107 results on '"Ivo Heinmaa"'
Search Results
2. Small organic molecules containing amorphous calcium phosphate: synthesis, characterization and transformation
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Abhishek Indurkar, Pawan Kudale, Vitālijs Rjabovs, Ivo Heinmaa, Öznur Demir, Matvejs Kirejevs, Kristaps Rubenis, Ganesh Chaturbhuj, Māris Turks, and Janis Locs
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amorphous calcium phosphate ,organic compounds ,ascorbate ,itaconate ,glutamate ,biomaterials ,Biotechnology ,TP248.13-248.65 - Abstract
As the primary solid phase, amorphous calcium phosphate (ACP) is a pivotal precursor in cellular biomineralization. The intrinsic interplay between ACP and Howard factor underscores the significance of understanding their association for advancing biomimetic ACP development. While organic compounds play established roles in biomineralization, this study presents the synthesis of ACP with naturally occurring organic compounds (ascorbate, glutamate, and itaconate) ubiquitously found in mitochondria and vital for bone remodeling and healing. The developed ACP with organic compounds was meticulously characterized using XRD, FTIR, and solid-state 13C and 31P NMR. The morphological analysis revealed the characteristic spherical morphology with particle size close to 20 nm of all synthesized ACP variants. Notably, the type of organic compound strongly influences true density, specific surface area, particle size, and transformation. The in vitro analysis was performed with MC3T3-E1 cells, indicating the highest cell viability with ACP_ASC (ascorbate), followed by ACP_ITA (itaconate). The lowest cell viability was observed with 10 %w/v of ACP_GLU (glutamate); however, 1 %w/v of ACP_GLU was cytocompatible. Further, the effect of small organic molecules on the transformation of ACP to low crystalline apatite (Ap) was examined in Milli-Q® water, PBS, and α-MEM.
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- 2024
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3. Development and Characterisation of Composites Prepared from PHBV Compounded with Organic Waste Reinforcements, and Their Soil Biodegradation
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Valentin Furgier, Andrew Root, Ivo Heinmaa, Akram Zamani, and Dan Åkesson
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PHBV ,biocomposite ,biodegradation ,sawdust ,hair waste ,chitin ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biobased and biodegradable polymer. This polymer is considered promising, but it is also rather expensive. The objective of this study was to compound PHBV with three different organic fillers considered waste: human hair waste (HHW), sawdust (SD) and chitin from shrimp shells. Thus, the cost of the biopolymer is reduced, and, at the same time, waste materials are valorised into something useful. The composites prepared were characterised by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile strength and scanning electron micrograph (SEM). Tests showed that chitin and HHW did not have a reinforcing effect on tensile strength while the SD increased the tensile strength at break to a certain degree. The biodegradation of the different composites was evaluated by a soil burial test for five months. The gravimetric test showed that neat PHBV was moderately degraded (about 5% weight loss) while reinforcing the polymer with organic waste clearly improved the biodegradation. The strongest biodegradation was achieved when the biopolymer was compounded with HHW (35% weight loss). The strong biodegradation of HHW was further demonstrated by characterisation by Fourier-transform infrared spectroscopy (FTIR) and solid-state nuclear magnetic resonance (NMR). Characterisation by SEM showed that the surfaces of the biodegraded samples were eroded.
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- 2024
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4. Application of Immersed Membrane Bioreactor for Semi-Continuous Production of Polyhydroxyalkanoates from Organic Waste-Based Volatile Fatty Acids
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Danh H. Vu, Amir Mahboubi, Andrew Root, Ivo Heinmaa, Mohammad J. Taherzadeh, and Dan Åkesson
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biopolymer ,immersed membrane reactor ,polyhydroxyalkanoates ,volatile fatty acids ,Chemical technology ,TP1-1185 ,Chemical engineering ,TP155-156 - Abstract
Volatile fatty acids (VFAs) appear to be an economical carbon feedstock for the cost-effective production of polyhydroxyalkanoates (PHAs). The use of VFAs, however, could impose a drawback of substrate inhibition at high concentrations, resulting in low microbial PHA productivity in batch cultivations. In this regard, retaining high cell density using immersed membrane bioreactor (iMBR) in a (semi-) continuous process could enhance production yields. In this study, an iMBR with a flat-sheet membrane was applied for semi-continuous cultivation and recovery of Cupriavidus necator in a bench-scale bioreactor using VFAs as the sole carbon source. The cultivation was prolonged up to 128 h under an interval feed of 5 g/L VFAs at a dilution rate of 0.15 (d−1), yielding a maximum biomass and PHA production of 6.6 and 2.8 g/L, respectively. Potato liquor and apple pomace-based VFAs with a total concentration of 8.8 g/L were also successfully used in the iMBR, rendering the highest PHA content of 1.3 g/L after 128 h of cultivation. The PHAs obtained from both synthetic and real VFA effluents were affirmed to be poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a crystallinity degree of 23.8 and 9.6%, respectively. The application of iMBR could open an opportunity for semi-continuous production of PHA, increasing the feasibility of upscaling PHA production using waste-based VFAs.
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- 2023
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5. Cyclohexanohemicucurbit[8]uril Inclusion Complexes With Heterocycles and Selective Extraction of Sulfur Compounds From Water
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Tatsiana Shalima, Kamini A. Mishra, Sandra Kaabel, Lukas Ustrnul, Simona Bartkova, Kaia Tõnsuaadu, Ivo Heinmaa, and Riina Aav
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Hemicucurbituril ,solid-phase extraction ,heterocycles ,inclusion complex ,lipoic acid ,sorbent recycling ,Chemistry ,QD1-999 - Abstract
Solid-phase extraction that utilizes selective macrocyclic receptors can serve as a useful tool for removal of chemical wastes. Hemicucurbiturils are known to form inclusion complexes with suitably sized anions; however, their use in selective binding of non-charged species is still very limited. In this study, we found that cyclohexanohemicucurbit[8]uril encapsulates five- and six-membered sulfur- and oxygen-containing unsubstituted heterocycles, which is investigated by single-crystal X-ray diffraction, NMR spectroscopy, isothermal titration calorimetry, and thermogravimetry. The macrocycle acts as a promising selective sorption material for the extraction of sulfur heterocycles, such as 1,3-dithiolane and α-lipoic acid, from water.
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- 2021
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6. Thorough Investigation of the Effects of Cultivation Factors on Polyhydroalkanoates (PHAs) Production by Cupriavidus necator from Food Waste-Derived Volatile Fatty Acids
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Danh H. Vu, Amir Mahboubi, Andrew Root, Ivo Heinmaa, Mohammad J. Taherzadeh, and Dan Åkesson
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biopolymer ,polyhydroalkanoates ,volatile fatty acids ,food waste ,acidogenic fermentation ,Fermentation industries. Beverages. Alcohol ,TP500-660 - Abstract
Volatile fatty acids (VFAs) have become promising candidates for replacing the conventional expensive carbon sources used to produce polyhydroxyalkanoates (PHAs). Considering the inhibitory effect of VFAs at high concentrations and the influence of VFA mixture composition on bacterial growth and PHA production, a thorough investigation of different cultivation parameters such as VFA concentrations and composition (synthetic and waste-derived VFAs) media, pH, aeration, C/N ratio, and type of nitrogen sources was conducted. Besides common VFAs of acetic, butyric and propionic acids, Cupriavidus necator showed good capability for assimilating longer-chained carboxylate compounds of valeric, isovaleric, isobutyric and caproic acids in feasible concentrations of 2.5–5 g/L. A combination of pH control at 7.0, C/N of 6, and aeration of 1 vvm was found to be the optimal condition for the bacterial growth, yielding a maximum PHA accumulation and PHA yield on biomass of 1.5 g/L and 56%, respectively, regardless of the nitrogen sources. The accumulated PHA was found to be poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with the percentage of hydroxybutyrate in the range 91–96%. Any limitation in the cultivation factors was found to enhance the PHA yield, the promotion of which was a consequence of the reduction in biomass production.
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- 2022
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7. Impact of short-term heat treatment on the structure and functional properties of commercial furcellaran compared to commercial carrageenans
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Kairit Eha, Tõnis Pehk, Ivo Heinmaa, Aleksei Kaleda, and Katrin Laos
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Carrageenan ,NMR ,Molecular weight ,Rheology ,Science (General) ,Q1-390 ,Social sciences (General) ,H1-99 - Abstract
In the production of biopolymers, the processing operations (e.g. extraction and drying) involve some degradation of the polysaccharide-causing structural and functional changes in final products. In this study, short-term heat treatment (75–115 °C, 15 min) influence on commercial carrageenans' — furcellaran, κ-carrageenan, ι-carrageenan and a κ/λ-carrageenan — structure, molecular weight and gel rheology was studied. Compared with other carrageenans, commercial furcellaran that had undergone multiple heatings at high temperatures during production was found to be susceptible to polymer degradation. Heat caused the desulphation and degradation of furcellaran galactans and the molecular weight was significantly decreased, causing a drop in viscosity and gel hardness. The loss of the network cross-linking of furcellaran gels was confirmed by scanning electron microscopy. Carrageenan gel storage modulus values decreased with the increase in the temperature of the treatment. The greatest decrease in storage modulus values occurred with κ/λ-carrageenan gels, followed by ι-carrageenan > furcellaran > κ-carrageenan.
