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Nanofiltration (NF) membranes can retain micropollutants (MPs) to a large extent, even though adsorption into the membrane and gradual permeation result in breakthrough and incomplete removal. The permeation of MPs is investigated by examining the energy barriers (determined using the Arrhenius concept) for adsorption, intrapore diffusion, and permeation encountered by four different steroid hormones in tight and loose NF membranes. Results show that the energy barriers for steroid hormone transport in tight membrane are entropically dominated and underestimated because of the high steric exclusion at the pore entrance. In contrast, the loose NF membrane enables steroid hormones partitioning at the pore entrance, with a permeation energy barrier (from feed toward the permeate side) ranging between 96 and 116 kJ/mol. The contribution of adsorption and intrapore diffusion to the energy barrier for steroid hormone permeation reveals a significant role of intrapore diffusive transport on the obtained permeation energy barrier. Overall, the breakthrough phenomenon observed during the NF of MPs is facilitated by the low energy barrier for adsorption. Experimental evidence of such principles is relevant for understanding mechanisms and ultimately improving the selectivity of NF.

We report on the effect of graphene (G) incorporation in TiO2 photoanodes (PAs) for improving their dye adsorption capacity, which in turn impacts the overall photoconversion efficiency of dye-sensitized solar cells (DSSCs). By varying the graphene content of TiO2 PAs (over the 0.05–1 wt.% range), the power conversion efficiency (PCE) of the DSSCs was found to increase significantly from 3.0% for standard TiO2 to a maximum value of 8.2% for PAs containing 0.1 wt. % of graphene. This corresponds to a PCE improvement of ∼173% in comparison with standard DSSCs made with TiO2 alone (without graphene). On the other hand, by performing thermogravimetric analyses to quantify the dye adsorption capacity of the TiO2–G PAs, we were able to establish, for the first time, a direct correlation between the PCE of the DSSCs and the dye uptake of their G–TiO2-based PAs. Our results demonstrate that by coupling the optimal PA (with the optimal graphene content of 0.1 wt.% and optimal sensitization with a solution of 4 mM of N719) with Co–Ni nanoparticles decorated multi-walled carbon nanotubes (MWCNTs) based counter electrodes, we were able to achieve DSSCs exhibiting a PCE as high as 9.8%. This performance is quite impressive particularly considering that no platinum was used in the counter electrode.

The adhesion, proliferation, and migration of cells over nanomaterials is regulated by a cascade of biochemical signals that originate at the interface of a cell with a substrate and propagate through the cytoplasm to the nucleus. The topography of the substrate plays a major role in this process. Cell adhesion molecules (CAMs) have a characteristic size of some nanometers and a range of action of some tens of nanometers. Controlling details of a surface at the nanoscale—the same dimensional over which CAMs operate—offers ways to govern the behavior of cells and create organoids or tissues with heretofore unattainable precision. Here, using electrochemical procedures, we generated mesoporous silicon surfaces with different values of pore size (PS ≈ 11 nm and PS ≈ 21 nm), roughness (Ra ≈ 7 nm and Ra ≈ 13 nm), and fractal dimension (Df ≈ 2.48 and Df ≈ 2.15). Using electroless deposition, we deposited over these substrates thin layers of gold nanoparticles. Resulting devices feature (i) nanoscale details for the stimulation and control of cell assembly, (ii) arrays of pores for drug loading/release, (iii) layers of nanostructured gold for the enhancement of the electromagnetic signal in Raman spectroscopy (SERS). We then used these devices as cell culturing substrates. Upon loading with the anti-tumor drug PtCl (O,O′-acac)(DMSO) we examined the rate of adhesion and growth of breast cancer MCF-7 cells under the coincidental effects of surface geometry and drug release. Using confocal imaging and SERS spectroscopy we determined the relative importance of nano-topography and delivery of therapeutics on cell growth—and how an unbalance between these competing agents can accelerate the development of tumor cells.

