Tamara S. Minakova

Synthesis and surface characterization of nanosized Y2O3:Eu and YAG:Eu luminescent phosphors which are useful in photodynamic therapy of cancer

Abstract A series of finely dispersed Y2O3:Eu and YAG:Eu phosphors useful for the enhancement of photodynamic therapy (PDT) of cancer were prepared using the Pechini method and self-propagating high temperature synthesis (SHS). The obtained phosphors can be used in cancer therapy drugs in combination with a photosensitizer which accumulates selectively in tumor tissues. Upon excitation with X-ray irradiation which easily penetrates the organism such phosphors are activated to radiate the visible light with wavelengths required to stimulate the photosensitizer yielding active singlet oxygen which destroys cancer cells. Thus the developed phosphors provide an extension of PDT in the treatment of internal tumors which are inaccessible for activating light from the outside. A detailed characterization of the obtained phosphors was performed to define various types of adsorption centers and the functional groups on their surface, including hydroxyls with different acid-base characteristics and an admixture hydrated carbonate layer which may help in linking with other drugs (photosensitizer and pluronic binder) and is important in respect of biocompatibility. A model describing the composition of acid-base centers with various pKa values on the surface of the studied materials is suggested on the basis of the obtained results as an approach to study the adjustable modification of various compounds in respect of the compatibility between their ingredients as well as their overall biocompatibility. Y2O3:Eu phosphor prepared via the SHS method was successfully tested for biological (therapeutic) activity which provided an effective destruction of fibroblast cell cultures of Chinese hamster V-79 in combination with a photosensitizer upon X-ray irradiation.

The Influence of Zn3(PO4)2:Mn - Luminophores Synthesis Conditions on their Surface and Luminescent Features

A technology, that allows production effective x-ray luminescent phosphors Zn3(PO4)2:Mn2+ with nanosized particles from the water solution by sol-gel method, and directional regulated their luminescence color from green to red was developed. X-ray intensity and spectra, phase structure, and surface properties of synthesized samples depending on the synthesis conditions was studied. The conditions of synthesis which allow to obtain the samples according to the demands for the luminophores of medical assignment were determined.

Luminescent Materials on the Basis of Yttrium Oxide and Yttrium Aluminum Garnet Used for Photodynamic Therapy

Finely-dispersed phosphors of Y2O3:Eu and Y3Al5O12:Eu have been synthesized with the help of Pechini method and the method of self-propagating high-temperature synthesis (SHS). During the synthesis of phosphors on the basis of Y2O3 carried out with Pechini method the size of crystallites increases with the enlargement of concentration of yttrium, but it decreases when the method of SHS is applied. The structure of phosphors on the basis of Y3Al5O12 (YAG) is strongly amorphized. This fact agrees with the data of XRD and with the prevalence of the band with λmax = 613 nm in the spectra of this phosphor. The enlargement of yttrium concentration in it promotes the amorphisation of yttrium aluminum garnet and the decrease of a crystal phase content. The sample of Y3Al5O12:Eu synthesized with Pechini method has the maximum intensity, while in conditions of excitement with “high-level” X-ray radiation which corresponds to the radiation of industrial medical X-ray apparatus, the phosphor of Y2O3:Eu synthesized with the help of SHS showed the largest intensity. Colloid solutions prepared with the use of the samples synthesized by SHS method revealed a higher steadiness and a lower disposition to the sedimentation process. The samples of Y2O3:Eu phosphor possessing the smallest size of particles and the highest intensity of X-ray luminescence are the most suitable for the creation of pharmacological drugs used for photodynamic therapy.

Adsorption-desorption of water vapor on initial and modified peat samples

Specific features of adsorption-desorption of water vapor on the initial samples of valley-bog and raised-bog peat and on the samples modified with iron and aluminum salts were studied and interpreted in terms of the model of a process with two types of sorption sites.

Influence of the Composition, Structure, and Physical and Chemical Properties of Aluminium-Oxide-Based Sorbents on Water Adsorption Ability

Interaction between the water adsorption ability of aluminium-oxide-based sorbents and their chemical composition, acid-base properties of the surface, and textural characteristics has been analysed. Alumina desiccants were synthesized with the centrifugal–thermal activation of gibbsite followed by the hydration of the gibbsite under mild conditions. It was demonstrated that the multicyclic adsorption regeneration of samples under realistic conditions results in structural transformations and changes in the acidity of their surfaces and water adsorption ability. The modification of pseudoboehmite with alkali ions increases surface basicity and the dynamic capacity of adsorbents relating to water vapours. Equations have been presented that describe the adsorption and desorption processes taking place during water vapour adsorption with the materials studied.

Investigation of acid-base and sorption properties of surface of metal–ceramic composites

The acid-base properties of the surface of composites based on boron, silicon, and sialon nitrides were investigated by the indicator method of Hammett and Tanabe with spectrophotometric indication. Identification of the surface sites of the composites under study was carried out. On the surface of composites based on boron and sialon nitrides the Lewis base sites dominate, while on the surface of samples based on silicon nitride the Brønsted acid sites. Sorption of dyes and oxalic acid by cermet materials was studied. It is shown that the adsorption activity depends on the nature and amount of surface active sites of the composites.

Phisicochemistry of alkaline-earth metals oxides surface

The surface state of alkaline-earth metals and magnesium oxides obtained by means of commercial and laboratory ways has been studied in this paper. A complex of methods has been used for identification, determination of a phase composition and morphology of the samples. The high basic character of surface centres has been shown with the help of pH-metry and adsorption of indicators methods. Acid-basic parameters (pHt, pHiis, etc.) can be used for the estimation of a general acid-basic state of metal oxides samples surface and for the supposition about different nature and strength of acid-basic centres as well as for the initial control in the process of acid basic properties of solid oxides surface properties evaluation.

Effect of technique of applying layers of metal acetylacetonates on acid-base and chromatographic properties of sorbents

A series of chromatographic sorbents, which differ by way of applying modifying chelates of acetylacetone was obtained. The acid-base and chromatographic properties of sorbents with thermally and chemically grafted layers of metal acetylacetonates were investigated. It was shown that the modifi cation of the mineral sorbents with metal acetylacetonates leads to a change in the surface acidity, as well as to an increase in the polarity and selectivity with respect to different classes of compounds.

Effect of plasmochemical modification on electro-optical and surface properties of zinc sulfide electroluminescent phosphors

Method for improving the brightness of photo- and electroluminescence from ZnS:Cu and ZnS:Cu, Al phosphors by their treatment in a low-temperature gas-discharge plasma was developed. The relationship between the luminescence brightness and spectra and surface properties of the phosphors was studied. The mechanism of processes that occur on the surface and in the bulk of phosphor particles during their bombardment with plasma ions was determined.