National Institute Of Materials Physics - Romania

In this work, a complementary ultraviolet-visible (UV-VIS) spectroscopy and photoluminescence (PL) study on melatonin (MEL) hydrolysis in the presence of alkaline aqueous solutions and the photodegradation of MEL is reported. The UV-VIS spectrum of MEL is characterized by an absorption band with a peak at 278 nm. This peak shifts to 272 nm simultaneously with an increase in the band absorbance at 329 nm in the presence of an NaOH solution. The isosbestic point localized at 308 nm indicates the generation of some chemical compounds in addition to MEL and NaOH. The MEL PL spectrum is characterized by a band at 365 nm. There is a gradual decrease in the MEL PL intensity as the alkaline solution concentration added at the drug solution is increased. In the case of the MEL samples interacting with an alkaline solution, a new photoluminescence excitation (PLE) band at 335 nm appears when the exposure time to UV light reaches 310 min. A down-shift in the MEL PLE band, from 321 to 311 nm, as a consequence of the presence of excipients, is also shown. These changes are explained in reference to the MEL hydrolytic products.

This work investigates the structural, magnetic and magneto-optical properties of a new zinc phosphate-tellurite glass belonging to the 45ZnO-10Al(2)O(3)-40P(2)O(5)-5TeO(2)system. The glass was prepared by a wet method of processing the starting reagents followed by suitable melting-stirring-quenching-annealing steps. Specific parameters such as density, average molecular mass, molar volume, oxygen packaging density, refractive index, molar refractivity, electronic polarizability, reflection loss, optical transmission, band gap and optical basicity have been reported together with thermal, magnetic and magneto-optical characteristics. Absorption bands appear in the blue and red visible region, while over 600 nm the glass becomes more transparent. FTIR and Raman spectra evidenced phosphate-tellurite vibration modes proving the P(2)O(5)and TeO(2)network forming role. Magnetic measurements reveal the diamagnetic character of the Te-doped glass with an additional weak ferromagnetic signal, specific to diluted ferromagnetic oxides. Positive Faraday rotation angle with monotonous decreasing value at increasing wavelength was evidenced from magneto-optical measurements. The final product is a composite material comprising of a non-crystalline vitreous phase and Te-based nanoclusters accompanied by oxygen vacancies. The metallic-like Te colloids are responsible for the dark reddish color of the glass whereas the accompanying oxygen vacancies might be responsible for the weak ferromagnetic signal persisting up to room temperature.

In this paper, we investigate the origin of point defects revealed by electron spin resonance (ESR) and photoluminescence (PL) emission in correlation with the photocatalytic activity of ZnO nanocrystals subjected to thermal annealing at various temperatures. Two ESR signals at g similar to 1.96 and similar to 2.003 were consistently observed in all annealed ZnO samples. However, their relative intensities have changed, indicating that the point defect densities were influenced by the annealing temperature. Interestingly, when doping nanoZnO with Cr3+, the Q-band ESR measurements at T = 100 K did show that the g similar to 1.96 signal was completely passivated, suggesting that the origin of the signal lies in the electrons located near the conduction band, i.e. at a shallow-donor level. The intensity of the g similar to 2.003 signal decreased by rising the annealing temperature, and this is attributed to the depopulation of zinc interstitials through the thermally induced migration process and/or recombination with the zinc vacancies. The green PL emission line at similar to 520 nm, which is dominant in the 700 degrees C annealed ZnO sample, shows a correlation with the ESR signal at g similar to 1.96, whose origin is attributed to the radiative transition of the electron from the shallow donor level to the singly ionized zinc vacancy. Furthermore, the high density of the shallow donor electron states was found to be primarily responsible for the high photocatalytic activity in the degradation of methylene blue.

This study addresses the deposition with improved adhesion of TiO2:N/SiO(2)mixture, with different concentrations of the nano-powders (NPs) (1:0,5; 1:1 and 1:1,5) on 100% cotton fabrics. The characteristics of the deposited thin films were investigated by scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS), Raman scattering, FTIR, and UV-VIS absorption spectroscopy. To improve the treatment durability to the external factors, the different crosslinking methods were used. Photocatalytic activity of functionalized textile fabrics was evaluated by determining the photodegradation efficiency of the methylene blue (MB) dye and forest juice, measuring the color difference of the irradiated samples compared with non-irradiated samples. Washing durability of the samples was achieved qualitatively by determining the photocatalytic activity remaining on the textile fabrics after 1 and 5 washing cycles. The samples treated with the mixture of TiO2:N/SiO(2)have demonstrated improved self-cleaning properties, the highest photocatalytic activity being obtained for the highest value of TiO2:N/SiO(2)NPs molar concentrations equal to 1:1.

Complexes with mixed ligands [Cu(N-N)(2)(pmtp)](ClO4)(2)((1) N-N: 2,2 '-bipyridine; (2) L: 1,10-phenanthroline and pmpt: 5-phenyl-7-methyl-1,2,4-triazolo[1,5-a]pyrimidine) were synthesized and structurally and biologically characterized. Compound (1) crystallizes into space groupPaand (2) inP-1. Both complexes display an intermediate stereochemistry between the two five-coordinated ones. The biological tests indicated that the two compounds exhibited superoxide scavenging capacity, intercalative DNA properties, and metallonuclease activity. Tests on various cell systems indicated that the two complexes neither interfere with the proliferation ofSaccharomyces cerevisiaeor BJ healthy skin cells, nor cause hemolysis in the active concentration range. Nevertheless, the compounds showed antibacterial potential, with complex (2) being significantly more active than complex (1) against all tested bacterial strains, both in planktonic and biofilm growth state. Both complexes exhibited a very good activity against B16 melanoma cells, with a higher specificity being displayed by compound (1). Taken together, the results indicate that complexes (1) and (2) have specific biological relevance, with potential for the development of antitumor or antimicrobial drugs.

