| 1. |
- Oberg, K., et al.
(författare)
-
Comparison of monolayer films of stearic acid and methyl stearate on an Al2O3 surface
- 2001
-
Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090. ; 397:1-2, s. 102-8
-
Tidskriftsartikel (refereegranskat)abstract
- Both stearic acid and methyl stearate chemisorbs onto an oxide surface of aluminum with an asymmetric coordination of the carboxylate group as concluded from infrared (IR) spectroscopy data. Similarities in the IR spectra of the films from the two compounds suggest that the ester is bonded in the same way as the acid, and that the ester therefore undergoes hydrolysis during the surface reaction. X-Ray photoelectron spectroscopy (XPS) and IR data are interpreted in terms of self-assembled monolayer formation and a more dense film from the carboxylic acid in comparison with that from the ester. (C) 2001 Elsevier Science B.V. All rights reserved.
|
|
| 2. |
- Adnan, Muhammad, et al.
(författare)
-
Fine Tuning the Optoelectronic Properties of Triphenylamine Based Donor Molecules for Organic Solar Cells
- 2017
-
Ingår i: Zeitschrift fur physikalische Chemie (Munchen. 1991). - : Walter de Gruyter GmbH. - 0942-9352 .- 2196-7156. ; 231:6, s. 1127-1139
-
Tidskriftsartikel (refereegranskat)abstract
- Geometrical parameters, electronic structures and photophysical properties of three new triphenylamine (TPA) and diphenylamine (DPA) based electron donor materials M1-M3 (for organic solar cells) have been investigated through density functional theory (DFT) methods at the B3LYP/6-31G(d) level of the theory. TPA and DPA are used as donor moieties due to their electron donating ability while benzothiazole, cyanide and cyanomethylacetate (CMA) moieties have been taken as acceptor moieties. The time dependent-DFT (TD-DFT) method has been employed [TD-B3LYP/6-31G (d)] for the computation of excited state properties in the gas phase and in solvent (chloroform). The polarization continuum model is applied for calculations in the solvent phase. The designed molecules exhibited broad absorption in the visible and near infra-red region of spectrum with respect to a reference molecule "R" of a similar class of compounds. Based on reorganization energies calculations, these materials could act as excellent hole transport materials.
|
|
| 3. |
- Albán Reyes, Diana Carolina, et al.
(författare)
-
Activation of dissolving cellulose pulp at low water content
- 2015
-
Ingår i: 4th EPNOE International Polysaccharide Conference.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mercerisation of cellulose by alkali treatment is the first step in modifying natural cellulose fibres into many commercial cellulosic materials. During treatment, the fiber transforms into a reactive and highly swollen material called alkali cellulose (Na-Cell). In case NaOH is washed out of the cellulose structure, Na-Cell turn into Cellulose II upon drying (Langan et al. 2001). The aim of the present study was to gain a better understanding of the mercerisation of dissolving cellulose pulp at low water content. This has been done by spraying NaOH onto milled cellulose in a kneader, then washing the cellulose to neutrality to stop the reaction. After drying the transformation degree to cellulose II was analysed. The experiments include variation of temperature (30-60°C), reaction time (5 and 25 min), [NaOH] (45-55%), and NaOH:Cellulose molar ratio (0.8- 1.8). A combination of NIR Raman imaging and multivariate data analysis have been used to study the transformation degree. To the authors’ knowledge, this is the first time the influence of NaOH: Cellulose molar ratio on the mercerisation process has been studied in a single model together with temperature, reaction time and [NaOH]. Our results indicate that increased NaOH: Cellulose molar ratio has a significant positive influence on transformation degree of dissolving cellulose pulp at low water content.
|
|
| 4. |
- Albán Reyes, Diana Carolina, et al.
(författare)
-
Activation of dissolving celluloses pulp for viscose and cellulose ether production
- 2016
-
Ingår i: The 7th workshop on cellulose, regenerated cellulose and cellulose derivatives. - Umeå ; Karlstad : Umeå university ; Karlstad university. ; , s. 29-30
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mercerisation of cellulose by alkali treatment is the most common procedure used to activate natural cellulose fibres into many commercial cellulosic materials. During mercerisation, the NaOH solution enters the cellulose fibres, transforming them into a swollen and a highly reactive material called alkali cellulose (Na-Cell). In case NaOH is completely washed out of the cellulose structure, Na-Cell turns into Cellulose II upon drying.Traditionally the cellulose is mercerised by suspending it in a 15-20 % NaOH solution. The result is a high (15-25 mol/mol) NaOH: Anhydroglucose molar ratio (r) and mercerisation in these conditions have been extensively studied. However, in modern production of cellulose ethers, the mercerisation conditions are often very different. The main reason is that any excess of water and OH--ions used during the mercerisation can later react with different chemicals in the process, thus forming unwanted by-products e.g. methanol. One way to avoid this kind of side reaction is by using low-water-content mercerisation conditions, i.e. low (r) = 0.8-1.8 mol/mol and high NaOH concentration (45-55% w/w). The traditional mercerisation is a suspension process while the cellulose during the latter process, i.e low-water-content mercerisation conditions, remains quite “dry”. Thus, although the chemical reaction principles of activation of cellulose for both viscose and cellulose ethers processes are the same, the activation conditions used are often very different. Therefore, the different dependencies of process parameters as well as any similarities between the processes are interesting.The presentation summarises the findings presented in two papers which described the influence of the different parameters on the mercerisation/activation of softwood Sulphite dissolving pulp in viscose production conditions (Albán Reyes et al. 2016) and cellulose derivatives production conditions (Albán Reyes et al.) respectively. In the individual studies this has been done by analysing the degree of transformation (DoT) of dissolving pulp to Na-cellulose (or more correctly cellulose II after washing and upon drying) as a function of simultaneous variation of [NaOH], temperature, and reaction time varied using design of experiment. Also the (r) was varied for samples mercerised at dry conditions. A combination of Raman imaging and multivariate data analysis have been used to study the DoT to Cellulose II.It was found that the mercerisation under the different conditions was dependent on different parameters. For traditional mercerisation, on the one hand, the temperature was shown to be important for the DoT and showed negative correlation with the data, while [NaOH] showed a positive correlation. On the other hand, at low-water-content mercerisation conditions the (r) was overall most important while the temperature showed no statistical importance in a Partial least squares analysis. Traditional mercerisation gave much higher DoT than the low-water-content mercerisation. Thus, the data for low-water-content mercerisation was further examined at the different (r). The same chemistry is always expected and the different influences of the parameters seen is understood and discussed in terms of the different physical reaction mechanisms.
|
|
| 5. |
- Albán Reyes, Diana Carolina, et al.
(författare)
-
The influence of different parameters on the mercerisation of cellulose for viscose production
- 2016
-
Ingår i: Cellulose. - : Springer Netherlands. - 0969-0239 .- 1572-882X. ; 23:2, s. 1061-1072
-
Tidskriftsartikel (refereegranskat)abstract
- A quantitative analysis of degree of transformation from a softwood sulphite dissolving pulp to alkalised material and the yield of this transformation as a function of the simultaneous variation of the NaOH concentration, denoted [NaOH], reaction time and temperature was performed. Samples were analysed with Raman spectroscopy in combination with multivariate data analysis and these results were confirmed by X-ray diffraction. Gravimetry was used to measure the yield. The resulting data were related to the processing conditions in a Partial Least Square regression model, which made it possible to explore the relevance of the three studied variables on the responses. The detailed predictions for the interactive effects of the measured parameters made it possible to determine optimal conditions for both yield and degree of transformation in viscose manufacturing. The yield was positively correlated to the temperature from room temperature up to 45 A degrees C, after which the relation was negative. Temperature was found to be important for the degree of transformation and yield. The time to reach a certain degree of transformation (i.e. mercerisation) depended on both temperature and [NaOH]. At low temperatures and high [NaOH], mercerisation was instantaneous. It was concluded that the size of fibre particles (mesh range 0.25-1 mm) had no influence on degree of transformation in viscose processing conditions, apparently due to the quick reaction with the excess of NaOH.
|
|
| 6. |
|
|
| 7. |
- Ans, Muhammad, et al.
