In an effort to obtain porous scaffolds with improved mechanical properties and biocompatibility, the current study discusses nanocomposite materials based on poly(propylene fumarate)/N-vinyl pyrrolidone(PPF/NVP) networks reinforced with polymer-modified graphene oxide (GO@PPF). The GO@PPF nanofiller was synthesized through a facile and convenient surface esterification reaction, and the successful functionalization was demonstrated by complementary techniques such as FT-IR, XPS, TGA and TEM. The PPF/NVP/GO@PPF porous scaffolds obtained using NaCl as a porogen were further characterized in terms of morphology, mechanical properties, sol fraction, and in vitro degradability. SEM and nanoCT examinations of NaCl-leached samples revealed networks of interconnected pores, fairly uniform in size and shape. We show that the incorporation of GO@PPF in the polymer matrix leads to a significant enhancement in the mechanical properties, which we attribute to the formation of denser and more homogenous networks, as suggested by a decreased sol fraction for the scaffolds containing a higher amount of GO@PPF. Moreover, the surface of mineralized PPF/NVP/GO@PPG scaffolds is uniformly covered in hydroxyapatite-like crystals having a morphology and Ca/P ratio similar to bone tissue. Furthermore, the preliminary biocompatibility assessment revealed a good interaction between PPF/PVP/GO@PPF scaffolds and murine pre-osteoblasts in terms of cell viability and proliferation.

Photo and thermal cis -> trans isomerization kinetics were investigated for a class of chloro-azomonoethers. We found that in the particular case of this class the photo induced isomerization overlaps with the thermal isomerization. For thermal isomerization (dark conditions) we have remarked multiple mechanisms that overlap revelated by multiexponential behavior. Our experimental constant rates for the photo and thermal cis -> trans isomerization was in the same range with values reported in literature. Activation energies for major thermal mechanism shows a dependence with molecule charge distribution.

Nucleic-acid aptamers consisting in single-stranded DNA oligonucleotides emerged as very promising biorecognition elements for electrochemical biosensors applied in various fields such as medicine, environmental, and food safety. Despite their outstanding features, such as high-binding affinity for a broad range of targets, high stability, low cost and ease of modification, numerous challenges had to be overcome from the aptamer selection process on the design of functioning biosensing devices. Moreover, in the case of small molecules such as metabolites, toxins, drugs, etc., obtaining efficient binding aptamer sequences proved a challenging task given their small molecular surface and limited interactions between their functional groups and aptamer sequences. Thus, establishing consistent evaluation standards for aptamer affinity is crucial for the success of these aptamers in biosensing applications. In this context, this article will give an overview on the thermodynamic and structural aspects of the aptamer-target interaction, its specificity and selectivity, and will also highlight the current methods employed for determining the aptamer-binding affinity and the structural characterization of the aptamer-target complex. The critical aspects regarding the generation of aptamer-modified electrodes suitable for electrochemical sensing, such as appropriate bioreceptor immobilization strategy and experimental conditions which facilitate a convenient anchoring and stability of the aptamer, are also discussed. The review also summarizes some effective small molecule aptasensing platforms from the recent literature.

We report an extension of experimental technique (version of the Chang method) for the measurement of the optical birefringence of [4-(4-chlorobenzyloxy)-3-methylpheny](p-tolyl)diazene dye in NLC phase. The azo dye shows birefringence only for cooling cycle, due to the increasing of molecular order by hydrogen bond associations. We create an extension from three-band model to four-band model and estimate the dispersion of optical birefringence Delta n(lambda, T) by applying a nonlinear fitting procedure on the rescaled transmittance Tr(lambda, T) We obtained the parameters G(0)(T), G(1)(T), G(2)(T), G(3)(T) involved in the calculation of Delta n(lambda, T). We use interference to accurate measure of temperature dependence of cell thickness D(T). The most important band involved in birefringence was lambda(0)similar to 120 nm, followed by lambda(3)similar to 369 nm, while lambda(1)similar to 258 nm and lambda(2)similar to 340nm bands were not important.

A new thiosemicarbazone ligand was immobilized through a Cu(I)-catalyzed click reaction on the surface of glassy carbon (GC) and electrochemically reduced graphene oxide (GC-ERGO) electrodes grafted with phenylethynyl groups. Using the accumulation at open circuit followed by anodic stripping voltammetry, the modified electrodes showed a significant selectivity and sensibility for Hg(II) ions. A detection limit of 7 nM was achieved with the GC modified electrodes. Remarkably, GC-ERGO modified electrodes showed a significantly improved detection limit (0.8 nM), sensitivity, and linear range, which we attribute to an increased number of surface binding sites and better electron transfer properties. Both GC and GC-ERGO modified electrodes proved their applicability for the analysis of real water samples.