A breakthrough curve in nanofiltration (NF) is observed when micropollutants adsorption and subsequent diffusion through the membrane occur at environmentally relevant low concentrations. The role of hydrodynamics and operative conditions in characterizing the curve shape is undefined. In this study, the impact of mass transport and residence time on the breakthrough curve shape of loose NF270 and tight NF90 is determined. Cross flow and stirred cell filtration systems are used to evaluate the breakthrough curve shape at different ranges of external mass transfer (km) and pressure (hence residence time). The concentration on the membrane surface plays a major role in controlling the breakthrough curve S-shape of NF membranes compared to the residence time in the active layer. The increase of concentration polarization (by increasing the flux or decreasing km) results in an increase of breakthrough curve steepness, which is particularly evident for the loose NF270. Indeed, convection and adsorption enhance the E2 transport through NF270, resulting in a breakthrough curve shape dependent on operational parameters. These novel findings are important for the evaluation of the breakthrough curve of new NF membrane materials through the appropriate selection of operative and hydrodynamic conditions.

Background: Estrogens and their synthetic analogues are widely used as pharmaceuticals. Upon oral administration these drugs are eventually excreted via urine. The persistence of these pharmaceuticals and inefficient removal by water treatment lead to accumulation in surface water and effluents with negative effects for aquatic life and human health. Methods: In this study, the uptake of estradiol by a combined magnetic ion exchange resin - ultrafiltration process (MIEX-UF) was investigated. This is a relatively common process used in drinking water treatment for the removal of natural organic matter. However, uptake of micropollutants, such as steroidal pharmaceuticals, may occur as a side effect of water treatment due to the high affinity for polymeric materials. To elucidate the mechanism governing estradiol partitioning between water, resin and membrane, the influence of different parameters, such as pH, humic acid concentration and membrane molecular-weight-cut-off (MWCO) was studied. Results: Humic acid concentration and pH affected estradiol uptake most. At pH 11 the most significant increase of estradiol uptake was observed for MIEX-UF process (30 ng/g corresponding to 80%) compared with individual UF (17 ng/g corresponding to 12%). The presence of humic acid slightly reduced estradiol uptake at pH 11 (about 55%) due to competition for the ion exchange binding sites. Conclusion: Results demonstrated that the uptake of estradiol, which is amongst the most potent EDCs detected in surface water, in the MIEX-UF process can reach significant quantities (30 ng/g of resin) leading to uncontrolled accumulation of this micropollutant during drinking water treatment. This study gives a novel contribution in the understanding the mechanism of the unanticipated accumulation of pharmaceuticals, such as estradiol, in the drinking water treatment process.

A long-standing goal of neuroscience is a theory that explains the formation of the minicolumns in the cerebral cortex. Minicolumns are the elementary computational units of the mature neocortex. Here, we use zinc oxide nanowires with controlled topography as substrates for neural-cell growth. We observe that neuronal cells form networks where the networks characteristics exhibit a high sensitivity to the topography of the nanowires. For certain values of nanowires density and fractal dimension, neuronal networks express small world attributes, with enhanced information flows. We observe that neurons in these networks congregate in superclusters of approximately 200 neurons. We demonstrate that this number is not coincidental: the maximum number of cells in a supercluster is limited by the competition between the binding energy between cells, adhesion to the substrate, and the kinetic energy of the system. Since cortical minicolumns have similar size, similar anatomical and topological characteristics of neuronal superclusters on nanowires surfaces, we conjecture that the formation of cortical minicolumns is likewise guided by the interplay between energy minimization, information optimization and topology. For the first time, we provide a clear account of the mechanisms of formation of the minicolumns in the brain.

In this paper, we report on the realization of photoanodes for dye sensitized solar cells based on composites of carbon nanotubes and titanium dioxide nanoparticles. Our results show the best photovoltaics performance for carbon nanotubes weight percentages between 0.2% and 0.4%. Photoanodes realized in three-layer configuration, TiO2/carbon nanotube/TiO2, show a cell efficiency of 10.5% and a fill factor of 70%, values 2.4 times greater with respect to that of classical TiO2 anode. The presence of carbon nanotubes enhances the charge transport, strongly reducing the electron/hole recombination in the anode bulk, while the double layer of TiO2 increases the dye adsorption limiting the reduction caused by the presence of carbon nanotubes.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Magnetic ion exchange resins (MIEX) were combined with nanofiltration (NF) in one single process to mitigate fouling by humic acids (HA). MIEX effectiveness in controlling NF fouling was investigated under different feed chemical conditions and employing two types of NF membranes (NF270, NF90). Fouling layer thickness was determined using novel helium ion microscopy, which allowed analysis of the membrane surface without sample alteration. Without MIEX, significant flux reduction (53–78%) due to irreversible organic fouling was observed for NF90, while fouling of NF270 was mostly reversible (15–23% irreversible flux reduction). This difference stems partially from the different ability of the two membranes to reject calcium, which affects the deposition of HA. Fouling was generally higher at alkaline pH due to calcite precipitation and formation of calcium-HA complexes. In the combined MIEX-NF process, fouling was reduced significantly. With NF90, irreversible flux reduction was half compared to the experiments run without resins, especially at neutral and alkaline pH (6−10). This was attributed to favorable HA-MIEX electrostatic interaction, which minimized the Ca-HA complexation and the availability of foulants for membrane deposition. Results demonstrated the effectiveness of MIEX to minimize fouling under different feed chemical conditions. This is of great importance considering the wide variability of real water chemistries in NF sources for drinking water production.