(författare)
-
Designing of non-fullerene 3D star-shaped acceptors for organic solar cells
- 2019
-
Ingår i: Journal of Molecular Modeling. - : Springer. - 1610-2940 .- 0948-5023. ; 25:5
-
Tidskriftsartikel (refereegranskat)abstract
- The design and fabrication of solar cells have recently witnessed the exploration of non-fullerene-based acceptor molecules for higher efficiency. In this study, the optical and electronic properties of four new three-dimensional (3D) star-shaped acceptor molecules (M1, M2, M3, and M4) are evaluated for use as acceptor molecules in organic solar cells. These molecules contain a triphenylamine donor core with diketopyrrolopyrrole acceptor arms linked via a thiophene bridge unit. Molecules M1–M4 are characterized by different end-capped acceptor moieties, including 2-(5-methylene-6-oxo-5,6-dihydrocyclopenta-b-thiophen-4-ylidene)malononitrile (M1), 2-(2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (M2), 2-(5-methyl-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (M3), and 3-methyl-5-methylnene-thioxothiazolidin-4-one (M4). The properties of the newly designed molecules were compared with a well-known reference compound R, which was recently reported as an excellent acceptor molecule for organic solar cells. Molecules M1–M4 exhibit suitable frontier molecular orbital patterns for charge mobility. M2 shows maximum absorption (λmax) at 846.8 nm in dichloromethane solvent, which is ideal for the design of transparent solar cells. A strong electron withdrawing end-capped acceptor causes a red shift in absorption spectra. All molecules are excellent for hole mobility due to a lower value of λh compared to the reference R.
|
|
| 8. |
- Ans, Muhammad, et al.
(författare)
-
Designing Three‐dimensional (3D) Non‐Fullerene Small Molecule Acceptors with Efficient Photovoltaic Parameters
- 2018
-
Ingår i: ChemistrySelect. - : WILEY-VCH VERLAG GMBH. - 2365-6549. ; 3:45, s. 12797-12804
-
Tidskriftsartikel (refereegranskat)abstract
- Three dimensional (3D) acceptor‐donor‐acceptor (A−D‐A) type small molecules (M1, M2, M3 and M4) are theoretically investigated for optoelectronic properties. The designed molecules contain spirobifluorene as core unit linked with end capped acceptors through four four thieno‐[3,2‐b]Thiophene (TT) units. The end capped acceptors are (3‐methyl‐2‐thioxothiazolidin‐4‐one) (M1), 2‐(2‐ethylidene‐5,6‐difluoro‐3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile (M2), 2‐(3‐ethyl‐4‐oxothiazolidin‐2‐ylidine)malononitrile (M3) and 2‐(2‐ethylidene‐5,6‐dicyano‐3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile (M4). The photovoltaic parameters of the designed molecules are compared with the recently reported reference compound R. Among all designed molecules, M4 is a low energy gap material (2.28 eV), broad absorption which is attributed to excellent communication between strong electron withdrawing end capped acceptors through extended conjugation. All newly designed molecules have lower binding energy as compared to reference molecule R which results in higher exciton dissociation in excited state. The reorganization energy calculations indicate good charge transfer ability of the designed molecules. M4 shows the lowest λe (0.0022) value with respect to the reference molecule R (0.034) which signifies its enhanced electronic transport behavior. The calculated open circuit voltages (Voc) ranges from 1.97 to 2.36 eV, 2.11 to 2.49 eV and 1.9 eV to 2.28 eV with respect to three different well known donor materials PTB7‐Th, PBDB−T and P3HT, respectively.
|
|
| 9. |
- Ans, Muhammad, et al.
(författare)
-
Opto-electronic properties of non-fullerene fused-undecacyclic electron acceptors for organic solar cells
- 2019
-
Ingår i: Computational materials science. - : Elsevier. - 0927-0256 .- 1879-0801. ; 159, s. 150-159
-
Tidskriftsartikel (refereegranskat)abstract
- Due to limitations of fullerene based acceptor molecules for solar cell applications, research is recently diverted to explore non-fullerene acceptor molecules. In this regard, four new A-D-A type fused ring electron acceptor molecules (M1, M2, M3 and M4) are evaluated for their opto-electronic properties for transparent organic solar cells. These molecules contain strong electron donor undecacyclic linked with four different acceptor moieties, 2-(3-ethly-5-methylene-4-oxothiazolidin-2-yluidene)malononitrile (M1), 2-(5,6-dicyano-2-methylene-3-oxo -2,3-dihydroindene-1-ylidene)malononitrile (M2), 2-(5-methylene-6-oxo-tetrahydro-1H-cyclopenta-thiophene-4(5H)-ylidene)malononitrile (M3), and 3-ethyl-5-methylene-2-thioxothiazolidin-4-one (M4). The electronic and optical properties of these molecules are compared with the reference molecule R, which is recently reported as excellent non-fullerene based acceptor molecule. Among all molecules, M2 exhibits the maximum red shift where absorption appears 893.5 nm with B3LYP/6-31 + + G(d,p) level of theory due to highly extended conjugation between electron withdrawing end-capped acceptor moieties. The calculated Open circuit voltage (V-oc) of reference molecule R is 1.78 eV with donor polymer PTB7-Th while molecule M2 exhibits the V-oc value of 1.86 eV.
|
|
| 10. |
- Ans, Muhammad, et al.
(författare)
-
Spirobifluorene based small molecules as an alternative to traditional fullerene acceptors for organic solar cells
- 2019
-
Ingår i: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 94, s. 97-106
-
Tidskriftsartikel (refereegranskat)abstract
- Four new three-dimensional (3D) acceptor-acceptor-donor (A-A-D) type of small molecule acceptors (Ml, M2, M3 and M4) were designed for better optoelectronic properties in organic solar cells. These molecules contain spirobifluorene as a 3D core unit, flanked with 2,1,3- benzothiadiazole (BT) units linked with the end-capped acceptor groups 2-(4-oxo-4,5-dihydrocyclopenta-b-thiophene-6-ylidene)malononitrile (M1), 2-(3-oxo-2,3-dihydro-1H-indene-1-indene-1-ylidene)malononitrile (M2), 2-(5,6-difluoro-3-oxo-2,3-dihydroindene-1-ylidene) malononitrile (M3) and 2-(5,6-dimethyl-3-oxo-2,3-dihydroindene-1-ylidene)malononitrile (M4). The optoelectronic properties of M1 -M4 were compared with the well-known reference molecule R, which has the same central BT-spirobifluorene-BT structure as Ml-M4 but is end-capped with the 2-(2-dicyanomethylene)-3-ethyl-4-oxo-thiazolidin-5-ylidenemethyl group. Among these molecules, M3 has the most appropriate frontier molecular orbital diagram for optoelectronic properties as deduced from MPW1PW91 calculations and also shows the maximum absorption peak at longest wavelength (569 nm) by TD-MPW1PW91 calculations with a polarizable continuum model for chloroform solution. These properties are due to the strong electron-withdrawing end-capped acceptor group which causes a red shift in the absorption spectrum. Computed reorganization energies indicate that the electron mobilities for M1-M4 are higher compared to that of reference R.
|
|
| 11. |
-
Benchmark study of bond dissociation energy of Si-X (X=F, Cl, Br, N, O, H and C) bond using density functional theory (DFT)
- 2017
-
Ingår i: Journal of Molecular Structure. - : Elsevier. - 0022-2860 .- 1872-8014. ; 1143, s. 8-19
-
Tidskriftsartikel (refereegranskat)abstract
- A benchmark study of Bond Dissociation Energies (BDEs) of various chemical bonds is carried out by Density Functional theory (DFT) method. The aim of the present research study was to find out the best suited functional and basis set to calculate BDEs of selected bonds of silicon with halogens (F, Cl, Br), N, H, C and O. Six different functionals (CAM/B3LYP, B3LYP, B3PW91, PBEPBE, TPSSTPSS) were applied on 36 molecules of different nature. Furthermore, six different basis sets 3-21G, aug-cc-pVTZ, 6-31G, aug-cc-pVDZ, DGDZVP and DGDZVP2 were also applied on these molecules with the best suited functional CAM/B3LYP. After rigorous effort it can be safely said that the best basis set for calculating BDEs for Si H, Si-C, Si-N bonds using CAM-B3LYP functional is 3-21G and for Si-halogens,aug-cc-pVTZ was found to be best basis set.
|
|
| 12. |
- Boman, Patrik, et al.
