Institute of Chemical Engineering science

Platani, Greece

Institute of Chemical Engineering science

Platani, Greece
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Kalampounias A.G.,University of Ioannina | Kalampounias A.G.,Institute of Chemical Engineering science
Chemical Papers | Year: 2017

Raman spectroscopy was used to probe the vibrational dynamics of LnX3 molten salts for a variety of lanthanides (Ln = La, Nd, Gd, Dy, Ho, Y) and halides (X = Br, Cl). Analysis of the line profiles has been performed by employing a time-correlation function with an analytical counterpart in the frequency domain, which permits fitting of specific vibrational features in an effort to elucidate the structure and obtain dynamical information in parallel. It is established using 2-D correlation methodology that all lanthanide halides exhibit similar structural properties and analogous vibrational relaxation and frequency modulation times. The structure of the lanthanide halide melts studied in this work is composed of distorted octahedra that constitute a loose network as reported before. The rigidity of the network is related to the splitting of the P1 and P2 bands, attributed to the ν1(A1g) and ν5(F2g) fundamental octahedral modes, and increases with increasing distortion of the octahedra in the sequence La → Y and Cl → Br. A variety of picosecond dynamics models have been tested and found that only the Rothschild approach complies well with the experimental data assuming that the environmental modulation is described by a stretched exponential decay. The experimental results are discussed in terms of theoretical models providing insights in the inter-molecular coupling mechanisms. © 2017 Institute of Chemistry, Slovak Academy of Sciences

Kostenidou E.,Institute of Chemical Engineering science | Kaltsonoudis C.,Institute of Chemical Engineering science | Kaltsonoudis C.,University of Patras | Tsiflikiotou M.,Institute of Chemical Engineering science | And 7 more authors.
Atmospheric Chemistry and Physics | Year: 2013

Aerosol produced during the burning of olive tree branches was characterized with both direct source sampling (using a mobile smog chamber) and with ambient measurements during the burning season. The fresh particles were composed of 80% organic matter, 8-10% black carbon (BC), 5% potassium, 3-4% sulfate, 2-3% nitrate and 0.8% chloride. Almost half of the fresh olive tree branches burning organic aerosol (otBB-OA) consisted of alkane groups. Their mode diameter was close to 70 nm. The oxygen to carbon (O : C) ratio of the fresh otBB-OA was 0.29 ± 0.04. The mass fraction of levoglucosan in PM1 was 0.034-0.043, relatively low in comparison with most fuel types. This may lead to an underestimation of the otBB-OA contribution if levoglucosan is being used as a wood burning tracer. Chemical aging was observed during smog chamber experiments, as f 44 and O : C ratio increased, due to reactions with OH radicals and O3. The otBB-OA AMS mass spectrum differs from the other published biomass burning spectra, with a main difference at m/z 60, used as levoglucosan tracer. In addition to particles, volatile organic compounds (VOCs) such as methanol, acetonitrile, acrolein, benzene, toluene and xylenes are also emitted. Positive matrix factorization (PMF) was applied to the ambient organic aerosol data and 3 factors could be identified: OOA (oxygenated organic aerosol, 55%), HOA (hydrocarbon-like organic aerosol, 11.3%) and otBB-OA 33.7%. The fresh chamber otBB-OA AMS spectrum is close to the PMF otBB-OA spectrum and resembles the ambient mass spectrum during olive tree branches burning periods. We estimated an otBB-OA emission factor of 3.5 ± 0.9 g kg-1. Assuming that half of the olive tree branches pruned is burned in Greece, 2300 ± 600 tons of otBB-OA are emitted every year. This activity is one of the most important fine aerosol sources during the winter months in Mediterranean countries. © 2013 Author(s).