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- 2021
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8. Efficiency of Iron- and Calcium-Impregnated Biochar in Adsorbing Phosphate From Wastewater in Onsite Wastewater Treatment Systems
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Sahar S. Dalahmeh, Ylva Stenström, Mohamed Jebrane, Lars D. Hylander, Geoffrey Daniel, and Ivo Heinmaa
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adsorption ,biochar ,iron impregnation ,calcium impregnation ,onsite wastewater treatment ,phosphate retention ,Environmental sciences ,GE1-350 - Abstract
This study evaluated the potential of biochar impregnated with Fe3+ or Ca2+, or mixed with Polonite®, as a filter material for removal of phosphate (PO4-P) from wastewater in onsite wastewater treatment systems (OWTS). Four treatments with biochar were investigated: unimpregnated biochar (UBC), biochar impregnated with iron Fe3+ (FBC), biochar impregnated with calcium oxide (CBC), and biochar mixed with Polonite® (PBC). In a batch experiment using phosphate solution at concentrations 0.5, 3.3, 6.5, 13, and 26 mg PO4-P L–1, adsorption of PO4-P in the different treatments was modeled using Langmuir and Freundlich isotherms. Column filters (5 diameter × 55 cm height) packed with UBC, FBC, CBC, and PBC were then furnished with raw wastewater over 148 weeks. During this experiment, adsorption of PO4-P was investigated in response to increasing hydraulic loading rate (HLR; 56, 74, and 112 L m–2 day–1) and increasing phosphate loading rate (PLR; 195, 324, 653, and 1715 mg PO4-P m–2 day–1). Among the materials, FBC had the highest maximum adsorption capacity (Qm) based on Langmuir isotherms (3.21 ± 0.01 mg g–1). FBC and CBC showed robust performance with increasing HLR, while increasing PLR increased the amount of PO4-P retained in all filters. After 148 weeks of operation, removal of PO4-P (averaged over the last 18 weeks of operation) was 13 ± 16% for UBC, 40 ± 20% for CBC, 88 ± 12% for FBC, and 30 ± 18% for PBC. The PO4-P amount retained in filters over the 148 weeks was 84.75, 221.75, 358.38, and 152.36 g m–2 in UBC, CBC, FBC, and PBC, respectively. The adsorption capacity of the filters after 148 weeks was 1.50, 4.02, 6.41, and 2.75 mg g–1 for UBC, CBC, FBC, and PBC, respectively. The adsorption capacity values and breakthrough curves showed that low concentrations (i.e.,
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- 2020
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9. Revealing three-dimensional quantum criticality by Sr substitution in Han purple
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Stephan Allenspach, Pascal Puphal, Joosep Link, Ivo Heinmaa, Ekaterina Pomjakushina, Cornelius Krellner, Jakob Lass, Gregory S. Tucker, Christof Niedermayer, Shusaku Imajo, Yoshimitsu Kohama, Koichi Kindo, Steffen Krämer, Mladen Horvatić, Marcelo Jaime, Alexander Madsen, Antonietta Mira, Nicolas Laflorencie, Frédéric Mila, Bruce Normand, Christian Rüegg, Raivo Stern, and Franziska Weickert
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Physics ,QC1-999 - Abstract
Classical and quantum phase transitions (QPTs), with their accompanying concepts of criticality and universality, are a cornerstone of statistical thermodynamics. An excellent example of a controlled QPT is the field-induced ordering of a gapped quantum magnet. Although numerous “quasi-one-dimensional” coupled spin-chain and -ladder materials are known whose ordering transition is three-dimensional (3D), quasi-two-dimensional (2D) systems are special for multiple reasons. Motivated by the ancient pigment Han purple (BaCuSi_{2}O_{6}), a quasi-2D material displaying anomalous critical properties, we present a complete analysis of Ba_{0.9}Sr_{0.1}CuSi_{2}O_{6}. We measure the zero-field magnetic excitations by neutron spectroscopy and deduce the spin Hamiltonian. We probe the field-induced transition by combining magnetization, specific-heat, torque, and magnetocalorimetric measurements with nuclear magnetic resonance studies near the QPT. With a Bayesian statistical analysis and large-scale Quantum Monte Carlo simulations, we demonstrate unambiguously that observable 3D quantum critical scaling is restored by the structural simplification arising from light Sr substitution in Han purple.
- Published
- 2021
- Full Text
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10. Improving the Electrochemical Performance and Stability of Polypyrrole by Polymerizing Ionic Liquids
- Author
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Arko Kesküla, Ivo Heinmaa, Tarmo Tamm, Nihan Aydemir, Jadranka Travas-Sejdic, Anna-Liisa Peikolainen, and Rudolf Kiefer
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ppypil ,electropolymerization ,ssnmr ,blend structure ,electrochemical performance ,Organic chemistry ,QD241-441 - Abstract
Polypyrrole (PPy) based electroactive materials are important building blocks for the development of flexible electronics, bio-sensors and actuator devices. As the properties and behavior of PPy depends strongly on the operating environment—electrolyte, solvent, etc., it is desirable to plant immobile ionic species into PPy films to ensure stable response. A premade ionic polymer is not optimal in many cases, as it enforces its own structure on the conducting polymer, therefore, polymerization during fabrication is preferred. Pyrrole (Py) was electropolymerized at low temperature together with a polymerizable ionic liquid (PIL) monomer in a one-step polymerization, to form a stable film on the working electrode. The structure and morphology of the PPyPIL films were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy and solid-state NMR (ssNMR) spectroscopy. The spectroscopy results confirmed the successful polymerization of Py to PPy and PIL monomer to PIL. The presence of (TFSI−) anions that balance the charge in PPyPIL was confirmed by EDX analysis. The electrical properties of PPyPIL in lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) aqueous and propylene carbonate solutions were examined with cyclic voltammetry (CV), chronoamperometry, and chronopotentiometry. The blend of PPyPIL had mixed electronic/ionic conductive properties that were strongly influenced by the solvent. In aqueous electrolyte, the electrical conductivity was 30 times lower and the diffusion coefficient 1.5 times higher than in the organic electrolyte. Importantly, the capacity, current density, and charge density were found to stay consistent, independent of the choice of solvent.
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- 2020
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11. Zeta Potential of Beta Zeolites: Influence of Structure, Acidity, pH, Temperature and Concentration
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Xuan Liu, Päivi Mäki-Arvela, Atte Aho, Zuzana Vajglova, Vladimir M. Gun’ko, Ivo Heinmaa, Narendra Kumar, Kari Eränen, Tapio Salmi, and Dmitry Yu. Murzin
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zeolites ,beta ,zeta potential ,Organic chemistry ,QD241-441 - Abstract
Measurements of the zeta potential of solid heterogeneous supports are important for preparation of metal supported catalysts and for shaping zeolites into extrudates. In the current work, different types of heterogeneous support materials such as SiO2, Al2O3, and a range of beta zeolites of different silica- to-alumina ratio were analysed. It was observed that parameters such as temperature, pH and acidity significantly affect the zeta potential. In several instances, depending on the materials’ acidity and microstructure, maxima in zeta potential were observed. The solid materials were thoroughly characterized using XRD, SEM, EDX, TEM, nitrogen physisorption, Al-NMR and FTIR with pyridine before zeta potential measurements.
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- 2018
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12. Bonding and Suppression of a Magnetic Phase Transition in EuMn2P2
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Tanya Berry, Nicodemos Varnava, Dominic H. Ryan, Veronica J. Stewart, Riho Rasta, Ivo Heinmaa, Nitesh Kumar, Walter Schnelle, Rishi Bhandia, Christopher M. Pasco, N. P. Armitage, Raivo Stern, Claudia Felser, David Vanderbilt, and Tyrel M. McQueen
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Colloid and Surface Chemistry ,General Chemistry ,Biochemistry ,Catalysis - Published
- 2023
13. Application of Immersed Membrane Bioreactor for Semi-Continuous Production of Polyhydroxyalkanoates from Organic Waste-Based Volatile Fatty Acids
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Åkesson, Danh H. Vu, Amir Mahboubi, Andrew Root, Ivo Heinmaa, Mohammad J. Taherzadeh, and Dan
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biopolymer ,immersed membrane reactor ,polyhydroxyalkanoates ,volatile fatty acids - Abstract
Volatile fatty acids (VFAs) appear to be an economical carbon feedstock for the cost-effective production of polyhydroxyalkanoates (PHAs). The use of VFAs, however, could impose a drawback of substrate inhibition at high concentrations, resulting in low microbial PHA productivity in batch cultivations. In this regard, retaining high cell density using immersed membrane bioreactor (iMBR) in a (semi-) continuous process could enhance production yields. In this study, an iMBR with a flat-sheet membrane was applied for semi-continuous cultivation and recovery of Cupriavidus necator in a bench-scale bioreactor using VFAs as the sole carbon source. The cultivation was prolonged up to 128 h under an interval feed of 5 g/L VFAs at a dilution rate of 0.15 (d−1), yielding a maximum biomass and PHA production of 6.6 and 2.8 g/L, respectively. Potato liquor and apple pomace-based VFAs with a total concentration of 8.8 g/L were also successfully used in the iMBR, rendering the highest PHA content of 1.3 g/L after 128 h of cultivation. The PHAs obtained from both synthetic and real VFA effluents were affirmed to be poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a crystallinity degree of 23.8 and 9.6%, respectively. The application of iMBR could open an opportunity for semi-continuous production of PHA, increasing the feasibility of upscaling PHA production using waste-based VFAs.
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- 2023
- Full Text
- View/download PDF
14. Turning food waste to antibacterial and biocompatible fungal chitin/chitosan monofilaments
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Sofie E, Svensson, Ana Osório, Oliveira, Karin H, Adolfsson, Ivo, Heinmaa, Andrew, Root, Nahid, Kondori, Jorge A, Ferreira, Minna, Hakkarainen, and Akram, Zamani
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Chitosan ,Organisk kemi ,Organic Chemistry ,Wet spinning ,Chitin ,macromolecular substances ,Other Industrial Biotechnology ,General Medicine ,Chitin/chitosan ,Microbiology ,Biochemistry ,Anti-Bacterial Agents ,Refuse Disposal ,carbohydrates (lipids) ,Antibacterial ,Mikrobiologi ,Food ,Annan industriell bioteknik ,Structural Biology ,Escherichia coli ,MAS NMR ,Humans ,Biocompatibility ,Fungal textiles ,Molecular Biology - Abstract
Here, cell wall of a zygomycete fungus, Rhizopus delemar, grown on bread waste was wet spun into monofilaments. Using the whole cell wall material omits the common chitosan isolation and purification steps and leads to higher material utilization. The fungal cell wall contained 36.9% and 19.7% chitosan and chitin, respectively. Solid state NMR of the fungal cell wall material confirmed the presence of chitosan, chitin, and other carbohydrates. Hydrogels were prepared by ultrafine grinding of the cell wall, followed by addition of lactic acid to protonate the amino groups of chitosan, and subsequently wet spun into monofilaments. The monofilament inhibited the growth of Bacillus megaterium (Gram+ bacterium) and Escherichia coli (Gram- bacterium) significantly (92.2% and 99.7% respectively). Cytotoxicity was evaluated using an in vitro assay with human dermal fibroblasts, indicating no toxic inducement from exposure of the monofilaments. The antimicrobial and biocompatible fungal monofilaments, open new avenues for sustainable biomedical textiles from abundant food waste. © 2022 The Authors
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- 2022
15. Orbital disorder and ordering in NaTiSi2O6 : Si29 and Na23 NMR study
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Ivo Heinmaa, Riho Rästa, Harlyn J. Silverstein, Christopher R. Wiebe, and Raivo Stern
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- 2022
16. Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes
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Ivo Heinmaa, Jan Novotný, Stanislav Komorovsky, Lukáš Jeremias, Patrick R. Nimax, and Radek Marek
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010405 organic chemistry ,Chemistry ,Resonance ,Nuclear magnetic resonance spectroscopy ,Carbon-13 NMR ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Crystallography ,Unpaired electron ,Transition metal ,Molecule ,Condensed Matter::Strongly Correlated Electrons ,Electron configuration ,Physical and Theoretical Chemistry ,Hyperfine structure - Abstract
Nuclear magnetic resonance (NMR) spectroscopy of paramagnetic molecules provides detailed information about their molecular and electron-spin structure. The paramagnetic NMR spectrum is a very rich source of information about the hyperfine interaction between the atomic nuclei and the unpaired electron density. The Fermi-contact contribution to ligand hyperfine NMR shifts is particularly informative about the nature of the metal-ligand bonding and the structural arrangements of the ligands coordinated to the metal center. In this account, we provide a detailed experimental and theoretical NMR study of compounds of Cr(III) and Cu(II) coordinated with substituted acetylacetonate (acac) ligands in the solid state. For the first time, we report the experimental observation of extremely paramagnetically deshielded 13C NMR resonances for these compounds in the range of 900-1200 ppm. We demonstrate an excellent agreement between the experimental NMR shifts and those calculated using relativistic density-functional theory. Crystal packing is shown to significantly influence the NMR shifts in the solid state, as demonstrated by theoretical calculations of various supramolecular clusters. The resonances are assigned to individual atoms in octahedral Cr(acac)3 and square-planar Cu(acac)2 compounds and interpreted by different electron configurations and magnetizations at the central metal atoms resulting in different spin delocalizations and polarizations of the ligand atoms. Further, effects of substituents on the 13C NMR resonance of the ipso carbon atom reaching almost 700 ppm for Cr(acac)3 compounds are interpreted based on the analysis of Fermi-contact hyperfine contributions.
