The Experts below are selected from a list of 1551 Experts worldwide ranked by ideXlab platform
Marcos R V Lanza - One of the best experts on this subject based on the ideXlab platform.
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electrodeposition of wo3 on ti substrate and the influence of interfacial oxide layer generated in situ a photoelectrocatalytic degradation of Propyl Paraben
Applied Surface Science, 2019Co-Authors: Alysson S Martins, Paulo Jorge Marques Cordeirojunior, Guilherme Garcia Bessegato, Jussara F Carneiro, Maria Valnice Boldrin Zanoni, Marcos R V LanzaAbstract:Abstract Ti/TiO2-WO3 photoanode composites were successfully synthesized through a simple electrochemical deposition of WO3 films on Ti substrate. The electrochemical deposition was evaluated in the following periods: 2.5; 5; 10; 20; 30; 45 and 60 min, and led to the generation of the electrodes denoted E2.5; E5; E10; E20; E30; E45 and E60, respectively. The performance of the electrodes was assessed by monitoring the photoelectrocatalytic oxidation of 50 mg L−1 of Propyl Paraben under UV–Vis light irradiation. Due to its autoxidation, the Ti substrate was found to exert a significant influence over the photoactivity, yielding a thin and photoactive interfacial layer of titanium oxide after heat treatment at 450 °C. More importantly, the photoactivity of the electrodes was strictly dependent on the content of WO3 as well as on its interaction with titanium oxide. In a good synergy of WO3-TiO2 semiconductors, lower amounts of electrodeposited W (
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enhanced photoelectrocatalytic performance of tio2 nanotube array modified with wo3 applied to the degradation of the endocrine disruptor Propyl Paraben
Journal of Electroanalytical Chemistry, 2017Co-Authors: Alysson S Martins, Marcos R V Lanza, Luciana NunezAbstract:Abstract We report on the photoelectrocatalytic degradation of the endocrine disruptor Propyl Paraben (PPB) using a TiO 2 nanotube (TiO 2 -NT) electrode prepared via chemical anodization, and a TiO 2 -NT electrode modified with WO 3 by electrodeposition. Solutions containing 50 mg L − 1 PPB were subjected to the photoelectrocatalytic process in a 0.2 L one-compartment electrochemical cell under UV/VIS irradiation, and the effects of bias potential (+ 0.5, + 1.0 and + 1.5 V) and solution pH (3.0, 7.0 and 10) on the performances of the unmodified and modified electrodes were investigated. Scanning electron micrographs (SEM) showed that the nanotubes were highly organized and perpendicularly aligned with a mean length of 800 nm. According to energy dispersive X-ray and SEM analyses, the concentration of W in the TiO 2 -NT/WO 3 electrode was ~ 0.75% and the distribution of the modifier was continuous and homogeneous on the surface, with pores uncovered and decorated with WO 3 . The photocurrent of the TiO 2 -NT/WO 3 electrode was improved by more than 20% in relation to its unmodified counterpart. The maximum degradation efficiencies were achieved at higher applied potentials and under acidic conditions for both electrodes. However, best results were obtained using the TiO 2 -NT/WO 3 electrode with an applied potential of + 1.50 V and at pH 3. Under these conditions, more than 99% of PPB was removed in 30 min and 94% mineralization was achieved in 60 min. The photoactivity of the electrode was highly stable even after exhaustive application, indicating that WO 3 deposition is an important method for improving the properties of TiO 2 -NT electrodes as applied to organic oxidation.
Dionissios Mantzavinos - One of the best experts on this subject based on the ideXlab platform.