The boundary conditions proposed to discuss the charge exchange taking place in an ionic liquid in contact with non-blocking electrodes are reconsidered in a dynamic situation. Assuming that the variation of the bulk ionic current density depends linearly on the surface value of the ionic current density, the frequency dependence of the phenomenological parameter is determined. The analysis has been performed in the framework where the relaxation times are smaller than a maximum relaxation time τM, and that the response function is independent on the value of the relaxation time. Using simple physical considerations, an expression for the surface conductivity describing the ionic charge exchange at the electrode is obtained. According to our calculations, its frequency dependence is similar to that predicted for the electric conductivity in disordered materials when the mechanism is of the hopping type. From measurements of impedance spectroscopy, by the best fit of the experimental data, the temperature dependence of the hopping time, of the dc surface conductivity, and of the diffusion coefficient are derived. They are in good agreement with the theoretical predictions obtained with the random distribution of surface energy barrier.

We present a study on director reorientation and anchoring breaking time in a pump-probe experiment for dye-doped nematic liquid crystal cells with different pump power and cell thickness. The liquid crystal (LC) used was 4'-n-pentyl-4-cyanobiphenyl (5CB) doped with the dye methyl red (MR). An Ar+ laser beam were used to irradiate the liquid crystal cells with a parallel beam and the twisted nematic structure was investigated with a He-Ne laser beam. We considered LC cells with thickness equal to 8, 12 and 23 mu m filled with 5CB doped with 2% MR. The results had shown that the nematic director is rotated only after a certain time interval, from the moment when the irradiation started. This time is named anchoring breaking time and it decrease as the intensity of the pump power was increased. A linear dependence between the anchoring breaking time and inverse of the pump power was observed for different cell thickness.

The influence of the electrode properties on the electric response of nematic liquid crystal cell limited by ITO surfaces is investigated. From electrochemical impedance spectroscopy measurements (EIS) of the real and imaginary parts of the electric impedance of the cell it is evident that in the DC limit the cell behaves as a pure resistance, since its reactance tends to zero linearly with the frequency of the applied voltage. The spectrum of the real part of the impedance shows the presence of two plateaux, one related to the bulk properties of the cell, and the other to the electrode properties. The experimental data can be interpreted in terms of Poisson–Nernst–Planck model, assuming that the presence of the non-blocking electrodes is described by a boundary condition according to which the conduction current across the electrode due to the charge exchange between ions and electrons is due to the surface electric field, as in Ohmic electrodes, and to the variation of the bulk density of ions just in front to the electrodes, as in the Chang–Jaffe model.

The need to obtain well defined nanometer structures it's a goal difficult to attain. This is even harder when the patterns are needed to be created inside of glass cell containing dye doped nematic liquid crystals (DDNLC). By irradiating cells filled with DDNLC, with a laser beam (476.5 nm), we obtained optically induced patterns, on the inner surface of the glass cell. The surface characterization of the photo-patterns was performed by using atomic force microscopy (AFM). Following the measurements for the regularity of the photo-patterns, optimal parameters that were required to have ripple structures on large areas, with greater heights and lower abnormalities have been obtain.

As far as the efficiency of the dye-sensitized solar cells (DSSC) can be improved by both increasing the rate of the regeneration of the dyes and reducing the rate of recombination, a study of the electric charge transport processes at the interface dye covered photoanode/electrolyte was performed. Using the Electrochemical Impedance Spectroscopy (EIS) technique, the electric response of the DSSC was found to exhibit a significant dependence on the percentage of dye molecules adsorbed on the porous TiO2 electrode. The changes in the impedance spectra related to the dye uncovered suirface of the photoanode have been theoretically analysed.

Evaporation induced self-assembly (EISA) technique was used to fabricate nanostructured titanium dioxide (TiO2) films. Using lyotropic liquid crystals as templates for growing mesoporous thin films on conducting transparent electrodes (TCO) only moderate temperatures are necessary for template removal. Nanoscale analysis of the cross-sectional structure and composition of TiO2 deposited on fluorine doped tin oxide coated glass (FTO) has shown that no tin diffusion is present in the titania film, contrary to what happens when higher temperatures are used with other techniques for growing TiO2 films. The lack of tin contamination within EISA technique prevents an irreversible transition from metastable anatase - generally considered to exhibit superior electrode performance - to the equilibrium rutile phase.

The theoretical dependence on time of the electric charge in a nematic sample is performed, by assuming that both, liquid crystal and alignment layers behave as linear media, according to the Maxwell-Wagner model. Using doped polypyrrole as orienting layer, under an applied electric field, the injection of ions from the alignment layer into the nematic bulk has to be taken into account in order to understand the accumulated electric charge experimentally found from the current-voltage characteristics.

Six new 1,4-disubstituted thiosemicarbazides were synthesized and their obtaining reactions were optimized in a 3(2) factorial experiment. The structural features of the analyzed compounds were established by spectral means. The tuberculostatic activity against Mycobacterium Tuberculosis has been tested for different concentrations of the studied thiosemicarbazides in DMSO + phosphate buffer in volumetric ratios 1:4. The highest tuberculostatic activity has been registered for compound IV.

