To achieve a suitable packaging configuration, it is important first to determine the physicochem... more To achieve a suitable packaging configuration, it is important first to determine the physicochemical characteristics related to the packaged product. In this study, the physicochemical characterization of fresh purple passion fruits of three different ripening stages was carried out to determine key variables for the packaging, such as O2 consumption and CO2 -ethylene production rates. Subsequently, intermediate-ripe fruits were packaged for 21 days at 6 °C under three packaging conditions: Xtend® perforated bags, low-density polyethylene (LDPE) bags, and LDPE bags with a novel ethylene scavenger active additive (ESAA). It was observed that an equilibrium modified atmosphere was formed in the packages. For the Xtend® bags, the highest values of O2 (yo2 = 0.184 to 0.192) and lowest of CO2 (yco2 = 0.033 to 0.041) were reached, whereas for the LDPE bags with ESAA these values were moderate. In the case of ethylene, the LDPE bags showed the highest levels in the headspace (26 to 31 ppm), whereas the lowest levels were obtained in the LDPE bags with additive (2 to 4 ppm). These levels resulted in a delay in the ripening of the fruits during storage, which was verified through a sensory acceptability test that was carried out on the juice extracted from the fruits. In this sensory test, panelists identified similar characteristics between the fruits packaged with ESAA and the Xtend® bags, regarding the control fruits. The LDPE bags with the ethylene scavenger performed satisfactorily and can considerably delay the ripening, which may result in longer shelf life and conservation of fresh purple passion fruits. PRACTICAL APPLICATION: This work presents a novel packaging proposal that reduces oxygen and ethylene levels in contact with purple passion fruits. Our proposed active packaging can be used to increase the fruit shelf life by improving its conservation conditions throughout the chain of storage, transport, and distribution in the market. With this, it will be possible to reduce the fruit's losses due to senescence and to reduce the substrate consumption by using a more effective packaging system.
After an internal conflict that lasted over half a century, the detection and removal of antipers... more After an internal conflict that lasted over half a century, the detection and removal of antipersonnel landmines in Colombia have become cumbersome challenges. Antipersonnel landmines remain scattered in Colombia and with a considerable impact on the central-western region. Most of these devices are handmade (therefore, they can also be classified as improvised explosive devices) and composed of ammonium nitrate and fossil fuel blend, a mixture known as ANFO. Due to several unique factors, including concealment tactics and non-conventional manufacturing techniques employed by guerrilla fighters, the most efficient method for the detection of ANFO-based antipersonnel landmines is the use of trained canines. This review aims at describing the current chemical strategies used in the detection of ANFO-based antipersonnel landmines. First, a detailed description of the different techniques used in the detection of explosives is made. Then, all the strategies reported in the world for ant...
Acta Crystallographica Section E Crystallographic Communications, 2017
In the title compounds,N-(5-acetyl-2-methylphenyl)quinoline-2-carboxamide [C19H16N2O2, (I)],N-(5-... more In the title compounds,N-(5-acetyl-2-methylphenyl)quinoline-2-carboxamide [C19H16N2O2, (I)],N-(5-acetyl-2-bromophenyl)quinoline-2-carboxamide [C18H13BrN2O2, (II)] andN-(5-acetyl-2-ethynylphenyl)quinoline-2-carboxamide [C20H14N2O2, (III)], the quinoline ring system is essentially planar and forms a dihedral angles of 3.68 (5) (I), 5.59 (7) (II) and 1.87 (6)° (III) with the acetyl-substituted ring. The molecular structures of (I) and (III) each feature an intramolecular N—H...N hydrogen bond, forming anS(5) ring, while in (II) an intramolecular bifurcated N—H...(N,Br) hydrogen bond forms twoS(5) rings. In the crystals, weak C—H...O hydrogen bonds link molecules of (I) intoC(7) chains long [010], molecules of (II) into chains ofR22(8) rings along [110] and molecules of (III) intoC(8) chains along [010]. In (I), there are no significant π–π stacking interactions under 4 Å, but in both (II) and (III), π–π interactions link the weak hydrogen-bonded chains into layers parallel to (001) [ce...
