V. Kampars - Academia.edu (original) (raw)

Papers by V. Kampars

physica status solidi (c), 2005

Azobenzene oligomer layers with side chain chromofore groups (ChG) has been experimentally studie... more Azobenzene oligomer layers with side chain chromofore groups (ChG) has been experimentally studied to optimize scalar and vector hologram recording at 633 nm. ChG with different acceptors (Br, NO 2 , H, CN) and different bonding type to the matrix (dispersed without bonding or with covalent bonding) were used. The influence of oligomer matrix (polyvinylbuthirol, tolyle, hexamethylene, polyvinylpirolidone, double matrix) and spacers was also studied. The best results (the maximal diffraction efficiency of 7.9% and the minimal specific recording energy of 0.38 J/(cm 2 %)) are obtained for ChG with one NO 2 acceptor group covalently bonded to tolyle matrix. Double matrix considerably decreases the recording energy and the hologram lifetime, and enables more efficient vector recording.The conclusion is made that ChG photoorientation accompanied by other processes is responsible for 633 nm recording.

Chemistry of Heterocyclic Compounds, 1978

ABSTRACT The initial step in the reaction of isopropylidene malonate with N-arylidene-1(or 2)-nap... more ABSTRACT The initial step in the reaction of isopropylidene malonate with N-arylidene-1(or 2)-naphthylamines is cleavage of the latter. The reaction gives isopropylidene 2-arylidene malonates, which subsequently react with a(or ß)-naphthylamines to give 4-aryl-2-oxo-1,2,3,4-tetrahydro-7,8(or 5,6)-benzoquinolines. The latter are also obtained in the reaction of arylbis (isopropylidenemalonatyl)methanes with a(or ß)-naphthylamines. Indane-1,3-dione and dimedone also cleave N-arylidene-1(or 2)-naphthylamines, and 2-arylideneindane-1,3-diones or arylbis (dimedonyl) methanes are obtained.

Journal of Analytical and Applied Pyrolysis

The transesterification of vegetable oil using various kinds of alcohols is a simple and efficien... more The transesterification of vegetable oil using various kinds of alcohols is a simple and efficient renewable fuel synthesis technique. Products obtained by modifying natural triglycerides in transesterification reaction substitute fossil fuels and mineral oils. Currently the most significant is the biodiesel, a mixture of fatty acid methyl esters, which is obtained in a reaction with methanol, which in turn is

Bioresource Technology, 2016

Acta Crystallographica Section A Foundations of Crystallography, 2007

Fuel Processing Technology, 2015

Журнал аналитической химии, 2014

ABSTRACT A convenient method for the analysis of commercial acetylated glycerol samples based on ... more ABSTRACT A convenient method for the analysis of commercial acetylated glycerol samples based on 13C NMR is presented with the accuracy comparable to the standard gas chromatography approaches. The advantage of method is that it does not need any sample derivatization procedure by silyl groups and its application is much more straightforward, as compared to the published 1H NMR method.

Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference, 2015

The transesterification of vegetable oil using various kinds of alcohols is a simple and efficien... more The transesterification of vegetable oil using various kinds of alcohols is a simple and efficient renewable fuel synthesis technique. Products obtained by modifying natural triglycerides in transesterification reaction substitute fossil fuels and mineral oils. Currently the most significant is the biodiesel, a mixture of fatty acid methyl esters, which is obtained in a reaction with methanol, which in turn is obtained from fossil raw materials. In biodiesel production it would be more appropriate to use alcohols which can be obtained from renewable local raw materials. Ethanol rouses interest as a possible reagent, however, its production locally is based on the use of grain and therefore competes with food production so it would implicitly cause increase in food prices. Another raw material option is alcohols that can be obtained from furfurole. Furfurole is obtained in dehydration process from pentose sugars which can be extracted from crop straw, husk and other residues of agric...