(författare)
-
Bond shift and charge transfer dynamics in methylene- and dimethylsilyl-bridged dicyclooctatetraene dianions
- 2001
-
Ingår i: Journal of the Chemical Society Perkin Transactions 2. - : Royal Society of Chemistry (RSC). - 1472-779X .- 1364-5471. ; , s. 1130-8
-
Tidskriftsartikel (refereegranskat)abstract
- The rate constants for bond shift in dicyclooctatetraenylmethane (1), dicyclooctatetraenyldimethylsilane (2), and their dianions (12– and 22–) in [2H8]THF, have been determined from the temperature dependence of their 13C NMR linewidths. The corresponding parameters for intramolecular electron and cation transfer (charge transfer) between the dinegative and neutral rings have been measured by 13C NMR spin saturation transfer experiments for the dipotassium salts of 1 and 2. Selected structural features of the neutral compounds and the dianions are discussed on the basis of 13C NMR chemical shifts and ab initio molecular orbital calculations at the HF/6-31G* and HF/3-21G(*) levels of theory. Energy contributions to the ring flattening in the bond shift process are calculated by molecular mechanics methods. The measured rate constants for both bond shift and charge transfer are larger for the methylene-bridged dianion. Approximately half of this difference is due to the greater ease of gating (i.e., ring flattening and distortion to the bond shift transition state) in 12––2K+. A significant portion of the remainder is attributed to a greater inter-ring through-space interaction in 12–, although mediation by the cation and/or through-bridge interactions probably also contribute to some extent. A temperature-dependent differential 13C NMR line broadening is observed for the dianion ring carbons of the dipotassium salts. Possible mechanisms for this counterion-specific line broadening, which occurs only for carbons with large HOMO coefficients, are discussed.
|
|
| 13. |
- Carlsson, Marcus, et al.
(författare)
-
One-pot synthesis of trans mono- or diarylalkynyl substituted platinum(II) compounds with tertiary phosphine or phosphite ligands
- 2006
-
Ingår i: Organometallics. - : American Chemical Society (ACS). - 0276-7333 .- 1520-6041. ; 25:22, s. 5500-5502
-
Tidskriftsartikel (refereegranskat)abstract
- An efficient one-pot synthesis has been developed for preparation of trans-mono- or diarylalkynyl bisphosphine or bisphosphite Pt(II) compounds. In the procedure, the alkyne and the tertiary phosphorus ligands are mixed with PtCl2 in tetrahydrofuran and triethylamine solution. CuI is added for synthesis of disubstituted complexes, but the catalyst is not used for preparation of monosubstituted complexes. Microwave irradiation is preferably employed to give the trans-mono- or diarylalkynyl Pt(II) compound in short time and high yield.
|
|
| 14. |
- Carlsson, Marcus, 1976-
(författare)
-
Synthesis and optical characterization of optical power limiting platinum(II) acetylides
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Interactions between light and a molecule can result in reversible or irreversible changes in properties of both the light and the molecule. Of the many known interactions, nonlinear absorption is a process in which an intense light signal, for instance from a laser, can be moderated. This can be manifested either in a marked lowering of the light’s intensity or in reductions in fluctuations of its intensity. Such an effect is often termed ‘optical power limiting’ (OPL). High power lasers can be very dangerous since their high intensity can damage or destroy eyes and optical sensors. However, there are currently no adequate protective measures against lasers that cover the entire visible region and there is an increasing demand for new or improved OPL materials. Some of the most promising optical power limiting materials are substances that combine nonlinear optical properties with high transparency in normal light, but after activation by a laser beam, their light transmittance falls extremely rapidly via so-called self-activating mechanisms. The platinum(II) acetylides comprise one class of compounds with such properties. In this study, various OPL Pt(II) acetylides were synthesized and their nonlinear optical properties were characterized. The emphasis of the work was on preparation of the compounds, but in order to design organoplatinum chromophores for OPL, attempts were also made to obtain insight into the mechanisms of nonlinear absorption. The work was divided into two main parts. In the first the goal was to find compounds that are good optical limiters in solution. The possibility of isolating the chromophore site by dendron shielding and the effects of incorporating a thiophene ring into the organic molecular system were also explored. In addition, a new route for synthesizing these compounds was developed. The second part was focused on incorporating the most interesting compounds into solid materials. The preparation and characterization of Pt(II) acetylides with molecular groups for covalent attachment to a silica matrix via the solution gel approach is described.
|
|
| 15. |
|
|
| 16. |
|
|
| 17. |
- Chateau, Denis, et al.
(författare)
-
Silica hybrid sol-gel materials with unusually high concentration of Pt-organic molecular guests : Studies of luminescence and nonlinear absorption of light
- 2012
-
Ingår i: ACS Applied Materials and Interfaces. - Washington : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 4:5, s. 2369-2377
-
Tidskriftsartikel (refereegranskat)abstract
- The development of new photonic materials is a key step towards improvement of existing optical devices and for the preparation of a new generation of systems. Therefore synthesis of photonic hybrid materials with a thorough understanding and control of the microstructure-to-properties relationships is crucial. In this perspective, a new preparation method based on fast gelation reactions using simple dispersion of dyes without strong covalent bonding between dye and matrix has been developed. This new sol-gel method is demonstrated through synthesis of monolithic siloxane-based hybrid materials highly doped by various platinum(II) acetylide derivatives. Concentrations of the chromophores as high as 400 mM were obtained and resulted in unprecedented optical power limiting (OPL) performance at 532 nm of the surface-polished solids. Static and time-resolved photoluminescence of the prepared hybrid materials were consistent with both OPL data and previous studies of similar Pt(II) compounds in solution. The impacts of the microstructure and the chemical composition of the matrix on the spectroscopic properties, are discussed.
|
|
| 18. |
- Eliasson, Bengt
(författare)
-
Numerical simulation of kinetic effects in ionospheric plasma
- 2001
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, we study numerically the one-dimensional Vlasov equation for a plasma consisting of electrons and infinitely heavy ions. This partial differential equation describes the evolution of the distribution function of particles in the two-dimensional phase space (x,v). The Vlasov equation describes, in statistical mechanics terms, the collective dynamics of particles interacting with long-range forces, but neglects the short-range "collisional" forces. A space plasma consists of electrically charged particles, and therefore the most important long-range forces acting on a plasma are the Lorentz forces created by electromagnetic fields.What makes the numerical solution of the Vlasov equation to a challenging task is firstly that the fully three-dimensional problem leads to a partial differential equation in the six-dimensional phase space, plus time, making it even hard to store a discretized solution in the computer's memory. Secondly, the Vlasov equation has a tendency of structuring in velocity space (due to free streaming terms), in which steep gradients are created and problems of calculating the v (velocity) derivative of the function accurately increase with time.The method used in this thesis is based on the technique of Fourier transforming the Vlasov equation in velocity space and then solving the resulting equation. We have developed a method where the small-scale information in velocity space is removed through an outgoing wave boundary condition in the Fourier transformed velocity space. The position of the boundary in the Fourier transformed variable determines the amount of small-scale information saved in velocity space.The numerical method is used to investigate a phenomenon of tunnelling of information through an ionospheric layer, discovered in experiments, and to assess the accuracy of approximate analytic formulæ describing plasma wave dispersion. The numerical results are compared with theoretical predictions, and further physical experiments are proposed.
|
|
| 19. |
- Eliasson, Bengt, 1965-
(författare)
-
Numerical Vlasov–Maxwell Modelling of Space Plasma
- 2002
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Vlasov equation describes the evolution of the distribution function of particles in phase space (x,v), where the particles interact with long-range forces, but where shortrange "collisional" forces are neglected. A space plasma consists of low-mass electrically charged particles, and therefore the most important long-range forces acting in the plasma are the Lorentz forces created by electromagnetic fields. What makes the numerical solution of the Vlasov equation a challenging task is that the fully three-dimensional problem leads to a partial differential equation in the six-dimensional phase space, plus time, making it hard even to store a discretised solution in a computer’s memory. Solutions to the Vlasov equation have also a tendency of becoming oscillatory in velocity space, due to free streaming terms (ballistic particles), in which steep gradients are created and problems of calculating the v (velocity) derivative of the function accurately increase with time. In the present thesis, the numerical treatment is limited to one- and two-dimensional systems, leading to solutions in two- and four-dimensional phase space, respectively, plus time. The numerical method developed is based on the technique of Fourier transforming the Vlasov equation in velocity space and then solving the resulting equation, in which the small-scale information in velocity space is removed through outgoing wave boundary conditions in the Fourier transformed velocity space. The Maxwell equations are rewritten in a form which conserves the divergences of the electric and magnetic fields, by means of the Lorentz potentials. The resulting equations are solved numerically by high order methods, reducing the need for numerical over-sampling of the problem. The algorithm has been implemented in Fortran 90, and the code for solving the one-dimensional Vlasov equation has been parallelised by the method of domain decomposition, and has been implemented using the Message Passing Interface (MPI) method. The code has been used to investigate linear and non-linear interaction between electromagnetic fields, plasma waves, and particles.
|
|
| 20. |
- Forsberg, Bertil, et al.