Acta Crystallographica Section E Crystallographic Communications, 2017
In the title compound, C10H9NO2S, all the non-H atoms, except for the ethyl fragment, lie nearly ... more In the title compound, C10H9NO2S, all the non-H atoms, except for the ethyl fragment, lie nearly in the same plane. Despite the molecular planarity, the ethyl fragment presents more than one conformation, giving rise to a discrete disorder, which was modelled with two different crystallographic sites for the ethoxy O and ethoxy α-C atoms, with occupancy values of 0.5. In the crystal, the three-dimensional array is mainly directed by C—H...(O,N) interactions, giving rise to inversion dimers withR22(10) andR22(14) motifs and infinite chains running along the [100] direction.
ABSTRACT In this work, the effect of addition of kaolinite and rice husk microparticles on the wa... more ABSTRACT In this work, the effect of addition of kaolinite and rice husk microparticles on the water vapor permeability of polylactic acid (PLA) was evaluated. The PLA-composites materials were characterized by X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and optical microscopy. For the composite preparation, an experimental design was established using two factors: additive type and concentration. When evaluating the water vapor permeability of the composites, it was found that the incorporation of kaolinite at 1% and 5% reduced the permeability coefficient of PLA. Furthermore, the inclusion of 5% kaolinite showed an increase on the tensile strength of the material. By contrast, the addition of rice husk produced an increase on water vapor permeability of the material and a decrease of both the tensile strength and ductility (percent of elongation at fracture). The higher dispersion and more regular morphology of the kaolinite particles could explain the enhancement of the gas barrier. A similar thermal behavior was observed for both PLA and composite materials, confirming that no damage of these properties was caused with the incorporation of the filler particles.
Journal of the American Society for Mass Spectrometry, 2017
Phenylenevinylene oligomers (PVs) have outstanding photophysical characteristics for applications... more Phenylenevinylene oligomers (PVs) have outstanding photophysical characteristics for applications in the growing field of organic electronics. Yet, PVs are also versatile molecules, the optical and physicochemical properties of which can be tuned by manipulation of their structure. We report the synthesis, photophysical, and MS characterization of eight PV derivatives with potential value as electron transfer (ET) matrices for UV-MALDI. UV-vis analysis show the presence of strong characteristic absorption bands in the UV region and molar absorptivities at 355 nm similar or higher than those of traditional proton (CHCA) and ET (DCTB) MALDI matrices. Most of the PVs exhibit non-radiative quantum yields (φ) above 0.5, indicating favorable thermal decay. Ionization potential values (IP) for PVs, calculated by the Electron Propagator Theory (EPT), range from 6.88 to 7.96 eV, making these oligomers good candidates as matrices for ET ionization. LDI analysis of PVs shows only the presence of radical cations (M +.) in positive ion mode and absence of clusters, adducts, or protonated species; in addition, M +. threshold energies for PVs are lower than for DCTB. We also tested the performance of four selected PVs as ET MALDI matrices for analytes ranging from porphyrins and phthalocyanines to polyaromatic compounds. Two of the four PVs show S/N enhancement of 1961% to 304% in comparison to LDI, and laser energy thresholds from 0.17 μJ to 0.47 μJ compared to 0.58 μJ for DCTB. The use of PV matrices also results in lower LODs (low fmol range) whereas LDI LODs range from pmol to nmol.
aditivo antiempañante en una matriz polimérica. g representa la tensión superficial y los subíndi... more aditivo antiempañante en una matriz polimérica. g representa la tensión superficial y los subíndices s, l y v representan las interfases sólido, líquido y vapor, respectivamente.
The title compound 9-(4-hydroxybutyl)-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2... more The title compound 9-(4-hydroxybutyl)-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione was synthesized in 72% yield through a simple, convenient and environmentally friendly one-pot reaction between dimedone and 3,4-dihydro-2H-pyran in aqueous citric acid. Additionally, a plausible reaction mechanism for the formation of the target xanthene is proposed.
