Structural and Luminescence Properties of Silica-Based Hybrids Containing New Silylated-Diketonato Europium(III) Complex

A new betadiketonate ligand displaying a trimethoxysilyl group as grafting function and a diketone moiety as complexing site (TTA-Si = 4,4,4-trifluoro-2-(3-trimethoxysilyl)propyl)-1-3-butanedione (C4H3S)COCH[(CH2)3Si(OCH3)3]COCF3) and its highly luminescent europium(III) complex [Eu(TTA-Si)3] have been synthesized and fully characterized. Luminescent silica-based hybrids have been prepared as well with this new complex grafted on the surface of dense silica nanoparticles (28 (+/-3 nm) or on mesoporous silica particles. The covalent bonding of Eu(TTA-Si)3 inside the core of uniform silica nanoparticles (40 (+/- 5 nm) was also achieved. Luminescence properties are discussed in relation to the europium chemical environment involved in each of the three hybrids. The general methodology proposed allowed high grafting ratios and overcame chelate release and tendency to agglomeration, and it could be applied to any silica matrix (in the core or at the surface, nanosized or not, dense or mesoporous) and therefore numerous applications such as luminescent markers and luminophors could be foreseen

A comparative study of non-covalent encapsulation methods for organic dyes into silica nanoparticles

Numerous luminophores may be encapsulated into silica nanoparticles (< 100 nm) using the reverse microemulsion process. Nevertheless, the behaviour and effect of such luminescent molecules appear to have been much less studied and may possibly prevent the encapsulation process from occurring. Such nanospheres represent attractive nanoplatforms for the development of biotargeted biocompatible luminescent tracers. Physical and chemical properties of the encapsulated molecules may be affected by the nanomatrix. This study examines the synthesis of different types of dispersed silica nanoparticles, the ability of the selected luminophores towards incorporation into the silica matrix of those nanoobjects as well as the photophysical properties of the produced dye-doped silica nanoparticles. The nanoparticles present mean diameters between 40 and 60 nm as shown by TEM analysis. Mainly, the photophysical characteristics of the dyes are retained upon their encapsulation into the silica matrix, leading to fluorescent silica nanoparticles. This feature article surveys recent research progress on the fabrication strategies of these dye-doped silica nanoparticles

Thyroid scanning in diagnosis of toxic nodular goiter

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Peak-effect, a new phenomenon observed at microwave frequencies in high Tc superconductor thin films

Measurements of microwave surface resistance in magnetic fields (parallel to c-axis), ranging between 0.2 and 0.9 T, of high quality epitaxial DyBa2Cu3O7-y and YBa2Cu3O7-y superconducting thin films show a pronounced peak near the superconducting transition temperature. It is more pronounced at a frequency of 9.55 GHz as compared to 4.88 GHz. The exact nature of the peak is somewhat sample-dependent thereby indicating that the nature and distribution of defects in the films or the pinning sites determine the nature of the peaks; however, it follows the general trend that as the magnetic field is increased the peak shifts towards the lower temperature and is absent when the field is zero. The temperature and field dependence of the peak suggests that this peak could be associated with the order–disorder transition of the flux-line lattice. The peak-effect shows strong frequency dependence close to the depinning frequency of the flux line lattice. We explain our data in terms of the temperature dependence of the Labusch parameter within the collective pinning scenario in type II superconductors.

In-silico analysis of bufadienolides as potential inhibitors of Trypanosoma nucleoside hydrolase

Trypanosomiasis is one of the neglected tropical diseases which curtails the productivity of the victim and causes mortality in extreme cases. Non-availability of vaccines, low therapeutic index of trypanocidal drugs and development of resistance lead to the need for research focused on developing alternative treatment options against this disease. The aim of the current work is to use computer-assisted drug discovery techniques to examine the anti-trypanosomal action of bufadienolides, which are commonly detected in the skin secretions of toads. A library of 16 compounds from the bufadienolides family was tested for toxicity and docked against the Trypanosoma brucei hydrolase. The oral bioavailability and good suitability of the compounds for transdermal delivery was also indicated by the ADMET study. The findings based on molecular docking and dynamics simulation along with toxicity assessment showed that three compounds, marinobufagin, resibufogenin and resibufaginol, have the lowest toxicity and maximum binding energy against Trypanosoma brucei hydrolase. According to the results obtained by molecular docking interactions between drugs and target proteins are observed and contain a number of hydrogen bonds near the residues in the active pocket of the enzyme. The results of this study contribute to the understanding of the SAR of bufadienolides and provide a foundation for further research and drug development efforts. The computational analysis, including the density functional theory study, the knowledge of inhibitory mechanisms and aids in the design and optimization of novel anti-trypanosomal drugs