(författare)
-
Luftföroreningshalters relation till fibrinogenhalten i blod
- 2002
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Som ett specialprojekt om hälsorelaterad miljöövervakning har studerats om hälsoundersökningsdata avseende fibrinogenhalt i blod kan användas som en indikator på luftföroreningspåverkan. Bakgrunden är att det under senare år har publicerats flera studier i vilka samband konstaterats mellan dygnets eller de senaste dygnens luftföroreningshalt (främst partiklar eller avgaskomponenter) och det dygnsvisa antalet dödsfall eller sjukhusinläggningar p g a hjärtsjukdom. Mekanismerna bakom effekterna är inte helt klarlagda, men mycket talar för att en mekanism kan vara kroppens inflammationssvar som inducerar förändringar i blodets koaguleringsbenägenhet. Fibrinogen är en av de viktigaste faktorerna bakom blodets viskositet. Ökad fibrinogenhalt i blodplasma har tidigare konstaterats dels i samband med en luftföroreningsepisod i Tyskland och när hälsoundersökningsdata från London korrelerats till kvävedioxidhalten dygnet innan blodprovet togs. I denna undersökning har vi använt data om fibrinogenhalten (g/l) i blodprover som tagits i den befolkningsbaserade MONICA-undersökningen i Norr- och Västerbotten under januari-april 1990 och 1994, och utifrån undersökningsdatum påfört individerna uppgifter om halten av ozon respektive sot samma och intilliggande dygn. För närmare 3400 personer vars blodprov kunnat sammankopplas med aktuell ozonhalt, konstaterar vi att fibrinogenhalten ökar med stigande ozonvärde. Sambandet är statistiskt säkerställt vid en analys med hänsyn till individfaktorer av betydelse för fibrinogenhalten. En ökning av ozonhalten med 50 μg/m3 (från 10:e till 90:e percentilen) leder till en i genomsnitt 3 % ökad fibrinogenhalt.
|
|
| 21. |
- Glimsdal, Eirik, et al.
(författare)
-
Excited States and Two-Photon Absorption of Some Novel Thiophenyl Pt(II)-Ethynyl Derivatives
- 2007
-
Ingår i: JOURNAL OF PHYSICAL CHEMISTRY A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 111, s. 244-50
-
Tidskriftsartikel (refereegranskat)abstract
- The photophysical characterization of two new compounds related to bis((4-(phenylethynyl)phenyl)ethynyl)bis(tributylphosphine)platinum(II), here abbreviated Pt1, is reported. For the first new compound ATP1, the inner phenyl rings (closer to the Pt atom) in Pt1 are replaced by thiophene rings bridging at the 2,5-positions. In compound ATP2, the outer phenyl groups are replaced by thiophene rings bonded at the 2-position. Specifically, we report on the fluorescence quantum yield, two-photon absorption, triplet decay times and two-photon absorption induced emission spectra of the molecules in THF solutions. The results were compared with those of Pt1 and Pt1 capped with an acetonide-protected 2,2-bis(methylol)propionic acid (bis-MPA) ester group (Pt1-G1). The photophysical properties of the organic dye 7-(diethylamino)coumarin (Coumarin 110) were determined and used as a reference material. The two-photon absorption cross section around 720-740 nm of ATP1 and ATP2 was found to be of the same order of magnitude as for Pt1-G1, i.e., between 5 and 10 GM, but slightly larger for ATP1 than for ATP2 (1 GM = 1 Goppert-Mayer = 10(-50) (cm(4) s)/photon). The fluorescence decay time of all compounds was found to be very short (subnanosecond) with quantum yields 0.0045, 0.0007, 0.0011 and 0.0020 for ATP1, ATP2, Pt1-G1 and Pt1, respectively, measured at excitation wavelength 373 nm. Just as Pt1 and Pt1-G1, both thiophenyl derivatives showed large intersystem crossing capabilities and phosphorescence, characteristic for a triplet state that can enhance the nonlinear absorption and optical power limiting by triplet state absorption. The phosphorescence emission of the thiophenyl derivatives was red-shifted in comparison with Pt1 and Pt1-G1, and the phosphorescence decay times were on the order of 200-500 ns, as for the Pt1 compound.
|
|
| 22. |
- Glimsdal, Eirik, et al.
(författare)
-
Luminescence, singlet oxygen production, and optical power limiting of some diacetylide platinum(II) diphosphine complexes
- 2010
-
Ingår i: Journal of Physical Chemistry A. - : ACS Publications. - 1089-5639 .- 1520-5215. ; 114:10, s. 3431-3442
-
Tidskriftsartikel (refereegranskat)abstract
- A series of four new trans-diphosphine Pt(II) diacetylide complexes, with a thiophene and two benzenoid rings in each acetylide ligand, have been synthesized and characterized with respect to optical absorption, spectrally and time-resolved luminescence, and optically nonlinear properties such as two-photon absorption cross section and optical power limiting. Density functional theory (DFT) calculations of a few ground state conformations of three Pt(II) diacetylide structures showed similar total energy for each geometry-optimized rotamer but some differences in the vertical excitation energies and in the ligand-to-metal charge-transfer character. The wavelengths of the calculated excitations were found to be red-shifted compared with peaks in the optical absorption spectra, but the general trends and shifts of wavelengths between the different structures are well reproduced. Static emission spectra for degassed samples in THF solution of the larger compounds showed small Stokes shifts and low fluorescence quantum yields, indicating fast intersystem crossing to the triplet manifold. More pronounced differences between the compounds were displayed in the phosphorescence data, in terms of spectral emission wavelengths and decay times. For instance, the phosphorescence decay of the compound with the thiophene ring close to the Pt center was found to be significantly faster than for the other compounds. A possible relationship between triplet lifetime and conformation of the compounds is discussed. It was also demonstrated that the quenching of the excited triplet states in air-saturated samples involves energy transfer to the oxygen triplet state, and subsequent generation of singlet oxygen showing the typical emission at approximately 1275 nm. The amount of produced singlet oxygen followed the phosphorescence yields of the solute molecules. Two-photon absorption cross sections (sigma(2)) were measured and showed values on the order of 10 GM at 780 nm for all compounds. Optical power limiting measurements of the new complexes in THF using 5 ns pulses, showed only slightly better performance at the wavelength of 532 nm compared to that of similar platinum compounds with only two aryl rings in each ligand. At 600 nm the complexes with three aryl rings were significantly better optical limiters than the smaller compounds with two aryl rings in the ligands.
|
|
| 23. |
- Glimsdal, Eirik, et al.
(författare)
-
Triplet excited states of some thiophene and triazole substituted platinum(II) acetylide chromophores
- 2009
-
Ingår i: Journal of Physical Chemistry A. - Washington : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 113:14, s. 3311-3320
-
Tidskriftsartikel (refereegranskat)abstract
- The photophysical properties of a series of platinum(II) acetylide compounds (trans-Pt(PBu(3))(2)(CC-R)(2)) with the R group consisting of two or three aryl rings (phenyl, phenyl/thiophenyl, phenyl/triazolyl) linked together with ethynyl groups were systematically investigated. Four new structurally similar compounds are reported with: (i) a bithiophene unit in the ligands, (ii) methyl or (iii) methoxy substituents on the aryl ring ligands that promote a more twisted conformation along the long axis of the molecule, and (iv) with two different alkynylaryl ligands giving rise to an asymmetric substitution with respect to the photoactive metal ion center. The spectroscopic studies include optical absorption, spectrally and time-resolved luminescence, as well as transient absorption spectra. The ground-state UV absorption between 300 and 420 nm gave rise to fluorescence with quantum efficiencies in the range of 0.1-1% and efficient intersystem crossing to triplet states. Phosphorescence decay times were in the order of 10-500 mus in oxygen-evacuated samples. The triplet states also lead to strong broadband triplet-triplet absorption between 400 and 800 nm. The complex with asymmetric substitution was found to populate two triplet states of different structure and energy.
|
|
| 24. |
- Gromov, Sergey P, et al.
(författare)
-
Synthesis, Structure, Spectroscopic Studies, and Complexation of Novel Crown Ether Butadienyl Dyes
- 2002
-
Ingår i: Helvetica Chimica Acta. ; 85:1, s. 60-81
-
Tidskriftsartikel (refereegranskat)abstract
- Butadienyl dyes of the benzothiazole series with various fragments of benzocrown ethers 1a-c were synthesized for the first time. The structures and spectral properties of crown-containing butadienyl dyes and their complexes with alkali and alkaline-earth metal cations were studied by X-ray diffraction analysis and 1H-NMR, UV/VIS, and resonance Raman spectroscopy. To interpret the experimental results, quantum-chemical calculations were performed. In the case of Sr2+ and Ba2+ ions, the formation of strong sandwich complexes [M(1b)2]2+ of an unusual structure involving stacking interactions was established; the dye molecules are arranged one above another in the complex according to the head-to-head' pattern.
|
|
| 25. |
- Gräsvik, John, et al.