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synthesis and characterization of coox bivo4 photocatalysts for the degradation of Propyl Paraben
Journal of Hazardous Materials, 2019Co-Authors: Athanasia Petala, Zacharias Frontistis, Dionissios Mantzavinos, Antigoni Noe, Charalampos Drivas, Stella Kennou, Dimitris I KondaridesAbstract:Abstract Cobalt-promoted bismuth vanadate photocatalysts of variable cobalt content (0–1.0 wt.%) were synthesized and characterized with various techniques including BET, XRD, DRS, XPS and TEM. BiVO4 exists in the monoclinic scheelite structure, while cobalt addition improves the absorbance in the visible region although it does not affect the band gap energy of BiVO4. Cobalt exists in the form of well-dispersed Co3O4 nanocrystallites, which are in intimate contact with the much larger BiVO4 nanoparticles. Photocatalytic activity was evaluated for the degradation of Propyl Paraben (PP) under simulated solar radiation. The activity of pristine BiVO4 is significantly improved adding small amounts of cobalt and is maximized for the catalyst containing 0.5 wt.% Co. PP degradation in ultrapure pure water increases with increasing photocatalyst loading (100 mg/L to 1.5 g/L), and decreasing PP concentration (1600–200 μg/L). Experiments in bottled water, as well as in pure water spiked with bicarbonate and chloride ions showed little effect of non-target inorganics on degradation. Conversely, degradation is severely impeded in secondary treated wastewater. The enhancement of the photocatalytic activity of the synthesized catalysts is attributed to efficient electron-hole separation, achieved at the p-n junction formed between the p-type Co3O4 and the n-type BiVO4 semiconductors.
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degradation of Propyl Paraben by activated persulfate using iron containing magnetic carbon xerogels investigation of water matrix and process synergy effects
Environmental Science and Pollution Research, 2018Co-Authors: Maria Metheniti, Zacharias Frontistis, Rui S Ribeiro, Adrian M T Silva, Joaquim L Faria, Helder Gomes, Dionissios MantzavinosAbstract:An advanced oxidation process comprising an iron-containing magnetic carbon xerogel (CX/Fe) and persulfate was tested for the degradation of Propyl Paraben (PP), a contaminant of emerging concern, in various water matrices. Moreover, the effect of 20 kHz ultrasound or light irradiation on process performance was evaluated. The pseudo-first order degradation rate of PP was found to increase with increasing SPS concentration (25–500 mg/L) and decreasing PP concentration (1690–420 μg/L) and solution pH (9–3). Furthermore, the effect of water matrix on kinetics was detrimental depending on the complexity (i.e., wastewater, river water, bottled water) and the concentration of matrix constituents (i.e., humic acid, chloride, bicarbonate). The simultaneous use of CX/Fe and ultrasound as persulfate activators resulted in a synergistic effect, with the level of synergy (between 35 and 50%) depending on the water matrix. Conversely, coupling CX/Fe with simulated solar or UVA irradiation resulted in a cumulative effect in experiments performed in ultrapure water.
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destruction of Propyl Paraben by persulfate activated with uv a light emitting diodes
Journal of environmental chemical engineering, 2018Co-Authors: Alexandra Ioannidi, Zacharias Frontistis, Dionissios MantzavinosAbstract:Abstract UV-A light emitting diodes (LEDs: 10 W of nominal power, 7.9 × 10−7 einstein/(L.s) photon flux) were employed as the radiation source to activate sodium persulfate (SPS) for the degradation of endocrine disruptor Propyl Paraben (PP). Experiments in ultrapure water (UPW) were conducted varying SPS concentration between 0 and 500 mg/L, PP concentration between 100 and 800 μg/L, initial solution pH between 3.2 and 9.2, as well as adding various organic (alcohols and humic acid) and inorganic (bicarbonate, chloride), non-target species. Besides UPW, experiments were performed in two actual matrices, i.e. secondary treated wastewater and bottled water. Degradation was found to increase with increasing SPS concentration and decreasing PP concentration, while it was favored as near-neutral, inherent solution pH. The addition of methanol and t-butanol, known radical scavengers, partly restricted the reaction, thus implying that both sulfate and hydroxyl radicals are formed and participate in PP degradation. The addition of humic acid in UPW completely quenched the reaction and so did the use of wastewater as the water matrix. Less significant were the effects of bicarbonate and chloride. SPS can also be activated by the UV-A part of simulated solar radiation (7.3 10−7 einstein/(L s) photon flux), potentially improving process sustainability.
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Synthesis and characterization of CoOx/BiVO4 photocatalysts for the degradation of Propyl Paraben.
