The never-ending race towards miniaturization of devices induced an intense research in the manufacturing processes of the components of those devices. However, the complexity of the process combined ...with high equipment costs makes the conventional lithographic techniques unfavorable for many researchers. Through years, nanosphere lithography (NSL) attracted growing interest due to its compatibility with wafer-scale processes as well as its potential to manufacture a wide variety of homogeneous one-, two-, or three-dimensional nanostructures. This method combines the advantages of both top-down and bottom-up approaches and is based on a two-step process: (1) the preparation of a colloidal crystal mask (CCM) made of nanospheres and (2) the deposition of the desired material through the mask. The mask is then removed and the layer keeps the ordered patterning of the mask interstices. Many groups have been working to improve the quality of the CCMs. Throughout this review, we compare the major deposition techniques to manufacture the CCMs (focusing on 2D polystyrene nanospheres lattices), with respect to their advantages and drawbacks. In traditional NSL, the pattern is usually limited to triangular structures. However, new strategies have been developed to build up more complex architectures and will also be discussed.
Monolayers of colloidal spheres are used as masks in nanosphere lithography (NSL) for the selective deposition of nanostructured layers. Several methods exist for the formation of self-organized ...particle monolayers, among which spin coating appears to be very promising. However, a spin coating process is defined by several parameters like several ramps, rotation speeds, and durations. All parameters influence the spreading and drying of the droplet containing the particles. Moreover, scientists are confronted with the formation of numerous defects in spin coated layers, limiting well-ordered areas to a few micrometers squared. So far, empiricism has mainly ruled the world of nanoparticle self-organization by spin coating, and much of the literature is experimentally based. Therefore, the development of experimental protocols to control the ordering of particles is a major goal for further progress in NSL. We applied experimental design to spin coating, to evaluate the efficiency of this method to extract and model the relationships between the experimental parameters and the degree of ordering in the particles monolayers. A set of experiments was generated by the MODDE software and applied to the spin coating of latex suspension (diameter 490 nm). We calculated the ordering by a homemade image analysis tool. The results of partial least squares (PLS) modeling show that the proposed mathematical model only fits data from strictly monolayers but is not predictive for new sets of parameters. We submitted the data to principal component analysis (PCA) that was able to explain 91% of the results when based on strictly monolayered samples. PCA shows that the ordering was positively correlated to the ramp time and negatively correlated to the first rotation speed. We obtain large defect-free domains with the best set of parameters tested in this study. This protocol leads to areas of 200 μm2, which has never been reported so far.
Plasticized poly(
l-lactide) (PLA) based nanocomposites were prepared by melt blending of the matrix with 20
wt% of poly(ethyleneglycol) 1000 (PEG 1000) and different amounts of montmorillonite, ...organo-modified or not. The intercalation of the polymer chains between the aluminosilicates layers and morphological structure of the filled PLAs were analysed by wide-angle X-ray scattering (WAXS). Thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) were performed to study the thermal behaviour of the prepared composites. At constant filler level, it appears that from all the clays studied, the montmorillonite organo-modified by bis-(2-hydroxyethyl)methyl (hydrogenated tallowalkyl) ammonium cations brings the greater effect in terms of thermal stability. Increasing the amount of clay allows to delay the onset of thermal degradation of the plasticized polymer matrix. It was also pointed out, by WAXS and DSC analyses, that it exists a real competition between PEG 1000 and PLA for the intercalation into the interlayer spacing of the clay.
This in vitro study investigated the metabolism of human osteoarthritic (OA) chondrocytes encapsulated in a spherical matrix enriched of chitosan. Human OA chondrocytes were encapsulated and cultured ...for 28 days either in chitosan-alginate beads or in alginate beads. The beads were formed by slowly passing dropwise either the chitosan 0.6%-alginate 1.2% or the alginate 1.2% solution through a syringe into a 102 mM CaCl2 solution. Beads were analyzed histologically after 28 days. Interleukin (IL)-6 and -8, prostaglandin (PG) E2, matrix metalloproteinases (MMPs), hyaluronan and aggrecan were quantified directly in the culture supernatant by specific ELISA and nitric oxide (NO) by using a colorimetric method based on the Griess reaction. Hematoxylin and eosin staining showed that chitosan was homogeneously distributed through the matrix and was in direct contact with chondrocytes. The production of IL-6, IL-8 and MMP-3 by chondrocytes significantly decreased in chitosan-alginate beads compared to alginate beads. PGE2 and NO decreased also significantly but only during the first three days of culture. Hyaluronan and aggrecan production tended to increase in chitosan-alginate beads after 28 days of culture. Chitosan-alginate beads reduced the production of inflammatory and catabolic mediators by OA chondrocytes and tended to stimulate the synthesis of cartilage matrix components. These particular effects indicate that chitosan-alginate beads are an interesting scaffold for chondrocytes encapsulation before transplantation to repair cartilage defects.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Light management is an important area of photovoltaic research, but little is known about it in perovskite solar cells. The present work numerically studies the positive effect of structuring the ...photo-active layer of perovskite material. This structuration consists of a hybrid absorbing layer made of an uniform part and an opal-like part. A genetic algorithm approach allows us to determine the optimal combination among more than 1.4 × 10 9 potential combinations. The optimal combination provides an internal quantum efficiency of 98.1%, nearly 2% higher than for an equivalent unstructured photo-active layer. The robustness of the optimum against potential experimental deviations, as well as the angular dependency of the proposed structure, are examined in the present study.
•I2-free polysiloxanes ionic conductors were used as electrolytes in TiO2 nanotubes based flexible electrodes.•I2-free electrolyte improved visible light absorption and reduces charge recombination ...in fabricated DSSCs.•Impedance spectroscopy and Voc decay measurements confirmed superior electron life time for DSSCs based on I2-free electrolytes.•I2-free electrolytes showed improved efficiency and stability as compared to the I2-based electrolyte.