Proceedings of ISES World Congress 2007 (Vol. I – Vol. V), 2008

ABSTRACT An attempt was made to extend the photosensitivity spectral range of fullerene/poly(3-he... more ABSTRACT An attempt was made to extend the photosensitivity spectral range of fullerene/poly(3-hexylthiophene) blend to NIR region by adding extra electron donor — hydroxygallium phthalocyanine (GaOHPc) with a strong and wide intermolecular charge transfer (CT) band around 830 nm. Multilayer cells of ITO/PEDOT: PSS/6 GaOHPc/P3HT: C61(CO2Et)2 have been prepared by spin coating with vacuum evaporated Al or In top electrodes. Significant photosensitivity of the cells was in 370–900 nm spectral range. However charge carrier photogeneration efficiency was 3 times higher for illumination in P3HT absorption band as compared with the GaOHPc CT band at 830 nm. But when GaOHPc was mixed in the blend forming P3HT:C61(CO2Et)2:GaOHPc active layer its CT band shifted to infrared part at 875 nm. At the same time the charge carrier photogeneration efficiency for illumination in GaOHPc CT band increased significantly, exceeding its value for illumination in P3HT absorption band.

An attempt was made to extend the photosensitivity spectral range of fullerene/poly(3- hexylthiop... more An attempt was made to extend the photosensitivity spectral range of fullerene/poly(3- hexylthiophene) blend to NIR region by adding extra electron donor - hydroxygallium phthalocyanine (GaOHPc) with a strong and wide intermolecular charge transfer (CT) band around 830 nm. Multilayer cells of ITO/PEDOT: PSS/6 GaOHPc/P3HT: C 61 (CO 2Et) 2 have been prepared by spin coating with vacuum evaporated Al or In top electrodes. Significant photosensitivity of the cells was in 370-900 nm spe ctral range. However charge carrier photogeneration efficiency was 3 times higher for i llumination in P3HT absorption band as compared with the GaOHPc CT band at 830 nm. But when GaOHPc was mixed in the blend forming P3HT:C 61 (CO 2Et) 2:GaOHPc active layer its CT band shifted to infrare d part at 875 nm. At the same time the charge carrier photogenera tion efficiency for illumination in GaOHPc CT band increased significantly, exceeding its value for illumination in P3HT absorption band.

IOP Conference Series: Materials Science and Engineering, 2015

ABSTRACT The effect of the gold nanoparticles size, gold load, nature of support and composites&a... more ABSTRACT The effect of the gold nanoparticles size, gold load, nature of support and composites' specific surfaces area on the nanocomposites catalytic activity and selectivity was studied. It was demonstrated that glycerol conversion increased from 62% to 100% in the presence of the nanocomposites when Au particle size decreased from 26 to 1 nm. Glyceric acid was obtained as a main product with high selectivity.

Latvian Journal of Chemistry, 2011

IOP Conference Series: Materials Science and Engineering, 2015

Using extractive-pyrolytic method fine-disperse Pt containing composites were synthesized and tes... more Using extractive-pyrolytic method fine-disperse Pt containing composites were synthesized and tested in catalytic glycerol oxidation. Catalyst activity and selectivity to glycolic acid was determined oxidizing glycerol in mild conditions. It was concluded that only iron containing platinum catalysts were selective to glycolic acid. Selectivity to glycolic acid reached 53-60% with glycerol conversion 12-56%.

Latvian Journal of Physics and Technical Sciences, 2014

Single sheet graphene (SG) is an innovative transparent material with high electrical and thermal... more Single sheet graphene (SG) is an innovative transparent material with high electrical and thermal conduction the use of which in transparent electrodes instead of traditional materials improves the performance of optoelectronic devices. In this study, graphene oxide (GO) has been obtained by a modified Hummer`s method followed by an advanced technique of water removal (lyophilisation). The Langmuir-Blodgett (LB) method was applied to transfer GO from suspension to substrate. To optimize the deposition process, as suspending and spreading solvents the benzene and benzene/methanol mixtures were chosen instead of previously studied water suspensions. The number of GO layers in suspension is reduced by exfoliation in order to obtain a single GO monolayer. For this purpose, sonication and centrifugation of GO sheets are carried out. Finally, the effect of variously treated glass substrate surfaces on the deposition efficiency has been studied. In the work, it is shown that ozonization of...

