28 research outputs found
A nonspecific synergistic effect of biogenic silver nanoparticles and biosurfactant towards environmental bacteria and fungi
The present study focused on the evaluation of a nonspecific synergistic effect of biogenic silver nanoparticles (AgNPs) in combination with biosurfactants against environmental bacteria and fungi. The AgNPs were synthesized in the culture supernatants of the biosurfactant producer Bacillus subtilis grown in brewery effluent, molasses or Luria-Bertani media. Antibacterial activities were tested against Gram-positive and Gram-negative bacteria, while the antifungal activity was tested against phytopathogens. The interactions between biogenic AgNPs and DNA were investigated using a cryo-TEM technique. The presence of biosurfactant significantly increased the stability of biogenic AgNPs and enhanced their antimicrobial activities. The physical properties and antimicrobial activity of biogenic AgNPs were compared with chemically synthesized Ag nanoparticles. Biogenic silver nanoparticles showed a broad spectrum of activity against bacteria and fungi. They were most active against phytopathogenic fungi and Gram-positive bacteria and less active against Gramnegative
bacteria. The nonspecific synergistic effect of biogenic AgNPs and biosurfactant on the phytopathogenic fungi was especially observed. In this report, the new roles of biosurfactants as a biogenic AgNPs stabilizer and enhancer of their antimicrobial properties are presented. Our results revealed that the biologically synthesized AgNPs by the biosurfactantproducing bacterium Bacillus subtilis grown on agro-industrial wastes, such as molasses and brewery effluent, could be used as a promising new nanoagent against microbes
Transferring Circular Economy Solutions across Differentiated Territories: Understanding and Overcoming the Barriers for Knowledge Transfer
“Learning from abroad” is a widely recognised and used means to innovate and improve strategies and policies implemented by regions and cities. However, literature on knowledge transfer and related concepts, such as policy transfer, policy mobility or lesson-drawing, highlights the limitations of this process, especially when it entails the simple transfer of (best) practices from “place A” to “place B”. Such a transfer may lead to suboptimal solutions particularly when the imported practices concern complex phenomena, involving networks of multiple actors and relying on place-specific dynamics. Departing from this critique, the article sheds light on the process of knowledge transfer in the field of circular economy, taking place between the two metropolitan regions of Amsterdam and Naples. This process is guided by an innovative methodology based on a network of (peri-urban) living labs generating eco-innovative solutions for using material waste and wastescapes as a resource in peri-urban areas. Using participant observation in knowledge transfer workshops, stakeholder interviews and surveys, it investigates how the process of co-creation of knowledge in the relational space of the networked living labs takes place thanks to the participation of stakeholders from both regions. This in turn allows for drawing conclusions on what barriers are encountered in such knowledge transfer, what makes solutions transferable across different contexts, and, finally, how the solutions are adapted as they travel from one place to another
Examination of the effect of selected factors on the photovoltaic response of dye-sensitized solar cells
The impact of photoanode preparation on the photovoltaic performance of dye-sensitized solar cells was investigated. The effects of titanium dioxide layer thickness, type of solvent and immersion time used for photoanode fabrication, and addition of coadsorbents and a cosensitizer on photon-to-current conversion efficiency and photovoltaic parameters were studied. Commercially available N719 and dyes prepared in our research group, 5,5′-bis(2-cyano-1-acrylic acid)-2,2′-bithiophene and 2-cyano-3-(2,2′:5′,2″-terthiophen-5-yl)acrylic acid, were applied as sensitizers. The effect of studied factors on UV–vis properties and morphology, that is, the root-mean-square roughness of the photoanode, was examined and correlated with the photovoltaic response of the constructed devices. Additionally, the amount of dye molecules adsorbed to the TiO2 was investigated. It was found that all considered factors significantly impacted photovoltaic parameters. Also, the photoanode stability was tested by measuring photovoltaic parameters after 14 months
Effect of polythiophene content on thermomechanical properties of electroconductive composites
