The centrifugal spinning of vitamin doped natural gum fibers for skin regeneration.

The study investigates the use of fiber carriers, based on biopolymeric gums as potential candidates for cosmetic and dermatological applications, in particular for skin regeneration. Gum arabic (GA), xanthan gum (XA), and gum karaya (GK) were used as the main gum materials for the fibers, which were prepared by centrifugal spinning from an aqueous solution. These solutions of different mass gum ratios were blended with poly (ethylene oxide) (PEO) for better spinnability. Finally, vitamins E and C were added to selected solutions of gums. The resulting fibers were extensively investigated. The morphology and structure of all fibers were investigated by scanning electron microscopy and Fourier transformed infrared spectroscopy. Most importantly, they were characterized by the release of vitamin E loaded in the fibers using UV-VIS spectroscopy. The presentation will show that the newly prepared fibers from GA and PEO represent a very promising material for cosmetic and dermatologic applications.

Highly Efficient and Controllable Methodology of the Cd0.25Zn0.75Se/ZnS Core/Shell Quantum Dots Synthesis.

The surface of any binary or multi-component nanocrystal has imperfections and defects. The number of surface defects depends both on the nature of the nanomaterial and on the method of its preparation. One of the possibilities to confine the number of surface defects is the epitaxial growth of the shell, which leads to a change in the physical properties while maintaining the morphology of the core. To form a shell of the desired thickness, an accurate calculation of the amount of its precursors is substantial to avoid the appearance of individual crystals consisting of the shell material. This study aimed to develop an effective calculation method for the theoretical amount of precursors required for the formation of a ZnS shell on the surface of a Cd0.25Zn0.75Se core, followed by the practical implementation of theoretical calculations and characterization of the prepared nanomaterials. This method allows the complete control of the masses and volumes of the initial reagents, which will in turn prevent undesirable nucleation of nuclei consisting of the shell material. In the synthesis of Cd0.25Zn0.75Se/ZnS core/shell quantum dots (QDs), the sources of chalcogens were substituted seleno- and thioureas, which are capable of not only supplanting modern toxic sources of sulfur and selenium but also allowing one to perform the controlled synthesis of highly photoluminescent QDs with a low number of surface defects. The result of this shell overcoating method was an impetuous augmentation in the photoluminescence quantum yield (PL QY up to 83%), uniformity in size and shape, and a high yield of nanomaterials. The developed synthetic technique of core/shell QDs provides a controlled growth of the shell on the core surface, which makes it possible to transfer this method to an industrial scale.

Laser Desorption Ionization Time-of-Flight Mass Spectrometry of Silver-Doped (GeS2)50(Sb2S3)50 Chalcogenide Glasses.

Mass spectra of (GeS2)50(Sb2S3)50 glass and Ag-doped glasses [5% Ag (GeS2)50(Sb2S3)50 and 15% Ag (GeS2)50(Sb2S3)50] obtained using laser desorption ionization (LDI) time-of-flight coupled with quadrupole ion trap mass spectrometry were studied. The analysis of the mass spectra indicated the formation of Ag a Ge b Sb c S d clusters. In addition to the SbS d + (d = 1 and 2), Sb2S d + (d = 1-3), Sb3S d + (d = 1-5), Sb4S d + (d = 3 and 4), Sb5S2 +, and Sb c + (c = 3 and 5) clusters, various clusters containing Ag, such as Ag a + (a = 1 and 2), AgGeS+, AgSb c + (c = 1, 2, and 4), AgSbS+, AgSb2S d + (d = 1-5), AgSb3S3 +, AgSb4S4 +, Ag2Sb3S d + (d = 4 and 5), Ag4Sb2S3 +, and Ag5SbS3 +, were generated. Moreover, in spite of the five-ninth purity of all glass components, several hydrogenated clusters (SbS3H8 +, Sb4S2H+, Ag2H11 +, Ag2Sb3H4 +, Ag3Sb2H4 +, Ag4Sb2H2 +, and Ag4S3H8 +) and some low-intensity oxidized clusters, such as Sb3O+ and Sb3O5 +, were also detected. When applying LDI on (GeS2)50(Sb2S3)50 glass, no Ge-containing clusters were detected in the positive ion mode, and just one Ge-containing cluster was observed after doping the glass with Ag. Hydrogen plays an important role in the glasses studied. The knowledge gained concerning cluster stoichiometry contributes to the elucidation of the structure of Ag-doped Ge-Sb-S chalcogenide glasses. It should be noted that some of the clusters were considered to be structural fragments. Furthermore, mass spectrometry was complemented with Raman spectroscopy.

In-situ measurement of reversible photodarkening in ion-conducting chalcohalide glass.

We report the kinetics of below band-gap light induced photodarkening in (80-x)GeS(2)-20Ga(2)S(3)-xAgI (x = 0 and 20 mol %) bulk chalcogenide glasses by measuring the time evolution of transmission spectra at every 10 milliseconds. The results prove clearly the enhancement of photosensivity upon doping of AgI compound in glasses. It is interesting to find that PD observed in AgI-doped glass totally disappears two hours later after the laser exposing even at room temperature. In significant contrast to 80GeS(2)-20Ga(2)S(3) glass that the metastable part of PD remains for a long time. We expect such a fast auto-recovery property in AgI-doped glass can be utilized for optical signal processing.