Journal of hazardous materials, 2018Co-Authors: Athanasia Petala, Zacharias Frontistis, Dionissios Mantzavinos, Antigoni Noe, Charalampos Drivas, Stella Kennou, Dimitris I KondaridesAbstract:Abstract Cobalt-promoted bismuth vanadate photocatalysts of variable cobalt content (0–1.0 wt.%) were synthesized and characterized with various techniques including BET, XRD, DRS, XPS and TEM. BiVO4 exists in the monoclinic scheelite structure, while cobalt addition improves the absorbance in the visible region although it does not affect the band gap energy of BiVO4. Cobalt exists in the form of well-dispersed Co3O4 nanocrystallites, which are in intimate contact with the much larger BiVO4 nanoparticles. Photocatalytic activity was evaluated for the degradation of Propyl Paraben (PP) under simulated solar radiation. The activity of pristine BiVO4 is significantly improved adding small amounts of cobalt and is maximized for the catalyst containing 0.5 wt.% Co. PP degradation in ultrapure pure water increases with increasing photocatalyst loading (100 mg/L to 1.5 g/L), and decreasing PP concentration (1600–200 μg/L). Experiments in bottled water, as well as in pure water spiked with bicarbonate and chloride ions showed little effect of non-target inorganics on degradation. Conversely, degradation is severely impeded in secondary treated wastewater. The enhancement of the photocatalytic activity of the synthesized catalysts is attributed to efficient electron-hole separation, achieved at the p-n junction formed between the p-type Co3O4 and the n-type BiVO4 semiconductors.
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solar photocatalytic degradation of Propyl Paraben in al doped tio2 suspensions
Catalysis Today, 2017Co-Authors: Sophia Kotzamanidi, Zacharias Frontistis, Vassilios Binas, G Kiriakidis, Dionissios MantzavinosAbstract:Abstract The photocatalytic degradation of Propyl Paraben (PP) over Al-doped TiO2 suspensions under simulated solar radiation was investigated. The catalysts were prepared by a co-precipitation method with the dopant content varying from 0.04 to 2 wt%. The catalyst with 0.04 wt% dopant was more effective than the rest, presumably due to a more efficient separation of the photogenerated charges associated with a greater crystallite size. Subsequent experiments with this catalyst showed that the rate of PP degradation (i) generally increased with increasing catalyst concentration in the range 125–1000 mg/L, and decreasing PP concentration (in the range 210–1687 μg/L), and (ii) was impeded at alkaline conditions (pH range 3–9). Moreover, degradation in pure water was always faster than in actual (i.e. bottled water, treated wastewater, surface water) or synthetic (i.e. pure water spiked with humic acid, t-butanol, chloride and bicarbonate ions) water matrices, pinpointing the competitive behavior of non-target water constituents. Conversely, the addition of persulfate had a beneficial effect on the rate of degradation since it acted both as electron acceptor and a source of extra sulfate radicals.
Zacharias Frontistis - One of the best experts on this subject based on the ideXlab platform.
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Sonoelectrochemical Degradation of Propyl Paraben: An Examination of the Synergy in Different Water Matrices.
International journal of environmental research and public health, 2020Co-Authors: Zacharias FrontistisAbstract:The synergistic action of anodic oxidation using boron-doped diamond and low-frequency ultrasound in different water matrices and operating conditions for the decomposition of the emerging contaminant Propyl Paraben was investigated. The degree of synergy was found to decrease with an increase in current in the range 1.25–6.25 mA/cm2 or the ultrasound power until 36 W/L, where a further decrease was observed. Despite the fact that the increased Propyl Paraben concentration decreased the observed kinetic constant for both the separated and the hybrid process, the degree of synergy was increased from 37.3 to 43.4% for 0.5 and 2 mg/L Propyl Paraben, respectively. Bicarbonates (100–250 mg/L) or humic acid (10–20 mg/L) enhanced the synergy significantly by up to 55.8%, due to the higher demand for reactive oxygen species. The presence of chloride ions decreased the observed synergistic action in comparison with ultrapure water, possibly due to the electro-generation of active chlorine that diffuses to the bulk solution. The same behavior was observed with the secondary effluent that contained almost 68 mg/L of chlorides. The efficiency was favored in a neutral medium, while the hybrid process was delayed in alkaline conditions.