The title compound 1,4-di(2-butoxycarbonyl-trans-vinyl)-2,5dimethoxybenzene was synthesized in 94... more The title compound 1,4-di(2-butoxycarbonyl-trans-vinyl)-2,5dimethoxybenzene was synthesized in 94% yield through the Heck reaction between 2,5diiodo-1,4-dimethoxybenzene and n-butyl acrylate, using bis(dibenzylideneacetone) palladium(0) as homogeneous catalyst.
Three new carboxylic-acid substituted oligo-phenylenevinylenes (OPVs) with electron-donating subs... more Three new carboxylic-acid substituted oligo-phenylenevinylenes (OPVs) with electron-donating substituents in the central ring were synthesized in high yield by the Mizoroki-Heck reaction. The linkers were optically characterized by UV-vis absorption spectrophotometry, fluorescence spectroscopy in solution and the solid state, and measurement of the emission quantum yield. A comparison of substituted and unsubstituted OPVs shows that the electron-donating groups significantly affect the luminescent properties of the linkers. As the electron-donating strength of the substituent increases, the absorption bands strengthen, the emission wavelength shifts bathochromically, and the emission quantum yield increases. Moreover, fluorescence analysis of the OPVs in the solid state shows that the nature of the substituent significantly affects the inter-chromophore interactions. These results suggest that the new linkers have potential for electro-optic applications in which high emission efficiency is required, such as chemical sensing. 2015 Elsevier B.V. All rights reserved.
In search of a film with optimal antifogging properties, low density polyethylene (LDPE) was sele... more In search of a film with optimal antifogging properties, low density polyethylene (LDPE) was selected as polymeric matrix, and one of the following four additives were incorporated into the film by an extrusion process: polysorbate 80, sorbitan oleate, glycerol monooleate and glyceride mixture, each of them in 3 different concentrations. Measures of surface tension, light transmission, contact angles, and qualitative cold fogging test were made to assess the efficiency of fog resistant in all packages. The results suggest that the film with sorbitan oleate (1%) presents the best antifogging properties.
Accepted Manuscript Triphenylphosphite and ionic liquids: positive effects in the Heck cross-cou ... more Accepted Manuscript Triphenylphosphite and ionic liquids: positive effects in the Heck cross-cou pling reaction Juan C. C rdenas, Cesar A. Sierra, Luca Fadini PII: S0040-4039(10)01905 -2 DOI: 10.1016/j.tetlet.2010.10.104 Reference: TETL 38592 To appear in: Tetrahedron ...
A new block copolymer comprised of a 2,5 (p-phenylene vinylene) unit alternating with a hexamethy... more A new block copolymer comprised of a 2,5 (p-phenylene vinylene) unit alternating with a hexamethylene unit was synthetized by the Heck methodology using phosphite ligands and two different sources of palladium, with high yields and good polymerization degrees. The spectral characteristics of the polymer are in good agreement with those of its oligomer analogue and its quantum yield (as high as 0.78 vs quinine sulfate as standard) showed to be dependant on the source of palladium employed for the Heck reaction.
A simple and convenient one-pot method for simultaneously obtaining decahydroacridine-1,8-diones ... more A simple and convenient one-pot method for simultaneously obtaining decahydroacridine-1,8-diones and 1,8-dioxo-octahydroxanthene derivatives is described. A high conversion yielding both products was obtained under the reaction conditions. To understand the optical behavior of the model compounds and their potential use as antenna moieties in bichromophoric systems, the photophysical properties of all samples were studied using ultraviolet-visible absorption and steady-state fluorescence spectroscopy in methanol solutions. For the case of the acridinediones, the fluorescence spectra were found to exhibit the typical emission profile of the locally excited state, whereas, contrary to previous published experimental results, reliable fluorescence emission spectra for the xanthenes derivatives could not be obtained. On the other hand, the poor quantum yields of the synthesized decahydroacridine-1,8-diones were explained based on the benzene-like substitution effect, which favors the intersystem crossing relaxation mechanism. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications 1 for the following free supplemental resource(s): Full experimental and spectral details.]
