as in the chemical analyses of pulp. ILs are applied either on their own or as electrolytes with dimethyl sulfoxide (DMSO) or gamma valerolactone (GVL) as co-solvents. All of the ILs utilised in this work were synthesised in our laboratory via Menshutkin reaction followed by metathesis to different counter anions or via acid-base chemistry. The beginning of our work focused on the investigation of the C2 chemistry of imidazolium ionic liquids (IMILs), one of the first class of ionic liquids utilised in biomass processing, resulting in the understanding of the C2 chemistry of IMILs under neutral and acidic conditions, which complete the comprehension on the mechanistic scenario of the C2 chemistry of IMILs. In this investigation, the importance of the quality of the ILs is remarked. The studies continued to investigate the activation of the chemical reactivity of pulps using tetrabutylphosphonium acetate ([P4444][OAc]), a more thermal stable ionic liquid. The non-dissolving pre-treatment of pulps by [P4444][OAc] demonstrated a reduction in the crystallinity of the pulp to be directly related to its chemical reactivity enhancement. Additionally, [P4444][OAc]:d6-DMSO (20:80 wt.%) was also investigated in both the regioselectivity studies of acetylation reactions and the oxidised nanocellulose nuclear magnetic resonance (NMR) analyses. Quantitative heteronuclear single quantum correlation (HSQC) NMR was a suitable experiment for the quantitation of the oxidation level achieved in the nanocellulose, demonstrating the potential of this method for cellulose analyses. Finally, the research concluded with the studies on other cellulose solvent systems, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with dimethylsulphoxide (DMSO), which resulted on the discovery of the unexpected reactivity of 1,1,3,3-tetramethylguanidinium acetate ([TMG][OAc]). Furthermore, this investigation led us to the design and synthesis of a novel task-specific ionic liquid (TSIL), so called ‘TMG2SA’. This IL was investigated with regard to cellulose chemical modification, resulting in the high yield production of nanocellulose-type materials by a low demanding energy step, with a different approach than previously reported.
  • Muha, Villo; Williamson, Ritchie; Hills, Rachel; McNeilly, A.D.; McWilliams, T.G.; Alonso, Jana; Schimpl, Marianne; Leney, Aneika C.; Heck, Albert J.R.; Sutherland, Calum; Read, Kevin D.; McCrimmon, Rory J.; Brooks, S.P.; Van Aalten, Daan M.F. (2019)
    O-GlcNAcylation is an abundant post-translational modification in the nervous system, linked to both neurodevelopmental and neurodegenerative disease. However, the mechanistic links between these phenotypes and site-specific O-GlcNAcylation remain largely unexplored. Here, we show that Ser517 O-GlcNAcylation of the microtubule-binding protein Collapsin Response Mediator Protein-2 (CRMP2) increases with age. By generating and characterizing a Crmp2S517A knock-in mouse model, we demonstrate that loss of O-GlcNAcylation leads to a small decrease in body weight and mild memory impairment, suggesting that Ser517 O-GlcNAcylation has a small but detectable impact on mouse physiology and cognitive function. © 2019 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License, which permits unrestricted use, provided the original author and source are credited.
  • Iashin, Vladimir (2020)
    C-H activation is a challenging problem in modern organic chemistry. Direct C–H borylation is one of the widely growing subclasses of C–H activation. As a rule, these reactions are performed by transition metal catalysis. However, recently a metal-free approach towards C-B boron bond formation has been growing intensively. Usually, metal-free borylations are performed with a boron compound as a Lewis acid component and a Lewis base as a proton acceptor, which may or may not be preorganized for this transformation. Usually, such reactions require the use of boranes with high Lewis acidity such as B(C6F5)3, BCl3, BBr3, etc. At the same time, the chemistry of the less acidic boron trifluoride, BF3, as a borylating species is unprecedented. This work is aimed at uncovering the reactivity of BF3 towards C-H borylation of Csp–H and Csp2–H bonds. In this respect, the following factors were studied in the work: • Formation of BF3 adducts with various amines and their reactivity in Csp2–H and Csp–H borylation reactions • Scope of borylation: influence of the substrates’ electronic structure and various functional groups’ compatibility • Controlling the formation of mono-, bis-, tris-, and tetrakisorganoborates from BF3, amine, and Rsp–H/Rsp2–H substrate. • Reactivity difference between BF3·SMe2, BF3·OEt2, and BF3-1,2,2,6,6-pentamethylpiperidine (BF3·PMP) with respect to alkyne borylation Because organoboranes are often unstable reactive species, they were converted to fluoroborates by tetramethylammonium fluoride. In this respect, competing reactions of protodeborylation and fluorination of organofluoroboranes were studied. The literature review consists of two parts: metal-free borylation of triple bonds and double bonds. For triple bonds, the review is preferably limited to terminal acetylenes because internal alkynes cannot undergo Csp–H activation. The influence of each component of a Lewis pair as well as its structure’s selectivity for C–H borylation, 1,2-addition, and carboboration is discussed. The second part uncovers the topic of C-H borylation of Csp2–H bonds. It includes both concerted borylations and borylations by reactive borenium cations. There is a special accent on the chemistry of haloboranes. In order to limit the size of the review, the use of hydroboranes for C–H activation is reviewed least in this book.