Co-encapsulation of drugs in the same carrier, as well as the development of microencapsulation processes for biomolecules using mild operating conditions, and the production of particles with tailored size and uniformity are major challenges for encapsulation technologies. In the present work, a suitable method consisting of the combination of membrane emulsification with solvent diffusion is reported for the production of multi-core matrix particles with tailored size and potential application in multi-therapies. In the emulsification step, the production of a W/O/W emulsion was carried out using a batch Dispersion Cell for formulation testing and subsequently a continuous azimuthally oscillating membrane emulsification system for the scaling-up of the process to higher capacities. In both cases precise and gentle control of droplet size and uniformity of the W/O/W emulsion was achieved, preserving the encapsulation of the drug model within the droplet. Multi-core matrix particles were produced in a post emulsification step using solvent diffusion. The compartmentalized structure of the multicore-matrix particle combined with the different chemical properties of polycaprolactone (matrix material) and fish gelatin (core material) was tested for the simultaneous encapsulation of hydrophilic (copper ions) and hydrophobic (α-tocopherol) test components. The best operating conditions for the solidification of the particles to achieve the highest encapsulation efficiency of copper ions and α-tocopherol of 99 (± 4)% and 93(± 6)% respectively were found. The multi-core matrix particle produced in this work demonstrates good potential as a co-loaded delivery system.

In this work, we illustrated a method for controlled growth of ZnSe/ZnS core/shell semiconductor and their insertion in a TiO 2 anatase bulk. Core/shell quantum dots were grown by Laser Ablation in Solution followed by heating and sonication phases. Shape and dimensions of nanoparticles were controlled by measurements of optical absorption during laser irradiation. The obtained quantum dots, with a ZnS core and a ZnSe shell and radius dimensions of about 12 nm, were spray-dried in film of anatase grains and characterized as photoanode for application on Graetzel cells. The efficiency of our hybrid photoanode is about 25% higher than classic organic dye/anatase.

In this work, we introduce a new method for the consolidation of ceramic artifacts using SiO2 and TiO2 nanoparticles (NPs). We study the influence of NPs in the restoration process based on luminescence diagnostics and dating techniques. The nanoparticles were grown by laser ablation in solution and their shape and dimensions were monitored by optical absorption and AFM morphology studies. The colloidal solutions are mainly made of spherical nanoparticles with dimensions of about 10 and 15 nm following a LogNorm distribution with a standard deviation less than 1 nm. The colloidal solution was then deposed on pottery surfaces to obtain a transparent film with thickness of about 1 μm. All chemical and morphological analysis indicate that the NPs consolidate the artifact penetrating in the deeper surface layer and forming a transparent and hydrophobic film on the surface. The adsorption process is a typical physisorption mechanism without formation of chemical bonds between the NPs and the constitutive elements of ceramic and without introduction of external impurities, which can damage the materials. Finally, our results indicate a strong influence of NPs on the luminescence emission by the artifacts and then in the thermoluminescence dating process for restored ceramics.

In this work, we present the analysis of adsorption properties of CO2 on Ag nanoparticle/carbon nanotube nanocomposites compared to those of N2 and O2. We observe for all gases an identical kinetic behavior, indicating that the nonwetting properties of CO2 on a carbon surface do not influence the gas adsorption. We perform the analysis in conditions of low pressure and temperature to better observe the physical properties of the system. We observe a first kinetic order for all gases, indicating the absence of gas–gas interactions on the composite surface. The desorption curves for all gases present several desorption temperatures, indicating the presence of different kinds of adsorption sites.