To achieve a suitable packaging configuration, it is important first to determine the physicochem... more To achieve a suitable packaging configuration, it is important first to determine the physicochemical characteristics related to the packaged product. In this study, the physicochemical characterization of fresh purple passion fruits of three different ripening stages was carried out to determine key variables for the packaging, such as O2 consumption and CO2 -ethylene production rates. Subsequently, intermediate-ripe fruits were packaged for 21 days at 6 °C under three packaging conditions: Xtend® perforated bags, low-density polyethylene (LDPE) bags, and LDPE bags with a novel ethylene scavenger active additive (ESAA). It was observed that an equilibrium modified atmosphere was formed in the packages. For the Xtend® bags, the highest values of O2 (yo2 = 0.184 to 0.192) and lowest of CO2 (yco2 = 0.033 to 0.041) were reached, whereas for the LDPE bags with ESAA these values were moderate. In the case of ethylene, the LDPE bags showed the highest levels in the headspace (26 to 31 ppm), whereas the lowest levels were obtained in the LDPE bags with additive (2 to 4 ppm). These levels resulted in a delay in the ripening of the fruits during storage, which was verified through a sensory acceptability test that was carried out on the juice extracted from the fruits. In this sensory test, panelists identified similar characteristics between the fruits packaged with ESAA and the Xtend® bags, regarding the control fruits. The LDPE bags with the ethylene scavenger performed satisfactorily and can considerably delay the ripening, which may result in longer shelf life and conservation of fresh purple passion fruits. PRACTICAL APPLICATION: This work presents a novel packaging proposal that reduces oxygen and ethylene levels in contact with purple passion fruits. Our proposed active packaging can be used to increase the fruit shelf life by improving its conservation conditions throughout the chain of storage, transport, and distribution in the market. With this, it will be possible to reduce the fruit's losses due to senescence and to reduce the substrate consumption by using a more effective packaging system.
After an internal conflict that lasted over half a century, the detection and removal of antipers... more After an internal conflict that lasted over half a century, the detection and removal of antipersonnel landmines in Colombia have become cumbersome challenges. Antipersonnel landmines remain scattered in Colombia and with a considerable impact on the central-western region. Most of these devices are handmade (therefore, they can also be classified as improvised explosive devices) and composed of ammonium nitrate and fossil fuel blend, a mixture known as ANFO. Due to several unique factors, including concealment tactics and non-conventional manufacturing techniques employed by guerrilla fighters, the most efficient method for the detection of ANFO-based antipersonnel landmines is the use of trained canines. This review aims at describing the current chemical strategies used in the detection of ANFO-based antipersonnel landmines. First, a detailed description of the different techniques used in the detection of explosives is made. Then, all the strategies reported in the world for ant...
Acta Crystallographica Section E Crystallographic Communications, 2017
In the title compounds,N-(5-acetyl-2-methylphenyl)quinoline-2-carboxamide [C19H16N2O2, (I)],N-(5-... more In the title compounds,N-(5-acetyl-2-methylphenyl)quinoline-2-carboxamide [C19H16N2O2, (I)],N-(5-acetyl-2-bromophenyl)quinoline-2-carboxamide [C18H13BrN2O2, (II)] andN-(5-acetyl-2-ethynylphenyl)quinoline-2-carboxamide [C20H14N2O2, (III)], the quinoline ring system is essentially planar and forms a dihedral angles of 3.68 (5) (I), 5.59 (7) (II) and 1.87 (6)° (III) with the acetyl-substituted ring. The molecular structures of (I) and (III) each feature an intramolecular N—H...N hydrogen bond, forming anS(5) ring, while in (II) an intramolecular bifurcated N—H...(N,Br) hydrogen bond forms twoS(5) rings. In the crystals, weak C—H...O hydrogen bonds link molecules of (I) intoC(7) chains long [010], molecules of (II) into chains ofR22(8) rings along [110] and molecules of (III) intoC(8) chains along [010]. In (I), there are no significant π–π stacking interactions under 4 Å, but in both (II) and (III), π–π interactions link the weak hydrogen-bonded chains into layers parallel to (001) [ce...