IOP Conference Series: Materials Science and Engineering, 2015

Latvian Journal of Chemistry, 2011

physica status solidi (a), 2011

ABSTRACT We report on second order optical nonlinearity in E–O active polymer materials – dendrim... more ABSTRACT We report on second order optical nonlinearity in E–O active polymer materials – dendrimer structures of three different generations – investigated by means of all-optical poling. Chromophores containing azo junction used for experiments were prepared as guest-host type system based on polycarbonate matrix spin-coated on a glass substrate. Molecular orientation and subsequent decay kinetics in two modes of reading beam performance, when reading (i) not permanent irradiated or (ii) permanent irradiated, were measured. Depending on the intensity of reading beam the decay for different structures was measured and analyzed. Experimental results show that read-out intensity determines faster decay of second harmonic signal, i.e., effective “washing-out” the polar orientation alignment of molecules.

Thin Solid Films, 2008

Surface relief gratings (SRGs) on organic thin films are studied extensively for both scientific ... more Surface relief gratings (SRGs) on organic thin films are studied extensively for both scientific interest and in relevance to the applications. Among the chromophores being used the azobenzenes showed the best performance, but the use of alternative photo-sensitive groups provides better general understanding of the phenomena. A thermodynamic theory and molecular dynamics simulations of photoinduced effects are discussed. In this study we use indandione derivatives, known as promising materials for photonics applications, as an alternative to the azobenzenes. We consider their photoreactions when incorporated into a polymer film. One of interesting features is the spectral dependence of the diffraction of indandione containing gratings, which is observed and discussed.

physica status solidi (c), 2005

Azobenzene oligomer layers with side chain chromofore groups (ChG) has been experimentally studie... more Azobenzene oligomer layers with side chain chromofore groups (ChG) has been experimentally studied to optimize scalar and vector hologram recording at 633 nm. ChG with different acceptors (Br, NO 2 , H, CN) and different bonding type to the matrix (dispersed without bonding or with covalent bonding) were used. The influence of oligomer matrix (polyvinylbuthirol, tolyle, hexamethylene, polyvinylpirolidone, double matrix) and spacers was also studied. The best results (the maximal diffraction efficiency of 7.9% and the minimal specific recording energy of 0.38 J/(cm 2 %)) are obtained for ChG with one NO 2 acceptor group covalently bonded to tolyle matrix. Double matrix considerably decreases the recording energy and the hologram lifetime, and enables more efficient vector recording.The conclusion is made that ChG photoorientation accompanied by other processes is responsible for 633 nm recording.

Chemistry of Heterocyclic Compounds, 1978

ABSTRACT The initial step in the reaction of isopropylidene malonate with N-arylidene-1(or 2)-nap... more ABSTRACT The initial step in the reaction of isopropylidene malonate with N-arylidene-1(or 2)-naphthylamines is cleavage of the latter. The reaction gives isopropylidene 2-arylidene malonates, which subsequently react with a(or ß)-naphthylamines to give 4-aryl-2-oxo-1,2,3,4-tetrahydro-7,8(or 5,6)-benzoquinolines. The latter are also obtained in the reaction of arylbis (isopropylidenemalonatyl)methanes with a(or ß)-naphthylamines. Indane-1,3-dione and dimedone also cleave N-arylidene-1(or 2)-naphthylamines, and 2-arylideneindane-1,3-diones or arylbis (dimedonyl) methanes are obtained.