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- 2021
17. Revealing three-dimensional quantum criticality by Sr substitution in Han purple
- Author
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Alexander Madsen, Christian Rüegg, Pascal Puphal, Stephan Allenspach, Nicolas Laflorencie, Jakob Lass, Ivo Heinmaa, Shusaku Imajo, Antonietta Mira, Raivo Stern, Joosep Link, Mladen Horvatić, Frédéric Mila, Franziska Weickert, G. S. Tucker, Cornelius Krellner, Bruce Normand, Steffen Krämer, Marcelo Jaime, Christof Niedermayer, Koichi Kindo, Yoshimitsu Kohama, Ekaterina Pomjakushina, Fermions Fortement Corrélés (LPT) (FFC), Laboratoire de Physique Théorique (LPT), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI-G ), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), ANR-16-CE30-0023,THERMOLOC,Thermalisation et localisation dans les systèmes à N corps: compréhension théorique et intêret experimental(2016), and ANR-19-CE30-0013,GLADYS,De la nature vitreuse des systèmes quantiques désordonnés(2019)
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Phase transition ,bose-einstein condensation ,Dimer ,FOS: Physical sciences ,02 engineering and technology ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,Condensed Matter - Strongly Correlated Electrons ,ground-state ,law ,0103 physical sciences ,Spin model ,BOSE-EINSTEIN CONDENSATION ,Antiferromagnetism ,magnetization plateaus ,FIELD ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,010306 general physics ,TEMPERATURE ,Quantum ,ComputingMilieux_MISCELLANEOUS ,antiferromagnet ,Physics ,model ,Strongly Correlated Electrons (cond-mat.str-el) ,phase-transitions ,Substitution (logic) ,ANTIFERROMAGNET ,temperature ,021001 nanoscience & nanotechnology ,field ,MAGNETIZATION PLATEAUS ,MODEL ,Crystallography ,chemistry ,GROUND-STATE ,PHASE-TRANSITIONS ,[PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el] ,0210 nano-technology ,Ground state ,Bose–Einstein condensate - Abstract
Classical and quantum phase transitions (QPTs), with their accompanying concepts of criticality and universality, are a cornerstone of statistical thermodynamics. An exemplary controlled QPT is the field-induced magnetic ordering of a gapped quantum magnet. Although numerous "quasi-one-dimensional" coupled spin-chain and -ladder materials are known whose ordering transition is three-dimensional (3D), quasi-2D systems are special for several physical reasons. Motivated by the ancient pigment Han Purple (BaCuSi$_{2}$O$_{6}$), a quasi-2D material displaying anomalous critical properties, we present a complete analysis of Ba$_{0.9}$Sr$_{0.1}$CuSi$_{2}$O$_{6}$. We measure the zero-field magnetic excitations by neutron spectroscopy and deduce the magnetic Hamiltonian. We probe the field-induced transition by combining magnetization, specific-heat, torque and magnetocalorimetric measurements with low-temperature nuclear magnetic resonance studies near the QPT. By a Bayesian statistical analysis and large-scale Quantum Monte Carlo simulations, we demonstrate unambiguously that observable 3D quantum critical scaling is restored by the structural simplification arising from light Sr-substitution in Han Purple., 19 pages, 5 figures
- Published
- 2021
18. Highly selective Prins reaction over acid-modified halloysite nanotubes for synthesis of isopulegol-derived 2H-chromene compounds
- Author
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D. Yu. Murzin, A.V. Kravtsova, A.Yu. Sidorenko, Vladimir Agabekov, Atte Aho, Johan Wärnå, Ivo Heinmaa, Konstantin P. Volcho, Hanna Pazniak, and Nariman F. Salakhutdinov
- Subjects
Cyclohexane ,010405 organic chemistry ,Prins reaction ,engineering.material ,010402 general chemistry ,01 natural sciences ,Halloysite ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Montmorillonite ,chemistry ,Pyridine ,engineering ,Physical and Theoretical Chemistry ,Brønsted–Lowry acid–base theory ,Selectivity ,Nuclear chemistry - Abstract
Prins reaction of terpenoid (−)-isopulegol with thiophene-2-carbaldehyde giving in substituted octahydro-2H-chromen-4-ol (as 4R- and 4S-diastereomers) was studied for the first time over a series of halloysite nanotubes (Dragon Mine, USA), treated with 1–30% HCl. Materials have been characterized by MAS NMR, XRD, XRF, N2 adsorption, FTIR with pyridine, SEM, TEM and thermal analysis methods. The quantitative data on the effect of acid treatment conditions on the content of structural units of halloysite are presented for the first time. The effect HNT treatment conditions, reaction temperature, catalyst loading, initial concentration of substrates on overall selectivity and 4R/4S ratio was studied. The diastereomers ratio decreased from 6.5 for air-dry nanotubes to 3.6 for counterparts dried at 350 °C, which clearly indicates formation of 4R-isomer on weak Bronsted acid sites At 99% isopulegol conversion in cyclohexane over HNT treated with 5% HCl an unprecedented selectivity towards 4R alone (ca. 80%) was achieved close to the sum of both diastereomers on a commercial montmorillonite K-10. The 4R/4S ratio decreased with an increase in the concentration of acid sites. The excellent selectivity on halloysite was due to the predominance of weak acid sites. On the contrary, a low chromenols yield (ca. 30%) was observed over strong Bronsted acid (resin Amberlyst-15) related to direct formation of dehydration products from the substrates. Kinetic modelling shows a substantial difference in the order to the catalyst for the dried at 110 °C resin (1.1 ± 0.12) and air-dry halloysite (1.95 ± 0.09) for the target 4R-isomer formation, which clearly indicates the key role of water in the reaction. Based on experimental results and kinetic modelling a dual mechanism of halloysite action was proposed implying formation of an intermediate with the reagents and transfer of the surface water to the intermediate giving chromenols. Stability of the catalytic properties and reusability of HNT were demonstrated. Thus, modified halloysite nanotubes can be considered as a novel type of highly selective catalysts for the Prins reaction.
- Published
- 2019
19. Fungal textile alternatives from bread waste with leather-like properties
- Author
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Andrew Root, E.R. Kanishka B. Wijayarathna, Akram Zamani, Ivo Heinmaa, Linn Berglund, Minna Hakkarainen, Karin H. Adolfsson, Amir Mahboubi Soufiani, Ghasem Mohammadkhani, and Jorge A. Ferreira
- Subjects
Economics and Econometrics ,Textile ,Filamentous fungi ,Biomass ,Food waste recovery ,Industrial Biotechnology ,chemistry.chemical_compound ,Industriell bioteknik ,Ultimate tensile strength ,Glycerol ,Polymerkemi ,Tannin ,Waste Management and Disposal ,chemistry.chemical_classification ,TGA ,Moisture ,business.industry ,Tanning ,Pulp and paper industry ,Polymer Chemistry ,Environmentally friendly ,NMR ,Food waste ,chemistry ,Fungal textiles ,AFM ,business - Abstract
Food waste and fashion pollution are two of the most prominent global environmental issues. To alleviate the problems associated with food waste, while simultaneously contributing to sustainable fashion, the feasibility of making an alternative textile material with leather-like properties from fungal biomass cultivated on bread waste was investigated. The filamentous fungus, Rhizopus delemar, was successfully grown on waste bread in a submerged cultivation process, and fungal biomass was treated with vegetable tannin of chestnut wood. NMR and FTIR confirmed interactions between tannin and fungal biomass, while OM, SEM and AFM visualised the changes in the hyphae upon the tannin treatment. Thermal stability was assessed using TGA analysis. The wet-laid technique commonly utilised for paper-making was used to prepare sheets of hyphae. Some of the sheets were treated with glycerol and/or a biobased binder as post-treatment. Overall, three of the produced materials exhibited leather-like properties comparable to that of natural leather. Sheets from untreated biomass with only glycerol post-treatment showed a tensile strength of 7.7 MPa and an elongation at break of 5%. Whereas sheets from untreated biomass and tannin treated biomass with both glycerol and binder treatments led to tensile strengths of 7.1 MPa and 6.9 MPa, and the elongation at break of 12% and 17%, respectively. The enhancement of hydrophobicity after the binder treatment, helped to preserve the absorbed glycerol within the sheet and thereby the flexibility was retained when in contact with moisture. These findings demonstrate that bread waste-derived fungal sheets have great potential as environmentally friendly materials with leather-like properties.
- Published
- 2021
20. Acid sites modulation of siliceous-based mesoporous material by post synthesis methods
- Author
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Atte Aho, Giuseppe Cruciani, Dmitry Yu. Murzin, Markus Peurla, Federica Menegazzo, Cristina Pizzolitto, Tapio Salmi, Narendra Kumar, Somayeh Taghavi, Michela Signoretto, Kari Eränen, Ivo Heinmaa, and Elena Ghedini
- Subjects
chemistry.chemical_classification ,Materials science ,Acid site modification ,Ambientale ,General Chemistry ,Sulfonic acid ,Condensed Matter Physics ,Settore CHIM/04 - Chimica Industriale ,Brønsted acidity ,Lewis acidity ,Porosity ,Promoted SBA-15 ,Catalysis ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Mechanics of Materials ,Pyridine ,Levulinic acid ,General Materials Science ,Lewis acids and bases ,Fourier transform infrared spectroscopy ,Mesoporous material - Abstract
The present work is focused on the improvement of an effective approach to tailor the acidity of silica alumina composite. SBA-15 was selected based on high surface area, uniform porosity and large mesopores. Modification of SBA-15 was performed to improve both Lewis and Bronsted acidities and hence catalyst activity. Therefore, introduction of alumina as a co-catalyst was carried out to enhance Lewis acid sites through its incorporation into the silica network. Evaporation impregnation method was evaluated for incorporation of aluminium to SBA-15 and materials with different SiO2/Al2O3 ratios were prepared. Acidity and morphological features of the materials were assessed using XRD, EDX, SEM, TEM, N2-physisorption, 27Al MAS-NMR and FTIR with pyridine. Bronsted acidity was attained by the introduction of sulfonic acid groups in the final catalyst via the post-synthesis grafting method. Therefore, the balanced Lewis and Bronsted acidities and proper porosity of modified SBA-15 led to its efficient performance in the conversion of glucose as a biomass-based model component to levulinic acid.