Acta Crystallographica Section E Crystallographic Communications, 2017
In the title compound, C10H9NO2S, all the non-H atoms, except for the ethyl fragment, lie nearly ... more In the title compound, C10H9NO2S, all the non-H atoms, except for the ethyl fragment, lie nearly in the same plane. Despite the molecular planarity, the ethyl fragment presents more than one conformation, giving rise to a discrete disorder, which was modelled with two different crystallographic sites for the ethoxy O and ethoxy α-C atoms, with occupancy values of 0.5. In the crystal, the three-dimensional array is mainly directed by C—H...(O,N) interactions, giving rise to inversion dimers withR22(10) andR22(14) motifs and infinite chains running along the [100] direction.
ABSTRACT In this work, the effect of addition of kaolinite and rice husk microparticles on the wa... more ABSTRACT In this work, the effect of addition of kaolinite and rice husk microparticles on the water vapor permeability of polylactic acid (PLA) was evaluated. The PLA-composites materials were characterized by X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and optical microscopy. For the composite preparation, an experimental design was established using two factors: additive type and concentration. When evaluating the water vapor permeability of the composites, it was found that the incorporation of kaolinite at 1% and 5% reduced the permeability coefficient of PLA. Furthermore, the inclusion of 5% kaolinite showed an increase on the tensile strength of the material. By contrast, the addition of rice husk produced an increase on water vapor permeability of the material and a decrease of both the tensile strength and ductility (percent of elongation at fracture). The higher dispersion and more regular morphology of the kaolinite particles could explain the enhancement of the gas barrier. A similar thermal behavior was observed for both PLA and composite materials, confirming that no damage of these properties was caused with the incorporation of the filler particles.
Journal of the American Society for Mass Spectrometry, 2017
Phenylenevinylene oligomers (PVs) have outstanding photophysical characteristics for applications... more Phenylenevinylene oligomers (PVs) have outstanding photophysical characteristics for applications in the growing field of organic electronics. Yet, PVs are also versatile molecules, the optical and physicochemical properties of which can be tuned by manipulation of their structure. We report the synthesis, photophysical, and MS characterization of eight PV derivatives with potential value as electron transfer (ET) matrices for UV-MALDI. UV-vis analysis show the presence of strong characteristic absorption bands in the UV region and molar absorptivities at 355 nm similar or higher than those of traditional proton (CHCA) and ET (DCTB) MALDI matrices. Most of the PVs exhibit non-radiative quantum yields (φ) above 0.5, indicating favorable thermal decay. Ionization potential values (IP) for PVs, calculated by the Electron Propagator Theory (EPT), range from 6.88 to 7.96 eV, making these oligomers good candidates as matrices for ET ionization. LDI analysis of PVs shows only the presence of radical cations (M +.) in positive ion mode and absence of clusters, adducts, or protonated species; in addition, M +. threshold energies for PVs are lower than for DCTB. We also tested the performance of four selected PVs as ET MALDI matrices for analytes ranging from porphyrins and phthalocyanines to polyaromatic compounds. Two of the four PVs show S/N enhancement of 1961% to 304% in comparison to LDI, and laser energy thresholds from 0.17 μJ to 0.47 μJ compared to 0.58 μJ for DCTB. The use of PV matrices also results in lower LODs (low fmol range) whereas LDI LODs range from pmol to nmol.
aditivo antiempañante en una matriz polimérica. g representa la tensión superficial y los subíndi... more aditivo antiempañante en una matriz polimérica. g representa la tensión superficial y los subíndices s, l y v representan las interfases sólido, líquido y vapor, respectivamente.
The title compound 9-(4-hydroxybutyl)-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2... more The title compound 9-(4-hydroxybutyl)-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione was synthesized in 72% yield through a simple, convenient and environmentally friendly one-pot reaction between dimedone and 3,4-dihydro-2H-pyran in aqueous citric acid. Additionally, a plausible reaction mechanism for the formation of the target xanthene is proposed.