The thermal, mechanical and electrical properties of polymeric composites combined using polythiophene (PT) dopped by FeCl3 and polyamide 6 (PA), in the aspect of conductive constructive elements for organic solar cells, depend on the molecular structure and morphology of materials as well as the method of preparing the species. This study was focused on disclosing the impact of the polythiophene content on properties of electrospun fibers. The elements for investigation were prepared using electrospinning applying two substrates. The study revealed the impact of the substrate on the conductive properties of composites. In this study composites exhibited good thermal stability, with T5 values in the range of 230–268 °C that increased with increasing PT content. The prepared composites exhibited comparable PA Tg values, which indicates their suitability for processing. Instrumental analysis of polymers and composites was carried out using Fourier Transform Infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM)
Effect of polyaniline content and protonating dopants on electroconductive composites
Elastic constructive elements prepared by electrospinning using polyacrylonitrile/polyaniline (PAN/PANI) electroconductive composites were prepared and investigated in terms of their thermal and mechanical properties. This study was focused on the impact of the type of counterion of polyaniline and the PANI content in composites on the thermal, conductive and morphological properties of electrospun fibers. In this study, composites obtained from PANI doped with sulfuric acid showed the highest conductivity, and composites obtained from PANI doped with hydrochloric acid showed the highest thermal stability. All obtained composites exhibited good thermal stability, with T5 values in the range of 230–268 °C that increased with increasing PANI content. The prepared composites exhibited comparable PAN Tg values, which indicates their suitability for processing. Instrumental analysis of polymers and composites was carried out using UV–visible spectroscopy, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis and scanning electron microscopy
The influence of paclitaxel on hydrolytic degradation in matrices obtained from aliphatic polyesters and polyester carbonates
Biodegradable polymers have become common materials used in pharmacy and medicine due to their
properties such as mechanical strength, biocompatibility and non-toxic degradation products. Different compositions of copolymers and also their chain microstructure may have an effect on matrices degradation and thus on the drug release profile. In our study, we aimed at the influence of paclitaxel content on hydrolytic degradation process of terpolymeric matrices. Hydrolytic degradation of three kinds of matrices (with 5 or 10% of paclitaxel and drug free matrices) prepared from three types of terpolymers was performed in vitro at 37OC in phosphate buffer solution (PBS, pH 7,4). The 1H and 13C NMR spectra of terpolymers were recorded. Thermal properties were monitored by differential scanning calorimetry (DSC). Molecular weight dispersity (D) and molecular weight were determined using gel permeation chromatography (GPC). The surface morphology was studied by means of the scanning electron microscopy (SEM). The most significant degradation was observed in case of poly(L-lactide-co-glycolide-co-ε-caprolactone) 44:32:24. Weight loss and water uptake were similar in the event of the same type of matrices obtained from the two poly(L-lactide-co-glycolide-co-TMC). Decelerated paclitaxel release in case of matrices with 51:26:23 molar ratio was noticed and it can be connected with higher content of carbonate units. Knowledge of paclitaxel influence on hydrolytic degradation process may contribute to receive valuable information about its release mechanisms from biodegradable terpolymers
Impact of TiO2 nanostructures on dye-sensitized solar cells performance
The effect of TiO2 nanostructures such as nanoparticles, nanowires, nanotubes on photoanode
properties, and dye-sensitized solar cells photovoltaic parameters were studied. The series
of dye-sensitized solar cells based on two dyes, that is, commercially N719 and synthesized 3,70-
bis(2-cyano-1-acrylic acid)-10-ethyl-phenothiazine were tested. Additionally, the devices containing
a mixture of this sensitizer and chenodeoxycholic acid as co-adsorbent were fabricated. The amount
of adsorbed dye molecules to TiO2 was evaluated. The prepared photoanodes with different TiO2
nanostructures were investigated using UV-Vis spectroscopy, optical, atomic force, and scanning
electron microscopes. Photovoltaic response of constructed devices was examined based on currentvoltage
characteristics and electrochemical impedance spectroscopy measurements. It was found