Popescu M.-T.,University of Patras | Tsitsilianis C.,University of Patras | Tsitsilianis C.,Institute of Chemical Engineering science
ACS Macro Letters | Year: 2013

The present study reports on the development of composite gold nanoparticles (AuNPs)/polymersome formulations, based on pH-responsive biocompatible polymer vesicles integrating prefunctionalized AuNPs, doped with a hydrophobic model probe for improved multimodal drug delivery. The polymer vesicles were prepared from an amphiphilic pentablock terpolymer poly(ε-caprolactone)-b-poly(ethylene oxide)-b-poly(2-vinylpyridine)-b- poly(ethylene oxide)-b-poly(ε-caprolactone) (PCL-PEO-P2VP-PEO-PCL), consisting of a pH-sensitive and biodegradable P2VP/PCL membrane, surrounded by neutral hydrophilic PEO looping chains. Additionally, partial quaternization of the P2VP block has been performed to introduce cationic moieties. Water-dispersible AuNPs carrying a hydrophobic molecule were encapsulated in the hydrophilic aqueous lumen of the vesicles, and the release was monitored at pH conditions simulating physiological and tumor environments. The complex delivery of the cargos from these vesicles showed improved and controlled kinetics relative to the individual nanocarriers, which could be further tuned by pH and chemical modification of the membrane forming block. © 2013 American Chemical Society.

Antonopoulou G.,Institute of Chemical Engineering science | Lyberatos G.,National Technical University of Athens
Waste and Biomass Valorization | Year: 2013

In this work, the effect of pretreatment on the biochemical methane potential (BMP) of sweet sorghum biomass was determined. Various pretreatment methods, such as thermal (1 h at 121 °C), enzymatic [through the addition of the enzyme Celluclast 1.5L (Cellulase from Trichoderma reesei , ATCC 26921) or by the addition of a mixture of Celluclast 1.5L and Novozyme 188 (Cellobiase from Aspergillus niger) at a ratio of (3:1)], chemical [through alkali (NaOH) or acid (H2SO4) addition, at concentrations of 0-2% w/v] or combination of the above methods (thermal acid and thermal alkaline) were tested, in order to evaluate their effect on carbohydrate solubilization (saccharification) and on the methane yield. The experimental results showed that thermal acid treatment and enzymatic treatment for all enzymes concentrations tested improved saccharification. Under thermal alkaline treatment at NaOH concentrations above 0.5% w/v, a significant decrease in soluble carbohydrates concentration was observed meaning that a high portion of sugars also contained in sorghum biomass was degraded or was transformed into other components. BMP experiments showed that the chemical pretreatment methods did not enhance methane generation compared to the raw substrates. This could be attributed either to inhibitory compounds released during pretreatment, or to high salts (cations of sodium during alkaline treatment) concentration, causing in both cases methanogenic bacteria inhibition. On the other hand, thermal treatment improved the methane yield from 253 to 288 LCH4/kg sorghum. During enzymatic pretreatment, the methane production was enhanced either with only one or with the mixture of enzymes. © Springer Science+Business Media 2012.

Tremouli A.,University of Patras | Antonopoulou G.,University of Patras | Antonopoulou G.,Institute of Chemical Engineering science | Bebelis S.,University of Patras | And 2 more authors.
Bioresource Technology | Year: 2013

Electricity production from filter sterilized cheese whey at different organic loads (0.35, 0.7, 1.5, 2.7 and 6.7gCOD/L respectively) was investigated in a two-chamber microbial fuel cell (MFC). The best performance of the cell was observed at the highest concentration of the pretreated (filter sterilized) cheese whey (6.7gCOD/L) corresponding to a maximum power density of approximately 46mW/m2. Experiments using glucose (0.35gCOD/L) were also performed for comparison reasons. The study of the open-circuit impedance characteristics of the MFC and of the individual electrodes revealed that the open-circuit impedance of the MFC depended to practically the same extent on both the ohmic resistance between the anode and cathode and the overall polarization resistance. The polarization resistance of the MFC decreased significantly under closed-circuit conditions, which in turn implies that the ohmic overpotential is the main contribution to the energy losses in two-chamber MFCs. © 2013 Elsevier Ltd.

Trump E.R.,Carnegie Mellon University | Fountoukis C.,Institute of Chemical Engineering science | Donahue N.M.,Carnegie Mellon University | Pandis S.N.,Carnegie Mellon University | Pandis S.N.,University of Patras
Atmospheric Environment | Year: 2015