For practical applications, flexible solid-state dye-sensitized solar cells (ss-DSSCs) with high photovoltaic performance and stability are paramount. A novel iodine (I2)-free polysiloxane based highly conductive poly(ionic liquid), which acts as the lone charge transfer intermediate, is used for the first time as an electrolyte in flexible 1D TiO2 nanotube photoanodes (TiO2 NT) based ss-DSSCs. The I2-free polymer electrolyte plasticized with ethylene carbonate (EC) leads to a higher power conversion efficiency in DSSCs involving TiO2 NTs than the I2-based polymer electrolyte, mainly due to improved Voc and Jsc. Apart from overcoming the visible light absorption loss, this I2-free polymer electrolyte also reduces the charge recombination and thus leads to higher electron lifetime in DSSCs. The I2-free DSSCs also displayed long-term stability measured under ambient and accelerated stability testing. The improvement is also due to the effective pore infiltration into the large pores of TiO2 NT structure in ss-DSSCs.
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With the purpose of achieving highly stable and efficient polymer electrolytes for dye-sensitized solar cell (DSSC) applications, a series of new poly(ionic liquids) (PILs), namely, ...poly(1-N-methylimidazolium-pentylpolydimethylsiloxane)iodide, with different ratios of pentylimidazolium iodide moieties, have been studied and employed to prepare solid-state electrolytes for DSSCs. PILs were further mixed with two types of ionic liquids (ILs), 1-methyl-3-propylimidazolium iodide (MPII) and 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (MPITFSI), and a plasticizer, such as ethylene carbonate (EC), to lower their viscosity and to increase the diffusion coefficient and ionic conductivity. The assembled devices prepared, using the quasi-solid-state electrolytes showed, light-to-electricity conversion efficiencies up to 6% for an active area of 0.2064 cm2. After 250 days, PIL-based cells retained 84% of their initial efficiency. These new findings encourage worldwide practical applications of DSSCs.
The biomineralization of otoliths results mainly from the release of soluble Ca
2+, which is in turn precipitated as CaCO
3 crystals. In some Carapidae, sagittae sections have been shown to reveal a ...three-dimensional asymmetry with a nucleus close to the sulcal side, an unusual position. This study seeks to understand otolith formation in
Carapus boraborensis. The unusual shape of the otolith is partly explained by the distribution of the epithelium cells, and particularly the sensory epithelium. Experimental evidence shows for the first time that aragonite growth takes place along the
c-axis. These aragonite needles present two different habits. On the sulcal side is found the acicular form resulting from rapid growth during a short period of time. On the anti-sulcal side, the prismatic form seen there is due to a slower growth speed over longer periods. The otolith surface was observed each hour during a period of 24
h in fishes reared in similar conditions. This allowed for the first time the direct observation on the otolith surface of the deposition of the two layers (L-zone and D-zone). In
C. boraborensis, the organic-rich layer (D-zone) develops during the day, whereas the CaCO
3 layer (L-zone) seems to be deposited during the night.
Concurrently to research conducted on ordinary Portland cement (PC), new types of binders were developed during the last decades. These are formed by alkali-activation of metakaolin or ...ground-granulated blast furnace slag (GGBFS) and are named, respectively, geopolymers (GP) or alkali-activated slag (AAS). Four different cementitious materials were synthesised: PC, AAS, GP, and a mix GP-AAS and fully compared about their compositions and (micro)-structures.
X-ray diffraction has revealed the presence of semi-crystalline C
S
H gel binding phase in PC while AAS, GP and GP-AAS are nearly amorphous. Progressive structural changes have been observed between the different samples by means of infrared spectroscopy,
29Si and
27Al magic-angle-spinning nuclear magnetic resonance spectroscopy: there is a polymerisation extent of the (alumino)-silicate framework from PC SiQ
1 and SiQ
2 units to AAS SiQ
2 and SiQ
2(1Al) units and finally to GP SiQ
4(2Al) and SiQ
4(3Al) units. Scanning electron microscopy has shown that GP is a homogeneous matrix while the other materials are composites containing GGBFS grains surrounded by a binding matrix. Energy dispersive X-ray EDX analyses (line scans) have shown the absence of formation of any specific phase at the matrix-grains interfaces.
Mesoporous tungsten oxide films have been reported via numerous processing routes namely dip-coating, spin-coating, electrodeposition etc. and different porous architectures have been emerged. ...However, the templating strategy becomes more challenging when associated with the more industrially compelling spraying methods. The confined environement of the droplets, the temperature gradient during the droplets trajectory along with the relatively high substrate temperature might severely alter the delicate kinetics of the mesophase process.
In this publication, we attest that templating can be effectively combined with the Ultrasonic Spray Pyrolysis method by a careful control of the deposition conditions. The emerging films are structurally characterized in the presence and absence of a surfactant over a temperature range (100 °C-390 °C) in order to determine the optimal deposition temperature. Smooth, uniform films are obtained at lower deposition temperatures (100 °C and 190 °C) and only in the presence of a surfactant. Therefore, surfactants are essentially acting as both wetting and templating agents at the same time. Finally, we emphasize on the role of porosity on enhancing the electrochromic properties of the films. Noticeably improved optical contrast (59 vs. 4%), coloration efficiency (40 vs. 6 cm2.C−1) and capacity (20 vs. 5 mC cm−2) is observed for the porous films compared to their dense counterparts.
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•Ultrasonic Spray pyrolysis as a method to deposit mesoporous tungsten oxide films.•Templating can be successfully combined with the Ultrasonic Spray pyrolysis method.•Porous films exhibit better electrochromic properties than dense films.
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