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synthesis and characterization of coox bivo4 photocatalysts for the degradation of Propyl Paraben
Journal of Hazardous Materials, 2019Co-Authors: Athanasia Petala, Zacharias Frontistis, Dionissios Mantzavinos, Antigoni Noe, Charalampos Drivas, Stella Kennou, Dimitris I KondaridesAbstract:Abstract Cobalt-promoted bismuth vanadate photocatalysts of variable cobalt content (0–1.0 wt.%) were synthesized and characterized with various techniques including BET, XRD, DRS, XPS and TEM. BiVO4 exists in the monoclinic scheelite structure, while cobalt addition improves the absorbance in the visible region although it does not affect the band gap energy of BiVO4. Cobalt exists in the form of well-dispersed Co3O4 nanocrystallites, which are in intimate contact with the much larger BiVO4 nanoparticles. Photocatalytic activity was evaluated for the degradation of Propyl Paraben (PP) under simulated solar radiation. The activity of pristine BiVO4 is significantly improved adding small amounts of cobalt and is maximized for the catalyst containing 0.5 wt.% Co. PP degradation in ultrapure pure water increases with increasing photocatalyst loading (100 mg/L to 1.5 g/L), and decreasing PP concentration (1600–200 μg/L). Experiments in bottled water, as well as in pure water spiked with bicarbonate and chloride ions showed little effect of non-target inorganics on degradation. Conversely, degradation is severely impeded in secondary treated wastewater. The enhancement of the photocatalytic activity of the synthesized catalysts is attributed to efficient electron-hole separation, achieved at the p-n junction formed between the p-type Co3O4 and the n-type BiVO4 semiconductors.
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degradation of Propyl Paraben by activated persulfate using iron containing magnetic carbon xerogels investigation of water matrix and process synergy effects
Environmental Science and Pollution Research, 2018Co-Authors: Maria Metheniti, Zacharias Frontistis, Rui S Ribeiro, Adrian M T Silva, Joaquim L Faria, Helder Gomes, Dionissios MantzavinosAbstract:An advanced oxidation process comprising an iron-containing magnetic carbon xerogel (CX/Fe) and persulfate was tested for the degradation of Propyl Paraben (PP), a contaminant of emerging concern, in various water matrices. Moreover, the effect of 20 kHz ultrasound or light irradiation on process performance was evaluated. The pseudo-first order degradation rate of PP was found to increase with increasing SPS concentration (25–500 mg/L) and decreasing PP concentration (1690–420 μg/L) and solution pH (9–3). Furthermore, the effect of water matrix on kinetics was detrimental depending on the complexity (i.e., wastewater, river water, bottled water) and the concentration of matrix constituents (i.e., humic acid, chloride, bicarbonate). The simultaneous use of CX/Fe and ultrasound as persulfate activators resulted in a synergistic effect, with the level of synergy (between 35 and 50%) depending on the water matrix. Conversely, coupling CX/Fe with simulated solar or UVA irradiation resulted in a cumulative effect in experiments performed in ultrapure water.
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destruction of Propyl Paraben by persulfate activated with uv a light emitting diodes
Journal of environmental chemical engineering, 2018Co-Authors: Alexandra Ioannidi, Zacharias Frontistis, Dionissios MantzavinosAbstract:Abstract UV-A light emitting diodes (LEDs: 10 W of nominal power, 7.9 × 10−7 einstein/(L.s) photon flux) were employed as the radiation source to activate sodium persulfate (SPS) for the degradation of endocrine disruptor Propyl Paraben (PP). Experiments in ultrapure water (UPW) were conducted varying SPS concentration between 0 and 500 mg/L, PP concentration between 100 and 800 μg/L, initial solution pH between 3.2 and 9.2, as well as adding various organic (alcohols and humic acid) and inorganic (bicarbonate, chloride), non-target species. Besides UPW, experiments were performed in two actual matrices, i.e. secondary treated wastewater and bottled water. Degradation was found to increase with increasing SPS concentration and decreasing PP concentration, while it was favored as near-neutral, inherent solution pH. The addition of methanol and t-butanol, known radical scavengers, partly restricted the reaction, thus implying that both sulfate and hydroxyl radicals are formed and participate in PP degradation. The addition of humic acid in UPW completely quenched the reaction and so did the use of wastewater as the water matrix. Less significant were the effects of bicarbonate and chloride. SPS can also be activated by the UV-A part of simulated solar radiation (7.3 10−7 einstein/(L s) photon flux), potentially improving process sustainability.