(författare)
-
Halogen-free ionic liquids and their utilization as cellulose solvents
- 2012
-
Ingår i: Journal of Molecular Structure. - : Elsevier. - 0022-2860 .- 1872-8014. ; 1028, s. 156-163
-
Tidskriftsartikel (refereegranskat)abstract
- This work demonstrates a novel synthesis route to halogen-free ionic liquids. A one-pot synthetic reaction route avoiding the use of toxic and high-energetic alkyl halides was developed to reduce the environmental impact of the synthesis process of ionic liquids. However, the elimination of halogens and alkyl halides in the preparation of ionic liquids is not just an environmental issue: the aforementioned species are also among the most common and persistent contaminants in today’s Ionic Liquids (ILs). Thus, this paper introduces a range of quaternized nitrogen based ionic liquids, including both aromatic and non-aromatic components, all prepared without alkyl halides in any step of the process. Moreover, bio-renewable precursors such as (bio-)alcohols and carboxylic acids were employed as anion sources and alkylation media, thus avoiding halogen contamination or halogen-containing anions. The IL’s prepared were designed to dissolve cellulose, some of which was included in a cellulose dissolution study using a sulphite cellulose from the company Domsjö.
|
|
| 26. |
- Gräsvik, John, 1977-
(författare)
-
Ionic liquids in bio-refining : synthesis and applications
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fossil fuel resources are not limitless so alternative renewable recourses are needed to fill the void that inevitably will be created once the supplies of this resource start do dwindle. Biomass has the potential to fill this void. Today only a small part of the world annual production of biomass is utilized by humankind, while the rest is allowed to decay naturally. To utilize this renewable resource in the production of fuel and chemicals, the so called bio-refineries specialized in fractionation and making use of all component of the biomass are needed. Ionic liquids could aid in this task.Ionic liquids (ILs) have shown great potential in the field of biomass processing in general and in the pretreatment of (ligno)-cellulose in particular. However, a few things need to be addressed before any large-scale processing can be considered: Finding new routes for IL synthesis that make "on-site" production possible; Investigation into the challenges facing IL pretreatment of (ligno)-cellulose such as possible depolymerization of cellulosic material during the pretreatment and investigating what influence different ILs have on the pretreatment of cellulosic material by methods like enzymatic hydrolysis.This work aims to address these issues and will present a route for IL synthesis making use of alcohols and carboxylic acids both commonly found in a biorefinery. Some of these ILs have also been tested for their ability of dissolve cellulose. Furthermore, this work will address the possibilities but also challenges upon IL-mediated (ligno)-cellulose processing. This includes investigating several ILs and their efficiency as a pretreatment solvent for enzymatic hydrolysis; these studies involve a large variety of different cellulosic materials. This work demonstrated that depolymerization during the IL pretreatment is a possibility and that this can complicate the recovery processes. Furthermore, this work gives guidance into what type of ILs might be suited as pretreatment solvents for different cellulosic materials, including amorphous and crystalline cellulose, processed and native lignocellulose, different types of wood samples and hemicellulose.
|
|
| 27. |
-
Hybrid Materials for Optical Limiting
- 2005
-
Proceedings (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Optical limiting materials based on alkynyl platinum derivatives and thiacalixarenes were produced using the sol-gel process. The molecular species were grafted to the matrix (class II hybrid) in order to maximise the concentration and the stability of the material. Broadband optical limiting performances in the visible wavelength region was observed in the prepared materials. Thermomechanical characterisation of the matrix will also be discussed.
|
|
| 28. |
- Iqbal, Javed, et al.
(författare)
-
An arylene-vinylene based donor-acceptor-donor small molecule for the donor compound in high-voltage organic solar cells
- 2016
-
Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 155, s. 348-355
-
Tidskriftsartikel (refereegranskat)abstract
- A donor-acceptor-donor (D-A-D) molecule has been designed and synthesized for use as the electron donating material in solution-processed small-molecule organic solar cells (OSCs). The D-A-D molecule comprises a central electron-accepting (2Z,2'Z)-2,2'-(2,5-bis(octyloxy)-1,4-phenylene)bis(3-(thiophen-2-yl)acry lonitrile) (ZOPTAN) core, which is chemically connected to two peripheral and electron-donating triphenylamine (TPA) units. The ZOPTAN-TPA molecule features a low HOMO level of -5.2 eV and an optical energy gap of 2.1 eV. Champion OSCs based on a solution-processed and non-annealed active material blend of [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) and ZOPTAN-TPA in a mass ratio of 2:1 exhibits a power conversion efficiency of 1.9% and a high open-circuit voltage of 1.0 V.
|
|
| 29. |
- Irfan, Muhammad, et al.
(författare)
-
Benchmark study of UV/Visible spectra of coumarin derivatives by computational approach
- 2017
-
Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 1130, s. 603-616
-
Tidskriftsartikel (refereegranskat)abstract
- A benchmark study of UV/Visible spectra of Simple coumarins and Furanocoumarins derivatives was conducted by employing the Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT) approaches. In this study the geometries of ground and excited states, excitation energy and absorption spectra were estimated by using the DFT functional CAM-B3LYP, WB97XD, HSEH1PBE, MPW1PW91 and TD-B3LYP with 6-31 + G (d,p) basis set. CAM-B3LYP functional was found to have close agreement with the experimental values of Furranocoumarin class of coumarins while MPW1PW91 gave close results for simple coumarins. This study provided an insight about the electronic characteristics of the selected compounds and provided an effective tool for developing and designing the better UV absorber compounds.
|
|
| 30. |
- Irfan, Muhammad, et al.
(författare)
-
Design of donor-acceptor-donor (D-A-D) type small molecule donor materials with efficient photovoltaic parameters
- 2017
-
Ingår i: International Journal of Quantum Chemistry. - : WILEY. - 0020-7608 .- 1097-461X. ; 117:10
-
Tidskriftsartikel (refereegranskat)abstract
- Four Donor-Acceptor-Donor (D-A-D) type of donor molecules (M1-M4) with triphenylamine (TPA) as donor moiety, thiophene as bridge, and thiazolothiazole as acceptor unit were designed and its photovoltaic parameters were equated with reference molecule R. DFT functional CAM-B3LYP/6-31G (d,p) was found best for geometry optimization and TD-CAM-B3LYP/6-31G (d,p) was found suitable for excited state calculations. Among designed donor molecules, M4 manifests suitable lowest band gap of 4.73 eV, frontier molecular orbital energy levels as well as distinctive broad absorption of 455.3 nm due to the stronger electron withdrawing group. The electron-withdrawing substituents contribute to red shifts of absorption spectra and better stabilities for designed molecules. The theoretically determined reorganization energies of designed donor molecules suggested excellent charge mobility property. The lower (e) values in comparison with (h) illustrated that these four donor materials would be ideal for electron transfer and M4 would be best amongst the investigated molecules with lowest (e) of 0.0177. Furthermore, the calculated Voc of M4 is 2.04 V with respect to PC60BM (phenyl-C61-butyric acid methyl ester). This study revealed that the designed donor materials are suitable and recommended for high performance organic solar cell devices.
|
|
| 31. |
- Jabeen, Sobia, et al.
(författare)
-
Tuning Optoelectronic Properties of Dithienopyrrole Donor Molecules for Organic Solar Cells
- 2019
-
Ingår i: Russian Journal of Physical Chemistry. - : Maik Nauka/Interperiodica. - 0036-0244 .- 1531-863X. ; 93:11, s. 2233-2243
-
Tidskriftsartikel (refereegranskat)abstract
- Theoretical analysis of physical properties of organic solar cells (OSCs) are important in order to reveal the correlation between power conversion efficiencies (PCE), structure and properties. Five new A-D-A type small molecules M-1, M-2, M-3, M-4, and M-5 were designed by using dithienopyrrole (DTP) as electron rich donor unit with different types of pi-spacers and end capped acceptor units. Functional MPW1PW91/6-31G(d,p) level of theory was used to optimize the geometry of all molecules. For excited state calculation TD-MPW1PW91/6-31G(d,p) level of theory was used. The geometries, electronic structures, dipole moment, open circuit voltage, reorganization energies and charge transport properties of designed molecules M-5) have been scrutinized comparing with the reported compound R. The results revealed that the HOMO energy levels of molecules M-1, M-2, M-3, and M-5 were lower while M-4 was of high energy level thus facilitate the donation of electron as compared to references molecule R. While LUMO energy level of all the molecules were slightly high energy due electron withdrawing effects of spacer and acceptor moiety. Highest energy gap of HOMO-LUMO was observed in M-1 which was 2.48 eV and M-3 showed low energy gap (2.11 eV) as compared to other designed molecules. All molecules showed low values for lambda(e), so they have high rate of electron transfer as compared to R. All designed molecules exhibited higher value of dipole moment as compared to reference molecule R except M-1. Higher value of dipole moment of donor molecules contrary to reference means good solubility towards organic solvents which is beneficial for further solar cell device fabrication. All designed molecules show higher V-oc values except M-4 which has comparable V-oc with respect to reference molecule R. In short, choice of appropriate electron withdrawing and donating groups is very important for improving power conversion efficiencies of OSCs.
|
|
| 32. |
- Kindahl, Tomas, et al.