- Published
- 2021
21. Modelling of an aza-Michael reaction from crystalline naphthalene derivatives containing peri–peri interactions: very long N–C bonds?
- Author
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Stacey V. A. Cliff, John D. Wallis, Raivo Stern, Isaac Naftalin, Jonathan C. Bristow, Ivo Heinmaa, Marina Carravetta, and Songjie Yang
- Subjects
chemistry.chemical_classification ,Ethylene ,Alkene ,Peri ,Substituent ,General Chemistry ,Condensed Matter Physics ,chemistry.chemical_compound ,Crystallography ,Solid-state nuclear magnetic resonance ,chemistry ,Michael reaction ,Molecule ,General Materials Science ,Naphthalene - Abstract
The separation between a pair of peri-located dimethylamino and ethene-2,2-dinitrile groups in a naphthalene molecule, which models the progress of a Michael reaction, can be controlled by the installation of a short ethylene bridge or the introduction of repulsive interactions at the opposite set of peri positions. Introduction of a dimethylammonium substituent produced a hydrated chloride salt in which the Me2N⋯C(H)[double bond, length as m-dash]C(CN)2 separation between reactive groups decreases, reversibly, from 2.167 Å at 200 K to 1.749 Å at 100 K, with the maximum rate of change in the range 128–140 K, which was studied by variable temperature X-ray crystallography and solid state NMR. From these and other crystallographic data a correlation between Me2N⋯C bond formation and alkene bond breaking was constructed for the first step of an aza-Michael reaction.
- Published
- 2020
22. Magnetic structure of the square cupola compound Ba(TiO) Cu4(PO4)4
- Author
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Raivo Stern, Kenta Kimura, Tsuyoshi Kimura, Riho Rästa, and Ivo Heinmaa
- Subjects
Physics ,Magnetic structure ,Spins ,Magnetism ,Point reflection ,Magnetoelectric effect ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Coupling (probability) ,01 natural sciences ,Square (algebra) ,Crystallography ,0103 physical sciences ,Condensed Matter::Strongly Correlated Electrons ,Cupola (geometry) ,010306 general physics ,0210 nano-technology - Abstract
A noncollinear arrangement of spins is a source of interesting phenomena in magnets. Thus, the loss of inversion symmetry activates asymmetric interactions via the relativistic spin-orbit coupling that can cause the magnetoelectric effect, a cross-correlation between dielectricity and magnetism. Here, the authors report NMR studies of the magnetic structure in BaTiOCu${}_{4}$(PO${}_{4}{)}_{4}$, a newly discovered magnetic insulator with antiferromagnetically rotated Cu${}_{4}$O${}_{12}$ square cupola clusters, formed by four corner-sharing CuO${}_{4}$ plaquettes. Using Cu zero-field NMR, theyunambiguously identify the model ${\mathrm{\ensuremath{\Gamma}}}_{3}$(2) with the moments pointing out of the CuO${}_{4}$ planes.
- Published
- 2020
23. Direct magnetic-field dependence of NMR chemical shift
- Author
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Ivo Heinmaa, Anu M. Kantola, Juha Vaara, Jukka Jokisaari, and Perttu Lantto
- Subjects
Materials science ,010304 chemical physics ,Field (physics) ,Chemical shift ,General Physics and Astronomy ,010402 general chemistry ,7. Clean energy ,01 natural sciences ,0104 chemical sciences ,Magnetic field ,Atomic orbital ,0103 physical sciences ,Electromagnetic shielding ,Diamagnetism ,Physical and Theoretical Chemistry ,Atomic physics ,Excitation ,Order of magnitude - Abstract
Nuclear shielding and chemical shift are considered independent of the magnetic-field strength. Ramsey proposed on theoretical grounds in 1970 that this may not be valid for heavy nuclei. Here we present experimental evidence for the direct field dependence of shielding, using 59Co shielding in Co(acac)3 [tris(acetylacetonate)cobalt(III)] as an example. We carry out NMR experiments in four field strengths for this low-spin diamagnetic Co(III) complex, which features a very large and negative nuclear shielding constant of the central Co nucleus. This is due to a magnetically accessible, low-energy eg ← t2g orbital excitation of the d6 system. The experiments result in temperature-dependent magnetic-field dependence of −5.7 to −5.2 ppb T−2 of the 59Co shielding constant, arising from the direct modification of the electron cloud of the complex by the field. First-principles multiconfigurational non-linear response theory calculations verify the sign and order of magnitude of the experimental results.
- Published
- 2020
24. Acid-modified Halloysite Nanotubes as a Stereoselective Catalyst for Synthesis of 2H -Chromene Derivatives by the Reaction of Isopulegol with Aldehydes
- Author
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Ivo Heinmaa, Vladimir Agabekov, Dmitry Yu. Murzin, Alexander Yu. Sidorenko, A.V. Kravtsova, Nariman F. Salakhutdinov, Konstantin P. Volcho, and Atte Aho
- Subjects
010405 organic chemistry ,Chemistry ,Organic Chemistry ,engineering.material ,010402 general chemistry ,01 natural sciences ,Halloysite ,Catalysis ,0104 chemical sciences ,Inorganic Chemistry ,engineering ,Organic chemistry ,2H-chromene ,Stereoselectivity ,Physical and Theoretical Chemistry - Published
- 2018
25. Catalytic isomerization of α-pinene oxide in the presence of acid-modified clays
- Author
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Atte Aho, T.F. Kuznetsova, Ivo Heinmaa, A.Yu. Sidorenko, D. Yu. Murzin, A.V. Kravtsova, and Vladimir Agabekov
- Subjects
chemistry.chemical_classification ,Cyclohexane ,010405 organic chemistry ,Process Chemistry and Technology ,Sorption ,engineering.material ,010402 general chemistry ,01 natural sciences ,Aldehyde ,Catalysis ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Aluminosilicate ,Illite ,engineering ,Calcination ,Physical and Theoretical Chemistry ,Isomerization ,Nuclear chemistry - Abstract
Isomerization of α-pinene oxide was studied at 20–50 °C in the presence of commercial montmorillonites K-10 and K-30, acid-treated illite clay as well as synthetic aluminosilicate AS-36 using cyclohexane as a solvent. The catalysts were characterized by XRD, XRF, FTIR, MAS NMR, thermal analysis and N2 low-temperature sorption methods The main reaction products at 99.9% conversion of the substrate are campholenic and iso-campholenic aldehydes, the largest amount of which (68.1 wt.%) is formed on illite clay treated by 10% HCl. The iso-campholenic/campholenic aldehydes ratio decreases from 0.7 to 0.25 with an increase of acidity of the catalyst from 47 to 153 μmol/g. The content of products with p-menthane structure (trans-carveol, trans-sorberol, p-cymene, pinol) reaches a maximum (33.0 wt.%) in the presence of medium-acid (104.0 μmol/g) K-10 clay. The amount of campholenic aldehyde in reaction mixture increases from 34.3 to 48.2 wt.%, and content of iso-campholenic aldehyde decreases from 33.7 to 17.7 wt.% with increasing the drying (calcination) temperature of illite clay from 50 to 600 °C respectively. The scheme for the formation of reaction products on clays was proposed.
- Published
- 2018
26. Synthesis and physicochemical characterization of beta zeolite–bentonite composite materials for shaped catalysts
- Author
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Zuzana Vajglová, Janne Peltonen, Markus Peurla, Dmitry Yu. Murzin, Narendra Kumar, and Ivo Heinmaa
- Subjects
Materials science ,Composite number ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Aluminosilicate ,Bentonite ,Particle size ,Fourier transform infrared spectroscopy ,Composite material ,0210 nano-technology ,Zeolite ,Porosity ,ta116 ,Powder diffraction - Abstract
Composite materials for shaped catalysts were prepared from three commercial beta zeolites using bentonite as an aluminosilicate clay binder. All pristine materials and the synthesized powder mixtures were characterized using X-ray powder diffraction for phase purity and structures, scanning electron microscopy for morphology, transmission electron microscopy for porosity and periodicity, nitrogen physisorption for surface area, pore volume and pore size distribution, and Fourier transform infrared spectroscopy using pyridine as a probe molecule to elucidate the presence, strength and amount of Bronsted and Lewis acid sites. Elemental analysis was carried out using energy dispersive X-ray micro-analysis. Through a systematic comparison of the properties of the individual components and powder zeolite–binder composites, this study elucidated the crucial binder influence on the key properties of the catalytic supports during the synthesis of the composites in the powder form, i.e. prior to shaping. It can be concluded that the promoting effect of the bentonite binder is derived from chemical interactions with the zeolite. The resulting effect of the binder on the composite properties is not a simple additive just reflecting the nominal ratio of the components. The synthesis process, zeolite type (SiO2/Al2O3 ratio of the framework, particle size) and binder concentration play a significant role in the resulting binder effect in composites.
- Published
- 2018
27. New insights in evaluation of acid sites in micro-mesoporous zeolite-like materials using potentiometric titration method
- Author
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Kai Yu, Dmitry Yu. Murzin, Sergii A. Sergiienko, Svitlana Filonenko, Nataliya D. Shcherban, Roman Barakov, Ari Ivaska, and Ivo Heinmaa
- Subjects
Process Chemistry and Technology ,Potentiometric titration ,Inorganic chemistry ,Sorption ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallinity ,chemistry ,Pyridine ,Titration ,0210 nano-technology ,Zeolite ,Mesoporous material - Abstract
Potentiometric titration was used to characterize the acid-base properties of micro-mesoporous zeolite-like materials obtained via dual template synthesis using sol-precursors of Beta zeolite and micellar templates. The obtained results were compared with other methods of acidity determination (ammonia TPD, pyridine ad(de)sorption). The acid sites with the strength comparable to Beta zeolite (lg K values 4.3–4.7) were found in low-crystalline and X-ray amorphous micro-mesoporous materials. The strongest acid sites were observed in conventional Beta zeolite and a low-crystalline (degree of crystallinity ca. 0.1) micro-mesoporous material prepared on its basis (lg K 4.3) in concentration of 450 and 100 μmol/g, respectively. A change from acidic to alkaline reaction media in the second stage of micro-mesoporous materials preparation led to an increase of the acid sites concentration from 190 to 600 μmol/g concomitant with formation of a high fraction of comparatively strong acid sites (lg K 4.7, 200 μmol/g). A high content of acid sites in low-crystalline and X-ray amorphous samples was assigned to acidity of zeolite precursors rather than zeolite crystals.