We report here on the use of pulsed KrF-laser deposition technique (PLD) for the decoration of Multi-wall carbon nanotubes (MWCNTs) by Co–Ni nanoparticles (NPs) to form highly efficient counter electrodes (CEs) for use in Dye-sensitized solar cells (DSSC). By varying the number of laser ablation pulses (N LP = 500–60,000) of the KrF laser, we were able to control the average size of the Co–Ni NPs and the surface coverage of the MWCNTs by the nanoparticles. The PLD-based decoration of MWCNTs by Co–Ni NPs is shown to form novel counter electrodes, which significantly enhance the power conversion efficiency (PCE) of the DSSCs. Indeed, the DSSCs based on the PLD-decorated Co–Ni counter electrodes (obtained at the optimal N LP = 40,000) are shown to exhibit a PCE value as high as 6.68%, with high short circuit current (J sc = 14.68 mA/cm2) and open circuit voltage (V oc = 0.63 V). This represents a PCE improvement of ~190% in comparison to the DSSCs with pristine MWCNTs (PCE = 2.3%) and ~7.4% PCE increase than that of the conventional DSSC made with a sputtered Platinum-based counter electrode. By systematically investigating the local nanostructure of the Co–Ni decorated CEs, we found that the Co–Ni NPs layer exhibits a porous cauliflower-like morphology, of which surface roughness (RMS) is N LP dependent. Interestingly, both PCE and roughness of the Co–Ni NPs layer are found to exhibit the same N LP dependence, with a maximum located around the optimal N LP value of 40,000. This enabled us to establish, for the first time, a linear correlation between the achieved PCE of DSSCs and the local roughness of their CEs decorated by Co–Ni NPs. Such a correlation highlights the importance of maximizing the surface area of the Co–Ni coated MWCNTs on the CEs to enhance the PCE of the DSSCs. Finally, Ultra-violet Photoelectron Spectroscopy (UPS) measurements revealed a significant decrease in the local work function (Φ) of Co–Ni NPs decorated MWCNTs based CEs (at N LP = 40,000, Φ = 3.9 eV) with respect to that of either pristine MWCNTs (Φ = 4.8 eV) or sputtered-Pt (Φ = 4.3 eV) counter-electrodes. This Φ lowering of the Co–Ni/MWCNTs based CEs is an additional advantage to enhance the catalytic reaction of the redox couple of the electrolyte solution, and improve thereby the PCE of the DSSCs.

In the pharmaceutical field, manufacturing processes which are able to make products with tailored size at suitable shear stress conditions and high productivity are important requirements for their industrial application. Cross-flow and premix membrane emulsification are the membrane-based processes generally used for particles preparation at large scale, however some disadvantages still limit their applicability for the production of fragile products. In this work, we investigated, for the first time, the preparation of micro and nano polymeric particles in a size range between 2.35 (±0.14) μm and 210 (±10) nm by using pulsed back-and-forward membrane emulsification for the application in pharmaceutical field. The suitability of the method to produce tailored particles by applying mild shear conditions has been demonstrated. The optimized fluid-dynamic conditions studied allowed the production of particles with target size by selecting the appropriate pore size of the membrane (1 μm and 0.1 μm). The uniformity of the particles could be obtained with an axial velocity of 0.5 ms−1 (corresponding to a shear stress of 4.1 Pa) that is 9 times lower than the maximum cross flow velocity reported in literature (4.5 ms−1).

In this work, we present the growth and optical characterization of carbon nanotube/TiO2 anatase nanocomposites. The composites are obtained by doping a bulk of anatase nanometric grains with different weight percentages of carbon nanotube (from 0.1% to 50%). We observe that only for tube concentrations between 0.1% and 2%, the growth process shows the formation of a matrix where carbon nanotubes are uniformed and dispersed in a bulk of TiO2 grains. Moreover, the X-ray photoelectron spectroscopy and surface morphology analysis (conducted from AFM images) indicated that the CNT absorption is a simple physisorption without chemical bonds formations between tube and dioxide. Finally, absorption in all the visible range has the increase of about 60% at very low concentration (2%) of carbon nanotubes.