(författare)
-
Photophysical and DFT Characterization of Novel Pt(II)-Coupled 2,5-Diaryloxazoles for Nonlinear Optical Absorption
- 2012
-
Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 116:47, s. 11519-11530
-
Tidskriftsartikel (refereegranskat)abstract
- Several new bis-phosphine platinum(II) complexes with 2,5-diaryl-substituted oxazole-containing alkyne ligands have been synthesized and optically characterized in solution. Measurements of nonlinear absorption showed strong attenuation of laser light at 532 and 600 nm. The light absorption of the Pt complexes was shifted from the near-UV region for the ground state to the red region for the excited triplet state, and was associated with large extinction coefficients. The optical limiting effect can be explained by triplet-triplet excited state absorption in conjunction with fast excited singlet to-triplet intersystem crossing and slow triplet to-ground-state decay, in comparison with the pulse length of the laser. DFT calculations show good predictability of the S-0-S-1 and S-0-T-1 energy gaps and offer insight into the interaction strength between Pt and the alkyne ligands. The use of this type of ligand, with weak absorption for the Pt(II) complexes in the visual wavelength range as a key feature, enables the possibility to further improve these molecular systems for nonlinear absorption applications.
|
|
| 33. |
- Kindahl, Tomas, 1980-
(författare)
-
Synthesis and development of compounds for nonlinear absorption of light
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High-intensity light — for instance that from a laser — can be destructive, not only to the human eye, but also to equipment such as imaging sensors and optical communication devices. Therefore, effective protection against such light is desirable. A protection device should ideally have high transmission to non-damaging light, and should also be fast-acting in order to effectively stop high-intensity light.In working towards a protection device, there is a need to conduct fundamental research in order to understand the processes involved. One of the photophysical processes of special interest in the field of optical power limiting (OPL) is reverse saturable absorption, where a compound in an excited state absorbs light more strongly than it does in its ground state.In this work, several novel organoplatinum compounds for OPL, rationally designed to have a strong reverse saturable absorption, have been synthesized. The compounds have been analyzed using linear and nonlinear absorption spectroscopy, luminescence spectroscopy, and quantum chemistry calculations to gain further knowledge regarding their photophysical properties.In addition to this fundamental research, the absorption capabilities of some of these compounds indicate that they can be used for OPL applications. Consequently, compounds from these studies have been incorporated into a sol–gel glass that could be used in optical systems.
|
|
| 34. |
|
|
| 35. |
- Lind, Per, et al.
(författare)
-
A QSPR study on optical limiting of organic compounds
- 2004
-
Ingår i: Chemical Physics Letters. - Amsterdam : North-Holland Publishing Co. - 0009-2614 .- 1873-4448. ; 387:4-6, s. 238-242
-
Tidskriftsartikel (refereegranskat)abstract
- The optical limiting performance of 23 structurally different organic compounds has been measured at the wavelength of 532 nm. Molecular orbital ab initio calculations were performed to generate molecular electronic variables that were applied in a quantitative structure–property relationship (QSPR) study. A model that predicts the optical limiting response was constructed by using a partial least square (PLS) analysis. Six variables that play a major role for the optical limiting ability of organic materials were identified.
|
|
| 36. |
|
|
| 37. |
- Lind, Per, et al.
(författare)
-
Non-linear absorption of 2,5-dialkynyl thiophenes
- 2005
-
Ingår i: Journal of Physical Organic Chemistry. - Chichester, Sussex, England : Wiley. - 0894-3230 .- 1099-1395. ; 18:5, s. 426-433
-
Tidskriftsartikel (refereegranskat)abstract
- Three diarylalkynyl-substituted thiophenes were synthesized and the optical power limiting (OPL) effect at 532 nm was investigated for solutions of these compounds. The relationship between the OPL and parameters obtained from molecular-orbital-based calculations is discussed. Semi-empirical calculations indicate that the compounds can have a broad distribution of conformations due to inter-ring twisting, but that the second hyperpolarizability (gamma) can be significant despite a ring twist. The calculations imply that substitution by alkyl groups can lead to enhanced gamma values. The measurements and calculations show a greater increase of the OPL and gamma effects from compound 5 to 6 than from 6 to 7. For these compounds, which differ mainly by the length of the pi-electron system, the magnitude of non-linear absorption seems to be well correlated with several properties of the electronic ground state estimated by standard ab initio molecular orbital calculations, as well as with gamma values from the semi-empirical calculations.
|
|
| 38. |
- Lind, Per, 1971-
(författare)
-
Organic and organometallic compounds for nonlinear absorption of light
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The demand for protection of eyes and various types of optical sensors from laser-beam pulses has resulted in the search for optical limiting devices that have the property of being transparent at low intensity of light (normal light), but non-transparent towards high intensity (laser) light. This type of protection may be obtained by using an organic material that displays nonlinear optical (NLO) properties. Examples of NLO effects that can be used for optical limiting are reverse saturable absorption (RSA), two-photon absorption (TPA) and nonlinear refraction. The advantage of using compounds that show such NLO effects is that they can have very fast response and are self-activating, that is, there is no need for externally controlled switching to obtain optical limiting. In this work, several dialkynyl substituted thiophenes and some thiophenyl-alkynyl-platinum(II)-complexes were synthesized and tested for nonlinear absorption of light. A palladium-copper mediated coupling (Sonogashira coupling) was utilized for all reactions between terminal alkynes and aryl halides. Molecular orbital calculations were used in order to screen for suitable properties, such as the second hyperpolarizability, in compounds of interest. A quantitative structure-activity relationship (QSPR) study using a PLS approach were performed in order to identify important molecular electronic variables for optical limiting of organic compounds.
|
|
| 39. |
- Lind, Per, et al.
(författare)
-
Structural, photophysical, and nonlinear absorption properties of trans-di-arylalkynyl Platinum(II) Complexes with Phenyl and Thiophenyl Groups
- 2007
-
Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 111:9, s. 1598-1609
-
Tidskriftsartikel (refereegranskat)abstract
- Optical power limiting and luminescence properties of two Pt(II) complexes with thiophenyl and phenyl groups in the ligands, trans-Pt(P(n-Bu)3)2(C[triple bond]C-Ar)2, where Ar = -C4H2S-C[triple bond]C-p-C6H4-n-C5H11 (1) and -p-C6H4-C[triple bond]C-C4H3S (2), have been investigated. The fluorescence lifetimes were found to be on the sub-nanosecond time scale, and the quantum yields were low, in accord with fast intersystem crossing from the excited singlet to triplet manifold. The phosphorescence lifetimes of 1 and 2 were shorter than that of a Pt(II) complex having two phenyl groups in the ligands. In order to elucidate the C-Pt bonding nature in the ground state, the 13C NMR chemical shift of the carbon directly bonded to Pt, the coupling constants 1JPtC, 2JPtC, and 1JPtP, and IR νC[triple bond]C wavenumbers were obtained for 1, 2, and three other trans-diarylalkynyl Pt(II) complexes. X-ray diffraction data of 1 and 2 and density functional theory calculated geometries of models of 1, 2, and trans-Pt(P(n-Bu)3)2(C[triple bond]C-p-C6H4-C[triple bond]C-C6H5)2 (3) show that 1 preferably exists in a different conformation from that of 2 and 3. The variations in photophysical, NMR, and IR data can be rationalized by differences in geometry and pi-backbonding from Pt to the alkynyl ligand.
|
|
| 40. |
- Manzoor, Farah, et al.
(författare)
-
Theoretical Calculations of the Optical and Electronic Properties of Dithienosilole- and Dithiophene-Based Donor Materials for Organic Solar Cells
- 2018
-
Ingår i: ChemistrySelect. - : Wiley - V C H Verlag GmbH. - 2365-6549. ; 3:5, s. 1593-1601
-
Tidskriftsartikel (refereegranskat)abstract
- Six Acceptor-Donor-Acceptor (A-D-A) types molecules with dimethyl dithieno[3, 2-b:2',3'-d]silole) -2,6-diyl (DTS) (M-1-M-3) and dimethyl cyclopenta [2, 1-b;3,4-b]-dithiophene (CPDT) (M-4-M-6) core flanged by different acceptor units through methylthiophene bridge are evaluated as donor materials for photovoltaic applications. The photovoltaic properties of M-1-M-3 and M-4-M-6 are compared with standard RaRc and R-b,R-d respectively. Geometry optimization was performed with CAM-B3LYP/6-31G (d) level of theory. TD-CAM-B3LYP has been employed for the estimation of excited state properties of the molecules. M-1, M-2, M-3 and M-4, M-5, M-6 symbolized suitable frontier molecular orbital's (FMO's) energy levels with broad absorption spectra. The electron withdrawing substituents impart red shift in absorption spectra along with good consistancy of designed donor molecules. Reorganization energies of donor molecules (M-1-M-6) showed ideal properties of charge mobility. M-1 and M-4 illustrated lowest le values as compared to lambda(h), thus dictated that designed donor molecules are of good choice for their electron donating ability. Furthermore, M-2 and M-6 demonstrated shortest Eg of 3.7 and 3.72 eV among HOMO and LUMO energy levels.
|
|
| 41. |
- Naessen, Sabine, et al.