The title compound 1,4-di(2-butoxycarbonyl-trans-vinyl)-2,5dimethoxybenzene was synthesized in 94... more The title compound 1,4-di(2-butoxycarbonyl-trans-vinyl)-2,5dimethoxybenzene was synthesized in 94% yield through the Heck reaction between 2,5diiodo-1,4-dimethoxybenzene and n-butyl acrylate, using bis(dibenzylideneacetone) palladium(0) as homogeneous catalyst.
Three new carboxylic-acid substituted oligo-phenylenevinylenes (OPVs) with electron-donating subs... more Three new carboxylic-acid substituted oligo-phenylenevinylenes (OPVs) with electron-donating substituents in the central ring were synthesized in high yield by the Mizoroki-Heck reaction. The linkers were optically characterized by UV-vis absorption spectrophotometry, fluorescence spectroscopy in solution and the solid state, and measurement of the emission quantum yield. A comparison of substituted and unsubstituted OPVs shows that the electron-donating groups significantly affect the luminescent properties of the linkers. As the electron-donating strength of the substituent increases, the absorption bands strengthen, the emission wavelength shifts bathochromically, and the emission quantum yield increases. Moreover, fluorescence analysis of the OPVs in the solid state shows that the nature of the substituent significantly affects the inter-chromophore interactions. These results suggest that the new linkers have potential for electro-optic applications in which high emission efficiency is required, such as chemical sensing. 2015 Elsevier B.V. All rights reserved.
In search of a film with optimal antifogging properties, low density polyethylene (LDPE) was sele... more In search of a film with optimal antifogging properties, low density polyethylene (LDPE) was selected as polymeric matrix, and one of the following four additives were incorporated into the film by an extrusion process: polysorbate 80, sorbitan oleate, glycerol monooleate and glyceride mixture, each of them in 3 different concentrations. Measures of surface tension, light transmission, contact angles, and qualitative cold fogging test were made to assess the efficiency of fog resistant in all packages. The results suggest that the film with sorbitan oleate (1%) presents the best antifogging properties.
Accepted Manuscript Triphenylphosphite and ionic liquids: positive effects in the Heck cross-cou ... more Accepted Manuscript Triphenylphosphite and ionic liquids: positive effects in the Heck cross-cou pling reaction Juan C. C rdenas, Cesar A. Sierra, Luca Fadini PII: S0040-4039(10)01905 -2 DOI: 10.1016/j.tetlet.2010.10.104 Reference: TETL 38592 To appear in: Tetrahedron ...
A new block copolymer comprised of a 2,5 (p-phenylene vinylene) unit alternating with a hexamethy... more A new block copolymer comprised of a 2,5 (p-phenylene vinylene) unit alternating with a hexamethylene unit was synthetized by the Heck methodology using phosphite ligands and two different sources of palladium, with high yields and good polymerization degrees. The spectral characteristics of the polymer are in good agreement with those of its oligomer analogue and its quantum yield (as high as 0.78 vs quinine sulfate as standard) showed to be dependant on the source of palladium employed for the Heck reaction.
A simple and convenient one-pot method for simultaneously obtaining decahydroacridine-1,8-diones ... more A simple and convenient one-pot method for simultaneously obtaining decahydroacridine-1,8-diones and 1,8-dioxo-octahydroxanthene derivatives is described. A high conversion yielding both products was obtained under the reaction conditions. To understand the optical behavior of the model compounds and their potential use as antenna moieties in bichromophoric systems, the photophysical properties of all samples were studied using ultraviolet-visible absorption and steady-state fluorescence spectroscopy in methanol solutions. For the case of the acridinediones, the fluorescence spectra were found to exhibit the typical emission profile of the locally excited state, whereas, contrary to previous published experimental results, reliable fluorescence emission spectra for the xanthenes derivatives could not be obtained. On the other hand, the poor quantum yields of the synthesized decahydroacridine-1,8-diones were explained based on the benzene-like substitution effect, which favors the intersystem crossing relaxation mechanism. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications 1 for the following free supplemental resource(s): Full experimental and spectral details.]
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