Journal of Analytical and Applied Pyrolysis

The transesterification of vegetable oil using various kinds of alcohols is a simple and efficien... more The transesterification of vegetable oil using various kinds of alcohols is a simple and efficient renewable fuel synthesis technique. Products obtained by modifying natural triglycerides in transesterification reaction substitute fossil fuels and mineral oils. Currently the most significant is the biodiesel, a mixture of fatty acid methyl esters, which is obtained in a reaction with methanol, which in turn is

Bioresource Technology, 2016

Acta Crystallographica Section A Foundations of Crystallography, 2007

Fuel Processing Technology, 2015

Журнал аналитической химии, 2014

ABSTRACT A convenient method for the analysis of commercial acetylated glycerol samples based on ... more ABSTRACT A convenient method for the analysis of commercial acetylated glycerol samples based on 13C NMR is presented with the accuracy comparable to the standard gas chromatography approaches. The advantage of method is that it does not need any sample derivatization procedure by silyl groups and its application is much more straightforward, as compared to the published 1H NMR method.

Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference, 2015

The transesterification of vegetable oil using various kinds of alcohols is a simple and efficien... more The transesterification of vegetable oil using various kinds of alcohols is a simple and efficient renewable fuel synthesis technique. Products obtained by modifying natural triglycerides in transesterification reaction substitute fossil fuels and mineral oils. Currently the most significant is the biodiesel, a mixture of fatty acid methyl esters, which is obtained in a reaction with methanol, which in turn is obtained from fossil raw materials. In biodiesel production it would be more appropriate to use alcohols which can be obtained from renewable local raw materials. Ethanol rouses interest as a possible reagent, however, its production locally is based on the use of grain and therefore competes with food production so it would implicitly cause increase in food prices. Another raw material option is alcohols that can be obtained from furfurole. Furfurole is obtained in dehydration process from pentose sugars which can be extracted from crop straw, husk and other residues of agric...

Proceedings of ISES World Congress 2007 (Vol. I – Vol. V), 2008

ABSTRACT An attempt was made to extend the photosensitivity spectral range of fullerene/poly(3-he... more ABSTRACT An attempt was made to extend the photosensitivity spectral range of fullerene/poly(3-hexylthiophene) blend to NIR region by adding extra electron donor — hydroxygallium phthalocyanine (GaOHPc) with a strong and wide intermolecular charge transfer (CT) band around 830 nm. Multilayer cells of ITO/PEDOT: PSS/6 GaOHPc/P3HT: C61(CO2Et)2 have been prepared by spin coating with vacuum evaporated Al or In top electrodes. Significant photosensitivity of the cells was in 370–900 nm spectral range. However charge carrier photogeneration efficiency was 3 times higher for illumination in P3HT absorption band as compared with the GaOHPc CT band at 830 nm. But when GaOHPc was mixed in the blend forming P3HT:C61(CO2Et)2:GaOHPc active layer its CT band shifted to infrared part at 875 nm. At the same time the charge carrier photogeneration efficiency for illumination in GaOHPc CT band increased significantly, exceeding its value for illumination in P3HT absorption band.

An attempt was made to extend the photosensitivity spectral range of fullerene/poly(3- hexylthiop... more An attempt was made to extend the photosensitivity spectral range of fullerene/poly(3- hexylthiophene) blend to NIR region by adding extra electron donor - hydroxygallium phthalocyanine (GaOHPc) with a strong and wide intermolecular charge transfer (CT) band around 830 nm. Multilayer cells of ITO/PEDOT: PSS/6 GaOHPc/P3HT: C 61 (CO 2Et) 2 have been prepared by spin coating with vacuum evaporated Al or In top electrodes. Significant photosensitivity of the cells was in 370-900 nm spe ctral range. However charge carrier photogeneration efficiency was 3 times higher for i llumination in P3HT absorption band as compared with the GaOHPc CT band at 830 nm. But when GaOHPc was mixed in the blend forming P3HT:C 61 (CO 2Et) 2:GaOHPc active layer its CT band shifted to infrare d part at 875 nm. At the same time the charge carrier photogenera tion efficiency for illumination in GaOHPc CT band increased significantly, exceeding its value for illumination in P3HT absorption band.