- Published
- 2017
28. NMR, magnetization, and heat capacity studies of the uniform spin- 12 chain compound Bi6V3O16
- Author
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V. Yu. Verchenko, Tanmoy Chakrabarty, Raivo Stern, P. L. Paulose, and Ivo Heinmaa
- Subjects
Physics ,Magnetism ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Heat capacity ,Magnetic susceptibility ,Ion ,NMR spectra database ,Crystallography ,Magnetization ,0103 physical sciences ,Magic angle spinning ,Condensed Matter::Strongly Correlated Electrons ,010306 general physics ,0210 nano-technology ,Spin (physics) - Abstract
We report the local (NMR) and bulk (magnetization and heat capacity) properties of the vanadium-based $S=\frac{1}{2}$ uniform spin chain compound ${\mathrm{Bi}}_{6}{\mathrm{V}}_{3}{\mathrm{O}}_{16}\phantom{\rule{4pt}{0ex}}({\mathrm{Bi}}_{4}{\mathrm{V}}_{2}{\mathrm{O}}_{10.66})$. In the low-temperature $\ensuremath{\alpha}$ phase, the magnetic ions $({\mathrm{V}}^{4+})$ are arranged in one-dimensional chains. The magnetic susceptibility shows a broad maximum around 50 K signifying a short-range magnetic order. Heat capacity measurements also reveal low-dimensional magnetism. The $^{51}\mathrm{V}$ magic angle spinning nuclear magnetic resonance measurements clearly show that the magnetic ${\mathrm{V}}^{4+}$ and nonmagnetic ${\mathrm{V}}^{5+}$ species are located on different crystallographic sites with no mixed occupation. The spin susceptibility calculated from the shift of the $^{51}\mathrm{V}$ NMR spectra reproduces the behavior observed in magnetic susceptibility and agrees well with the $S=\frac{1}{2}$ uniform spin chain model with $J=113(5)$ K.
- Published
- 2019
29. From Fe32+δGe35-xPx to Fe32+δGe35-x-yPxAsy: fine geometry optimization in new intergrowth structures
- Author
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Evgeny V. Dikarev, Ivo Heinmaa, Andrei V. Shevelkov, Zheng Wei, Anton Jesche, Raivo Stern, Alexander A. Tsirlin, Valeriy Yu. Verchenko, and Roman A. Khalaniya
- Subjects
Materials science ,Mechanical Engineering ,Metals and Alloys ,Structure (category theory) ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Energy minimization ,Base (topology) ,01 natural sciences ,0104 chemical sciences ,Crystallography ,Mechanics of Materials ,Materials Chemistry ,0210 nano-technology ,Solid solution - Abstract
A new compound with a two-dimensional intergrowth structure, Fe32+δGe35-xPx (x = 1.7–4.4, δ = 0.6–0.75), and the solid solution on its base, Fe32+δGe35-x-yPxAsy (δ
- Published
- 2019
30. Impact of short-term heat treatment on the structure and functional properties of commercial furcellaran compared to commercial carrageenans
- Author
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Aleksei Kaleda, Katrin Laos, Tõnis Pehk, Ivo Heinmaa, and Kairit Eha
- Subjects
0301 basic medicine ,Science (General) ,animal structures ,Scanning electron microscope ,animal diseases ,Carrageenan ,Molecular weight ,Q1-390 ,03 medical and health sciences ,Viscosity ,chemistry.chemical_compound ,0302 clinical medicine ,Polymer degradation ,Rheology ,H1-99 ,Multidisciplinary ,Chemistry ,Extraction (chemistry) ,Dynamic mechanical analysis ,respiratory system ,NMR ,Social sciences (General) ,carbohydrates (lipids) ,030104 developmental biology ,Chemical engineering ,Degradation (geology) ,030217 neurology & neurosurgery ,Research Article - Abstract
In the production of biopolymers, the processing operations (e.g. extraction and drying) involve some degradation of the polysaccharide-causing structural and functional changes in final products. In this study, short-term heat treatment (75–115 °C, 15 min) influence on commercial carrageenans' — furcellaran, κ-carrageenan, ι-carrageenan and a κ/λ-carrageenan — structure, molecular weight and gel rheology was studied. Compared with other carrageenans, commercial furcellaran that had undergone multiple heatings at high temperatures during production was found to be susceptible to polymer degradation. Heat caused the desulphation and degradation of furcellaran galactans and the molecular weight was significantly decreased, causing a drop in viscosity and gel hardness. The loss of the network cross-linking of furcellaran gels was confirmed by scanning electron microscopy. Carrageenan gel storage modulus values decreased with the increase in the temperature of the treatment. The greatest decrease in storage modulus values occurred with κ/λ-carrageenan gels, followed by ι-carrageenan > furcellaran > κ-carrageenan., Carrageenan; NMR; Molecular weight; Rheology
- Published
- 2021
31. Solvent-free synthesis of tetrahydropyran alcohols over acid-modified clays
- Author
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Vladimir Agabekov, Zh.V. Ihnatovich, Atte Aho, Ivo Heinmaa, T.F. Kuznetsova, A.Yu. Sidorenko, D. Yu. Murzin, and Yu.M. Kurban
- Subjects
inorganic chemicals ,010405 organic chemistry ,Process Chemistry and Technology ,Tetrahydropyran ,engineering.material ,010402 general chemistry ,01 natural sciences ,Halloysite ,Catalysis ,Isovaleraldehyde ,0104 chemical sciences ,Solvent ,chemistry.chemical_compound ,Montmorillonite ,chemistry ,Specific surface area ,engineering ,Organic chemistry ,Physical and Theoretical Chemistry ,Selectivity - Abstract
A number of acid-modified clays (halloysite, montmorillonite, illite) were studied as catalysts for isoprenol cyclization with isovaleraldehyde to tetrahydropyranols used in perfumery as a mixture of cis- and trans- isomers. The main attention was paid to properties of halloysite nanotubes after treating them with 5% HCl at temperatures from 30 to 100 °C. The catalysts were characterized by XRD, EDX, MAS NMR, SEM, and N2 adsorption-desorption methods. The acid modification of halloysite allows an efficient increase of its acidity and specific surface area, while preserving morphology of nanotubes. On relatively weakly acidic clays, the formation of the target product occurs through a hemiacetal as a precursor. On the contrary, over strongly acidic resin Amberlyst-15, the yield of tetrahydropyranol was significantly lower because of a direct formation of tetrahydropyranols and dehydration by-products. The yield of tetrahydropyranol in the presence of clays was 65–72 %, slightly increasing with an increase in their acidity. The selectivity towards the cis- isomer did not practically depend on the acid sites concentration in clays, decreasing slightly for the trans-isomer with decreasing acidity due to formation of the dehydration by-products. In general, acid-modified clays are promising catalysts for the preparation of tetrahydropyranols under mild conditions and in the absence of any solvent.
- Published
- 2021
32. Alkali activated construction materials: Assessing the alternative use for oil shale processing solid wastes
- Author
-
Päärn Paiste, Kalle Kirsimäe, Signe Vahur, Ivo Heinmaa, and Martin Liira
- Subjects
Chemical substance ,Materials science ,Metallurgy ,02 engineering and technology ,Building and Construction ,010501 environmental sciences ,021001 nanoscience & nanotechnology ,01 natural sciences ,Silicate ,law.invention ,Amorphous solid ,chemistry.chemical_compound ,Compressive strength ,chemistry ,Magazine ,law ,General Materials Science ,Cementitious ,0210 nano-technology ,Oil shale ,Curing (chemistry) ,0105 earth and related environmental sciences ,Civil and Structural Engineering - Abstract
The potential of oil shale ash wastes as a source material for geopolymeric or alkali activated construction materials was assessed using structural, XRD, SEM, SEM-EDX, ATR-FTIR and 29 Si MAS-NMR methods. Fresh, unhydrated furnace bottom and cyclone separator ash along ash plateau sediment were used in combination with 5 M NaOH and Na 2 SiO 3 solutions with SiO 2 /Na 2 O ratios of 2.72 and 1.5 as alkaline activators, under ambient curing conditions. Our analytical results show that only activator solutions containing soluble silicate will induce the formation of amorphous C-(A)-S-H gel, giving the samples 8 times higher compressive strength (8.5 MPa) than samples exhibiting cementitious properties upon hydration (1.25 MPa).
- Published
- 2016
33. Synthesis and physico-chemical characterization of Beta zeolite catalysts: Evaluation of catalytic properties in Prins cyclization of (−)-isopulegol
- Author
-
Markus Peurla, Nikolai Li-Zhulanov, Janne Peltonen, Anna O. Zaykovskaya, Päivi Mäki-Arvela, Dmitry Yu. Murzin, Stéphane Streiff, Bright T. Kusema, Atte Aho, Ekaterina Kholkina, Ivo Heinmaa, and Narendra Kumar
- Subjects
Aqueous solution ,Materials science ,02 engineering and technology ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,Prins reaction ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Benzaldehyde ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,General Materials Science ,Fourier transform infrared spectroscopy ,0210 nano-technology ,Spectroscopy ,Zeolite ,Nuclear chemistry - Abstract
Synthesis of Beta zeolite catalysts was carried out using two different methods. The influence of such parameters as synthesis time and temperature, gel composition and gel ripening on the physico-chemical and catalytic properties of Beta zeolite catalysts was studied. A range of analytical methods was applied in this work including scanning and transmission electron microscopies, energy dispersive X-ray spectroscopy, X-ray powder diffraction, nuclear magnetic resonance spectroscopy – 27A1-MAS-NMR and 29Si-MAS-NMR, nitrogen physisorption, Fourier transform infrared spectroscopy and inductively coupled plasma optical emission spectrometry. The sodium forms of Beta zeolites were transformed to the proton forms H-Beta by ion-exchange using aqueous solutions of NH4NO3 and thereafter evaluated in Prins cyclization of (−)-isopulegol with benzaldehyde. The best catalyst synthesized at 150 °C in the rotation mode for 17 h possessing an optimal combination of morphological and structural properties as well as concentration of acid sites demonstrated high (−)-isopulegol conversion (93%) along with high selectivity to the desired product (79%).