Atmospheric chemical transport models (CTMs) have often serious difficulties reproducing the observed aerosol nitrate levels. We hypothesize that one of the reasons for these errors is their treatment of the competition between the accumulation and coarse-mode particles for the condensing nitric acid. The hybrid mass transfer method is used in the CTM PMCAMx to test this hypothesis. The simulation approach combines the dynamic calculation of mass transfer to coarse-mode particles while maintaining computational efficiency by assuming that the fine mode particles are in equilibrium. The resulting model is applied to Europe and evaluated for the period of May 2008 against ground-based and airborne Aerosol Mass Spectrometer measurements from the EUCAARI campaign.PMCAMx using the default equilibrium approach to calculate the partitioning of semi-volatile PM components between the gas and particle phases seriously overpredicts PM1 nitrate levels especially for locations in which there were relatively high coarse-mode particle concentrations (significant sea-salt or dust concentrations). This shortcoming was especially apparent for the Mace Head site in Ireland, where a large amount of nitrate was associated with sea-salt. The improved simulation of the coarse-mode particle chemistry results in significant improvement of the predictions of PM1 nitrate and ammonium. Sea-salt emissions in areas with high nitric acid levels reduce the PM1 nitrate concentrations. © 2014 Elsevier Ltd.

Muktadirul Bari Chowdhury A.K.M.,University of Patras | Akratos C.S.,University of Patras | Vayenas D.V.,University of Patras | Vayenas D.V.,Institute of Chemical Engineering science | And 2 more authors.
International Biodeterioration and Biodegradation | Year: 2013

Olive mill wastes exacerbate environmental problems in Mediterranean countries. These wastes are highly phytotoxic and contain phenolic compounds, lipids and organic acids. They also contain high percentages of organic matter and a vast range of plant nutrients that could be reused as fertilizers for sustainable agricultural practices. In this paper, recent research on composting wastes of 2-phase and 3-phase olive mills is reviewed, concentrating on factors affecting composting such as bulking agents, aeration strategy, physicochemical characteristics (duration of the thermophilic phase, moisture content, organic matter, volatile solids, total organic carbon, water soluble carbon, total nitrogen, total phosphorus, potassium, C/N ratio, phenols and the humification process), and phytotoxicity. The review highlights the effects of composting operational factors (bulking agent, additives, and aeration strategy) on the physicochemical characteristics of the final compost, and the production of a good quality soil amender or fertilizer. © 2013 Elsevier Ltd.

Mourtas S.,University of Patras | Lazar A.N.,Laboratoire Of Neuropathologie Escourolle | Lazar A.N.,French Institute of Health and Medical Research | Markoutsa E.,University of Patras | And 4 more authors.
European Journal of Medicinal Chemistry | Year: 2014

With the objective to formulate multifunctional nanosized liposomes to target amyloid deposits in Alzheimer Disease (AD) brains, a lipid-PEG-curcumin derivative was synthesized and characterized. Multifunctional liposomes incorporating the curcumin derivative and additionally decorated with a Blood Brain Barrier (BBB) transport mediator (anti-Transferin antibody) were prepared and characterized. The fluorescence intensity of curcumin derivative was found to increase notably when the curcumin moiety was in the form of a diisopropylethylamine (DIPEA) salt. Both curcumin-derivative liposomes and curcumin-derivative Anti-TrF liposomes showed a high affinity for the amyloid deposits, on post-mortem brains samples of AD patients. The ability of both liposomes to delay Aβ1-42 peptide aggregation was confirmed by Thioflavin assay. However, the decoration of the curcumin-derivative liposomes with the Anti-TrF improved significantly the intake by the BBB cellular model. Results verify that the attachment of an antibody on the curcumin-liposome surface does not block deposit staining or prevention of Aβ aggregation, while the presence of the curcumin-PEG-lipid conjugate does not reduce their brain-targeting capability substantially, proving the potential of such multifunctional NLs for application in Alzheimer disease treatment and diagnosis. © 2014 Elsevier Masson SAS. All rights reserved.