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Synthesis and characterization of CoOx/BiVO4 photocatalysts for the degradation of Propyl Paraben.
Journal of hazardous materials, 2018Co-Authors: Athanasia Petala, Zacharias Frontistis, Dionissios Mantzavinos, Antigoni Noe, Charalampos Drivas, Stella Kennou, Dimitris I KondaridesAbstract:Abstract Cobalt-promoted bismuth vanadate photocatalysts of variable cobalt content (0–1.0 wt.%) were synthesized and characterized with various techniques including BET, XRD, DRS, XPS and TEM. BiVO4 exists in the monoclinic scheelite structure, while cobalt addition improves the absorbance in the visible region although it does not affect the band gap energy of BiVO4. Cobalt exists in the form of well-dispersed Co3O4 nanocrystallites, which are in intimate contact with the much larger BiVO4 nanoparticles. Photocatalytic activity was evaluated for the degradation of Propyl Paraben (PP) under simulated solar radiation. The activity of pristine BiVO4 is significantly improved adding small amounts of cobalt and is maximized for the catalyst containing 0.5 wt.% Co. PP degradation in ultrapure pure water increases with increasing photocatalyst loading (100 mg/L to 1.5 g/L), and decreasing PP concentration (1600–200 μg/L). Experiments in bottled water, as well as in pure water spiked with bicarbonate and chloride ions showed little effect of non-target inorganics on degradation. Conversely, degradation is severely impeded in secondary treated wastewater. The enhancement of the photocatalytic activity of the synthesized catalysts is attributed to efficient electron-hole separation, achieved at the p-n junction formed between the p-type Co3O4 and the n-type BiVO4 semiconductors.
Alysson S Martins - One of the best experts on this subject based on the ideXlab platform.
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electrodeposition of wo3 on ti substrate and the influence of interfacial oxide layer generated in situ a photoelectrocatalytic degradation of Propyl Paraben
Applied Surface Science, 2019Co-Authors: Alysson S Martins, Paulo Jorge Marques Cordeirojunior, Guilherme Garcia Bessegato, Jussara F Carneiro, Maria Valnice Boldrin Zanoni, Marcos R V LanzaAbstract:Abstract Ti/TiO2-WO3 photoanode composites were successfully synthesized through a simple electrochemical deposition of WO3 films on Ti substrate. The electrochemical deposition was evaluated in the following periods: 2.5; 5; 10; 20; 30; 45 and 60 min, and led to the generation of the electrodes denoted E2.5; E5; E10; E20; E30; E45 and E60, respectively. The performance of the electrodes was assessed by monitoring the photoelectrocatalytic oxidation of 50 mg L−1 of Propyl Paraben under UV–Vis light irradiation. Due to its autoxidation, the Ti substrate was found to exert a significant influence over the photoactivity, yielding a thin and photoactive interfacial layer of titanium oxide after heat treatment at 450 °C. More importantly, the photoactivity of the electrodes was strictly dependent on the content of WO3 as well as on its interaction with titanium oxide. In a good synergy of WO3-TiO2 semiconductors, lower amounts of electrodeposited W (
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enhanced photoelectrocatalytic performance of tio2 nanotube array modified with wo3 applied to the degradation of the endocrine disruptor Propyl Paraben
Journal of Electroanalytical Chemistry, 2017Co-Authors: Alysson S Martins, Marcos R V Lanza, Luciana NunezAbstract:Abstract We report on the photoelectrocatalytic degradation of the endocrine disruptor Propyl Paraben (PPB) using a TiO 2 nanotube (TiO 2 -NT) electrode prepared via chemical anodization, and a TiO 2 -NT electrode modified with WO 3 by electrodeposition. Solutions containing 50 mg L − 1 PPB were subjected to the photoelectrocatalytic process in a 0.2 L one-compartment electrochemical cell under UV/VIS irradiation, and the effects of bias potential (+ 0.5, + 1.0 and + 1.5 V) and solution pH (3.0, 7.0 and 10) on the performances of the unmodified and modified electrodes were investigated. Scanning electron micrographs (SEM) showed that the nanotubes were highly organized and perpendicularly aligned with a mean length of 800 nm. According to energy dispersive X-ray and SEM analyses, the concentration of W in the TiO 2 -NT/WO 3 electrode was ~ 0.75% and the distribution of the modifier was continuous and homogeneous on the surface, with pores uncovered and decorated with WO 3 . The photocurrent of the TiO 2 -NT/WO 3 electrode was improved by more than 20% in relation to its unmodified counterpart. The maximum degradation efficiencies were achieved at higher applied potentials and under acidic conditions for both electrodes. However, best results were obtained using the TiO 2 -NT/WO 3 electrode with an applied potential of + 1.50 V and at pH 3. Under these conditions, more than 99% of PPB was removed in 30 min and 94% mineralization was achieved in 60 min. The photoactivity of the electrode was highly stable even after exhaustive application, indicating that WO 3 deposition is an important method for improving the properties of TiO 2 -NT electrodes as applied to organic oxidation.