- Published
- 2020
34. Improving the Electrochemical Performance and Stability of Polypyrrole by Polymerizing Ionic Liquids
- Author
-
Anna-Liisa Peikolainen, Rudolf Kiefer, Nihan Aydemir, Ivo Heinmaa, Tarmo Tamm, Arko Kesküla, and Jadranka Travas-Sejdic
- Subjects
Conductive polymer ,Materials science ,Polymers and Plastics ,electropolymerization ,General Chemistry ,Electrolyte ,Chronoamperometry ,Polypyrrole ,Article ,lcsh:QD241-441 ,chemistry.chemical_compound ,ssnmr ,lcsh:Organic chemistry ,chemistry ,Polymerization ,Chemical engineering ,Ionic liquid ,Propylene carbonate ,electrochemical performance ,ppypil ,Cyclic voltammetry ,blend structure - Abstract
Polypyrrole (PPy) based electroactive materials are important building blocks for the development of flexible electronics, bio-sensors and actuator devices. As the properties and behavior of PPy depends strongly on the operating environment&mdash, electrolyte, solvent, etc., it is desirable to plant immobile ionic species into PPy films to ensure stable response. A premade ionic polymer is not optimal in many cases, as it enforces its own structure on the conducting polymer, therefore, polymerization during fabrication is preferred. Pyrrole (Py) was electropolymerized at low temperature together with a polymerizable ionic liquid (PIL) monomer in a one-step polymerization, to form a stable film on the working electrode. The structure and morphology of the PPyPIL films were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy and solid-state NMR (ssNMR) spectroscopy. The spectroscopy results confirmed the successful polymerization of Py to PPy and PIL monomer to PIL. The presence of (TFSI&ndash, ) anions that balance the charge in PPyPIL was confirmed by EDX analysis. The electrical properties of PPyPIL in lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) aqueous and propylene carbonate solutions were examined with cyclic voltammetry (CV), chronoamperometry, and chronopotentiometry. The blend of PPyPIL had mixed electronic/ionic conductive properties that were strongly influenced by the solvent. In aqueous electrolyte, the electrical conductivity was 30 times lower and the diffusion coefficient 1.5 times higher than in the organic electrolyte. Importantly, the capacity, current density, and charge density were found to stay consistent, independent of the choice of solvent.
- Published
- 2020
35. Long-term mineral transformation of Ca-rich oil shale ash waste
- Author
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Päärn Paiste, Peeter Paaver, Alar Konist, Kristjan Leben, Ivo Heinmaa, Riho Mõtlep, Gunnar Nurk, Edward J. Anthony, Kalle Kirsimäe, and T. Pihu
- Subjects
Environmental Engineering ,010504 meteorology & atmospheric sciences ,Alkalinity ,010501 environmental sciences ,01 natural sciences ,Silicate minerals ,Environmental Chemistry ,Coal ,Ash utilisation ,Waste Management and Disposal ,0105 earth and related environmental sciences ,Mineral ,business.industry ,Alkali-activation ,Metallurgy ,Fossil fuel ,Mineralogy ,Pollution ,C-S-H ,Amorphous solid ,Deposition (aerosol physics) ,Oil shale ash ,Environmental science ,business ,Stability ,Oil shale - Abstract
Power generation and other industries using solid fossil fuels like coal, lignite, oil shale and peat are responsible for producing large quantities of solid residues that are often chemically reactive and/or unstable and are disposed in holding ponds and deposition sites. Stability and long-term behaviour of such deposits are typically studied in short-term laboratory experiments that cannot describe nor predict long-term changes taking place in these materials. Here, we study long-term (>40 years) transformations, in highly alkaline conditions, of the Ca-rich ash deposit in Estonia composed of oil shale processing residues from the Eesti power plant. Detailed mineralogical, chemical and micromorphological analyses using X-ray diffraction, X-ray fluorescence, 29Si nuclear magnetic resonance, scanning electron microscopy and other methods were applied in order to identify the composition of the waste with a focus on formation and transformation of semicrystalline phases in the deposit. The results show progressive formation of calcium-silicate-hydrate (C-S-H) type phase at the expense of silicate minerals and amorphous glass phases with increasing depth and age of the sediments, from about 25% in the upper part of the depository to over 60% in the oldest-deepest part. This demonstrates that over time the high alkalinity of the ash is responsible for initiating natural alkali-activation. The formation of C-S-H-type phases increases the mechanical strength of the sediment and ensures long-term stability of waste deposits. These findings may encourage the use of these ashes in binder or other construction material production or as construction aggregates.
- Published
- 2018
36. Single-crystal growth of Cu4(OH)6BrF and universal behavior in quantum spin liquid candidates synthetic barlowite and herbertsmithite
- Author
-
Ivo Heinmaa, C. Hoffmann, Z. A. Kelly, Christopher Pasco, Tyrel M. McQueen, Benjamin A. Trump, Raivo Stern, and T. Thao Tran
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Single crystal growth ,Specific heat ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic susceptibility ,Crystallography ,Lattice (order) ,0103 physical sciences ,engineering ,General Materials Science ,Orthorhombic crystal system ,Herbertsmithite ,Quantum spin liquid ,010306 general physics ,0210 nano-technology ,Ground state - Abstract
Synthetic barlowite, $\mathrm{C}{\mathrm{u}}_{4}{(\mathrm{OH})}_{6}\mathrm{BrF}$, has emerged as a new quantum spin liquid (QSL) host, containing kagom\'e layers of $S=1/2\mathrm{C}{\mathrm{u}}^{2+}$ ions separated by interlayer $\mathrm{C}{\mathrm{u}}^{2+}$ ions. Similar to synthetic herbertsmithite, $\mathrm{ZnC}{\mathrm{u}}_{3}{(\mathrm{OH})}_{6}\mathrm{C}{\mathrm{l}}_{2}$, it has been reported that $\mathrm{Z}{\mathrm{n}}^{2+}$ substitution for the interlayer $\mathrm{C}{\mathrm{u}}^{2+}$ induces a QSL ground state. Here we report a scalable synthesis of single crystals of $\mathrm{C}{\mathrm{u}}_{4}{(\mathrm{OH})}_{6}\mathrm{BrF}$. Through x-ray, neutron, and electron diffraction measurements coupled with magic angle spinning $^{19}\mathrm{F}$ and $^{1}\mathrm{H}$ NMR spectroscopy, we resolve the previously reported positional disorder of the interlayer $\mathrm{C}{\mathrm{u}}^{2+}$ ions and find that the structure is best described in the orthorhombic space group, Cmcm, with lattice parameters $a=6.665(13)\AA{},b=11.521(2)\phantom{\rule{0.16em}{0ex}}\AA{},c=9.256(18)\phantom{\rule{0.16em}{0ex}}\AA{}$, and an ordered arrangement of interlayer $\mathrm{C}{\mathrm{u}}^{2+}$ ions. Infrared spectroscopy measurements of the O---H and F---H stretching frequencies demonstrate that the orthorhombic symmetry persists upon substitution of $\mathrm{Z}{\mathrm{n}}^{2+}$ for $\mathrm{C}{\mathrm{u}}^{2+}$. Specific heat and magnetic susceptibility measurements of Zn-substituted barlowite, $\mathrm{Z}{\mathrm{n}}_{\mathrm{x}}\mathrm{C}{\mathrm{u}}_{4\ensuremath{-}\mathrm{x}}{(\mathrm{OH})}_{6}\mathrm{BrF}$, reveal striking similarities with the behavior of $\mathrm{Z}{\mathrm{n}}_{\mathrm{x}}\mathrm{C}{\mathrm{u}}_{4\ensuremath{-}\mathrm{x}}{(\mathrm{OH})}_{6}\mathrm{C}{\mathrm{l}}_{2}$. These parallels imply universal behavior of copper kagom\'e lattices even in the presence of small symmetry-breaking distortions. Thus, synthetic barlowite demonstrates universality of the physics of synthetic $\mathrm{C}{\mathrm{u}}^{2+}$ kagom\'e minerals and furthers the development of real QSL states.
- Published
- 2018
37. Naturally tuned quantum critical point in the S=1 kagomé YCa3(VO)3(BO3)4
- Author
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A. Leitmae, A. Z. Sharma, Ivo Heinmaa, Haidong Zhou, Yiming Qiu, Raivo Stern, Ryan Sinclair, Chris Wiebe, and H. J. Silverstein
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Materials science ,Spin glass ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Spins ,Order (ring theory) ,engineering.material ,Neutron scattering ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Magnetization ,Quantum critical point ,0103 physical sciences ,engineering ,Condensed Matter::Strongly Correlated Electrons ,General Materials Science ,Herbertsmithite ,010306 general physics ,Ground state - Abstract
Although $S=1/2$ kagom\'e systems have been intensely studied theoretically, and within the past decade been realized experimentally, much less is known about the $S=1$ analogs. While the theoretical ground state is still under debate, it has been found experimentally that $S=1$ kagom\'e systems either order at low temperatures or enter a spin glass state. In this work, ${\mathrm{YCa}}_{3}{(\mathrm{VO})}_{3}{({\mathrm{BO}}_{3})}_{4}$ (YCVBO) is presented, with trivalent vanadium. Owing to its unusual crystal structure, the metal-metal bonding is highly connected along all three crystallographic directions, atypical of other kagom\'e materials. Using neutron scattering it is shown that YCVBO fails to order down to at least 50 mK and exhibits broad and dispersionless excitations. $^{11}\mathrm{B}$ NMR provides evidence of fluctuating spins at low temperatures while dc magnetization shows critical scaling that is also observed in systems near a quantum critical point such as Herbertsmithite, despite its insulating nature and $S=1$ magnetism. The evidence shown indicates that YCVBO is naturally tuned to be a quantum disordered magnet in the limit of $T=0$ K.
- Published
- 2018
38. Zeta Potential of Beta Zeolites: Influence of Structure, Acidity, pH, Temperature and Concentration
- Author
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Tapio Salmi, Dmitry Yu. Murzin, Ivo Heinmaa, Kari Eränen, Päivi Mäki-Arvela, Atte Aho, Vladimir M. Gun’ko, Narendra Kumar, Zuzana Vajglová, and Xuan Liu
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Magnetic Resonance Spectroscopy ,Static Electricity ,Pharmaceutical Science ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Article ,Analytical Chemistry ,Catalysis ,Metal ,lcsh:QD241-441 ,chemistry.chemical_compound ,zeta potential ,Physisorption ,lcsh:Organic chemistry ,X-Ray Diffraction ,Drug Discovery ,Pyridine ,Zeta potential ,Physical and Theoretical Chemistry ,Fourier transform infrared spectroscopy ,Organic Chemistry ,Temperature ,Oxides ,Hydrogen-Ion Concentration ,021001 nanoscience & nanotechnology ,Microstructure ,0104 chemical sciences ,Chemical engineering ,chemistry ,Chemistry (miscellaneous) ,zeolites ,beta ,visual_art ,X-ray crystallography ,visual_art.visual_art_medium ,Zeolites ,Molecular Medicine ,0210 nano-technology ,Acids - Abstract
Measurements of the zeta potential of solid heterogeneous supports are important for preparation of metal supported catalysts and for shaping zeolites into extrudates. In the current work, different types of heterogeneous support materials such as SiO2, Al2O3, and a range of beta zeolites of different silica- to-alumina ratio were analysed. It was observed that parameters such as temperature, pH and acidity significantly affect the zeta potential. In several instances, depending on the materials’ acidity and microstructure, maxima in zeta potential were observed. The solid materials were thoroughly characterized using XRD, SEM, EDX, TEM, nitrogen physisorption, Al-NMR and FTIR with pyridine before zeta potential measurements.