The first electrochemical immunosensor for the determination of the 20S proteasome (P20S) was developed, entailing the immobilization of an antibody on an aminophenylboronic/poly-indole-6-carboxylic acid-modified electrode. The proposed electrochemical bioplatform is a simple and feasible analytical tool applicable for the determination of P20S in human plasma, considering its high clinical and biological relevance. Cyclic voltammetry, electrochemical impedance spectroscopy, and square wave voltammetry (SWV) were used to determine the optimal step-by-step process to obtain the electrochemical immunosensor. The interaction of P20S with the recognition layer of the immobilized antibody on the nanostructured surface took place by incubating the electrode in a P20S solution at 20 degrees C for 2 h. Using SWV as an electro-analytical technique, this immunosensor can quantify P20S. The current was linear with the P20S concentration within two dynamic concentration ranges from 20.0 to 80.0 and 80.0 to 200.0 ng.mL(-1) (r(2) = 0.992 and 0.98, respectively) with a limit of detection and quantification of 6 and 18 ng.mL(-1), respectively. Moreover, the immunosensor showed considerable repeatability and reproducibility, when the determination was done in human serum, which confirms that it is a promising alternative for direct detection of P20S in biological fluids with minimal interference.

Polyvinylidene fluoride-iron oxide (PVDF-Fe2O3) nanocomposites have been obtained my melt mixing of PVDF with Fe2O3 nanoparticles. The interactions between the polymeric matrix and the nanofiller have been investigated by wide angle X-ray scattering (WAXS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, using both red and green excitations (lasers). WAXS, FTIR, and Raman spectra confirm that all samples contain alpha PVDF as the major crystalline form of the polymeric matrix. Experimental data revealed small changes in the positions of X-ray lines as well as modifications of the width of X-ray lines upon loading by Fe2O3 nanoparticles. FTIR and Raman spectra are dominated by the lines of the polymeric matrix. Within the experimental errors, the positions of Raman lines are not affected by the wavelength of the incoming electromagnetic radiation, although they are sensitive to the strain of the polymeric matrix induced by addition of the nanofiller. The loading of the polymeric matrix with nanoparticles stretches the macromolecular chains, affecting their vibrational spectra (FTIR and Raman). A complex dependence of the positions of some Raman and FTIR lines on the loading with Fe2O3 is reported. The manuscript provides a detailed analysis of the effects of nanofiller on the position of WAXS, FTIR, and Raman lines. (c) 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48907.

Graphene-based photocatalytic layers were prepared by reactive matrix assisted pulsed laser evaporation technique. Binary, nitrogen doped reduced graphene oxide (RGO)/TiO2 and ternary RGO/TiO2/graphitic carbon nitride (g-C3N4) compounds were synthesized and simultaneously deposited onto solid substrates. Aqueous dispersions of commercial graphene oxide platelets and TiO2 nanoparticles were prepared. NH3 or melamine powder was added to the dispersions to achieve enhanced nitrogen doping and synthesis of g-C3N4 during laser irradiation. The photocatalytic efficiency of the layers towards degradation of antibiotic, chloramphenicol and organic dye molecules was systematically investigated and correlated with structural, compositional, and morphological features. This study provides new insights into the importance of TiO2 crystal facets and the synergistic effects between TiO2 nanocrystals and the other constituents, nitrogen doped RGO and g-C3N4 of the hybrid layers. As a result of combined effect of constituent materials, TiO2, RGO, and g-C3N4 as well as N doping of RGO, through the generation of quaternary and pyrrolic N functionalities, the composite layers showed high photocatalytic efficiency for degradation of organic molecules. Stability and reusability experiments indicated that the composite layers maintain their high photodegradation efficiency towards organic molecules during consecutive degradation cycles. Active radical scavenging experiments were also carried out in order to determine the role of the main active species involved in the photocatalytic degradation process.

This paper outlines a method of extraction of iron from water in the form of iron oxyhydroxide natural nanoclusters at comparatively low concentrations and varied ranges of pH using zinc acetate salt. The zinc acetate salt dissociates into Zn(2+)and acetate ions in water where Zn(2+)interacts with iron clusters present in a solution of a given iron concentration and pH, while the acetate ion helps in charge-neutralization based coagulation and consequent precipitation of such nanoclusters. The Zn(2+)ions may also lead to the growth of layered zinc hydroxide (LZH) nanosurfaces at pH >= 6 at sufficient loading. The advantage of this method is the active chemical interaction of Zn(2+)with Fe clusters, followed by growth, which ensures that only some added Zn ions remain in the water while the rest precipitate out along with the residual iron oxyhydroxide, especially at higher pH. The solid that precipitated under various different conditions was successfully evaluated by XRD (formation of ferrihydrite-like nanoclusters (n-Fh)), FTIR (the presence of acetate in the solid n-Fh), TEM (the presence of zinc at higher pH), and EXAFS (local structural characterization). ICP analysis of the obtained solid and the corresponding filtrate revealed the removal efficiency of iron and zinc from the solution at various initial concentrations and pH values. This method of extracting soluble Fh-like nanoclusters by charge neutralization appears to be a suitable promising tool for water purification, because ferrihydrite is capable of isolating other adsorbed contaminants from water, along with itself.