(författare)
-
Autoimmune Disease in Turner Syndrome in Sweden : An up to 25 Years' Controlled Follow-up Study
- 2024
-
Ingår i: Journal of Clinical Endocrinology and Metabolism. - : Endocrine Society. - 0021-972X .- 1945-7197. ; 109:2, s. e602-e612
-
Tidskriftsartikel (refereegranskat)abstract
- Context: Turner syndrome (TS) is the most common chromosomal aberration in women; it is the result of structural or numeric abnormalities in the X chromosome. Autoimmune hypothyroidism has been recognized as one of the more prominent disorders associated with TS.Objective: This work aimed to study the prevalence of autoimmune diseases in TS.Methods: A cross-sectional, longitudinal, 25-year follow-up study was conducted of patients from adult Turner centers at the University Hospitals, Sweden. During 1994 to 2020, a total of 503 women aged 16 to 71 years with TS were evaluated consecutively every fifth year according to national guidelines. A random population sample of women, n = 401, aged 25 to 44 years, from the World Health Organization Monitoring of Trends and Determinants for Cardiovascular Disease (MONICA) project served as controls. Serum thyrotropin, free thyroxine, vitamin B-12, antithyroid peroxidase (anti-TPO), and antitransglutaminase antibodies were measured.Results: Mean follow-up time (years) was 16 +/- 7 for patients and 13 +/- 1 for controls. From study start, the prevalence increased in TS for hypothyroidism 40% to 58%, vitamin B-12 deficiency 5% to 12%, celiac disease 4% to 7%, positive anti-TPO 26% to 41%, and antitransglutaminase antibodies 6% to 8% (P < .0001 vs controls). Type 1 diabetes and Addison disease were rare. The only interrelationship was between hypothyroidism and vitamin B-12 deficiency, both in TS and controls. No association between autoimmune disease and karyotype, antecedent growth hormone treatment, or ongoing estrogen hormone replacement, was seen in TS.Conclusion: In women with TS up to older than 80 years, more than half developed hypothyroidism, mainly autoimmune, during follow-up. Awareness of vitamin B-12 deficiency and celiac disease throughout life is also recommended in women with TS.
|
|
| 42. |
- Parola, S., et al.
(författare)
-
Hybrid materials for non linear absorption
- 2005
-
Ingår i: Nonlinear Optical Transmission and Multiphoton Processes in Organics III. - : SPIE - International Society for Optical Engineering. ; , s. 1-5
-
Konferensbidrag (refereegranskat)abstract
- Alkynyl platinum derivatives and thiacalixarenes were trapped in solid transparent matrices prepared by the sol-gel process. By using functionalyzed silicon alkoxides, molecular species were grafted to the gel matrix giving a high doping concentration and chemically stable materials. In this communication we present broadband optical limiting performance in the visible wavelength region observed in the prepared materials.
|
|
| 43. |
- Parola, Stephane, et al.
(författare)
-
Hybrid materials for optical limiting applications
- 2006
-
Ingår i: Optical Materials in Defence Systems Technology III. - Stockholm, Sweden : SPIE-INT SOC OPTICAL ENGINEERING. - 9780819464996 ; , s. U71-U78
-
Konferensbidrag (refereegranskat)abstract
- Optical limiting materials are developed for applications in protection of optical sensors against laser aggressions. We have studied functionalised macrocycles (thiacalixarenes) and alkynylplatinum(H) derivatives for optical limiting applications. Glass materials based on alkynylplatinum(H) derivatives and macrocycles were prepared through the sol-gel process. The molecular species were grafted to the matrix in order to maximise the concentration and the stability of the final solid-state material. The glass materials were cut and polished to approximately 1.5 mm. The glass materials show broadband optical limiting in the visible wavelength region, for nanosecond laser pulses.
|
|
| 44. |
- Revoju, Srikanth, 1987-, et al.
(författare)
-
Asymmetric triphenylamine–phenothiazine based small molecules with varying terminal acceptors for solution processed bulk-heterojunction organic solar cells
- 2018
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 20:9, s. 6390-6400
-
Tidskriftsartikel (refereegranskat)abstract
- Three compounds consisting of the electron-donating triphenylamine–phenothiazine conjugate backbone and each of the electron-withdrawing groups 3-ethylrhodanine, malononitrile and 1,3-indandione have been synthesized and used as donors in blends with [6,6]-phenyl-C70-butyric acid methyl ester (PC71BM) for organic solar cell devices. After improvements of the active layer structure by a selected donor-to-acceptor weight ratio and a two-step solvent and thermal annealing, the organic solar cells showed power conversion efficiency (PCE) values in the range of 4.79–7.25%. The highest PCE was obtained for the bulk heterojunction device with the indandione compound, which can be attributed to its better absorption profile, higher crystallinity, more balanced electron and hole transport, higher charge collection efficiency and reduced recombination, in comparison with the photovoltaic cells from the other two compounds. DFT-calculated characteristics, absorption spectra and cyclic voltammetry of the compounds, along with X-ray diffraction patterns of the blend films, are used to validate the photovoltaic results.
|
|
| 45. |
- Revoju, Srikanth, et al.
(författare)
-
Effect of acceptor strength on optical, electrochemical and photovoltaic properties of phenothiazine-based small molecule for bulk heterojunction organic solar cells
- 2018
-
Ingår i: Dyes and pigments. - : Elsevier. - 0143-7208 .- 1873-3743. ; 149, s. 830-842
-
Tidskriftsartikel (refereegranskat)abstract
- Two new acceptor–π(donor)–donor–π(donor)-acceptor small molecules SM1 and SM2 with benzodithiophene (BDT) donor core unit linked via phenothiazine (PTZ) donor units with 1,3–indanedione and malononitrile end capping units, respectively, have been designed and synthesized and used as electron donor along with PC71BM as acceptor for solution-processed bulk heterojunction organic solar cells. The influence of these end-capping groups on their thermal, optical, electrochemical properties and photovoltaic performance was investigated. After the optimization of the donor to acceptor weight ratio and solvent vapor annealing, the organic solar cells based on SM1:PC71BM and SM2:PC71BM active layers showed the power conversion efficiency (PCE) of 6.20% and 7.45%, respectively. Hence, the end-capping acceptor units for the two small molecules revealed a significant influence on the PCE of the organic solar cells, which resulted from differences in film absorption, molecular packing and charge transport properties.
|
|
| 46. |
- Revoju, Srikanth, 1987-
(författare)
-
Molecular design, synthesis and performance evaluation of phenothiazine-based small molecules for efficient organic solar cells
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Photovoltaics offers one of the most promising routes to generate electricity in a clean way. As an emerging technology in photovoltaics, organic solar cells (OSC) have attracted a great deal of attention owing to their potential low-cost, lightweight, flexibility and solution processability. Although power conversion efficiencies above 12% have been achieved at this date, there is a great interest for new ideal materials to further improve the PCEs and address device durability, which are major concerns for the commercialization of this technology. The main objective of this thesis is to design and synthesize phenothiazine-based conjugate small molecules and explore their use as electron donor components in OSCs. Phenothiazine is a non-planar moiety with unusual “butterfly” type of geometry, which is known to reduce molecular aggregation and intermolecular excimer formation.In the first study of this thesis, a small molecule based on a cyano-arylenevinylene building block with deep HOMO level was prepared. Although a high open-circuit voltage of 1.0 V was achieved, the tendency of the small molecule to crystallize in the active layer at a higher temperature and with time hindered the attainment of an optimal phase morphology required for the achievement of a higher efficiency. In the second and third studies, phenothiazine was used as a π-system bridge and as a core unit to construct small molecules based on symmetric and asymmetric frameworks with varying terminal electron-withdrawing groups. The electron-withdrawing property of the terminal units was found to have a significant influence on the optical absorption properties, electronic energy levels, molecular ordering, charge carrier mobility and morphology of the resulting active layers. In the fourth study, side-chain modification of the phenothiazine unit of symmetrically configured small molecules with an oxygen-containing (methoxyethoxy ethyl) side chain resulted in the enhancement of the dielectric constant. Although absorption properties were unchanged in solution, a dense π-π stacking was observed in the solid state.In summary, it is demonstrated that phenothiazine is a promising candidate and worth exploring donor material for OSCs. Its versatility as a π-linker and as a central core unit in symmetric and asymmetric configurations has been explored. The use of nonplanar building blocks such as phenothiazine for the construction of donor materials is an interesting strategy for controlling molecular aggregation and difficult solution processability of small molecules if it is combined with a judiciously designed conjugate backbone.
|
|
| 47. |
- Revoju, Srikanth, et al.