Jaksic M.M.,Institute of Chemical Engineering science | Jaksic M.M.,University of Belgrade | Botton G.A.,McMaster University | Papakonstantinou G.D.,Institute of Chemical Engineering science | And 2 more authors.
Journal of Physical Chemistry C | Year: 2014

Surface in and ex situ analysis have shown that in the course of cathodic oxygen reduction (ORR), all along the reversible potential range (the low slope Tafel plots, about 30 mVs/dec), nanostructured Pt electrocatalyst is covered by the interfering primary (Pt-OH) and surface (Pt=O) oxide mixture, while the higher polarization (120 mVs/dec) characterizes electrocatalytic surface deprived from these oxides and, consequently, the reaction mechanism of direct electron exchange on clean electrode surface. The substantial difference between the standard RHE (reversible hydrogen electrode) and ROE (reversible oxygen electrode), is that the former implies spontaneous hydrogen adsorption, fast H-adatoms (Pt-H) effusion and reversible electrode behavior (Pt(H 2)/Pt-H/H3O+), while the latter features the strong irreversible Pt=O adsorptive strength, and which is more significant, missing the Pt-OH spillover within the critical potential range between the primary oxide adsorption/desorption peaks position and oxygen evolving limits in both potentiodynamic scan directions (or the imposed polarization energy barrier of about 600 mVs). Since the Pt-OH presence and spillover are unavoidable decisive and indispensable for establishing the ROE properties, and thermodynamic electrode equilibrium (Pt(O2)/Pt-OH/Pt=O/OH -), within the pronounced high polarization broad potential range, such spillover species has the same meaning and significance for the ROE as Pt-H plays for the RHE. Thence, to fill such a high polarization gap, the guiding concept implies homogeneous nanostructured distribution and selective grafting while interactive hypo-hyper-d-d-interelectronic bonding of Pt nanoclusters upon various mixed valence hypo-d-oxide supports, primarily Nb2O 5,TiO2 (or Ta2O5,TiO2), because of their much thermally advanced electronic conductivity and extra high stability. In such a constellation, nanoparticles of Pt and solid oxides establish the so-called SMSIs (strong metal-support interactions), the strongest ones in all of chemistry, together with advanced electron conductive transfer, while the exposed surface of the latter undergoes spontaneous dissociative adsorption of water molecules (Nb2O5 → 2 Nb(OH) 5), and thereby becomes, along with continuous further water vapor supply, the undisturbed and almost unlimited, (alike electrons in metals) renewable latent storage and spillover source of the Pt-OH all along the potential axis between oxygen and hydrogen evolving limits, with inexhaustible abilities of further optimizations. The reversible alterpolar changes instantaneously result by the spillover of H-adatoms with corresponding bronze type (Pt/HxNbO5, x ≈ 0.3) electrocatalysts under cathodic, and/or its hydrated state (Pt/Nb(OH)5), responsible for Pt-OH effusion, under anodic polarization. This way there establishes the reversibly revertible alterpolar bronze features (Pt/HxNbO 5 ↔ Pt/Nb(OH)5), as the thermodynamic equilibrium, and thereby substantially advanced electrocatalytic properties of these composite interactive electrocatalysts for both oxygen and hydrogen electrode reactions, in particular unique and superior for the revertible (proton exchange membrane fuel cell (PEMFC) versus water electrolysis (WE)) cells. © 2014 American Chemical Society.

Iatridi Z.,University of Patras | Iatridi Z.,Institute of Chemical Engineering science | Tsitsilianis C.,University of Patras | Tsitsilianis C.,Institute of Chemical Engineering science
Soft Matter | Year: 2013

We present a unique multisegmented, heteroarm star block terpolymer that can be used as an effective dispersing agent for multiwalled carbon nanotubes in aqueous media. The (polystyrene)22(poly(2-vinylpyridine)-b- poly(acrylic acid))22, PS22(P2VP-b-PAA)22, star terpolymer exhibits a pH responsive self-assembly behavior in aqueous solution, due to the ampholytic nature of its diblock copolymer arms. Depending on the pH of the medium, two different self-assemblies were observed. At a low pH (pH 2), core-shell unimolecular micelles, with a hydrophobic PS core and P2VP, PAA segments in the shell, as well as multicore large compound micelles were formed. At pH 8.5, the star was transformed from a bis-hydrophilic into a bis-hydrophobic state, leading to a network-like intermicellar assembly. This star terpolymer was capable of dispersing MWCNTs, through non-covalent interactions, thus leading to stable MWCNT-star nanohybrids in water. More importantly, the resulted MWCNT-star nanohybrids adopted the "smart" pH responsive properties of the physisorbed stars, i.e. the nanohybrids can be positively or negatively charged at low and high pH respectively, while at an intermediate pH window, phase separation occurs due to neutralization of the oppositely charged segments. This journal is © The Royal Society of Chemistry 2013.

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