that the highest UV-Vis absorption exhibited the photoanode with nanotubes addition. This indicates
the highest number of sensitizer molecules anchored to the titanium dioxide photoanode, which was
subsequently confirmed by dye-loading tests. The highest power conversion efficiency was (6.97%)
for solar cell containing nanotubes and a mixture of the dyes with a co-adsorbent
New thiophene imines acting as hole transporting materials in photovoltaic devices
ASAP Article - Articles ASAP (as soon as publishable) are posted online and available to view immediately after technical editing, formatting for publication, and author proofing.Five new unsymmetric thiophene imines end-capped with an electron-donating amine (−NH2) group were obtained
using a simple synthetic route, that is, the melt condensation of 2,5-diamino-thiophene-3,4-dicarboxylic acid diethyl ester with
commercially available aldehydes. Their thermal stability and electrochemical and photophysical (absorption (UV−vis) and
photoluminescence (PL)) properties were examined and density functional theory calculations were performed. The imines were
thermally stable above 200 °C. They underwent reduction and oxidation processes and exhibited an energy band gap
electrochemically estimated between 1.81 and 2.44 eV. They absorbed radiation from the UV and visible range to 480 nm and
showed weak light emission. These compounds were investigated as hole transporting materials in solar cells with the structure
FTO/b-TiO2/m-TiO2/perovskite/imine/Au. The highest photoelectric conversion efficiency was observed for compounds with a
morpholine derivative substituent
Remarkable Thermal Conductivity Enhancement in Carbon-Based Ionanofluids: Effect of Nanoparticle Morphology
Transfer of the excellent intrinsic properties of individual carbon nanoparticles
into real-life applications of the corresponding heat transfer fluids remains
challenging. This process requires identification and quantification of the nanoparticle−
liquid interface. Here, for the first time, we have determined geometry and properties of this
interface by applying transmission electron cryomicroscopy (cryo-TEM). We have
systematically investigated how the particle morphology of carbon-based nanomaterials
affected the thermal conductivity, specific isobaric heat capacity, thermal diffusivity, density,
and viscosity of ionanofluids and/or bucky gels, using a wide range of fillers, especially singlewalled
carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs), both
with extreme values of aspect ratio (length to diameter ratio) from 150 to 11 000.
Accordingly, hybrid systems composed of various carbon nanomaterials and ionic liquid,
namely 1-ethyl-3-methylimidazolium thiocyanate [EMIM][SCN], were prepared and
characterized. Most of the analyzed nanodispersions exhibited long-term stability even
without any surfactant. Our study revealed that the thermal conductivity could be remarkably improved to the maximum values of
43.9% and 67.8% for ionanofluid and bucky gel (at 1 wt % loadings of MWCNTs and SWCNTs), respectively, compared to the
pristine ionic liquid. As a result, the model proposed by Murshed and co-workers has been improved for realistic description of the
concentration-dependent thermal conductivity of such hybrid systems. The obtained results undoubtedly indicate the potential of
ionanofluids and bucky gels for energy management
New benzo[h]quinolin-10-ol derivatives as co-sensitizers for DSSCs
New benzo[h]quinolin-10-ol derivatives with one or two 2-cyanoacrylic acid units were
synthesized with a good yield in a one-step condensation reaction. Chemical structure and purity
were confirmed using NMR spectroscopy and elemental analysis, respectively. The investigation of
their thermal, electrochemical and optical properties was carried out based on differential scanning
calorimetry, cyclic voltammetry, electronic absorption and photoluminescence measurements. The
analysis of the optical, electrochemical and properties was supported by density functional theory
studies. The synthesized molecules were applied in dye-sensitized solar cells as sensitizers and cosensitizers
with commercial N719. The thickness and surface morphology of prepared photoanodes
was studied using optical, scanning electron and atomic force microscopes. Due to the utilization of
benzo[h]quinolin-10-ol derivatives as co-sensitizers, the better photovoltaic performance of fabricated
devices compared to a reference cell based on a neat N719 was demonstrated. Additionally, the effect
of co-adsorbent chemical structure (cholic acid, deoxycholic acid and chenodeoxycholic acid) on
DSSC efficiency was explained based on the density functional theory