(författare)
-
Phenothiazine-based small molecules for bulk heterojunction organic solar cells : Variation of side-chain polarity and length of conjugated system
- 2019
-
Ingår i: Organic electronics. - : Elsevier. - 1566-1199 .- 1878-5530. ; , s. 232-242
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Three small molecules denoted SM1, SM2 and SM3, with the phenothiazine donor moiety connected to benzothiadiazole and 3-ethylrhodanine acceptor units through thiophene π-linkers have been synthesized for use in organic solar cells with PC71BM as electron acceptor. SM1 has a 2-ethylhexyl group at the phenothiazine nitrogen, while SM2 and SM3have a 2-(2-methoxyethoxy)ethyl group at that N. Opto-electronic and dielectric properties, charge carrier mobilities, morphology of active layers, and photovoltaic properties were investigated in detail. The three molecules have wide absorption bands with high molar absorption coefficients and relatively low HOMO levels (−5.21 to −5.27 eV). Compared with the N-alkylated SM1, both SM2 and SM3 exhibit red-shifts of the long-wavelength absorption band in thin films, and show enhanced crystallinity in thin films with smaller stacking distances, higher hole mobility, and higher dielectric constant. After solvent vapourannealing, the power conversion efficiencies (PCEs) were significantly improved for the solar cell devices, from 1.69 to 3.95% for SM1, 2.78–6.62% for SM2 and 3.22–7.16% for SM3. This increase in PCEs was due to the enhancement in Jsc and FF attributed to the formation of nanoscale domains of donor and acceptor resulting in efficient charge separation, balanced charge transport and suppressed charge recombination. These results demonstrate that use of an oxygen-containing side chain, in conjunction with alkyl side chains for solubility during solar cell processing, is an alternative and effective strategy for achieving high-performance small molecule donor materials.
|
|
| 48. |
- Reyes Forsberg, Diana Carolina, 1984-
(författare)
-
Experimental study of alkalinisation of cellulose in industrial relevant conditions
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mercerisation of cellulose pulp with a solution of NaOH is the first step of manufacturing cellulose-based value-added products, e.g. viscose fibres and cellulose ethers. During this process, cellulose transforms into a swollen crystalline structure, alkali cellulose (Na-Cell). This increases the reactivity of the cellulose and makes it more accessible for reagents to penetrate and react with the hydroxyl groups. The mercerisation conditions are known to affect the degree of alkalinisation of cellulose as well as the final products. The main objective of this thesis is to investigate how the alkalinisation of softwood sulphite dissolving cellulose pulp is influenced by the co-variation of process variables in the mercerisation in industrial relevant conditions, for both viscose and cellulose ether production. This objective was achieved by quantitative analysis of the effect of simultaneous variation of a set of key parameters on the degree of alkalinisation (i.e. degree of activation, DoA) of the chosen dissolving pulp. Quantitative measurements were performed using Raman spectroscopy data, evaluated by partial least squares (PLS) regression. For mercerisation at viscose production conditions, the effect of studied variables on mass yield was also considered. In the case of mercerisation at ether processing conditions, formation of alkali cellulose at a fixed temperature was included. The knowledge obtained on mercerisation under ether processing conditions was then applied for preparation of the ionic cellulose ether carboxymethylcellulose (CMC). The overall results show that temperature has a strong effect on DoA and mass yield for mercerised samples under steeping conditions. Measured DoA decreases as the temperature increases from 20 to 70 °C. Mass yield correlates positively with the temperature up to 45-50 °C in the PLS model, after which the relation is negative. The [NaOH] and reaction time show a complex dependence of other variables. At mercerisation conditions for cellulose ether production, the NaOH/AGU stoichiometric ratio, denoted as (r), shows to be very important for DoA, with a positive correlation. At these mercerisation conditions, temperature shows no effect on DoA. The influence of the [NaOH] (which also refers to the concentration of water) shows a complex dependence on (r). As (r) increases and [NaOH] decreases, the measured DoA increases. Prolonged mercerisation time shows no significance in the modelled DoA. However, a gradual increase of the DoA over time was seen when mercerisation was performed with 30% and 40% [NaOH] at (r) = 0.8, suggesting a slow diffusion of NaOH and Na-Cell formation. 13C CP-MAS NMR measurements of samples produced at room temperature show that formation of the Na-Cell allomorph is mainly determined by the [NaOH]. However, in the transition area between Na-Cell I and Na-Cell II, (r) also seems to be of importance. An increase of DS in the produced CMC samples also shows to be consistent at such conditions with the increase in the measured DoA and with increased (r) and decreased [NaOH]. However, these conditions also favour the formation of by-products. In the synthesised CMC samples, a DS of up to 0.7 was achieved. Measured solubility was lower than expected for any given DS. This, along with the non-statistical distribution of monomer units in the polymer chains, indicates high heterogeneity in the synthesised samples. The distribution of substituents within the AGU shows attachment to hydroxyl oxygens in the order O3 < O2 ≈ O6. The relative importance of the substitution at O3 indicates an increase at this position when [NaOH] increases.The models presented in this thesis will hopefully serve as a basis for predicting the effects of the studied variables on the DoA, as well as on the mass yield of cellulose pulp when mercerisation conditions are adjusted. Moreover, it is believed that the presented studies can give a better understanding of mercerisation at cellulose ether conditions, hence enabling further development of this process step.
|
|
| 49. |
- Sahar, Anum, et al.
(författare)
-
UV absorbers for cellulosic apparels : A computational and experimental study
- 2018
-
Ingår i: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - : Elsevier. - 1386-1425 .- 1873-3557. ; 188, s. 355-361
-
Tidskriftsartikel (refereegranskat)abstract
- Two triazine based Ultra Violet (UV) absorbers Sulfuric acid mono-(2-{4-[4-chloro-6-(4-{4-chloro-6-[4-(2-sulfooxy-ethanesulfonyl)-phenylamino]-[1,3,5] triazin-2-ylamino-phenylamino)-[1,3,5]triazin-2-ylamino]-benzenesulfonyl}-ethyl) ester (1a) and 4-{4-chloro-6-[4-(2-sulfooxy-ethanesulfonyl)-phenylamino]-[1,3,5] triazin-2-ylamino}-2-[4-chloro-6-(2-sulfooxy-ethanesulfonyl)-[1,3,5]triazin-2-ylamino]-benzenesulfonic acid (2a) with different substituents were designed computationally. The influence of different substituents on the electrochemical properties and UV spectra of the absorbers was investigated. The presence of electron deficient unit in 1a to the molecular core significantly reduces the LUMO levels and energy gap. The designed absorbers were synthesized via condensation reaction and characterized by UV–Vis, FT-IR, MS studies. The performance of synthesized compounds as UV absorbers and their fastness properties were assessed by finishing the cotton fabric through exhaust method at different concentration and results appeared in good range.
|
|
| 50. |
- Shahzadi, Iram, et al.
(författare)
-
Estimation of optical rotation of gamma-alkylidenebutenolide, cyclopropylamine, cyclopropyl-methanol and cyclopropenone based compounds by a Density Functional Theory (DFT) approach
- 2017
-
Ingår i: Chirality. - : Wiley Periodicals. - 0899-0042 .- 1520-636X. ; 29:10, s. 634-647
-
Tidskriftsartikel (refereegranskat)abstract
- Computing the optical rotation of organic molecules can be a real challenge, and various theoretical approaches have been developed in this regard. A benchmark study of optical rotation of various classes of compounds was carried out by Density Functional Theory (DFT) methods. The aim of the present research study was to find out the best-suited functional and basis set to estimate the optical rotations of selected compounds with respect to experimental literature values. Six DFT functional LSDA, BVP86, CAM-B3LYP, B3PW91, and PBE were applied on 22 different compounds. Furthermore, six different basis sets, i.e., 3-21G, 6-31G, aug-cc-pVDZ, aug-cc-pVTZ, DGDZVP, and DGDZVP2 were also applied with the best-suited functional B3LYP. After rigorous effort, it can be safely said that the best combination of functional and basis set is B3LYP/aug-cc-pVTZ for the estimation of optical rotation for selected compounds.
|
|