Environmental contextContamination of surface water by micropollutants is a major environmental concern because of their high persistence and toxicity. Micropollutants are only partially removed in nanofiltration water treatment systems, encouraging the investigation of more complex systems involving partitioning with membrane materials, organic matter and ion exchange resins. This study elucidates the micropollutant partitioning mechanisms in this complex water treatment system. AbstractThe accumulation of micropollutants, such as steroid hormones, in magnetic ion exchange resin-nanofiltration (MIEX-NF) poses a risk to the environmental contamination of surface water where the treated water is discharged. In this study, the partitioning of the steroid hormone estradiol (E2) with humic acid (HA), MIEX and the membrane is investigated at different feed water conditions (e.g. pH and presence of calcium). The transport and adsorption of E2 in NF is not affected significantly by the E2-HA interaction. Indeed, E2 partitions with HA between 8% and 25% at different pH. This is attributed to the presence of calcium ions, which reduces the number of HA molecules available to interact with E2 molecules. The calcium interference is evident especially at pH>10, where calcite and HA precipitate to result in irreversible membrane fouling. In the hybrid MIEX-NF process, the E2-MIEX interaction occurs at all pH conditions. Approximately 40% of the E2 total mass partitions with MIEX. This is significantly higher than E2 accumulation in NF. Since the partitioning is at least partially reversible, this poses a risk for accidental E2 release into the process streams.

Membrane emulsification is a promising technology for the production of micro nano particles, which is able to compete with the conventional mechanical emulsification processes. The production of emulsions with narrow droplet size distribution at dispersed phase fluxes (productivity) sufficiently high to make the process suitable for industrial application is still a considerable challenge. The interfacial tension between the dispersed phase and the membrane pore wall is a crucial parameter to maintain droplets shape while enhancing productivity. In the present paper, a membrane thickness with asymmetric properties in terms of wettability between external and internal sides has been tested in the preparation of W/O emulsions. The membrane surface wettability modification was obtained by adsorption of hydrophobic macromolecules on the lumen side of hydrophilic membrane. Lipase was used as a model macromolecule. W/O emulsion droplets with smaller droplets size have been produced with lipase-loaded membrane compared with the unmodified hydrophilic membrane. High dispersed phase flux of 30 L h(-1) m(-2) was also obtained with a significant increase of process productivity compared to the use of hydrophobic membranes. These results show that membrane-protein interaction can be used to functionalize opportunely the membrane for membrane emulsification application reducing emulsification time and increasing dispersed phase flux without modifying the control on droplets properties in terms of size and size distribution. (C) 2014 Elsevier BY. All rights reserved.

Over the last decade, the use of polycaprolactone has attracted much interest in drug delivery compared to biodegradable polyesters derived from lactic and glycolic acids. The methodologies commonly used for the preparation of polycaprolactone microparticles are associated with many problems regarding the control of particle size and size distribution and particles morphology. Membrane emulsification/solvent diffusion processes offer great potentials in manufacturing particles. In this work, polycaprolactone microparticles with mean diameter of 20. ?m, spherical shape and smooth surface have been successfully produced using the emulsification/solvent diffusion method. The fluid-dynamic and chemical parameters have been optimized to produce uniform particles with a span value of 0.5. The effect of process parameters controlling the solvent diffusion on the shape and surface morphology has also been investigated. The use of microporous membranes allowed the simultaneous particle size and size distribution control during the emulsification step. Also, the solvent diffusion permitted easy control of the size and morphology of particles during the solidification of polymer within the droplets. © 2014 Elsevier B.V.

In this work, we present the realization of four carbon-based counter electrodes for dye-sensitized solar cells. The photovoltaic behaviours of counter electrodes realized with graphene, multiwalled carbon nanotubes, and nanocomposites of multiwalled carbon nanotubes and metal nanoparticles are compared with those of classical electrodes (amorphous carbon and platinum). Our results show an increase of about 50% in PCE for graphene and Ag/carbon nanotube electrodes with respect to amorphous carbon and of 25% in comparison to platinum. An improvement in cell stability is also observed; in fact, the PCE of all carbon-based cells assumes a constant value during a period of one month while that with the Pt electrode decreases by 50% in one week.

In this work, we propose using the pulsed laser ablation technique in solution as a 'chemical-free' method for forming biatomic or multiatomic semiconductor quantum dots. In particular, we present the results of the formation and characterization of ZnS nanoparticles by laser ablation in solution as a case study for all semiconductors of the III and IV groups. We obtain results comparable to those obtained by chemical methods without the use of surfactants and without changing the crystallinity of the precursor target. Colloidal solutions of nanoparticles with different dimensions were obtained by varying the irradiation time during laser ablation. A study of the morphology and changes in the band edge indicates the formation of ZnS quantum dots with dimensions