Output performances of Nd-vanadate lasers with simultaneous dual-wavelength emission on the 1.06-μm 4 F 3/2 → 4 I 11/2 transition and the 4 F 3/2 → 4 I 13/2 transition at 1.34 μm are discussed. The design uses a linear resonator for emission at 1.06 μm and an L-type folded resonator for the 1.34-μm wavelength, and the ratio between the power of a single wavelength and the total power is adjusted by the choice of the output mirror transmissions. A continuous-wave (CW) Nd:GdVO4 laser with total output power in the range of 3.9 to 6.8 W and the corresponding ratio of the output power at 1.06 μm to the total output power between 0.26 and 0.97 is realized. It is also shown that in comparison with the pump at 808 nm, the pump directly into the 4 F 3/2 emitting level at 879 nm improves the total output power. Furthermore, a Nd:GdVO4 laser with simultaneous emission at 1.06 and 1.34 μm and that generates also green light at 0.53 μm by intracavity frequency-doubling with LiB3O5 (LBO) nonlinear crystal is demonstrated.

We report on laser-induced ripple structures in dye-doped nematic liquid crystals for different dye concentrations varying between 0.5% and 2% wt. The surface morphology was studied by atomic force microscopy. For dye concentrations smaller than 0.56% the ripple structure was not obtained. The depth of the ripple structure depends on both the laser power and the dye concentration. Using the Berreman formula for periodic structure, the azimuthal anchoring energy was evaluated. An increase of the anchoring energy with the dye concentration and with the pump power was noted.

The electric response of a hydrosolution is investigated. We show that our experimental data can be interpreted by means of the standard drift-diffusion model only if the frequency dependence of the viscosity of the hydrosolution is taken into account. From this result, it follows that measurements of impedance spectroscopy can give information on the non-newtonian character of complex fluids.

We investigate the dielectric properties of hydrogel by means of the impedance spectroscopy technique. Our experimental data relevant to the frequency dependence of the real and imaginary parts of the electrical impedance of the cell indicate that, in the low frequency region (f<20 Hz), the electric response of the cell is dominated by surface effects, weakly dependent on the thickness of the sample. On the contrary, in the high frequency region (f>100 Hz), the electric response of the sample is mainly due to the bulk properties. The observed frequency dependence of the electrical impedance of the cell can be well interpreted by means of the Poisson–Nernst–Planck model taking into account the Ohmic character of the interface electrodes-hydrogel.

In order to estimate electro-optical response times, measurements of the transmitted light intensity through positive uniaxial nematic thin films in planar alignment have been performed. Very fast relaxation times were experimentally found for nematic samples aligned with conductive polymers, namely, polypyrrole doped with 5 types of anions having different molecular sizes and geometries. Using undoped polypyrrole alignment layers, slower electro-optical responses were obtained. Given that the improvement in the relaxation times is induced by the presence of the anions in the polypyrrole films, the increasing of the total restoring torque of the nematic molecules to the confining surfaces—responsible for the short relaxation times—is related to the charges accumulated at the nematic-conductive polymer interface.

The photoalignment effect induced by an Ar+ linearly polarized laser beam on a dye-doped nematic liquid crystal in a pump-probe experiment is investigated. A symmetric capillary cell with two polymer coated glasses was used. An easy axis was induced by rubbing both surfaces in the same direction. The exciting Ar+ laser beam has the polarization direction perpendicular to the easy axis. The time dependent transmitted intensity of the probe He-Ne laser beam (polarized parallel to the easy axis) has been measured for various power of Ar+ laser in high-intensity regime and the beginning time of the ripple structure formation has been estimated. The spacing and the depth of the ripple structure were measured by using atomic force microscopy.

The permanent structure induced by an Ar+ linearly polarised laser beam on an asymmetric dye-doped nematic liquid crystal cell was investigated in a pump-probe experiment. The polarisation direction of the probe beam was parallel to the easy axis and two configurations of pump beam were used: polarisation directions perpendicular and parallel to the easy axis. The transmitted intensity of the probe beam was recorded during irradiation and it was observed that it depended both on the power and polarisation direction of the pump beam. We explained the evolution of the transmitted intensity and evaluated the start time of formation of the ripple structure. The induced permanent structure in the irradiated zones and the laser-induced surface morphology was studied using a polarising optical microscope and an atomic force microscope, respectively. The surface morphology in the irradiated zones was also dependent on both the power and polarisation of the Ar+ laser beam. The orientation of the microgrooves in the ripple structure was parallel to the polarisation direction of the pump laser beam in both configurations. For a given pump power, the depth of the ripple structure was greater in the case of an Ar+ beam polarised parallel to the easy axis. The induced azimuthal anchoring energy provided by the ripple structure was evaluated.