IOP Conference Series: Materials Science and Engineering, 2015

ABSTRACT The effect of the gold nanoparticles size, gold load, nature of support and composites&a... more ABSTRACT The effect of the gold nanoparticles size, gold load, nature of support and composites' specific surfaces area on the nanocomposites catalytic activity and selectivity was studied. It was demonstrated that glycerol conversion increased from 62% to 100% in the presence of the nanocomposites when Au particle size decreased from 26 to 1 nm. Glyceric acid was obtained as a main product with high selectivity.

Latvian Journal of Chemistry, 2011

IOP Conference Series: Materials Science and Engineering, 2015

Using extractive-pyrolytic method fine-disperse Pt containing composites were synthesized and tes... more Using extractive-pyrolytic method fine-disperse Pt containing composites were synthesized and tested in catalytic glycerol oxidation. Catalyst activity and selectivity to glycolic acid was determined oxidizing glycerol in mild conditions. It was concluded that only iron containing platinum catalysts were selective to glycolic acid. Selectivity to glycolic acid reached 53-60% with glycerol conversion 12-56%.

Latvian Journal of Physics and Technical Sciences, 2014

Single sheet graphene (SG) is an innovative transparent material with high electrical and thermal... more Single sheet graphene (SG) is an innovative transparent material with high electrical and thermal conduction the use of which in transparent electrodes instead of traditional materials improves the performance of optoelectronic devices. In this study, graphene oxide (GO) has been obtained by a modified Hummer`s method followed by an advanced technique of water removal (lyophilisation). The Langmuir-Blodgett (LB) method was applied to transfer GO from suspension to substrate. To optimize the deposition process, as suspending and spreading solvents the benzene and benzene/methanol mixtures were chosen instead of previously studied water suspensions. The number of GO layers in suspension is reduced by exfoliation in order to obtain a single GO monolayer. For this purpose, sonication and centrifugation of GO sheets are carried out. Finally, the effect of variously treated glass substrate surfaces on the deposition efficiency has been studied. In the work, it is shown that ozonization of...

IOP Conference Series: Materials Science and Engineering, 2015

Latvian Journal of Chemistry, 2011

physica status solidi (a), 2011

ABSTRACT We report on second order optical nonlinearity in E–O active polymer materials – dendrim... more ABSTRACT We report on second order optical nonlinearity in E–O active polymer materials – dendrimer structures of three different generations – investigated by means of all-optical poling. Chromophores containing azo junction used for experiments were prepared as guest-host type system based on polycarbonate matrix spin-coated on a glass substrate. Molecular orientation and subsequent decay kinetics in two modes of reading beam performance, when reading (i) not permanent irradiated or (ii) permanent irradiated, were measured. Depending on the intensity of reading beam the decay for different structures was measured and analyzed. Experimental results show that read-out intensity determines faster decay of second harmonic signal, i.e., effective “washing-out” the polar orientation alignment of molecules.

Thin Solid Films, 2008

Surface relief gratings (SRGs) on organic thin films are studied extensively for both scientific ... more Surface relief gratings (SRGs) on organic thin films are studied extensively for both scientific interest and in relevance to the applications. Among the chromophores being used the azobenzenes showed the best performance, but the use of alternative photo-sensitive groups provides better general understanding of the phenomena. A thermodynamic theory and molecular dynamics simulations of photoinduced effects are discussed. In this study we use indandione derivatives, known as promising materials for photonics applications, as an alternative to the azobenzenes. We consider their photoreactions when incorporated into a polymer film. One of interesting features is the spectral dependence of the diffraction of indandione containing gratings, which is observed and discussed.