- Published
- 2018
39. Mechanical reinforcement of electrospun poly(vinyl alcohol) by α-FeOOH nanowires
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Andris Šutka, Anna Šutka, Martin Järvekülg, Krisjanis Smits, Martin Timusk, Uno Mäeorg, and Ivo Heinmaa
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Vinyl alcohol ,Materials science ,Polymers and Plastics ,Composite number ,Nanowire ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electrospinning ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Nanofiber ,Ultimate tensile strength ,NATURAL SCIENCES:Physics [Research Subject Categories] ,Materials Chemistry ,Ceramics and Composites ,Composite material ,0210 nano-technology ,Glass transition ,Elastic modulus - Abstract
The authors kindly acknowledge the financial support of the Estonian Research Council for the post-doctoral research grants of personal research funding in projects PUT1096 and PUTJD578 as well as Institutional Research Funding Projects, IUT20-17, and IUT23-7., We report the mechanical performance of α‐FeOOH nanowire reinforced poly(vinyl alcohol) (PVA) composite nanofiber mat, fabricated using straightforward aqueous processing methods. Goethite (α‐FeOOH) nanocrystals have a high elastic modulus and –OH rich surface, ensuring strong interactions with hydrophilic polymers and effective reinforcement. Needle‐less electrospinning resulted in alignment of the nanowires along fibre axis, as confirmed by transmittance electron microscopy studies. Produced composite PVA nanofibers containing 10 wt% goethite nanoparticles exhibited an outstanding fivefold increase in Young's modulus and 2.5‐fold improvement of tensile strength compared to mats of neat PVA. The addition of α‐FeOOH had a significant influence on glass transition temperature indicating formation of interphase regions around nanowire inclusions. Observed properties are explained by nanowire grafting in the precursor solution, extensive interactions between the adsorbed PVA chains and the matrix and percolation of interphase regions at 10 wt% α‐FeOOH., Estonian Research Council PUT1096 and PUTJD578; Institutional Research Funding Projects, IUT20-17, and IUT23-7; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²
- Published
- 2018
- Full Text
- View/download PDF
40. Covalent fixation of boron in wood through transesterification with vinyl ester of carboxyphenylboronic acid
- Author
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Mohamed Jebrane and Ivo Heinmaa
- Subjects
040101 forestry ,0106 biological sciences ,Materials science ,Vinyl ester ,chemistry.chemical_element ,04 agricultural and veterinary sciences ,Transesterification ,01 natural sciences ,Catalysis ,Biomaterials ,Potassium carbonate ,chemistry.chemical_compound ,chemistry ,Covalent bond ,010608 biotechnology ,Reagent ,Polymer chemistry ,Vinyl acetate ,0401 agriculture, forestry, and fisheries ,Organic chemistry ,Boron - Abstract
Vinyl ester of 4-carboxyphenylboronic acid has been synthesized and tested as reactive reagent for permanent fixation of boron in wood based on an improved approach described previously. The essence of the method is a covalent incorporation of the boron compound via transesterification between wood hydroxyl groups and vinyl ester containing boron. The synthesis of this vinyl ester was accomplished by exchange reaction of vinyl acetate with 4-carboxyphenylboronic acid. The obtained vinyl ester of carboxyphenylboronic acid was characterized by FTIR and 1H-, and 13C-NMR spectroscopy. The covalent fixation of boron to wood’s hydroxyl groups was achieved through potassium carbonate (K2CO3) catalyzed transesterification of the vinyl ester containing boron. The transesterification was confirmed by weight percentage gain (WPG) calculation, curcumin staining, FTIR, and 13C CP-MAS NMR spectroscopy. The efficiency of the reaction improved with increasing temperature and reaction time.
- Published
- 2015
41. A route to produce renewable diesel from algae: Synthesis and characterization of biodiesel via in situ transesterification of Chlorella alga and its catalytic deoxygenation to renewable diesel
- Author
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Annika Smeds, Carolina Vieira Viegas, Donato A.G. Aranda, Imane Hachemi, Atte Aho, Jarl Hemming, Suely Pereira Freitas, Narendra Kumar, Dmitry Yu. Murzin, Débora Cristina da Silva Pereira, Ivo Heinmaa, Päivi Mäki-Arvela, and Filipe Batista Fontes
- Subjects
Biodiesel ,biology ,General Chemical Engineering ,Organic Chemistry ,Vegetable oil refining ,Energy Engineering and Power Technology ,Transesterification ,biology.organism_classification ,Catalysis ,Chlorella ,chemistry.chemical_compound ,Fuel Technology ,chemistry ,Biodiesel production ,Organic chemistry ,Methanol ,Hydrodeoxygenation - Abstract
In situ transesterification of Chlorella alga was performed using 5–20 wt% sulfuric acid as a catalyst at either 60 or 100 °C. The maximum ester yield in the range of 96–98% is comparative to the specification of ester content in biodiesel, 96%. A high excess of methanol was used in transesterification ensured also a high ester yield. The FAME was purified via adsorption of chlorophyll and carotenoids onto a clay. Properties of the purified biodiesel were investigated with several methods. The results showed that the Chlorella based biodiesel exhibits slightly lower oxidative and thermal stability compared to soybean based biodiesel due to the presence of polyunsaturated FAMEs. In addition to biodiesel, also the residual biomass was characterized showing that it contained sugars and proteins. An additional hydrogenation would increase the oxidative stability. Hydrodeoxygenation of Chlorella based biodiesel was also demonstrated over 5 wt% Ni–HY-80 zeolite with SiO2/Al2O3 ratio of 80 and with 5 wt% Pd/C at 300 °C and 30 bar in dodecane as a solvent. Ni–HY-80 was superior to Pd/C catalyst giving more than 95% yield of hydrocarbons.
- Published
- 2015
42. Isomerization of verbenol oxide to a diol with para-menthane structure exhibiting anti-Parkinson activity
- Author
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Markus Peurla, Atte Aho, Nariman F. Salakhutdinov, Päivi Mäki-Arvela, Narendra Kumar, Rainer Sjöholm, Dmitry Yu. Murzin, Konstantin P. Volcho, Annika Smeds, Alexandra Torozova, and Ivo Heinmaa
- Subjects
chemistry.chemical_compound ,Reaction mechanism ,chemistry ,Diol ,Pyridine ,Oxide ,Organic chemistry ,Physical and Theoretical Chemistry ,Oxetane ,Isomerization ,Catalysis ,Dimethylacetamide - Abstract
Isomerization of verbenol oxide to (1R, 2R, 6S)-3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol, which exhibits anti-Parkinson activity, has been investigated with large and medium pore zeolites, namely H-USY and H-ZSM-5 types of catalysts with different SiO2 to Al2O3 ratio in dimethylacetamide as a solvent. The catalysts were characterized with nitrogen adsorption, 27Al MAS NMR, pyridine desorption, XRD, SEM and TEM techniques. The main reaction product was the target diol with the highest selectivity of 52 % achieved with H-ZSM-5-23 (the last number corresponds to SiO2/Al2O3 ratio) at 49 % conversion of verbenol oxide. The catalyst deactivation was, however, extensive with medium pore zeolites, compared to large pore zeolites. The second highest selectivities to diol with H-USY-80 and H-ZSM-5-80 were about 47–50 mol% at 100 and 78 % of conversion, respectively, achieved at 140 °C within 3 and 5 h. The other main products were the corresponding cyclopentylhydroxyketone and oxetane. A reaction mechanism was proposed.
- Published
- 2015
43. 14N overtone NMR under MAS: signal enhancement using symmetry-based sequences and novel simulation strategies
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Harry Bentley, Philip T. F. Williamson, Ilya Kuprov, Ivo Heinmaa, Marina Carravetta, Ibraheem M. Haies, and James A. Jarvis
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Floquet theory ,Computer simulation ,Chemistry ,Overtone ,Analytical chemistry ,General Physics and Astronomy ,Nuclear magnetic resonance spectroscopy ,Physical and Theoretical Chemistry ,Spectral resolution ,Polarization (waves) ,Adiabatic process ,Spectral line ,Computational physics - Abstract
Overtone 14N NMR spectroscopy is a promising route for the direct detection of 14N signals with good spectral resolution. Its application is currently limited, however, by the absence of efficient polarization techniques for overtone signal enhancement and the lack of efficient numerical simulation techniques to aid in both the development of new methods and the analysis and interpretation of experimental data. In this paper we report a novel method for the transfer of polarization from 1H to the 14N overtone using symmetry-based R-sequences that overcome many of the limitations of adiabatic approaches that have worked successfully on static samples. Refinement of these sequences and the analysis of the resulting spectra have been facilitated through the development of an efficient simulation strategy for 14N overtone NMR spectroscopy of spinning samples, using effective Hamiltonians on top of Floquet and Fokker–Planck equations.
- Published
- 2015
44. Vacancy association energy in scandium doped ceria: 45Sc MAS NMR and 2D exchange spectroscopy study
- Author
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Helgi Kooskora, Reio Põder, Ivo Heinmaa, and Juhan Subbi
- Subjects
Arrhenius equation ,Chemistry ,Inorganic chemistry ,Doping ,chemistry.chemical_element ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,Activation energy ,Condensed Matter Physics ,Ion ,symbols.namesake ,Vacancy defect ,symbols ,Physical chemistry ,General Materials Science ,Scandium ,Two-dimensional nuclear magnetic resonance spectroscopy - Abstract
Oxygen vacancy exchange between Sc ions in 0.5% Sc-doped ceria Sc0.005Ce0.995O0.9975 is investigated by means of 2D exchange spectroscopy (EXSY). 45Sc NMR spectrum of Sc-doped ceria contains two peaks—one corresponding to Sc ions coupled with an oxygen vacancy (Sc-7), and the other corresponding to Sc ions in a regular lattice site surrounded by eight oxygen ions (Sc-8). The vacancy exchange between these two Sc sites generates the cross-peaks in the EXSY spectrum. Relative amplitudes of the cross-peaks provide direct values of the exchange frequency at a given temperature. Arrhenius analysis of the exchange frequency gives the activation energy Ea = 1.18 eV for the vacancy hopping between Sc sites. Most of this energy barrier is due to association energy which binds the vacancy to Sc3 +. Large dopant–vacancy association energy in Sc doped ceria is demonstrated by 45Sc NMR spectrum of La/Sc doubly doped sample, ScxLaxCe1 − 2xO2 − x, x = 0.005, where the only line of Sc-7 site shows that all vacancies are bound by Sc3 + ions.