  • Vesterinen, Veli-Matti (Helsingin yliopisto, 2012)
    Nature of science (NOS) describes what science is, how it works, how scientists operate, and the interaction between science and society. As a crucial element of scientific literacy, knowledge about NOS is widely recognized as one of the key aims of chemistry education. To enhance students understanding of NOS, teachers need adequate understanding of NOS as well as sufficient pedagogical content knowledge related to NOS for translating their understanding of NOS into classroom practice. This thesis reports an educational design research project on the design and development of a pre-service chemistry teacher education course on NOS instruction. Educational design research is the systematic study of the design and development of educational interventions for addressing complex educational problems. It advances the knowledge about the characteristics of designed interventions and the processes of design and development. The thesis consists of four interconnected studies and documents two iterative design research cycles of problem analysis, design, implementation, and evaluation. The first two studies describe how NOS is presented in the national frame curricula and upper secondary school chemistry textbooks. These studies provide a quantitative method for analysis of representations of NOS in chemistry textbooks and curricula, as well as describe the components of domain-specific NOS for chemistry education. The other two studies document the design, development, and evaluation of the goals and instructional practices used on the course. Four design solutions were produced: (i) description of central dimensions of domain-specific NOS for chemistry education, (ii) research group visits to prevent the diluting of relevance to science content and research, (iii) a teaching cycle for explicit and structured opportunities for reflection and discussion, and (iv) collaborative design assignments for translating NOS understanding into classroom practice. The evaluations of the practicality and effectiveness of the design solutions are based on the reflective essays and interviews of the pre-service teachers, which were collected during the course, as well as on the four in-depth interviews of selected participants, collected a year after they had graduated as qualified teachers. The results suggest that one critical factor influencing pre-service chemistry teachers commitment to teach NOS was the possibility to implement NOS instruction during the course. Thus, the use of collaborative peer teaching and integrating student teaching on NOS instruction courses is suggested as a strategy to support the development of the attitudes, beliefs, and skills necessary for teaching NOS. And even though the outside forces of school culture (e.g. school community, curriculum, textbooks) tend to constrain rather than support novice teachers efforts to implement new practices, the results also demonstrate that a pre-service teacher education course can be successful in producing innovators or early adopters of NOS instruction. Thus it might be one of the first steps in the challenging task of injecting NOS instruction into the chemistry curriculum for enhancing students understanding of NOS and strengthening their scientific literacy.
  • Losilla Fernández, Sergio A (Helsingin yliopisto, 2013)
    In this thesis, several numerical methods for electronic structure calculations are presented. The first is a quadrature scheme for the accurate and efficient computation of electrostatic potentials. The quadrature is applied to calculations on real-space grids, and to Coulomb integrals over Gaussian-type orbitals. Second, we introduce a real-space representation for three-dimensional scalar functions encountered in electronic structure calculations. In this representation, each function is partitioned into numerical atom-centred parts (the bubbles), and the remainder is represented on a three-dimensional Cartesian grid. The algorithms to carry out the required operations are discussed, along with benchmarks of their computer implementations. The presented methods are all of a divide-and-conquer nature, breaking the problem into simple pieces which are suitable for execution in emerging massively parallel computer architectures, such as general-purpose graphics processing units.
  • Asmi, Eija; Neitola, Kimmo; Teinila, Kimmo; Rodriguez, Edith; Virkkula, Aki; Backman, John; Bloss, Matthew; Jokela, Jesse; Lihavainen, Heikki; De Leeuw, Gerrit; Paatero, Jussi; Aaltonen, Veijo; Mei, Miguel; Gambarte, Gonzalo; Copes, Gustavo; Albertini, Marco; Perez Fogwill, German; Ferrara, Jonathan; Elena Barlasina, Maria; Sanchez, Ricardo (2018)
    Aerosol particle optical properties were measured continuously between years 2013-2015 at the Marambio station in the Antarctic Peninsula. Annual cycles of particle scattering and absorption were studied and explained using measured particle chemical composition and the analysis of air mass transport patterns. The particle scattering was found elevated during the winter but the absorption did not show any clear annual cycle. The aerosol single scattering albedo at lambda = 637 nm was on average 0.96 +/- 0.10, with a median of 0.99. Aerosol scattering Angstrom exponent increased during summer, indicating an increasing fraction of fine mode particles. The aerosol was mainly composed of sea salt, sulphate and crustal soil minerals, and most of the particle mass were in the coarse mode. Both the particle absorption and scattering were increased during high wind speeds. This was explained by the dominance of the primary marine sea-spray and wind-blown soil dust sources. In contrast, the back-trajectory analysis suggested that long-range transport has only a minor role as a source of absorbing aerosol at the peninsula.