Lata Panicker - One of the best experts on this subject based on the ideXlab platform.
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Propyl Paraben-induced changes in dipalmitoyl phosphatidylethanolamine vesicles
Journal of Thermal Analysis and Calorimetry, 2010Co-Authors: Lata PanickerAbstract:This article reports the influence of the preservative, Propyl Paraben (PPB), on the phase transition and dynamics of dipalmitoyl phosphatidylethanolamine (DPPE) vesicles both in multilamellar vesicular (MLV) and unilamellar vesicular (ULV) forms using DSC and (^1H and ^31P) NMR. DSC results indicate that the mechanism by which PPB interacts with DPPE vesicles is similar in both forms. Addition of PPB to DPPE dispersion results in lowering of the gel to liquid crystalline phase transition temperature ( T _m) and consequently increases DPPE headgroup fluidity. At high PPB concentration, additional transitions are observed whose intensity increases with increasing PPB concentration. DSC and NMR data indicate that the PPB molecules get intercalated between the DPPE headgroups as the polar group of the PPB molecules interacts with the polar group of PE, and the alkyl chain of PPB penetrates into the acyl chain region. The interesting finding with MLV is that the gel phase of DPPE in the presence of PPB, on equilibration at 25 °C, transforms to a stable crystalline subgel phases and whose intensity increases with increasing PPB concentration. The effect of inclusion of cholesterol in the PPB-free and PPB-doped DPPE dispersion was also studied.
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Propyl Paraben-induced changes in dipalmitoyl phosphatidylethanolamine vesicles
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: Lata PanickerAbstract:Abstract This article reports the influence of the preservative, Propyl Paraben (PPB), on the phase transition and dynamics of dipalmitoyl phosphatidylethanolamine (DPPE) vesicles both in multilamellar vesicular (MLV) and unilamellar vesicular (ULV) forms using DSC and (1H and 31P) NMR. DSC results indicate that the mechanism by which PPB interacts with DPPE vesicles is similar in both forms. Addition of PPB to DPPE dispersion results in lowering of the gel to liquid crystalline phase transition temperature (T m) and consequently increases DPPE headgroup fluidity. At high PPB concentration, additional transitions are observed whose intensity increases with increasing PPB concentration. DSC and NMR data indicate that the PPB molecules get intercalated between the DPPE headgroups as the polar group of the PPB molecules interacts with the polar group of PE, and the alkyl chain of PPB penetrates into the acyl chain region. The interesting finding with MLV is that the gel phase of DPPE in the presence of PPB, ...