- Published
- 2014
45. Biobased and Sustainable Alternative Route to Long-Chain Cellulose Esters
- Author
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Nasko Terziev, Mohamed Jebrane, and Ivo Heinmaa
- Subjects
Vinyl Compounds ,Polymers and Plastics ,Vinyl ester ,Bioengineering ,Oleic Acids ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Catalysis ,Biomaterials ,chemistry.chemical_compound ,Acyl chloride ,Pyridine ,Polymer chemistry ,Materials Chemistry ,Vinyl acetate ,Organic chemistry ,Cellulose ,chemistry.chemical_classification ,Esterification ,Fatty acid ,Esters ,Transesterification ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Long chain fatty acid ,0210 nano-technology - Abstract
Fatty acid cellulose esters (FACEs), which have been identified recently as sustainable film materials, are conventionally synthesized by the use of the reaction with acyl chloride/anhydride pyridine in the presence of LiCl/N,N-dimethylacetamide. In this study, we have developed a new synthetic route to FACEs using a vinyl ester of long chain fatty acid, which is an excellent biobased and highly reactive reagent, for the functionalization of cellulose. The developed method involves the synthesis of the long aliphatic fatty acid vinyl ester via a transition-metal-catalyzed transvinylation reaction between vinyl acetate and the fatty acid, followed by its subsequent reaction with cellulose to yield FACEs. In this work, we have used vinyl oleate as a model precursor to introduce the fatty acid chain to cellulose. The covalent grafting of the fatty acid chain to the free hydroxyl groups of cellulose was achieved through potassium carbonate (K2CO3)-catalyzed transesterification of vinyl oleate in the presence ...
- Published
- 2017
46. Low-Temperature High-Resolution Solid-State (cryoMAS) NMR of Han Purple BaCuSi2O6
- Author
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Ivo Heinmaa, E. Joon, Hiroyuki Nakamura, Alexander A. Tsirlin, Tsuyoshi Kimura, and Raivo Stern
- Subjects
Crystallography ,Structural phase ,Solid-state physics ,Condensed matter physics ,Chemistry ,Magnetism ,Magnetic frustration ,Solid-state ,High resolution ,Crystal structure ,Atomic and Molecular Physics, and Optics ,Spectral line - Abstract
We present low-temperature (low-T, sub-liquid-N2) high-speed high-resolution 29Si solid-state (cryoMAS) nuclear magnetic resonance studies on a model 2D-BEC quantum magnet BaCuSi2O6, known also as Han Purple. We observe broadened 29Si lines below the well-established 100 K structural phase transition confirming the existence of inhomogeneities at low temperatures. Interestingly, the low-T spectra of $${\mathrm{BaCuSi}}_{2}{\mathrm{O}}_{6}$$ closely resemble those of the novel compound Ba2CoSi2O6Cl2 taken at room temperature. This suggests that the Co compound features structural modulations or inhomogeneities already at room temperature. The low-T crystal structure and magnetism of $${\mathrm{BaCuSi}}_{2}{\mathrm{O}}_{6}$$ are more complex than previously believed, and deserve further investigation.
- Published
- 2014
47. Novel homogeneous gel fibers and capillaries from blend of titanium tetrabutoxide and siloxane functionalized ionic liquid
- Author
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Ants Lõhmus, Ivo Heinmaa, Ilmar Kink, Kristjan Saal, Valter Reedo, Raul Välbe, Andres Hoop, Kaija Põhako-Esko, Marta Tarkanovskaja, Uno Mäeorg, and Andres Krumme
- Subjects
Materials science ,Tetrafluoroborate ,Process Chemistry and Technology ,Inorganic chemistry ,Infrared spectroscopy ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,visual_art ,Alkoxide ,Ionic liquid ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Ionic conductivity ,Ceramic ,Hybrid material ,Sol-gel - Abstract
The preparation of ionogels by sol–gel processing has attracted much attention, because the final ceramic materials combine properties of both inorganic matrix (thermal and mechanical stability) and the ionic liquid (ionic conductivity). The aim of this study was to combine different imidazolium based ionic liquids (1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF 4 ], 1-butyl-3-methyl imidazolium tetrafluoroborate [BMIM][BF 4 ], 1-decyl-3-methylimidazolium tetrafluoroborate [DMIM][BF 4 ] and 1-methyl-3-[3′-(triethoxysilyl)propyl]imidazolium chloride MTICl) with titanium(IV) butoxide to prepare homogenous hybrid fibers through aqueous sol–gel reaction. The study showed that ionic liquid miscibility with metal alkoxide plays an important role in the preparation of homogenous fibers. Unlike simple imidazolium salts functionalized ionic liquid was dispersed homogenously in fibers, but the main advantage is derived from its chemical structure. New stable ionic liquid can be involved in sol–gel processes through ethoxy groups and as a result it associates with titanium alkoxide network by covalent bonding providing non-leaking ceramic hybrid material. Indirect and direct characterization studies of the product were carried out by energy-dispersive X-ray spectroscopy (EDX), silicon-29 nuclear magnetic resonance spectroscopy ( 29 Si NMR), scanning electron microscopy (SEM) and optical microscopies; also infrared spectra (IR) were recorded. Thermal analyses were performed by differential scanning calorimetry (DSC).
- Published
- 2014
48. Nuclear Magnetic Resonance of Hydrogen Molecules Trapped inside C70 Fullerene Cages
- Author
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Xuegong Lei, Ilya Kuprov, Judy Y.-C. Chen, Ivo Heinmaa, Salvatore Mamone, Mark Denning, Marina Carravetta, Yasujiro Murata, Maria Concistrè, Malcolm H. Levitt, Nicholas J. Turro, Yongjun Li, and Gary Wall
- Subjects
Carbon-13 NMR satellite ,010402 general chemistry ,01 natural sciences ,cryogenic nmr spectroscopy ,chemistry.chemical_compound ,Nuclear magnetic resonance ,0103 physical sciences ,Endohedral fullerene ,Physics::Atomic and Molecular Clusters ,C70 ,Physical and Theoretical Chemistry ,010306 general physics ,Anisotropy ,solid-state nmr spectroscopy ,Nuclear magnetic resonance spectroscopy ,Articles ,Carbon-13 NMR ,Atomic and Molecular Physics, and Optics ,3. Good health ,0104 chemical sciences ,NMR spectra database ,chemistry ,C70 fullerene ,endofullerenes ,Proton NMR ,quantum dynamics - Abstract
We present a solid-state NMR study of H2 molecules confined inside the cavity of C70 fullerene cages over a wide range of temperatures (300 K to 4 K). The proton NMR spectra are consistent with a model in which the dipole-dipole coupling between the ortho-H2 protons is averaged over the rotational/translational states of the confined quantum rotor, with an additional chemical shift anisotropy δ(H)(CSA)=10.1 ppm induced by the carbon cage. The magnitude of the chemical shift anisotropy is consistent with DFT estimates of the chemical shielding tensor field within the cage. The experimental NMR data indicate that the ground state of endohedral ortho-H2 in C70 is doubly degenerate and polarized transverse to the principal axis of the cage. The NMR spectra indicate significant magnetic alignment of the C70 long axes along the magnetic field, at temperatures below ~10 K.
- Published
- 2013
49. Solid state NMR spin-lattice relaxation investigation of oxygen dynamics in scandium doped ceria from 60 to 1073 K
- Author
-
Reio Põder, Juhan Subbi, Helgi Kooskora, and Ivo Heinmaa
- Subjects
Chemistry ,Relaxation (NMR) ,Inorganic chemistry ,Spin–lattice relaxation ,chemistry.chemical_element ,General Chemistry ,Activation energy ,Condensed Matter Physics ,Ion ,symbols.namesake ,Chemical physics ,Vacancy defect ,symbols ,General Materials Science ,Scandium ,Raman spectroscopy ,Characteristic energy - Abstract
Scandium spin dynamics in scandium doped ceria has been addressed first time through spin-lattice relaxation temperature dependence. Scandium spin-lattice relaxation temperature dependence in 0.5% scandium doped ceria matrix has been measured in the range between 60 K and 1073 K in magnetic fields 4.7 T and 8.5 T. The temperature dependence revealed four separate processes, two for 8-coordinated scandium and two for 7-coordinated scandium. However, none of these processes could be associated with oxygen vacancy hopping processes, directly responsible for ion conductivity in scandium doped ceria. We have established that for 7-Sc, the high temperature process is vacancy hopping around the scandium ion with activation energy 0.37 eV and the low temperature process is a Raman process involving local vibrations with characteristic energy 26 meV (208 cm − 1 ). For 8-Sc, the high temperature process is assigned to hopping between potential wells with different energy minima with apparent activation energy of 0.28 eV. We have shown that in this case the apparent activation energy of the process does not correspond to barrier height for hopping, but to barrier height plus energy difference between minima of corresponding wells. The low temperature process is again a Raman process involving local vibrations with even lower characteristic energy 20 meV (160 cm − 1 ).
- Published
- 2013
50. Mechanical properties of individual fiber segments of electrospun lignocellulose-reinforced poly(vinyl alcohol)
- Author
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Andris Šutka, Sergei Vlassov, Meeri Visnapuu, Ivo Heinmaa, Anna Šutka, Mikk Antsov, Uno Mäeorg, and Martin Järvekülg
- Subjects
Vinyl alcohol ,Yield (engineering) ,Nanocomposite ,Materials science ,Polymers and Plastics ,Modulus ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electrospinning ,0104 chemical sciences ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,chemistry ,Nanofiber ,Ultimate tensile strength ,Materials Chemistry ,Fiber ,Composite material ,0210 nano-technology - Abstract
The influence of lignocellulosic nanofibers (LCNF) additive on the inherent mechanical properties of submicron electrospun poly(vinyl alcohol) (PVA) fibers is reported. LCNF with a diameter of 25 ± 15 nm and a length of 220 ± 90 nm obtained from hemp shives were dispersed in aqueous PVA solutions to produce homogeneous nanocomposite fibers with 0, 5, and 10 w/w % LCNF loads in solid PVA. Tensile tests on mats show that LCNF additive causes up to sevenfold increase in stiffness and significant decrease in elongation at yield. AFM-based 3-point bending tests on single LCNF-doped fibers reveal up to 11.4 GPa Young's modulus in the diameter range of 300 to 500 nm, indicating a 2.4 times increase compared to neat PVA fibers. Mechanical properties of both neat and LCNF-doped PVA fibers are found to be strongly size-dependent at lower fiber diameters, with Young's modulus values exceeding 100 GPa at below 100 nm diameters. The results can be explained by extensive restructuration of hydrogen bonding network due to the LCNF additive. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44361.
- Published
- 2016
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