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Interaction of Propyl Paraben with dipalmitoyl phosphatidylcholine bilayer : A differential scanning calorimetry and nuclear magnetic resonance study
Colloids and surfaces. B Biointerfaces, 2007Co-Authors: Lata PanickerAbstract:Abstract The influence of the preservative, Propyl Paraben (PPB) on the biophysical properties of dipalmitoyl phosphatidyl choline (DPPC) vesicles, both in multilamellar vesicle (MLV) and unilamellar vesicle (ULV) forms, has been studied using DSC and ( 1 H and 31 P) NMR. The mechanism by which PPB interacts with DPPC bilayers was found to be independent of the morphological organization of the lipid bilayer. Incorporation of PPB in DPPC vesicles causes a significant depression in the transition temperature and enthalpy of both the pre-transition (PT) and the gel to liquid crystalline transition. The presence of the PPB also reduces the co-operativity of these transitions. However, at high PPB concentration the PT disappears. DSC and NMR findings indicate that: (i) PPB is bound strongly to the lipid bilayer leading to increased headgroup fluidity due to reduced headgroup–headgroup interaction and (ii) the PPB molecules are intercalated between the DPPC polar headgroups with its alkyl chain penetrate into the co-operative region. MLV incorporated with high PPB concentration shows additional transitions whose intensity increases with increasing PPB concentration. This phase segregation observed could probably be due to co-existence of PPB-rich and PPB-poor phospholipid domains within the bilayers. The effect of inclusion of cholesterol in the PPB-free and PPB-doped DPPC dispersion was also studied. Equilibration studies suggest that PPB molecules are very strongly bound and remain intercalated between the polar headgroup for prolonged time.
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Effect of Propyl Paraben on the dipalmitoyl phosphatidic acid vesicles
Journal of colloid and interface science, 2007Co-Authors: Lata PanickerAbstract:The effect of the preservative Propyl Paraben (PPB) on the phase transition and dynamics of dipalmitoyl phosphatidic acid (DPPA)-buffer (pH 7.4/9.3) vesicles has been studied using DSC and ((1)H and (31)P) NMR. These investigations were carried out with DPPA dispersion in both multilamellar vesicular (MLV) and unilamellar vesicular (ULV) forms. DSC results indicate that the mechanism by which PPB interact with the DPPA vesicles is similar in MLV and ULV and is independent of pH of the buffer used to form the dispersion. However, for a given concentration of PPB, the perturbation in DPPA bilayer is more when the dispersion is prepared in buffer pH 7.4. PPB affected both the thermotropic phase transition and the molecular mobility of the DPPA membrane. In the presence of PPB, the gel to liquid crystalline phase transition temperature (T(m)) of the DPPA vesicles decreases hence increases membrane fluidity due to reduced headgroup-headgroup interaction. For all concentrations, the PPB molecules seem to get intercalated between the polar groups of the phospholipids with its alkyl chain penetrating into the co-operative region. At high PPB concentration, additional transitions are observed whose intensity increases with increasing PPB concentration. The large enthalpy values obtained at high PPB concentration suggest that presence of PPB makes the DPPA bilayer more ordered (rigid). The interesting finding obtained with MLV is that the stable gel phase of DPPA-buffer (pH 9.3/7.4) system in the presence of high PPB concentration becomes a metastable gel phase, this metastable gel phase on equilibration at 25 degrees C or when cooled to -20 degrees C transforms to a stable crystalline phase(s). The intensity of this new phase(s) increases with increasing PPB concentration. However, the transition temperatures of these new phases are not significantly changed with increasing PPB concentration. The effect of inclusion of cholesterol in the PPB-free and PPB-doped DPPA dispersion was also studied.
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Drug-Lipid Interactions in the Model Membrane, Dppc-Water: A DSC and Proton NMR Study
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 1996Co-Authors: K. Usha Deniz, Lata Panicker, P. S. Parvathanathan, Geeta Datta, Subramanian Vivekanandan, K. V. Ramanathan, C.l. KhetrapalAbstract:Abstract The interactions of the keratolytic drug Salicylic Acid (SA) and the antifungal drugs Methyl Paraben (MPB) and Propyl Paraben (PPB) with the model membrane, DPPC-Water, have been studied using DSC and 1H NMR. The results show that these drug molecules are situated near the membrane interface with their polar group (s) interacting with the vicinal water, while the aromatic regions and the methyl and Propyl groups of MPB and PPB interact with the neighbouring hydrophobic regions of the DPPC molecule. The strength of interaction of the aromatic group is in the order PPB > MPB > SA.
